Another option, which is what I used, is to thread the DO and use a mototool to cut the tab stop into it. you can use another DO as a template. This was a Simplex DO on a Follis 172, BTW. This works fine, and you can still use the spring-loaded derailler if you prefer. This gives you a lot more flexibility, as the deraillers with the spring loaded plate seem to be scarce.
Craig Young firstname.lastname@example.org (work) email@example.com (home)
> -----Original Message-----
> From: firstname.lastname@example.org
> [mailto:email@example.com]On Behalf Of Jerry Moos
> Sent: Tuesday, November 07, 2000 8:10 AM
> To: Chris Beyer
> Cc: classicrendezvous
> Subject: Re: [Classicrendezvous] Simplex Info redux
> Chris, all Simplex derailleur from the 60's on should fit those DOs
> including Prestige, Criterium, and the nearly infinite number
> of different
> versions of the alloy derailleurs collectively referred to as
> the Super
> LJ. The Simplex incorporates a spring load upper pivot with
> tabs that fit
> on either side of the unnotched DO. A nut slides into the DO from the
> inside and the pivot bolt threads into the nut rather than
> directly into
> the DO. Many Huret derailleurs also had a similar arrangement to fit
> Simplex DOs.
> Jerry Moos
> Chris Beyer wrote:
> > Greetings:
> > I know this was discussed not to long ago, but I was asleep
> during the
> > class session.
> > I have recently acquired a French frameset which has
> Simplex dropouts,
> > and an unthreaded derailleur hanger with no stops. What do
> I use for a
> > rear derailleur? I think the frameset is most likely late '70s.
> > Unfortunately, I have no hands-on familiarity with Simplex
> > any more recent than the TDF (exept for the evil black
> plastic thing).
> > I seem to recall having seen reference to some sort of adapter which
> > Huret offered for the Dupar/Challenger, but I've never seen
> or touched
> > one.
> > If you know what I need, and have one to sell, please
> respond off-list.
> > Thanks,
> > Chris Beyer
> > Balmy (60s today) Bloomfield, NJ