Date: Wed, 05 Apr 2000 15:19:50 -0700

Author: Martin Simon

Subject: Re: Bicycle Generator



I was way behind on my Tap-L reading so I'm just catching up
to this thread. I initiated a similar thread a year ago when
I asked for help finding a dc motor/generator that would put
out 120 V and about 1 HP for this demo. I had looked at C&H
and other sources for new and used motors and couldn't find
anything suitable.

The advice from the group was to go to 12 Volts and that's
what I attempted to do. I looked into old car generators
but they seemed a little too wimpy (150 W or less) and I'm
not sure if the RPMs would be a good match to the thrift
store exercise bike I intended to use.

I finally found something I thought would work from
Windstream Power Systems, 1-802-658-0075.
They sell a 12 A at 12V generator for about $198
(with a pedal set if you want for extra $). They also
sell a 40 A at 12 V generator which I bought for around $450,
more than I expected to pay, but worth it if it makes
a reliable heavily used demo.

How well does it work? It really takes a lot out of you to
keep six 50W (12 V) light bulbs going and you can't do it for
very long. I would like to start with one light bulb and then
screw in more one at a time. Problem is that the voltage shoots
up too high and burns out the bulb. With three 50 W bulbs in,
the voltage is fine and additional bulbs can be screwed in one
at a time. Another minor problem is that because of the pedals,
the drive is uneven. At the top of the stroke the bulbs go dim.
I do have a flywheel but it is not enough under load. A bicycle
built for two with offset pedals would work better.

It would be nice to clamp the voltage at 12 or below. Anyone know
of something like a 12 V zener diode that can handle 50 W or so?
One idea is to use a discharged motorcycle battery. If the voltage
goes above 12 Volts it will start charging the battery.

Martin Simon