On Tue, 01 Jan 2008 21:54:48 -0800, Richard Riley
wrote:

On Fri, 28 Dec 2007 19:46:57 -0800 (PST), "
wrote:

On Dec 28, 2:57 pm, wright1902glider wrote:
the author
seems to think that 4130 cro-mo steel can't be welded with an oxy-
acetylene torch.
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Pure bull****. Indeed, for the stresses encountered in bicycles
(which is what he's talking about) there are any number of BRAZING
compounds that yield joints stronger than than normalized 4130.

O/A does just fine airframes... and for bike frames.

If brazing gives stronger joints that normalized 4130, why aren't we
brazing airframes?

(I'm not saying it's an incorrect statement - I know better than to
disagree with VD on something like this. I just figure there must be
a reason, like the brazing compounds are more expensive.)

It is not your standard brazing. It is "fillet brazing", using a much
stronger "spelter" than your standard braze. The process uses a gas
flux (a "Hookah" bubbling the acetelene (I think - might be the O2)
through the liquid flux ). The flux in the flame is EXTREMELY
reactive, so the flame "scrubs" the joint, leaving little if any flux
behind. These brazed joints ARE stronger than the 4130 or 4140 base
metal.

The process was developed for and used extensively by small race car
chassis fabricators in England and the continent. Lotus is a good case
in point.

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