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In the past, a wide variety of direct and indirect shock absorbing
devices were used to control spring action of passenger cars. Today,
direct, double-acting hydraulic shock absorbers and shock absorber
struts have almost universal application.
The operating principle of direct-acting hydraulic shock absorbers is
in forcing fluid through restricting openings in the valves. This
restricted flow serves to slow down and control rapid movement in the
car springs as they react to road irregularities. Usually, fluid flow
through the pistons is controlled by spring-loaded valves. Hydraulic
shock absorber automatically adapt to the severity of the shock. If
the axle moves slowly, resistance to the flow of fluid will be light.
If the axle movement is rapid or violent, the resistance is stronger,
since more time is required to force fluid through the openings. By
these actions and reactions, the shock absorbers permit a soft ride
over small bumps and provide firm control over spring action for
cushioning large bumps. The double-acting units must be effective in
both directions because spring rebound can be almost as violent as
the original action that compressed the shock absorber.
In the 1930s, there was a school for chauffeurs of the Rolls Royce.
Since the car had a reputation to maintain for its smooth and quiet
ride, the students had to pass a special test. They were required to
drive a Phantom II model with a glass of water on the radiator
without spilling a drop!
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