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.
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
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'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.
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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.
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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
try searching for "field telephone"
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 > Greetings,
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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
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.
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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.
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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
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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.
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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.
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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
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Some related sites with pedal power outputs
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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.
perform
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.
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