Table of Contents
Advertisement
OM3245 8/11
DYNAMIC RETARDING
Dynamic retarding is a braking torque (not a brake)
produced through electrical generation by the
wheelmotors when the truck motion (momentum) is
the propelling force.
For normal truck operation, dynamic retarding should
be used to slow and control truck speed.
Dynamic retarding is available in FORWARD/
REVERSE at all truck speeds above 0 kph/mph.
However, as the truck speed slows below 5 kph (3
mph), the available retarding force may not be
effective. Use the service brakes to bring the truck to
a complete stop.
Dynamic retarding will not hold a stationary truck on
an incline.Use the parking brake or wheel brake lock
for this purpose.
When in NEUTRAL, dynamic retarding is available
only when truck speed is above 5 kph (3 mph).
When dynamic retarding is in operation, engine rpm
will automatically go to an advance retard speed
setting. This rpm will vary depending on temperature
of several electrical system components.
Dynamic retarding will be applied automatically if the
speed of the truck obtains the maximum speed
setting programmed in the control system software.
When dynamic retarding is activated, an indicator
light in the overhead display will illuminate. The
grade/speed retard chart should always be used to
determine safe downhill speeds. Refer to Grade/
Speed Chart in this chapter.
Retarder Lever
Retarder lever (5, Figure 32-2) mounted on the right
side of the steering column can be used to modulate
retarding effort. The lever will command the full range
of retarding and will remain at a fixed position when
released.
• When
the
lever
is
(counterclockwise) position, it is in the OFF/no
retard position. An adjustable detent holds the
lever in the OFF position. Refer to Section J in
the service manual for adjustment procedures.
• When the lever is rotated to full "down"
(clockwise) position, it is in the full ON/retard
position.
• For long downhill hauls, the lever may be
positioned to provide desired retarding effort, and
it will remain where it is positioned.
rotated
to
full
"up"
Operator Cab And Controls - Section 32
NOTE: The retarder lever must be rotated back to
the OFF position before the truck will resume the
propel mode of operation.
The lever and foot-operated retarder/service brake
pedal can be used simultaneously or independently.
The Propulsion System Controller (PSC) will
determine which device is requesting the most
retarding effort and apply that amount.
Brake/Retarder Pedal
Brake/retarder pedal (3, Figure 32-1) is a single, foot-
operated pedal that controls both retarding and
service brake functions. The first portion of pedal
travel commands retarding effort through a rotary
potentiometer. The second portion of pedal travel
modulates service brake pressure directly through a
hydraulic valve. Thus, the operator must first apply,
and maintain, full dynamic retarding in order to apply
the service brakes. Releasing the pedal returns
brake and retarder to the OFF position.
When the pedal is partially depressed, the dynamic
retarding is actuated. As the pedal is further
depressed, to where dynamic retarding is fully
applied; the service brakes (while maintaining full
retarding) are actuated through a hydraulic valve
which modulates pressure to the service brakes.
Completely depressing the pedal causes full
application of both dynamic retarding and the
service brakes. Indicator light (B3, Figure 32-8) in
the overhead panel will illuminate, and an increase in
pedal resistance will be felt when the service brakes
are applied.
For normal truck operation, dynamic retarding
(lever or foot-operated pedal) should be used to slow
and control the speed of the truck.
Service brakes should be applied only when
dynamic retarding requires additional braking force to
slow the truck speed quickly or when bringing the
truck to a complete stop.
Throttle/Accelerator Pedal
Throttle/accelerator pedal (4, Figure 32-1) is a foot-
operated pedal which allows the operator to control
engine rpm depending on pedal depression.
It is used by the operator to request torque from the
motors when in forward or reverse. In this mode, the
propulsion system controller commands the correct
engine speed for the power required. In NEUTRAL,
this pedal controls engine speed directly.
Page 32-3
Advertisement
Table of Contents
Troubleshooting
