About to rewind a hubmotor for a BMX wheel.

[Mouse]

I'm making a BMX styled small framed ebike and am lacing what I think is a 1000W motor originally for a 26" wheel into a smaller 20" wheel.
I bought a broken burned out motor with the intention of rewinding rather than buying a new motor and taking it apart.
I'm planning of rewinding the hub with fewer turns to compensate for the smaller wheel which will need to spin faster and return it to the same speed / voltage etc. I have little to go on for this as the motor was burned out when I got it so have no idea how fast it spun as standard but assume it came from a 26" wheel.
Ratio of 26" wheel to 20" wheel is 0.77
Ratio of 7 turns to 6 turns is .85
Using something I found that says Turns * kv = Constant. these numbers are kind of close .

The motor was originally wound with,
7 turns of 8 strands of 0.5mm wire.
New spec idea,
6 turns of 9 strands of 0.5mm wire.

I've already laced the rim using paired spoke pattern rather than radial which should be stronger and looks good and I'm going to be rewinding the motor later in the week and would welcome any idea about rewinding for this sort of conversion.


Shortest spokes I've ever seen.


Paired spokes for some torsional strength.

 

[calab]

There are lots of links showing you how to rewind a hub motor, it is quite tedious and time consuming but your in it for the hobby aspect.

What is your current plan to rewind the motor? Have you found the right wire and insulating paper?

 

[From-A-To-B]

Forum member Dui ni shou de Dui recently worked on a rebuild of a much larger QS motor. His rework was much more extensive, as he went on to rebuild the laminations. Maybe you’ll find his thread helpful for some of the finer points and pitfalls of rewinding.

Rewinding a QS 273 motor

Hello everyone, A good friend of mine unfortunately fried his motor recently. It looks like one of the phase partially melted down. He dropped the motor off to my place yesterday and now I'm trying to see if I can rewire it. That would be my first time attempting this task, so I thought I'd...

endless-sphere.com

 

[Mouse]

Thanks for the link. It was an interesting read.
I've used Nomex paper and 0.5 wire just as the original was wound with was but using 1 less turn per finger and 1 extra wire strand which is currently working out with regard to winding and available space in the slots. Time will tell if this was a clever idea.

I'm about half way through the rewire right now and will complete it when I get some spare time.

PS There's a random q in the link which killed it.

 

[nicobie]

Rewinding a motor is hard. The one time I attempted it I just gave up and tossed everything in the trash.

But don't let me discourage you from giving it a go. It will take a lot of patience to be successful.

 

[From-A-To-B]

Thanks for the link. It was an interesting read.
I've used Nomex paper and 0.5 wire just as the original was wound with was but using 1 less turn per finger and 1 extra wire strand which is currently working out with regard to winding and available space in the slots. Time will tell if this was a clever idea.

I'm about half way through the rewire right now and will complete it when I get some spare time.

PS There's a random q in the link which killed it.
View attachment 334885

Thanks for noticing that erroneous Q - I edited the link!

 

[Mouse]

This is always more tedious than I remember.
Home made spool to hold the 9 strands of 0.5mm wire

 

[calab]

Patience and small, strong hands is required.

Same goes for lacing rims. But rewinding a motor is more tedious. I havent done one yet, I got the hubs to do it on. Perhaps one could try it on a smaller scale before jumping into the big hubs, maybe you have an old rc motor to practice on, nimble up those small fingers.

more tedious than I remember.

Smart, like trying to put line on a fishing reel, you just gotta do what you gotta do in order to get it done.

Home made spool