On Mon, 7 Apr 2008 11:34:05 -0400, "Ed Huntress"
wrote:
wrote in message
...

okay thank you!

i do want to use 6061 but there aren't too many suppliers of aluminum
alloys in my country and I just found this one that sells 6063 alloy
products.

either 6061, 7075 or 2024 alloys but then it's really difficult to
look for suppliers here.

i guess i'll have to look around some more.

Except for 6061, those other alloys will require lugs and adhesive assembly,
rather than welding. 7075 can be welded but it loses its corrosion
resistance. On 2024, you won't get a satisfactory weld, and the tubes may
crack. And the welding on 6061, or any weldable aluminum alloy, almost has
to be TIG (GTAW) when you're welding tubes.

All in all, you need a really good reason to make a tube structure out of
aluminum, rather than steel.

Some of the specialty bikes are made with specially forged or formed
flanges at each frame join point, fluxed and 'preforms' of wire solder
placed inside the lugs, clamped into a jig, and the whole frame is
brazed in one shot in an industrial oven...

But when you consider all the variables that have to be controlled
and gotcha's conquered, that's an even trickier method than TIG
welding - useful only for production shops that get lots and LOTS of
practice at it.

For a low production shop or a low-skills country, and if you insist
on using aluminum tubing: Buy excellent welding gear (Miller) and
proper safety gear and accessories, and have a few staffers sent to a
tech school and get /lots/ of hands-on practice time (buy material
they can use for practice coupons) to learn how to TIG weld properly
and well. It is an art that takes time to perfect.

-- Bruce --