MOTOR TRUCK SERVICE MANUAL
BRAKES-AIR
ROCKWELL-STANDARD
STOPMASTER BRAKES
The Stopmaster Brake is a wedge actuated brake.
The brake power unit forces a wedge between two rollers and two plungers. This causes the plungers to spread apart and
push the brake shoes against the brake drum.
There are several variations of Stopmaster Brakes in use. Some have two power units per brake and others only one.
Where two power units are used, there may be a Fail-Safe unit on one or both. The brake support may be either a cast
spider or a stamped backing plate. On the cast spiders, the plunger housings may be either integral or bolted on. Brake
shoe adjustment may be either automatic or manual. Other minor variations are also in use.
The various basic Stopmaster Brakes are identified as model RDA, with letters denoting the following: R-Stopmaster
Brake, Wedge Actuated; D-Double Actuated; A-Air operated;
RDA
Bolted on Spider Mounted
Integral Plunger Housings
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