I suspect it was because heat control was not great either due to unrefined technique on the part of the brazer or possibly poorer brazing materials that required heat sufficient to affect the strength in the tube where the bosses were attached.
Might also have been the tubes themselves which were more affected by heat than are modern tubes.
-----Original Message----- From: firstname.lastname@example.org [mailto:email@example.com]On Behalf Of Fred Rafael Rednor Sent: Wednesday, August 01, 2001 3:00 PM To: Bicycle Classics inc; classicrendezvous-bikelist.org Subject: Re: [CR]Earliest Brazed Downtube Shifters ???
> My guess would be somewhere in the 1930's.
Sounds about right. But I still must ask, why did they
fall out of favor or fail to catch on with racing builders?