On Thu, Jan 27, 2011 at 6:41 AM, Ian Stirling <o...@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. > _______________________________________________ > Devel mailing list > Devel@lists.laptop.org > http://lists.laptop.org/listinfo/devel > > >
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 _______________________________________________ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
