All ball bearing motor

[Andy]

I have a bench grinder that i bought in 1986. The label says "all ball bearing motor." Is that motor different than other motors?

[trader_4]

Generally there are two types of bearings, ball or sleeve and ball ones cost more and are better for many applications, including that they can be replaced in many cases if they wear out. On the other hand it a sleeve bearing lasts the life of an infrequently used, not so expensive thing, it can be well suited to the application.

[Rod Speed]

Andy [e-mail] wrote

Yep. not all motors have nothing but ball bearings.

[Ed Pawlowski]

Female motors have no balls. They have sleeves.

[Mike Oxbern]

And some of them have a high-pitched whine.

[Clare Snyder]

It's different than motors with plain bearings - or the odd one with needle or roller bearings.

[A K]

thanks trader_4 for the detailed info.

Andy

[micky]

Worth noting that car engines have only sleeve bearings, but they get long life out of them by making them of special material and by inserting oil under pressure between the bearing and the rotating shafts. My guess is that roller bearings and ball bearings wouldn't work at the high rpm of car engines, or at least they wouldn't work better, though maybe i'm wrong and some engines I'm not acquainted with do use them.

OTOH, car wheel bearings are roller bearings, and they are replaceable. When one of your wheels rumbles when the car is moving, it may be the wheel bearing.

[Ralph Mowery]

Ball bearings work fine at engine speeds. They only run around 3000 rpm or less normally, but up to 5000 t0 10000 rpm for short periods of time.

One reason for the ball bearings in wheels is it is very difficult to put oil to them under pressure.

It it the oil and grease that keeps the metel parts seperated so they do not wear.

Electric motors often run at 3600 rpm or more with ball bearings and grease.

[rbowman]

Consider what an automotive crankshaft looks like. How do you get the ball bearings on the journals?

Some motorcycles use roller and ball bearings but you are essentially building the crank out of pieces and the crankcase splits perpendicular to the centerline of the crank.

[gfretwell]

You could use individual roller bearings like they use in a transmission but the babbit bearings work so well no engine manufacturer wants to spend the money.

[Xeno]

FWIW, sleeve bearings are used up to 150,000 rpm. Think turbochargers. In operation, hydrodynamic lubrication keeps the metallic components separated by a thin oil film.

They were generally two stroke engines and cars also used them, like the Goggomobile, early Suzuki LJ 50s and several other Japanese marques of the same era. Not sure if Saab 2 strokes used built up crankshafts. The difference was the lack of pressure lubrication so the more usual hydrodynamic lubrication systems wasn't an option. Two strokes also needed to fill up dead space in the crankcase so it could be used more efficiently as a pump. This meant the crankshaft webs were quite bulky lending themselves to press fit crank pins. roller and ball bearings are known as anti-friction bearings so were a benefit in small two stroke engine in reducing the parasitic losses associated with friction.

[Xeno]

Not ideal. The ball would need to run across a *joint* and the effect would be to wear away/hammer at the edges - bit like how a pothole in the road grows as cars pass over it.

Babbit hasn't been used in engine bearings for yonks. It pretty much faded from the scene around the time I entered the motor trade and split shell bearings came into general use. Babbit cannot handle the speeds and loads of modern engine crankshafts.