Larsb review of 72124 motor

Hello, i just got the 72124 motor from this group buy:

I will post some basic details and testing here to hopefully get a nicely on-topic thread. Keep out any offtopics please, i like threads that can be read and are useful to others.


Motor weighs 2.1kg
Rotor weight 595g
Stator weight 987g

Measured drill press kV: 109 (averaged over the three phases)
Measured inductance is 241 uH (ebay meter value, averaged over cogging steps)
Bearing 6001z Deep Groove, 12x28x8
Phase wires: 12AWG
Winding: 11 turns, delta connection
Stator stack: 75mm
Lamination thickness 0.5mm

Original winding 7x0.4, 11T delta
Phase wires: 12AWG

Both winding and phase wires are pretty small, i’d like at least 10AWG to support starting currents better. Most likely this motor won’t be able to take so much power. We’ll see. Rough rule of thumb from RC community seems to be about 3kW/kg max possible input so i’ll check if this can take 6kW.

Finish is spot on, perfect surfaces and anodisation.

Great Idea to create this thread.

I’ll try to add as much useful information as possible from my experience.

The bearings are NSK made in indonesia:

This time the manufacturer decided to fix the phase windings in a wired way. There’s a potential short from vibration if no additional insulation added!

As usually mineral oil or corrosionx or something like that is recommended.

Copper fill in the winding does not look so good in this picture. I guess it will have something like 20% fill so the motor could be rewound to accept about 40% more current with the same losses. Do you have some pics of the seals?

Copper fill is my “eternal struggle” with the manufacturer. For some mysterious reason (maybe their winding machine) they claim that the stator is full. I have done some manual rewinding and yes you can can put 20% more. Really do not what to do…

And no 20% more copper does not give 40% more current … sadly. It’s closer to 1:1 so +20% more current.

No I don’t have any seal photos.

40% fill is doable and normally not so hard to wind. double copper is half resistance so it’s sqrt(2) of the previous current capability. so roughly 40% more current.

Measured drill press kV is 109 averaged over the three phases
Measured inductance is 241 uH (warning:cheap ebay meter measurement)

I’ll add these in my first post to have all data gathered.

If you want a certain copper fill then i’d specify (dimension)x(parallells) and no of turns vs the manufacturer, check motors and claim if they did not do it.

What I meant was 20% more then the current winding. It is not half full it’s 80%(of the practical maximum that fits) full at the moment(this number comes from my rewinding experience). Looking forward for your further testing.

I can insure you it’s not 80% copper fill in this motor. I’d bet you a serious 1000usd and stand by it. But you will lose.

Anything above a true 50% is really good. Anything above 65% is really hard to accomplish even when you aim for it.

80% fill is basically impossible without special winding like square wire - this is not it.

Have to agree with larsb.

I know by experience 60% infill is really hard to wind. Most of the motor have around 30-40% copper infill

I do not know how to explain. I’m not talking about percentage of a slot crossection. I’m talking about the winding that is currently on the motor.

And the problem being the manufacturer does not want to increase the copper fill.

By the way it would be super nice to see somebody rewind this motor with 2x amount of copper. I made several attempts and only managed to increase the copper fill by 20% compared to what we have from the factory.

Inrunners are harder and long stators too. I am tempted to just try it but then no tests will be done for quite some time… I need to think about it.

I see, you are refering to the winding factor, which is something else. The previous conversation was about the coil fill factor, aka the copper infill.

Here is a screenshot of the parameters you enter / set for a motor :

Resistance, area and factors are calculated according to the parameters you set. I just wanted to show that we were speaking about 2 different things.

It all depends on the number of turns. Some Outrunners are harder to wind than inrunners.
@Konstantin_Cunichin Do you happen to know the number of turns ?

I am not referring to winding factor, i am referring to what is called ”coil fill factor” in your picture.

I know you are, so was I. But @Konstantin_Cunichin was refering to the winding factor :wink:

11 turns. Delta commutation.

Great. I opened motor, it was easy. I’ll size stator and see if it’s worthwile.

Looking at the winding it’s 7x0.4mm so 0.9mm2
There’s a broken wire in there :slightly_frowning_face:

This means current capacity is down to 90% of original. Maybe that’s my que to strip it and start winding. I have 2.5x1.25 square wire.
I’d be happy if i can wind 6 turns for roughly 200kV and 2x original copper.

1 Like

Thats properly sh1t! That should be a full refund from the factory as far as I am concerned!
I can fully appreciate why lift and FR have had their motors built elsewhere.

Totally agree, but the hassle and cost of shipping etc often saves the manufacturer… it’s pure shite.
@Konstantin_Cunichin: this should be claimed to let the company know their issues. The wire seems to have been squeezed and damaged in the assembly. Motor will probably work but at a lower performance.

I can’t be bothered to send it back, really…

That is probably the reason why I have seen different VESC detection results. The difference between vesc measured motor resistance was within 4 mΩ between different motors.

Regarding calling the motors shit and sending them back to manufacturer. That’s the easiest thing to do.

The hard one is to figure out how to get a good motor at a good price :wink:

I would really appreciate thoughts and ideas how to achieve that!

I’m thinking of local assembly … But on such small volume it will add to the cost 50 to 100 EUR per motor.

Or maybe I’m just doing a completely unnecessary thing that has no value for anyone.

Anyway the tests will show and people will hopefully give their feedback. Then I’ll decide.