Skyhawk GT2-A Frame Fail

Timbone

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After Thursday's commute home on the motorbike, something didn't feel right just as I got off the bike. I did a simple flex test and, yes, the Skyhawk Aluminum frame was flexing. Flexing too much at that..

It took a few minutes but I finally found a crack that traveled half way around the downtube, just below the bottom weld of the in frame gas tank.

Here are my options as I see them:


Could simply buy a new frame: $120-150.

Could buy a new bicycle and move all the stuff over. I have more than enough parts! $40-150.

Could try to find a welder to weld a new aluminum support piece. $20-60.

I am working on finding a decent tig welder because my other option has failed. I had a plan:

I have some propane so I went to Harbor Freight and picked up some of those alumalloy rods as I have used them in the past with good results. My idea was to braze the rod into the crack, grind it down and then braze an aluminum collar around the area to bulk it up.

This was a fail. The aluminum rod melted but rolled right off the base metal. Attempts to braze the aluminum collar over the crack failed, too. The rod adhered nicely to the aluminum collar, but it would not braze the piece to the bike frame. I thought it was going to but it just wouldn't. I hda scrubbed and cleaned the entire area very well. I figure there must be some kind of alloy in the aluminum bike frame.

Anyway, a good welder could fix this up in a hurry.
 
AL and MAB's don't mix, for long. Even welded it's too dangerous, if possible go steel.
 
the problem with the gt2a frames is that there's no bracing to keep that aluminum piece from shaking around, so they tend to break right where you described. you need to have gussets welded to the pedestal or you need to buy one of bikebobber's miami mod mounts, but unfortunately bikebobber isn't doing business anymore. I believe you can still get clones of his design from mzmiami on ebay
 
I've got the same frame too, gonna switch to something else when it cracks. for now it looks cool as hell though
 
the pedestal is the problem, it's unsupported and causes frame cracks. you need to gusset it or use miami mod mounts
That is not where he said this frame failed.

It took a few minutes but I finally found a crack that traveled half way around the downtube,
just below the bottom weld of the in frame gas tank.

AL and MAB's don't mix, for long. Even welded it's too dangerous, if possible go steel.
Aluminum framed Felts never crack.

There is no comparison between these Chinese frames and a Felt.

The aluminum feels thin and they probably don't heat treat the welds
properly.

There are other quality made aluminum frames too.
 
Good reading! Actually, I created my own bomb proof motor mounts out of steel and worked around the pedestal mount. That thing is designed to fail.

The more serious problem I am confronting is a crack failure far up the downtube, just below the bottom weld on the gas tank. Looks like the crack started out of the weld on the inside and has worked a little over half way around. This frame is unrideable now.

I'll put up a pic of this tomorrow. I cleaned the damaged area carefully but the alumalloy rod would not take to it. There must be some kind of annealing in the aluminum that prevented brazing.

I am convinced that a decent TIG welder could fix this up and give this frame another year's life. Gotta find him, though! I can TIG weld, but I don't have the equipment.
 
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