Possible to modify a TIG welded frame?

[saab2000]

I was just wondering if it is possible to modify a TIG welded frame? If, for example, a bike had a top tube which was too long, could it be shortened? Could the head tube be cut off and have the top and down tubes shortened and have the head tube re-welded?

Stupid question, I know. Just curious.

[cpg]

Yes.

Curt

[NateM]

If you shortened the top and down tube and then replaced the headtube (headtube would be longer) wouldn't the crown height of fork be lower as well(effectively shortening the span of fork)? The original fork would jack up the front end changing angles in process. With carbon forks this might be hard to deal with? Please explain.

[Kevan]

maybe not. Depends on the butting of the pipe. I'd also guess that mitering is made more difficult with the other end of the pipe still connected to the rest of the frame. So too you would need a new longer head tube, possibly effecting the fork and all that goes with it.

[Sandy]

Not much goes with it, only the knife and spoon. :)

Spoon Sandy

[Kevan]

need I remind you that when you eat a rake has to be included too! :D

[Sandy]

That was funny- hoe, hoe, hoe.. :)

[csb]

i asked TK if merlin would shorten up my old road's
top tube and he said no. now maybe some other bloke
would consider it, but merlin doesnt want to rework
a frame they already finished... that's my understanding.

but i wonder if it were to be 'crashed' if in the process
of repairing, would they be willing to shorten the top tube.

[saab2000]

It is a bit of a theoretical question, but I would not be asking if there were not an application.

I have a frame which MIGHT, I repeat MIGHT, benefit from this mod. I have looked at the head tube and it looks long enough to be put back a centimeter or so.

Anyway, I also thought it could be done but thought that someone might have a better idea about it.

Ultimately, the main issue is one of cost. If it is too expensive it is not worth it as the frame itself was not extremely expensive.

[Smiley]

my 2 cents is sell it and buy one that works , once you start messing with the front end you'll never going to replicate the bikes handling as was before . Don't fool yourself and only a desperate repair shop would take on this type of challenge ...WHY . Besides the $$$ charged to make this repair would probably make starting a new look pretty attractive .

[saab2000]

I agree with Smiley on the cost/benefit issue.

I almost certainly won't pursue it, but thought it was at least interesting food for thought since there is a bike in my largish stable to which this could apply.

[cpg]

my 2 cents is sell it and buy one that works , once you start messing with the front end you'll never going to replicate the bikes handling as was before . Don't fool yourself and only a desperate repair shop would take on this type of challenge ...WHY . Besides the $$$ charged to make this repair would probably make starting a new look pretty attractive .

The front end handling can be replicated. It's just numbers. There's no magic there. In an earlier posting, I stated that it can be done. Does this make it cost effective? That's up to the consumer. Here's what's entailed in the repair-
-replace top tube with something shorter
-replace down tube with something shorter oriented at the new angle caused by the shorter top tube
-replace the head tube because it would be wise at this point
-new paint job

Again, the original question was can it be done. Yes but what would I know?

Curt

[zap]

Curt, doesn't tig welding create more heat than brazing with brass. Can tubes take repeated passes, in your example the seat tube/tt junction, without weakening the tube?

[cpg]

Yes and no. Tig is much hotter but more localized. The biggest concern would be the seat tube. Mostly the concern will be ovalizing the seat tube but a competant builder can deal with this. This is also why the head tube would be replaced. No reason to reheat it.

Curt