| Author | Message | ||
     Steve Brabin New member Username: steve_b Post Number: 42 Registered: 09-2002 Posted From: 62.7.50.147 |
The previous discussion on the ante-chamber and a plausible practical method of design was, as usual for the board, informative and helpful for anyone studying this monument. The photographs alone are invaluable contributions to anyone who has not seen the pyramid first hand, and the general theory put together by Samuel a logical application of engineering practice to a problem that clearly presents itself for this type of work. My engineering expertise is not sufficient to pass professional judgement on the ideas, but they are obviously clearly thought out, and if they took even twice as long to write as hey did to read, then the effort put into the conceptual design was considerable! I for one am more than happy to accept Samuel's hypothesis as a highly logical possibility and a more than plausible solution to the engineering workings of the antechamber. But aren't we missing the point somewhat in the overall work??? Without trying to draw Samuel's proposal in detail, the following two diagrams sum up the antechamber as we have it today, and how it should have looked just after completion.   The problems that I can see in this scenario are clearer to me now than they were before the detailed discussion on the engineering of the antechamber took place. 1) The antechamber offers no protection whatsoever against robbers as the closure stones can be accessed from above an all cases. 2) The first of the stones (and the one which is still in place today) serves no purpose whatsoever, and in fact when viewed in isolation from the rest of the proposed system, this stone is still quite clearly in its 'down' position. 3) The final assembly provides perfect protection from anyone trying to enter the grand gallery from the main chamber, but not the other way around !!! Or to summarise the whole of the chamber, something is not quite right. The hollows on the top of the granite leaf, the obvious implication that there should have been sliding stones in place at some time in the past, the fact that there is a stone in place which serves no practical purpose all get ones mind thinking. In fact, is that not the purpose of the antechamber ? The portcullis stone that is in position today, if it serves no practical purpose, can therefore only be serving a symbolic purpose, and that surely is to show anyone looking at it how the sliding stone mechanism works. The grooves in the walls show where the sliding portcullises should be placed. And the perfectly sealed passage from the main chamber (were the portcullises actual there) shows that if the builders of this monument had wanted to seal off the main chamber from the grand gallery approach, we should be under no illusions whatsoever that they could and would have done so. (Imagine trying to get into the antechamber from the main chamber with the portcullises down.Push? Pull? Slide? Drill? You wouldn't know where to start) Samuel's hypothesis is , as far as I can see, exactly what the antechamber is about. Do we not now have all the information that we could require for entering into a sealed Ancient Egyptian monument's main chamber should we ever come across one in the future, as we have clear indications of the precise closure mechanism that was used ? The following diagram shows an old Egyptian lock mechanism,  and was taken from the web page http://www.chass.utoronto.ca/~maryjmeg/history.html As can be seen from the diagram, and gleaned from the text and links on the page, tumbler and pin style locks were present in Ancient Egypt around the supposed time of the pyramids construction and were always placed on the INSIDE of the door in question for pretty obvious reasons. To suggest that the locking mechanism of the greatest monument ever built had is locking mechanism on the outside and also a mechanism which was so seriously flawed in its design surely gives very little credit to the architects, and not too much to our own capacity to think in past even the elementary concepts in what we are looking at . Is the ante chamber not just a lock pickers' instruction manual, the content of which has just so elloquently been explained to us by Samuel? Best Regards Steve Brabin | ||
| J.D. Degreef Senior Member Username: jd_degreef Post Number: 452 Registered: 02-2000 Posted From: 213.177.158.90 |
Dear Mel, On the S wall grooves, stopping them before the KC passage indeed provided for a better seal. A thick portcullis leaving four 9 cm holes in the wall near its top may not have been felt to be satisfactory indeed. Also, if the suspension holes had been lower in the portcullises, once they had been lowered one would have been able to peek through (maybe not as far as the KC, if the crawling passage was plugged). The idea that the plugs were to keep something / somebody in the KC rather than preventing people to enter it is interesting, and possible. Anthropologists would certainly find many parallels (they usually do  ), and fear of the dead wasn't unknown in Egypt. It has been invoked to explain the mutilations of the 4th dyn. "reserve heads". Well, I don't know. I'm indeed not satisfied by the model which seems indicated by the majority of material clues at our disposal : that the portcullises were closed all at once, and without much braking. Samuel's model may appear more satisfactory from the mechanical point of view, but it certainly accounts for much less construction details than the one I presented. As a side note, the construction details also forced me to abandon most of my own darling ideas... Maybe the distance between the leaf and the N wall wasn't that important, if the space above the portcullises was almost filled with architectural elements. For example the beams are generally considered to have been made of wood, but what about granite ones, with a second level of beams above them, just leaving narrow spaces for the ropes ? After closure, this would leave a narrow window above the leaf, allowing one to peek into the space where the suspended portcullises had been. And the northern space could itself have been plugged. The difference between the tops of the E & W wainscots is the most intriguing aspect of the chamber indeed. Dear Samuel, I'm relieved that you didn't spot major engineering flaws in my posting, as this isn't really my domain... Just a few reactions to your reply : -on removing the struts supporting the portcullises : I have tried to present a model based on as many construction features as possible (not all : at the present point, the differences between the upper wainscot surfaces cannot be reconciled...). From this point of view, the sharp rim of the crawling passage's ceiling where it meets the portcullises' chamber north wall indicates that no cables under a lot of tension would have descended from the leaf stone area, turned around the sharp rim and gone towards the Grand Gallery. Especially since the rim could have been crafted differently, in the classical shape of an Egyptian doorway. See pic of exit of Menkaure's portcullises chamber into what plays the role of the GG in his pyramid, IMHO :  So if one lets the construction details talk, your idea about lifting the slabs to remove the struts, then smoothly lowering them one by one, isn't what the details say, even though it may be satisfactory from other viewpoints. Besides, from the measurements I calculated, the portcullises occupied the whole space between the beams and the level of the passages, so they couldn't be lifted more, as they already touched the beams. Agreed, the measurements are approximate, being partly based on a photograph not entirely perpendicular to the object being measured. But IMHO : no lifting, no pulling away the struts (and sawing their bases off is another complication which makes your model still less probable). So is the constant rewiring of the portcullises, through holes that lie more than an arm's length from the "empty" space above ! Not impossible, but rather impractical. Placing the ropes when building the chamber would have been easier, and I don't see what would have weakened them with the years : not moisture, not ultraviolet light, no wear and tear (with the portcullises resting on their struts and the jaws of the leaf stones in open position). Nor do I believe in your wooden construction at the top of the GG. From the traces in this passage, from its structure and from the homologous chamber in Menkaure's pyramid, I deem it more probable that the walls were covered with wooden panels with a false door motive, the doors of which may also have served to cleverly hold the structures maintaining the AP plugs in position. -on the way you reconstructed the suspension of the portcullises, this would have caused rubbing, which could easily have been avoided by a slightly different design. I can't believe that the slides would have been designed that way, with the descending portcullises rubbing against the north lip of the slides. Of course even without lubricant this wouldn't have prevented the system from closing, but it isn't neat, that's all. In the case of the leaf stone, firstly, the mechanism with the boss may derive from a second thought (original plan = lifting suspended upper leaf from above ???) ; secondly, it only involved a short sliding movement, maybe only a centimeter, not at all the same thing as a massive portcullis shearing against its slide during its violent descent. Again, I let the slide design talk, and what it tells us is that the suspension wasn't as you think it is. I'm not sure it was as I presented it either, since this involves lost beams and wall structures under the chamber's roof. But at least the existence of lost elements is certain ! The rough working of the roof could also point to its being hidden by other technical structures. -on the upper wainscot surfaces : >In my opinion, if the beams rotate or not, is not important.< All important, at the contrary, from the point of view of static friction, possibly holding the portcullises up while the supporting struts were being removed ! You still don't provide a rationale for narrowed cylindrical ends on the east side ! >JD: A third possibility is that the eastern end of the beam was cut into a rectangle, with one short side resting on the wainscot. Samuel: This would be the same as cutting the lower end straight, as shown by Pochan.< Except here the beam isn't weakened as much ! And it explains 1. the flat upper surface of the wainscot 2. the level at which it lies. -on the "leaf": >JD: "but is displaced towards the west, may show that the upper rim was already as oblique as it is now (in other words, that it has not simply be damaged after the pyramid was looted) : the displacement may have been intended to bring the boss underneath the slab's center of gravity, where it should be ! Samuel: Could the workers calculate the center of gravity of such an irregular slab, as have been mentioned?< Calculate, probably not, but determine it by placing the slab on a small square beam and finding the position where it didn't tip over to either side, yes ! >What will happen if the wooden level machine [to lever the leaf upwards] is only 1 inch in thickness and 5 inches in length? I leave this to you.< You're the engineer : are you saying the wood wouldn't hold the 900 kg compression ? >JD : b. the dent at the center of the southern lower rim of the upper slab c. the small cupular depression near the upper rim of the lower leaf stone, Samuel: ...they could only have been used, as I proposed; for controlling the slab movements at the moment of introducing the slab in the side wainscot grooves. As a matter of fact, in my proposal I suggested its use as a controlling rope line, they are not needed for supporting the slab weight.< No need to control the descent of such a "light" slab, other than with the ropes with which it's being descended, no ? -On the plugging of the crawling passages : > Setting these plugs in position is nothing compared with the 43 stone beams in the 5 ceilings of the King's Chamber< Yes, but when placing these giant blocks, the whole working platform of the pyramid stump could be used, plus the rooms may have been built in shafts left in the core, so that the huge beams would have been descended into position on a ramp, with the help of gravity. Whereas here the situation is comparatively more difficult : -one is working against the slope of the GG, i.e. upslope. -one is hampered by the presence of the high "step" at its end. -one is working in a confined space, without much room for a ramp and for the pullers themselves. -one has to do high precision work : pushing a very heavy plug into a passage not much wider than the block ! I don't understand your explanations on helping devices, especially if placed in the portcullises chamber (where ? the portcullises were lowered at this stage). Indeed a healthy exercise in logic, these discussions on the GP's portcullises chamber ! Hi Steve, Your diagrams are wrong : 1. the upper surface of the leaf stone isn't only rounded, but irregular and sloping down towards the east. 2. the upper parts of the portcullises are not rounded, but perfectly square, with four suspension holes astonishingly near the rim. 3. the leaf stones are thinner than the portcullises and don't feature their perforations. 4. the leaf stones comprise two parts, the portcullises one (contrary to your drawing). 5. the portcullises had suspension beams, the leaf stone none that we have remains of. In any case none in the location where those of the portcullises were. I'm not splitting hairs, but your diagrams seem to convey the impression that the leaf stone is some kind of equivalent or model of the portcullises, which it certainly isn't ! The door lock in your posting seems to be New Kingdom, 1000-1500 years after the GP. >Is the ante chamber not just a lock pickers' instruction manual< Or rather a stage in the development of portcullis mechanisms ? -until Snefru's reign, portcullises were usually lowered inside a shaft of their own, intersecting the underground passage to be blocked.  -the mass of a pyramid was such that one couldn't build a shaft between its surface and the passages underneath it, so the architects had a problem there. At the Bent Pyramid, they designed incredible portcullises sliding on an incline, perpendicular to the passage. The Red Pyramid seems to have been plugged by letting one or more blocks slide down the whole DP, at the bottom of which is a prismatic cavity apparently destined to receive the block. The same structure can be found at the lower end of the GP's DP. But there seems to have been a theological need for portcullises, playing the role of the "doors of the sky". At Meidum, there was an actual wooden door in the DP. I don't know about the plugging there. -all later Old Kingdom pyramids have portcullises at their exits, sliding vertically down. The ones in the chamber we're discussing are the oldest of these. As I just wrote, the DP at the Red Pyramid was plugged letting blocks slide down the DP (each of which had to be introduced separately through the entrance). In the case of the GP's AP, this was impossible, of course, so another plugging mechanism was designed, involving the GG. Here a whole train of blocks (at least three, probably more, possibly even enough to fill the whole AP) would automatically descend into the AP from the GG, once it had been released. This idea of an automatic closure system may have influenced the design of the portcullises chamber also : a few men with a lever, lifting a block by, say, 1 cm, would cause the portcullises to cra... uh ... close. -the probable portcullis(es) in Djedefre's pyramid are lost. -at Khafre's, the classical type appears : the portcullis is stored in a cavity in the passage's roof. Its descent is prevented by blocking its slides in the passage's side walls. How such a portcullis was descended I don't know. I suppose using levers. Or by knocking individual stones out of the slides, which they had blocked ? JD | ||
| Steve Brabin New member Username: steve_b Post Number: 43 Registered: 09-2002 Posted From: 213.123.74.242 |
JD, I take your points about the drawings, but they are not intended to be an accurate representation of the chamber - just a schematic. With all the details that you suggest, and which were discussed at length in the previous posting, amended on the drawings the overall picture is still the same. The antechamber is a perfect locking mechanism to prevent anyone getting OUT of the main chamber and a quite inept attempt to prevent anyone getting IN. The diagram of the lock was simply to illustrate the point - locks go on the inside of doors and not on the outside. The reason being that once you can see the method of the locking mechanism, it is considerably easier to open. So, is there any reason that anyone can put forward as to why the antechamber appears to have been constructed in reverse? And also does what I am suggesting make sense? Steve Brabin | ||
| Samuel Laboy Member Username: samuellaboy Post Number: 71 Registered: 09-2002 Posted From: 209.91.200.150 |
