Years ago I crashed a Formula Ford because of an aluminum chassis member
failure, and severely damaged the frame. The car was built in the early
70's. In that era, British builders used mild steel tubing and brazed
joints. No one used chrome moly because it took so much special effort to
prevent damage to the chrome moly characteristics and the benefits weren't
that great anyway. I tried to find another frame, to no avail. I took the
frame to a professional and his evaluation was that the frame tubes had
rusted from the inside and the tube wall thickness was half the original.
You should check that too. But, he also told and showed me how to
hi-strength braze. The result was that I built a surface plate, a fixture,
I redesigned the frame to eliminate the possibility of future failure, and
I built an entirely new frame. It was a successful project, because in the
first year of competition I won the Chicago Regional Championship in that
car. All of which is beside the point, of course, but I couldn't resist
throwing it in.
The best way to do this is using nickel bronze rod. It's expensive but the
resulting joint is nearly as strong as steel -- I think it has a yield of
80,000 psi or so. If you use flux-coated rod, the flux puddles over the
weld puddle and you have a hard time seeing exactly what the weld puddle is
doing. The fix for this is to use a Jet-Fluxer. This is a pressure bottle
filled with liquid flux. You pipe the acetylene gas to the bottle -- it's
simply a bubble-through device. The acetylene picks up gaseous flux and
carries it to the brazing flame, and since the flux is entrained in the gas
it does not interfere with what you see. You must carefully control the
nature of the flame as far as oxygen-rich or fuel-rich is concerned.
I don't know if the bottles and flux are still available. The flux is very
highly corrosive, and you can plan on going through one rebuild of your
acetylene regulator during a complete frame build.
Finally, I still have my Jet Fluxer. I have not used it for years and will
donate it to anyone who is interested in using it. It is still half full of
flux because I have never figured out how to safely dispose of such a
corrosive chemical. Which also means, of course, that I don't know how to
ship it. Nevertheless, the offer remains.
At 09:58 PM 10/4/02 -0700, you wrote:
>Thanks to all that responded to my question on the Zink frame. Looks like
>I'll be
>getting an oxy-acetylene set-up soon!
>There is a welding supply shop down the street that should have everything I
>need.
>
>Mike Ritz
>Bent 67 Zink
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