Are we just talking about the fact that Simplex dropouts are unthreaded with Simplex derailleurs attached via a threaded collar or bolt inside the DO? The standard solution, if you wanted a Campy derailleur, was to tap the DO for Campy thead, but you also had the file a notch in the DO for the derailleur stop. I think Huret derailleurs could usually be attached to Simplex DO's with a nut inside the DO. I've never seen this done with a Campy RD on a Sipmplex DO, though. Maybe that is because you still would have to notch the DO for the derailleur stop.
I recently picked up a Sabliere French touring bike. It has a Simplex SLJ 5500 rear derailleur which mounts on the outside of the derailleur hanger (as one would expect) but the mounting screw is inserted from the inside of the derailleur hanger. I want to change derailleurs on this, but do not have another derailleur that mounts this way. I attempted to mount a derailleur in the "normal" fashion only to discover that it will not screw in. I tried a Jubilee.
A couple of questions: are there other derailleurs out there that mount in this way (I vaguely recall some discussion about a Jubilee that mounts in this fashion, but then I vaguely remember most everything, some of which didn't happen)? Could the threading be redone to take a "normal" mounting bolt (the size of the screw-in appears smaller than the "normal."). And has anyone else faced this problem and solved it?
Thank you as always.
Tom Hayes Chagrin Falls, Ohio sunny and over 80 degrees.