Comment by geocrasher
3 days ago
You may be right. I read this on the late Sheldon Brown's website, and it stuck. References:
https://www.sheldonbrown.com/tancrank.html
Left-threaded pedals and cranks are reputedly an invention of the Wright brothers, bicycle builders from Dayton, Ohio. (They also built airplanes).
https://www.sheldonbrown.com/brandt/left.html
The left-threaded left pedal was not the result of armchair theorizing, it was a solution to a real problem: people's left pedals kept unscrewing! We have read that the left threading was invented by the Wright brothers, but we are not sure of this.
So, I said it with more authority than was warranted. But it's good enough for normal dinner conversation references ;)
It looks like that method was known by 1880, if I read https://archive.org/details/indispensablebic00stur/page/14/m... correctly ('The "indispensable" bicyclist's handbook; a complete cyclopaedia on the subject') correctly:
> The Centaur Crank is first screwed up to a shoulder on the axle with right and left-handed threads, so that the pressure of the foot tends to make it all the more secure ; whilst, to prevent its loosening by “ back-pedalling,” a slightly tapered conical pin is driven through both crank and axle, and secured with a nut.