MIL-T-62255 Truck Tractor, Yard Type, 4 X 2, Xm878This specification covers diesel engine driven, four-wheel, two rear wheel drive truck-tractor, yard type, with a one man half cab, having a minimum gross vehicle weight rating GVWR of 43,500 pounds and a gross combination weight rating GCWR of 100,000 pounds. Vehicles under this specification shall be procured only from a manufacturer who meets the standard commercial and commercially proven component criteria. Vehicles shall be warranted by the manufacturer as specified in the procurement documents.

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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 25°F 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.