[pmrid (Peter)]

TenChain Hill Obs has a 4 x 5 metre roof that rolls off on to the west. The existing bottom rails (50x50 box section 11 metres long have 15 Bunnings rollers per side and the roof is centred by sections of 50mm angle iron on the outside of both top rails. That was fine for a while but we have had an extended wet and this means too much time to think and re-invent the wheel.
So now we are well under way with the "New" roof system.
This time, the rollers will be attached to the roof and not the bottom rail - it'll keep them out of the weather. And the rollers are in fact pulleys with high-precision bearings in them and there will be ten to the side.
The bottom rail will be 50x50 square section with a vertical flat bar rail running the full 11 metre length and the pulleys will roll along this bar. The pulleys each have a side-pushing spring so the pulleys will be self-centering and will be able to handle a bit of deviation as it rolls out and back.
The attached photo shows the upper sections with pulleys fixed in place and a couple of sections of the bottom sections with the flat-bar rail.
All going well, I ought to be able to move the roof by hand without blowing a valve every time, or throwing my back out. And the boat winch I use occasionally will not have to suffer a hernia every time.
Next step is to get the rails in place. That'll be fun.

Peter