motor rewinding?

def215

def215

10 kW
Joined
Oct 7, 2009
Messages
518
Location
philadelphia, pennsylvania
so i had a question. i opened up my motor casing to find that there was some damage to my motor windings(a brushed motor). it looks like some of the enamel came off, its not much, but its enough to bug me out. it seems the shaft has slight play from side to side on it. i am thinking about rewinding the whole thing now since i found this out(but i have been comtemplating this for some time now). i want to add more windings for some added torque. my question is does anyone have any experience with rewinding an electric motor? i do have experience with rewinding motors, but it was only rc car motors, nothing of the size of these motors yet.
 
from what i read, more windings give more torque and lowers the max rpm. also it has less amp draw, which is what im really looking for. i just really want to do this for experimental purposes. i have 22 ga magnet wire coming in soon, so ill wait for that until i really start playing with stuff.
 
More turns gives more torque per amp but the resistance also goes up - the amount of heat generated in the motor, for a given torque level, is the same. It would help relieve the load on your batteries and ESC, though.
 
it is possible to repair the winding, the super corona dope in this picture is made for that
stators.jpg


To experiment you may want to just repair your current motor and see if you can find a toasted unit to try things on .

be able to keep the bike running and cant help but wonder if an add in the wanted section may net you a bigger motor that will still work with your current controller.

:twisted: got comfy with the power didnt ya ? want more dont ya ? :twisted:
 
enoob said:
To experiment you may want to just repair your current motor and see if you can find a toasted unit to try things on .

be able to keep the bike running and cant help but wonder if an add in the wanted section may net you a bigger motor that will still work with your current controller.

:twisted: got comfy with the power didnt ya ? want more dont ya ? :twisted:
Click to expand...

well im just running the 250watt motor(similar to the unite motor) on my bike. so yeah, the ev grin is sorta still there, but i think i can use some more :D if i could, id like to find a currie 900w 24v motor. i think something of that size might make me happy, but im not so sure the size of the motor will fit in my frame discreetly anymore(ive ridden by several cops and they didnt even wink at the sight of it). i wanted to rewind this motor because if i do screw up, the motor is easily obtainable at tncscooters. or i can just buy a new motor from them :idea: but wheres the fun in that... :mrgreen:

Miles said:
More turns gives more torque per amp but the resistance also goes up - the amount of heat generated in the motor, for a given torque level, is the same. It would help relieve the load on your batteries and ESC, though.
Click to expand...

i didnt take the resistance into account at all, but my motor gets a tad bit warm only, i can still touch it after a 1/2 hour of riding. that is pretty much my main goal of rewinding my motor, relieve the stress on my batteries.
 
Toorbough ULL-Zeveigh said:
who in their right mind would want to read a 68 page thread about
Triple Rewind of Unite 500W Motor? :shock:
Click to expand...

why read when you can get hands on experience?

sorry enoob. i dont know why i didnt listen to you. i just got really antsy when my magnet wire came in today and i just couldnt resist.
here it is in its untouched state. looks a little dark and it smelled a little burnt.
IMG_0154.jpg

heres the motor stripped of the old windings. next to it is one of my rc motors that ive rewinded in the past.
IMG_0155.jpg

its coming together.
IMG_0156.jpg

finally, after 4 hours of knicking the layer of enamel on the armatures and testing for shorts.
IMG_0157.jpg

its ready to come back together.
IMG_0158.jpg


i just finished it and i cant ride it because its dark out and theres crappy weather, but i got on it to see if it would pull from a dead stop and it does, and much better than the stock windings(the stock windings was 30 turns, i rewound it with 37 turns). once this crappy weather breaks, ill get out there for some testing and see what my work can do...lol
 
nice work

hey dont listen to me . im drunk most of the time :wink:

good job . looks tighter and better packed than original.

same gauge wire ?

look forward to hearing how it works now compared to old
 
From a stop, and for all the time the controller is on it's current limit, the motor should have about 35% more torque.

It will come off the current limit at about a 35% lower RPM though (due to the higher BEMF), and peak power should be about 35% less.

You did a very nice job winding. :) Brushed motors are tough to do!
 
Toorbough ULL-Zeveigh said:
who in their right mind would want to read a 68 page thread about
Triple Rewind of Unite 500W Motor? :shock:
Click to expand...

Can link you up its written by your best mate Safe...most of the part.... :mrgreen: FrankG has video of rewinding the Unites on his website Thworkshop.ca that shows the best method to rewind the Unite IMHO.

KiM
 
enoob said:
nice work

hey dont listen to me . im drunk most of the time :wink:

good job . looks tighter and better packed than original.

same gauge wire ?

look forward to hearing how it works now compared to old
Click to expand...

yeah, i tried to pack the windings in as tight as i could because it was sort of a tight squeeze before i did the rewind. it was the same guage wire, which was 22 guage. ill definitely update information on how it performs.

Miles said:
Yes, great job def 8)
Click to expand...

thanks miles

liveforphysics said:
From a stop, and for all the time the controller is on it's current limit, the motor should have about 35% more torque.

