الفهرس 
EXPERIMENTAL WORKOnly 14 pages are availabe for public view
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Abstract
This research was carried out aiming to evaluate the brake performance
of one of the heavy duty brakes under variable operating conditions.
For this purpose a test rig was constructed, and equipped ~~th a
Ito-Servo drum brake unit of the type fitted to the rear axle of bus type
SaturnI-HD Deutz,(Nasr/Cairo bus). Proper instrumentations were made for
measuring the applied brake pressure, braking torque developed, drum and lining
temperature as well as the drum rotating speed. The results were recorded
throughout a single and drag brake applications.
The study concluded that the braking torque varies throughout the stop.
The average braking torque increases as the actuating brake pressure increas-
es in a non-linear form, and depends on the initial drum speed during the stop
(for the same actuating pressure and initial lining temperature). The torque
developed reaches an initial maximum value before the lining temperature’
reaches its maximum during the stop.
The coefficient of friction between drum and lining varies during the
stop. It is influenced by both the lining temperature and the initial drum
speed. The coefficient of friction decreases as the lining temperature and
initial drum speed increase.
The lining temperature distribution follows approximately a sin form
along the lining arc. For the primary shoe(floating shoe), the position of the instantanious maximum lining temperature varies with drag time duration.
It moves slightly towards the shoe toe during the drag brake applica-
tions. For the secondary shoe (fixed shoe) the position of the instantanious
maximum lining temperature is independent of the variable operating conditions.
o
It always occures at an angle 90 approximately measured from the shoe pivot.
Drum eccentricity affects both the actuating pressure, braking torque
and lining temperature during brake applications. This effect is recognized
as a periodic function supperimposed on all recorded signals. The periodici-
ty was found to be equal to the time of one complete drum revolution. The
,
phenomenon is influenced by the variable operating conditions.