Thrust bearing setup help

[ray schrauwen]

Just wondering how much space to leave for the 3 piece thrust bearing on a TP Power 4070 motor W/8mm shaft? End play is about 2mm so 1/2 that less or more??

Should it be lubricated and if so where?

Thx.

[Fella1340]

The proper location would be halfway between the total endplay. This should leave the ball bearings running true without loading it either way. As far as lubrication you want the balls and races coated in grease. That said I'm not entirely convinced that the thrust bearings will stand up that
well if running a real high rpm setup. I have bought a few myself that are still sitting in my parts box and will likely stay there. I'm sure many people are running them with great success though. 2mm seems like an extreme amount of endplay to have in a motor. I just went and checked a few motors of mine. I looked at two different size brand new TP motors and I would need a dial indicator to measure endplay as it's not discernible by eye or feel. That will change a bit once broken in. The tfl motor had well under 0.5mm endplay (can't give a more accurate number without using the dial indicator) and it has some run time on it. At 2mm it makes me think that that either the shafts are moving in the inside diameter of the bearing or more likely the outside diameter of the bearings are sliding in the motor end caps. I have no idea if this is common in rc boat motors or not. I work as a millwright and have installed and rebuilt hundreds of motors in just about every application you can think of and I would find this as an area of concern. This is well over a 1/16". Perhaps somebody else can chime in and explain things if this is a common occurrence. Sorry I couldn't offer a proper solution

[rearwheelin]

I go .5 mm

[785boats]

I let the armature sit where the magnets want to put it in regards to endplay & then have a few thou between the coupler & the thrust bearing.
If you leave a larger gap between the coupler & the thrust washer than the amount of endplay, then the shims on the armature will be pushed back to the end bell bearing under load, & the thrust bearing won't even be in the game.

You will also find that one of the thrust washers is a more loose fit on the shaft than the other one. The loose one goes against the motor, & the tighter one goes against the coupling.

Just like Fella1340, I coat the race with flex shaft grease during assembly, but then after a couple of runs I just add a drop of light machine oil before each run.

Paul.

[ray schrauwen]

Awesome, thank you and I see what you mean Paul, one side of the ball race sits close to the outer washer on one side compared to the other. So the side that has smaller gap goes to the coupler.

Yes seems like a lot of end play and I'll check the bearings to see whats going on in there first.

Thanks a bunch. It's the custom TP Power 1250kv 4070 motor that has 8mm shaft, I run it only on 6S2P Revo's and a 447 prop and it got pretty dang hot on a few runs so, when doing maintenance, I noticed all this end play and thought, maybe I need a thrust washer to cut down some heat from the rear bearing. It's not a lot of rpms and it's in a Whip 40.

[Fluid]

The motor bearings are designed to take thrust loads. The motor end play is most likely due to the internal motor shims being a bit too short. Thrust bearings are usually not needed, but if used they must be installed so that they take the thrust not the motor bearings, which requires care in installation....as described above. Do NOT use "grease", high speed bearings need good oil!

[ray schrauwen]

Thanks Fluid, we'll see how it goes. I'm sure it did not have that much end play when it was new because my other 4070 doesn't it's still new.

[Fella1340]

I understand why you want to use oil on the thrust bearing due the the rpm. The fact that there's no way to keep oil on the thrust bearing while running is an area of concern to me. The microfilm left on the bearings won't last long. Hybrids like ceramic balls are better suited to the application where adequate lubrication isn't available. I am basing my thoughts on industry practises, not from years of running thrust bearings on brushless motors. They seem to be more of a drawback than benefit imo.

[ray schrauwen]

We'll see what happens next time out. I'll try both oil & grease during the day.

[Fella1340]

I am looking forward to see how it works for you. I haven't found much information about thrust bearing use period, some first hand feedback will be great! I am interested to know the temperature of the thrust bearing versus the rear motor bearing. I hope everything works out great!