(Should we use descriptive titles for sub threads, as I’m finding it hard to refer back?)

Am I right that Steve’s idea is to have a pivoting log fixed transversely across the underside of the stone, so whilst the stone rotates from horizontal to vertical the pivot log effectively rolls through 45%?

If so, lots of questions occur to me, including some possible dangers to be considered:

It’ll take a bit of computing because, as well as pivoting, the stone is following the curve of the log and moving through a small arc, which it wasn’t before.

I guess physical positioning of the pivot log on the edge of the tower needs to be extremely accurate i.e. the computer model may predict it’ll end up vertical but if it’s physically placed 4% off from the edge of the tower that’ll translate into the stone ending up 4% off vertical, maybe more.

Also, what form is the edge of the tower? Is it square or is it another log? If the latter, can we place the stone pivot log exactly on top of the tower pivot log, along their whole lengths and will the one effectively roll round the other, uniformly?