Bill;
Just a few rules will get you a nice, strong braze- welded joint:
1. Don't overheat the weld-- this creates intermetallics and a weak joint.
2. Have close- fitting joints. Don't fill big gaps!!
3. Both pieces must be really clean!
4. Use flux on both pieces.
One nice thing is that there is far less distortion in the braze- welded
structure than there is in a fusion- welded one.
Most welding books cover conventional brazing a little but braze welding not
at all. You're right-- motorcycles, bicycles, and (British) race car chassis
were using this technique years ago.
Regards, Neil
-----Original Message-----
From: ardunbill@webtv.net [mailto:ardunbill@webtv.net]
Sent: Friday, December 07, 2001 5:31 PM
To: Albaugh, Neil; land-speed@autox.team.net
Subject: RE: lakester frame
Neil, you are so right, before the invention of the joint jigger it must
have been a nightmare to fishmouth all the joints of a round-tube frame
at various angles.
You touched on an interesting subject here, "braze welding", and maybe
some of the real fabricators on this List would care to kick this around
a little for us (maybe they won't too, since it might be a can of
worms). I know next to nothing about the deep art of welding in all its
many subtleties and breakage risks, just taught myself enough torch
welding to make my own exhaust systems, do a little brazing, make some
simple parts, and tack stuff together so real welders could weld it.
I do know that for many years the finest racing motorcycle frames in
England were fabricated of alloy steel tubing (Reynolds 531 was the
standard stuff, also I believe famous for racing bicycle frames, may
still be) which was united by some form of braze welding because the
lower temperature was better for the tubing. The lore was "if it
sparkles, you've overheated the tubing, throw it away and start over, if
you use it, it will break later in service". So I was told by an
unimpeachable authority with many successful years of hands-on practice.
I have been told that some shops in this country today still prefer to
fabricate racecar frames with this braze welding. It seems to me that
no form of brazing has any "penetration", instead there is a
super-strong molecular bonding of the steel and the brass, rather than
the actual melting-together of steel that you get in a good heliarc,
tig, mig, etc. joint.
I gather that brazed frames are rare in LSR cars. Anybody who really
knows welding care to comment about these issues? I see nowhere in the
Rules that says you can't braze-weld your frames, but ?????? Cheers
Bill
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