----- Original Message ----- Harry asked:
> You have experience of observing and recording the "natural history" of
> these creatures:
>
> For those with long semi-horizontal dropout slots, would you comment on
> the role of axle placement for the operation of the rear der? Assume you
> add an inch (25mm) of chain to move the axle 1/2" (25mm)back in the
> slot, so relative chain tightness has not changed, have you increased or
> diminished the capacity of the rear der to handle a larger largest cog?
>
> Asking this here because I don't think it is covered in say the Sheldon
> Collection, beyond the general race-based observation that shorter
> wheelbase --> more precise handling.
>
> Harry Travis
> Washington, DC
> USA
In my experience, one gains tooth capacity with rearward placement with long and short dropouts.. In fact, this is the means by which one can may persuade a Nuovo Record RD to swing to 28t (or better according to some). Note however, that chain length likely will need to be kept as short as possible to prevent the jockey from striking.
I suspect that the Huret design philosophy at the time (and for a long time before in the RD geometries from which the Jubilee evolved) was predicated on small evenly spaced cogs for best shifting performance. They were not constrained by a front chainring minima of 42t or 44t for 144/151 BCD cranksets given the lack of limitations of Stronglight and later TA crankarms. The long cage RD was no doubt intended to wrap a bit more chain rather than to accomodate larger freewheels. Later Hurets such as the Duopar showed that they could easily swing over some pretty big cogs.
Charlie Young
Honey Brook, Pennsylvania USA