Hi JD, I am sorry; I did not check your engineering calculations. But it called my attention your insistence in using the level system and the boss to lift the whole weight of the granite slab. It is not a matter if the wood wouldn't hold the 900 kg in compression or not, that is not the case. As you said, I am the engineer, no? When the lifting operation with the level starts, the compression of the wood is not the governing factor. Please refer to your last diagram about this. Since the level is inclined, the wood piece will receive a shearing force (cutting effect), very heavy, with the tendency to break the side of the pushing end of your wooden level. This shearing force component could split out the corner of the level, before the full compression is obtained. In other words, where you put a vertical component to hold the slab, the reaction component in the wood is not of compression as you think, is shear stress component, tending to shear-out or strip the corner of the wood. This shearing stress component has to be overcome, before you think in the final compression stress for the wood. Besides, the resistance to shearing forces of the wood, in the same direction of the grains, is very, very weak. This is why in four different occasions I have given you my opinion about that type of level system and why it does not work in this case. I thought that your engineer advisors, or from your readings, you would find out, that is why I said " I leave it to you", excuse me if you thought in other way. I have a great respect and esteem for you to do otherwise. Going further on your design, the force passing through the piece of wood will be the weight of the stone (vertical component) and the normal force to the stone (horizontal component). Assuming that the surface of the wood is flush with the bottom of the boss, no matter how big the piece of wood you use, the force will be applied only through the area of the bottom of the boss. Now, if the piece of wood had exactly the area and geometry of the bottom of the boss, then the load could be assumed to be evenly distributed along the area. But, since this sectional area is about 5 square inches, there would be certain buckling of the wood before getting anywhere NEAR lifting the stone. Now, what happens when you use a piece of wood with a larger sectional area? The load is still being transferred by the area of the boss to the wood. That means that around the boss, the piece of wood must match the load that is being transferred. This creates a local shearing reaction. Using principles of statics, the stresses around the boss must be approximately equal to the uniform distributed load. Assuming a weight for the stone of 1,700 pounds, this load equals 340 pounds per square inch. Wood COULD takes this load- in compression. But this is SHEARING stress. Moreover, it would be shearing stress very much in the weak shear plane of the wood piece- along the fibers. The highest number for allowable stress in compression I have found for wood is 1,875 psi (pine), and its corresponding allowable shear stress 220 psi- much less than that required to lift the stone. And that is without taking in consideration stress concentrations around the boss. Please refer to an advanced structural mechanics book for explanations on stress concentrations. JD, we have reached the time when everything is being recycled. And as you continually say (IMHO), it means that I am dealing with your HO, not with facts. There is no way I am going to change your opinion. In the other side, I also have MHO. Therefore, we have to stop going over the same arguments, or speculations, based on opinions. If your opinion is that my system does not work, that's OK to me. There is nothing I can do about it. For example you wrote: 1. " IMHO: So if one lets the construction details talk, your idea about lifting the slabs to remove the struts, then smoothly lowering them one by one, isn't what the details say, even though it may be satisfactory from other viewpoints. 2. IMHO : no lifting, no pulling away the struts (and sawing their bases off is another complication which makes your model still less probable). So is the constant rewiring of the portcullises, through holes that lie more than an arm's length from the "empty" space above! Not impossible, but rather impractical. 3. Nor do I believe in your wooden construction at the top of the GG. -on the way you reconstructed the suspension of the portcullises, this would have caused rubbing, which could easily have been avoided by a slightly different design. I can't believe that the slides would have been designed that way, 4. Again, I let the slide design talk, and what it tells us is that the suspension wasn't as you think it is. I'm not sure it was as I presented it either, since this involves lost beams and wall structures under the chamber's roof. I don't understand your explanations on helping devices, especially if placed in the portcullises chamber (where ? the portcullises were lowered at this stage). " You see what I meant, its opinion against opinions, no facts. The exchange of opinions is OK, but they are only opinions, acceptable from any side. For example, in spite of your additional comments, much of them already discussed, I have not changed my mind in relation to the basic idea of my proposal, the same as you. However, if you were the owner of a project to build the antechamber, I would gladly submit my bid to take the project. I am sure I will do an exact copy of the antechamber, using the equipment and materials I asked for, in my proposal. I will try to explain again what I said about helping devices, using drawings this time: As you suggested the changing in the wooden beams for granite, and other mechanisms to lower the portcullises, I suggest these construction-aids to handle the slabs to lock position. 1. To lower the portcullises, one end of the rope lines have to be fixed (in my proposal), some men can hold steady the ends of the ropes, or if desired, the resisting force can be obtained, using a wooden device in front of the antechamber's entrance at the GG, as I illustrated in my previous post addressed to Jon. Four ropes can be tied up to a cross beam in front of the entrance, then, the action is just to pull the other ends, until slightly lift the slab (remember: one slab at a time).   As you will note, these simple construction-aid devices, consists of two sets of wooden columns and two wooden beams. Very easy to cut and place. There is no need to use the jaws of the granite slabs, or the level system. The holes for the columns at the south platform corners are there, could be evidence for them. All the other material (wood), was easy to take away at any time, leaving no traces of its use. However, simple devices like these will not permit the ropes to touch the rim of the north wall, and easier the task. After the portcullises are lowered, these helpful devices are dismantled and taken away. This was salvage material, usable in any other project.  For pushing stone blocks, like those plugs assumed placed in the lower corridors of the antechamber, besides wetting the floor with water, oil, grease, plaster, or whatever, we should consider the use of wooden beams for assistance. These beams, place over a side of the block, would allow many men to push the beam, and consequently the stone block to its position. In the case of the inside of the antechamber, a T shape device, built with crossed wooden beams, could help to push the stone from the inside of the GG, where more men could push.  Suggested wooden device, in T shape, for pushing the sealing stones inside the antechamber.  Samuel Laboy --------------------------------------------- Hi Steve: I think you have a good point, about the locking mechanisms. Locks go usually on the inside of doors and not outside. For example, I make sure that my doors are locked well on the inside, to avoid anybody entering my house. I could do something from the outside to prevent the intruders, but I feel more secure been locked on the inside. If the Pharaoh considered himself a living soul, eternal, he could ask the designer to make sure he was locked well on the inside of the chamber, so nobody enter, and he feels save. Therefore, the designer makes sure that he was locked inside the chamber, as apparently seen in the antechamber. However, we can get some light from JD, that is his line. I would appreciate his advice on these matters. Samuel Laboy | ||
| Janine Williams Senior Member Username: janine Post Number: 417 Registered: 09-2002 Posted From: 66.26.59.152 |
Sam: Superb, magnificent drawings as always. Janine | ||
| J.D. Degreef Senior Member Username: jd_degreef Post Number: 457 Registered: 02-2000 Posted From: 80.236.140.62 |
Dear Samuel, As the Chinese proverb says, "a picture says more than ten thousand ideograms" (or something like that), and now I understand what you mean. Thank you for the nice drawings ! But I still disagree, because of the following points : 1. your design doesn't consider the structure and features of the leaf slabs. With your design, one even wonders why the leaf stones were included in the first place. One also wonders why the vertical beams in the N space didn't deserve the same socket in the floor as the portcullis struts. 2. the rounded transverse beams which you drew aren't, and by far, of the caliber deemed necessary by the ancient architects to support the stresses induced by the mass of the portcullises. Your beams should be about a cubit in diameter, and if you redo your drawings with this dimension, you'll almost obstruct the crawling passage and will have problems fitting the whole thing in the northern part of the portcullises chamber and fastening the outer beam to the upright ones in the GG. 3. on the matter of the beam, I have of course to accept your calculations as an engineer, based on the use of a simple piece of wood. But the builders of the GP were extremely experimented in the use of levers. They would no doubt have found a solution to this. They already knew the technique of counterplating (as shown by some 3d dynasty pieces). So a compound lever is conceivable for the 4th dynasty : a piece of wood with the length of the fibers perpendicular to that of the rest of the lever, glued at the top and fastened by ropes. Because of the elasticity of wood, I suppose –that's all I can do...- that this would distribute the load in the top of the log, otherwise one would only transfer the problem lower down (well, I can always glue pieces of wood with fibers perpendicular to the force on one side of the main log, over its whole length ; give me glue and rope and nothing will stop me). Besides, the operation of the lever would take less than a second, not much time for this contraption to fall apart.  4. a few other less important details made me lift eyebrows : -the GG is 2 m wide, so you can place to pullers abreast there. So the transverse piece of wood would be of no great help, and if the portcullises were slightly lifted, then carefully descended into position by workmen in the GG, these probably pulled the ropes themselves. -could two or three men develop enough force on a transverse beam to push the very heavy plugs for the crawling passages, even on a lubricated floor ? And how to lift the plugs from the GG floor on top of the platform, with 50 cm of space on both sides ? -the GG benches have rectangular sockets along the whole length of the passage, from its upper platform to the vicinity of the entrance to the AP. This shows that the sockets weren't meant to hold the stored plugs (which couldn't be placed on either the platform or over the passage towards the QC). Giving the sockets on the upper platform a role in moving the portcullises seems to neglect the fact that they're part of a contraption involving the whole GG. IMHO, shallow and at an angle as they were, they held a light scaffolding, itself destined to maintain wooden panels with a false door motive. 5. as to Steve's remark that the portcullises room looks stronger near the KC, and weak, penetrable on the GG side, this may be due to the fact that we don't know what the missing pieces were in the roof (and possibly north) part. We know that something is missing above the E wainscot, but for the rest all we have is our imagination. If the upper part was almost filled with heavy granite beams, the room would have been less insecure indeed. A second aspect is that the builders may have sacrificed some of the sturdiness which they could have achieved, in order to build an automatic, self-closing chamber. We have two parallels to this : the oblique portcullises at the Bent (you remove the blocking log, and they slide into place all by themselves, or so the builders thought) ; and a second parallel is the stored plugs of the GG, sliding into the AP all by themselves once released –or so the builders thought : that this didn't work is one of the explanations put forward for the existence of the Well Shaft. So I still think that my variant of the POCHAN model is still the more probable one, taking the context into account (fad for automatic systems), plus the features of the portcullises chamber which you tend to neglect in favor of a hypothesis which appears simpler, but which doesn't go without difficulties. In any case this is one of the most fascinating discussions ever on this BB, and I want to thank all the participants and especially you for your patience and the pleasure you've given me, and for the always courteous tone ! JD | ||
| Janine Williams Senior Member Username: janine Post Number: 418 Registered: 09-2002 Posted From: 66.26.59.152 |
Steve: Nice perspective on the angle of your drawing, also a fascinating URL on ancient locks. Agree, the portcullis system (port system) can be no more than a deterent, not a block. Three granite plugs in the AP:... that is a block. Another puzzling thing about the KC is, that the GG grandly leads straight to it. If supposedly hidden, a spotlight couldn't do the job any better. I think the top of the granite leaf or couterweight (CW) may have been a trigger mechanism. It could not drop very far, and apparently didn't need to. Pull the prop out. If used as a rope clamp, it could use a coverplate with the ropes threaded through it. By the way, with all the ropes shown in a previousw URL, they surely knew something about knots...say, a loop slip knot - a pull from one end of the rope tightens it, a pull from the other end slips the knot out. Think there is better... (need a sailor on board.) As for the ropes: How the ropes are finally entangled, I will leave to the gentlemen. (I might think a high heeled shoe makes a great anti-roll prop, but they wouldn't.) *Note: The height of the east wainscot is approximately level with the bottom of the cradles on the west wainscot. (Ht west = 111 in; Ht east = 102 in...This assumes Lepre's measures of the west side go to the horizontal part that separates the cradles, and gives about a 9 inch dip to hold a large beam. It need not equal the radius.) Since the ports are definitely no more than a deterent, then they are either purely religious, (and JD was right to begin with)...OR...we have the dreaded, imaginary "Scenario X" : The counterweight mechanism is triggered from inside the KC. The KC has air channels, which the AEs built-in themselves...so I don't object if they used the room later. The entrance to the KC is not blocked. The deterent consists of three portcullises, supported by 3 wooden beams that reach past the east wainscot by less than ½ inch or so... very perilous...After the ports come down, the CW triggers the poles and they come down too! (In trouble...never mind half fast deterents..!) So, we are inside the KC, barricaded from a mob of frothing rabble who are part of the first IP rebellion... Nofret De Farge is in the lead. All are terror stricken. Where do we go from here? As planned, out the back door...a tunnel... The cover stone, which is low enough to maneuvered and re-set, must be replaced by the last men, and show no trace! (Pot of mud, inside .) So now what?...Where does the tunnel go? (Thanks to Blake): http://www.ldolphin.org/egypt/egypt2/fig109.jpg ......................******..................... All in all: I am now convinced that the porculisses had a relgious symbolism. Too many things indicate where the room is located, and as you said, if the builders wanted to block it, it would BE blocked. Janine | ||
| Steve Brabin New member Username: steve_b Post Number: 44 Registered: 09-2002 Posted From: 62.7.95.77 |
I knew I shouldn't have started reading these threads on the antechamber..... The following are two views of the antechamber from an AutoCAD reconstruction accurate in all details to 1/10th inch.   Hope the drawings are of use - for sure they show that the system is designed for blocking the exit from the KC no barring the entrance. If that was the case then how interesting that there are three ways out of the KC, all of which are blocked by doorways! (Nortern shaft,Southern shaft,passageway) I don't suppose that the antechamber mechanism was a counterbalance system so that the door could be opened from the inside? Because if it were, the ropes of the mechanism would have to be attached to the back of the blocking stone - for which you would need to attach a handle to the inside of the door to which to tie the ropes to. And a copper handle attached to the door would leave the handle fittings showing on the KC side of the blocking stone!! Best Regards Steve B | ||
| Steve Brabin New member Username: steve_b Post Number: 45 Registered: 09-2002 Posted From: 62.7.29.221 |
..... if that was the case then the back of the last block and the rope system would have looked like this :  and you can probably deduce what the other side of the block would have looked like!!!! Steve B | ||
| Mel Coldwell New member Username: melco Post Number: 28 Registered: 09-2002 Posted From: 136.8.159.10 |
It seems I have a couple of converts to "designed to keep something in" theory. But don't be limited to the roller/beam theory. It is already poorly supported (pun) by there being no radial feature on the Eastern wainscot. If we ignore this for the time being then any other mechanism can be considered. That in itself means the portcullis stones can be taller. However this is alot of work for a passage that is going to built and jammed in the open possition and then be closed once. Never to be opened again. I think not. Simpler systems could be devised. IMHO this really was intended to be opened and closed a few times. I'm still working on alternative mechanism. i have several principles but there not worth sharing untill I can get them to fit better with the available features. Lots of great work people. I'd be interested to here the religious conotations of locking something in the KC. | ||
| Janine Williams Senior Member Username: janine Post Number: 422 Registered: 09-2002 Posted From: 66.26.59.152 |
Steve: Those AutoCAD reconstructions are gorgeous! Indirect lighting, yet... emphasizes the 3D even better. Janine | ||
| Janine Williams Senior Member Username: janine Post Number: 423 Registered: 09-2002 Posted From: 66.26.59.152 |
Mel: Why would the AEs want to trap someone IN the KC?... King's spirit? Since the GP is the only pyramid in Egypt that has air-shafts...I consider "an escape for the king's ba" as a manufactured guess. There is no counterpart. It is people that need air, not spirits... Were the shafts designed for continued use, or for the building crew? (But I'm off your subject, here.) Who then? (The coffer isn't going anywhere.) Janine | ||
| Samuel Laboy Member Username: samuellaboy Post Number: 72 Registered: 09-2002 Posted From: 209.91.201.165 |
Steve, Thanks for the AUTOCAD drawings. Surely they are magnificent and will be very useful for all of us. I just wandered what would think the Egyptian antechamber's designer if he had the opportunity to see them. Regards, Samuel Laboy | ||
| Mel Coldwell New member Username: melco Post Number: 29 Registered: 09-2002 Posted From: 136.8.159.10 |
Hi Janine. I don't know why the AE would want to trap anyone in the KC. But IMHO the construction points this way. Possibilities:- 1. The KC contains some God power that shouldn't be released. 1.a The earthly trapings left after the new pharaoh was promoted to god when the old one died. (Had to go into the pyramid/temple perform a ritual, wash in the sarcophagus to cleans the body, discard old robes, call on the spirit of the old King, put on new robes? Having been reborn as the new pharaoh all old stuf was tainted so must be locked away) 1.b The relm of the god XXXX (not Fosters).(Permenant situation caused by containing ritual objects) 1.c Ritual summons the God for a periodic event/occassion. 2. Part of a test or ritual that requires survival for X days. 3. Its not a dead end. We just haven't found the other exit yet. (Anyone tried the middle stone, 3rd row up in the West wall?) I am also doubtful that the "air shafts" have a fundamental religious aspect. What is important is how the change in assumption from keeping people out to keeping something in afects our understanding of the function of the pyramid. This requires a much greater breadth of knowledge than I have. | ||
| J.D. Degreef Senior Member Username: jd_degreef Post Number: 461 Registered: 02-2000 Posted From: 80.236.159.92 |
Hi Steve, Wow, incredible CAD drawings ! Gorgeous lighting ! But the leaf stone is wrong. And with the disposition of the ropes in your last reconstruction, if you pull the portcullis upwards, it's going to hang obliquely from the four ropes, and shear against the slide walls. Dear Mel, If you look at a bank vault, the tightly fitting part is the deep part. The front end of the locking mechanism is more loose, and in plain sight, yet you can't enter. I'm not sure the disposition of the portcullises chamber indicates that something had to be locked in. Rather that what was being locked was the KC, but we already knew that... Looking forward to seeing an alternative model of the chamber, with levers and the whole thing... Dear Samuel, A question to the engineer : although my friction coefficient for rope on wood probably was a little too optimistic, static friction on the suspension beams combined with that on ropes jammed between the leaf stones -admitting for a moment that this was how the room worked- seems to have been able to keep the portcullises up after the supporting struts had been removed. On the other hand, dynamic friction doesn't seem to have had much effect on the speed of descent of the portcullises, which can only be described as "crashing" (one of the less satisfactory aspects of the model I'm defending). But is there a way to calculate the transition between static and dynamic friction resistance to movement ? Because since the portcullises' descent was a very brief event, the speed of the ropes never was very great. So could dynamic friction at low speeds not have been higher than the 10-20 % of static friction I read about in my textbook ? JD | ||
