Cracked Ali headtube

[mattg]

Hello.
Im looking for advice on patching an aluminium headtube on a bike. It has an inch crack from the bottom upwards and an inch crack from the top downwards. Not having access to TIG, and not having much respect for the looks of the end product, I plan to cut a steel tube in half and then weld it back together around the damaged area. This should stop it totally failing...hopefully.
Any comments?
matt

 

[shenion]

I woudl find someone with a TIG to fix it or look for a new frame off ebay.

 

[Pete.]

Hello.
Im looking for advice on patching an aluminium headtube on a bike. It has an inch crack from the bottom upwards and an inch crack from the top downwards. Not having access to TIG, and not having much respect for the looks of the end product, I plan to cut a steel tube in half and then weld it back together around the damaged area. This should stop it totally failing...hopefully.
Any comments?
matt

Is this a bicycle or motorcycle?

 

[mattg]

sorry its a bicycle- just a fairly standard mountain bike which I would like to use to pull a trailer. As the bike was free, Id rather not pay someone to TIG weld it- it will probably crack elsewhere at some point as well and it would be good to be able to fix it myself. thanks, matt

 

[hotrodder]

If the headtubes cracked the headset bearing races are probably now a loose fit (may well have been hamfisted attempts at pressing 'em in that initiated the crack in the first place). With the forces going on that area (braking etc) the cracks will just continue to grow under a sleeve.

No doubt you could bodge it up for a few weeks/months of use, a piece of accuratly sized tube that was a shrink fit over the ends of the headtube might work for a while but because of the cross and down tubes it will be so small that i would think it will ovalise after not long. I would have thought you'd be able to find someone to weld it for a drink.

 

[Sam]

If you are not too tight to use petrol come down and I will weld it for you foc. or you could always cycle!!!

 

[MrFluffy]

be sure to drill a small pinhole at the end of the two cracks to stop them propogating further before any repair is done...

 

[chunkolini]

I think with a cracked headtube it is a dead bike, if it were to fail it could get messy.
I bet you could find another frame or a whole bike by asking around.
Chunko'.

 

[Alfaman]

I think with a cracked headtube it is a dead bike, if it were to fail it could get messy.

Agree, and I speak from experience!

I reckon the steel tube 'fix' might work for a short while, but it's not something I have tried, nor would trust. I have my doubts.

What would work is if you could get hold of a scrapped frame (made of the same ali) with a good headstock, and make one good one out of the two. Maybe not ideal if you don't have access to TIG.

 

[chunkolini]

Not even safe then. a lot of aluminium frames are heat treated after welding to relieve stresses etc.
Bin it, or leave it outside the pub for a bike thief to find......

Chunko'.

 

[Alfaman]

heat treated after welding to relieve stresses etc.

True, depends on the spec tho'

What would happed if the existing cracks were tig'd, would the heat treatment need repeated?

 

[Alfaman]

Although having re-read the OP's comments:

it will probably crack elsewhere at some point as well

i would tend to go with chunkolini's 'Bin it.....' suggestion!

 

[toddy]

well my point is if there is any cracks in a bike to bin it. but thin this is comming from some one who riped out a ti part of a frame once.
if you are really not wanting to spend much at all i have got a giant frame that i have been meaning to put in my shop, you can have it for £10 +pp(so about £17)
if you are interedted pm me

 

[NTwoO]

Some bikes are 6000 series alu and some are 7000 series alu. This will affect the ability to repair it. Stopping cracks by drilling requires at least a 6mm hole and is not the practice for structural components. The general policy I was brought up with is "will you step into it if it was an aeroplane" if the answer is no, then don't do it with a car or bicycle.