TM 5-3895-359-14&P
CRANKSHAFT VIBRATION DAMPER
The 4-71 engine uses a viscous type vibration damper
to reduce the crankshaft stresses to a safe value.
The viscous (fluid) type damper is employed where the
equipment which the engine powers requires frequent
speed and load changes. The viscous damper provides
faster' response to load and speed changes and high
temperatures have a less adverse effect than on the
rubber type damper.
The viscous damper assembly consists of a sealed
outer shell. an internal flywheel and a quantity of highly
viscous fluid (Fig. 1). The small clearance between the
flywheel and the outer shell is filled with the fluid which
causes the flywheel to be driven upon acceleration and
permits it to "freewheel" upon deceleration.
During operation. the outer shell. which is firmly
attached to the crankshaft, turns at the same speed as
the crankshaft, its motion being transferred to the
flywheel through the fluid within the shell. Inasmuch as
Fig. 1. Removing Vibration Damper Assembly
"fluid-drive" is more or less inefficient with frequent
(Viscous Type)
speed changes. considerable slippage of the flywheel
will take place as the power impulses are
transmitted through the crankshaft. In this type of
operation.
the slippage is desirable since the
acceleration and deceleration of the flywheel in the
damper lessens the amplitude of the vibrations, thereby
reducing their effects to a point where they are not
harmful to the engine.
The vibration damper must be removed whenever the
crankshaft, crankshaft front cover or crankshaft front oil
seal is removed or replaced.
Remove Vibration Damper From Crankshaft
1. Remove drive line adapter plate by removing the five
capscrews from crankshaft pulley.
2. Remove the crankshaft pulley retaining bolt and
washer.
3. Remove the crankshaft pulley.
4. Reinstall the pulley crankshaft bolt and install a puller
wedged between the crankshaft and the damper hub.
Fig. 2. Loosening Vibration Damper Outer Cone
After loosening the cone. it may be "fished" from the
inner diameter of the damper hub with two thin shank
screw drivers.
10-2-66
