BEARING TYPES, USE AND CARE
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.
[Illustration: Fig. 139. Plain Bearings or Bushings]
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.
[Illustration: Fig. 140. Shims]
[Illustration: Fig. 141. Bock Roller 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.
[Illustration: Fig. 142. Hyatt Roller Bearing]
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.
[Illustration: Fig. 143. Double Row Radial Ball Bearing]
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.
[Illustration: Fig. 144. Double Row Thrust Bearing]
[Illustration: Fig. 145. End Thrust Bearing]
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.