A Hand Cranked MagnetoGenerator

I've got one of those. Didn't cost a fortune from "Fair Radio Sales"
about 10 years ago.

Mine outputs ~200 volts peak to peak, open circuit @ ~100 hz. It has
a two pole armature that rotates between the horseshoe pole pieces,
with a set of slip rings to pull the power off. The waveform is NOT
sinusoidal. There are a set of brass gears that give a (eyeballing it)
~1:3+ speed increase from crank to armature. It will dimly light a 7
watt 125 VAC lamp. (that is one can see the filament glow, but
nothing like a full 7 watts).

I got one of the old, relatively large, horseshoe magnet types. Fair
Radio also had some compact "field telephone" magnetos - round and
small.

 

On Sun, 14 Aug 2005 11:12:34 -0700, "Watson A.Name - \"Watt Sun, the

Snipped

Interesting links

I'll bet mine has a set of weak magnets. We were having a contest to
see who could get the bulb to light the brightest, in the lab - that's
where the 100 HZ came from. I imagine that they used some iron pole
pieces for the magnet and it would lose flux over the years.

Sometime I'll have to hunt for it and see what some rare earth magnets
can do.

 

Greetings,

I'm trying to locate information on the hand crank magneto generator
used in vintage phones:

how they were constructed
what charge was produced and how was it used.

I tried Google but my query returned little.

rg

 

You should first look for antique telephones. I know of several dealers
(yes, dealers) who sell such stuff, and they are members of the ATCA,
Antique Telephone Collectors Ass'n. The last meeting I went to they had
old porcelain "Bell System" signs for $400 to $1200, and I asked one guy
who bought one how those prices were, and he said they were reasonbable.
So don't expect to get a magneto for cheap. A decent wall telephone
with a hand crank costs $200 on up, so figure out how much you wanna
spend.

www.atcaonline.com and try the links to member pages.

http://207.158.222.209/ericsson/links.htm some links to other tel
websites

Ekkehart Willms website has some amazing items, more than just
telephones. Like the Art Deco radio for $$$$$! I saw it at the last
meeting, and it's awesome.(# R7 here
http://www.vintagephone.com/EWRad.htm) Yes, his name is spelled that
way. I also saw him play the Edison cylinder record player with the big
tulip horn, and it's amazingly loud for not having an amplifier.
http://www.vintagephone.com/EW.htm

The generator puts out about 90VAC at about 20 Hz, depending on how fast
it's cranked. It's bridged across the phone line and when cranked, a
switch engages and connects the rotor to the line. Just a few magnets
and a armature with wire and slip rings.

 

I see that there is a lot of interest in this device. I was hoping to
get an illustrated parts breakdown so that I can get a better
understanding of whats going on when the crank is turned.

If anyone has one or know where I might view a print, I would
appreciate the tip.

rg

 

My cat could give you more information that I can - sadly (and I still
feel bad about it) I connected one lead from one of these to a metal
plate, and the other lead to a saucepan of milk - cat stood on the plate
and started drinking the milk - I wizzed the handle and he jumped

David - who doesn't feel bad though about all the local kids he talked
into holding the leads from his genny

 

snipped

Lot of pictures of old magnetos no drawings that I could find.
Chances are there's an on-line patent or two with the drawings, but
good luck locating it.

The magneto is a basic permanent magnet alternator or dynamo. There
should be a lot of drawings for those - lots of folks wanting to build
them for small wind or water power plants.

 

Had this cat that insisted on climbing through the window. It was a
"city cat" and the owner had just left the window open. When I
acquired the cat (owner went to work at the CIA) the windows were
screened and there was no way . . .

A spark coil with a couple of wires nailed to the sills cured that cat
- she needed two lessons - to break a lifetime habit.

 

With a two pole horseshoe magnet that covers (maybe) 120 degrees of
rotation . . . There's a big bare spot with no generation. That and
less than optimal pole pieces or armature.

Wave was sort of like a hemisphere with a spike (like a sine wave)
superimposed on the first part of the waveform. But that may be unique
to my magneto.

If your goal is to raise worms . chances are the waveform isn't all
that critical. Ring phone bells - ditto.

 

It's funny you should mention that. Years ago, I was watching a WWII
era film and the crank genny was used very effectively in an
interrogation technique involving the mans' pride and joy. "Ouch!"

rg

 

A print for this unit, as far as I'm concerned, is not in cyberspace.
Schematics abound showing the phone circuits but, keeping in mind the
fact that this assembly is vintage analog and omitting the phone
circuitry, I have determined from descriptions by Watson and default
that what we have left is basically an unorthodox P.M.G.

