In addition to this we have the so-called anti-friction bearings, in which balls, or straight, taper, or helical rollers are used, giving a rolling rather than a sliding contact.
On the engine alone there are 102 bearings. This is figured on the average six-cylinder motor; some of them have more than double the number. There are, for instance, the following:
Six cylinders, 6 wrist-pin bearings, 6 crank-pin bearings, 4 main, 3 cam shaft, 12 cam, 12 push rod, 12 valve stem, 2 fan, 2 water pump, 8 ignition, 6 spark control, 6 carburetor control, 6 carburetor, 3 oil pump, 4 self-starter, and 4 self-starter linkage bearings; total, 102.
The first named, cylinder and piston, not generally termed bearings, are usually of cast iron, which gives comparatively long wear and in which the friction is not great if well lubricated. When wear does occur at this point it is necessary to rebore and have larger pistons fitted.
The wrist-pin bearings usually are in the form of a bronze shell, called a bushing, surrounding the wrist pin; when wear occurs it is necessary to drive out the bushing and replace with a new one which fits.
The crank-pin bearings are usually in halves, the metal babbitt or bronze, surrounded by a steel strap or casing. When wear occurs, the adjustment is made by taking out thin sheets of metal, called shims, which allow the halves to be brought closer together. The main crank-shaft bearings are of the same type.
The cam-shaft bearings are usually in bushing form, which must be replaced with new ones when they become worn. The cam-follower bearings may be just flat plates resting directly upon the cam, or rollers running on a pin in the valve push rod. Wear in these parts would usually be compensated for by adjusting screws on the valve push rods.
The push-rod guides are sometimes made of cast iron or other metal, with babbitt or bronze shell in bushing form, and would require replacement when worn.
The oil-pump bearings consist of a plunger working in a small cylinder, with one end bearing against a cam, or a pair of gears driven from the cam shaft. These bearings, being perfectly lubricated, seldom or never require adjustment.
All of the bearings considered so far are cared for by the lubricating system of the engine, which starts when the engine starts to run, and as long as oil is kept in the engine they are quite certain to be taken care of, barring accidental stoppage of the oil lead.