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 TM 9-8000
universal joints are necessary in the power shafts of this
design, because the swinging-arm pivot axis is out of line
with the power shaft. The pivot axis, however, does pass
through the inboard universal joint to minimize the
relative sliding motion of the splined coupling.
30-8.
MacPherson Struts.
The MacPherson
suspension system uses a tubular strut, which houses
the shock absorber mechanism and links the wheel and
body together (fig.
The strut usually is
surrounded by a coil spring attached to the top of the
strut, which is mounted to the body. The lower half of the
spring is mounted by a flange that is attached to the
bottom half of the strut, which is mounted to the spindle
or control arm.
There are also other types of
configurations in which the spring is mounted next to the
strut; this type makes replacement of the strut relatively
easy.
30-9.
Comparison.
The
development
of the
independent suspensions came about mostly to reduce
the unsprung mass, thereby improving the handling and
traction of high-speed road cars. However, the demand
for greater speed and mobility for military vehicles
warrants the use of independent suspension on such
vehicles. In addition to the improved performance
Figure 30-13. MacPherson Strut Suspension.
associated with reduced unsprung mass, the use of
independent suspensions increases the speed and
maintenance. The separate rigid members used to
mobility of the military vehicle by reducing front end
maintain wheel alinement require more careful design,
vibration (wheel shimmy and axle tramp), permitting the
expensive machining, and costlier bearings than the
use of softer suspension springs, providing more ground
simple solid axle, leaf-spring suspension. The pivot
clearance, and permitting more optimum wheel spacing.
bearings must be lubricated properly so that excessive
clearances will not cause vibrations and disturbances in
The disadvantages of independent suspensions for
the steering and suspension systems. The independent
military vehicles are primarily those of cost and
suspension is not as rugged as the solid axle type,
although continuing development of the independent
suspension for military vehicles may minimize these
disadvantages.
Section IV. HEAVY VEHICLE SUSPENSION
if the secondary spring is secured to the frame. From
30-10.
Springs.
Several configurations of spring
that point on, the two springs carry the load jointly and
suspension have been used for vehicles that carry widely
their load ratings are added. This allows the vehicle to
varying loads, to provide the necessary variable load
carry heavy loads without deflecting the mainsprings.
rate.
b. Another method of suspension that also provides
a. Auxiliary springs, often called secondary springs
a spring with variable load rating is shown in figure 30-
15. The spring is made with flat ends that bear against
mainspring to accomplish this purpose. When the load
curved bearing plates.
on the spring reaches a certain amount, the deflection of
the mainspring brings the free ends of the secondary
spring against bearing plates on the frame, or on the axle
TA233807
30-9
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