spent one afternoon and two evenings to modernize the bottom bracket (BB).
Thomson BB with 'all steel' chainwheel and 'wedge axle' crank arms
original part was a Thomson type BB with wedge
mentioned, the crank arms were rusted and too heavy also. I decided to dismantle
the crank arms and the BB completely.
The BB shall be replaced by a semi-modern square taper version.
Wedge axles are odd to square taper crank arms
Sturdy frame: All the residues on it were dirt and oil - no rust
bottom bracket, which was to small
shall read the description of the offer:
"... not for replacement of 40mm Thomson bottom brackets." Silly, I am.
Wrong diameter = too small!
By searching the internet I found this: THUN-BB-40mm, but, alas, it´s out of stock. I haven´t found any similar part.
The second best solution would be the purchase of a Sunrace 40mm press-fit bottom bracket which theoretically shall fit.
does *not* fit!
polish frame builder has hollow turned the inner area just to fit in
the Thomson bearing shells. The nylon shells for the new bottom
bracket are more
and the press-fit got blocked.
spent five hours grinding off the metal inside
make it sort of fit
Grinding excess metal inside the BB housing
Cutting away excess plastics from press-fit bushing
Finally, after hours of trial and error, it fits in
better solution would
to make turned parts from stainless steel to
the formely purchased, screwable
bottom bracket into the frame,
but I don't know anyone with a lathe to ask for.
Result: The press-fit bottom bracket is mounted. The time will show how durable this imperfect solution is.
Next chapter: The chain wheel, Part 1