SECTION VII.
MANUFACTURER’S DATA
AIR-OVER-HYDRAULIC POWER CLUSTER
8-1.
GENERAL
The power cluster, used in an air-over-hydraulic actuating system, has an air cylinder and a standard hydraulic brake
master cylinder which are aligned upon the cluster mounting bracket. This unit provides a 15.1 pressure ratio so that a
maximum 1500 psi hydraulic pressure is secured at approximately 100 psi applied air pressure. Units are produced In
four sizes, matching the standard master cylinder sizes used on medium and heavy commercial vehicles.
8-2.
HOW THE CLUSTER WORKS
a. Air Cylinder’ Air, entering, forces the piston and rod to stroke the hydraulic cylinder and compress the air piston
return spring. The piston also strokes a spring loaded stroke indicator rod which extends through a drilled bolt, one of
those mounting the air cylinder. The cylinder shell wall is sealed by a cup carried on the piston, which also carries a felt
wiper that cleans and lubricates the wall. A boot stretched between the piston and the cylinder head excludes dust,
moisture, and oil from the opening into the hydraulic cylinder. Air displaced on the atmospheric side of the air piston
passes through a filtered breather located in the air cylinder head.
8-1