| Samuel Laboy Member Username: samuellaboy Post Number: 73 Registered: 09-2002 Posted From: 209.91.201.250 |
Hello JD, Here are my comments about yours: As the Chinese proverb says, "a picture says more than ten thousand ideograms" (or something like that), and now I understand what you mean. Thank you for the nice drawings ! (thanks) But I still disagree, because of the following points : 1. your design doesn't consider the structure and features of the leaf slabs (Yes it does, see my second schematic drawing). With your design, one even wonders why the leaf stones were included in the first place (they are needed). One also wonders why the vertical beams in the N space didn't deserve the same socket in the floor as the portcullis struts (The shorter are the beams, the better. They should be closer to the corridors sides for better performance.) 2. the rounded transverse beams which you drew aren't, and by far, of the caliber deemed necessary by the ancient architects to support the stresses induced by the mass of the portcullises. (I am not considering the mass of the portcullises, just of one). Your beams should be about a cubit in diameter (I doubt it), and if you redo your drawings with this dimension, you'll almost obstruct the crawling passage and will have problems fitting the whole thing in the northern part of the portcullises chamber and fastening the outer beam to the upright ones in the GG. (This is incorrect. The beam and the columns are easily assembled and disassembled. At the time of starting the lifting operation nobody should be going in, or out the corridor. The beam at the corridor's entrance is the last part of the operation. When the first portcullis is lowered, the front beam, if necessary can be moved to the side, until ready for the next slab). 3. on the matter of the beam, I have of course to accept your calculations as an engineer, based on the use of a simple piece of wood. But the builders of the GP were extremely experimented in the use of levers. They would no doubt have found a solution to this. They already knew the technique of counterplating (as shown by some 3d dynasty pieces). So a compound lever is conceivable for the 4th dynasty : a piece of wood with the length of the fibers perpendicular to that of the rest of the lever, glued at the top and fastened by ropes. Because of the elasticity of wood, I suppose –that's all I can do...- that this would distribute the load in the top of the log, otherwise one would only transfer the problem lower down (well, I can always glue pieces of wood with fibers perpendicular to the force on one side of the main log, over its whole length ; give me glue and rope and nothing will stop me). (Yes you will need much glue… and patience to deal with the project.) Besides, the operation of the lever would take less than a second, not much time for this contraption to fall apart. (It means that in less than a second you will find out if your system works!) 4. a few other less important details made me lift eyebrows : -the GG is 2 m wide, (Right!) so you can place to pullers abreast there. So the transverse piece of wood would be of no great help (My schematic drawing shows only possible, or maybe not possible in this occasion, but good suggestions, to pull or push the ropes. I believe the important thing is the system, not the pulling method. Remember the Egyptian supervisor had available as many men as he needed to pull. The ropes could be extended for the length of the Grand Gallery, over 150 feet, with as many ropes lines, as required (4 in my case). and if the portcullises were slightly lifted, then carefully descended into position by workmen in the GG, these probably pulled the ropes themselves (?). -could two or three men develop enough force on a transverse beam to push the very heavy plugs for the crawling passages, even on a lubricated floor ? (I think so, IMHO, plus using the T wooden adapter for pushing (my invention?) in front of the plug and its end along the GG' floor, improving the pushing power). And how to lift the plugs from the GG floor on top of the platform, with 50 cm of space on both sides ? (The top of the platform is about 10 inches above the benches. If wooden beams, about 10 inches diameter, were placed horizontally from holes to holes over the benches (about 27 beams), (I am referring to the holes dig into the walls, not those dig into the benches), and a sledge was used (the sledge's length should be so that when it clears the last beam, it is already over the front one), to roll the stone block over the beams to the great step, the stone block will arrived level with the platform. Please refer to the schematic drawing I used to illustrate Jon, one possible use for the platform corner sockets, using the same beam and columns mechanism to pull the stones over the inclined plane of the GG.) -the GG benches have rectangular sockets along the whole length of the passage, from its upper platform to the vicinity of the entrance to the AP. This shows that the sockets weren't meant to hold the stored plugs (which couldn't be placed on either the platform or over the passage towards the QC). Giving the sockets on the upper platform a role in moving the portcullises seems to neglect the fact that they're part of a contraption involving the whole GG. IMHO, shallow and at an angle as they were, they held a light scaffolding, itself destined to maintain wooden panels with a false door motive. (This would be eyes looking for religion motives, not for construction needs, that is a matter of opinion.) 5. as to Steve's remark that the portcullises room looks stronger near the KC, and weak, penetrable on the GG side, this may be due to the fact that we don't know what the missing pieces were in the roof (and possibly north) part. We know that something is missing above the E wainscot, but for the rest all we have is our imagination. If the upper part was almost filled with heavy granite beams, the room would have been less insecure indeed. (Steve, to my understanding, has a good point. There is nothing wrong in investigating it.) Anyway, the portcullises were not placed fitting their sides, they are separated by six inches one to the other. The builders knew how to place them together; the example is the first one, next to the south wall. To leave 6 inches between them sounds phony, they are vulnerable to the easy broken.) A second aspect is that the builders may have sacrificed some of the sturdiness which they could have achieved, in order to build an automatic, self-closing chamber. We have two parallels to this : the oblique portcullises at the Bent (you remove the blocking log, and they slide into place all by themselves, or so the builders thought) ; and a second parallel is the stored plugs of the GG, sliding into the AP all by themselves once released. (This last comment can be questioned. Pochan suggested as a possibility that the three plugs in the AP could have stored in the side of the corridor, in a place adjacent to the closing place. The same place Al Mammun excavated his passage to bypassed the plugs, That is, around the area we actually climb using a stair, to the AP. Therefore, if this space existed, it was gone with Mammun's passage. If the Caliph Mammum notices, somehow, that to the side of the plugs existed this cavity, surely he would have broken this way for his passage, as he finally did.–or so the builders thought : that this didn't work is one of the explanations put forward for the existence of the Well Shaft. (To me, the Well shaft was necessary when the full excavation of the subterranean chamber started. There were so much material to be extracted out of the pyramid, that they had to build a hasty passage to allow a special passage for the men going down to removed the subterranean excavation material, while the other workers coming with full baskets, could use freely the descending passage. It appears to me that this business started when the construction of the pyramid was still at the surface terrain level. The passage could have been continue up to the GG to allow closing the KC and the three plugs placed, leaving a escape way for the workers. All of these, (IMHO), could have happened.)} So I still think that my variant of the Pochan model is still the more probable one, taking the context into account (fad for automatic systems), plus the features of the portcullises chamber which you tend to neglect in favor of a hypothesis which appears simpler, but which doesn't go without difficulties. (JD, I am sure my theory could have difficulties, seen or not seen, anyway is just a theory, like yours and others presented.) In any case this is one of the most fascinating discussions ever on this BB, and I want to thank all the participants and especially you for your patience and the pleasure you've given me, and for the always courteous tone ! (Thanks to you and all the participants. Anyway, I am sure that many have copied this material for future reference, it is interesting, and contain unique drawings, such as those presented by Steve.) Samuel Laboy | ||
| Samuel Laboy Member Username: samuellaboy Post Number: 74 Registered: 09-2002 Posted From: 209.91.219.109 |
Hello JD, Although I do not like to check other designs than mine, since you asked for it, here is my analysis using of your jaws system, using your own numbers, that proves the leaf stones could not have been used as jaws. Here are the assumptions for this case (which seems to be the critical one): 1) Four ropes are used, each going through a corresponding hole in the three portcullis slabs. 2) The eight ends of the four ropes are to be held by jaw action underneath the leaf stone that has the boss. 3) The portcullis slabs each weigh 2590 kg. The leaf stone weighs 947 kg. 4) Distribution of weight between ropes is uniform. 5) Though strictly speaking, kgs are mass and not weight, I use them for convenience. Using your proposed system, the four ropes are supporting the portcullis slabs. For the moment, we leave aside the question of where the ropes are fixed. Using a simplified model (see below), we see that the weight supported by ONE rope is 2590(3/4)= 1942.5 kgs. The tension in the rope equals 1942.5/2= 971.25 kg. Now, we have eight ends of rope that will be clamped with the leaf stone. We (by some means) lift the stone and clamp down the ropes. Is this a stable system? As we can see below, the eight ropes form a support system for the upper leaf. The leaf weighs 947 kg, so the force that holds down each rope is 947/8= 118.375 kg. Let us assume a friction coefficient of 1 (!!!), for the sake of argument (all the benefits given). Friction force is equal to 1(118.375)(2) (2 surfaces, top and bottom)= 236.75 kg. And as we can plainly see: 971.25 (tension in rope) much more than >> 236.75 (friction force). So the leaf stone could not have been used to clamp the ropes, they would have gone flying the moment they felt the force from the slabs. What weight WOULD hold down the ropes (assuming, again, a friction coefficient of 1)? 971.25(4)= 3,885 kg. So, to hold down the ropes we would need a leaf stone with more than four times the weight of the actual leaf stone. See reference sketch for the analysis:  I believe this more than proves that the concept of jaws is not valid, which consequently makes unnecessary, the point of using the boss to lift the upper section of the granite leaf. So, JD, my advice would be to forget about the glue and tying ropes for the level, and try another way. Samuel Laboy. | ||
| J.D. Degreef Senior Member Username: jd_degreef Post Number: 464 Registered: 02-2000 Posted From: 80.236.140.150 |
Dear Samuel, A reply to a reply to a reply… 1. In your design, the leaf has two uses that I can see : -to allow the ropes to do a quarter turn -to screen off the empty space above the portcullises once they are descended. If we do some reverse engineering, what is the geometric shape logically following these specifications ? One slab (rather than a beam, which wouldn't screen), fastened in the walls, with a nicely rounded, level upper surface.  What is the shape we actually find ? Two superposed blocks. In a slide. The surfaces between the blocks nicely worked (not necessary if only the upper surface was used !). The upper surface irregular and sloping eastwards (not right if it served as a beam !). The northern surface of the upper block with a boss. Not at all the same thing. This points at the upper slab being lifted using the boss (and a fancy composite lever with glue dripping all over the place). You do neglect all the features of the leaf stones !  2. You don't take into account existing structures, such as details of the leaf stones or of the sharp rim of the doorway to the N crawling passage, so you're obliged to add wooden structures of your own (I add upper beams, but the empty space and the existence of missing pieces invites me to). The diameters of the beams which you drew are much too small. If a one cubit beam was used above each of the portcullises, this means that the builders deemed this size necessary to bear the load. When you pull up one portcullis and the rope you're using presses against a beam, the forces are –unless I'm wrong- of the same order of magnitude as those on the beam above said portcullis. So I'd expect the diameter of your supplementary beams to also be of the same order, i.e. one cubit. 3. Your mechanism for bringing the heavy plugs to the level of the upper platform is neat. But where would these plugs have been stored beforehand ? There is absolutely no proof of the existence of the POCHAN niche in the lower sidewall of the AP. But the major part of the AP, ceiling and walls, is very damaged, as if "with vinegar and fire", a clue to the existence of an extensive plugging which had to be smashed by the robbers. These plugs had to be stored somewhere, and their existence is the whole rationale for the existence of the GG : no AP plugs, no GG, just a small offering room near the portcullises, as in almost all later pyramids ! The GG is about 50 % longer than the AP. Even taking into account the existence of restraining systems for the plugs, these would hardly have occupied so much space. We also have to deduce the part over the passage to the QC, and the upper platform. This leaves some space at the top of the GG to store other material, possibly the plugs for the crawling passages. But placing these on top of the other plugs, as you want to do, although not impossible, sounds like a strange concept, which would imply a lot of crawling above or underneath plugs ! 4. On the gaps between individual portcullises : one finds those in the "normal" OK portcullis systems, even though no space for ropes was needed there ! 5. Thank you very much for checking my calculations. I answered hundreds of queries for info since I started posting here. But in the field of engineering, it's my turn to ask queries, and the only engineer we have on this BB is you, so, sorry, but you're my designated volunteer ... Could we do the calculation over step by step, since I can't follow yours ? Step 1 : since we don't know how many ropes there were, isn't it better to do calculations as if there was only one rope (you can braid or bind all the rope ends together before they go through the POCHAN jaws). Total weight of portcullises : 2,590 x 3 = 7,770 kgs. In my model half the ropes are suspended to the upper beams, so the weight on the ropes going to the leaf stones is halved : 7,770 / 2 = 3,885 kgs, pulling on the theoretical rope going through the POCHAN jaw. Step 2 : well, actually 3,885 kgs is not the force pulling on the theoretical rope, as we have to consider static friction against the lower suspension beams ! This involves friction against a quarter of the perimeter of the beam. I'm unable to calculate the integral involved. So I took as a mean value friction at 45°, sin 45° = 0.707, meaning that the force squeezing the rope against the beam is 3,885 x 0.707 = 2,746.6 kgs. Another unknown is the friction coefficient µ, which (unless they knew rubber ) isn't as high as I determined experimentally (I think the small piece of rope which I used could cling onto irregularities in the wood and would only start sliding at a higher slope than a heavier piece. Since I don't have heavy rope, I can't determine tg alpha = µ. But I'm sure you can do the integral and we can use µ = 1 as you generously proposed . This will yield the real force pulling on the theoretical rope. Step 3 : compare this real pulling force and the frictional effect of the upper leaf (in my preceding postings I didn't think that an upper and a lower surface had to be taken into account in this case, thank you for pointing this out !). I hope the above is clear and you'll be kind enough to do the calculation. At least if the model is wrong, we'll have found out how come Snefru had prosthetic toes... JD | ||
| Samuel Laboy Member Username: samuellaboy Post Number: 75 Registered: 09-2002 Posted From: 209.91.201.176 |
JD, In your calculation of the antechamber's dimensions, you calculated the height of the portcullis slab as about 146 cm, and the space available for it as 146 cm. So, you assumed that both measurements were equal, and the portcullis filled the entire space between the beam and the passage below. However, remember that the granite floor slab was raised (0.5"); therefore, at this section the height of the ceiling of the corridor would be only 109.73 cm, instead of 111. So, the calculation of the granite slab's height would be about 1.27 cm shorter than your calculation. In other words, the slab's height = (111 - 1.27) + 22 + 20 - 7 = 144.73 cm, or 56.98 inches. The lower section of the beam would be 282 - 24.7 = 257.3 cm, less the crawling passage's height (109.73 cm) would provide a 147.57 cm as the free space between these two points. If the slab's bottom was placed flush with the ceiling of the passage, the space between the lower part of the beam and the top of the slab would be 147.57 - 144.73 = 2.84 cm, or a little more than 1 inch. Little by little, it helps, no? Samuel Laboy | ||
| Janine Williams Senior Member Username: janine Post Number: 426 Registered: 09-2002 Posted From: 66.26.59.152 |
