#54337
01/29/2002 8:40 PM
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Joined: Jan 2001
Posts: 13,858
Carpal Tunnel
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Carpal Tunnel
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Posts: 13,858 |
Today I was telling wow about an incident which involved a solenoid. Every one of us who has ever driven an automobile, has had to use one to start the motor. But I suspect that only a few have heard the term before.
o[le[noid 7sb4l! n.d#, s9l4!38
n.
5Fr sol=no:de < Gr sblcn, a tube, channel (< IE *tul3 < base *twb3 > Sans tdVa, a quiver) + eidos, 3OID6 a coil of wire, usually wound in the form of a helix, that acts like a bar magnet when carrying a current: used in brakes, switches, relays, etc.
so#le[noi4dal
adj.
When you start the motor, turning the key all the way closes a circuit that activates a solenoid using current from the battery to operate starting motor. When motor has started, and the key springs back partway, the battery is no longer connect to the starting motor. I had a solenoid jam closed, and it burned out my whole electrical system. We were up in Canada, and you would not believe the trouble we had. The Toyota dealer would not touch it until he got authorization in mail from my insurance company. We had to rent a car to get home. And a month later I had a ride to recover my vehicle in a Canadian 8 passenger plane in turbulence so violent that even the pilots were airsick.
If for no other reason, that experience fixed the word "solenoid" in my memory.
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#54338
01/29/2002 9:05 PM
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Joined: Oct 2000
Posts: 5,400
Carpal Tunnel
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Carpal Tunnel
Joined: Oct 2000
Posts: 5,400 |
back in the days when i was a mechanical techy.. we has several "daffynitions" of words for things we worked with.
what is a solenoid?
a painful condition that develops on the bottom of motor that have been idling too much!
what blows fuses?
Oh-- so bad..
easy girls and/or queer electrons. (and maybe we should add, interns named Monica?
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#54339
01/29/2002 9:11 PM
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Joined: Dec 2000
Posts: 13,803
Carpal Tunnel
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Carpal Tunnel
Joined: Dec 2000
Posts: 13,803 |
Dear Dr. Bill
A solenoid and a relay perform the same function. They switch electrical contacts as a result of some external signal. I seem to have it stuck in my tiny little brain that the difference is that in a relay the signal is electrical and in a solenoid it is mechanical. Thus, the pressure switch that turns on the submersible pump in my water well is a solenoid, since the signal that controls it is water pressure on a diaphragm in the switch and the power to the pump is switched. Your description of the solenoid in a car suggests that it is controlled by an electrical signal through the keyed ignition switch. Perhaps it is merely that the term solenoid is just an older term that has become fossilized in automotive usage, much as the capacitor somewhere in there is known by the older term condensor. Any ideas?
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#54340
01/29/2002 9:41 PM
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Joined: Jan 2001
Posts: 13,858
Carpal Tunnel
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Carpal Tunnel
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Posts: 13,858 |
Dear Faldage: I can remember in some of my older vehicles the loud thump that used to be heard when you turned the key, apparently closing clutch of starter motor. Ditto on some old washing machines. I never took one apart, but my understanding was that the metal core inside the windings moved powerfully to move something mechanically. Relays don't need much current to change current flow to a different circuit.
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#54341
01/29/2002 11:41 PM
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Joined: Mar 2000
Posts: 11,613
Carpal Tunnel
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Carpal Tunnel
Joined: Mar 2000
Posts: 11,613 |
I've had cars (and may now, for all I know) with a solenoid, though I've never had a clear idea of what they do. Thank you, Dr. Bill.
What I want to know is: why is it pronounced sell-annoyed?
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#54342
01/30/2002 12:04 PM
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Joined: Jan 2001
Posts: 1,156
old hand
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old hand
Joined: Jan 2001
Posts: 1,156 |
But I suspect that only a few have heard the term before.Don't worry, they're still around. It's basically a coil of wire, wrapped around a piece of iron (or some other magnetic material) with an current going through the wire. When the current is in one direction, there is a magnetic field in the centre of the coil. If you have a piece of magnetic material in the centre, it will want to move in the direction of the magnetic field. If you reverse the direction of the current, the piece of metal in the middle will move the other way. So if you use a solenoid as a switch, say to start something, when you apply the voltage, the metal in the middle shoots in one direction (as in a car starter). If you use it with alternating current (and thus alternating the direction of the force in the middle of the coil), the metal thing will move one way and then the other way, over and over again. Most Google searches on solenoid just give you companies who produce them, but here's a webpage with instructions to build your own solenoid at home which will suck up a nail into its centre when turned on. http://cdelker.tripod.com/electric/solenoid.htmlAnyone who's taken physics, or an electricity and magnetism course, will know what a solenoid is. As for the pronunciation, we tend to say SOL-uh-noid (first syllable rhymes with ball) or SOLE-uh-noid (first syllable rhymes with hole) here.
