Building a better human powered battery charger

[Norm]

   The exercise bike has a 20 inch bike wheel

the original tire was a solid sponge rubber, not

very good for a friction driven generator to be

running against, luckily a regular bike tire and

tube fit on it, had to drill a hole in the rim

for the tube stem...minor detail.

  I made an 1 1/2 wood pulley for the little

generator, so everthing considered I calculate

that if I pedal at a 60 rpm rate, the wheel spins

at 120. This would be about 7mph and the generator is spinning about 1920rpm (crank to

generator ratio 1:32)

   This seems to be very inefficient....I'm

putting about 800Ma into 6 700Ma AA batteries

at about 9.5 v0lts or about 7 watts.

  I'm handcranking this and exerting as much

energy as I was in physical therapy at 50 watts

according to the meter on their machine.

  I figure that if I hooked a 30 volt Ametek to

the wheel with a 3 inch dia. pulley then pedaling

at a 7mph rate...60 rpm the Ametek will be spinning about 1000 rpm and I'll be charging a

12 volt battery at least 30 watts??

  Is my math about right? ....over or underestimating ?

  What is the best operating range for a 30 volt

Ametek?

 

[Boss]

I am interested in this project as I too built an exercise bike with an alternator.

The system I built was more for exercise than electrical output.

I haven't been able to measure the output, because my alternator is an automotive type and it uses much of the energy of pedaling to energize the alternators field coils and I only have a direct connection amp meter.

I knew the power output is low, but from your numbers I can see that it is very low.I am thinking of building a little axial flux alternator for it, but if I can't substantially increase the output I may just leave it as it is.

 

[Norm]

It looks like at about 400 rpm the Ametek will

produce about 64watts...may even have to make

the pulley larger to slow it down to where it

won't be so hard to pedal.

Should have some results in a couple of days

soon as I get New Year out of the way.

......Happy New Year BTW to you and whoever is

reading this post!