foot power

Ian Stirling olpc at
Thu Jan 27 09:41:28 EST 2011

Carlos Nazareno wrote:
> Hey guys.
> I haven't taken that much look into foot pedal chargers and do know
> what their internals look like -- I just remembered coming across the
> link I posted so I shared The efficient way to do a foot pedal powered
> generator would probably be to have a small weighted wheel spin as a
> dynamo when you step on it?
> You just keep pumping on the pedal to keep the wheel spinning and it
> shouldn't take much effort, the wheel's momentum should keep power
> flowing.

Basically, never do mechanically what you can do electrically.
There are cells now which are reasonably light, cheap, and can take
30W charge.
for example.

A flywheel is going to be _lots_ heavier.

My design that I posted about earlier in this thread had basically a
'gearbox' electronically that optimised charging of the battery at
the optimum biodynamic speed, and then used the generator as a motor
to pop up the pedal back to the operating position.

It was designed to get enough charge to charge a mobile phone battery
fully by an adult over 3-5 mins.
This is only at best 50-30W or so.

If you want something to generate power efficiently, you need to use
both legs - either a cycle, or a step-machine.
Cycles are rather more efficient than step machines though
the mechanism is pretty much inherently bulky.

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