Motor - Balance Data

If you could do it, let us know and what tools need to be changed. And the exact links to these Bearings. We will be very grateful!
I went with Metal bearings, I updated my post above to include a link to what metal bearings I purchased. Also linked to the Metal/Ceramic versions, if interested.

Motor - Balance Data | Page 2 | 3D Robotics Drone Forum

FWIW, Avid metal bearings are $1 a piece. Being new to the bearing game I thought what the heck. I bought 10 bearings each, thinking I would have a cull or two, they all seem fine and better than I replaced. Time will tell though. You can buy the Boca for $6 each, but why...

I machined bearing presses; bought bolt, washers and thumb nut. Pressing, seating and aligning the bearings correctly is fairly important for the life of the bearings. Press the bearing only on the outer race, otherwise you'll have a short lived replacement. My effort produced an improved motor balance.

There are bearing tools available on the interweb, just didn't care to spend $30 and didn't want to trial and error someone else's design.
 
Installing motor bearings.
If you heat the center (stator) of the motor with a heat gun, (should be quite warm to hold), it will expand slightly.
And if you cool the bearings, (I put them in the freezer in a plastic bag for a while), they will shink slightly.
Then when it comes to installing them they should fall into place, the hotter & colder, the better.
And as Rich mentioned, if you press them, press only on the outer race, and dont hit them in.
 
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In my days at a helicopter engine shop, seating the Lycoming gearbox bearings was interesting. The box would be put into an oven at 300 deg while the bearings were packed in dry ice. We still had to use a rubber mallet to pound them in...
 
Nice thread we got going here. I haven't flown solo in a few months. With all the recent updates I expect I'll have lots of reading to do. Did I miss a link to how one would go about balancing their motors? Regarding that pull you feel when turning the motors by hand I can feel all of the little "grabs" and if I recall correctly they are pretty pronounced on my solo. As if they were a few mm or so apart. Should we not be feeling that?

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Regarding that pull you feel when turning the motors by hand I can feel all of the little "grabs" and if I recall correctly they are pretty pronounced on my solo. As if they were a few mm or so apart. Should we not be feeling that?
You always should feel the "pull" of the magnets, if not then it no workie.... The degree of the pull is the question. it appears that several of the CW/Black motors have a greater pull than the comparable CCW. At speed the effect diminishes....so I think it is a rabbit hole to consider it the offender. At least at this time.

FWIW, the correct term for the magnetic pull is Cogging Tourque or Detent. There is an IEEE paper on the subject. The paper basically says it is either the stator, magnets or the bell roundness. There's more than that, but for our purposes that's enough to isolate a cause.

I had written the above reply last night and then realized I had never measured the run out for the bell housing. So I set up my dial gauge, mounted the #4 motor pod off my table saw fence and proceeded to measure the run out. To my surprise the bell was running a little over .001" out towards the exposed bottom portion of the bell. The location of the difference was opposite of one of the grub screws, the one set to the flat of the shaft. The top side of the bell had very little run out if any.

So there is a possibility that the shaft alignment is the source of the excessive Cogging Torque. Allowing a set of magnets to be closer to the stator. I've never been concerned about run out before in machining, since it is a tolerance related to the machine itself. True the machine and run out should not be an issue.

I measured another CCW motor pod, which had very little Cogging Torque, and it's run out was tight. Interesting and it confirms a possible reason for the perceived issue. My question remains, does Cogging Torque contribute to vibration while the motor is running? Obviously the run out does, but could be compensated by balancing with weight...just like they do during assemble of the motor. Take a motor apart and you see the epoxy plugs in between the magnets as balancing weight....

And yes, I removed both motor pods several times and remeasured to confirm my process was not flawed. About 6 times with the #4 CW and 3 times with the CCW. If anyone has the proper gauges, I'd appreciate any confirmation that agrees or disagrees with my findings.

This could be as simple as how the bell cap was drilled to accept the shaft. You'd presume they ran the CW on one machine and then the CCW on another....
 
Interesting excerpt from a bearing manufacture's documentation for preloading bearings... 10.2 is the main point I'm making with this excerpt.

10.1 Preload


A pair of axially loadable bearing is to be loaded in advance in the axial direction F. This is called “Pre-loading”. Bearing has an internal clearance. Pre-loading reduces this clearance and elastic contact of ball and raceway occurs. By the result, the bearing does not have a looseness due to the clearance, which leads to the reduction of vibration and noise when rotating. Moreover, this contributes to the higher rigidity of the bearing. However, excessive pre-loading causes the increase of friction moment, heat generation and seizure of the bearing. In order to avoid this, optimum selection of pre-loading level and method is highly recommended.

10.2 Effect of Pre-loading

1.Maintains the bearings in exact position both radially and axially and also maintains the running accuracy of the shaft
2.Increases the bearing rigidity
3.Minimizes noise due to axial vibration and resonance.
4.Prevents sliding between the rolling elements and raceway due to gyroscopic moment for high speed application
5.Maintains the rolling elements in their proper position with the bearing rings.

http://www.nskmicro.co.jp/products/bearing_technology_pdf/ISC_P24-25.pdf
 
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So here's another tid'bit...

I'm order some replacement motors for the Solo. I called RC distributor here in the US and they were out of the particular T-Motors, so I asked for a suggested alternate....He recommended SunnySky, I'm thinking what....

Anyway he goes on to say that actually SunnySky manufactured T-Motors products for years and may still produce many of the offerings. Needless to say my jaw dropped open. He said the RC motor business is really strange and it's really hard to say who makes what at times.

I'm in manufacturing, so some times people's choice of words are misleading. "Built" and "Assembled" are two different things in my world. I think the variable on these motors is that one company does the winding of the stators for many companies. They may use another's components, but the other does the work. It makes sense if your business and people are geared to winding motors.

I asked what the possibility of a domestic US manufacture of brushless motor. He said they are too expensive to compete with the foreign made product.... They are basically hand made, at least wound by hand. It's a small world in the brushless RC motor world it appears...

Maybe he mislead me with his information in some way, but this makes the business of MR that much more interesting.

Good luck 3DR, you have the odds stacked against you, yet again. I'm not giving up.
 
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