I would say this comes down to the Simplex derailleurs (such as the Prestige and Criterium) requiring less cable pull. The plastic Simplex levers had a small "spool" diameter to the point where could not really work well with, for example, a Suntour (which required rather large cable travel). The demultiplacateur reduces the cable travel to allow a larger spool lever to interface with a derailleur requiring smaller cable travel. One data point is that the demultiplacateur came in the bag with NOS Simplex bar-cons (Cross-Commandes) I bought about a year ago from the seemingly endless supply of Ron Boi. I bet the bar-cons pull a fair amount of cable although I can't get at the bike they (and a demultiplicator).are on to check right now.
The relais demultiplacateur de transmission avec cable is Simplex Ref. 2343. As shown in the Cross-Commandes (Ref. 2615) instruction sheet, the middle of the bellcrank travel would be at the roughly at the point of each cables tangency to the arc about the bellcranks center when set up properly- the ratio would change very little, if at all, since the changes in the length of "A" and "B" would be roughly proportional as the crank were rotated away from the center position.
Joe Bender-Zanoni
Great Notch, NJ
> If you will kindly turn your attention to
> http://bulgier.net/
>
> Please note that since radius "A" is larger than radius "B", point "1"
will
> move farther for a given amount of rotation than point "2"
>
> Since "1" is attached to the shift lever and "2" is attached to the rear
> derailleur, you'll have to move the shift lever farther than normal to
move
> the rear derailleur a certain amount.
>
> Since "A" and "B" are changing at different rates through the range of
> motion of the bellcrank, the ratio between the two isn't a constant and
even
> the average ratio can vary depending on initial conditions - where you
> position the bellcrank to begin with. It probably doesn't change enough
to
> worry about though; and most people position it to start and end roughly
> equal angles from the neutral angle between chainstay and downtube. I
don't
> see any advantage to setting it up substantially different from this.
>
> But the most important thing is...... Happy New Year!
>
> Mark Bulgier
> Seattle, Wa
> USA
>
>
> > -----Original Message-----
> > From: r cielec [mailto:teaat4p@yahoo.com]
> > Sent: Tuesday, December 31, 2002 7:49 PM
> > To: Classicrendezvous@bikelist.org
> > Subject: Re: [CR]Demultiplicators...
> >
> >
> >
> > Is there a photograph or illustration of this device ?
> > Richard Cielec
> > Chicago, Illinois
> > Philcycles@aol.com wrote:
> > In a message dated 12/30/02 6:04:03 PM, sachs@erols.com writes:
> >
> > >This may just prove that logical arguments aren't the story,
> > and that Phil
> > >
> > >is right.
> >
> > The "feel" thing comes direct from a Simplex ad.
> > Phil Brown
> > NoHo, Ca
> > _______________________________________________
> >
> >
> > ---------------------------------
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