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|  MIL-T-62255C(AT)
3.3.2 Service brakes. Service brakes stopping distance shall be in accordance with the
requirements of Federal Motor Carrier Safety Regulation 393.52. The anti-skid requirements of
Federal Motor Vehicle Safety Standard 121 shall not be furnished or its components and
accessories installed on the vehicle. A means shall be furnished and installed to decrease the
braking forces on the front wheel brakes when the anti-skid requirements are not furnished.
3.3.2.1 Parking brake. Parking brake shall be furnished. Parking brake shall be in
accordance with Federal Motor Carrier Safety Regulation 393.41.
3.4 Chassis components.
3.4.1 Engine. The engine furnished shall be the chassis manufacturer's standard or optional
engine for the commercial vehicle which meets or exceeds the requirements of this specification.
Vehicle shall be equipped with a liquid cooled, compression ignition, two-stroke or four-stroke
cycle diesel turbocharged engine, with not less than six cylinders. Engine net horsepower figures
used in the performance prediction calculations shall be determined in accordance with
SAE J816. Maximum net engine torque shall be not less than 550 pound-feet at
1800 revolutions per minute, and develop not less than 225 gross horsepower at
2,600 revolutions per minute (rpm) and provide an engine torque of 455 pound-feet at 2,600 rpm.
The engine shall not display any oil downstream of the exhaust system when engine is idling at
manufacturer's recommended idle speed. Fuel consumption shall be observed in the selection of
the engine and power train requirements in accordance with 3.2.14. Certify that the engine is
matched and rated for use in conjunction with interfacing components.
3.4.1.1 Filter, coolant system. A filter for the coolant system shall be furnished. The filter
shall be of the spin-off type for filtering of the coolant contaminates.
3.4.1.1.1 Fan clutch. A thermostatically-controlled fan clutch shall be furnished and
installed for the cooling system. Vehicle performance shall be with the fan clutch and fan
engaged. Fan clutch shall have a positive lock-up in case of failure of the air control system.
Fan bolts shall be Grade 8 in accordance with SAE J429. Bolts shall be torqued. Fan and fan
clutch assembly shall be of aluminum to decrease stress on the fan shaft.
3.4.1.1.2 Fan shroud. Fan shroud shall be furnished. The fan shroud shall be around the
perimeter of the engine fan and shall be securely fastened to preclude vibration of any
component, and shall be capable of removal for service of front engine components.
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