A Special Builder's Notes


The Special Builder's Breakfast Club

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02 October 2021

Several Wrongs....

... and then something went right.

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I approached the task of making a sprocket for the operation of the clutch with some confidence. All went well. Well, it went well to a point, and I sort of lost it linishing the various flats on the teeth. The end result wasn't the prettiest, but it looked like it was going to work. I could always make another if I wasn't happy as I had plenty of material left.

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Of course, it would have gone even better if I had measured the pitch of the chain correctly. It wasn't 12mm (and I was perfectly aware that the chain was Imperial) but 12.7mm - or ½" in old money. So I had to do it again in any case.

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The second attempt was a great improvement and I paid more careful attention to the shape of the teeth. Then came the simple job of welding the sprocket to the torque tube. I don't know what was in the steel sheet that I cut the sprockets from, but the tungsten on the TIG quickly absorbed enough contamination to become twice its thickness and parts of the weld appeared like the surface of the moon - despite proper cleaning. Then another patch would be fine. Learned Counsel thought it could be either lead or an excess of carbon in the steel. Whatever it was it certainly turned the air blue.

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I'd been struggling to find out what the nut size was on the differential pinion shaft. As far as I could tell it was 5/8"x18tpi and most likely UNC. The Riley Forum couldn't come up with the gen, so I took the plunge and ordered a bag of 5 Nylocs. They didn't fit which was a bit of a puzzle, but closer examination of the original nut that came off revealed a difference in height of the thread. I took off a couple of thou in the lathe and that solved that. The nut is still tight on the thread but taking it off again showed no signs of damage. I'll shave another of the nuts and apply some threadlock for good measure.

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I also struggled to find the right size splined shaft to go in the double UJ that makes up part of the steering linkage. The supplier had no idea what size it was and after measuring up and ordering one that was certain to be correct - it was wrong - I turned up a double-ended spigot with a flat for the pinch bolt. The geometry of the setup prevents anything self-dismantling in the unlikely event of the clamp nut and bolt coming undone.

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The steering wheel end was not quite so troublesome but threw up the problem of the Riley wheel being too big. I have a spare pattern from the A7 Special which is 1½" smaller in diameter and gives that extra bit of leg room. I'll trim down the Riley boss to accommodate the A7 wheel.

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The pedals have their cylinders connected and work well - that's the something that went right.

previous post I Have Controls.
next post Flight And Fight.


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