Will i be able to save this motor?

[SirCrashALot]

I've had this 4985 motor laying around for a while.
The front bearing was seized and the inner ring was stuck to the shaft.
I dremeled it off, but i hit the shaft and it now has a small cut. It looks superficial so i thought maybe it isn't much to worry about.
Also the windings on the magnets were slightly damaged by taking the rotor out.
I just took a small paint brush and applied a very thin coat of epoxy raisin, by spinning the rotor in my electric screwdriver and brushing a few drops all around.
Would do you guys think? Will it work?
It's drying now, will try tomorrow.

 

[Diem Turner]

If it still fits in the can and will rotate without touching anywhere, I don't see what harm could come of trying it out. I just wouldn't mash WOT right off the hop but, that's probably just uncommon sense.

 

[SirCrashALot]

If it still fits in the can and will rotate without touching anywhere, I don't see what harm could come of trying it out. I just wouldn't mash WOT right off the hop but, that's probably just uncommon sense.

That's what i thought. If it seizes, it seizes
I already thought it was a write off.
I have two more of those running on 4s i my Mojaves. I'll try this one on 3s first.
Btw. Tomorrow isn't going to happen.
I just noticed i am out bearings.

On bearings...
How about rubber sealed bearings in these motors? Since they won't see anything over 30000rpm on 4s. Think it'll do? I'd prefer that for the type of bash spots i have. Being dusty, salty and sandy.

 

[Diem Turner]

That's what i thought. If it seizes, it seizes
I already thought it was a write off.
I have two more of those running on 4s i my Mojaves. I'll try this one on 3s first.
Btw. Tomorrow isn't going to happen.
I just noticed i am out bearings.

On bearings...
How about rubber sealed bearings in these motors? Since they won't see anything over 30000rpm on 4s. Think it'll do? I'd prefer that for the type of bash spots i have. Being dusty, salty and sandy.

Nah, best to stick with ZZ bearings inside the motor, imho. I don't think it's an accident that those are all that you find in motors. I wouldn't but that doesn't mean you shouldn't. That's just me. YMMV.

 

[slick2500]

Nah, best to stick with ZZ bearings inside the motor, imho. I don't think it's an accident that those are all that you find in motors. I wouldn't but that doesn't mean you shouldn't. That's just me. YMMV.

FWIW some of the TRBRC hybrid ceramic motor bearings have a rubber seal on one side. The ones for the BLX185 motor bearings included. Been running them for years.

 

[morrjr71]

FWIW some of the TRBRC hybrid ceramic motor bearings have a rubber seal on one side. The ones for the BLX185 motor bearings included. Been running them for years.

The TRB RC ceramic hybrid bearings I got a few days ago for the outer wheel bearings on my Infraction 6s are like that.

 

[Diem Turner]

FWIW some of the TRBRC hybrid ceramic motor bearings have a rubber seal on one side. The ones for the BLX185 motor bearings included. Been running them for years.

Then I stand corrected @SirCrashALot. Forget what I said. I was only going on what I've seen up to this point and I guess I ain't seen errtang (I was under no illusions that I had, to be fair).

 

[Hector_Fisher]

Then I stand corrected @SirCrashALot. Forget what I said. I was only going on what I've seen up to this point and I guess I ain't seen errtang (I was under no illusions that I had, to be fair).

But I do think you point you make is one worth re-mentioning. Not just ANY bearing will perform well spinning at 30,000+ rpm inside the motor. Most all drive train servicing, rubber shielded bearings spin several times slower than the motor once you make the first gear reduction from the (generally) smaller pinion to the (normally) larger spur.

Unfortunately, finding good motor bearings can be a bit of a crap shoot. I'd normally say to buy something labelled as a "motor bearing", but I have no way of validating legitimacy. For example, a high quality rubber shield "normal" bearing may outperform a low quality "motor bearing". As a rule of thumb, I'd stick to the name brand, reputable "motor bearings" and you should be good.

Out of curiosity, OP what prompted you to tear apart the motor and thus find this condition inside?

 

[Greengaunja]

Ideally I'd say for a motor, especially high temp and rpm motors, PTFE seals over rubber would be preferrable. As for motors with steel shields, I wonder if it's more about keeping the bearing together than actual need to protect the bearing. The ceramic hybrids I've bought, Acer and Amazon "skate bearings", all had PTFE shields and races.

 

[Dan B.]

The ceramic hybrids I've bought, Acer and Amazon "skate bearings", all had PTFE shields and races.

