CHAPTER XXIV

YOUR BEARINGS

Ever stop to count up how many bearings there are about your car? If you haven’t, you are likely to lose your bearings while you hunt for the several hundred bearing points of the modern automobile.

A bearing is a support for a moving member, so designed as to minimize friction and receive wear, and to permit of fine adjustment.

There are many types of bearings, some in which the metals are selected with the idea of obtaining strength rather than non-friction qualities; others have strong metal shells lined with a comparatively soft non-friction metal. In these bearings moving members slide over each other.

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.

The fan usually runs on ball bearings which are lubricated with a squirt can; being usually of the cup and cone type, they are adjusted by tightening the cone. The water-pump bearings are lubricated by compression grease cups; when the bearings become badly worn it is necessary to drive out the bushings and replace them; generally the shaft also will need replacing. When this shaft becomes worn out of round, no amount of tightening of the stuffing box will prevent water from leaking out.

The valve-stem guides are sometimes bushings, but more usually are holes bored through the cylinder casting. In the former case, when wear occurs the bushing may be driven out and a new one, with new valve, installed; in the latter case, the holes must be reamed true and larger, and valves with larger stems be inserted.

In the ignition system ball bearings usually are employed, with or without means of adjustment. These are lubricated with an oil can or packed in grease. There is one bearing of the ignition system which is unique in that some manufacturers advise keeping it free of lubricating substance of any kind. This is the rocker arm of the interrupter on certain makes of magnetos. Other forms of interrupters are so constructed that lubrication is advisable.

The carburetor air-valve bearing operates better if not lubricated, but does wear and need replacing at times. The throttle bearings may be lubricated and would certainly wear longer if this were done. When they do wear air is admitted which is noticeable at low engine speed, causing skipping and irregular running. Then the holes in the casting must be enlarged and larger shaft inserted.

The throttle and spark-control linkage have a number of bearings, which may be of the steel ball and socket type, or a wire bent to fit in an eye. These pins should be frequently lubricated with a squirt can. Usually they are not adjustable, so that parts must be replaced when they become badly worn.

The self-starter motor and generator are usually equipped with ball bearings and are lubricated with a squirt can. Both the motor and generator have a copper commutator on which carbon brushes bear. These are not bearings, strictly speaking, but they do require a very slight trace of oil if the brushes have not been soaked in oil. The commutator becomes worn occasionally and must be smoothed up with fine sand paper, or, if badly worn, must be removed and trued in a lathe.

The other principal bearings throughout the car are usually of ball or roller type, which may or may not be adjustable. Usually the directions for the care and replacement are given in the manufacturer’s instruction book.

In the steering gear there is a plain bronze bearing or bushing in which the shaft is set out of center, so that when wear occurs by twisting the bushing, the sector of the steering gear may be thrown deeper into mesh with the worm and take up the play.

In the transmission gear, in which all other bearings are of the ball or roller type, there will be found often a plain bearing on the forward end of the square or fluted shaft called the pilot-shaft bearing. This is one weak point in many otherwise satisfactory transmissions. When this bearing wears, the operation becomes noisy and the gears are difficult to shift. The transmission must be disassembled, the bushing withdrawn and a new one pressed in.

The steering-gear linkage bearings are usually of the ball and socket type, self-adjusting by means of springs. Steering knuckle bearings are usually bushings which may be driven out and replaced when wear occurs. It usually is necessary to replace the pins at the same time.

The universal joints of the propeller shaft become very noisy when the bearings are worn. In modern construction these bearings are in the form of bushings which may be replaced at small expense. The brake linkage has many bearings, which are clevis and pin. These are non-adjustable, and unfortunately are not often lubricated. When wear occurs the holes may be drilled larger and larger pins be inserted, or the parts may be replaced entirely.

Of course there are scores of other bearings in other parts of the chassis, that with ordinary care last the life of the car. The lubrication and adjustment are usually given in detail in the manufacturer’s book of instructions and need no special caution other than to advise following what is there printed.