Can you advise

[SITHLORD]

Hi guys...

Sorry if this is the wrong area of the forum BTW...

I was given this website name to see if someone could possibly help me with a repair on a bicycle frame as you are experts in this field..

The Material is 7020 Alloy, and has been (I think) TIG welded.. the frame was then acid dipped to reduce weight..

The problem I have , is it has developed a crack around the down tube , near the head tube on the frame..

Can anyone advise on if this could be repaired safely and by whom, ideally someone in the northumberland area as this is where I am located or indeed I would not mind posting the frame for repair..

Your help would be very much appreciated.

I can provide any additional details/photos that may be required..

TIA.

Si

 

[Pete.]

Hotrodder is your man for that!

 

[wyn]

It looks a bit like the gusset has caused the problem.
It has stiffened up the area it supports but comes to an abrupt stop. the tube then flexes at this junction and causes the cracking.

If you get it repaired maybe get the gusset cut off and a better designed one welded on .

 

[SITHLORD]

Do you think this is repairable then guys .. ?

The frame cost me a fortune when I bought, only realizing recently how bad this gusset design is..

 

[runnach]

The Material is 7020 Alloy, and has been (I think) TIG welded.. the frame was then acid dipped to reduce weight..

The problem I have , is it has developed a crack around the down tube , near the head tube on the frame.

Looks a tricky repair, meaning to do a strong lasting repair! You state frame has been acid dipped. Looks to me it has been anodised with a black die, now here lies the first hurdle with contamination problems due to anodising process.

Wyn rightly states area around gusset is a high stress area, running a weld round crack will have an annealing effect on the material. Might be an idea to fit an inner sleave (if one can be installed?) then plug weld to keep in place. Problem is finding solid bar of the same spec.

Hopefully other members may know an easier route to take?


Cheers.......

 

[pedrobedro]

It looks like the crack started from the heat affected zone where the gusset is welded and then propagated round the tube as it flexed. I can't actually see what the gusset is supposed to do where it is, it would have been better gusseted to the top tube and boxed in or just butted up to the steering tube. You could weld round the crack then plate the sides and box the back in if you could get someone to do it. Aluminium alloy that thin is not going to last long, it has a finite lifespan unlike steel and if it's going there it's going to be weak elsewhere.

 

[scarecrow]

best bet is probably to replace the whole tube and refit a proper shape gusset all that one did was put stresses back into the lighter tube

 

[Glyn]

Is it worth repairing? Gussets are usually left open on the end, to prevent this. I'm only asking because I once had a frame snap at this point, wasn't going fast but happend so quick I almost impailed my self on the handle bars. Would you really trust it again after a repair?

 

[chap]

So i guess that gusset is to strengthen the head tube join for longtravel forks, where there is more leverage at the head/down tube intersection.
Seem to remember seeing these gussets on a lot of bike frames, with classier ones (I guess the better developed) get the gusset left open on the end.

Personally, i think you'd probably be better off with a new frame.. having it welded is one thing; getting it heat treated and the strength back in there is another!

Incidentally, what model frame is it? And what sort of age?

 

[chunkolini]

Dead meat, I would not repair or ride that after a repair there.

Chunko'.

 

[hotrodder]

Physically repairing it is easy enough but as said a repair that will last is another thing- however it's done there will be a new stress riser added that'll be the starting point for a crack (just like the poor gusset design that caused the existing crack).

As Chunko' that's dead i'm afraid.

How old is it? No chance of warrenty replacement?