Sam, JD, Steve, Mel: WHAT IF: The ropes are set in two stages. What if: the leaf stones, as shown in Sam's last post clamping the ropes, had a cover plate with 'n' holes in it. The ropes are threaded through the separation of the leaf and through the cover plate holes, and tied in some manner. Say, Steve's. The cover plate fits into the section inside the rebates...size undetermined, and may have a socket to cover the boss. At removal time, untied the ropes, and remove the cover plate. If the top leaf doesn't readily release (and it shouldn't), give it an upward lift with an instrument that locks into the angle of the boss - it protrudes downward,and appears angled somewhat toward the passage. There is a place to stand there. Originally, there might be a problem getting the ropes between the two parts of the leaf unless the top section is suspended, or propped. Tighten the ropes according to Sam's method. (I would wet them and give them a good stretch. It would be that much less sag-stretch later.) As for originally setting the portcullises into place in a raised position (outside and from the top), do it in two or more stages. Done individually, starting at the south wall, lower one port to rest on an assist block. Raise the port again, to about 1/4 or 1/2 inch above the assists. Make 1st securement. Do for each port. When all three ports are positioned, thread the ropes through the separated leaf stones and through the holes of the one piece cover plate. Begin 2nd securement by Sam's method, then tightend and tie on the cover plate. BTW, Is there a north wall at this stage? Workers are both outside and inside. (If not, use plan BTTDB) The 'assist' blocks will stay in place after the final securement until the funeral is over and the ports are to be lowered. They are additional insurance. However, they will not interfere with the funeral cortege. The east wall 'assists' are the depth and width of the grooves; the height is as high as needed. Add a dab or two of sticky gum to the inside of the grooves, to keep them from accidentally tipping away from the grooves. It won't take much, it's only a balancer, but must stick...yet be pulled away without too much force. The west wall 'assists' can be much larger and any size that doesn't interfere with the passage of the funeral cortege. When time to lower the ports, remove the the assists starting at the south wall. (The north wall is in place, now, if it wasn't earlier.) Untie the cover stone of the leaf, and lower the ropes "according to plan" (some body's). I have doubts about two things: l.) Tying a thick 2" rope in a knot over a short space (would prefer two or three 1" ropes). 2.)Although the ropes can probably be secured and released well enough from the leaf stone, how are they arranged in the antechamber for permanent support, yet non-jamming release? ASIDE: If I read Lepre right, the level of the straight east wainscot is about level with the bottom of the cradles on the western one. They may not have needed two sets of cradles to prevent rolling...(Sam?)...as well as being able to more easily retrieve and re-use the long lasting beams. | ||
| Christian Koussiounelos New member Username: cck97 Post Number: 40 Registered: 09-2002 Posted From: 217.39.65.20 |
Sorry to barge in like this...! Admittedly, I haven't read every single word in this string yet, but I would like to ask another, rather simple, question. If something is meant to be sealed inside the KC, I believe 1 stone slab should have done the trick... the other 2 are a little redundant. If something or someone (or anyone for that matter!) was meant to be kept out of the KC, a system more akin to the granite plugs at the bottom of the ascending passage would have been more appropriate - sealed for eternity as it were. It seems to me that if a system of portcullis slabs was ever in place (and you must keep in mind that this is only a theory - who would ever break these slabs up and remove them completely from the antechamber??) then it was obviously used repeatedly, not merely to seal an entrance or an exit just the one time! It seems ridiculous that a system so complicated would have been put in place to seal a chamber once. The sad fact is that most theories begin with flawed assumptions. I am not proposing anything new here, just adding my pennie's worth! It just seems to me that this extremely complicated chamber may have served (and it is too complicated not to have) a purpose that we simply haven't figured out yet. Resorting to the spiritual is also not a solution in the face of that which we do not understand, yet. However, this chamber should not be treated in isolation. It's purpose would most certainly be very clear if we knew the purpose of the rest of the intriguing features of the Great Pyramid. I seem to have taken a step back from the discussion above and am looking at the broader picture, but I hope this will keep the ball rolling and perhaps open up new avenues of enquiry. Regards, Christian | ||
| J.D. Degreef Senior Member Username: jd_degreef Post Number: 468 Registered: 02-2000 Posted From: 80.236.140.202 |
Dear Samuel, Thank you for the correction of the portcullis height ! The 1 inch plus height which you may have made available could have been used for a wedge, which would have made removing the struts much easier. On the friction calculations of the ropes going over the suspension beams, something occurred to me : if one takes the two southernmost portcullises, their southern rope ends do a quarter turn over the beams lying above each of these portcullises ; then they go north, and do another quarter turn around the northern beam (which also serves as suspension beam for the northern portcullis), before descending to the mysterious northern part of the chamber. This double quarter turn is important when calculating friction tending to "hold the portcullises up" alongside the effect of the POCHAN jaws (if they existed). As to the ropes holding the northernmost portcullis up, they do their two quarter turns around one and the same beam : is this different, from a physical point of view, from the situation of the other portcullis ropes ? And here is my plan B if you prove that despite the above the POCHAN jaw wouldn't work : we could use your suspension method, and add static friction of the suspended portcullises against the northern part of the slides ! As to my plan C, I warn you that it will involve pixies, fairies and a lot of magic... Dear Janine, A plate covering the space between the rebates would indeed explain why the 1 inch deepening of the north face of the slabs wasn't limited to a narrow space around and below the boss. But what would be the rationale for the presence of such a plate ? A wooden plate to hold the ropes in some way (with protuberances to wrap them around ? with a basket shape to place the rope coils in ?). This could answer your two questions about tying and storing the ropes. As to the "assists" holding the portcullises up, they wouldn't need gum to remain in place, the weight of the portcullises and the fact that the struts are sunk into a floor socket would make this a very stable structure. So stable that an important problem would be how to remove them. About the cradles for the suspension beam being present on one side only, here's a possible reason : Egyptian architects were used placing round beams on top of walls, in palm tree log ceilings (see pic in Djoser's complex).  Each of these logs can only have rested in hemi-cylindrical cradles. So there was a concept at the time, "logs resting in hemi-cylindrical cradles". If I may quote a similar situation, one has the structure of horse-pulled carriages at the end of the 19th century. Then the internal combustion motor is invented, and what appears are automobile cars shaped like the old carriages, with a motor added. After some time one realizes that the horse-carriage shape isn't obligatory and indeed not the best one, and cars start looking like cars. To come back to the reign of Khufu, rounded suspension beams are to be placed horizontally above walls. So : hemi-cylindrical cradles according to the concept of the day. But it's important to increase friction, to avoid the beams turning. So one end is shaped so that it prevents rotation. This is the equivalent of the horse-carriage shaped car with a motor added. An archaeologist in the distant future, who would only have the early automobile, and wouldn't know about horse carriages, may wonder why on earth they were built with such a peculiar shape. As we wonder about the what and how of the suspension beams. Another possibility is indeed to make retrieval of the beams easier, but possibly also their placing : one end is entered into a rectangular socket on the east side, the other lain flat in the western cradle. Sockets on both sides would be more difficult. Hi Christian, Most pyramids have a triple portcullis near their exit, even though their descending passages are plugged. In the PTs the opening and closing of the Doors of the Sky is mentioned in the relevant part. The opening of the Sky Doors is a common expression in AE writings (the doors of temples and shrines are called Sky Doors, and when opening them to start a ritual, one "opens the Sky Doors" or one "enters the sky" (see Youth Text of Thutmosis III). But I don't remember a text mentioning the opening then immediately the closing of such doors. The reason, IMHO, is that the sky is opened to let the king's soul fly up and enter it, and that the closure alludes to the lowering of the portcullises. So the security role of the portcullises is paralleled by a religious one. As to repeatedly opening and closing the KC or indeed the pyramids : once their entrances were plugged, this was out of the question. Before the burial then ? The pyramid was part of a cult complex which already functioned during the king's lifetime, so your idea isn't impossible. There was a Holy of Holies in the upper temple (the zH with the false door), of which the KC is without doubt an equivalent (in decorated pyramids it also contains a false door, an extensive offering list, as in the temple's zH). But did it have to be so heavily sealed for this role ? I have my doubts. The sealing was very probably destined to preserve the king's glorified body and the important items of magical / religious nature placed with it during the funeral. JD | ||
| Mel Coldwell New member Username: melco Post Number: 31 Registered: 09-2002 Posted From: 136.8.159.10 |
Hi JD, In your very usefull picture. Are the "log" resting in cradels? The left hand side looks like they have a flat cut on them. Christian. I agree with many of your points and also try to step back from some details. As JD has mentioned the use of 3 portcullises is not unique. Since the whole pyramid is almost certainly of religious significance then the use of 3 ports is probably also religious. I did read somewhere a reference to 3 guardians to the relm of Sokhar. (Did I spell that right?) I don't know if JD can come up with a reference? | ||
| Mel Coldwell New member Username: melco Post Number: 32 Registered: 09-2002 Posted From: 136.8.159.10 |
Heres an idea:- The leafs have nothing to do with the mechanism. When the chamber is built the upper leaf is stored resting on the TOP of the wainscots next to the North wall. Its not in the slots. The "boss" prevents it butting right up to the North wall so you can still get hold of it. The portcullis slabs are moved. Without the upper leaf access to the holes in portcullise slabs is easy when they are raised or lowered. The ropes and mechanism are removed. A block is placed on the lower leaf and the upper leaf is moved into the slots and lowered on to the block. Wooden planks are fitted between the upper and lower leaf and wedged up to take the weight of the upper leaf. The planks protrude across the space to touch the North wall. The block is removed (planks support the upper leaf) and the last plank inserted in the gap left by the block. The wedges are removed so all the planks and the upper leaf are lowered until they rest on the lower leaf. We now have a wooden ceiling blocking access to the top of the portcullis stones. Over the years the wood has been robbed out. Since the upper leaf is hidden by the ceiling it doesn't require fine finishing. | ||
| J.D. Degreef Senior Member Username: jd_degreef Post Number: 472 Registered: 02-2000 Posted From: 80.236.159.38 |
Hi Mel, The logs forming most ceilings in Djoser's complex are of course stone copies of the real thing, as are the wickerwork chapels etc. There are no real stone logs placed on top of the walls, but ceiling blocks sculpted to resemble logs. But this doesn't mean that the concept of "log in cradles", used continuously when new palaces and houses were built, wasn't in the architect's mind when designing the portcullises chamber, with beams resembling ceiling logs. I don't know about the three guardians of Sokaris' realm. On your idea concerning the leaf stones, as having played a role in the placing of a wooden ceiling : such a ceiling would have offered little protection, and the technique sounds a wee bit too complicated, no ? JD | ||
| Samuel Laboy Member Username: samuellaboy Post Number: 76 Registered: 09-2002 Posted From: 209.91.200.76 |
JD, Janine, Mel, Steve, and others: I think there is no problem in holding the portcullises in the up position for a long period of time, and lowering them when the time comes. When the portcullis slabs are lowered from the top of the antechamber, without ceiling, they are lowered and supported by the already placed struts (or wooden supports). They are leaved there until the pharaoh's death. There is no need for wiring the ropes at that time, or do anything else. The system consists of three portcullis slabs, supported at the two extremes. Exactly like a beam supported at both ends, they are stable in that position. There is no need to find storage for oil, grease, plaster, or to storage the ropes, auxiliary wooden beams, etc. The corridor passage will be free to pass in and out. I do not see any problem with this. When the time comes to lower the slabs, (as suggested - about 20 years later), the following action should be taken. Since there is no time limit to rush the job. All required material, implements, could be easily obtained (fresh from the department store) at that time. What we need? 4 ropes 2 additional ropes to pull the wooden supports Some auxiliary pieces of wood, in case they are needed. The number of men required to pull the ropes. What we do: Use my original system exposed in my proposal to lift the blocks, one at a time, and then lower the slabs. There are many ways to ease the way of doing the same task. I offered my original version as one of them. Others can be used, as the one I suggest now, based on Steve's version. Although these ropes could lift the slab, more checking would be necessary, but as JD, said, by experience, the builders knew what type of rope and where to use them. In this case, both ends of the ropes would be pulled.  Our job is to lower the slabs, one at a time. Therefore, when we get the required materials supplies, we start the following process: 1. All the supplies, being in the platform entrance, a man enters the antechamber with one rope end and wire it around the portcullis slab, as indicated in my proposal. The wiring of the ropes could be also changed as suggested in my drawing. In this last case, there is no need for the ropes to slide inside the slabs holes when the lifting operation starts, they are just tying the slab to allow pulling them up. Any other method could be used, if appropriate. 2. Another man enter underneath the slabs and tie a rope to pull the wooden slab-support, out of the way, when the pulling of the upper ropes relieve the weight. 3. If the specifications of the pharaoh indicates that the rims of the north wall should not have grooves for the ropes, to save the pyramid's esthetics, just another short piece of a round log, having a cut about a quarter diameter, and placed lengthwise against the corner of the wall (as shown in the drawing) could do the work.  4. The ropes will pass under this attached log section to the GG, where they will be pulled. In this arrangement, both ropes ends could be pulled at the same time, as stated. 5. When the slab is just slightly raised, and the men pulling the wooden supports pull the two slab supports out of the way, the men pulling in the GG, having still the lift-force in their hands, start releasing it slowly, to lower the slab to position. The first portcullis is down. 6. The men enter again into the antechamber; completely remove the released wooden supports out to the GG. One end of the rope is left in the GG and the other end is used to re-wired in the same form, the middle portcullis slab. Remember, the upper wooden beams, are just sitting there, there is no weight over them. Therefore, they can be lifted and move them over the top section, as necessary. You can even move one on top of the other, is you need more space to work the ropes between the slabs. Before the system is ready for lowering the next slab, the second slabs supports are tied to be pull. The same process is done to lower the second slab. 7. Then, finally using the same process, the third portcullis slab is lowered. 8. In this case, we are not using my suggested construction wooden-aid inside the antechamber, (to avoid the groove cuttings in the rim of the north wall). However, the outside system is used. In this case, the ropes lines will pass over the outside beam. This is a benefit for the system because will help the men to control the descend of the slab, when releasing the pulling force. See the suggested method in Arnold's book to lower a coffin down to the pit. It shows us how simple could be the operation.  Therefore, why do we have to drop the three slabs at the same time? If we can do it one at a time. Why do we have to use the jaws? If there are simple ways to hold the ropes. Why do we have to depend on static friction or any other friction to hold the slabs? If the wooden supports take care of it, until the slabs are lowered. Why do we have to do a lot of turnings of ropes around the beams? If we need only to tie the slab and pull. Why to use another system over the system to lower the slabs? If we have all required elements to lower the slabs. Why to use the boss to lift the granite slab? If there is no need to rise the slab. Why to risk people inside the antechamber? If they can work from the outside in the GG. Why risk the antechamber's floor by slamming 8 tons of stone in a flash? If they can be place slowly one at the time. I believe that putting more effort in calculation of friction, stresses, and complicated systems, to me, makes it a sterile discussion. Sometimes a simple solution could be the correct answer. There are some aspects that worry JD; one is the struts removal of the wooden supports for the slabs, and their final remotion from the antechamber. The following sketch shows what I meant to cut horizontally the supports, flush with the floor, to allow the easy pulling to remove them, out from underneath the slab. The inside wood section in the cavity, is left there, since it will not affect the lowering operation, or the slab final resting place.  Another is the rim of the north wall. What about if the builders used the suggested log-cut system shown above. The pulling force will overcome the friction force generated. Besides, I believe never, the friction force will hold these slabs from going down, only a full restraining force will do. The friction force will be there, but it will be much less than to hold the slabs. These are my ideas about this type of work. To try to explain every detail we find in the antechamber as used of the lifting operation, do not sound right to me. For example, to assume that the top left, of the granite slab, which is broken toward the left, was cut in that way by the builders, either. If the intruders break down the portcullis slabs, why not assume they broke this corner. As another example: because the coffin has a broken corner, and we found it in that shape, we do not have to blame the builders by assuming that it was built in that way. As I have always said, the only posibility to me about the boss is that it represents a seal of identification. If this were the case, the designers would be (in the other World) in deep sorrow that we have done nothing to find its meaning, labeling it as nothing of importance. Why attribute so much sinificance to the meaning of the three portcullis slabs, and nothing to this extremly worked surface with this carved sign. Was this granite slabs, besides a support for the ropes, a stelae for the pyramid, with a protection sign against the robbers, ordered by the pharaoh? We do not know now, maybe some time later. Samuel Laboy | ||
| Janine Williams Senior Member Username: janine Post Number: 428 Registered: 09-2002 Posted From: 66.26.59.152 |
