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Stone Shifting 3

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GordonP G
GordonP Sep 2, 2003 18:04:45
Replying to Steve Gray

Hi Steve
Yes I know notching the logs would be time consuming but all this can be done before the event. If we use logs with an average diameter of say 6in and reduce the notched part to 4in, that is to say we take a bit off each side of the log just at the notched point we end up with a square section joint. If we make this joint loose enough to accomadate any of the logs we can tighten the loose joints with flying wedges. this would enable us to biuld the tower very quickly and the weight of the stone would hold it all together.

We can use the weight of the stone another way too. As we erect the tower when the need arises we can create platforms around the tower by inserting logs into the tower to form a canterlever platform complete with guard rails if necessary.

I'm still convinenced the stones were launched from the sloping side. I've been studying the film of the 4 ton experiment. At the time I didn't know about the sloping side of the hole, so dug my hole with four virtical sides but made it overbig just to be on the safe side. As the stone entered the hole at less than vertical the inside face of the stone catches the inside face of the hole stopping the stones rotation.

S Steve Gray
Steve Gray Sep 2, 2003 22:33:58
Replying to GordonP

I had imagined that the overlap points of the logs would all be beneath the stone. That way there is no bending load on any of the logs and we rely entirely on the compressive strength of the timber, which is considerable and gives us a good safety margin. If we don't do this I would find it hard to provide convincing stress calculations unless we used stress graded timber (for which bending moments are known) and violate our historical integrity.

If the laps are all beneath the stone, I don't think we need proper joints. The logs cannot carry such a load on round surfaces without deforming into flattened contact areas, but if you really feel it is necessary, you could cut notches that have a 4" square bearing surface and a sloping shoulder on all 4 sides of the square. The slopes on the top of the log would go upwards whereas the slopes on the sides of the log would go down. As long as the angle is the same, all timbers will fit together perfectly regardless of the size of the log.