Comment by eesmith

Comment by eesmith 4 days ago

I'm having a really hard time verifying that it was a Wright Brothers innovation.

I can find claims that it was so, but nothing substantial. For example, this 1959 kids book - https://archive.org/details/wilburorvillewri0000augu/page/17... .

On the other hand, I can find cranks which had reversed threads, pre-dating 1900, like US643349A filed 1895 where "The screw-threads on the parts b b' of the shaft are oppositely directed, or, in other words, are right and left hand threads".

It's described as protecting the ball-bearings, not to prevent coming loose.

https://www.wright-brothers.org/Information_Desk/Just_the_Fa... says:

> In 1900, the Wrights announced a "bicycle pedal that can't come unscrewed." Pedals were mounted to the crank by threaded spindles. On early bicycles, both crank arms had standard right-hand threads. As the cyclist pedaled, the action tended to tighten one pedal and loosen the other, with the result that one pedal kept dropping off the bike. British inventor William Kemp Starley had solved a similar problem years before when the right-hand cups that housed the crank or "bottom" bearing on early bicycles kept coming loose. He simply reversed the thread direction on the right cup so the pedaling action kept it tight. It wasn't long before bicycle makers realized the same solution could keep the pedals in place. Wilbur and Orville were in the vanguard of those manufacturers that offered right-hand threads on one crank arm and left-hand threads on the other.

That is, the Wright Brothers were early promoters of the design, but not the innovators.

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 ;)

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eesmith 3 days ago

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.

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