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Homopolar Motor With Five Speed Manual Stick-Shift

video Homopolar Motor With Five Speed Manual Stick-Shift

This video show how to build a homopolar motor that's really different...it's got a five-speed shifter!

The homopolar motor is the simplest design electrical motor in the world. It uses a battery, a neodymium magnet and a wire. Usually, either the copper wire or the magnet rotates. In this case the battery rotates.

Here, I've used a battery, a neo magnet, and a copper wire wrapped around a coat-hanger. The coat-hanger acts as both electrical connection and support for the hanging battery. Coins are used to change speeds of the rotating "battery-plus-change" motor.

I've been recently told that US coins, being non-magnetic, won't work for this Instructable. (Sorry about that!) Perhaps the US coins could be glued together to make it work. Furthermore, some Canadian pennies are magnetic and some are not.

You can order the BEST neodymium super-magnets from K&J Magnetics here.

See more of my homopolar motor videos at :
http://ca.youtube.com/MrfixitRick

81 comments

1-40 of 81

Aug 18, 2011. 7:17 AMvruiz3 says:

unexplained things #2 homopolar motor with 5 speed shft. :P

Jul 17, 2011. 10:40 AMtechnician ace says:

your idea is a wonderful and revolutionary idea ,sir

Mar 4, 2011. 5:01 PMSky_line91 says:

do you happen to know if this is possible with wires coming from a power source instead of a battery?

Mar 4, 2011. 9:43 PM

mrfixitrick (author) says:

A dc power source will work. It will require up to 5 amps at a couple of volts.

Mar 9, 2011. 5:43 AMSky_line91 says:

awesome, thanks

Dec 29, 2009. 10:21 PMdivyanshu007 says:

how does the movemement of the shifter result in the variation in the speed

Dec 30, 2009. 2:17 AM

mrfixitrick (author) says:

The shifter gets moved from coin to coin. Although the various coins have different resistances and magnetic values, the radius of contact of the shifter conductor to the spinning magnetic field is the biggest speed factor. (as long as the conducting coins don't have too much resistance).

Generally, the larger radius coins will spin slower but with more torque. This torque and speed could be calculated using the Lorentz force principles.

Feb 8, 2011. 10:51 AMRottom says:

would it be possible to just stack different thickness and diameters of the neo mags and apply the gear theory to thus?

Feb 8, 2011. 12:34 PM

mrfixitrick (author) says:

Yes, that should work, and produce more torque and rpm as well.

Mar 25, 2010. 9:49 AMShingoshi says:

I'm guessing that using any circular magnetic surface like one having a conical cross-section would actually give you a variable rate transmission. No more fixed speed shifts. Simply sliding the shifter from one radius to another would immediately change the speed of the device without ever having a discontinuation in rotation.

Xavian-Anderson Macpherson
ShingoshiDao

Mar 25, 2010. 10:22 AM

mrfixitrick (author) says:

Interesting concept...A fixed power but variable speed motor with a cone-shaped commutator.

Mar 25, 2010. 9:58 AMShingoshi says:

Come to think of it. A sewing thimble would work perfectly for testing the idea. Because the less variation in mass, the more accurately one can view the effect of changing the radius alone has. I would flip the cone of the thimble to cover the end of the magnet and extend over the battery. The result will be more stability avoiding the necessity to align coins for proper rotation.

ShingoshiDao

Mar 25, 2010. 11:10 AM

mrfixitrick (author) says:

Good idea, I will have to try it one day...or perhaps you should? hehe

Mar 25, 2010. 1:37 PMShingoshi says:

I just need to find myself some small NbFeB magnets. I'm thinking of a few devices around my house that I could strip apart to acquire the magnets from. So if I do get to do it, I'll definitely post my results here and elsewhere (ie. You Tube).

ShingoshiDao

Jan 3, 2011. 8:41 AMJ_gilbert6911 says:

I am doing this for a science project... somewhat. I am having trouble getting it to work. The thing i dont understand is the coin part. Do you need coins or magnets or both?

Jan 3, 2011. 1:08 PM

mrfixitrick (author) says:

The coins are magnetic Canadian coins. They are not necessary, except as a means of altering the speed. (different radius coins)

The magnet is necessary, and must be a powerful neodymium type magnet, found at a place like K& J Magnetics.

Jan 4, 2011. 8:08 AMJ_gilbert6911 says:

Would this type work? 13/16" dia. x 1/16" thick Grade N42 - Nickel Plated

Jan 5, 2011. 10:30 AM

mrfixitrick (author) says:

This experiment is tough to do. That 13/16" magnet won't work.

