Homopolar motor

posted Nov 10th 2009 10:00am by Mike Szczys
filed under: misc hacks

homopolar-motor

Slow day at the office? Here’s a trick that’ll make your coworkers smile. Dangerously Fun has a guide to build a homopolar motor from a battery, copper wire, and magnet. A homopolor motor doesn’t rely on electromagnets in an armature changing their polarity to force a rotation movement compared to stationary magnets. Instead, they use an electrical current’s orientation to a magnetic field to provide a repulsive or rotational force. In this implementation, the current moves through a loops of copper wire from one pole of a battery to the other. A rare-earth magnet on one pole of the battery provides the magnetic field.

After the break we’ve embedded video of this simple example as well as a few more complex homopolar examples such as a five speed version. The motor in action certainly brings a smile to our faces and places this firmly in the useless machines family of hacks.

Oops, this next one’s NOT a homopolar motor. Thanks Fallen.

[Thanks Paine]

Comments [35]

tagged: homopolar, magnet, motor, rare-earth, useless machine

Reader Comments

neato, i’m gonna have to make one of those with my little girl, she’ll love

Posted at 10:14 am on Nov 10th, 2009 by vikki

The last one isn’t a homopolar motor.
The windings are commutated.

Posted at 10:17 am on Nov 10th, 2009 by Fallen

Cool, I have not seen this before

How long will the AA battery last ? and how hot does it get ?

Posted at 10:24 am on Nov 10th, 2009 by Mark Jones

@Fallen

Yes, it is a homopolar motor, there’s no commutation.

Use the right-hand rule for Lorentz force. Lay your palm out, with your thumb at a 90 deg angle to your fingers. Put your fingers in the direction of the magnetic field, thumb in direction of current, and your palm pushes the direction of the force.

In the last video we can assume (for example) that the current is flowing clockwise and the magnetic field is pointing up. Using the Lorentz force you see that the bottom of the ring is pushed away from the camera, while the top of the ring is pulled towards the camera. This force continues as the ring begins to rotate.

Posted at 11:06 am on Nov 10th, 2009 by Charper

Mere seconds after seeing this I grabbed a AAA battery, some magnets from the back of some LED flashy things, a coat hanger and a piece of solder and surprised my wife when I showed her my own working homopolar motor!

Now, of course I have to make a nice one to sit on my desk!

THANK YOU HACK A DAY and the creators for bringing this to me!

Delight! Delight I say! :D

Posted at 11:07 am on Nov 10th, 2009 by strider_mt2k

and then off course it flies off at 40k rpm into your eyes kekekkekeke

Posted at 11:23 am on Nov 10th, 2009 by kirov

How does the money stick to the magnet in the second video?

Posted at 12:03 pm on Nov 10th, 2009 by adamziegler

Oh, these are my designs :D
you can see videos here:
http://www.youtube.com/watch?v=zOdboRYf1hM
http://www.youtube.com/watch?v=Kto3JGQs83M&feature=related

The battery will last only some minutes (maybe about ten or so) I started to use rechargable batteries for that, but some of them died forever.

Its simple, but not effective :)

Posted at 12:37 pm on Nov 10th, 2009 by danky

@adamziegler it is Canadian money. I wondered the same thing until he mentioned the two dollar coin.

Posted at 12:44 pm on Nov 10th, 2009 by David Major

I usually do the NiFeB mag + AA + wire + screw trick to show a homopolar magnet, but this one with a solid wire as the rotor is art. Kinetic art!

Posted at 12:47 pm on Nov 10th, 2009 by PocketBrain

Heh. NeFeB… stupid typos.

Posted at 12:48 pm on Nov 10th, 2009 by PocketBrain

@PocketBrain:
That’s still wrong, I think.
“Ne” is “Neon”. It doesn’t like to form bonds.

Posted at 2:17 pm on Nov 10th, 2009 by r_d

I got an A+ at the Phisics class many years ago with this thing :D

Posted at 2:20 pm on Nov 10th, 2009 by cigraphics

you just found this ? So tell me why did you chose to live in the cave most of you life, since you escape from basement you was locked in by child molester for 10 years ?

Posted at 2:38 pm on Nov 10th, 2009 by therian

i would make one but i seem to be haveing a hard time finding a magnet :(
this is definetly SWEET and COOL

Posted at 2:43 pm on Nov 10th, 2009 by monkeyslayer56

@therian,
Why do you try so hard to make people dislike you?

We did this in school ages ago. it was fun then. looks fun now. thanks for sharing.

Posted at 2:59 pm on Nov 10th, 2009 by captain obvious

“I got an A+ at the Phisics class many years ago with this thing :D”

Sadly, it seems you lost the spelling bee! ;)

Posted at 6:06 pm on Nov 10th, 2009 by Patrick

@Patrick

Love it. Whilst this is the second homopolar motor ive seen, this one is much cooler!

Posted at 6:40 pm on Nov 10th, 2009 by Chris

It is far from new, but still cool. I thought the first time I read about this a long while back that it was b.s., then I tried it. I only had square neodymium magnets so it did not work right but it showed very clearly that the concept worked. It rotated poorly, still worked tho! Square wheels do suck after all. An example of one of these motors doing work (something useful other than education.) would be awesome. Probably hard to do with a motor that appears to have slightly more than zero torque.

