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From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: How to build a windup generator?
Date: Fri, 22 Nov 2002 04:20:26 GMT
NNTP-Posting-Date: Thu, 21 Nov 2002 20:20:26 PST
Steve Andrew wrote:
> Chuck Simmons wrote:
> > MNQ wrote:
> >> Hello All
> >> I am trying to find ways of building a windup electricity generator
> >> to produce approx 10V at afew 10s ma for 2 minutes or more. Can
> >> anyone give me some hints as to where to start from.
> >> Any help/advise would be appreciated.
> >> Thanks
> > 10 volts and 10ma for two minutes is 12 joules. This is the same as a
> > 1kg mass falling through about 1.22 meters. That is some healthy
> > windup spring! We are not talking about a music box spring here!
> > Chuck
> Interesting point. I know that a guy in the UK came up with a clockwork
> powered radio that ran for around 10 minutes before required re-winding. The
> unit is produced in large quantities and distributed throughout Africa as
> well as other places. Given that the radio used a louspeaker and produces
> adequate volumn, I would have thought that it's power requirements would be
> the same (if not greater) than 10v/10ma. Anybody know anything about the
> inner workings of this product ?
I'll ask my oldest daughter about them when I get a chance. She has
spent a lot of time (about four years) in the boonies in central Africa
so she has probably seen them (her own battery powered radio was lost in
some political mess six months after she arrived and she didn't replace
10 volts and 10ma is 100mw. For ten minutes, the total energy is 60
joules. Suppose the device has a long spiral spring. Energy is torque
times angle in this case. Say that 5 newtons is easy enough winding.
That would be about 1.1 pounds force. Take a 10cm crank arm and the
torque is 0.5 newton-meters. This makes an angle of 120 radians which is
about 19 turns. 100mw for the speaker amplifier plus some for the radio
proper might give 30 turns. The only other problem is the gears,
generator and low loss regulator. A flyball governor with no brake would
be OK for this considering the gearing needed to get a generator up to
useful speed. This is workable. The spring is large, of course, but you
don't have to buy batteries so size may be no problem. Die cut or
injection molded gears can be low enough loss. The generator is actually
off the shelf. If this radio is your only entertainment, you do get a
bit of arm execise in the bargain. Oh! Throw some generator and gear
loss in my 30 turn SWAG. See, we are not talking music box springs here.
It's music box springs on steroids.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons firstname.lastname@example.org
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