It will come off the current limit at about a 35% lower RPM though (due to the higher BEMF), and peak power should be about 35% less.

You did a very nice job winding. :) Brushed motors are tough to do!
Click to expand...

thanks LFP. the torque is what i was looking for. hopefully this will let me be a little easier on the throttle. rewinding was not too difficult. it was messing up the windings that sort of took up a lot of time. also the last set of windings were a PITA because i had to really pack them in(they almost didnt fit).

AussieJester said:
FrankG has video of rewinding the Unites on his website Thworkshop.ca that shows the best method to rewind the Unite IMHO.

KiM
Click to expand...

aww darnit. i mustve not done my research well enough on this topic. if i did, i probably wouldve bumped into the link or something.

when the weather breaks next week, ill do some testing and see what my rewinding can do. im just hoping it will be better than before.
 
Yeah, if that's the same gauge wire, then forget about what I said above, you've increased copper fill by 35%, which makes for a huge improvement in everything! Great job!
 
liveforphysics said:
Yeah, if that's the same gauge wire, then forget about what I said above, you've increased copper fill by 35%, which makes for a huge improvement in everything! Great job!
Click to expand...

thats great news. :D

Miles said:
If you've managed to go from 30 turns to 37 turns, using the same gauge wire, that's great :D
Click to expand...

yeah. i originally tried to do a 40 turn, but i was definitely sure that wouldnt fit when i saw that theres supposed to be 2 different coils that goes into each armature slot(or is it called the stator? ive shouldve done my research on that :lol: )

so i took it out for a quick ride and theres definitely a noticeable difference. its nothing drastic like a massive power increase, but i could definitely notice it. before the rewind, it will normally cruise at around 12-15 mph without pedaling. when i rode it earlier, i could sustain 15-17mph constantly on a flat without pedaling and i can feel more torque from a dead stop(for testing reasons). no amp readings or anything of that nature yet. ill do that later. i wanted to test to see if it worked or not. so far im pleased with its performance. ill update with other info on this as i get to it, like my amp draw and wh/mi.

and thanks for all the great comments and advice you guys gave me. it definitely helped me out. :mrgreen:
 
Def,

My philly brother - I am speechless... Great work!

I got a project for ya bud... = )_

-Mike
 
thanks mike. i still need to break it in. the windings arent discolored or does it smell like burning yet. :wink:

i had a few questions:

am i supposed to balance my motor after i rewind it?

also,

luke mentioned that the overall characteristics of this motor will change because of more copper fill with the same guage wire, does that also mean that the amp draw of the motor will increase too or will it drop, or should i say, get more torque per amp as miles stated earlier?
 
def215 said:
luke mentioned that the overall characteristics of this motor will change because of more copper fill with the same guage wire, does that also mean that the amp draw of the motor will increase too or will it drop, or should i say, get more torque per amp as miles stated earlier?
Click to expand...

You will get more torque per amp because you are increasing the number of turns and the efficiency will
increase, too, because you are doing it without reducing the diameter of the wire :D

If you were at maximum practical copper fill, in order to increase the number of turns, you'd need to decrease the wire's cross-sectional area at the same time as you are increasing its length. Supposing you wanted to double the number of turns in order to double Kt and halve Kv? You would have to halve the cross-sectional area of the wire and you would be doubling the total length of the winding. So, the resistance would be squared, which balances out the losses being the square of the current and so the heat generated for a given torque would be the same as before.

In your case, you are increasing the number of turns, so the torque per amp will go up. You are only lengthening the wire, though, not reducing its cross-sectional area, so the resistance will only go up linearly, hence you will get a greater efficiency.

Does this make sense?
 
okay, i think i understand what youre saying miles. since i increased the windings, i get better torque. also since im using the same guage wire, resistance would be the same as before(from what i read, correct me if im wrong which is very likely :D ).

well, so far from what im experiencing, this motor is better than stock and that is always a good thing. :mrgreen:
 
You get more torque for the same amp draw and the maximum torque that you can put out continuously will be higher. :D

You have a more efficient motor. :D

Resistance will be higher, though, because you have increased the total length of the winding...
 
ok, now i understand. after a ride today, which was around 1 mile going flat out full-throttle, the motor did get warm. i could definitely feel some heat. i also tried retiming the motor also but my 30a breaker tripped while i was going flat out at 19mph(i know, not fast at all). i swear i broke it. i sat on the side of the street checking my throttle, motor and brake switch wire connections, until i remembered i had a breaker on it :oops:

i unadvanced the timing as soon as i got back home. tomorrow ill hook up my multimeter while i ride to get some numbers out of this thing.
 
Timing can make a HUGE difference on a motor. Getting that set correctly for your RPM range can be a huge difference in performance.
 
I feel like such a noob reading this stuff. But, apparently higher copper fill = good. So, would there be a benefit to using wire with triangular cross section? Seems to me you could easily fit more copper into the same volume, if it weren't a circular cross section...
 
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