What I was trying to uncover was why the waveform is not sineusoidal.
I'll take a stab at that too.

I think that the reason is because of the horseshoe magnets providing
the magnetic field. The highest concentration of flux is at the poles
of the magnets and does not follow the arc of the rotor coils. When the
rotor coils are at 90' to the plane of the horseshoe poles, the coils
aren't cutting lines of flux, they are running with them.

rg

 

I agree. I think this unit will remain in the realm of novelty however,
raising worms is justification enough to keep one handy;-)

I read that the Military has adapted it, in a handheld version, to
charging high tech-low voltage DC field equipment such as PDAs', cell
phones and, If I read correctly, 12 volt batteries.

Thanks,

rg

 

It sure seems like it would make more sense to spin one of those
ultra-strong new magnets between some kind of stator windings.

Thanks!
Rich

 

snipped

Doubtless the military has some fancy stuff.

There was a "survival" radio advertised that was pretty neat. The
power was stored in a large spring one wound up. The spring powered
a dynamo and was regulated so that if more power was needed the spring
unwound faster - if the music, for instance, had a lot of bass the
spring would spin the dynamo faster.

Stepper motors make good slow speed, low current, alternators. Good
for lighting leds as a demonstration.

http://www.otherpower.com/pmg2.html Interesting low speed homemade
wooden alternator. He could probably more than double the output if
he mixed some powdered iron in his epoxy on the field coils. Claims
it can power a 120 volt tube type stereo that dissipates 300 watts,
powered with an electric drill.

 

I figure peddling my bicycle I probably generate ~100 watts average
and can keep that for an hour or two with no problem. I think it
would take a lot of work to turn a hand crank at that level long
enough to charge a car battery. Say 9-10 amps into a 60-70 amp hour
battery?

Leg power maybe, but I'd think solar cells or small gas generator
first.

 

default wrote:

I share the curiosity about how modern high power magnets would perform
instead of the horseshoes. The best application I can think of at this
time is to boost charge a weak car battery, anywhere! I would have one
in my trunk dedicated to that function.

rg

 

I doubt that you would be able to crank one enough to turn over a car
engine. Have you ever hand cranked an ice cream churn? Think about how
little electricity it takes to run an electric one. Multiply that times
the additional energy needed to to turn over a modern high compression
engine over the efficiency of the charging process.

--
Link to my "Computers for disabled Veterans" project website deleted
after threats were telephoned to my church.

Michael A. Terrell
Central Florida

 

snip

Some related sites with pedal power outputs

http://www.los-gatos.ca.us/davidbu/pedgen.html
Burst output: 25 amps at 17 volts (425 Watts)
30 minute average output (back when I was in shape) 150 Watts

http://www.ibiblio.org/pub/academic...es/homepower-magazine/archives/23/hp23p48.txt
A modestly fit person can expect to
generate about one tenth horsepower (roughly 70 watts) for a brief
period. For normal regular use a generator capable of producing
50 watts or more is quite adequate. If you are a cyclist interested
in serious training, a generator capable of 100 watts or more is
desirable, PM generators ranging in size from 60 watts to 200 watts
are readily available and can be obtained with the bike generator
options described below.

http://www.otherpower.com/otherpower_experiments_bicycle.html
Although I have not tested this alternator for exact speed vs output
information, it seems to start charging 12 volts at approx 80 rpm.
When coupled to the bike, I was able to generate
5 amps(60 watts) in a leisurely way, and if I pedaled as fast as I
could, I'd get about 10 amps(120 watts). This
seems to be in line with claims we've seen for other peoples plans,
although it seems clear that with a higher gear
ratio, one could generate significantly more with this alternator.

 

I took a hard disk drive apart and removed the platters. I connected a
red LED the leads of the heads that go to the voice coil. When I
wiggled the voice coil back and forth in that strong magnetic field, it
lit the LED, easily. Also, some of the HDD motors are permanent magnet
and when spun will light the LED.

 

Forget it. Your arm muscles would give out after a few minutes. 14
volts output at an amp is 14 watts, figuting 70 percen efficiency, 20
watts imput to the gen. You can't do that for long; a bicyclist can't
put out a sustained hundred watts using his legs, only for a short
burst. The thigh muscles are the largest and most powerful muscles in
your body.

At 1 amp, it'll take you an awful long time to charge a car battery.