It might be possible that those would be rated (ABEC or otherwise) for far lower RPM’s since they are skate bearings? Just curious.

 

[slick2500]

The TRB RC ceramic hybrid bearings I got a few days ago for the outer wheel bearings on my Infraction 6s are like that.

Weird that they aren't sealed on both sides.

 

[Dan B.]

Weird that they aren't sealed on both sides.

For motor bearings, they’d only need to be sealed on the outside face, right? Just spitballing here…

 

[SirCrashALot]

Out of curiosity, OP what prompted you to tear apart the motor and thus find this condition inside?

The front bearing was stuck on the shaft. I had to dremel it off.

 

[slick2500]

For motor bearings, they’d only need to be sealed on the outside face, right? Just spitballing here…

Yeah.

 

[Greengaunja]

It might be possible that those would be rated (ABEC or otherwise) for far lower RPM’s since they are skate bearings? Just curious.

Higher, according to what I've read. Here are the two taken from my TP 5670 and 2 leftover spares that are ABEC 11. First thing noticed is the spin time. Night and day difference.

According to what I've read, quality skateboard/rollerskate bearings have among the highest rpm rates and are perfect choices for motor bearings. These bearings were very similar spec-wise to Acer's RC specific hybrid bearings for motors with the main difference being these were $52 for 4 and Acer's $28 for 1.

The only thing different I would have done is is to go with ABEC 7's. The way the ABEC 11s installed, I know it's gonna be nightmare should they ever require changing. Very tight tolerances.

 

[Diem Turner]

The only thing different I would have done is is to go with ABEC 7's. The way the ABEC 11s installed, I know it's gonna be nightmare should they ever require changing. Very tight tolerances.

Yeah, I can imagine that the tolerances on those are an order of magnitude more precise than the grinding on the shaft of the motor.

 

[SirCrashALot]

Well, i did some research on bearings.
For the motor i wanted good quality bearings, so i looked at SKF. Their spec lists say that the rubber sealed bearings are only rated to 24000rpm. That rules them out for use in motors.
Their metal shielded bearings are rated for 80000rpm!. So that would be the 626ZZ.
They also come in two tolerance ratings.
Normal C0 and tight C3.
I went for the tigh tolerance C3

Now for the motor. It can be turned by hand, so i hooked it up to the MMX6S esc in my Slash and connected a 3s battery.
It works. But it got hot fast.
Could that have anything to do with the motor spinning without any load?
I am not really absolutely sure the rotor is not touching anywhere.
I might disassemble and sand the epoxy on the rotor a little.

 

[Hector_Fisher]

I wouldn't stress about it too much. Personally I'd just run it in a truck and test it out.

And yes motors can indeed get hot when spinning with no load.

 

[Greengaunja]

Well, i did some research on bearings.
For the motor i wanted good quality bearings, so i looked at SKF. Their spec lists say that the rubber sealed bearings are only rated to 24000rpm. That rules them out for use in motors.
Their metal shielded bearings are rated for 80000rpm!. So that would be the 626ZZ.
They also come in two tolerance ratings.
Normal C0 and tight C3.
I went for the tigh tolerance C3

Now for the motor. It can be turned by hand, so i hooked it up to the MMX6S esc in my Slash and connected a 3s battery.
It works. But it got hot fast.
Could that have anything to do with the motor spinning without any load?
I am not really absolutely sure the rotor is not touching anywhere.
I might disassemble and sand the epoxy on the rotor a little.

One issue with metal shielded bearings is that friction increases the warmer it gets due to expansion. For this reason, PTFE shields are a better option when considering temperatures. They will go as high as 480-500 degrees Fahrenheit before it breaks down. A thin metal shield becomes a problem at around 280 degrees Fahrenheit. There are actually bearings that are completely PTFE constructed but so far those made with with steel races, ceramic balls, and PTFE shields/retainers seem to be the best bang for your buck. The PTFE shield is also a happy medium for keeping water out between steel and rubber shields. But the biggest bonus is PTFE can run dry and still be as effective. The black bearing above in my pic has steel races, ceramic balls and PTFE shields and retainer.
For those not sure or don't know PTFE, or Polytetrafluoroethylene, is to Teflon what polycarbonate is to Lexan.

 

[GamwToInsomnia.gr]

I see you are referring to ceramic bearings. Are they so hard to find because of the price? Because I rarely see them for sale. Do you think they make a difference in wheels and differentials so they are worth buying or are they for more demanding parts of the car?