Samuel, JD, Chris: Chris...Good thoughts all the way! Samuel...Agree, no need to put the ropes in until the chamber is to be closed. Also agree it is not practical to lower all three ports at once... In fact, am not sure about letting even one "slam" to the floor because of the vibrations. There may be a problem in the first diagram above, based on Steve's version, because the center of gravity is off and lower edge of the port might jam. What if: The rope were looped through the port hole (loop goes through first and emerges facing the leaf stone. Rope ends are pulled through it.) ...Gravity would be centered. ...The knot would tend to tighten. ...Workers might raise the ports a little,even with the loops, when ready to free the supports. ...The rope would be re-usable, if no fraying. A method is needed to prevent slamming the port to the floor. Friction from the ropes through the loop, when freed, might slow it down a little, but not to depend on. The clamp of the Leaf stones might be used to retard the release speed. With the boss, it looks raisable, lower and raise once for each port. OBJECT - Drop speed control: Scenario: Workers are raising the port, by manpower, for inside workers to remove the supports (which must be small enough to get past the others). When the supports are out, an inside worker lowers the leaf stone clamp, the workers outside the AC release the ropes slowly. The clamp may allow the ropes to slip gradually, bearing the weight of one port. If needed, the drop speed can be increased by raising the top leaf part way, using the boss. Other viewpoints? Janine JD: The cover plate would have taken only the stress of "rope slippage" that could occur if all ropes were in the leaf clamp. The clamp would have taken the bulk of the stress. But that is for long term positioning of all the ropes...The other way is better...(Sam's system of roping only one port at a time during closure). About the "assists", vs. support blocks...don't need both. The "assists", being 1/4 to 1/2 inch below the ports simply makes them easier to remove, but have the disadvantage of placing all the weight on the ropes for several years.(Long term view)... they are not needed if the ports originally rest on the supports and the supports can be removed safely. Also will not need a couple of wads of "goo" behind the narrow supports. The port itself will keep it from tipping. However, for anyone that wants to know: One "wad" works perfectly for 1" x 1/2" sticks painted white to hold up a back window sash that wants to drop. Bubble gum (well chewed) is perfect. Juicy Fruit and Spearmint don't work. Glue had problems. Janine | ||
| J.D. Degreef Senior Member Username: jd_degreef Post Number: 476 Registered: 02-2000 Posted From: 80.236.140.149 |
Hi Samuel, 1. I'm rather disappointed that you don't want to help with the calculations. They would have taken 10 minutes of your time, and I'll need a whole day. To get a result which I won't be able to trust. 2. We don't seem to be providing answers to the same question. You answer : "how would I use the portcullises chamber ?" I answer : "What was the mechanism of the chamber which the Egyptians intended, based on the archaeological features ?". 3. Your idea about wiring the chamber right before the portcullises have to be lowered : IMHO it wouldn't simplify things, at the contrary, and wiring the built chamber would be almost impossible. See for yourself : -a worker is sent up in the space above the portcullises, resting on their struts and surmounted by their heavy suspension beams (wood or granite). The worker is helped up the one cubit wide space between the leaf stones and the north wall. One cubit ? Not with your rounded beam protecting the upper door rim ! So you have to place this after the worker has climbed up, locking him in. Kind of weird ! So you'll wait until he has wired the one portcullis, let him get out, place the beam, pull the portcullis support struts away, lower the portcullis, remove the wooden beam, send the worker back in, and restart the whole procedure. Kind of complicated ! -what does he see once he's above the suspension beams ? Not much : where do you place a lamp ? Where is there a horizontal surface to do so ? You can lift one in the northern space. Not ideal (the worker's hands will always be in his own shadow), but it will have to do. -the rope ends are passed on through the northern space. OK. -now he's going to wire the southernmost slab, lying uncomfortably on the beams (or on a thin board brought in through the northern space). What does he see ? The south wall with the grooves. A 25 cm wide, near prismatic space between this wall and the beam. How is he going to wire the portcullis ? He pushes one end of a rope down in a wall groove. The groove extends until near the level of the crawling passage towards the KC. At one point, about 20 cm below the beam, lies the portcullis suspension hole. How is the rope going to know it has to do a 90° turn inside the groove and enter this hole ? As far as I can see, the rope is going to descend until it reaches the tapering end of the groove, and be stuck there. How about entering the rope in the opposite end of the suspension hole ? This lies more than 70 cm deep in the narrow space between the portcullises. The worker's arm doesn't reach that far (try with your own arm !). And even if he manages to push the end of the rope in the suspension hole, a 2" rope is fairly rigid and doesn't easily bend by 90°, so pushing the rope from above may not make it continue to slide into the hole 70 cm below. And when the rope comes out on the groove side, what would make it bend upwards . So it will be hard to retrieve from above. -you can try wiring the northern portcullis first, but looking at LAUER's section of the chamber, the suspension hole would be lying between the leaf and the portcullis (this would need to be checked using the real dimensions and the 20 cm distance between the top of the portcullis and the lower rim of the suspension hole, as roughly determined from Charlie RIGANO's photograph). In any case, wiring the room wouldn't be as easy as your postings seem to imply, and IMHO this isn't a logical procedure to follow. Then there's your excellent idea that the south wall grooves extend up to ceiling level because the portcullis was lowered using ropes passing through its suspension holes. My calculations have also shown that the specifications for the ropes correspond with modern safety regulations for ropes to be used, not once, but some time. So I don't see what would be wrong using new ropes to lower the portcullises onto their support struts while building the chamber. Leaving these ropes in place. Wiring the chamber as new elements are added on top of the portcullises. Restraining the rope ends that need to be, placing the moving ends between the open jaws of the leaf stones. No strain on the ropes, they remain slack, no wear, no action of moisture or ultraviolet : we still found the ropes of Khufu's bark after 4600 years. The ones in the portcullises chamber would have kept well for tens of years, no problem ! 4. As Janine has noted, but using kinder words, your new suspension method is absurd, as the portcullis would tend to hang obliquely from one side. Considering the above, it would also be more difficult to wire the portcullises this way (think of the 180° bending of 2" rope in a narrow space ! How would you go about doing this ?). 5. Removing the suspension beam (and possibly using only one item, moving it and placing it above each successive portcullis) is a new and interesting concept, to keep in mind, and which may save your wiring model (although it would bring the worker's hand nearer the suspension holes, the wiring still wouldn't be that easy). But a portcullis chamber with a huge empty space above it is quite absurd, so one should seriously consider that the beams were granite, not wood, and that there was an upper level of beams neatly filling the chamber. The only drawback is that not a single fragment of such granite drums was ever found. But even broken they may have been valuable to make stone vases during the MK, and thus be taken away and hollowed out. 6. As to your questions : >Therefore, why do we have to drop the three slabs at the same time? If we can do it one at a time.< An annoying aspect of my hypothesis, which I admit. Maybe there's a solution which would be a variant of Janine's leaf stone cover plate hypothesis. Maybe after the struts were removed, the ropes weren't only held by friction forces on the beams and in the POCHAN jaw, but also by vertical beams (side length = space between rebates minus width of boss lifting piece, divided by number of ropes ; or even total available width minus width of boss lifting piece, divided by 12 ropes). Since these vertical "rope holders" would push against the leaf stones, they would make lifting the upper leaf more difficult. But the lever system I drew was so easy that two men could lift the upper slab. So here we'd put a few more to overcome the supplementary friction. The good news is this may increase the force with which the POCHAN jaw clasps the ropes ! >Why do we have to use the jaws? If there are simple ways to hold the ropes.< Because the jaws are there, and the whole structure of the leaf stones contradicts your simplistic use of them ! >Why do we have to depend on static friction or any other friction to hold the slabs? If the wooden supports take care of it, until the slabs are lowered.< Static friction isn't used until the struts are removed ! >Why do we have to do a lot of turnings of ropes around the beams? If we need only to tie the slab and pull.< The trajectory of the moving strands of rope is almost the same in my model as in yours ! In mine the ropes don't pass over the oblique and rough upper surface of the leaf, that's all. >Why to use another system over the system to lower the slabs? If we have all required elements to lower the slabs.< I don't understand your question. If you mean the supplementary set of suspension beams over the lower ones, these can easily be avoided this way :  But this leaves the large empty space under the roof unexplained. And could weaken the suspension beam. >Why to use the boss to lift the granite slab? If there is no need to rise the slab.< Archaeologically, the leaf stones are in slides, as are the portcullises. The upper one has a boss, displaced away from the midline (which I explained by the oblique upper rim, causing the slab's center of gravity to be displaced likewise). So : slabs in slides, with boss = structure which can be lifted. If it was built, it had a planned use, involving lifting. Whereas you degrade it to a simple beam, the exact only use which it couldn't have had, given the state of its upper surface. Nobody ever speaks of its upper rim being broken, only of it having remained in its natural state, as found in Aswan. >Why to risk people inside the antechamber? If they can work from the outside in the GG.< Yes, a perilous job, knocking the wedges away at the top of the struts, then quickly removing these. But building the pyramids must have involved other perils (pulling the huge KC granite beams and placing them !) and this didn't stop the kings from building them. >Was this granite slabs [leaf stones], besides a support for the ropes, a stelae for the pyramid, with a protection sign against the robbers, ordered by the pharaoh?< A protection sign in Egypt was an Evil Eye, or a Double Bull (both from PTs), and the sign for protection itself (zA) was a restraining rope for calves. Not a boss ! Hi Janine, I'm sorry but I don't understand your explanation : >What if: The rope were looped through the port hole (loop goes through first and emerges facing the leaf stone. Rope ends are pulled through it.) ...Gravity would be centered. ...The knot would tend to tighten. ...Workers might raise the ports a little,even with the loops, when ready to free the supports. ...The rope would be re-usable, if no fraying. A method is needed to prevent slamming the port to the floor. Friction from the ropes through the loop, when freed, might slow it down a little, but not to depend on. The clamp of the Leaf stones might be used to retard the release speed. With the boss, it looks raisable, lower and raise once for each port.< I do need a way of slowing down the portcullises' descent (unless the transition phase between static and dynamic friction provides for sufficient slowing down, given the short time span ? But despite all my good will, this isn't something I'm able to calculate or prove.) JD | ||
| J.D. Degreef Senior Member Username: jd_degreef Post Number: 481 Registered: 02-2000 Posted From: 80.236.134.56 |
PS : for those in favor of the moving around of the suspension beam(s) idea, such a beam weighed about 250 kgs = 500 pounds ! By a single man in a cramped space. Not easy, to say the least ! JD | ||
| Janine Williams Senior Member Username: janine Post Number: 431 Registered: 09-2002 Posted From: 66.26.59.152 |
JD: Agree. Setting the ropes in place during construction is the simplest way. Thought about Khufu's barque, too, and wondered why a new rope, unstressed, wouldn't last a least 30 years? This would also take care of the lighting problem (good point)! No accidents needed. So far, I don't agree with anybody's method of securing the ropes, including mine...which won't work trying to loop a 2" rope through a 3½" hole!... Although it might work using a 1½" rope...(Perhaps that's why there are more than 2 holes in some ports.) However the ropes are tied and set, it would be done outside in the daylight and the balance and center of gravity of the ports tested then, before lowering onto the support blocks. Storage of what are probably long rope ends should be above the beams and laid out "Ship-shape" ready for use. Storage between the leaf slab and the north wall is not good. Someone may have to stand there, if the leaf is to be opened and closed. The use of the leaf clamp (I keep picturing shark teeth with 'jaws'), might work to control the drop speed if the ports are dropped one at a time. Although no one has said that all three ports had to be dropped at once, in my view it is not worth considering. To do so, simply adds more associated hazards and stress problems that could be avoided. Control is essential, since the clearance is only thought to be about 1/4 " on either side of a 20" port. Hopefully the end clearances are at least and inch or two (E/W) in the 3" deep channels, because if one rope in one hole is released without the same tension as the rope in the other hole, the port would tend to wedge east/west. So what have we got? l. New ropes, partially set and balanced when the ports are put in, under well lighted conditions. 2. Ports are supported by support blocks, the ropes are slack. 3. Rope storage is above the beams laid ready for use. 4. At final closure, ports are lowered one at a time. 5. The granite leaf blocks are not excess baggage but in use. ...the leaf blocks are apparently constructed to be raised and lowered. (It has a "lock-stop" in the channel which has supported it for 4500 yrs. so it probably did not need a beam.) The boss may aid in moving the top leaf, since it protrudes at the bottom and is angled in the direction where a worker would stand. (The offset of the center of gravity by the boss may be negligible.) 6. The granite leaf provides control of the drop speed. With tolerances that close, the port could become wedged in either direction, just as well as not. We still need: A workable method for setting of the ropes for final closure... JD's idea of drilling the beams with 3½" holes may not weaken a 21" beam that much...the weak spot, at least the one that troubles me, is the knot. JD: The loop described is hard to draw and I don't have an auto cad. Try it, according to the directions, with a piece of string looped over a round pencil and any small symetrical weight. The loop must face the direction that will cause it to tighten when a 'pull' is applied to the string. The loop is fixed at the center of the top of the pencil, although it might not have to be...? It could be somewhat on the south side and used to raise the ports a small amount to retrieve the supports. (?) The rope will only be used once, but the concern is whether or not the loops are stong enough to hold the port for drop time needed. All the stress would be on the loop. Rope retrieval: When all the ports are down, send a worker up above the beams to sever the loops, knots, or whatever is up there. Janine | ||
| Samuel Laboy Member Username: samuellaboy Post Number: 77 Registered: 09-2002 Posted From: 209.91.200.136 |
Hello JD, This is in response to your post No.464. Normal and red yours, bold and black- mine Here we go again… 1. In your design, the leaf has two uses that I can see : -to allow the ropes to do a quarter turn -to screen off the empty space above the portcullises once they are descended. (I see other uses: As rope bearing support, as an identification stelae, with a prepared surface and a carved sign, representing the Pharaoh's Seal, similar in concept to the stele in front of the Sphinx and many temples and pyramids (I have answered that many times) If we do some reverse engineering, what is the geometric shape logically following these specifications ? One slab (rather than a beam, which wouldn't screen), fastened in the walls, with a nicely rounded, level upper surface. What is the shape we actually find ? Two superposed blocks. In a slide. The surfaces between the blocks nicely worked (not necessary if only the upper surface was used !). The upper surface irregular and sloping eastwards (not right if it served as a beam !). The northern surface of the upper block with a boss. Not at all the same thing. This points at the upper slab being lifted using the boss (and a fancy composite lever with glue dripping all over the place). You do neglect all the features of the leaf stones ! 