# Convert 4 pole DC to a two pole PM motor .



## Bird of Prey (Aug 24, 2016)

I have a two Prestilite 4001 motors , and I want to convert one of mine into a PM motor . I want to get the two magnets made to turn it in to a two pole motor . I have a custom Curtis controller that puts out 144 volts an 900 amps that I still want to use . I know that I might need something to keep the voltage from going back thru the controller . And the forward reverse switch is done by 4 contactors thru the shifter that has a neutal position that dose not send power to the motor at all .(my second safety switch) . I thought about putting diodes in line to keep the voltage going back in to the controller . Any thoughts to help me do this ? Or am I all ready on track ? Do I need a regen controller for this motor ?


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## major (Apr 4, 2008)

Bird of Prey said:


> I have a two Prestilite 4001 motors , and I want to convert one of mine into a PM motor . I want to get the two magnets made to turn it in to a two pole motor . I have a custom Curtis controller that puts out 144 volts an 900 amps that I still want to use . I know that I might need something to keep the voltage from going back thru the controller . And the forward reverse switch is done by 4 contactors thru the shifter that has a neutal position that dose not send power to the motor at all .(my second safety switch) . I thought about putting diodes in line to keep the voltage going back in to the controller . Any thoughts to help me do this ? Or am I all ready on track ? Do I need a regen controller for this motor ?


Hi Bird,

What are the first three characters in the Prestolite part number; M??-4001? After I get that, I'll tell you more. 

major


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## Bird of Prey (Aug 24, 2016)

MTY-4001- c , sorry about that .


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## major (Apr 4, 2008)

Bird of Prey said:


> MTY-4001- c , sorry about that .


Hi Bird,

With a little more google-fu I learned the MTY type motor is a 33 slot/33 bar single turn armature. It has a 7.2 inch outer frame diameter and 6 or 7 inch core length. It is a very strong series wound motor. Regarding you ideas expressed in post one:

1.) Years ago it was unthinkable to replace the wound fields with PM using an armature design such as this due to the low flux density available in ceramic magnets. Today the rare earth neo magnets are in the flux ball park. But you will find it impossible or incredibly expensive to obtain suitable size and shape of what you'll need. Then you'll have similar difficulty with the tools needed to convert the motor.

2.) It is unlikely any of the components of the 4-pole MTY motor would be at all useful in 2-pole motor. I have no idea why you would think such a change would be of any benefit.

So I'd suggest just building you PM motor from scratch.

Regards, 

major


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## dcb (Dec 5, 2009)

Hey Bop or major? I see those on ebay for a few hundred but have never found any more info, do you have any more specs?

i.e. series/shunt? Only seen two terminal images of it, so not sepex, EDIT oops, cant read the field terminal labels though, big enough for series though.

shaft size?

amps/torque/rpm/hp ratings?

Thanks.


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## major (Apr 4, 2008)

dcb said:


> Hey Bop or major? I see those on ebay for a few hundred but have never found any more info, do you have any more specs?
> 
> i.e. series/shunt? Only seen two terminal images of it, so not sepex, EDIT oops, cant read the field terminal labels though, big enough for series though.
> 
> ...


Hi dcb,

Google : Prestolite MTY-4001. I got several pages of FS sites showing photos in which I was able to recognize features. Sure looked like the end turns on a series field coil in one pic. Three bolts per pole shoe were used for 6 & 7 inch stacks. Pics of the comm and other info gets me to like 99% certainty it's 33 S & B. Photos show keywayed output shaft maybe about 1" dia.

It appears to be proprietary design to Raymond Corp. so unlikely to be performance information available. At that time Raymond made 36V forklifts. So as a drive motor it undoubtedly is set to neutral and probably had about a 200A one hour rating ventilated with internal fan, Class H.

The MTY design is close to the MTC-4001 design. MTC was sold under the Prestolite tag to different companies so performance curves can be found up 96V with advance. EVfun uses an MTC for his buggy at 96V IIRC.

Those 33 slot 7.2" dia Prestolites from the 70's and 80's were excellent workhorses. Much like you'd have with a WarP7.

major


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## Bird of Prey (Aug 24, 2016)

Why could you not use the brushes an case ? And or advance it ? I want to turn high RPM . 8,000 to( just a wet dream)11,500 RPM . The magnets will be smdc , they can take 500 degrees and lose no magnetic power .


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## major (Apr 4, 2008)

Bird of Prey said:


> Why could you not use the brushes an case ? And or advance it ? I want to turn high RPM . 8,000 to( just a wet dream)11,500 RPM . The magnets will be smdc , they can take 500 degrees and lose no magnetic power .


Hi Bird,

Two pole motors typically use 2 brush arms, one positive and one negative at 180 degrees apart. For same loading as the 4-pole, brushes would need increased cross sectional area.

And if you were to keep the same or similar total flux in the 2-pole as the 4-pole, then the yoke or back iron (case as you called it) would need to be twice the thickness.

The speeds you mention are achievable with that 4-pole machine, although you need to improve banding and balance. Jim Husted has banded commutators like that with Kevlar.

Regards,

major


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## Bird of Prey (Aug 24, 2016)

I can not find any one to do my motor . One guy left the country , one guy that said that he could do it , retired and two guys here just vanished . I would be happy to send my motor to any one who can get me near or at my goal . I already got someone to make a custom controller for me that rocked .....til the motor with a F rating threw some smoke . I also have another one just like it , it could help turn it into a twin motor .


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## Bird of Prey (Aug 24, 2016)

Does anyone know someone to rebuild and modify a dc motor for a high performance electric car ? Does anyone have Jim Husted's number , or anyone else ?


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## dcb (Dec 5, 2009)

Bird of Prey said:


> I would be happy to send my motor to any one who can get me near or at my goal


I'm not even sure what your goal actually is, but PM and 2 pole aren't gonna help you with performance.

Why don't you talk to netgain, their faq mentions kevlar banding as an option, and they have an interpole motor if you need high rpm(and thus high voltage).


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## Bird of Prey (Aug 24, 2016)

What and who should I do to get the motors to 8,000 to 11,500 rpm without giving up that much of my torque , motors and my controller ? Netgain will not help me because it's not there motor . The motor is direct drive .


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## dcb (Dec 5, 2009)

why does it matter if it is the old 4001 vs buying a new "race prepped" warp11hv (or whatever)? It'll probably cost a bundle either way, and netgain has plenty of experience in dual motor setups as well. 

what do you have to gain by clinging to the prestolite?!? (like I said, they are ~$300 on ebay...)


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## dcb (Dec 5, 2009)

I mean you gotta do a *little* of your own research...

https://bitcointalk.org/index.php?topic=154978.0

ampeater had basically the same motor, modified by Husted, 20 bitcoin at the time was like $20,000... performance isn't cheap, especially if you don't do any of your own fabricating or much research.


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