Date: Wed, 01 May 2002 08:49:48 -0400

Author: Wolfgang Rueckner

Subject: Re: Bicycle Generator 5K40.83


Thanks for sharing your experience with your generator, Martin.
Rather than going to a 120 VAC inverter, which you say was hopelessly
inefficient, how about a DC to DC converter to bring the voltage up
to 120 VDC and add some large capacitors to take care of the voltage
variations and spikes. If all that becomes part of the generator
"package," it shouldn't complicate things conceptually. But of
course you wouldn't be able to power household items like TVs, etc.
-- just light bulbs and toasters.

>I bought a low RPM 1 kW 12 V permanent magnet generator from
>They also have a smaller Wattage model which would probably also
>work fine. The 1 kW is overkill. I had looked into old car generators
>but they seemed to deliver only 200-300 Watts and I was afraid that
>was too small. They would probably work fine. With this generator I
>use a bank of eight 12 V 50 W bulbs which are sometimes called
>Marine or RV bulbs. I also have a small B&W 12 V TV which can
>be attached.
>It works, but there are some problems that I would like to solve to
>make it better.
>1. It would be nice to start with one bulb, then switch in the second
>bulb, then the third, etc, so that the pedalling is easy and then gets
>progressively harder. However, with too small a load, the voltage
>spikes up and burns out the connected bulbs. I have to have a
>minimum of three or four bulbs in to keep the voltage around 12 V
>or else I lose bulbs. It depends on how hard the student pedals
>under light load. I would like to find a way to clamp the voltage to
>12V without complicating the circuit much. One idea is to add a
>discharged 12 V car battery but that complicates things conceptually.
>2. Connecting more bulbs makes it very hard to pedal and makes
>the illumination very uneven. It is very hard to deliver power from
>the pedals continuously under heavy load. The exercise bike has
>a flywheel but no gearing, and the flywheel is not enough to even
>out the stroke.
>3. I wanted to be able to connect an inverter so that I could go
>up to 120V AC. I connected a cheap 1 KW inverter but it is
>so lossy that I couldn't get any useful power out. I need to try
>with a more efficient smaller inverter. The uneven stroke
>and voltage swings may be a problem though.
>Despite these limitations it does get used a lot and is liked
>by the instructors.
>Martin Simon
>>I am seeking recommendations for a good permanent magnet, low
>>voltage DC motor to be used as a generator with an exercise bike.
>>Does any body do a Bicycle generator?
>>Can you tell me anything about the motor you use, the
>>specifications, maybe the make and the model?
>>Do you have any gearing on the motor or the bike?