I wasn't thinking of a 54T, but if the fitting was designed for say 50T, even 52T might not fit. As well as the problem you imply, that with a smaller than original ring, the FD will be too high to shift optimally. The highly integrated bikes that characterized the constructeurs were great when new, but that same integration often makes it difficult to change equipment, even items like chainring or cog size, or to replace components that haven't been made for 50 years.
I would think it would be much easier to fabricate something like the Le Chat FD if one had an original as a pattern or at least some detailed drawings with dimensions.
Regards,
Jerry Moos
Big Spring, Texas, USA
> From: Jan Heine <heine94@earthlink.net>
\r?\n> Subject: Re: [CR] Barra Frame on eBay
\r?\n> To: "Jerome & Elizabeth Moos" <jerrymoos@sbcglobal.net>, "'Classic Rendezvous'" <Classicrendezvous@bikelist.org>
\r?\n> Date: Friday, November 27, 2009, 10:12 AM
\r?\n> At 10:40 AM -0800 11/26/09, Jerome
\r?\n> & Elizabeth Moos wrote:
\r?\n>
\r?\n> > One consideration is the unique brazeon (or
\r?\n> weldon) for the FD. It will probably be extremely
\r?\n> difficult and expensive to source a special Barra FD.
\r?\n>
\r?\n> That fitting is for a Le Chat front derailleur with a Barra
\r?\n> lever system - see "The Golden Age of Handbuilt Bicycles" p.
\r?\n> 90-91.
\r?\n>
\r?\n> As with all these hand-made parts, the easiest way is to
\r?\n> make one, not try to find one.
\r?\n>
\r?\n> > Did Barra ever use vertical DO's on touring models?
\r?\n>
\r?\n> Yes, usually the cyclotouring bikes had vertical dropouts.
\r?\n> The bike on e-bay looks more like a sportif, like the one in
\r?\n> Bicycle Quarterly Vol. 6, No. 4, which also had horizontal
\r?\n> dropouts. The bridges on the e-bay bike aren't drilled for
\r?\n> fenders, either...
\r?\n>
\r?\n> >
\r?\n> > The FD fitting also will restrict the size of the
\r?\n> large chainwheel, although there were certainly steel
\r?\n> constructeur bikes with similar special FD fittings.
\r?\n> That's one disadvantage of constructeur bikes. They were
\r?\n> highly integrated with the original components, but that
\r?\n> also means it may be difficult to change components or
\r?\n> replace the originals half a century later.
\r?\n>
\r?\n> True, you can't put a 54-tooth ring onto most constructeur
\r?\n> bikes, but if Fausto Coppi could win the Tour de France with
\r?\n> a 51-14 as his largest gear, a 48-14 should suffice for the
\r?\n> rest of us... My problem usually is that the derailleur sits
\r?\n> too high - I'd rather use a 46-tooth "big" ring. And it's
\r?\n> been a long time since somebody dropped me while I was in my
\r?\n> big ring.
\r?\n>
\r?\n> Jan Heine
\r?\n> Editor
\r?\n> Bicycle Quarterly
\r?\n> 2116 Western Ave.
\r?\n> Seattle WA 98121
\r?\n> http://www.vintagebicyclepress.com