UPDATE ------I rewound my first motor, it runs great.

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paul scooter
Last seen: 4 years 12 months ago
Joined: Thursday, January 11, 2007 - 07:02
Points: 18
UPDATE ------I rewound my first motor, it runs great.

Update on my rewound UE motor.
It was running great, lots of power and about twice the speed. So i wanted to push it all out up a steep long hill. When i got to the top of the hill it seemed to loose about half of its power, i took it easy and rode it home to take it apart to see what happened. To my amazment 2 of the 4 brushes melted the solder and the wires came off. Wow thats about 460 degrees, much hotter then i would ever had thought. I'll try to buy some high temp solder and put a blower on the motor to cool it and see if that helps.
I would like to get a bosch gpa 750 motor with a built in fan and rewind it. If someone has a rewindable motor and wants to sell it please write me at paul_scooter [at] yahoo.com

I was riding my Charly a few weeks ago and ran over a nail. I didn't notice until it was too late and the increase in rolling resistance burnt out the motor. I just put on no flat tires so that will never happen again.
I wanted to rewind the Bosch motor but never did anything like that so i decided to experiment on an old Urban Express motor i had. I wanted to have a before and after comparison for the UE motor rewinding.
I replaced the Charly Bosch motor with the UE motor, to my surprise it fit on like it was made for it. My top speed was only12 MPH, with fair torque, so it was a little slower on top end and climbing hills then the original Bosch motor.
I removed the UE motor and unwound it paying attention to the winding pattern and the number of turns.
I think the wire size in the UE motor was 20 gauge using 12 turns per winding. It looked like it had room for many more turn or a much larger gauge wire . I rewound it with 16 gauge using 6 turns because that was all that i was able to fit in the coils. Knowing that the RPM would approx double i used high strength epoxy to fill the small coil gabs and hold them in at high RPM.
When i tried out the motor i was very surprised at the speed and power of the motor. The flat road max speed was now 24 MPH and the hill climbing ability was noticeably better.
I have one more UE motor that someone gave me and i think i will rewind that now that i have a tiny bit of experience at it. I can do a much better job and practice once more before i rewind my Bosch motor. It was a lot of fun and a great learning experience. I was very surprised at the great outcome.

Deafscooter's picture
Last seen: 15 years 9 months ago
Joined: Friday, November 17, 2006 - 17:39
Points: 519
Paul, That good Job you did rewound the UE motor => see inside

Hi Paul D, you did good job rewound the UE motor also Deafscooter explain to Paul D
== How to rewound and balance the armature make it better fast with #16 wire

Deafscooter done many time wound on motor make it go 50 mph on Rad2Go motor

Craig warning you the brush can burn / wear out when too much currents on loads
you need get heavy duty brush and spring also thick copper wire inside the springs !!!



chas_stevenson's picture
Last seen: 12 years 3 weeks ago
Joined: Wednesday, December 6, 2006 - 17:14
Points: 1309
RE; I rewound my first motor, it runs great.


Sounds great, good job, rewinding motors can be a hard thing to do but it sounds like you did everything right by watching how everything was when you took it apart. Don't forget to balance the armeture afterwards.

When I raced remote controlled cars we would rewind motors to get more RPM and to get more torque. This was accomplished by using dual winds on the armeture. We would wind 16 turns for torque and then layer another set of winding of 8 turns for RPM. This worked great for the RC cars. I never tried it on a larger motor. The wire size was also important. We used a small wire for the 16 turns and a larger wire for the 8 turns. My sprint car had so much torque it could pull wheel stands as you came out of a corner and stood on the throttle. RPM was not a problem as this car could reach 55 mph in a city block.

Just another idea,
Chas S.

paul scooter
Last seen: 4 years 12 months ago
Joined: Thursday, January 11, 2007 - 07:02
Points: 18

thanks Chas,
I was fun and i learned a lot. I searched all over on line and wasn't able to find much on " how to rewind a PM motor ". I did try to balance the armature but wasn't very successful. I spun it and it seemed to stop fairly randomly. I ran the motor up to 8000 rpm and was just barely able to notice any vibration, so i don't think it highly out of balance. I would like to know a better way to balance it then just supporting it on the bearings and spinning it by hand. I marked the top with a pencil to see if there was a trend but was able to find one.
Can you tell me more about the dual winding technique? Are the windings in parallel? Was there a way to switch for torque mode to high RPM mode? I chose the wire size by going one size larger then what was on my original Charly Bosch motor. The UE motor looked about 20 Gage, the Bosch motor looked about 18 gage and the wire i chose was high temperature 16 gage. I'm glad i didn't go any larger, i think 16 gage was the largest i would be able to bend and manipulate in the small spaces.


PJD's picture
Last seen: 1 day 10 hours ago
Joined: Wednesday, November 22, 2006 - 05:44
Points: 1416
Different Paul


The person who did this rewnding is a different Paul.

I did the amperage modification to my e-max controllers. Being as the 2000W e-max motor is brushless, the increased amps should not hurt the motor if ridden within reasonable limits - it's the controller that is the concern.

I'd like to try an rewind on an e-max motor for more speed, but I'll need a spare motor before I'll try it...

Paul D.

Last seen: 14 years 3 months ago
Joined: Tuesday, November 21, 2006 - 13:01
Points: 137

Paul, the more I study this the more convinced I am that rewinding is the way to go. Some googling will find sites with people doing amateur rewinding for fun. Here's one: http://groups.yahoo.com/group/lrk-torquemax/
(Edit) and here's another one, showing pictures of a smaller motor but probably very similar to the e-max hub http://aquaticus.info/BLDC

It was a long time since I studied this but I have a vague picture of that in cheap motors the windings are not well optimised. To save cost, most are wound using machines, and can be rewound by hand a lot better. Some don't even fill the available space with wire. Not sure what category the e-max hub falls in, but one can guess. Chances are that the OEM wire is not the best money can buy either. So you might be able to get the same number of turns (=voltage) with thicker and lower resistivity wire, or fewer turns (lower voltage, more amps, lower torque, more speed) with even thicker wire.

The winding is static and only the magnets are spinning, which means we don't need to be overly concerned about centrifugal forces and balancing. If you're really ambitious, you can replace the magnets as well.

I will be looking for a spare e-max hub motor too. Together with your controller mod it will be a killer.


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