Increase the speed of electric motor with rare earth magnets

[EcoForumZ]

Saw this video on how to increase the speed of an electric motor with powerful magnets on the outside of the motor. Interesting idea but not sure how practical it would be on larger motors. My guess is you would need a few powerful rare earth magnet the size of a tennis balls to see any real benefit. In the video they claim to increase the RPM by 200%. If you could increase the RPM by 15 - 30% with some magnets that could be a very good mod. Not sure how realistic this would be and it is probably not but thought I would throw it out there for those of you that just so happen to have a huge rare earth magnet to test this out with.

http://www.metacafe.com/watch/665396/how_increase_speed_of_electric_motor

 

[fechter]

That trick is called field weakening. By placing large magnets on the outside of the motor they are able to reduce the magnetic field in the armature resulting in a speed increase. This changes the voltage constant of the motor. A series wound motor will do this automatically as it speeds up. You can also do this by moving the magnets further away from the armature.

In practice, it would be difficult place magnets on the outside of a motor so they could move. If the magnet ring is adequately sized, most of the flux from the external magnets would be shunted by the ring, making the change in field strength minimal.

 

[Link]

In practice, it would be difficult place magnets on the outside of a motor so they could move. If the magnet ring is adequately sized, most of the flux from the external magnets would be shunted by the ring, making the change in field strength minimal.

Oh, I'm sure I have a magnet or two that could do it.

8)

 

[Miles]

Blimey, that's a monster You could have some interesting accidents with it...

 

[Drunkskunk]

The first thing I noticed was the mondo magnet, the second thing I noticed was the tape measure isn't sitting on the desk. Since it appears to be a cast aluminum (non magnetyic) case, that means its being held up by just the steel tape and the tiny screws. Ami rite? Damn powerfull magnet.

I wounder if that thing could pry a bottle cap of a bottle of bee.. err, coke.


As for putting magnets on the outside, the flux ring around the outside of the motor would kill the effect for the most part on motors that use a high number of magnets, But!

back when I was a kid, we had Stompers. Little electric 4x4 trucks about twice the size of a Matchbox car. They used 1 AA battery and a 2 magnet motor, and when I was 10, we used to race them. And it took no time at all to figure out how to run them off 9V batteries, and how to add broken refigerator magnets to the outside of the motors to give them a speed boost

Eventualy, We discovered that adding iron to the outside, instead of magnets worked even better.

 

[TylerDurden]

that means its being held up by just the steel tape and the tiny screws. Ami rite?

Don't forget all the tape inside the case...

Eventualy, We discovered that adding iron to the outside, instead of magnets worked even better.

THAT has interesting implications. 8)

 

[fechter]

Weakening the magnets to make a motor go faster gives it a wider rpm range so it might be like having gears. You could gear for a lot of torque in the low end and use the field weakening to still have a decent top speed. If you put magnets in a ring over the main magnet ring in such a way that you could rotate it, you could align the magnets to make them stronger then rotate the ring by one pole to make the magnets weaker. They'd have a strong tendency to align in the strong mode, so it would take a lot of force to rotate the ring. This could be offset by a spring perhaps.

Link, that's a scarey looking magnet. I'd be afraid to get it that close to my computer!

 

[Link]

Link, that's a scarey looking magnet. I'd be afraid to get it that close to my computer!

Did you know you can degauss a CRT with more magnets?

 

[Tiberius]

Hi Link,

I was going to ask if you had a TFT or a CRT. A magnet can make a CRT nicely psychedelic - bit if you get too close with a big one you can magnetise bits and the effect stays there. Believe me, I've done it in my youth. You then have to de-Gauss it before the boss finds out.

Nick

 

[Link]

That's the little TV in my room. The computer screen is a TFT.

I know all about the screen getting magnetized. I've gotten quite good at using smaller magnets to demagnetize it.

This thread reminds me of this vid that the Doc posted:

[youtube]6_41btVawMc[/youtube]

 

[Miles]

This thread reminds me of this vid that the Doc posted:

And you've reminded me that I came across a discussion on that over at RC Groups
http://www.rcgroups.com/forums/showthread.php?t=839839

 

[alex]

Interesting subject that prompts me to hunt for more...

http://www.youtube.com/watch?v=OEfpGoYMdvQ&feature=related

Hopefully, they will develop this technology for ebikes first...

By then, no more low speed issues, no more battery issues...

Batteries ? Who need batteries anymore ? :wink:

 

[Tiberius]

I know all about the screen getting magnetized. I've gotten quite good at using smaller magnets to demagnetize it.

You can demagnetise it with the big magnet. Flip it back and forth rapidly (hold your arm out straight and swivel your hand), bring it up close and then draw away slowly while still swivelling. That mimics what a de-Gaussing process does - rapid field reversals that start stronger than the magnetisation and then reduce down to low level.

Nick

 

[Link]

That doesn't really work for me. I just end up changing the pattern on the screen. I can't seem spin it fast enough, I guess.

I just use a smaller neo magnet and make it green where it was purple and vice-versa. Takes a little practice, but you can't even tell I did that to my screen anymore.

 

[Link]

This thread reminds me of this vid that the Doc posted:

And you've reminded me that I came across a discussion on that over at RC Groups
http://www.rcgroups.com/forums/showthread.php?t=839839

Hmm, interesting. Most there seem to think it's a dumb idea where most here think it would be a pretty cool/good idea. :?