Kalmar Ottawa t2, Maintenance Manual

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52 4.3 Brake System – 4 Brakes
Maintenance Manual Ottawa T2 4x2
4.3.10 Brakes
page –
Description
Brake Chambers and Parking Brakes — In the front are two
single chamber units at the wheel ends. These operate the
foundation brakes described below.
In the rear are two dual chamber units at the wheel ends. These
operate both the foundation brakes and the parking brakes.
When there are dual rear axles, brake chambers are typically
mounted on the forward axle, but are sometimes supplied on
both axles.
The brake chamber is designed to move the shoes against the
drums using air pressure. Air pressure is released into the
chamber by the foot pedal. Push rods change the air pressure
into mechanical action to rotate the brake cam shafts. The push
rods in the brake chambers provide a 2.25-2.50-inch (57-
64 mm) range of stroke length.
The second chamber in the dual chamber unit uses the air
pressure to keep a powerful spring compressed. This spring,
attached to the push rod, provides the parking brake action.
When system air pressure falls below 43 PSI, the springs acti-
vate the push rods and apply the foundation brakes. When sys-
tem air pressure rises above the set point, it overcomes the
spring pressure and releases the brakes.
For service, the springs can be released manually if the engine
cannot be started, or if air pressure cannot be restored to the
system.
Slack Adjuster Diagram
Slack Adjusters — Slack adjusters change the distance the
brake shoes have to travel to contact the drum. During each ap-
plication of the brakes, automatic adjusters detect the rotation
of the brake cam shaft. They retain the setting at the point
where the lining contacts the drum. This setting changes as the
drum and linings wear.
Foundation (Wheel) Brakes — The foundation brakes consist
of brake drums on the wheels and shoes lined with friction ma-
terial attached to the axles. Actuated via cams rotated by push
rods in the brake chambers, the shoes are pressed against the
drums. Air pressure controlled by the foot pedal supplies the
force necessary to stop the wheels from rotating.
OTT0012
BRAKE CHAMBER
PUSH
ROD
S-CAM
BRAKE
SHOES
BRAKE DRUM
SLACK
ADJUSTER