MAKE subscriber Steve Hoefer sent us a link to this fascinating piece on retro-direct drives for bikes. Not really sure how practical it is, but the engineering is interesting. And, it’s probably a great way to work different leg muscles.
What’s a retro-direct bike?
At the beginning of the 20th century, although derailleurs and geared hubs had already been invented, an innovative company, the Manufacture FranÃ§aise d’Armes et Cycles from Saint Etienne in France, created a one-of-a-kind bicycle, the Hirondelle (meaning “swallow” in English), sporting four speeds, two of which came from a primitive front derailleur, and two from pedaling forward or backward.
The system was clever, involving two independent freewheels (large and small), and a single chain going from the top of the chainring to the top of the small cog, around the small cog, around an idler installed under the chainstay, back to the bottom of the large cog, around the large cog, and back to the bottom of the chainring.
When the rider pedaled forward, the chainring would pull on the small cog and engage its freewheel, while the large cog would freewheel in reverse. Conversely when the rider pedaled backward, the chainring would drive the large cog forward and let the small cog freewheel.
An excellent and detailled presentation of this system can be found at this page.