Quoth Duncan Granger:
>I thought I would pass this along, since I searched the archives
>before I tried it, and didn't find any reference to fixing or
>straightening bent crank arms.
>
>I am in the process of restoring an older (1957) English bike with a
>cottered Nicklin chainset. The drive-side arm was bent in, towards
>the frame. I removed and cleaned the chainset, and took the pedals
>off the arms.
>
>To straighten the drive side arm, I put it in a 400 degree (F) oven
>for five minutes, then with oven mitts ran it up to my shop, put the
>pedal end in the bench vice with the arm pointing straight up and
>the chainwheel at the top. I then slipped the handle from a socket
>wrench into the hole for the BB spindle, and pushed down. I had to
>put my whole weight on the thing. However, the result was that it
>actually bent back very close to straight.
Actually, there's a much easier way to do this. It helps to have an assistant.
Unscrew the pedal, lift the bike up and clamp the end of the crank into a vise (the assistant tightens the vise while you hold the bike in position) then use the bike as a lever to bend the crank back straight.
Do NOT do this with an aluminum crank, but it's reasonably safe with a steel crank.
I don't believe 400 degrees F is hot enough to make any practical difference in the malleability of a steel part.
Sheldon "Leverage" Brown
Newtonville, Massachusetts
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| There is a remedy for everything; |
| it is called death. |
| --Portuguese Proverb |
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