2. You don't take into account existing structures, such as details of the leaf stones or of the sharp rim of the doorway to the N crawling passage, so you're obliged to add wooden structures of your own. I am not supposed to take into account the existing conditions and details of a structure built 5 millenniums ago to realize an structural evaluation. I am sure the ancient designer will feel very unhappy if he knows that I am bypassing all his rightly done designs and builders work, to considered and give only credit to the trash that had been put into their work, by time, robbers, intruders, visitors, earthquakes, etc. Most probable, this granite slab top was well cut, and placed. Why assumed that the ancient builders built it in that slopping way to the side? Why not assumed that this section was a victim of the same people that break the portcullises into pieces? Do you consider also that the Pharaoh's sarcophagus was built with the split corner? I have to consider that these ancient people, capable of doing such a magnificent monument, were very intelligent and full of ideas to deal with stone and wood construction. You said that I am obliged to add wooden structures of my own. I am not obliged, I just suggested a method that the intelligent builders could have used, where the sharp rim of the doorway to the North crawling passage could no be affected. Therefore, if you can suggest that upper beams, over the upper beams, could have been used because the empty space and the existence of missing pieces invite you to, why I cannot use the same invitation? The diameters of the beams which you drew are much too small. If a one-cubit beam was used above each of the portcullises, this means that the builders deemed this size necessary to bear the load. Incorrect! Besides, you cannot base the diameter of the beam based on my schematic drawing. I am not using any scale for the drawing. JD, the builders, in many occasions used the materials at hand, if safe to used. If they need a 6 inches tree trunk, and have available one of 10 inches, well, better for them. Do you think that those massive round columns used to support the temple's ceilings are required? Probable columns with half the diameter, or less, could very safely do the work. But in these occasions the designers want to implement a good appearance, esthetics, and build all columns of equal diameter. Therefore, the fact that they used a 20 inches diameter wooden beam for the upper section of the portcullises do not imply that they have to use the same diameter, or larger, in another place. There are many other ways to solve the ropes passing through a sharp rim without having to break them off. Anyway, even using a very large diameter beam in front of the corridors, they are very easy to dismantled after each portcullis is placed. The only thing to consider would be that the pulling of the wooden portcullis supports will be done just to move them out from the slab base. When the entrance is open to prepare for the second lowering, they are taken out to the GG, just a minor detail, easy to fix. When you pull up one portcullis and the rope you're using presses against a beam, the forces are –unless I'm wrong- of the same order of magnitude as those on the beam above said portcullis. (But the stresses could be different according to the beam's area) So I'd expect the diameter of your supplementary beams to also be of the same order, i.e. one cubit. My drawing is schematic; you can't consider the diameter shown as the required to handle the stresses). If someone have used a 20 inch pipe diameter to supply water to a field, but a 6 inches pipe is enough according the amount of water, and you need to add more pipe lines, will you spend the required excess money to buy 20 inches pipes to continue the pipe's line, or prefer a box and transfer to 10 inches pipe lines (without any risk)? This example is for illustration only. 3. Your mechanism for bringing the heavy plugs to the level of the upper platform is neat. But where would these plugs have been stored beforehand? (I do not know it would be speculations on my part). There is absolutely no proof of the existence of the POCHAN niche in the lower sidewall of the AP (or that disproved!). But the major part of the AP, ceiling and walls, is very damaged, as if "with vinegar and fire", a clue to the existence of an extensive plugging which had to be smashed by the robbers. These plugs had to be stored somewhere, and their existence is the whole rationale for the existence of the GG : no AP plugs, no GG, (JD, I have other ideas about this, the GG have other connotations. The Grand Gallery forms part of my design of the Great Pyramid, as if it were inherent with the design, therefore, to me, it was not built to handle the plugs, although it could be used for that purpose). just a small offering room near the portcullises, as in almost all later pyramids ! The GG is about 50 % longer than the AP. Even taking into account the existence of restraining systems for the plugs, these would hardly have occupied so much space. We also have to deduce the part over the passage to the QC, and the upper platform. This leaves some space at the top of the GG to store other material, possibly the plugs for the crawling passages. But placing these on top of the other plugs, as you want to do (When and where I said that?, although not impossible, sounds like a strange concept, which would imply a lot of crawling above or underneath plugs ! 4. On the gaps between individual portcullises : one finds those in the "normal" OK portcullis systems, even though no space for ropes was needed there ! This again, suggests Steve's idea, to me, no? Why these spaces? They make the closing vulnerable from the outside, although more difficult for the Pharaoh's soul to get out. 5. Thank you very much for checking my calculations. I answered hundreds of queries for info since I started posting here. But in the field of engineering, it's my turn to ask queries, and the only engineer we have on this BB is you (You are certainly very incorrect about this, there are more engineers in the board than what you think!) So, sorry, but you're my designated volunteer ... Could we do the calculation over step by step, since I can't follow yours ? If you cannot follow my calculations, how can you follow my calculations of your work? I am really sorry about disappointing you, I do not want, and will not get involve in professional engineer debates in the Board about engineering structural designs and structural matters. I will leave open these questions for anyone to answer. I am completely sure, that you will no believe or trust the results of my work, see all the underlying red notes you wrote, and you will see that I am not a person to trust. My advices and suggestions are neglected. How could you trust my calculations? However, at the time you start questioning my results, a professional engineering debate will start, and never end, since, apparently, that is no your field. I am please to participate in the discussions, answers questions, and perhaps, calculate and present my solutions, as I believe in them. So, sorry JD, really sorry.} Step 1 : since we don't know how many ropes there were, isn't it better to do calculations as if there was only one rope (you can braid or bind all the rope ends together before they go through the POCHAN jaws). Total weight of portcullises : 2,590 x 3 = 7,770 kgs. In my model half the ropes are suspended to the upper beams, so the weight on the ropes going to the leaf stones is halved : 7,770 / 2 = 3,885 kgs, pulling on the theoretical rope going through the POCHAN jaw. Step 2 : well, actually 3,885 kgs is not the force pulling on the theoretical rope, as we have to consider static friction against the lower suspension beams ! This involves friction against a quarter of the perimeter of the beam. I'm unable to calculate the integral involved. So I took as a mean value friction at 45°, sin 45° = 0.707, meaning that the force squeezing the rope against the beam is 3,885 x 0.707 = 2,746.6 kgs. Another unknown is the friction coefficient µ, which (unless they knew rubber ) isn't as high as I determined experimentally (I think the small piece of rope which I used could cling onto irregularities in the wood and would only start sliding at a higher slope than a heavier piece. Since I don't have heavy rope, I can't determine tg alpha = µ. But I'm sure you can do the integral and we can use µ = 1 as you generously proposed . This will yield the real force pulling on the theoretical rope. Step 3 : compare this real pulling force and the frictional effect of the upper leaf (in my preceding postings I didn't think that an upper and a lower surface had to be taken into account in this case, thank you for pointing this out !). I hope the above is clear and you'll be kind enough to do the calculation. At least if the model is wrong, we'll have found out how come Snefru had prosthetic toes... (It is being said that Benjamin Franklin was asked what he had learned about his light bulb invention. He answered, "Well, my friend, one thousand and one different ways to make a light bulb that doesn't work!".) Samuel Laboy | ||
| Samuel Laboy Member Username: samuellaboy Post Number: 78 Registered: 09-2002 Posted From: 209.91.200.144 |
Hi JD, As before, I used your same post to answer, since is easier for me and at the same time those members that read the posts know the questions behind the answers. Normal - JD, black and bold, Samuel: 1. I'm rather disappointed that you don't want to help with the calculations. They would have taken 10 minutes of your time, and I'll need a whole day. To get a result which I won't be able to trust. 2. We don't seem to be providing answers to the same question. You answer : "how would I use the portcullises chamber ?" I answer : "What was the mechanism of the chamber which the Egyptians intended, based on the archaeological features ?". 3. Your idea about wiring the chamber right before the portcullises have to be lowered : IMHO it wouldn't simplify things, at the contrary, and wiring the built chamber would be almost impossible. See for yourself : -a worker is sent up in the space above the portcullises, resting on their struts and surmounted by their heavy suspension beams (wood or granite). The worker is helped up the one cubit wide space between the leaf stones and the north wall. One cubit ? Not with your rounded beam protecting the upper door rim ! So you have to place this after the worker has climbed up, locking him in. Kind of weird ! So you'll wait until he has wired the one portcullis, let him get out, place the beam, pull the portcullis support struts away, lower the portcullis, remove the wooden beam, send the worker back in, and restart the whole procedure. Kind of complicated ! JD, if I have been the Egyptian supervisor I wouldn't permit anybody to be inside the antechamber at the moment of lowering the slabs. I already stated that, safety reasons. Everything should be workout from the inside of the GG to finally lower the slabs. After everything is set, then, they should start to lower the slabs. The process of removing my suggested front beam is easy. If the beam is supported into the drilled holes in the columns, have the men to lift the columns with the beams from the sockets and put it aside, they are not attached to the north wall. Even, the columns could be slide through the beam, to easy the job, since they are drilled holes passing from one end of the side of the column, to the other side. The rounded beam protecting the rim of the north wall could be hold in place by two wooden supports placed over the area in front of the corridor, (necessary just to hold the beam in position, there is no force applied to them.) So, removing these two supports, this half cut beam could be put aside in seconds. Why is complicate? Why is weird? Increase safety, more secured the system -what does he see once he's above the suspension beams ? Not much : where do you place a lamp ? Where is there a horizontal surface to do so ? You can lift one in the northern space. Not ideal (the worker's hands will always be in his own shadow), but it will have to do. -the rope ends are passed on through the northern space. OK. -now he's going to wire the southernmost slab, lying uncomfortably on the beams (or on a thin board brought in through the northern space). What does he see ? The south wall with the grooves. A 25 cm wide, near prismatic space between this wall and the beam. How is he going to wire the portcullis ? He pushes one end of a rope down in a wall groove. The groove extends until near the level of the crawling passage towards the KC. At one point, about 20 cm below the beam, lies the portcullis suspension hole. How is the rope going to know it has to do a 90° turn inside the groove and enter this hole ? As far as I can see, the rope is going to descend until it reaches the tapering end of the groove, and be stuck there. How about entering the rope in the opposite end of the suspension hole ? This lies more than 70 cm deep in the narrow space between the portcullises. The worker's arm doesn't reach that far (try with your own arm !). And even if he manages to push the end of the rope in the suspension hole, a 2" rope is fairly rigid and doesn't easily bend by 90°, so pushing the rope from above may not make it continue to slide into the hole 70 cm below. And when the rope comes out on the groove side, what would make it bend upwards . So it will be hard to retrieve from above. -you can try wiring the northern portcullis first, but looking at LAUER's section of the chamber, the suspension hole would be lying between the leaf and the portcullis (this would need to be checked using the real dimensions and the 20 cm distance between the top of the portcullis and the lower rim of the suspension hole, as roughly determined from Charlie RIGANO's photograph). In any case, wiring the room wouldn't be as easy as your postings seem to imply, and IMHO this isn't a logical procedure to follow. Sorry, no. There is a simple technique coming from the ancient Egyptians. Introduce first a simple thin string, stick, a papyrus tree branch, or any flexible material, attaching or tying the rope to its end, and pull. When the slabs are in the up position, the holes are only about 16 inches from the top of the wainscot. There is a 6 inches free space at the side of south slab to work, and 6 inches to both sides of the middle slab and north slabs. Do you think they are not on reach by the hands of a workingman? In case of the south slab, a hand can be extended for about 25-30 inches or more, and the space of 6 inches is enough, to introduce the hand of any normal person, for a reach of 16 inches (his hand could go about 10 inches lower than that). He can used, like a needle, a stick of wood, tree branch, or however, can be introduce through the hole to direct it through the hole and upward through the wall groove for 16 inches up. Then, the branch is pulled, having attached the rope to the end, and in a flash, you have the ropes winded through the holes. When the first slab is down, the free space is increased in one side to about 27 inches horizontally (below the 6 inches entrance), and 6 in the other, and the reach still is 16 inches. When the first two are down, the space free to work is 53 inches horizontally, over the down slabs and 6 inches to the other side. This is where I said before that if the men are able to move the center beam over the south one (using a level with the adjacent beam as fulcrum, they can even stand in top of the center portcullis slab, since there would be a cavity of approximately 21 inches width and 90 inches height. Almost the same as in front of the granite leafs. However, there is no need for that. For retrieving the ropes, there is no problem, is a matter of pulling and end out. Maybe the reason you do not see any logic is that you are somehow confused about where are the holes positioned when the slabs are up, and when they are down. Then there's your excellent idea that the south wall grooves extend up to ceiling level because the portcullis was lowered using ropes passing through its suspension holes. My calculations have also shown that the specifications for the ropes correspond with modern safety regulations for ropes to be used, not once, but some time. So I don't see what would be wrong using new ropes to lower the portcullises onto their support struts while building the chamber. Leaving these ropes in place. Wiring the chamber as new elements are added on top of the portcullises. Restraining the rope ends that need to be, placing the moving ends between the open jaws of the leaf stones. No strain on the ropes, they remain slack, no wear, no action of moisture or ultraviolet : we still found the ropes of Khufu's bark after 4600 years. The ones in the portcullises chamber would have kept well for tens of years, no problem ! All right, I agree with your opinion. You can do that if you were the Egyptian supervisor, maybe could happen nothing. I am from a different school. I prefer to work safely. I believe this is a matter of preferences. Bring me new ones, however, if the old ones are the only available, bring them up! If they break, what I have to do is change them for new ones. No problem for me, using the pulling system. That is not your case! 4. As Janine has noted, but using kinder words, your new suspension method is absurd, as the portcullis would tend to hang obliquely from one side. Considering the above, it would also be more difficult to wire the portcullises this way (think of the 180° bending of 2" rope in a narrow space ! How would you go about doing this ?). That is what many people thought about going to the moon and back. It was absurd. I know there is a moment of force created by the slab weight direction. But in my opinion it will be taken over, in conjunction with the friction, by the slabs side stones at the instant of pulling the ropes. Remember that the applied force is just the required to raise the slab several centimeters, and then the slab will be released, as I have explained in many occasions. If this were a continuous action, that's another thing. Therefore, to me, this moment of forces will have a minimal effect in the momentarily lifting of the slab for such a small distance. I think that the absurd expression, attached to a professional opinion, certifies my previous assertion of the reasons why I do not want to debate professional engineering designs in the board. I prefer to discuss, comment, and participate like other members. 5. Removing the suspension beam (and possibly using only one item, moving it and placing it above each successive portcullis) is a new and interesting concept, to keep in mind, and which may save your wiring model (although it would bring the worker's hand nearer the suspension holes, the wiring still wouldn't be that easy). (I explained already how easy it could be done). But a portcullis chamber with a huge empty space above it is quite absurd, so one should seriously consider that the beams were granite, not wood, and that there was an upper level of beams neatly filling the chamber. The only drawback is that not a single fragment of such granite drums was ever found. But even broken they may have been valuable to make stone vases during the MK, and thus be taken away and hollowed out. ---------- . but also by vertical beams (side length = space between rebates minus width of boss lifting piece, divided by number of ropes ; or even total available width minus width of boss lifting piece, divided by 12 ropes). Since these vertical "rope holders" would push against the leaf stones, they would make lifting the upper leaf more difficult. But the lever system I drew was so easy that two men could lift the upper slab. (You do not remember that I proved that your level system with the boss did not work) So here we'd put a few more to overcome the supplementary friction. The good news is this may increase the force with which the POCHAN jaw clasps the ropes ! (JD, if the struts are removed, the whole weight of the slabs will make them go immediately down, the strain suffered by the ropes as they are been stressed, will not give chance to the jaws to hold the ropes by friction. It is possible that the ropes will stretch and elongate so much (if old) that the slab is down before the action to hold arrives to the jaws. In the other way, the ropes could send an impact force to the jaws that could break the ropes. Finally. If they will be able to hold the slab, you will have, by any means, to loose the ropes to lower the slabs, something that could produce an impact into the floor slabs. Remember, this method is very different to that when you are pulling the ropes. When you pull, the rope stretches, elongates, suffer strains, until they take the pulling force. If the ropes couldn't lift the slab and broken down, you have the chance of rewiring another rope with more strength, or greater diameter. The pulling force will be applied again until the rope takes all this factors, and then, start to overcome the weight and the additional frictional forces in the system. When the pulling force overpasses these forces, the slab will start to rise. Since we only need several centimeters lift-off, the men, who are safely in the GG, can pullout of the way the two supports. These men, pulling the supports, are doing the same thing, as I explained before. They keep pulling to stress the rope and overcome the rope elongation, etc, so that when the slab is lifted, their pulling effort immediately enter into action for removing the supports. In relation to your answers to my questions, I accept that. It is your opinion and I respect that. I am sure that all members interested in the topic also have their own opinions, which I respect in the same way. However, in relation to the boss, I am more than surprised, let's say astonished, about my new findings about the antechamber and this carved object design. The same configuration that gave me a probable solution for the Great Pyramid's geometry, gave me also the probable solution for the antechamber's design. I am working on that, I will post it in the next days. It is too much interesting to let it rest in my computer. Regards, Samuel Laboy | ||
