OK, since I've renamed the vibration to Yudders, I can know describe further without offending.
Did finally balance the new #4 motor and it took a .001g piece of tape. The readings were comparable to the other motors now. Still have Yudders, but it's isolating further.
Lets be clear, I'm unsure at this point that motors have anything to do with yudders. The following is just my discoveries and nothing more. The sky is not falling. ymmv.
The original #4 motor, I replaced the bearings in it and was able reduce the balancing weight to .001g rather than the .006g I had on it originally. Learned quite a bit about brushless motors prior to the swap and then more as I installed the new set of bearings. In the end, I succeeded in what I set out to perform and learn.
The short answer, it appears the shaft was spinning within the bearing. At higher RPM the bell will oscillate within the bearing rather than ride on the bearing. This creates an imbalance of the bell housing. I did have a slight tick in the top bearing as well.
Long answer:
First, I never had any issues with motors from my previous brand. They were smooth running. I presumed they are T-Motors. It appears they are one of the better brushless motors out there, as far as mass produced. So I'll use T-Motors as the benchmark for this conversation.
The ticking bearing, it was slight but was easily felt when spinning the bell off the bearing. Not calling it bad. Just in the discovery phase for bearings.
The bearings, the shaft and pre-loading. So here's the deal with bearings in a brushless motor. The bell's shaft does not fit tight to the ID of the bearings. There is a certain tolerance for the fit to allow a non-pressed fit, they slide through. Typically this is resolved by the tolerance in the fit along the shaft. Bearings are spaced by the base housing, the stator actually fits over the base, so the bearing to bearing spacing has fairly close tolerances when properly fitted. Bearing slop is a variable however.
The shaft and the bell housing on the other hand are another variable. The bell housing actually
rides on the inner race of the top bearing. The shaft then passes through the lower housing bearing. There is thrust washer and then a funky cir-clip to hold the assembly together.
At this point the shaft length is very critical to how the motor will run. Too long and the motor will have a abnormal sound to it. Basically it is oscillating within one of the bearings rather than spinning the bearings. You'll sometime hear the motor change pitch at a constant motor RPM. This is the shaft wobbling within the bearing. Not good, the shaft will show polish points on the shaft where the bearing would be. This is wear.
Will assume the shaft was installed properly or it has loosened from the bell, as factory. Either way, the thrust washer should pull the shaft once the cir-clip is installed, compressing slightly the bearings together. As I've read it, this is called pre-loading the bearings. Too much pressure and you bind the bearings. Too little and the shaft can wobble.
Not saying the brass thrust washer used is no good, but motor #4 did have a polish on the shaft. Originally it required the heaviest weight of .006 to be used out of the four motors. It now takes the lightest weight, .001g. At this point I've only done this motor. I'm still working on a method to separate the pod from the motor so that I can reassemble like factory.
I used a T-Motor Washer 3.175mm, which appears to be a nylon material as a replacement thrust washer. It was slightly thicker than the brass washer by about 0.3mm. Understanding nylon like I do, it will compress with a certain amount of pressure. Further is will not deform, melt at operating temperatures or wear easily. It provides the correct compression for the bearings, with all other components being correct. At least based on this first install. Preloaded bearings, no shaft oscillations.
Bought the T-Motor cir-clips as well....
It all fits...like I knew what I was doing...
I bought the bearings through a local dealer/mfg to me here in Houston, seemed to have a following in the RC car world. The stated spec's were spot on for my set of calipers, so tolerance are very good. I would imagine RC cars are more demanding on bearings than drones, so I choose them for the bearings. That's pretty much what they carry btw... And a heck of a lot cheaper than others...Tell them RichWest sent you....maybe I'll get a hat.
Avid Racing Concepts LLC | RC Bearings and Accessories for radio controlled vehicles - shipped Monday AM, recv'd by Tues.
Top 1/8 x 5/16 x 9/64 Metal
Bot 1/8 x 3/8 x 5/32 Metal
Helidirect - these guys took two days to ship, recv'd on Thur.
T-Motor thrust washer and cir-clip...
Tapping the bearings out was no big deal, plenty of videos showing the process. I made a tool to install the bearings, pretty slick actually. Again plenty of videos showing ways to install bearings. Do your research prior to messing with bearings.
FWIW, Again these are just my notes from my discoveries. If I'm wrong, please feel to correct me. I really don't recommend changing the bearings in the Solo's motor pods just yet. it's fairly involved at this point, more so than many here should attempt. FWIW, bearings or motor pods will eventually need replacing. It's part of the game and a wearable part.
If you've read this far, I bet you can't wait till I start discussing my discoveries about Cogging... Again, another thing that T-Motors appears to have reduced in their brushless motors.
Good night and good luck!
