Paging engineers --- ankling engery savings?

Questions about bike hire abroad and everything light bike related. No off-topic chat please

Moderators: robbosmans, Moderator Team

Post Reply
User avatar
elviento
Posts: 1199
Joined: Thu Aug 25, 2005 7:09 pm
Location: In the industry
Contact:

by elviento

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.
Attachments
a505db61jw1e0omz5mntaj.jpg
Fast falcons: http://www.youtube.com/watch?v=j3mTPEuFcWk" onclick="window.open(this.href);return false;
www.falcobike.com
Facebook: falcobikeglobal

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



Kasparz
Posts: 566
Joined: Mon Jul 16, 2007 10:17 am
Location: Latvia

by Kasparz

Cocaine is bad for designing bike parts.

Dozer
Posts: 70
Joined: Sat Jun 02, 2012 10:43 am

by Dozer

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.

User avatar
djconnel
Posts: 7917
Joined: Wed Sep 26, 2007 1:57 pm
Location: San Francisco, CA
Contact:

by djconnel

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.

User avatar
btompkins0112
Posts: 2635
Joined: Fri Feb 11, 2011 3:04 am
Location: Mississippi

by btompkins0112

Yeah, what DJ said....... :noidea:

Anybody got a weight on that crank? :smartass:

kulivontot
Posts: 1163
Joined: Sun May 16, 2010 7:28 pm

by kulivontot

Lol, a wind-up crank based on rotating the pedals?

User avatar
elviento
Posts: 1199
Joined: Thu Aug 25, 2005 7:09 pm
Location: In the industry
Contact:

by elviento

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.
Attachments
fj.JPG
Fast falcons: http://www.youtube.com/watch?v=j3mTPEuFcWk" onclick="window.open(this.href);return false;
www.falcobike.com
Facebook: falcobikeglobal

HillRPete
Posts: 2284
Joined: Tue Apr 12, 2011 8:08 am
Location: Pedal Square

by HillRPete

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.

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



Post Reply