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TM 9-8000
The control valves are mounted directly on the air
position remains constant, and the control link- age shifts
cylinder, each valve controlling one side of the cylinder.
and shuts off the air supply to the air cylinder. When this
The air pressure delivered from the air line to the cylinder
happens, the air cylinder remains pressurized In that
is proportional to the force applied on the top of the valve
position and holds the steering linkage steady until the
piston plunger by the control rod. The valves are
steering wheel is turned again.
actuated by a rocker arm so that air Is delivered to one
side of the cylinder at a time. These valves are adjusted
b. Right and Left Turns. If the steering wheel is
so that the air can be exhausted from both sides of the
turned in one direction, the steering linkage shifts one
cylinder simultaneously, but air pressure can be
way and the control valves allow one side of the cylinder
delivered to only one side at a time (fig. 33-17)
to exhaust while pressurizing the opposite side. The
piston rod then extends or retracts, providing the power
33-15. Operation.
a. Neutral. In the neutral position the force on the
steering  wheel  is  removed,  the  steering  wheel
b. Four-Wheel Steering. All four wheels can be
33-16. Construction.
steered from the steering wheel by connecting the
steering linkage of these wheels to the pitman arm (fig.
a. Four-Wheel Drive. A construction in which all four
33-19). The rear wheels are connected together by
wheels of the vehicle drive, is used on many military
knuckle arms and a tie rod. Because the rear wheels
vehicles. A typical construction for a wheel that drives
must be turned in the opposite direction to the front
and steers is illustrated in figure 33-18. A universal joint
wheels to travel in the same arcs around the center of
is used at the end of the axle shaft so that the wheel will
rotation, the drag links to the front and rear wheel
be free to pivot at the end of the axle, as well as be
steering linkage cannot be connected directly to the
driven through the axle. The end of the axle housing
steering gear arm. The drag link to the front wheels must
encloses this universal joint and is provided with vertical
move forward while the drag link to the rear wheels
trunnion pins that act as a steering knuckle pivot. The
moves rearward, and vice versa. To accomplish this, an
wheels, mounted on steering knuckles attached to these
intermediate steering gear arm is pivoted on the frame
trunnion pivots, are free to turn around the pivots at the
side member near the middle of the vehicle. The drag
same time they are driven through universal joints on the
links are connected to opposite ends of this arm so that,
inner axle shaft. Steering knuckle arms are mounted on
as it Is turned by direct connection to the pinion arm (by
the steering knuckles so that the wheels can be turned
means of an intermediate drag link), the front and rear
around the trunnion steering pivots by the steering
drag  links  are  moved  in  opposite  directions.


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