Looking for a wide one piece crank

[mat_man]

Re: Modify one piece crank (Re: Looking for a wide one piece crank)

How much heat would one have to apply to a one piece crank to do this?

Some do without heat:

Cold bending 1 piece cranks?
http://motorbicycling.com/showthread.php?t=35923

 

[jbcruisin]

With what kind of torch?

oxygen & acetylene

 

[dracothered]

oxygen & acetylene

Oxygen & Map gas might work also I would think.

 

[DTFuqua]

Yea, my cutting torch setup uses butane/propane and oxygen. Been using that setup for over 20 years. Just wish my son would bring it back to me so I can use it now.

 

[atombikes]

I use a Bernzomatic model JTH7 torch for my mapp only bicycle brazing. It is what they call a swirl head, it uses no oxygen, but has a rather large tip on it. Has a 3 ft hose so you can invert the torch (and you can put the mapp bottle in a bucket of hot water for more pressure)...

I think the logic is that air will mix with the mapp as it is being burned. Anyway, I have been able to heat up and braze dropouts and bottom brackets with this torch. But I wonder if it will also have enough heat for this job? Guess I will find out in a month or two when I am ready for this step.

 

[DTFuqua]

I think the torch I bought is about the same thing but without the hose. Just mounts to the top of the bottle. It did get mine hot enough to bend with a little effort. I used the bike frame to hold the crank while I did the bending just so I'd be sure I bent them enough to clear and rotate. I took everything apart and cleaned and re-greased the bearings after doing this. I'll have to redo it someday to make them wide enough to keep my ankle from getting too close to the drive belt and pulley but I got them wide enough to use with care for now.