Declination drive metalwork Pt.2.

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I spent the afternoon making a new motor plate and main support plate for the declination axis in 10mm aluminium. I was rather too generous with the length of the main plate and found the 11" RA wormwheel was obstructed. Cutting the main plate 10mm shorter solved the problem but meant another dismantling of the just rebuilt declination axis housing. Apart from the four main studs there are lots of cross studs to loosen before the axis flange bearing will slide free.

The images show progress on the Declination drive assembly.  Despite the offset shafts there will still have to be a belt tension pulley or roller like the RA drive.

I use cheap, electroplated, cross-head screws for assembly during the construction and fitting stage. The stainless steel, socket head screws and stainless Nyloc nuts are only used once the assembly is finished. It is easier to twirl a cross-head screwdriver than a hex wrench. The problem with cheap fasteners is that they rust so readily. The electroplating is only good enough for bubble pack displays, in a warm, dry, indoor climate before it starts rusting. Once rusted, they are hard to dismantle.

Stainless steel screws are relatively inexpensive when bought from small, online specialists. They remain as bright as they day they were bought. There is nothing more depressing than seeing rusty fixings on a mounting or a bicycle! It is inexcusable penny pinching to use anything but stainless steel these days.

Again I have notched the Declination motor plate to clear the wormwheel. The top of the plate will be shortened last. Making the large holes in the motor plate with hole saws is a very time consuming business. I ended up using the lathe in the slowest back gear @ 45rpm. With the tailstock pushing a small board behind the motor plate for the feed. The new pillar drill suffered from frequent belt slip in bottom gear when using hole saws. Larger drive pulleys made the saws run too fast. It might be a better idea to drill a ring of small holes on the saw line first to speed things up.

I shall have to buy some new 16mm galvanized studs for the Polar Axis housing. I had simply cut the original meter lengths in half when I first started the project. The polar axis eventually ended up shorter than the declination housing. Adding the 10mm base plate made the studs too short for comfort. The large, brass, domed nuts use up a lot more thread length than standard nuts. I could revert to using 16mm stainless steel nuts but prefer the rust prone ends of the studs to be suitably covered.

Factored in with the total cost of the mounting then four new studs are hardly going to break the bank. Any commercial Goto mounting with the weight carrying capacity of my build would cost many thousands of pounds or dollars. Though most amateurs would probably not want the heavy mounting I have built. That is simply a matter of taste. I didn't have the funds to buy a large commercial mounting. So I did what I usually do. I built my own to my own tastes and needs within my far more modest budget. I do not set myself the very high cosmetic standards demanded of commercial mountings. Having worked in CNC production I know the difficulties of maintaining perfection with bored and careless workers.

Unless I paint the mounting the aluminium will suffer from surface deterioration anyway. Scotchbrite red-brown, abrasive fiber is one way to get and keep a reasonable finish on bare aluminium. Hammerite enamel seemed to last for a few years on the aluminium castings of my old Fullerscope's MkIV mounting kept outside under a tarpaulin. Ventilation is a good idea to rid the mounting of the inevitable condensation and dew between uses. Birds must be kept out or they will readily nest in there!

Click on any image for an enlargement.

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