spears%nrl-aic@sri-unix.ARPA (06/11/85)
From: William Spears <spears@nrl-aic>
I have just recently come across an interesting advertisement
for a radio that runs on muscle power alone - just turn the crank
10 times and the radio (and encased flashlight!) will run for an
hour and a half.
Judging by the measurements given for the radio, and by looking
at the picture, the crank seems to be about 4 inches long. I assume
a healthy person will generate 40 lbs of force over the circumference
traced by the crank handle (This seems like an absurdly high force).
After 1 turn the person has done slightly more than 80 ft. lbs. of
work (or roughly 110 Joules). In 10 turns roughly 1100 Joules of work
has been done.
Assuming a 1 Watt (1 J/s) radio (and flashlight) the device can
operate for perhaps 1000 seconds (assuming high efficiency). This
is roughly 17 minutes.
My question: How does his radio function for 1.5 hours? Can I assume
a .1 Watt radio? Also I have assumed that the person wants to build up
his/her biceps with 40 lbs of force - but this assumption helps the claim
of the advertisement.
Does anyone have one of these radios?
Bill Spears
NRL-AICthroopw@rtp47.UUCP (Wayne Throop) (06/14/85)
> From: William Spears <spears@nrl-aic> > I have just recently come across an interesting advertisement > for a radio that runs on muscle power alone - just turn the crank > 10 times and the radio (and encased flashlight!) will run for an > hour and a half. [omitted calculation of energy available from hand crank] > My question: How does his radio function for 1.5 hours? Can I assume > a .1 Watt radio? Yes. Since crystal radios draw zero power, it seems clear that a radio can operate on quite modest power levels. I have no way of knowing for sure, but I suspect that the radio in this case is essentially a cheap crystal set, and would be of quite low quality. I'm not sure about the flashlight claim, but imagine it to be quite dim. -- Wayne Throop at Data General, RTP, NC <the-known-world>!mcnc!rti-sel!rtp47!throopw