I just tried a 3/4" x 1/16" and it would not hold. 3 or 4 of them stacked will likely work.

A 1/2" x 1/4" N52 magnet will work. I prefer a stronger N52 magnet, and definitely thicker than 1/16", at least 3/8" thickness.

You could stack magnets like coins as well. For example, use a 1", then the 13/16" x 1/16", then a 5/8", 1/2", etc. stacked.

Jan 6, 2011. 8:24 AMJ_gilbert6911 says:

I bought a pack of 10 from K&J Magnetics. Would using several work?

Jan 6, 2011. 1:10 PM

mrfixitrick (author) says:

Try an experiment with loading up the battery with as many stacked 13/16" magnets as it can take and still stick well on the hanger.
Then remove one or two magnets for a little less weight. The coins are optional to vary the speed.

The hanger tip where the battery hangs is somewhat critical. It must be rounded and smooth, not a sharp point or edge. The magnetized battery hangs in better that way.

A thicker wire coat-hanger will work better than a thin wire one.

Jan 7, 2011. 8:35 AMJ_gilbert6911 says:

I went to the local home-depot and just gor regular copper-wire. Bought a few D batteries. Then from my science teacher i got a 2", believe its a black hole magnet (like refrigerator magnets but bigger and with a hole in the middle) I wrapped the magnet in tin foil and shaped the wire to fit around it. IT WORKS!!! IT WORKS!!! lol :) So far i have made the heart shape and somewhat of a spiral. Anyone with any ideas for other cool shapes??

Jan 7, 2011. 10:35 AM

mrfixitrick (author) says:

Good idea!
I didn't think that would work!

Have a look at this movie that shows wire-formed dragonflies and butterflies using the homopolar motor idea.

Jan 26, 2010. 7:49 PMcamaroboy says:

how much torque does 1st gear have?

Feb 3, 2010. 1:17 AM

mrfixitrick (author) says:

Good question. I don't know.

Feb 2, 2010. 8:25 PMcamaroboy says:

why does the battery spin faster when the wire touches the coin closest to the magnet/battery?

Feb 3, 2010. 1:16 AM

mrfixitrick (author) says:

The magnetic field is stronger when closer to the magnet.
And the radius is smaller, making it run faster.

Feb 2, 2010. 8:18 PMcamaroboy says:

how come mine doesnt work properly? it only works when touching the magnet. seriously, whats wrong with mine?????????

Feb 3, 2010. 1:15 AM

mrfixitrick (author) says:

The magnet may need to be stronger.

The coins work best if they are magnetic like Canadian coins or magnetic coins from a magic shop.

Jan 26, 2010. 10:03 AMcamaroboy says:

how many rpm can the 5 th speed do?

Feb 3, 2010. 1:13 AM

mrfixitrick (author) says:

5th is about 500 rpm.

Jan 26, 2010. 8:09 PMcamaroboy says:

omg this things awesome. im doing it for my science project, and im gonna burn it to the ground. lol just kidding. again great project and keep up the good work.

Nov 30, 2009. 4:58 PMToastaG says:

The shifter reminds me of a record player.

Jan 27, 2008. 11:05 AMfinlandrocks says:

ok no-one has asked a question about the use of the battery, does the batteries contents act as a magnet or fly-weight or both? would using a larger battery produce a faster motor or more torque etc? im really interested in this odd motor. thanks,simon.

Jan 27, 2008. 1:24 PM

mrfixitrick (author) says:

Good question! The battery acts as a magnet in that when it is attached to a magnet, it's steel core gets magnetized and enables it to hang off the wire-frame holder. It also acts as a flywheel somewhat. The current in the battery determines the torque and the voltage, the speed. I've been using the rechargeable AA Duracell NiMHbattery in the 2650 mah size. It's fun..try it for yourself

Jan 27, 2008. 11:05 PMfinlandrocks says:

hey thanks mrfixits for your reply, so im guessing that the batteries charge disspates with the use of the homopolar motor, you should try the experiment using D cell ansmann 8000mah batteries! :) cheers''

Jan 28, 2008. 12:13 AM

mrfixitrick (author) says:

Wow, 8 amps available current! Keep in mind with that amount of power, safety glasses are a must, as the neodymium magnets can explode. And wires can get hot, too. But hey, I want one! Ansmann has the best power AA batteries I've seen too, at 2700 mah. Thanks for the "hot tip" , findlandrocks!

Oct 22, 2009. 1:20 AMDr. dB says:

Cripes! ...don't forget your Kevlar undies, too!

Oct 12, 2009. 4:23 PMarea36 says:

Mumble mumble mumble