19.01.2021 Ring template arcs and RA drive.

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Tuesday 19th: A grey, damp day. I trimmed the ends of the arcs with the jig saw. Then cleaned up the cut edges with the mini router against a straight edge. Far too wet to lay them out on the ground to check their accuracy. Heavy rain forecast for tomorrow. After thick mist overnight. 

Wednesday 20th: Rain and wind. The hole saws have turned up today. Now I can finish the reinforced RA drive motor/worm assembly. It is no use having a massive mounting, capable of carrying heavy loads, if the drives don't match in performance. 

I had grossly underestimated the weakness of the Beacon Hill worm housings and bearings. It wasn't until I started looking at up-market, commercial mountings that I realised the best had one thing in common. The worm was housed in a boxy casting with very high, inherent stiffness. NOT in a cheap and flimsy, channel section, aluminium off-cut. Barely wide enough to house the plain, ball bearing races!  

The 26mm hole saw produced a nearly 28mm hole. I had a carrier with the correct thread but the hole saw swiftly became eccentric in the hole. This, despite my drilling a pilot hole just undersized. Fortunately the bearing wouldn't enter the hole. So it will be safely restrained against linear movement. Which would otherwise cause backlash. I also need to apply end loading on the angular contact bearings. 

After lunch I shall reduce the boss on the larger pulley in the lathe to ensure clearance. Sawing out the motor & worm plate from the scrap section would be easier and more accurate on the mitre saw. Except for six, 5' x 5' sheets of plywood leaning against that same saw! It looks like being the jig saw which gets the task. And did. 

A coarse toothed, DeWalt metal blade went through the 10mm aluminium plate quite quickly. I put a few drops of lamp oil in the cuts. The drive unit went together smoothly once I had reduced the large pulley hub to 25mm. Now I just need to tidy up and refit the stainless steel, socket head screws and Nyloc nuts.  

As of yesterday, Google Blogspot has suddenly lost its quick edit button. I am not alone! Added to the newly created farce in trying to edit text around and when moving images, one must assume internal, evil intent. Obscenely overpaid, new broom? Working several floors above their qualifications for the task? 

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