In a message dated 3/26/2004 9:08:54 AM Eastern Standard Time, heine93@earthlink.net writes:
<< Silver vs. brass brazing:
It is interesting that a lot of Thanets - silver-brazed and all - have failed. It would be interesting to see whether this affected only the Silverlights with their rather unique tubing arrangement, or also the more traditional Silverthans. Failures also were astonishingly common among some early - and some relatively recent - American high-end frames, often silver-brazed, before people figured out what worked and how to do it. So I agree with Richard - silver-brazing isn't a guarantee for a lasting frame. On the other side, a lot of brass-brazed frames go on and on and on. Many earlier European frames were created in a way that today we would consider crude at best, but their track record speaks for itself (or doesn't in the case of some brands!). This world is not littered with failed Masis and Cinellis... >>
Silverthans were not subject to the same failure rates as the Silverlights .. This was due to the "innovative" frame design of the Silverlights, just not a sound design from an engineering pointy of view.... Hilary is "the man" on these bikes, so I hope he will chime in here.
I would posture that failure has little to do with brazing materials, but more caused by other factors, which can include gauges of steel, the design-for-function, how strenuously the bike is used and most of all, the builders experience/"touch".
56% silver content brazing alloy is, in theory and in proper application, by far the best way to braze thin steel and have the least traumatized joint. But a person who has only made a few frames is much more likely to have a failure than a brazer who has thousands under his/her belt! So we have seen some (USA mostly) newbie custom builders have failures.
But brass brazed steel has had it's issues too. All of us in the biz have seen our share of frames crapping out. But honestly few have been due to the brazing process... Most are just plain fatigue and over stressing the frame in extreme usage. In the good old days, they didn't drive those wooden plugs into steerer tubes for fun!
My 3 cents, Dale
Dale Brown
Greensboro, NC