This has been kicked around lately but I'll spare you the flogging...
From at least the mid 60s until they went out of business in the 80s Simplex made direct mount rear derailleurs that fit Campy style hangers. They may even work on proprietary Huret dropouts too but I've never tried it.
The correct derailleurs have a black shoulder bolt which screws into the rear of the top pivot. The shoulder is about 9mm in diameter and fits nicely into the threaded hole on the inside of the dropout. The head is about 3mm thick and takes a 6mm hex key.
Many if not most of the "claw" mount Simplex Rds were attached by a stud with a thin flat nut. A few had a 9mm shoulder on the nut so they may work also???
Simplex dropouts were designed to only fit Simplex derailleurs but that could be easily modified with some filing and threading the 9mm mounting hole to 10x1mm or 10x26TPI. From about 1974 on, you didn't need to file the dropout with many Shimano RDs.
Chas. Colerich Oakland, CA USA
Ben Kamenjas wrote:
> Being that all the talk is sounding like the yearly Masi-fest, in honour
> of Jerry Moos (where are ya Jerry?) I thought to bring discussion back
> to French (yes, I know he owns a Masi) and to be more specific: Simplex !!!
> I don't have a Simplex derailleur at hand but I have an itch for French
> and am wondering if there's any issues to fitting SIMPLEX rear
> derailleurs to Campagnolo 1010 type dropouts with threaded hangers? I
> don't wish to use a hanger or "claw" and I'm thinking of mid 70's and
> early 80's Simplex derailleurs like the SLJ or 610. It might be a
> non-issue ... I just don't know.
> To keep our resident Leporid from beating on his well worn keyboard I
> did search the archives and IntraWebs but didn't find anything specefic
> to answer my basic question.
> Ben Kamenjas
> Kensington, Australia