30.03.19 Focuser motor mount & solar

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I have been thinking [and even dreaming] about focuser motor mounts. Mostly thinking about how to make one. The early plan was to drill a rectangle to 28mm to clamp onto the pinion housing once the support is cross-drilled and then sawn in half. The size is actually 28.5  but hole saws usually produce an oversize, clearance hole. So I'll need to source a hole saw in 28mm.

The rectangle could just as easily be made from two strips, clamped firmly together and then drilled.

Bare aluminium wouldn't be very kind to the focuser's pinion housing without some sort of packing material. So why use aluminium? Clear polycarbonate is tough enough for the task of supporting a little, electric motor. Plastic is easily machined and won't mar aluminium. It can look quite attractive if smoothed and polished on a buffing wheel. It's very transparency will make it fade into the background. Allowing the focuser and motor to become one. As if always intended to be that way.

I have some Tufnol sheet but it's a bit smelly and goes on being smelly for some time after being machined. I don't really want something smelly close to my face. Not while I'm looking through an eyepiece for extended periods. It may even be toxic?

Brass is traditional for telescopes but will mar aluminium if there is relative movement. Or even chemical attack from moisture ingress at the joint? No real advantage over aluminium, it is harder to work and it discolours over time, even when lacquered.

I have some sheet Teflon/PTFE but can't see the advantage of using that. It's snowy whiteness will only draw the eye to dominate well beyond its allotted task.

I'd better start a search for some polycarbonate offcuts. I have some buried in the detritus of the workshop. Just waiting patiently to be to be made into a prototype. I'm bound to think of a better way of doing it once I've actually have something to play with.

Further, careful examination of the bright section of the pinion housing suggests it is most likely stainless steel. It is thus not nearly so likely to be marred as aluminium might be. Presumably this material was chosen so that commercial focuser motors did not spoil the focuser cosmetically. 

Having looked at the motor support problem I can get away with a 50x40x8mm rectangle. No need for hinges or pins. I'll just use two clamping screws. One above and one below the 28.5mm hole. Then saw the rectangle in half lengthways and smooth the cut surfaces. I may radius the bottom edge to avoid corner contact with the focuser as it is twisted around the pinion housing.

The motor's own plate will be attached at right angles to one of the separated clamping strips. This gives me the option to adjust belt tension by rotation of the whole assembly around the pinion housing. While I have a whole range of woodworking and metal drills and a few hole saws I don't have a 28mm. Which means progress must wait until I reach a DIY outlet tomorrow.

As usual I have talked this simple job to death. It is just my way of seeing if I can come up with better ideas.   

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