foot power

[Sameer Verma]

On Thu, Jan 27, 2011 at 6:41 AM, Ian Stirling <olpc at mauve.plus.com> wrote:
> 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.
>
> http://cgi.ebay.co.uk/Lifepo4-A123-Cell-26650-2300mah-3-3v-battery-3-Pcs-NEW-/260726135323?pt=US_Batteries&hash=item3cb47d1a1b
> 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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>

Looking at this thread reminded me of clocks with weight pulleys. I
saw one recently outside UCSF hospital.
http://www.flickr.com/photos/revger/4381874187/
The weight unwinds the pulley slowly. This is also seen on roasting
jack (For those who attended the OLPC SF dinner/bbq, the Kleiders have
this at their house)

http://en.wikipedia.org/wiki/Clock_jack

Will such a wind-up mechanism work?

Sameer