> ------------------------------
>
> Message: 5
> Date: Fri, 11 Sep 2009 03:54:49 -0700
> From: r cielec <teaat4p@yahoo.com>
> Subject: [CR] Huret Jubilee Rears and Rears in General ?
> To: Classic Rendezvous <classicrendezvous@bikelist.org>
> Message-ID: <223303.73157.qm@web53601.mail.re2.yahoo.com>
> Content-Type: text/plain; charset="us-ascii"
>
> Ahoy!
> I've some questions, please, concerning Huret Jubilee rear derailleurs
> and, rear ders. generally speaking. Yes, I am trying to set-up a drive
> train incorporating a Huret Jubilee short cage rear derailleur.
>
> Re: Huret Jubilee rear ders., short cage version
> I am of the understanding that the max. rear sprocket is 26t-28t,
> depending on one's specific set-up (that is: at these limits, it's a trial
> and error as to whether a 26t or a 28t can be handled).
> Can anyone confirm this, please? Yes, I'm trying to get an idea of what
> may work so I don't unecessarily purchase a heap of FW's that can't be
> used.
>
> Re: Rear ders., generally speaking
> I am of the understanding that (A) the length of the parallelogram
> determines the max. size of the rear sprocket; and, that (B) the length of
> the cage determines the amount of chain take-up. Example: If the rear der.
> max. size of rear sprocket is 26t then, doing a retro-fit of a longer cage
> will allow for smaller (front) chain rings to be installed because more
> chain can now be wrapped but, the longer cage does not allow retro-fitting
> rear sprocket larger than the 26t max. (that is: one is"stuck" with the
> 26t rear sprocket).
> Do I understand correctly?
>
> Thank you.
>
> Richard Cielec
> Chicago, Illinois; U.S.A.
Richard- There are a few more factors controlling the range and performance of rear derailleurs. Max FW cog is really dependent on how far from the axle the upper pulley is when the der. is pulled all the way in to low gear position. This dimension is made of the der. parallegram's "length", any upper pulley rotation around the cage pivot (think ST VGT compared to Shimano Crane), any parallegram canting to further move the upper pulley away from the cogs while pulling inwards, the size of the upper pulley, the axle to der. mounting bolt dimension (drop out length) and indirectly the chain length (and how it effects the cage position).
Some of these can be played with by axle positioning in drop out slot (assuming no verticals), chain length, chain ring spread (less difference of size produces less rear der. cage movement to take up the less slack changes), upper pulley size changes and of course any der./drop out angle adjusting screw (or pivot spring strength).
If you're willing to limit the gear combos you use then you can often exceed the claimed range with chain length changes. I.e. a chain length that has the upper pulley clearing the low gear cog when in the middle or small chain ring, but might not be long enough to allow big big cross over.
I use to routinely exceed the range of my derailleurs by a couple of teeth but with combo limits. Back in the day when the performance of gear systems were more dependent on the rider's technique the shifting response drop off, when exceeding range claims, was not too big a deal. Now that the current (and OT) gear systems are so set up dependent the amount of shift performance drop off is greater. As a rider who tours and has a Tandem I find this narrowing of the gear systems' "flexibility" frustrating.
Hope this helps you understand and plan your project.
Andrew R Stewart
Rochester, NY