Why do engine bearings look like this:

and not this:


I don't even know how the top ones could be considered a bearing, since they have no moving parts???

With interfaces like rod bearing, the important thing is very tight tolerances to reduce play or slop in the joint. The more moving parts you have, the more slop is present. Where something simply spins and has no forces from the side, like in a transmission, roller bearings work well. But a crankshaft experiences high forces from the side.

Take a look at the crankshaft...any crankshaft. Notice how it is designed.

Only place a roller bearing could work would be the front of it.

And a bearing does not have to be a roller in desgin. Bearings are designed for one thing only, and that is to cut down friction. So long as the bearing material is softer than the metal it is protecting. Often times cam, main, and rod bearings are known as "sacrificial" bearings because they WILL wear out before the assemblies do.

So shouldn't they technically be called bushings?

bearing: a machine part in which another part (as a journal or pin) turns or slides

bushing: usually removable cylindrical lining for an opening (as of a mechanical part) used to limit the size of the opening, resist abrasion, or serve as a guide

This is the Merriam-webster definitions

The whole thing to remember is that the metal ideally never makes contact with metal. The crank actually floats suspended on a layer of oil that keeps it from contacting the bearing.