Three types of bearings are being used by the manufacturers of automobiles and gasoline engines. They are, namely, the plain bearing or bushing, the solid and flexible roller-bearing, and the double and single row of self-aligning ball bearings.

Bearings were designed to prevent wear and friction between parts, which operate on, or against each other.

Fig. 139 shows three types of plain bearings. A, the split type of plain bearing, is used widely by the manufacturers of engines as main bearings to support the crank shaft and at the large end of the connecting rod. B is a cylindrical type of plain end bushing, used to support light shafts in end walls. C is a center or sleeve type of plain bushing.

All three types of plain bearings described above will stand unusually hard use, but must be kept well lubricated or run in an oil bath to prevent frictional heating and excessive wear. Fig. 140 shows two types of shims used between the retainer jaw of a split bearing, which allows the wear to be taken up when the bearing gets loose and begins to pound. The shims may be either solid or loose leafed, and are of different thickness. The loose leafed shim has an outer casing, which contains seven to ten metal sheets of paper-like thinness, which may be removed to the exact thickness required for an accurately fitted bearing.

Fig. 141 shows the Bock type of radial and end thrust roller bearing. The end of each roller is provided with a section of a perfect sphere which rolls in unison with the tapered rollers and makes the end contact practically frictionless. The advantage claimed for this type of bearing is that it embodies both the ball and roller bearing strength and reduces the friction on the roller and thrust end to a minimum. This type of bearing is used in the hub of the wheel, which must be cleaned and well packed with a medium grease every thousand miles. The bearing is best cleaned by dropping it into a container of kerosene and scrubbing it with a stiff paint brush. Do not run the car with the hub cap off.

Fig. 142 shows the Hyatt flexible type of roller bearing. This type consists of an inner and outer race and a cage which holds the flexible rolls. The flexible rolls are spirally wound from a high grade sheet alloy steel. The rolls are placed in the cage in alternative positions. This arrangement of rollers has a tendency to work the grease back and forth on the surfaces of the races. Another advantage claimed for this type of bearing, is that the weight is more evenly distributed at the point of contact, due to the fact that the wound rolls allow a certain amount of resiliency, and accepts road shocks easily, which reduces the amount of frictional wear to a minimum. This type of bearing requires the same attention as the Bock, described above.

Fig. 143 shows a type of double row ball bearings. Ball bearings are being used more extensively each year by the manufacturers of light and heavy duty motor vehicles. The efficient reliability and ease of action has proven to be the main factor in the development of this type of bearing. One of the big features in considering ball bearings is that a ball rolls equally well in any direction, and the slightest effort will start it to rolling. It is a proven fact, that a ball is started more easily than any other type of supportive element. This explains why ball bearings of all types come nearest to being frictionless. Once upon a time people believed that the ball in ball bearings carried the load by point of contact, which is not true, as ball bearings carry the load on a definite area. And in bearing construction, such as shown in Fig. 143, where the inner and outer race curves around the balls and increases the contact area, the contact capacity is greatly increased. Thus a one-fourth inch S. K. F. ball showed a crushing resistance of nine thousand and seven hundred pounds, while the one-half inch ball showed a crushing strength of twenty-five thousand pounds. The sectional view of a radial bearing, shown in Fig. 142, consists essentially of four elements, which are the following: (a) The outer ball race, (b) the two rows of balls, (c) the ball retainer, and (d) the inner ball race.

The inner surface of the outer race is spherically ground in the form of a section of a sphere whose center is the center of the axis of rotation. This provides that both rows of balls shall carry the load at all times. This reduces the load carried by each ball to the least amount.

The ball retainer is made of a single piece, which provides for proper spacing of the balls, and positively circulates the lubricant. The retainer is open at the sides, which permits free access of lubricant, and makes inspection easy.

The inner ball race contains two grooves to accommodate the two rows of balls, and the curvature of the outer race is slightly larger than that of the balls. The fact that both inner and outer races are curved gives an ample surface contact between the balls and the races.

Fig. 144 shows a double thrust bearing. This type of bearing was designed to take end thrust in both directions. It is used to stabilize the shaft against lateral motion and to accept reversing thrust loads. It is also automatically self-aligning.

The assembly of balls and races forms a section of a sphere within a steel casing. The inside of this casing is ground spherically to the same radius as the spherical seats, thus permitting the assembled bearing parts to adjust themselves to any shaft deflection.

This type of double thrust bearing is so designed that the central rotating disc, two rows of balls, and the aligning seats are combined in a single unit within the casting.

The unit construction of this type of bearing insures ease in mounting, and eliminates much costly machine work usually encountered in setting double thrust bearings, and renders the bearing practically dirt, dust and fool-proof. If it becomes necessary to disassemble the machine upon which these bearings are mounted, the user has every assurance that the shafts can be relocated precisely in its original position, with the minimum of time, labor and expense. This type of bearing is also entirely free from adjustment, loose parts, costly machine work, and the possible abuse at the hands of inexperienced workman are entirely done away with.

Fig. 145 shows a thrust bearing designed to carry the load in one direction, along the shaft, and consists of two hardened steel discs provided with grooved ball-races, and a single row of balls held in position between the races by means of a suitable retainer.

Cleaning Bearings.—To clean bearings, use gasoline, kerosene, or a weak solution of baking soda and soft water. Place the cleaning fluid in a shallow receptacle, take a piece of wire and bend a hook on the end, place the hook through the center of the bearing and rinse up and down in the fluid, spinning it with the hand occasionally. If some of the grease has dried or baked on the roll or roller guide or retainer and refuses to be dislodged by this method, lay the bearing flat and scrub with a brush which has been dipped into the cleaning fluid.