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Stone Shifting
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nigelswift
8112 posts

Re: Stone Shifting
Aug 25, 2003, 15:04
“The BBC built a massive ramp out of modern scaffolding”. I didn’t know that. What a cheat.

More experimenting:

I don’t know the proper engineering explanation for the pivoting/sliding thing but I guess for our purposes “the quicker it pivots, the less time it has to slide” is a good working basis. So I was thinking, there’s another way, apart from tilting the stone, to speed up the pivoting, and that is to remove a lot more of the redundant support so that instead of being about in the middle of the stone, the pivot point is well to the left of where you show it. (Obviously, you’d need to strengthen the A frame, and move the hole leftwards).

The reason I think this might be a good option is that I find there’s a downside to “fast pivoting” in that when the stone hits bottom the “new” top of it retains momentum and there’s a tendency for it to lurch forward against the far side of the hole instead of staying vertical. If the pivot point is further to the left this doesn’t happen: the pivoting speed is increased (because the right hand side of the stone is heavier) but then when the stone lands there’s less left hand/top stone to throw itself forward. It’s a bit fiddly to find, but there’s a “sweet spot” for pivoting a brick off a step, for instance, (about one third along the brick from the left) and you can get the brick to land and stay “on end” every time.

Depending on how it goes, we might find a combination of this principle together with tilting would be the answer. Either way, my messing about in the garden has convinced me this is something we ought to get dead right as we can’t do much trial and error with the “big one”. I’m wondering whether there is a universal “sweet spot” applicable to all sizes? I think lots of experiments with lots of scaled down models will give us a good feel for what’s right. I know we’re relying on the sides of the hole to guide the stone into the ground but it would be so much better if we knew that that was exactly where the stone wanted to go anyway and it wasn’t going to be exerting a lot of lateral pressure on the hole. To this end, can you remind me of the dimensions and weight of the “big one” and also the dimensions of the ten-tonner?
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