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Fixed my hemiatrophic Girardengo...

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Fixed my hemiatrophic Girardengo...

Old 06-01-23, 08:27 AM
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Fixed my hemiatrophic Girardengo...

A while ago I thought this bike was finished - but when the front wheel went in it was tilted to one side.

Careful measuring showed that it had been built wrong - the top of one dropout slot was about 2mm closer to the top of its side of the fork crown.

I didn't want to file the longer dropout, in case I got it wrong and went too far.
Instead made made a bit to fill in the dropout slot in the shorter leg.
That way a too-much error wouldn't hurt the bike.

I turned a bit of brass rod to a sort of bobbin-shape, central diameter the same as a front axle and width of the flanges so it would just centre in the slot.
That bit got cut in half and glued into the slot with cyanoacrylate.
I drilled a 2.5mm hole through the glued-in-bit into the dropout, then tapped the bit-plus-dropout m3x0.5 - I tapped the brass even though I wouldn't need threads there later, just wanted to make sure the tap went straight.
After that I turned the edge off a countersunk M3 screw and drilled a clearance hole for the now-smaller head in the brass section.
I cut the screw to length and put it in, and then the careful work started - filiing the D-shape to just the right size C shape such that a wheel would centre properly.
After that the flanges got filed off, leaving just the necessary crescent.

D-shape and screw:



Drilled and tapped - the blotch on the brass at the bottom is excess glue:



Screwed and the C-shape filed:





Flanges filed off:


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Old 06-01-23, 10:20 AM
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Originally Posted by oneclick
A while ago I thought this bike was finished - but when the front wheel went in it was tilted to one side. Careful measuring showed that it had been built wrong - the top of one dropout slot was about 2mm closer to the top of its side of the fork crown.
Were it a track bike, I'd wonder if built that way on purpose to aid on turn-in to one side, like tire stagger on a stock-car racer.
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Old 06-01-23, 11:02 AM
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I've known people to use a bit of JB-Weld in a fork dropout slot, easy enough to file-to-fit after it hardens, and very tough stuff.
The dynamic load in use is taken by the grip of the locknut as opposed to the end of the axle.

Drilling/tapping is one's own experiment as far as "endurance testing" into the future, same as with any modification to metal parts.

I've seen a few frames over the years having unequal "effective lengths" at the fork or at the seatstays, and I find it annoying, but might be one of the reasons why I found myself able to buy at a good price (infinitely better than buying a stolen bike).
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Old 06-01-23, 11:43 AM
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