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PostPosted: Tue Jan 15, 2013 5:44 am 
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I came across this device lately. And the designer says this is to capitalize on the energy otherwise wasted in the ankling action while pedaling.

Frankly I am a bit lost on how this could work. But here is a pic for your thoughts.


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Posted: Tue Jan 15, 2013 5:44 am 


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PostPosted: Tue Jan 15, 2013 9:22 am 
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Cocaine is bad for designing bike parts.


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PostPosted: Thu Jan 17, 2013 8:02 am 
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That's odd, for sure.

So, the sprocket on the pedal/platform shaft is ~14t and the one mounted on the crank is ~28 (very rough estimate from that picture. That means a 2:1 ratio, so its a torque multiplier.

Unless there are some one way clutches involved, that arrangement fixes the position of those platforms relative to each other. That means they would have to be timed to make sure they weren't out of position with each other. Sounds uncomfortable having your ankles timed together like that (couldn't do a 1 leg calf stretch for sure).

I don't see how it really would make any more power since all lower lef forces are in series with your upper leg forces and therefore reacted against them given the platform appears to be under the ball of the foot. Also, the crank itself wants to move at a constant velocity, else the whole bike would have to slow down/speed up. So, if you pushed your toe down on this bike, the crank would want to speed up. But, it can't. So, your upper leg would have to slow down by a 1:1 corresponding amount. That seems inefficient.

I do think moving the pedal mid-foot makes sense expecially for endurance riders and for triathelons. But, this is something very different.

Take into account weight and friction and I bet this is easily a net slower bike....just this one engineers $0.02.


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PostPosted: Thu Jan 17, 2013 6:16 pm 
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My guess is it's yet another example of the erroneous assumption that force applied perpendicular to the direction of motion is "wasted energy". Energy = force dot distance; the perpendicular component of force doesn't contribute.

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PostPosted: Thu Jan 17, 2013 6:48 pm 
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Yeah, what DJ said....... :noidea:

Anybody got a weight on that crank? :smartass:

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PostPosted: Fri Jan 18, 2013 2:02 am 
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Lol, a wind-up crank based on rotating the pedals?


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PostPosted: Fri Jan 18, 2013 6:32 am 
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Here is a second version of this.

I communicated with the designer a bit more and looks like the idea is that at the 12 o'clock and 6 o'clock positions, the heel could push down and the torque is transfered to the BB via the mini-drivetrain to the BB thereby eliminating the dead spots in the revolution.

Theoretically it may work but I seriously doubt there is any net increase in overall efficiency considering so many extra pieces.

Plus I cringe at the thought of the Q-factor. And no pedaling through a corner due to little ground clearance.


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PostPosted: Fri Jan 18, 2013 10:01 am 
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Extension of the ankle towards the end of a stride (6 o'clock position) is deeply engrained in the human physiology. Anything that substantially alters that motion sequence is likely to cost efficiency.

Yey for experimenting, though.

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Posted: Fri Jan 18, 2013 10:01 am 


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