And here it is - one of the handful of most important derailleur patents of all time. This one describes the Campagnolo Gran Sport, the derailleur that established the parallelogram design as the definitive way to go.
Some geeky details are:
- The derailleur shown has a hanger adjustment screw. This feature, much requested by users, did not actually appear on production Campagnolo derailleurs until the 1980s.
- The cable clamp bolt has a screw head. It is also placed very close to the b-knuckle and mounted on a 'solid' protrusion - not the signature 'two armed' protrusion found on production models.
- The pulley cage is a sensible, sober shape. This was a feature of the very, very, first production models (as fitted to Fausto Coppi's 1951 Tour de France bike) and of all the Campagnolo Gran Sport variations after 1953. But in between all manner of fancy pulley cage shapes held sway.
- The pulley wheels appeared to be drilled with 12 holes each. Campagnolo collectors love to discuss the number of holes in the pulley wheels of early Campagnolo Gran Sports.
- The allen bolts at the knuckles have the 'large' heads typical of early Campagnolo Gran Sports.
That's enough obsessing for just now.