Monday, 6 April 2020

QR50 - Oil Tank Cap

Updated: First published March 2020

Like a few British classics, and many others the QR50 has an oil tank built into the frame spine. The filler neck was a bit bent, and I described how I straightened that in another post but I don't have the plastic cap to fill the hole. These are available, but at £15 I'm not putting my hand in my pocket, especially when I have a chunk of Acetal that I can make one from:


The Acetal is about 42 mm OD, which I bought for the fork dust excluders. It's easily sliced up on the bandsaw:


First job is to face the end:


Then I machined a 24 mm diameter to carry the O ring:


Next, I use a modified parting tool to put a groove under the cap to fit over the wider part of the filler neck:


Like this:


Next step is to put a step in the top of the cap on the lathe. I chamfered both of these steps and used a 2nd cut file and wet & dry paper to smooth the chamfer into curves that emulate the genuine part:


It fits well. I milled the finger-grips with the rotary table set up on the lathe:


Looks OK, but I used a 1/4" end mill and set the cuts at 30 degree intervals. The tool was much too large for those intervals - I should have cut a 20 degree slot with a 40 degree space, or used a much smaller cutter.


Maybe I will make another.

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