Rope-Drive Bicycle: See How It Works!

[Redbelly98]

This looks pretty cool, a new design of bicycle that uses a rope instead of a chain. Here is a PhysOrg article that has some good videos showing how it works:

http://www.physorg.com/news204349619.html

Several videos are linked there, but the best (in terms of understanding the operation) appears just before the words "Another advantage of the system..."

 

[Borek]

Can't say I was able to understand details. Crank and front part are obvious, but what happens near the wheel axis is a mystery, as it doesn't show how the string behaves at the rear wheel axis.

This one seems better to me:



What I like most is that there is no overlap between these 19 gears, and shifting up/down is always done the same way, no need for tricks with front/back sprockets (I mean combinations of up/down done at the same time).

 

[Redbelly98]

Can't say I was able to understand details. Crank and front part are obvious, but what happens near the wheel axis is a mystery, as it doesn't show how the string behaves at the rear wheel axis.

It appears to be a ratcheting mechanism at the rear wheel. When the string is pulled forward it drives the rear wheel. During the return stroke, there must be a spring mechanism to rotate the small wheel (that the string is fastened to) backwards and keep the string taught; and if it is a ratcheting mechanism then no backwards torque is applied to the bicycle wheel during the return stroke.

I imagine one would carry a spare set of ropes around, just as I used to always carry a spare inner tube when I used to bicycle regularly.

 

[Borek]

Thanks. What I meant was that I couldn't make details from the first video, after seeing the second one it became obvious.

I am just back from biking, and while traversing a muddy puddle I started to think if it is really as good as they claim in such conditions. There is a strong friction and I would expect strong abrasion in the place where the force is transferred (sorry, my English fails me here). That means fast wear of two elements on each side.

 

[AlephZero]

This reminded me of one of the stories about Turing, when he was working as a code-breaker in WWII.

His bike chain broke, so tied the ends together with a piece of string (so the ends didn't touch the ground) and pedaled alternately forward and backward the correct number of revolutions so the string never reached the sprockets. This "fix" worked fine for several years, apparently.

 

[boneh3ad]

It won't catch on until they find a way to add a differential, methinks.