| J.D. Degreef Senior Member Username: jd_degreef Post Number: 482 Registered: 02-2000 Posted From: 213.177.158.135 |
Samuel, >I am not supposed to take into account the existing conditions and details of a structure built 5 millenniums ago to realize an structural evaluation.< Then we disagree on the basic scientific method. I look at all the clues and try to determine the intended function and mechanism (reversed engineering). You explain how you would lower portcullises, going through great lengths (portcullises hanging obliquely from their ropes, cables passing over an oblique surface -described by PETRIE as natural, not as broken, you're twisting descriptions to fit your needs-, adding a thick and heavy log which has to be placed and dismantled three times to protect a sharp rim which IMHO indicates that no ropes passed towards the GG...) to save your "king shield's" hypothesis...). >Therefore, if you can suggest that upper beams, over the upper beams, could have been used because the empty space and the existence of missing pieces invite you to, why I cannot use the same invitation?< Touché ! But the missing pieces are a fact, as is the empty space. You're using the northern empty space, which already has a function, which only you with your "king's shield" idea want to deny : to allow the use of the oblique lever against the boss. But if the upper layer of beams disturbs you, I just suggested another suspension model, where the fixed rope strand goes around and through the known suspension beams. >the builders, in many occasions used the materials at hand, if safe to used. If they need a 6 inches tree trunk, and have available one of 10 inches< The AEs were incredible misers, who controlled every little lamp wick or tool. If they used thick suspension beams, it is that they deemed them necessary, not that they just happened to be lying around ! This (and preventing the rewiring of the descended portcullises) may have made them want and retrieve the beams, which could explain the space under the roof. Unless the beams were granite. And unless the large empty space thus created would have been felt to threaten the room's efficiency. All in all I don't believe the beams were moved. >Your mechanism for bringing the heavy plugs to the level of the upper platform is neat. But where would these plugs have been stored beforehand? (I do not know it would be speculations on my part).< That's one way to test a hypothesis, consider all its implications : in this case, if you can't store them, they don't exist ! (I don't say this is the case, but the storing and the handling of such bulky and heavy plugs would be a problem in the GG. I even thought that the plug could have been used as a counterweight for the portcullises, their descent helping to haul the plug 1 m up a small ramp towards the platform, or indeed on the sledge you hypothesized. But this sounds too complicated for the time and age). >If you [JD] cannot follow my calculations, how can you follow my calculations of your work?< Physics was one of my major university classes in my time, so if you explain step by step what you're doing and why, I'll be able to follow you. On the wiring of the chamber, I of course considered the use of thinner ropes to pull the large ones. But I still don't see how you'd wire the holes near the south wall grooves... Due to the weight of the beams, I don't think they were removed to wire the blocks. >You do not remember that I proved that your lever system with the boss did not work< I acknowledged your comment about a horizontal component to the (oblique) lifting force, which would cause friction against the leaf's slide. But lubricating the slide with liquid mortar, of which traces are indeed still to be seen, may decrease this problem, and the available force on the lever on the GG side could very, very easily be increased, even tenfold ; I also proposed an easy solution to your objection concerning the splitting of the lever's wood. >JD, if the struts are removed, the whole weight of the slabs will make them go immediately down, the strain suffered by the ropes as they are been stressed, will not give chance to the jaws to hold the ropes by friction. It is possible that the ropes will stretch and elongate so much (if old) that the slab is down before the action to hold arrives to the jaws. In the other way, the ropes could send an impact force to the jaws that could break the ropes. Finally. If they will be able to hold the slab, you will have, by any means, to loose the ropes to lower the slabs, something that could produce an impact into the floor slabs.< These are interesting concepts (did you do the calculations ?) and you may very well be right. But I showed that the ropes correspond to modern safety regulations, and when I see objects dangling from cranes and bumping up and down, it gives me the impression that ropes can take quite a stress. Was it Janine who proposed wetting the ropes to make them shrink, once the POCHAN jaw had been closed ? This would put them under tension by the time the supporting struts of the portcullises were removed ? Hi Janine, >Storage of what are probably long rope ends should be above the beams< They're only long in Samuel's model, because they have to go towards the GG. In my automatic closure model, each rope must have a 2.22 strand sticking out of the POCHAN jaw in the north space. That's only six small coils, hanging from the gap between the (open) leaf stone jaw. >Control is essential, since the clearance is only thought to be about 1/4 " on either side of a 20" port. Hopefully the end clearances are at least and inch or two (E/W) in the 3" deep channels, because if one rope in one hole is released without the same tension as the rope in the other hole, the port would tend to wedge east/west.< I don't understand what you mean, could you post a little drawing ? Is 20" the width between the rebates ? >JD's idea of drilling the beams with 3½" holes may not weaken a 21" beam that much...the weak spot, at least the one that troubles me, is the knot.< Passing the rope end under the strand under tension because of the weight of the portcullis would already maintain it rather firmly. You can add any knot you want (an appeal to the sailors and yacht owners on this BB ).  I think we're slowly getting somewhere ! We have certainly booked major advances since starting this string. I wish I were a better writer, and could do a posting on the state of mind of the GP builders, on their enthusiasm, etc... This would certainly help distinguish between the meek and the audacious hypotheses ! JD | ||
| Samuel Laboy Member Username: samuellaboy Post Number: 79 Registered: 09-2002 Posted From: 209.91.201.11 |
Hi JD, normal - old posts JD & Samuel, Black and bold (now) Samuel ------------------------------ Samuel>I am not supposed to take into account the existing conditions and details of a structure built 5 millenniums ago to realize an structural evaluation. < Then we disagree on the basic scientific method. I look at all the clues and try to determine the intended function and mechanism (reversed engineering). You explain how you would lower portcullises, going through great lengths (portcullises hanging obliquely from their ropes, cables passing over an oblique surface - described by PETRIE as natural, not as broken, (I did not find where Petrie describe this oblique surface as natural) you're twisting descriptions to fit your needs-, adding a thick and heavy log which has to be placed and dismantled three times to protect a sharp rim which IMHO indicates that no ropes passed towards the GG...) to save your "king shield's" hypothesis...). JD, It seems to me, and I disagree that apparently you are evaluating me and not my method. I think that your remarks that I am twisting descriptions to fit my needs is out of order, and also that I am trying to save my "king shield's hypothesis, as you called it. I do not need to twist anything or save anything. I am just participating in the discussion giving my ideas as how to solve some construction problems. My proposal about the antechamber, although could contain many flaws, gave some light regarding its construction. The placement of the port slabs before the ceiling, the use of the south wall grooves, the placement of the wooden slabs before closing the ceiling, The winding of the ropes, the use of the GG for lowering the slabs, and many other things. I have tried by all means to answer all the questions and explain other methods that could be used, instead of my original proposal. All of that is natural, from a person that want to put some input into an apparent difficult solution. All participants are open to present their proposal, if interested. Besides, using just a sentence, not containing the complete idea, seems to disfigure my way of thinking, which would be unfair to me. I said: "I am not supposed to take into account the existing conditions and details of a structure built 5 millenniums ago to realize an structural evaluation. I am sure the ancient designer will feel very unhappy if he knows that I am bypassing all his rightly done designs, and builders work, to consider and give credit only to the trash that had been put into their work, by time, robbers, intruders, visitors, earthquakes, etc." In that way, I think would be fair. Therefore, I meant that the site should be screened from all those things that could be out of the designers, or builders intentions. >Therefore, if you can suggest that upper beams, over the upper beams, could have been used because the empty space and the existence of missing pieces invite you to, why I cannot use the same invitation? < Touché ! But the missing pieces are a fact, as is the empty space. You're using the northern empty space, which already has a function, which only you with your "king's shield" idea want to deny : to allow the use of the oblique lever against the boss. I have to deny nothing, is a matter of presenting ideas, all participant involve in this discussion have their rights to present them, and be listen. I am not obsess with the carve "boss", I am studying and researching about it, like anybody does research studies. If you do not want to discuss or mention it, that's all right. The research is mine. But if the upper layer of beams disturbs you, I just suggested another suspension model, where the fixed rope strand goes around and through the known suspension beams. I think there are to many suspension system models. However, one more is all right to me. >the builders, in many occasions used the materials at hand, if safe to used. If they need a 6 inches tree trunk, and have available one of 10 inches < The AEs were incredible misers, who controlled every little lamp wick or tool. If they used thick suspension beams, it is that they deemed them necessary, not that they just happened to be lying around ! This (and preventing the rewiring of the descended portcullises) may have made them want and retrieve the beams, which could explain the space under the roof. Unless the beams were granite. And unless the large empty space thus created would have been felt to threaten the room's efficiency. All in all I don't believe the beams were moved. I am not disturb by your proposed upper layers of beams, or if the supposed wooden beams were of granite material, that is your own idea. I think they were not. Since there is no evidence, it is a matter of opinions. >Your mechanism for bringing the heavy plugs to the level of the upper platform is neat. But where would these plugs have been stored beforehand? (I do not know it would be speculations on my part) .< That's one way to test a hypothesis, consider all its implications : in this case, if you can't store them, they don't exist ! (I don't say this is the case, but the storing and the handling of such bulky and heavy plugs would be a problem in the GG. I even thought that the plug could have been used as a counterweight for the portcullises, their descent helping to haul the plug 1 m up a small ramp towards the platform, or indeed on the sledge you hypothesized. But this sounds too complicated for the time and age). >If you [JD] cannot follow my calculations, how can you follow my calculations of your work? < Physics was one of my major university classes in my time, so if you explain step by step what you're doing and why, I'll be able to follow you. On the wiring of the chamber, I of course considered the use of thinner ropes to pull the large ones. But I still don't see how you'd wire the holes near the south wall grooves... Due to the weight of the beams, I don't think they were removed to wire the blocks. JD, the space between the beams is 6 inches. Any hand of a normal person can be introduced through this space for 16 inches reach. The south port, next to the wall, have available this space at the north side of the slab. I explained this before. You may have skipped its reading. It says: " In case of the south slab, a hand can be extended for about 25-30 inches or more, and the space of 6 inches is enough, to introduce the hand of any normal person, for a reach of 16 inches (his hand could go about 10 inches lower than that). He can used, like a needle, a stick of wood, tree branch, or however, can be introduce through the hole to direct it through the hole and upward through the wall groove for 16 inches up. Then, the branch is pulled, having attached the rope to the end, and in a flash, you have the ropes winded through the holes." I hope you clear out the location of the holes in relation to the port system."} >You do not remember that I proved that your lever system with the boss did not work< I acknowledged your comment about a horizontal component to the (oblique) lifting force, which would cause friction against the leaf's slide. But lubricating the slide with liquid mortar, of which traces are indeed still to be seen, may decrease this problem, and the available force on the lever on the GG side could very, very easily be increased, even tenfold ; I also proposed an easy solution to your objection concerning the splitting of the lever's wood. The diagram you presented to repair the broken level was so out of proportion that I did not consider it. However, if you insist, there is no problem for me, you can consider it in your proposal. >JD, if the struts are removed, the whole weight of the slabs will make them go immediately down, the strain suffered by the ropes as they are been stressed, will not give chance to the jaws to hold the ropes by friction. It is possible that the ropes will stretch and elongate so much (if old) that the slab is down before the action to hold arrives to the jaws. In the other way, the ropes could send an impact force to the jaws that could break the ropes. Finally. If they will be able to hold the slab, you will have, by any means, to loose the ropes to lower the slabs, something that could produce an impact into the floor slabs. < These are interesting concepts (did you do the calculations ?) and you may very well be right. But I showed that the ropes correspond to modern safety regulations, and when I see objects dangling from cranes and bumping up and down, it gives me the impression that ropes can take quite a stress. Was it Janine who proposed wetting the ropes to make them shrink, once the POCHAN jaw had been closed ? This would put them under tension by the time the supporting struts of the portcullises were removed ? If I understand, you wet the ropes once the Pochan jaw had been closed (JD, 20 years before been used?). How many cycles of expansion and contraction would the ropes suffered during this period, enclosed in the antechamber? If wet at the closing time, and allow to shrink, in my opinion, that will not change the extreme forces pattern developed in the system, as the struts are released. Yes, JD, we have not reached the place, but we keep walking. Every little stept helps. I guess that many Egyptologists reading these posts will better understand now the possibles mechanisms used for the antechamber's construction. And by this, we might be helping, with a small grain of sand, to the Egyptology science. Samuel Laboy | ||
| J.D. Degreef Senior Member Username: jd_degreef Post Number: 484 Registered: 02-2000 Posted From: 80.236.140.78 |
Hi Samuel,  Here's a scale drawing of the upper part of the portcullises etc., with an upper limb scanned from GRAY's Anatomy then scaled to the length of my own arm (although an Egyptian would have been shorter than I am and with a shorter arm). So the arm can indeed be stretched to reach the suspension holes. But picture the hand holding the end of a 2" rope. How rigid is such rope ? Would it be easy to bend it at right angles, to push it into the suspension hole, and with small movements make it slide through the portcullis ? But then it comes out of the hole on the opposite side and bumps into the groove in the southern wall. How are you going to make it go up so that you can grasp it ? How would using a thinner thread to pull the thick rope make your task easier ? >If I understand, you wet the ropes once the Pochan jaw had been closed (JD, 20 years before been used?).< No, not at all ! The procedure as I posted it is : -wire the room while it's being built, using the ropes that served to lower the portcullis onto their supporting struts, before the beams and roof were placed. -pass the moving ends of the ropes through the POCHAN jaw, which is kept in its open position, so as not to crush and damage the ropes during the years elapsing before the king's death. -after the funeral, close the POCHAN jaw, after having tightened the ropes as much as possible.. -possibly, wet the ropes to make them shrink (method used while placing an obelisk in Rome at the Renaissance). To which I may add : -when one knocks away the wedges between the portcullises and the struts, they won't fall out after one blow, given the load they bear. So a few knocks will be needed. At each of these, and due to the triangular section of the wedge, the portcullis is going to descend by a few millimeters. If everything has been calculated correctly by the builders, by the time the wedges drop to the floor, the portcullis will have descended to be close to the struts, but not touching them, so that they can be removed. And there will not have been a sudden jerk of the portcullis, tearing the ropes. >JD, It seems to me, and I disagree that apparently you are evaluating me and not my method.< Yes, you're right, and I apologize. But I was very disappointed about the calculation matter. JD | ||
| Samuel Laboy Member Username: samuellaboy Post Number: 80 Registered: 09-2002 Posted From: 209.91.201.141 |