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#54343
01/30/2002 4:57 PM
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Joined: Jul 2000
Posts: 1,094
old hand
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old hand
Joined: Jul 2000
Posts: 1,094 |
build your own solenoid at home which will suck up a nail into its centre when turned on.
Isn't the reverse how one would make a rail gun? If you get a big enough one you could even propel objects into space.
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#54344
01/30/2002 6:01 PM
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Joined: Jan 2001
Posts: 13,858
Carpal Tunnel
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Carpal Tunnel
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In the realm of fantasy, a radio amateur I knew a long time ago, claimed he had a cannon three feet long, aroundwhich he wound a mile of telephone wire, and made an electromagnet so powerful that it lifted a stove in the apartment below up to the ceiling. He was even able to keep a straight face.
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#54345
01/30/2002 6:27 PM
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Joined: Jan 2001
Posts: 1,156
old hand
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old hand
Joined: Jan 2001
Posts: 1,156 |
My husband apparently made such a thing when he was in school, for a science fair project. I suspect it was designed so it wouldn't damage anything seriously. He's a bit bitter about it, something to do with the science teacher not appreciating how much physics was involved. I dunno, you'd have to ask him.
As for propelling objects into space...The escape speed (the speed an object needs to be going to get into orbit) is 11 km/s = 7 mi/s = 40 000 km/h = 25 000 mi/h. It might be tricky to get something moving that fast with a rail gun. Not sure of all the subtleties there, though.
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#54346
01/30/2002 6:53 PM
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Joined: Jan 2001
Posts: 13,858
Carpal Tunnel
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Carpal Tunnel
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Posts: 13,858 |
Dear Bean: I have forgotten all the little bit of physics I used to know. I think the cannon magnet might have lifted a flat iron a foot away, but the idea of lifting a stove ten feel below is absurd.
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#54347
01/30/2002 7:05 PM
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Joined: Dec 2000
Posts: 13,803
Carpal Tunnel
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Carpal Tunnel
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Posts: 13,803 |
My tiny little brain had it backwards. According to M-W on line, in a solenoid, the input is electrical and the output is mechanical. So
A) I thought the output of the solenoid in the car was electrical so what gives here?
and
2) What *do they call it if the input is mechanical?
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#54348
01/30/2002 8:01 PM
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Joined: Jan 2001
Posts: 13,858
Carpal Tunnel
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Carpal Tunnel
Joined: Jan 2001
Posts: 13,858 |
Dear Faldage: the starter motor has a clutch that has to be engaged to crank engine, and solenoid moves one of the disks, I guess. Too bad Geoff isn't here, as an auto mechanic he would really know how to describe it. Washing machines also use one when going from wash to spin. I can't think of any devices that move core to affect current flow. A lot of things that used to use solenoids for light loads now use servo motors regulated by transistor circuits.
Wonderful to have the board so much more active, and windows change so quickly. Bill
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#54349
01/30/2002 8:25 PM
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Joined: Jan 2001
Posts: 13,858
Carpal Tunnel
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Carpal Tunnel
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Posts: 13,858 |
When I was a boy, cars were for strong men only. You had to insert a crank into a small round opening below the radiator, and use a good bit of strength to turn motor over, compressing gas-air mixture in cylinders so spark could ignite it. Never saw it work on first try. And my father derived a substantial part of his income from treating wrist fractures when motor backfired.
Boss Kettering, whose inventions made key starting possible made GM what it is today because it made it possible for women to drive, doubling car sales.
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#54350
01/31/2002 2:53 AM
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Joined: Nov 2000
Posts: 1,289
veteran
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veteran
Joined: Nov 2000
Posts: 1,289 |
Bill, if you remember the days when cars had to be cranked, you must also remember electric cars. James Thurber, in his hilarious accounts of his youth, noted that electric cars were favorites of women. Now we know why; it never occured to me that it was because they were self-starting - I assumed it was because they didn't go fast.
Now we are on the verge of a return of the electric car. Plus ça change ...
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#54351
01/31/2002 3:23 PM
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Joined: Jan 2001
Posts: 13,858
Carpal Tunnel
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Carpal Tunnel
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Dear Bob: There was one rich lady in my town who had a Franklin electric. Spookily quiet. No idea what its round trip distance was. There was also a guy who had a Stanley Steamer. Took over an hour to get steam up. And roundtrip was at times restricted by need to get suitable water. They had acceleration no internal combustion vehicle could match.
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#54352
01/31/2002 4:51 PM
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Joined: Aug 2001
Posts: 2,605
Carpal Tunnel
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Carpal Tunnel
Joined: Aug 2001
Posts: 2,605 |
Stanley Steamer -- a name now used for a carpet-cleaning service, I believe. An interesting case of recycling.
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