Steve Leitgen asked:
Now how about a Campy Sport (dates)? Has one pulley. How many gears?
and Mick Butler responded, in part:
1953 was the official launch year of the single pulley Sport derailleur although they were about in 52. Neat looking gear but absolutely hopeless in operation.
Here are some more pieces of the puzzle:
The Sport required a small spring-stop hole in the rear drop-out, centered above the derailleur mounting bolt. Its only spring was designed to move the jockey pulley away from the FW as you shifted into higher gears with fewer teeth to contact. Huh? I believe that drop-out model with the hole was discontinued about 1961, but for several years after the boss was still on the forging.
The Sport is listed for 16 - 22 teeth, and will move across a 5-speed block (I think).
I find the whole design so absurd that I have never tried one on a bike. Better suited for mounting on a plaque as a gift to help an engineer remember that not all designs are useful. :-)
harvey sachs mcLean va the other thing I'm going to (eventually) find the time to mount on a plaque is a genuine Watt-type flying ball steam engine speed governor. Fantastic invention, and I feel lucky to have been able to buy one out of the Appalachians, legal. I guess they had no use for the engine, just wanted the boiler for processing corn? But, I digress. When I mount it, it will get a plaque that just says: "Governor, with real balls." (I think that this was the first true feedback regulator for machinery, saving the wages of a boy used before that in the mine applications).