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Hand cranked military generator modification

how to modify an old military Chinese hand cranked generator?

An old hand cranked Chinese military generator found its way back to us recently. (More on those details tomorrow.)

It was designed to power Army radios in the field. Cutting the 4 pin cable reveals black, red, and white wires. The red and white wires equal 30 regulated volts at 1 amp and the red and black outputs 25 regulated volts at 2 amps.

I'm surprised at how little effort it takes to create 12 to 15 volts. The first experiment I want to do is hook up an additional voltage regulator/charge controller to try charging a golf cart battery.

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Where can I get one of these? This would be great for emergencies!
Comment by Nayan Wed Aug 20 17:18:27 2014

Try to put a sprocket on the axle instead of a hand-crank and hook it up to your training bike. You're bound to get more power output that way. Two legs will beat one arm.

If you have a 1000 Wh battery, and a generator that puts out 50W in the best case, you'll be cranking for at least 20 hours. You rather than me!

Of course you could set up a couple of training bikes with generators and call it a fitness club. Then you can have people pay you to charge your batteries. :-)

Comment by Roland_Smith Wed Aug 20 17:39:19 2014

Is "much little effort" more like much effort or little effort?

I remember thinking it was super hard to pedal hard enough to turn on the lightbulb at the science museum when I was a kid, but I have no idea how much power that actually took. (Power? Current? Not even sure.)

Comment by Amy Wed Aug 20 19:01:26 2014

Nayan --- Google "chinese military hand-cranked generator." For a while, they were being sold here but are not currently:

Roland --- So, the question is, what kind of use would you recommend around a homestead for a generator like this?

Amy --- Thanks for noticing that. Mark and I usually clean up each others' typos pretty well, but I guess I fell down on the job today. :-) That would be "how little effort."

Comment by anna Wed Aug 20 19:32:32 2014

Continuous human power output is quite limited and not lineair.

An average healthy human male might sustain 300 W for a minute or two, 150 W for an hour or so. And maybe 75 W for a whole day.

So you could e.g. use the generator to:

  • Charge a capacitator bank to power some LEDs during a power outage.
  • Maybe keep a laptop running.
  • Charge a mobile phone.

But there are the inefficiencies of a generator/conversion/transmission to consider. I would guess you'd lose at least 20% of the energy you generate.

And the efficiency of the human body itself is around 25% IIRC. So the best thing it would do is probably keep you warm in winter. :-)

Most human power applications use the mechanical power directly. Like bicycles, water pumps et cetera.

Human powered equipment like pole lathes and drills were common before electricity became widespread.

Comment by Roland_Smith Thu Aug 21 02:37:41 2014

In support of Roland's comment:

According to the article, it takes 2-3x more effort to generate electricity to run a motor that runs a machine than to directly power the machine by pedal cranking. Of course, we can't directly crank a light bulb or pedal a tractor very effectively, so it would be nice to be able to charge your battery by human effort in a pinch.

[That Low Tech Mag is a very interesting site that debunks many of the myths we TreeHuggers hold dear. How can it be that a concept becomes "bunk" only after it has been "de-bunked?"]

Comment by doc Thu Aug 21 06:44:20 2014

My guess is that this ranks as a cool doo-dad play-toy than anything practical.

When Mark was wee lad, he was forever taking things apart to see how they work.

dirk (the brother)

Comment by dirk Thu Aug 21 14:52:13 2014