Rewinding Motors

[Motorman]

Has anyone here tried rewinding a burned up motor? Is any enameled wire good or is there a special wire for this? Just wondering if you thought it was worth the trouble, did you have success or better to just buy a new one.

Thanks,
MM

 

[David Hoover]

I have no personal experience in motor rewinding but you may learn something useful here  http://www.gobrushless.com/shop/

Hope it helps.

Best, David

[Motorman]

Cool site, thanks.

[John Cralley]

Likewise, I have not rewound a motor but I know of one modeler who has. I believe at one time you could buy motor kits and wind them yourself. This fellow would rewind motors to change the KV value.

[Tim Wescott]

My inclination is to tell you to take it apart, carefully, then put it back together with new wire.  There's a good chance that the windings are multiple strands in parallel (Google "Litz wire" for reasons).

But you could probably get the job done more quickly by getting a second job flipping burgers, then using your pay to buy a new motor.

[CircuitFlyer]

So you want to put the smoke back inside, eh.

I've done a couple of small motors, Park 250 & Park 450 size.  It can be a little fussy.  Work carefully and neatly and it may perform a little better than what the manufacturer can mass produce.  I wouldn't recommend using multistrand for the first time.  Just substitute a larger gauge that has the same total cross section area should be good.  If you loose track of how many turns on each pole or mess up the order you may have to rip it out and do it again.  You will change the Kv.  If you have the patients and want to learn something new its a fun evening project.

What motor is it?

Paul

[Motorman]

It's an E Flite Power 15. I'll take it apart and see what it looks like.

MM

Update: Looks like the bell housing is threaded on using glue or you can press it apart in a big vise like dummy just did. Surprisingly the threads still look good.

The wires are multi strand, 8 strands of .011" wire 29 gauge? It's a 12/14 motor so looks like it might be a dLRK Evolution wind because it has Delta terminations.

There are strips of plastic glued in the gaps of the rotor I guess to keep dirt out? Might have to destroy them to get them out unless acetone will loosen them.

Thanks for all the advise.

[John Rist]

I tried rewinding a Cobra motor.  The problem was the endbell on one end would not come off.  With the endbell in the way it was  impossible to get the windings tight enough or straight enough to get all of the wire back in.  I was able to rewind it with small wire and get it to run however it, of course, would not handle the power required to fly the plane.   Also it took some doing to figure out the wind patter.  The Cobra was different than the online examples I found.  The price of a new Cobra motor is so low that it isn't worth the trouble to wind your own unless it's fun thing - just to prove it can be done.

[Motorman]

I tried rewinding a Cobra motor.  The problem was the endbell on one end would not come off.

I can get that off for you, I have a 10 ton press see post #6.

MM

[FLOYD CARTER]

I have rewound other types of motors, but not the model type.  You would be wasting time using ordinary enameled magnet wire.  The sharp bends and run heat will cause the "varnish" to fail.  You have to look for "Heavy Polythermalese" insulation.  This is industrial grade, not normally available in small quantities.

The power density in these small motors causes high heat build-up, and they inherently have poor air circulation to the fixed stator.

Floyd

[Motorman]

Would this work?

http://www.gobrushless.com/shop/index.php?app=ccp0&ns=prodshow&ref=MW-29G-QP

[FLOYD CARTER]

29 ga. is too small for anything over 100 Watt size.

F.C.

[Tim Wescott]

29 ga. is too small for anything over 100 Watt size.

It's pretty common in high-performance, low-voltage motors to run multiple strands of wire in a bundle.  If you do that, 29 gauge would work.

I do NOT know the details: people who sell Litz wire say you have to braid it in specific patterns for it to work.  Yet I've seen bundles of fine wire work well in a switching power supply when they were just twisted into a rope and wrapped around a toroid.  So I can't explain it, but I've seen it pull someone's cookies out of the fire.

[FLOYD CARTER]

Litz wire is multiple strands, each one insulated from the others.  Since HF current flows on the outside of the wire ("Skin Effect") you get less loss at HF because of the increased surface area. 

This doesn't hold for low frequencies, or DC, where electric motors live.

[Tim Wescott]

The fundamental frequency on a coil in a typical 12-pole motor is going to be around 800Hz, which is enough for skin effect to start showing.

I know that the theory says don't bother, but I also know that several sources claim that it adds performance.  I have not personally tried it, so I can't say.

Multi-strand wire would certainly be easier to wind in a motor, though.

[FLOYD CARTER]

Genuine Litz wire has each tiny strand cotton-covered.  That takes up a lot of space, while enamel coating is much smaller diameter.

It's also a pain to get each strand properly tinned for a solder connection.