justridingalong

I have a frame built out of 6061 aluminum, there's a 1/2 crack in the weld at the seattube/ bottom bracket junction. Tig is out because the frame would require heat treatment etc after welding. Has anyone heard of low temp propane torch repair for aluminum. There's several outfits offering the welding rod for this. Durafix (durafix.com) is one of several.

HillRider

What is a 1/2 crack? 1/2 inch or 1/2 way around the weld? That's a high stress area in a frame and, in either case, I'd retire and replace the frame.

I have to think if that type of low temperature welding/brazing was adequately strong, every maker would be doing it.

Crankycrank

I've used some of the propane/alu rods you're talking about to put some brackets on my rear rack. It seems to be plenty strong for small parts but I seriously doubt it would be strong enough to hold a frame together with. It's more like an alu solder and doesn't flow as well as a proper weld either. You could easily put enough heat into your frame tubes to weaken them as well with the heat needed to melt the rods.

davidad

Manufacturer's warrantee? If not it is time for a new one. Al has a finite number of flexes before it cracks due to fatigue. Some place else is going to break soon.

BCRider

Those lower temperature rods are more like soldering or maybe at best sort of like brazing. They won't restore the area to the original strength. At least I would not trust it.

Talk to a good aircraft welder before you dismiss the idea of tigging it. The whole heat treating the whole frame is largely urban legend. An aircraft welder will likely have some better thoughts on it that you can trust better than us lot on something this touchy. Some alloys would require a full item heat treatment. Others maybe a little special work and still other alloys nothing at all. Also what is needed depends on the final heat treatment level of the material of your particular 6061.

hueyhoolihan

for no good reason, i've always had my suspicions about the necessities of heat treating. it may be because i once had a camshaft reground (okay, it was steel) and put about 50,000 miles on it before i sold it. if i had a frame that i liked and needed to be re-welded i would be sorely tested (if the price was right ) to just have it re-welded and ride it and see what happened, even aluminum.

i just occurred to me that i may be suspicious in that i recently had a bent aluminum motorcycle front rim re-welded after it had been cracked and bent from running over some road debris. it (the motorcycle) weighs almost 1000 lbs when i'm riding it.

HillRider

It's very likely that camshaft was through hardened and the grinder didn't allow it to get it hot enough to change the heat treated properties.

FastJake

Whether it is necessary or not for a given application, heat treating is a very real process for steel and aluminum and if you do some quench and temper tests at various times and temperatures you can see that.

Heat treating the frame is certainly possible if you can get access to one of those big industrial ovens capable of high temperature for long periods of time.

bradtx

Check with these folks: https://www.bikeforums.net/forumdispl...-Framebuilders .

Brad

Kimmo 

Not to mention a jig that'll withstand the heat.

Homebrew01

Picture ? A small tig repair is not likely to heat up the rest of the joint very much.

bradtx

Same as I thought, along with using wet rags all around the repair. I just don't know for sure.

Brad

WickedThump

Plasma needle arc would do the job without a lot of excess heat. Durafix is basicly aluminum solder, and it's very difficult to use because it has a narrow plasticity range. I've only used it myself for coil repair.

fietsbob

Aluma-weld or scrap it are probably your 2 choices , if the side effects of welding are too much of a worry, then scrapping the frame is what is left.

justridingalong

Found a welder who's done a lot of frame welding for a well known bike brand. He says he's had good results repairing aluminum frames. He came highly recommended by another well known local frame builder. Thanks for your input, and also for not calling me a moron for posing the question ,ha, ha, ha.

Homebrew01

You moron

ultraman6970

Depending on where the crack is, you can fix the stuff. But there is a problem, probably it will crack somewhere else, thats the reason after welding the good quality frames goes to an oven to overheat the whole frame so the whole thing gets the same strength, if you weld in a repair the weld will be stronger than the tubing and the tubing cracks again but in another place.

Is the OP call after all.

justridingalong

I inquired about alum frame repair for a rider who mainly rides fire roads on his SC Blur.
He had it repaired at Arc-Tec in Santa Cruz and so far he's happy with the repair , because it hasn't cracked. This response is for a guy that wanted a personal reply, but I haven't attained that level on BF, so this is the only way I know how to let the guy know, idiot that I am w/ computers.

HillRider

You only have 13 posts and to do PMs I believe you need to be a "Senior Member" which after 37 more posts you will be.