Hello JD, normal type: JD & Samuel, black and bold: Samuel ------------------------------------ Here's a scale drawing of the upper part of the portcullises etc., with an upper limb scanned from GRAY's Anatomy then scaled to the length of my own arm (although an Egyptian would have been shorter than I am and with a shorter arm). So the arm can indeed be stretched to reach the suspension holes. But picture the hand holding the end of a 2" rope. How rigid is such rope ? Would it be easy to bend it at right angles, to push it into the suspension hole, and with small movements make it slide through the portcullis ? But then it comes out of the hole on the opposite side and bumps into the groove in the southern wall. How are you going to make it go up so that you can grasp it ? How would using a thinner thread to pull the thick rope make your task easier? Follow one of the two methods shown in the drawing, or both. Electricians to enter heavy cables inside electric pipes use both systems. Nowadays there is a specially design cable for this function. I think is called a fishing cable or something like that.  Notes: 1. My excuses for using your drawing for illustration. 2. There is story about a cable that needed to be crossed over the Niagara Falls to the other side. It was impossible to cross a boat because the high current velocity of the water. While they were twisting their minds about that, a young boy asked. Hey Mister, if you want, I fly my kite to the other side and drop it, tell your men in the other side to pick up the string and pull. They follow the suggestion, adding increasing sizes of string until the heavy cable was transferred. I do not know is the legend is true, but it seems interesting! >If I understand, you wet the ropes once the Pochan jaw had been closed (JD, 20 years before been used?).< No, not at all ! The procedure as I posted it is : -wire the room while it's being built, using the ropes that served to lower the portcullis onto their supporting struts, before the beams and roof were placed. -pass the moving ends of the ropes through the POCHAN jaw, which is kept in its open position, so as not to crush and damage the ropes during the years elapsing before the king's death. -after the funeral, close the POCHAN jaw, after having tightened the ropes as much as possible.. -possibly, wet the ropes to make them shrink (method used while placing an obelisk in Rome at the Renaissance). To which I may add : -when one knocks away the wedges between the portcullises and the struts, they won't fall out after one blow, given the load they bear. So a few knocks will be needed. At each of these, and due to the triangular section of the wedge, the portcullis is going to descend by a few millimeters. If everything has been calculated correctly by the builders, by the time the wedges drop to the floor, the portcullis will have descended to be close to the struts, but not touching them, so that they can be removed. And there will not have been a sudden jerk of the portcullis, tearing the ropes. All right, JD, now you have removed the struts, the portcullises are hanging from the ropes, how do you lower them to the antechamber's floor? See the simplified sketch I drew. Is that what you mean?  If you open the jaw, the portcullis slabs slam the floor, if you cut loose the ropes, the same thing. If you lower one slab at the time, you will have to open again the jaw, and place the corresponding ropes. Repeat the process again for the third slab. Since you don't want to repeat the processes, you will have to hold and release the three slabs at the time, in that case, the impact to the antechamber's floor could damage the floor, or cracked the slabs. How are you planning to slowly lower the slabs, being one at a time, or the three at the time? >JD, It seems to me, and I disagree that apparently you are evaluating me and not my method.< Yes, you're right, and I apologize. But I was very disappointed about the calculation matter. Apology accepted. Regards, Samuel Laboy | ||
| J.D. Degreef Senior Member Username: jd_degreef Post Number: 487 Registered: 02-2000 Posted From: 213.177.133.65 |
Hi Samuel, You could indeed introduce a thin rope (flexible, since it has to bend about 90° to enter the northern orifice of the suspension duct), quite a length of it. When it comes out on the other side, gravity will cause it to drop in the groove in the southern wall. So you have to go fish it up with a copper hook (the length of the wire will prevent it from slipping off the hook). Feasible, but not very easy. I still wonder why you insist upon wiring the room right before closure. Surely ropes would preserve well in the dark and dry surroundings of the room. >If you open the jaw, the portcullis slabs slam the floor< That would indeed appear to be the crux of the problem. If I have time later today, I'll try and redo the friction calculations, and see how much slowing down I can get from dynamic friction. While I calculated possible solutions to the portcullis chamber problem, I considered the two effects the crashing portcullises could have had : 1. chipping effect : I calculated the effect of the chipping tool actually used by the AEs (10 kg dolerite percussion hammer stone, estimated impact velocity 10 m/sec.) : impulsion / surface = mass x velocity / surface. The same calculation for the whole portcullis yielded a local stress of about 100,000th of that of the hammer stone. So unless my calculation was wrong, the crashing portcullises wouldn't chip the floor. Things would be more critical with the oblique suspension method which you recently advocated, since here the lower northern rim would bear the whole impact. 2. transfer of momentum, action = reaction and such things. If you build a miniature wall with sugar lumps and bang the table with your fist, this will cause the lumps to jump up and when they fall back the wall will be destroyed. Unless you put your other hand on top of the miniature wall. Then the energy of the impact will be transferred by the lumps to your hand (without the lumps moving), and be dissipated, thanks to your hand's elasticity, as heat. Now the portcullises chamber is firmly maintained by the huge pressures from the surrounding core masonry which, being rather imperfect, is also somewhat elastic. This would have to be checked with calculations (and not the kind of calculations I'm able to do), but intuitively I'd say the crashing portcullises wouldn't damage the room. But they aren't very satisfactory from a conceptual and indeed from an aesthetic point of view, I agree. JD | ||
| J.D. Degreef Senior Member Username: jd_degreef Post Number: 490 Registered: 02-2000 Posted From: 213.177.133.65 |
About the "impossibility" to lift the leaf using a lever. -drawing a parallelogram of forces, one can see that the obliquity of the lever introduces a horizontal component to the lifting force. This component, being horizontal, doesn't lift the stone. But it has to be provided by the lever. Looking at the forces parallelogram, the horizontal component seems to be about 20 % of the vertical force. This means that one must push the lever 20 % harder to lift the leaf, compared with a system where the lever would be vertical. But our lever has an amplification factor of 10-15 times, so that the increase will be less than 2 % in net force ! 2 % of 900 kgs = 18 kgs. -another consequence of the existence of a horizontal component is that it pushes the leaf against the southern rim of its slide, causing friction. How much friction ? Well, as if a mass 20 % of that of the leaf was resting on a granite surface and needed to be moved. This would mean a 20 % of 900 = 180 kg block resting on a horizontal surface. Using the lever amplification factor of 10-15, this reduces to a 12-18 kg block on a smooth surface. -total weight to bear on the workers' end of the lever : 900 / 10-15 = 60-90 kgs vertical lifting force plus 18 kgs to account for horizontal component plus 12-18 kgs to compensate for friction against the slide total : 90-126 kgs. Two or three average weight people bearing with their whole weight on the lever end thus lift the leaf ! And I didn't even use lubrication. Piece of cake, no ? JD | ||
| J.D. Degreef Senior Member Username: jd_degreef Post Number: 491 Registered: 02-2000 Posted From: 213.177.158.163 |
Hi All, Here are my no doubt long awaited calculations on the total frictional forces of the portcullises chamber.  In my model there are five friction areas : 1. rope against upper surface of suspension hole 2. rope against one quarter of perimeter of suspension beam 3. rope barely touching top of middle suspension beam (neglected) 4. rope against one quarter of perimeter of northernmost suspension beam 5. rope against two surfaces of POCHAN jaw between leaf stones. Area 1 (portcullis suspension duct) : The mechanism with one free rope end is as follows :  The rope goes through a suspension duct in the portcullis. Friction between the rope and the inner surface of the suspension duct tends to prevent the rope from moving, and thus the portcullis from descending (static friction). The formula to calculate static friction for an object lying on a surface is : smallest force necessary to start motion = friction coefficient x weight of object Of course the smallest force to start motion is a force slightly higher than the frictional force preventing motion. As an approximation, we may consider them equal. The friction coefficient depends from the physical nature of the surfaces involved. For example it will be large for rubber, so that for an object of a given weight, the smallest force necessary to start it moving will increase. For hemp rope against granite, I determined it to be about 0.85, and we can try and use this value. Let us now calculate (or at least try to ) the value of static friction (that counteracting the portcullis' tendency to descend, sliding on the rope). For the ease of calculations, I will simplify to one portcullis with the combined mass of the three (Mp), and one rope. I will also use weight (kgs) instead of force units (kgm ?). smallest force necessary to start motion = 0.85 x weight of portcullises = 0.85 Mp = 6,604.5 kgs. The force pulling the portcullises downward is their weight, Mp, which is larger than 0.85 Mp, so if it only depended upon friction in the suspension duct, the portcullis would start descending, the pulling force being 1,165.5 kgs. But we have to add the friction in the other areas, which we will now calculate. Area 2 (friction against suspension beam during quarter turn) : The problem is complicated here by the fact that we are dealing with a curved surface. Friction depends from the force with which an object presses against another, i.e. from the force component perpendicular to the surface of friction. At the point where the rope coming from the portcullis reaches the suspension beam, the whole force points downwards, and is thus parallel to the surface : no friction ! Friction will then increase as the curved surface of the portcullis nears the horizontal, and be maximum at the top of the beam, where the downward component of the force is perpendicular to the beam's surface. The rope then leaves the beam to go northwards.  The trigonometric function which describes such an increase from 0 to 1 over a 90° arc is the sine. To calculate friction on the beam, we would have to mentally decompose the rope and beam surface into an infinity of small divisions, each with its own angle of forces, kind of like the yellow arrows on the sketch. We would have to add each individual friction to find the total friction. This is called integral calculus, and is beyond this mathematical moron's possibilities. So I'll take a mean value, at 45°. Sin 45° = 0.707. Now we have to come back to our formula quantifying friction : smallest force necessary to start motion = friction coefficient x weight of object What is going to change here is the weight of the object, and for two reasons : -first of all, we have to decrease it because of the sinus factor, so M = 0.707 x Mp. -secondly, the portcullis is suspended from two rope ends, an immobile one, and the one we are looking at here. So only half the portcullis weight is supported by the rope going over the beam, it only feels the pull of half the portcullis' weight, so M = half of 0.707 x Mp = 0.35 Mp. Since we don't know what the beams were made of, we can try and keep the friction coefficient of 0.85. Thus our formula becomes : smallest force necessary to start motion = 0.85 x 0.35 Mp = 0.297 Mp = 2,307.6 kgs. Real pulling force experienced by the rope = Mp/2 = 3,885 kgs. Result 3,885 – 2,307.6 = 1,577.4 kgs (the portcullises still descend). Area 3 (rope touches intermediate portcullis) : Negligible area of contact, we will neglect its effects. Area 4 (quarter turn around northernmost portcullis) : Mirror image of the situation in area 2, but due to friction on the southern beam, the force pulling on the rope has been decreased by the time it reaches the present area. As this is the force pulling the rope, but also pressing it on the surface of the beam, causing friction, we have to take this into account, and deduct the frictional counterforce of area 2 : Effective weight of portcullis here = Mp/2 – 0.297 Mp = 0.203 Mp = 1,577.3 kgs. smallest force necessary to start motion = 0.85 x 0.203 Mp = 0.172 Mp = 1,340.7 kgs. Result : 1,577.3 – 1,340.7 = 236.6 kgs. Area 5 (rope clamped in POCHAN jaw) : As correctly indicated by Samuel, one novelty here is that we have two friction surfaces (one with the upper-, the other with the lower leaf stone). The other novelty is that the weight braking the rope is the weight of the upper leaf stone (Ml). smallest force to start motion = twice 0.85 x Ml = 1.7 x 887 = 1507.9 kgs. Conclusion : If these calculations are exact, the force pulling on the ropes by the time they have reached the POCHAN jaw is fairly small : 236 kgs. So the jaw with its frictional effect of 1,508 kgs would easily hold them. But my above calculation may contain a big mistake. When considering the force pulling on the moving rope end where it reaches the first suspension beam, I wondered what to do with friction in the portcullis suspension duct. Did it decrease the load on the rope going over the beam or not ? It seemed to me that this part of the rope didn't "know" how the portcullis was suspended to it (through individual "ears" or a suspension duct inside which the rope could slide). So I took as the basic weight hanging from this rope half that of the portcullis (since the immobile strand supports the other half of the weight). But I wonder. If the portcullis were made of rubber and the rope couldn't slide through the suspension duct, what would happen at the level of the mobile rope strand ? If it were left completely slack, the portcullis would then be suspended from the immobile strand. So friction in the suspension duct seems to influence what happens at the level of the mobile strand. If this is true, am I allowed to consider the load on this strand, as it does its quarter turn around the beam, to be decreased by the friction which occurs in the suspension hole ? An important question, for this friction accounts for a counterforce of 0.85 Mp, or 85 % of the weight of the portcullis ! Does the rope going around the beam only "feel" 15 % of the portcullis weight (or even of half its weight, the other half being supported by the immobile strand) ? Sounds unbelievable. So I'm depending upon the advice of engineers here. But in case it were true, here are the friction calculations for the whole chamber : -pull after friction in area 1 : Mp – 0.85 Mp = 0.15 Mp -pull after friction in area 2 : the preceding 0.15 Mp minus 0.707 x 0.85 x 0.15 Mp = 0.059 Mp -pull after friction in area 4 : the preceding 0.059 minus 0.707 x 0.85 x 0.059 Mp = 0.023 Mp = 182.9 kgs of pull before the POCHAN jaw. And the same calculation, if the rope around the first beam only experiences 0.85 times half the weight of the portcullises (other half supported by fixed strand) : -pull after friction in area 1 : half of 0.15 Mp = 0.075 Mp -pull after friction in area 2 : the preceding 0.075 minus 0.707 x 0.85 x 0.075 = 0.029 Mp -pull after friction in area 4 : the preceding 0.029 minus 0.707 x 0.85 x 0.029 = 0.017 Mp = 135.4 kgs of pull before the POCHAN jaw. So depending upon which calculation will be deemed correct, we have low pulls on the ropes even before the POCHAN jaw : 236, 183 or 135 kgs respectively. Astonishingly, the jaw's frictional effect of 1,508 kg is 6.38 to 11.17 times greater than this. This evokes the 5-10 / 1 ratio between static and dynamic friction. It could mean that the jaw could indeed efficiently brake the ropes even after they started moving, as Janine thought : friction would drop by a factor 5 to 10 in the portcullis-suspension system, and also by a factor 5-10 between the leaf jaws, so the ratio would remain the same, of 6-11 to 1 ! If the above ideas are right, the GP's portcullises' chamber may have been an extraordinary example of engineering, capable of closing automatically after a simple lever would have lifted a stone by a centimeter or two, then let it drop back so as to brake the passage of the ropes, thus controlling the descent of the portcullises ! JD | ||
| J.D. Degreef Senior Member Username: jd_degreef Post Number: 492 Registered: 02-2000 Posted From: 80.236.134.157 |
PS : please disregard the following sentence in the second last paragraph : This evokes the 5-10 / 1 ratio between static and dynamic friction. It could mean that the jaw could indeed efficiently brake the ropes even after they started moving, as Janine thought : friction would drop by a factor 5 to 10 in the portcullis-suspension system, and also by a factor 5-10 between the leaf jaws, so the ratio would remain the same, of 6-11 to 1 ! This was a stupid remark. I just calculated that if friction decreased fivefold when passing from static to dynamic friction (friction coefficient of 0.17 instead of 0.85), and using the middle calculation, the pull by the portcullises would jump up to 4,990.3 kgs, whereas the effect of the POCHAN jaw would decrease to 301.6 kgs ! The question which remains is : how fast does this new, dynamic friction succeed to the static friction model above, after the ropes start sliding ? Does it leave time for still high friction values to slow down the portcullises' descent ? How long before friction between the leaf stones looses its 6-11-fold advantage over the pulling force of the portcullises ? JD | ||
| Steve Brabin New member Username: steve_b Post Number: 46 Registered: 09-2002 Posted From: 62.7.119.196 |
Hi JD, Have just been through all the calculations and have the following couple of comments. I agree that this is not the place to discuss calculus, but there is a very easy way of calculating the sine calculus that you are after. Open up an Excel spreadsheet, and create a column of numbers representing the angles 1º - 90º. In the next column calculate the sine of each angle, and then just total column two and divide by 90 ! The result is 0.64 for the average of the sines. Secondly, even though I am no engineer, there must be something missing from your calculations. The size of the beam and the thickness of the rope must be relevant in the friction calculations. (Imagine a thin rope around a narrow beam, and a thick rope around a wide beam - the second case clearly has more friction.) I haven't located the answer to this yet, but the surface contact area between the rope(s) and the beam must come into the calculation somewhere surely? Best Rgds Steve B | ||
| Steve Brabin New member Username: steve_b Post Number: 47 Registered: 09-2002 Posted From: 62.7.107.254 |
Re : Friction comment in last post. I said I wasn't an engineer. Friction is apparently independent of surface area... http://www.physlink.com/Education/AskExperts/ae140.cfm Steve | ||
| J.D. Degreef Senior Member Username: jd_degreef Post Number: 494 Registered: 02-2000 Posted From: 80.236.134.159 |
Hi Steve, Before doing the calculations for my preceding long posting on this matter, I thought that the surface of contact intervened too, but then found in my old physics textbook that it didn't... So the mean sine value is 0.64 instead of 0.707 : this will decrease the remaining load before the POCHAN jaw even further. But one unknown still remains (among others, I'm sure ) : the friction coefficients. We don't even know for sure whether the suspension beams were made of wood or of granite... Thank you for going through the calculations anyhow. Which of the three calculations is the correct one, do you think ? JD |
