Re: Do we need ropes? | Forum — The Modern Antiquarian

Steve Gray Sep 16, 2003 17:37:42

Replying to GordonP

I'm not very happy about levering off the tower. It's one thing to use an unjointed tower structure to raise a deadweight, but quite another to apply massive side loads to it. These side loads are likely to be in the region of 7 tons at a height of 24 feet. I've said this before, but that's one hell of a torque. In order to counter that torque we would need some very long (70-100 foot) diagonal bracing poles against the tower, or guy ropes in the opposite direction, or both.

I'm also not sure that I agree about their lack of knowledge of gearing (I prefer the term "mechanical advantage" because gearing implies cogs and things). They already knew about using levers to attain a mechanical advantage. I could imagine that someone pulling on a rope might have thought to wrap it around a long branch, stick the end of the branch into a hole in the ground and then pull on the top to get extra leverage. An A-frame is not much more. In fact the job of an A-frame can be done with a single pole provided that tether ropes are attached on each side to stop it falling sideways.

I'm not arguing for one method over any other, but I think we shouldn't exclude any avenue of research that MAY end up being needed.

Steve Gray Sep 16, 2003 18:09:32

Replying to Steve Gray

Hey, I think I've just had a brainwave.

Suppose we made a long rectangular frame of logs that can be dug into the ground so that it will lean against the back of the 70deg stone near the top like a shore. Levers attached to the top edge of the frame would make contact with the stone and would stick up above it. Ropes from the levers would then be pulled causing the stone to be raised a little. Packing would be rammed into the hole behind the stone and then the rope pullers would relax. When they did, the frame would drop a little to take up the new position of the stone and the process can be repeated.

The redcution in mechanical advantage caused by the frame moving lower on the stone will be compensated for by the fact that the leverage required to raise the stone becomes less as the stone gets more upright.

GordonP Sep 16, 2003 18:12:57

Replying to Steve Gray

Still thinking of levering at 90 degrees to the braceing strutts, (surely that must half the pressure) also trying the bracing strutts again at an angle of 90 degrees to the lintel placed at the other side of the upright. No need to take the ropes under the upright, just under the lintel.

Stone shifting 5