My early to mid 50's W P Newton has a 28 tooth rear sprocket and a 44/28 tooth chainset, using a Simplex touring derailleur. (I believe it's the Grand Tourisme model, but others will handle a wide range, too). This gives me a bottom gear of 27 inches, which is fine even for the very steep hills round here.
Have a look at
http://smg.photobucket.com/
Alternatively, a Cyclo Standard derailleur will handle a 28 tooth rear sprocket, but it's a bit heavy and inelegant compared to the Simplex.
Neil Foddering Weymouth, Dorset, England
>From: Amir Avitzur <avitzur@013.net>
>To: Classicrendezvous <classicrendezvous@bikelist.org>
>Subject: [CR]Fr. Der. for LARGE jumps
>Date: Sat, 20 Jan 2007 18:54:08 +0200
>
>
>My Hobbs is getting a Stronglight 49 crank with TA rings.
>It is being set up for touring with very wide gears.
>
>What's the biggest climb typical 50's derailleurs could make?
>
>My guess is that plunger type front derailleurs aren't recommended on 20
>tooth climbs.
>
>Amir Avitzur
>Ramat-Gan, Israel