Old Automation Phase 3 – Roof

The third phase of the automation project is the roof. Not only does it need power, it needs to roll very smoothly to ensure the motors don't stall when opening and closing the roof. So this element will probably take the longest to complete...

18th November 2016

Some real progress with the roof! After inspection and measuring, I deduced that I could mount the sprocket and chain in between the main runner and the outside edge of the roof - i.e. in the same gap that the wheels will live. I also settled on some galvenised steel V-track and matching wheels from FH Brundle. After some careful measuring, I needed to rebuild the horizontal section of the roof runners to allow enough room for the wheels and sprockets to fit in, and to support the track

So, having ordered the track and wheels, I set to....

I lifted the roof clear of the runners so I could access the wheels.
I stripped off the original 22mm thick wood that was used to build up the platform for the wheels to run on. I replaced them with 47mm wood to give more width to allow the steel track to fit
Showing the first side has had both pieces of 47mm baton installed and bolted into place
The same was done on the left hand side. After taking this image, I actually stripped the wood off as it was actually quite warped. A new piece was cut and installed
A coat of the green preserver was applied
Here the original wheels can be seen. They are made up of two plastic wheels, slid onto a bolt and separated by a washer.
The shiny new ones! Stainless steel 80mm, rated at 300kg, with an M14 bolt and a bearing either side
I hade made the assumption that installing the new wheels so the bottom was flush with the bottom of the roof outer edge, there would be enough clearance when the wheel sat on the track. As can be seen, this was not the case! The outer edge sat perfectly onto the horizontal runner - there was no way that was going to roll!
So, new holes were drilled to allow the wheels to hang below the outer edges. The original holes will be filled with a strong wood repairer - the sort of stuff that hardens rotten wood,
The first part of the roof remodelling is now complete. The roof rolls better than it did, but now the track needs shimming to ensure perfect level

I now have to ensure the track is levelled, so I have purchased some packs of steel shim for this. I need to get the roof off again in order to do this. Ideally, I;d like to take it off completely to give clear access - but that will need some strong assistants and somewhere to support the roof while I do the shimming!

I am also a little concerned about the weight still... It is a very heavy roof and while it does roll OK, I worry that even with a level track, it will be too much for 12v motors. Either It will end up with mains powered ones, or I may even rebuild the roof completely to be much lighter. Either way, the track needs levelling!

19th October 2016

I have been mulling over the mechanics of motorising the roof and what to do about getting the roof rolling smoother than a smooth thing from the planet Smooth... This thread on SGL has put me on the right track (ha! see what I did there??) so now I need to check dimensions of the track from the supplier and get it ordered

The actual moving of the roof is another matter. I am not an engineer so it takes me a while to work things out and visual things, but I eventually came up with the idea of:

  • Mount the motors on the underside of the roof
  • On top of the two horizontal beams, attach nylon chain and affix by using some form of staple
  • The motor sprockets then mate with the chain to drive the roof forwards or backwards

After discussing with Steve Richards (thanks again Steve!), we concluded this was not an ideal solution as the sprocket would probably not mate correctly with the chain because the staples would be in the way. Steve then kindly revised my idea to have the motors fixed on the rear wall of the observatory, a sprocket at the far end of the roof and a chain that is fixed at one single point to the roof.

On closer inspection of the roof, however, I am not sure this will actually be possible. There is insufficient clearance between the top of the pent roof section and the bottom of the sliding section to allow the chain to run. It might be possible to mount it on the outside though, to the underside of the external vertical beam - I will look at this in a bit of detail over the next couple of weeks

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