Broke the third crank mechanism! The dome is just too heavy! I wore out two round holes for a crank handle into oblong holes in just a few complete rotations. Two 1/2 inch holes through mild steel rhs turned into 1/2 inch by 1 inch oblongs.
So now i have built a SUPER CRANK MECHANISM out of two 25mm roller bearings side by side. I'll be getting Ron to put it on the site for me, on the support ring page.
Until then, heres a couple of pics.