Thanks to the wonderful Bicycle Museum of Bad Ideas for cataloging all the versions of non-straight cranks from at least 1931 through today. Notable entries include:
- Agache 1931
- Rosa 1938
- P.M.P. “L” or “bent” cranks of the early 1980’s
- Z-Torque” as of 2012
- dpardo Sickle crank available today
As MOBI correctly points out
A moment’s thought shows a straight crank and an L crank always have the same relation between pedals, chain, and bottom bracket. Thus, there is no advantage to L cranks. And an L crank always has more material than a straight crank, so is always at a disadvantage for weight, strength, stiffness, and/or cost.
This is pretty good confirmation of the line about the rate at which suckers are born, no matter who said it.