TM 9-2350-247-10THEORY OF OPERATION 0003 00GENERAL INFORMATION: M548A1The M548A1, 6-ton tracked cargo carrier is powered by a liquid cooled 6V53, 210 horsepower diesel engine. The enginepower is converted to mechanical power and transferred to the carrier tracks and other components through a transfergearcase, transmission, differential, and final drives.The engine, transmission, and steering/braking system are driver controlled. Engine startup and shutdown are controlled byelectrical signals and mechanical linkages connected to the accelerator pedal, the fuel shutoff cable, and the hand throttlecable. Steering/braking are controlled through linkages connected to the differential.ENGINE AND DRIVE TRAINThe engine converts air and diesel fuel into energy. The engine delivers this power to the transmission. A drive train transferspower from the engine to the carrier tracks. The drive train consists of the engine, transfer gearcase, transmission, differential,drive lines, final drive assemblies, and drive sprockets.COOLING SYSTEMThe engine and transmission generate heat during normal operation. The cooling system transfers some of the heat to theoutside to maintain a safe operating temperature. The vent fan draws air in through the radiator, circulates it around the powerplant, and expels it through the exhaust grille above the vent fan. The vent fan is belt-driven from the engine crankshaft. Amixture of antifreeze and water is pumped through the cooling system to cool the engine and transmission. The enginecooling system has a capacity of 9.5 gallons (35.96 liters). The cooling system should be checked regularly. The auxiliaryradiator tank, located on the transverse beam, provides space for the separation of air and liquid coolant. Stop engine iftemperature goes above 200F (93.3C). See Cooling System illustration in Location and Description of Major Components(WP 0002 00). Refer to Check/Fill Cooling System (M548A1) (WP 0065 00).COLD START SYSTEMThe engine is equipped with a cold start system (air box heater). The air box heater heats the air entering the cylinders toassist in ignition of fuel at low ambient temperatures (below 40F (4.4C). A fuel and air mixture is sprayed into the air boxand a spark ignites a flame. The flame heats the engine air, which is fed directly into the cylinders to make starting easier.DIFFERENTIAL STEERING LEVERSThe differential steering levers are used to steer as well as stop the carrier. Pulling on one or both of the differential steeringlevers applies the brakes in the differential steering unit. To turn left, gradually pull on the left steering lever. To turn right,gradually pull on the right steering lever. To slow or stop the carrier, gradually pull both steering levers. To lock the steeringlevers in place, push down on the brake lock buttons, located on top of the steering levers. To release the steering leversbrake-lock buttons, pull back on the steering levers and the buttons will pop up.PIVOT STEER LEVERSThe pivot steer levers are used to steer the carrier while in water and to turn a stopped carrier in a tight turn. To pivot steer thecarrier, bring the carrier to a stop and pull on the pivot steer lever. Pulling the pivot lever applies the disc brake, which willlock up the one track and allow all of the differential power to be applied to the other track.TRANSMISSION SHIFT CONTROLLERThe transmission shifter is used to select driving range of transmission. The transmission shifter has six positions to choosefrom. See driver’s controls (WP 0004 00) for a description of each position. There is a neutral safety switch to make sure theengine only starts with the transmission in neutral.0003 00-1
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business