TM-9-2350-311-20-2
HOWITZER, MEDIUM, SELF-PROPELLED, 155MM; M109A2, M109A3, M109A4 AND M109A5
TECHNICAL MANUAL; UNIT MAINTENANCE MANUAL FOR CAB, ARMAMENT, SIGHTING AND FIRE CONTROL, ELEVATING AND TRAVERSING SYSTEMS AND ASSOCIATED COMPONENTS
DECEMBER 1993
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CAB TRAVERSING SYSTEM
The cab traversing system consists of the gunner’s selector switch box assembly, hydraulic motor, bypass valve assembly
and solenoid, clutch mechanism, and gunner’s control handle. The M109A4/M109A5 howitzers have an additional clutch
valve.
The gunner’s selector switch box assembly is used to electrically switch the cab traversing mechanism between power and
manual traversing.
The bypass valve assembly and solenoid combination controls the hydraulic power between the manual and power
modes. In the power mode, the solenoid will push out the plunger to divert the hydraulic fluid to the hydraulic motor. In the
manual mode, the plunger will retract and disengage the hydraulic motor.
The clutch mechanism controls the mechanical switching between the two modes and is controlled electrically
(M109A2/M109A3 howitzers) or hydraulically (M109A4/M109A5 howitzers). The clutch valve in the M109A4/M109A5
howitzers controls the flow to the clutch.
The gunner’s control handle operates the power traversing of the cab and the manual traverse handwheel operates the
manual traversing of the cab.
CAB TRAVERSING SYSTEM (M109A2/M109A3 HOWITZERS)
POWER PACK
ASSEMBLY
MAIN ACCUMULATOR
POWER RELAY
BOX ASSEMBLY
GUNNER’S SELECTOR
SWITCH BOX ASSEMBLY
SLIP RING
ELECTRICAL
CONTACT
HOLDER
ELECTRICAL
CONTROL
CIRCUIT
PUMP PRESSURE –
925 TO 1225 PSI
(6378–8446 kPa)
DRAIN RESERVOIR
PRESSURE, 0 PSI
(0 kPa)
OPERATING PRESSURE
900 PSI (6206 kPa)
SIGHT
GAGE
ASSEMBLY
BYPASS
VALVE
ASSEMBLY
AND SOLENOID
HYDRAULIC MOTOR
GUNNER’S CONTROL
ASSEMBLY (LEFT)
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