Posted at 7:21 pm on Nov 10th, 2009 by mic

@Charper

There is commutation. When making that type of motor the insulation is stripped from half the wire, so it conducts every 180 degrees.

Posted at 7:24 pm on Nov 10th, 2009 by Fallen

its NdFeB, some peope call em NIB for neodymium iron boron. i wish i had one lying around that had the poles arranged correctly. i dont wana break my hard drive magnets in half, and the other ones i have are way too small.

Posted at 7:43 pm on Nov 10th, 2009 by jeditalian

looks like the magnet has to conduct electricity, so i might try wrapping a round black magnet with aluminum foil or something when i find one. sure it wont be as fast cuz it wont be neo, but this is cool nontheless

Posted at 7:54 pm on Nov 10th, 2009 by jeditalian

@jeditalian: if you magnet doesn’t conduct electricity, just put a washer or coin on top of it and touch the wire to that. It is not critical that the current goes through the magnet, it just has to be flowing.

Posted at 9:05 pm on Nov 10th, 2009 by Dan

You can never get enough motor and engine design stuff.

I’d like to see this type in a more powerful design where it produces energy for a bigger system efficiently.

Posted at 1:00 am on Nov 11th, 2009 by tj

we need a usb version

Posted at 5:31 am on Nov 11th, 2009 by Tulio

@Fallen:
That still wouldn’t make it commutated.

Great stuff, especially liked the 5 gear version on youtube. Crazy ferromagnetic space-bucks.

Posted at 6:27 am on Nov 11th, 2009 by le'chef

And rebuttal. Didn’t realize which motor we where talking about… That’s what I get for shooting the yapper on the internet, I guess.

Posted at 6:31 am on Nov 11th, 2009 by le'chef

Dear god why do people put these things on sites jammed with advertising, pop-ups and useless junk?!

Posted at 11:03 am on Nov 11th, 2009 by James

you just found this ? So tell me why did you chose to live in the cave most of you life, since you escape from basement you was locked in by child molester for 10 years ?

Posted at 2:38 pm on Nov 10th, 2009 by therian

_____________________________________________

lmao!!!!!

Posted at 11:27 am on Nov 11th, 2009 by MysticShadow

I just got my mind blown because I’ve spent my entire life knowing that magnets don’t stick to pennies (I remember from experimenting with magnetism as a kid)

Turns out our (Canadian) pennies have been able to stick to magnets since 2007…

Posted at 1:27 am on Nov 12th, 2009 by Frank McSteez

if you want to build the last one, have a look at http://fly.hiwaay.net/~palmer/motor.html
the trick is in step 2: leave some insulation (that is the clear coating) on one of the wire-ends, so that the coil shuts off for half a turn.

Posted at 7:07 am on Nov 12th, 2009 by tantris

@James: here’s your hack for today; Firefox and Adblock Plus

http://www.mozilla-europe.org/en/firefox/
https://addons.mozilla.org/en-US/firefox/addon/1865

Posted at 12:25 am on Nov 13th, 2009 by v.dog

@v.dog: Amen! Firefox/Adblock Plus have made the net a nice place to visit.

Also, as a cave dweller I had never seen such a motor before and I think this post is great. Can’t wait to impress the nephews with it!

Posted at 5:01 pm on Nov 14th, 2009 by mjrippe

why does the homopolar wire spin?

Posted at 3:37 pm on Nov 17th, 2009 by Mrs.Shorty

This Blows
.. my mind! lol.
right hand rule: say the electrons are going up to + terminal. stick yo right thumb up. your fingers are pointing in the direction of the newly created spinning magnetic field. if u could point your right thumb up 4 the other wire, and see the magnetic fields like wheels, both rotating ccw, put a wheel in the middle, it will go clockwise. the magnet is so strong that it makes the battery a big str8 magnet, but where those fields interact is where i get lost, because up and down are n and s, rgw wire mag field is like a wheel one side n one side s, spinning 90degrees to the updown n s battery, and the magnetic fields r acting like invisible gears turning. the 5 speed rig is just mindblowing. anyway that 90degree magnetic field interaction cuts down on magnetic drag/ lockup/pull/ friction.. but i believe also reduces the ability to do real, useful, harnessable w0rk. if you had 2 or more normal 2polar mags spinning where N attracts S attracts N, you could transfer mechanical energy, without the problem of worn out gear teeth, since the gear teeth are magnetic instead of material. but try putting those magnets like spinning [N-s] o [s-N] spinning, where o is a coil. monitor the electrical signals coming from the coil. i’d like to know what happen. or where o is an up-down magnet like the battery magnet combo. im pretty sure it would resonate trying to seek equilibrium. . as long as the[ns] [sn] magnets are spinning, you’ve built a 3 magnet vibrator! but it can be much more useful than a vibrator, if you put your mind to it.

Posted at 11:32 pm on Nov 18th, 2009 by jeditalian

Homopolar motor

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