I believe this is interesting information about how to mount a front derailleur to a curved seat-tube.
Steven Maasland Moorestown, NJ
I followed your emails on the CR list, but, not being a member cannot post this reply there. If you want to do so , feel free.
I have used several JT curved tubes to build time-trialling frames and have on occasion fixed front mech bosses. You can do this by obtaining a pressed steel - NOT microfusion cast - front mech bracket and sawing of the small lug that actually brazes to the frame. You can them sometimes braze this to the tube in a position , depending on the mech being used - to enable you to use both chain rings without the mech's cage being cocked up in the air causing chain rub. Otherwise you may have to braze a small piece of mils steel to the bracket to efectively push the bracket into the required positin. This extra piece lying directly backwards of the seat tube is brazed into position.
The other solution is to contact Trevor Jarvis, of "Flying Gate" frame fame. His frames as you will know use a vertical "seat tube" which throws the frontmech both far too far forward and at the wrong angle. To get around this Trevor, who is a good engineer, designed and had cast for him, aluminium spacers pieces which screwed on to the "seat tube "in place of the mech, and then the mech, less the securing hinged bracket was screwed into the back of the spacer. Sounds a bit clumsy but it was well engineered and very rigid. If you search on Google etc for either Jarvis or "Flying Gate " I'm sure you will find his web-site. It might even be on the CR site under "Baines" on the English builders page.
Good hunting
Norris Lockley
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