Brushless Motors Failing

[danl]

Something else must be wrong if you keep doing bearings but hard to diagnose without pictures or a video, which is a pain to do on this forum unless you have a YouTube account. When you say the front bearing is it the front bearing on the motor you’re talking about?

Front bearing closest to the pinion. I could upload a video to my youtube account but just imagine a motor on the bench squealing as the RPM's climb. I replaced the bearing and the noise went away.

The $50 Ebay motor in my traxxas maxx slash is doing fine with equal the runs as the hobby wing in the kagama. The front end of the traxxas motor is fully sealed but still gets dirt.

My next move is to put a pice of fuel tube over the motor shaft in an effort to shield the output shaft from dirt. I have a Corally Spark coming next week and the hobbywing will be going into that car. I'll also consider moving to another spot for running the cars.

 

[Sandracer_NL]

Its become super dusty this summer with the heat we have been experiencing. My pictures above are a screenshot of a video I took showing the dust around the front of the motor. The bearing picture is after I removed it. There was grease on the outside of the bearing, as if the front bearing seal facing outward had failed some way.

An o ring between the motor and the pinion and grub screws in the unused motor holes helps a lot. And better motor bearings.

 

[danl]

An o ring between the motor and the pinion and grub screws in the unused motor holes helps a lot. And better motor bearings.

Motor holes are now filled on all my motors. Moving forward they all now have 3 mm of a silicone hose over the output shaft. I do not have o rings in that size.

I don’t have great bearings in it at the moment, but I’ll be ordering some skf ones when I find a supplier I trust to not be selling counterfeits.

 

[danl]

Delete

 

[Nelson.81]

I think it might just be a case of bad luck pretty strange doing the same motor bearing especially only on 4s but not having any other bearings failing on the car if it was the conditions your running in would maybe expect to see other bearings fail too. When it’s installed make sure there’s no movement in the motor mount or the diff only other thing I can think of but you would expect to see pinion gears getting chewed up if that was the case. Dunno lol good luck with it

 

[danl]

Pinion gear life has been exceptional. I always check that I have a bit of backlash and check at multiple points when rotating the spur. I go through inner rear wheel bearings on all my cars. I probably get 50 runs before one or more needs replaced. I get 100 or so packs before fronts need attention.

There was zero in/out play with the new hobbywing motor and it felt "tight" out of the box. When I put the new bearing in I set it up such that it has 1-2 thousandths of free play. I have a new Grizzly 825 (stock kagama LE motor) and it has a slight bit of endplay so I set the hobbywing up just like that and I'll see how it lasts.

 

[danl]

Ok, so quite a few runs between now and my last update. The hobbywing setup was moved to a corally spark and has 6+ runs on it after I had to replace the pinion side motor bearing. I installed a felt ring around the motor output shaft, adhering one side to the motor case with the appropriate 5mm hole for the motor shaft. I am running a non sealed front bearing because that is all that I have on hand. The motor still runs very smooth, no shaft play, etc. The motor has been "overheated" by seeing 180F for a bit. I am still trying to get a cooling fan on it. For reference my 9200mah packs give me around 30 mins of run time. So I'm about 3 hours in without issue on that car.

The Kagama LE has a Kuron 825 that ingested a lot of dirt. I sealed the area around the motor wires with RTV. I cleaned out the dirt/debris. I filled the unused mounting holes in the front of the motor with grub screws or RTV. Finally I put a piece of silicone tubing over the output shaft before putting the pinion back on. The LE has about 6 runs on it as well but it sees more time around fine dirt. The same 9200mah packs only last 10-15 minutes in the LE. So far all is well on this motor.

The traxxas maxx slash, 6-8 runs on 5000mAh 6S packs. The truck lasts 10-15 minutes with my driving style. It has seen 160F but typically stays under 150F. This guy is running the $50 1750KV Ebay motor recommended earlier in this thread. These motors are a tank. This guy has taken heat and while the traxxas is more protected from dirt, it still gets exposed to a lot of dirt since I drive this truck like a goon. These are great motors and will probably be my basher motors in the future.

I think dirt, specifically fine dirt is contributing to front motor bearing life, at least on the LE. Even with a chassis net I hurt the hobbywing. The front of the motor needs a shield of some sort to keep dust away from the motor output shaft in my experience. I am not sure but I think the cooling fans blowing down from the top are flowing dirt down and onto the motor and some of it may be getting exposed to that motor bearing. I noticed on the spark that being a buggy body, it does not get nearly as much dirt in it running nearly twice as long in the same bashing area. The way the corally motor mount is it seems to form a shield for the motor with the pinion installed, but I have pictures where there is clearly dirt packing into that area. I also saw how the bearing seal was damaged and grease was leaking, after only a handful or runs.

I'll update if folks think this is useful.

 

[AggyMi]

very insightful post. I must say coming back to this hobby from 35 years out of it, I'm still quite shocked how all of the big brand bashers all have a bit of spur and pinion exposed to the elements. Dirt and gear grease just forms an abrasive paste, which cant be good. Most of those Tamiya gearboxes way back when were completely sealed, the only place you had dirt ingress was through the brushed can vents.