Bicycle generated power

[Lightspeed]

(27 July 2012, 16:17)Skvez Wrote: Lightspeed

I had been under the impression that a car alternator powered by a bike wasn't very practical because the car alternator needed such a high rpm. However doing a bit of maths suggests it's reasonable:

Typical bike wheel diameter 0.63 m
Typical bike wheel circumference 1.98 m
Reasonable power 'bike speed' 20 mph (miles per hour)
= Reasonable power 'bike speed' 533 mpm (meters per minute)
= wheel rotation of 270 rpm

Given that a car charging alt really needs 2500 to 3000 rpm to get good generation means we need a 10:1 ratio from the bike wheel rpm to the alternator rpm.
If we have a belt on the 0.63m diameter bike wheel we need a 6.3cm diameter pulley wheel on the car alternator.

This seems quite reasonable.

Thanks for doing he math Skvez

As I said it was just a fanciful idea. The pulley method will give the mechanical advantage necessary, as alternators tend to come with drive pulleyse that are in the 6cm dia range. Thanks for evaluating that.

Next question will be power generated. I fear that pulling a big alternator of a deisel Merc for example would be an error. It's designed to generate too much power, and my likkle legs probably would not be up to the task. I'm guessing a puny alternator off a citroen 2cv or off a small moped would be better suited to the task?

I dunno... just some thoughts.

LS