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MIL-T-62255C(AT)
3.3 Performance. Vehicle will operate primarily in shipping terminals, shuttling transport
semitrailers from ship side to marshalling yards and trailer transfer points. Vehicle shall be
capable of operating on Class I roads in accordance with TABLE IX of SAE J688 and grades
and speeds specified herein.
3.3.1 Speeds and gradeability. High and low speed requirements shall be met with the truck
tractor loaded to specified GCWR.
3.3.1.1 Gradeability. Vehicle shall be capable of ascending a continuous grade of
1.0 percent at 20 miles per hour (mph). Gradeability shall be verified with calculations in
accordance with SAE J688, Truck Ability Prediction Procedure (see 6.3). Gradeability in low
gear shall be not less than 27 percent. Calculations shall indicate:
a. Ratio, revolutions per minute and miles per hour in each range.
b. Torque, horsepower and revolutions per minute and calculated grade that the GCW will
be capable of ascending in each of the forward gear ranges.
c. Cooling system calculations to verify cooling requirements at minus 25F ambient
temperature and the grades that the vehicle will be subjected to as specified in 3.1.1.3 and
3.3 as specified herein.
3.3.1.2 Low speed. Low speed shall be calculated with engine operating at not less than
35 percent of the recommended governed speed, and shal1 provide not more than three mph.
3.3.1.3 Reverse speed. The vehicle shall be capable of a reverse speed of five to ten mph.
3.3.1.4 Maximum geared speed. Maximum geared speed at engine governed speed shall be
35 mph, plus or minus 15 percent. Conformance to geared speed specified shall be determined
by calculating in accordance with the following formula:
Maximum geared speed (mph) =
Governed speed (rpm)_______
Total gear reduction x (tire factor)
3.3.1.5 Inching capabilities. Inching capabilities shall be demonstrated from a smooth
forward or reverse starting position.
3.3.1.6 Sustained operation. The vehicle shall be capable of sustained operation for 10 to
12 hours without scheduled maintenance or servicing.
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