Bent Hanger Repair
 

Hi,

I would be grateful for your thoughts. A friend has called with an old Pearson frame in 531 tubing. It has been in a smash and has what has been described as a badly bent rear mech hanger. The local bike shop are not interested in attempting a fix stating that it is 50/50 whether or not it will shear if they bend it cold, they advise heating it up. I have oxy/acet, dropout alignment handles and mech alignment tool.
I am looking for any tips on how hot to get it or any other basic info that will give the repair the best chance of long term success.

Thanks in advance

Welcome to BikeForums.

I suspect the lack of responses is because there's not enough information provided to offer advice. What kind of rear dropouts does the bike have? Can you provide photos showing how badly the hanger is mangled?

I don't know that bending steel while it is hot really avoids damage. I don't think it is any better. I would probably bend it back cold

Thanks folks for the input and the welcome. I will try and get a photo when the bikes delivered, I was trying to get a little info in advance.
From what I can gather from the bikes age the dropouts will be either a standard steel vertical dropout with mech hanger integrated or a more traditional forward facing sliding drop with hanger. So defo steel and with the dropout and hanger as one piece.
To be more specific I am more after metallurgy advice such as will heat be useful or as unterhausen suggests there will be no benefit.

Cheers

If it's a fairly common dropout like the Campagnolo 1010 or 1010/A (no eyelets), and low temperature silver brazing filler was used, it might be easier and safer to have a framebuilder simply remove the dropout with the bent hanger and replace it with a new one since they are still readily available and are relatively inexpensive.

http://i32.photobucket.com/albums/d7...ps0f4dab49.jpg

http://i32.photobucket.com/albums/d7...ps5c897d0a.jpg

Most will consider aligning a hanger when cold. Only when extreme situations exist would I use heat. Andy.

Thanks again for the input. Ok I have a good idea of what to do. If the damage is slight/moderate, then align cold as there seems no benefit to adding heat. If the twist is pretty serious I will replace. I figure this is best done by bisecting the old dropout thereby reducing the amount of heat necessary to sweat out the old tabs individually. Then clean up and replace.

BTW I just found this forum, seems I missed it for some time. Good to see your name pop up Andy. I remember you from various incarnations of different frame forums. Always reliable and helpful info. Cheers.

BTW I just found this forum, seems I missed it for some time. Good to see your name pop up Andy. I remember you from various incarnations of different frame forums. Always reliable and helpful info. Cheers.[/QUOTE]

Thanks, it's hard to teach this old dog new tricks. Andy.

steel doesn't anneal well .. you form it hot .. higher than the melting point of brass .. red-orange-yellow Hot

you may try taking it to a bike shop if not too bent , [sounds like you bought that tool]

the same beam tool that screws into the dropout to fine tune the allignment will also bend it back into place if not too far gone..

Like a fall over on the right side, bend..

other than that, saw it in half , so then you melt the brass in each tube, 1 At a time, and pull the halves out while the brass is molten .