Bearing question

[Broncobill78]

Ok, perhaps a silly question but can anyone tell me why main, cam & rod bearings are called bearings when they're really bushings ? Just one of those stray thoughts that I've always wondered about.

 

[Tennessee Jed]

Bushings are used between two pieces that independently move usually one piece part designed to keep a harder pin, shaft aligned and moving freely in a range or sweeping motion. A bearing may or may not contain rollers of some kind, a rod bearing is a sleeve of metal between two rotating parts with no rollers so the oil pressure acts like the rollers and normally contain two or more parts and turn full revolutions.

Bushings can be plastic or almost any metal. I know old engines had babbitt bearings because the oil pressure was low and types of oil available broke down quick without filtering and detergents. Some old Harley-Davidson engines used actual roller bearings in the engine.

More reading allows this definition: bushings are more appropriate for high impact, low speed joints. Bearings provide better alignment, less friction, and last longer in faster rotating machines.

So in conclusion a bushing is a slower motion device most likely not turning full revolutions to carry a shaft whereas a bearing is faster and does make complete revolutions of the shaft it carries.

Seems like bearings are designed with many load conditions considered like the wheel bearings in the front wheels are designed to carry the weight of the car the cornering forces and load shift from side to side where the thin hard metal of a cam bearing is holding the straight up and down motion of the rocker/lifters.

 

[Broncobill78]

Bushings are used between two pieces that independently move usually one piece part designed to keep a harder pin, shaft aligned and moving freely in a range or sweeping motion. A bearing may or may not contain rollers of some kind, a rod bearing is a sleeve of metal between two rotating parts with no rollers so the oil pressure acts like the rollers and normally contain two or more parts and turn full revolutions.
Bushings can be plastic or almost any metal. I know old engines had babbitt bearings because the oil pressure was low and types of oil available broke down quick without filtering and detergents. Some old Harley-Davidson engines used actual roller bearings in the engine.

More reading allows this definition: bushings are more appropriate for high impact, low speed joints. Bearings provide better alignment, less friction, and last longer in faster rotating machines.

So in conclusion a bushing is a slower motion device most likely not turning full revolutions to carry a shaft whereas a bearing is faster and does make complete revolutions of the shaft it carries.

Seems like bearings are designed with many load conditions considered like the wheel bearings in the front wheels are designed to carry the weight of the car the cornering forces and load shift from side to side where the thin hard metal of a cam bearing is holding the straight up and down motion of the rocker/lifters.

Well, it was always my understanding that the moving parts in the engine rode on a "wedge" of oil once pressure was built and that was what prevented the metal-to-metal contact and I know Mopar screwed around with needle bearing mains back in the 60's but found that there was no real HP advantage to it since the existing system (shell-type bearings) let the crank,rods & cam ride on that wedge and there wasn't much frictional loss as a result. I seem to recall something about some older VW air-cooled engines having needle-bearing mains but drew a blank on anything else.

I just always wondered why something that was so obviously a bushing was constantly refered to as a bearing.