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Re: Cota 172 Restoration

Posted: Thu Sep 27, 2018 6:54 pm
by David Lahey
Have you tried a high pressure washer like a Gerni. Put truck wash on the fins until it dries then water blast.

Re: Cota 172 Restoration

Posted: Wed Nov 14, 2018 8:27 pm
by Phil 850
A bit more progress.
I removed a spoke from each wheel to see what they clean up like and they don't look too bad.
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The top one is the rear and measured up to M4 x 0.75 pitch and both the spoke and nipple threads cleaned up nicely.
However the front measured 3.2mm x 0.75 pitch which is not a standard thread of any metric description.
In imperial it might be 1/8" x 32tpi but I can't find that as a standard of any description either, and neither can my local bolt specialist.

Any ideas ?
Phil

Re: Cota 172 Restoration

Posted: Thu Nov 15, 2018 2:07 pm
by 18ss
3.2 mm equates to 10g spokes which were fairly standard on the front wheels of british bikes. Anything pre-69 will use them.

Re: Cota 172 Restoration

Posted: Thu Nov 15, 2018 9:10 pm
by Phil 850
So is there a particular designation for a 10g thread so I know what to ask for to buy a tap and die ?

Re: Cota 172 Restoration

Posted: Sat Nov 17, 2018 7:40 pm
by 18ss
Not that I can find. A 10g spoke should be 40 tpi. If the thread gauge says 32 tpi a unc 32tpi no.6 may do. As you stated there is no metric equivalent that would work. I would probably try, if the threads were too rough a 32tpi thread file or if they are just crudded a touch of fine valve grinding paste and screw the nipple up and down a few times.

Re: Cota 172 Restoration

Posted: Sat Nov 17, 2018 9:48 pm
by Phil 850
Thanks for the info.
It's mainly the thread in the nipples where spokes finished the thread is a bit rusty and I'd like to clean them out before I reassemble them.

Re: Cota 172 Restoration

Posted: Sun Nov 18, 2018 10:23 pm
by David Lahey
If you can find a spare spoke with the right thread, make your own tap from it by cutting flutes into it.

If the crud in the nipple is rust you can dissolve the rust with phosphoric acid then if you want it to look fancy, re-plate the nipple (aid will remove zinc plating).
I've done the acid treatment on two complete sets of steel spokes and nipples because they were otherwise perfectly good.

Re: Cota 172 Restoration

Posted: Mon Nov 19, 2018 9:03 pm
by Phil 850
What did you do about replating the spokes and nipples ?

Re: Cota 172 Restoration

Posted: Mon Nov 19, 2018 9:05 pm
by Phil 850
Fully stripped the rear wheel.
Now do I polish the hub or leave it the original satin :|
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Re: Cota 172 Restoration

Posted: Mon Nov 19, 2018 10:10 pm
by David Lahey
Phil 850 wrote:What did you do about replating the spokes and nipples ?

I couldn't be bothered setting up the plating kit to zinc-plate them, but I did paint them before reassembling the wheel. About 10 years after that, replacement (plated) spokes became available for a reasonable cost and then when I next machined the brake drums, I fitted the new spokes.