HEATER / AIR CONDITIONER VENTS
The operator has complete control of the air flow in the
cab. The heater/air conditioner vents (5, Figure 5-2)
are a flapper type which may be individually opened or
closed and may be rotated 360° for optimum air flow.
There are four (three not shown) across the top of the
panel, two in front of the operator (one each in right
and left panel modules), and four below the panel.
INSTRUMENT PANEL
The Instrument Panel (7, Figure 5-2) includes a wide
variety of switches, gauges, and indicators. Refer to
INSTRUMENT PANEL AND INDICATOR LIGHTS, for
a detailed description of function and location of these
components.
GRADE/SPEED CHART
The Grade/Speed chart (8, Figure 5-2 & shown here)
provides the recommended MAXIMUM truck speeds
for descending various grades with a fully loaded truck.
The operator should reference this chart before de-
scending any grade with a loaded truck. Proper use of
Dynamic Retarding will maintain a safe speed.
Two lists are provided, one a continuous rating and the
second a short-term (3-minute) rating. Both lists are
matched to a truck at maximum Gross Vehicle Weight.
The continuous numbers on the chart indicate the
combination of speeds and grades which the vehicle
can safely negotiate for unlimited time or distance.
The short-term (3-minute) numbers listed on the chart
indicate the combination of speeds and grades which
the vehicle can safely negotiate for three minutes.
These speeds are faster than the continuous values,
reflecting the thermal capacity of various system com-
ponents. System components can accept heating at a
higher-than-continuous rate for a short period of time
beyond which the system would become over-tem-
perature.
If the vehicle is operated at short-term grade and
speed limits for a period of time greater than three
minutes, the retarding effort may begin to reduce,
resulting in vehicle acceleration. The service brakes
are available to slow the truck within the continuous
level. This reduction in retarding effort will be gradual
as the vehicle moves from the short-term limits to the
continuous limits.
The “three-minute” curve is a minimum and the actual
time limit could be greater. Ambient temperature, baro-
metric pressure and recent motor power levels can
affect this number.
The three-minute rating will successfully accommo-
date most downhill loaded hauls. It is necessary to
divide haul road grade segment length by allowable
speed to determine actual time on grade. If actual time
on grade exceeds the allowable amount, the grade will
need to be negotiated at the continuous speed.
DO NOT exceed these recommended MAXIMUM
speeds when descending grades with a loaded truck.
This decal may change with OPTIONAL truck equip-
ment such as: wheelmotor drive train ratios, retarder
grids, tire sizes, etc.
ALWAYS refer to this decal in the operator’s cab,
and follow these recommendations for truck operation.
N05044 Operator Cab Controls N5-5
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