Anybody know about BLDC motors?

[WNDSRFR]

So, the motor on my Phantom ESC failed lately and I'm trying to find a replacement. These are specs I measured.
Motor housing: Dia 55mm Lt 67mm
Shaft: Dia 8mm Lt 67mm

It uses 28VDC and is thought to be 4KW and 150A and spins around 50k rpm. A real beast of an RC motor. I think it was for a large electric ducted fan. I'm learning but don't know a lot about BLDC's. I think it's a 6 pole but not sure. It seems to have 6 magnets on the rotor and 6 coils on the stator. Can anyone help me with this? The only really important specs are 28 VDC, 50k rpm and an 8mm shaft

[soundman98]

try an r/c hobby forum?

[gen3v8]

These motors have a kv rating, kv meaning how many rpms the motor does per 1volt. They also have a S or voltage rating and max amps. They go way deeper best to google.
The batteries are usually lipo and are rated 3.7v a cell,flat voltage. So 1S is 1cell 3.7volts(4.2v charged), 2S is 7.4v(8,4v), 3S is 11.1v(12.6v) and so on. They also have mah capacity and a C rating for discharge current.
https://www.google.com/aclk?sa=l&ai=...WgQ0Qx6BAgDEAE

[NoHaveMSG]

It's also sensorless from what I can tell from the picture, meaning the ESC doesn't get feedback from the motor to tell it's stator position.

[WNDSRFR]

Yeah
It only has three wires attached to it. And after closer inspection, it looks like it has 4 magnets and 6 coils.
I ordered some new bearings. I'm going to see if i can bring it back to life. The bearings are only 15 bucks so it's well worth a try.

[NoHaveMSG]

Might be worth testing across all the phases(not sure if that is the right term here but i'll go with it) with a multimeter. You could have a short in a winding or something. What is it doing exactly?

[WNDSRFR]

What happened is it seized. I took it apart by pushing the rotor out. It has a lot of magnetic force holding it in. Then I put it back in and it is no longer seized. I think what happened is: the bearing or bearings failed. I think one or more balls got stuck to the magnets and gummed it up. The balls were tiny. There were still a couple left but the bearings are gone. Except for the bearings everything else looks OK.
I have no speed control so it's going to be scary testing this thing. It's either 50,000 rpm or off. Should be fun.

[NoHaveMSG]

Originally Posted by WNDSRFR

What happened is it seized. I took it apart by pushing the rotor out. It has a lot of magnetic force holding it in. Then I put it back in and it is no longer seized. I think what happened is: the bearing or bearings failed. I think one or more balls got stuck to the magnets and gummed it up. The balls were tiny. There were still a couple left but the bearings are gone. Except for the bearings everything else looks OK.
I have no speed control so it's going to be scary testing this thing. It's either 50,000 rpm or off. Should be fun.

Ahh, that makes more sense. As long as you can make out the bearing numbers it should be easy to get direct replacements. Even just being able to measure them will get you close. I usually recommend tractor repair shops for sourcing bearings locally if you have any available in your area. Living in the grass seed capital of the world, I have an abundance of them.

[gen3v8]

Originally Posted by WNDSRFR

I have no speed control so it's going to be scary testing this thing. It's either 50,000 rpm or off. Should be fun.

I can`t see how it will run up this way. Please explain.

[soundman98]

Originally Posted by gen3v8

I can`t see how it will run up this way. Please explain.

not enough load to slowly wind up.

it goes like this

[WNDSRFR]

Originally Posted by NoHaveMSG

Ahh, that makes more sense. As long as you can make out the bearing numbers it should be easy to get direct replacements. Even just being able to measure them will get you close. I usually recommend tractor repair shops for sourcing bearings locally if you have any available in your area. Living in the grass seed capital of the world, I have an abundance of them.

There are no identifying features of any kind on anything. I was hoping to peel off the Phantom label and see Hobby King under it, but no. I ordered the bearings from Grainger. I was going to get them from McMaster-Carr but the shipping cost more than the parts.

[WNDSRFR]

Originally Posted by gen3v8

I can`t see how it will run up this way. Please explain.

It has a motor controller/battery charger. But the controller has two states: off or on. It is switched by a normally open switch activated by the gas petal. It is set to be full on at about 80 percent throttle.

[gen3v8]

F86D Sabre Dog 5kw 50v EDF only a bit over 100amps + - losses. Mine 10+ years ago?. It still runs 150mph.

[WNDSRFR]

That might just work! The compressor wheel on mine is 98 mm and weighs 98 grams. Can you give me a manufacturer and model number? I just need the motor not the edf.