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Classic Lightweights UK
Restoration  
 

Repairing a frame with stripped bottom-bracket

Bill Ives
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I have recently had to restore a Saxon frame with stripped bracket threads by installing a Bayliss Wiley Bracket Unit.  These units, which are very useful for this repair job, still come up for sale from time to time. They were used in the post-war years by builders such as Paris/Rensch who built some of their frames with this bottom bracket as standard. On welded and bi-laminated frames there was no need for the heavy bottom bracket shell as a simple tube could be welded in.

Reaming the bracket was a pig of a job for although it's easy enough to ream a plain tube a bottom bracket has steps in diameter where the threads are plus the five holes where the frame tubes and chainstays enter.  There is also the hole for the bottom bracket grease nipple but this is so small as to make little difference.

The Saxon uses a cast bracket which tapers quite a bit towards the outside so reaming left it very thin at the edges. To counter this and increase the strength I turned up two re-inforcing rings and brazed them on.

I built one of the rings with ears which engage with the flats on the fixed cup of the unit bottom bracket.


The reaming was done with an adjustable reamer used from  1 11/32" to 1½"



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Bottom bracket before repair with the shell of the unit hub and the two strengthening rings
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View if the bottom bracket after the repair showing the 'wings'  engaged with the flats on the cup

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The rings brazed on and 'fairing-in' done with the brazing metal
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Side view showing more 'fairing' and the reamed inside of the bracket - now minus threads

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The 'pig of a job' in progress