I keep looking at all the newly released parts and notice one common thing: they all use ball bearings. Even motors.
Beyond the price concern, why not roller bearings properly sealed?
Here’s a few types:
Needle bearing. I assume they will be ideal for the closed end of the motors
Normal roller bearing. Geardrives? Pulleys? The other end of the motor?
Tapered bearings. Put against each other they could replace the wheel bearings
Thrust bearing. For 2 meeting flat surfaces spinning against each other.
Lastly, an odd one i would like to see on @moon’s wheel gear:
I need to note that 3ds do use roller bearings on a baseplate and on their last geardrive, but their stuff is not at a price i can swallow. Maybe we’ll start to see more affordable options from other vendors in the future
Roller bearings are for super super high loads and are for unidirectional loads only. They’re also very intolerant to misalignment. Mostly though, we don’t see loads big enough to justify these types of bearings. (Besides maybe in a truck pivot)
Also, a lot of your bearings you posted do not use an inner race, making it so the surface they are rolling on requires a very very good quality surface finish. The surface also needs to be hardened to stop wearing too fast. And alu is generally too soft, maybe anodizing is not, but i have not looked at that.
what’s are you thinking the benefit of the combination thrust / normal roller bearing (last one) would be over a tapered roller bearing? Aren’t they both meant to handle both axial and radial loads?
Ball bearings are more efficient for sure, but i feel like a lot of people do not make use of angular ones correctly in a lot of instances, for example helical gears, therefore they tend to wear out their bearings quickly.
I think @Boardnamics is very on point with this, and actually thats why all electric outrunner motors from china have TWO bearings in the back, so they can be swapped for angulars in case of helical gears. Not five or four bearings
Yea, thats what i meant why motors have two on the back.
I have noticed for example with my home made belt tensioners (two bearings next to eachother) that they do not like the sideways movement of the belt. They started to click nearly instantly.
Also in my experience a wrongly aligned belt that wants to move creates some nasty movement to the side when its rubbing against the wall of the pulley, creating more strain on the motor bearings. And making them run a lil worse.
But, from what i have read i think you did your maths on this so thanks for your info, i think you are correct.
The two bearings on the back are just for good measure, I think. It costs almost nothing to incorporate something like that. Most motors have one bearing in the front and one in the rear. One takes thrust load in one direction, the other in the other direction. As you’re riding helical gears, the thrust load is constantly changing from the front bearing and the rear bearing. (accelerate and brake).
I am not explaining it right but incorporating AC bearings is more complicated than just slapping another bearing somewhere. The bearing has to sit against some kind of step in the shaft or it has no ability to bear thrust loads.
I see, interesting. We have been talking to an electric motor guru and he said one of the reasons they have two is because these motors are made without a specific use in mind because the designer does not know what forces are going to act on it.
Therefore they generalize their design to take in mind several forces. He indeed also mentioned “concentricity” if thats a word.
Yes, it is true. Adding a second radial ball bearing is cheap, easy to implement, and essentially doubles the radial load rating. It would do much for thrust capabilities.
I don’t think the failure rate is high enough on our current motor’s designs to warrant a completely new motor structure being made. One thing to keep in mind also is it’s not easy to just increase the size of the bearings in the motor. A bigger bearing means less space for stator iron.
