Jan, you must have missed my posting.
There is a seven page set of detailed set-up directions and shifting instructions printed by Campagnolo when Cambio Corsa was current in the 1930s and '40s.
It even specifies how to slacken the chain when you shift. I had always heard that you softly pedal while closing the quick release, but this is in fact, incorrect.
The directions say to pull the shift lever forcibly to the right after completing the shift by backpedaling; this would be at the same time that you close the quick release while the pedals were stationary.
This procedure creates chain slack by bending the chain laterally (sideways to the right) which pulls the wheel forward just enough so the chain doesn't bind.
Interesting, the info contained in Catalogo Campagnolo, yes? ;)
Chuck Schmidt South Pasadena, CA http://www.velo-retro.com (Reprints, T-shirts and Timelines)
Jan Heine wrote:
>
> Cambio Corsa:
>
> For a detailed description of how to operate the Cambio Corsa, see my
> article in On The Wheel. This was discussed a few weeks ago when
> people asked about Learco Guerra, so you'll find the exact reference
> in the archives. Not an original text from the old days, but I doubt
> they had many instructions back then anyhow...
>
> Overall, it is cumbersome, requires some concentration, but it is not
> difficult to use. It does not require years of practice or detailed
> instructions.
>
> To your question: the wheel goes backwards on its own, under the
> weight of the rider, because the dropouts are inclined. So you move
> the wheel forward by pedaling (softly, otherwise, it'll hit the seat
> tube), and backwards by coasting. The act of shifting to a bigger cog
> alone will move the wheel forward, so there is no need to first move
> the wheel, then lock the QR and shift, then adjust the chain tension
> (as written in one report on the system). When shifting to a smaller
> cog, the wheel will go back all the way. The difficult part is to get
> the chain just a tad slack, after you are done with the shifting
> itself, so it doesn't bind.
>
> Some reports published 5-10 years ago, before these bikes started
> coming out of Italy and becoming somewhat commonplace, about shifting
> the Cambio Corsa simply are wrong, written by people who have never
> ridden the thing or seen it in action. (As I said above, back then,
> there was no info available, so the authors may be excused for their
> errors.)
>
> One article stated that Bartali used one hand to shift, the other to
> check the chain tension at the same time. This is physically
> impossible (you'd need two right arms!) - Bartali probably checked
> the chain tension after he had shifted... although I'd think that
> with that much experience, he didn't need to check often. He probably
> knew how much pressure to apply on the pedals so that it was right.
>
> Jan Heine, Seattle