Your Great Grandads derailleur, the Cambio Corsa

     The First bicycles had no gears, you just pushed along  while straddling your two wheeler. (Harley Davidson made lots of push bikes during the AMF years)
     Then pedals got added. Still no gears, or chain. As riders wanted to go faster, the wheel got bigger, as that was the only way to get more speed, and, with that, we got the iconic Penny Farthing.(Also known as Ordinary and High wheeler)

     Eventually the drive wheel was moved from the front to the rear(for safety) and cranks, gears, and a chain popped on to the scene.

     After a time the size of the wheel began to shrink, because now speed could be attained with gearing rather than wheel size.

     Then bicyclists realized they could have two(yes 2) ratios if they put a gear on each side of the wheel, and put wing nuts on the axle, they could turn the wheel around for an easy gear when they got to a hill.

 This led to the creation of the quick release skewer by Tulio Campagnolo. During a race he was unable to get the wing nuts loose to make a gear change, and a flow of creative juices spilled out on to the dusty road.
     Tulio did not stop with the quick release, he went on to develop many improvements to the sport, and today we take a look at one of them, the Cambio Corsa. One of the first derailleur designs, patented in 1933 and in use until the late 40s.

     (This bike is also equipped with an anti-flat device, a wire rubbing against the tire in the hope of popping loose that thumb tack rather than the tube.)

     Cambio has various translations, including gear, rate, change, and transmission. All of them are appropriate to the derailleur. Corsa means race, and this design was primarily used on racing bikes.So good job in the naming department.
     The Cambio Corsa gave the rider four gears and shifting on the fly. There was more of a learning curve compared to the indexed and electronic shifting we have today.
      While pedaling along, you reach back and open the quick release(Something any bike shop will tell you is a bad idea), then you actuated a second lever that moved a gate back and forth to shift the chain from one gear to another. Because this gate was over the top run of chain, you needed to back pedal to get the chain to shift. Back pedaling also allowed the wheel to move forward in the dropouts letting the chain slack enough to make a shift. Once the gear was selected you began pedaling again to move the wheel back in the dropouts and tension the chain. Then you tightened the quick release. (I am guessing there were very few sneaky upshifts before the sprint.)
     If you handed a bike equipped with this set up to a modern rider, it would look like a scene from Scanners.

     You are thinking to your self, "That is absolutely crazy. The wheel would come shooting out of the dropouts or cock sideways and lock up". And you would be right except old Tulio was on the ball and he made an axle with geared ends that fit up to teeth cut in to the drop out. This kept everything square and under control.

     Here is a video of the system in action.

And a link to a better video, This one is better
     And for the car guys, Maserati makes a car called the Cambiocorsa.

     So next time a friend complains about his shifting, or how he does not have enough gears to climb the hill, make him read this page.