BRAKE TYPES, OPERATION AND CARE
An automobile is always equipped with two sets of brakes, as they are
required by law. The functional action of the brakes is to check the
motion of the car when the driver wishes to stop or reduce the rolling
speed. The service brake usually operates on the external surface, or
on the outside of the drum flange, and is connected to the right foot
pedal through a set of linkage. The emergency brake operates on the
internal surface of the drum, and connects through linkage to a hand
lever operating on a notched quadrant. The service brake is used in
ordinary driving to check the rolling motion and to stop the car. The
emergency brake is used to assist the service brake and to hold the
car, in case the driver wishes to allow it to stand on a grade.
Fig. 124 shows a set of brakes assembled on the axle ready to receive
the horizontal flange of the brake drum. The brake drum is attached to
the wheel; consequently when a wheel has been removed and is about to
be replaced, the first operation consists of starting the drum flange
into the space between the lining of the external and internal bands;
care should always be exercised in making this adjustment, in order
not to burr the outer edge of the lining, as a brake with an uneven
frictional contact surface is of little value in checking the motion of
the car.
In Fig. 124, A shows the position of the band on the inside of the
drum; B shows the contracting tension coil spring which holds the
bearing surfaces of the band in contact with the flat surface of the
cam when the brake is not in use; C shows the cam shaft, and the flat
surfaces of the double action cam, which expands the band and brings it
into even contact with the inner horizontal surface of drum flange,
thereby checking the motion of the wheel by frictionally grasping the
drum.
The service brake shown in Fig. 124 is of the external contracting
type, which operates on, or frictionally grasps the outside horizontal
surface of the drum. D shows the lined band, which is held in a
stationary position from the rear; E shows the leverage arrangement
with its expanding coil spring, which holds the band free from the
drum, when the brake is not in use; F is the lever to which the pull
rod is connected; G is the lever on the internal brake cam shaft to
which the hand lever is connected by the pull rod.
[Illustration: Fig. 124. Brake--Types and Adjustment]
Fig. 125 shows a new type of internal expanding brake, which is being
used on many of the late models. The brake band in this case is
supported at three points and has an adjustment at the rear main point
of support. The cam has been done away with, and the band is expanded
by a leverage toggle arrangement which operates through a much larger
area, and is more dependable as there is no danger of its “sticking” or
turning over, as was often the case with the cam.
Fig. 126 shows another type of service brake which may be encountered
on a few of the former models. This type of brake is usually located
on the propeller shaft at the rear end of the transmission case. This
type of brake operates in the same manner as the service brake at the
end of the axle.
[Illustration: Fig. 125. Brake--Showing Toggle Arrangement]
Fig. 126 shows an equalizer which allows for any difference that may
occur in making adjustments.
[Illustration: Fig. 126. Transmission Brake--Equalizer]
Fig. 127 shows the complete brake assembly, and the points of
adjustment on late Buick cars.
=Brake Adjustment.=--All types of brakes are adjustable. The service
brake usually has two adjusting points, one at the drum, which is made
by turning the nut on the leverage pull pin, and another on the pull
rods. A long neck clevis, or a long butted turn buckle will always be
found on the pull rods, or on the rod leading to the equalizer. The
adjustment is made by turning either to the right to shorten, or take
up, and to the left to lengthen. The clevis is always threaded to the
right, while the turn buckle has a right and left thread which carries
each end of the rod into the butt when it is turned to the right.
The lock nuts must always be turned up tight to the butts after the
adjustment is made in order to hold it.
[Illustration:
BRAKE SHAFT
SERVICE BRAKE PEDAL
PULL RODS
ADJUSTING TURNBUCKLE
EMERGENCY BRAKE
LEVER
INTERNAL BRAKE SHAFT
EXTERNAL BRAKE SHAFT
ADJUSTING THUMB SCREW
ADJUSTMENT
INTERNAL BRAKE BAND
EXTERNAL BRAKE BAND
Fig. 127. Brake--Arrangement and Adjustment--“Buick”]
=Brake Care.=--A great deal depends upon the proper operation of the
brakes. They should be regularly inspected at least once a month for
loose adjustments and uncleanliness. The need of adjustment usually
occurs from natural wear, while an unclean frictional surface is
usually the result of oil or grease seepage through the outer axle
bearing. A felt washer is provided to prevent this from taking place,
but as these washers are subjected to considerable pressure, they often
become caked and hardened and lose their absorbing effectiveness. These
washers can be purchased at any accessory store for a few cents apiece,
and applied with very little trouble.
=Cleaning the Surface of the Brake Bands.=--This is accomplished by
removing the wheel and washing the friction contact surface with
gasoline, after the surfaces have become thoroughly dry. Drop three or
four drops of castor or Neat’s foot oil on the contact surfaces of the
drum, and replace the wheel and spin it a few times before releasing
the jack.
=Caution.=--After you have set the gears for starting, and before you
release the clutch pedal, always reach and make sure that the emergency
brake lever is in the neutral position. New drivers invariably forget
to do this, which results in severe strain on the bearings, and causes
them to get loose; the average brake band will not stand more than
fifteen to twenty minutes of continuous contact before it burns or
wears beyond the point of usefulness.