## New motor type?

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scikidus
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### New motor type?

I can't find anything like this online, so I have to assume that no one's done it before.

Basically, it's a simple push=pull motor which uses iron-core electromagnets with a twist: the iron core of each electromagnet is part of the circuit.One terminal of a battery is connected to an iron-core electromagnet. The trailing wire from the electromagnet is attached to the iron core of the electromagnet. One electromagnet is fixed to the base of the motor, and the other electromagnet is placed upside-down in a tube surrounding both electromagnets. The top electromagnet is free to move. The two iron cores, when at rest, touch each other, completing the circuit.

When the circuit completes itself, both electromagnets form magnetic fields, and due to their orientation, repel each other. Since the bottom electromagnet's coil is fixed, the top electromagnet to repelled upward. However, this breaks the circuit which si supplying the electromagnets, and with nothing repelling the two electromagnets anymore, gravity pulls the top electromagnet back down again, touching the two iron cores, completing the circuit, and repeating the cycle.

From what I'm imagining this push-pull motor would be very fast, but its amplitude would be very small. More importantly, would this idea work, or have I gotten something terribly wrong?
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Durandal
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### Re: New motor type?

A... um... diagram would be nice.

Anyway, from your descriptions of the actions, it wouldn't work that well. For one, the circuit would be broken instantaneously once they move apart, which would, as you said, give a very small amplitude. Also, the acceleration down due to gravity wouldn't match the acceleration up due to the magnets, and for a motor you need to have very precise timing (as in, SHM precise). Furthermore, the force of gravity alone would not generate very much power at all. It would also be very slow.

Also, I'm not sure on this one, but I think there might be a magnetic braking force according to lenz's law as the loop increases in size on the way up... although again, not sure. I've never considered a scenario such as the one you described with regards to lenz's law.

So yeah, not very feasible.
Last edited by Durandal on Mon Jun 22, 2009 4:15 pm UTC, edited 1 time in total.

scikidus
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### Re: New motor type?

Durandal wrote:A... um... diagram would be nice.

*is desperately trying to find diagram software, preferably online*
Durandal wrote:Anyway, from your descriptions of the actions, it wouldn't work that well. For one, the circuit would be broken instantaneously once they move apart, which would, as you said, give a very small amplitude. Also, the acceleration down due to gravity wouldn't match the acceleration up due to the magnets, and for a motor you need to have very precise timing. Furthermore, the force of gravity alone would not generate very much power at all. It would also be very slow.

Except that they cease to be magnets when the circuit is broken. After the initial repel, you simply have a coil of wire sitting above another coil of wire with nothing supporting it. It fals completes the cirucit, and goes back up again.
Durandal wrote:Also, I'm not sure on this one, but I think there might be a magnetic braking force according to lenz's law as the loop increases in size on the way up.

So yeah, not very feasible.

It's more a thought experiment, I suppose, than anything. In the meantime, I'm going to try to Photoshop together a diagram.
Happy hollandaise!

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Durandal
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### Re: New motor type?

1) I didn't mean that gravity was fighting against the magnets.

2) They would accelerate upwards far faster than gravity would accelerate them downwards (9.8 m/s2), thus the motor would not be in simple harmonic motion. Although you may be able to rig them to mimic the acceleration of gravity... see number 3.

3) 9.8 m/s2 is a ridiculously small acceleration in motor terms. Veeeeeeeeeeeery slow.

4) Gravity provides very little power, proportional to the weight of the electromagnet.

scikidus
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### Re: New motor type?

Durandal wrote:1) I didn't mean that gravity was fighting against the magnets.

2) They would accelerate upwards far faster than gravity would accelerate them downwards (9.8 m/s2), thus the motor would not be in simple harmonic motion. Although you may be able to rig them to mimic the acceleration of gravity... see number 3.

3) 9.8 m/s2 is a ridiculously small acceleration in motor terms. Veeeeeeeeeeeery slow.

4) Gravity provides very little power, proportional to the weight of the electromagnet.

All true. I'm trying to think of a use for such a motor.

Here's my crappy mock-up:
I probably got a polarity wrong. Oh well.
pushpullmotor.jpg (53.72 KiB) Viewed 1987 times
Happy hollandaise!

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You, sir, name?
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### Re: New motor type?

Durandal wrote:2) They would accelerate upwards far faster than gravity would accelerate them downwards (9.8 m/s2), thus the motor would not be in simple harmonic motion. Although you may be able to rig them to mimic the acceleration of gravity... see number 3.

Yeah, gravity is effectively linear at the distance differences involved, but magnetic forces vary greatly with the distances involved.

You have
$F_g = const, F_m \sim C\frac{1}{r^2}$

You won't get sinusoidal oscillation, but you will get oscillation. I ran a simulation, and this is what I got:
Attachments
disp.png (5.46 KiB) Viewed 1925 times
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Firnagzen
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### Re: New motor type?

Look into how a basic electric buzzer works, you've basically reinvented that, albeit using two electromagnets as opposed to one electromagnet and a iron lump.

Sorry.
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Phoenix112358
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### Re: New motor type?

Firnagzen wrote:Look into how a basic electric buzzer works, you've basically reinvented that, albeit using two electromagnets as opposed to one electromagnet and a iron lump.

Sorry.

Ah, beat me to it.

When I was reading the OP's description I thought: "Hey.. this sounds surprisingly similar to the example of how a particular school bell worked when we covered solenoids."

keeperofdakeys
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### Re: New motor type?

i have always had the crazy idea of replacing the current internal combustion engine with permanent magnets on the piston heads and electro magnets above, switching polarity to achieve motion, probably use too much power from friction

zalzane
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### Re: New motor type?

keeperofdakeys wrote:i have always had the crazy idea of replacing the current internal combustion engine with permanent magnets on the piston heads and electro magnets above, switching polarity to achieve motion, probably use too much power from friction

It would have the same friction as a standard ICE (internal combustion engine), but in order for your design to be feasible, it would have to have less waste energy/heat than current electric motors.

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### Re: New motor type?

zalzane wrote:
keeperofdakeys wrote:i have always had the crazy idea of replacing the current internal combustion engine with permanent magnets on the piston heads and electro magnets above, switching polarity to achieve motion, probably use too much power from friction

It would have the same friction as a standard ICE (internal combustion engine), but in order for your design to be feasible, it would have to have less waste energy/heat than current electric motors.

I sincerely doubt it would, though. The design has several shortcomings over regular electrical engines:
• It is fixed-speed. Many electrical engines can run at any speed so long as it has enough juice. Piston engines are bound to the harmonic frequencies of the pistons, and as such require a gearbox, and gearing induce more friction still.
• Piston engines bleed energy from the vibrations their non-balanced motion causes.
• You'd experience serious eddy current braking if the engine housing is made out of a conductive material.
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