I think that we should be able to get rid of some of the variables.

The height of the uprights at Stonehenge varies. The outer circle is fairly constant, I`ve seen figures of between 13.5 - 16 ft for its height above ground. The inner horseshoe was higher, up to 22 ft. I presume that we`d be going for the lowest figure. I don`t know how deep the stones were set into the ground.

By depth, do you mean width? The width of the stone dragging on the tower? Or is that irrelevant once you know the coefficient of friction?

The figures that I`ve got are 7 ft wide and 3.75 ft deep for the outer uprights, with weight of 25-30 tons.

Can you tell me what the offset variable relates to, please? I don`t understand that one.

baz