Air Spring

A simple mass on an air spring.
The spring constant of the confined air is:
where
γ = adiabatic gas constant
pa = atmospheric pressure [Nm-2]
S = cross-sectional area of air column [m2]
L = length of air column [m]

The natural frequency is:
where
f0 = natural frequency [Hz]
m = mass [kg]
Advantages:
  1. A readily attained low system natural frequency for a soft ride and lower shock inputs.
  2. Almost constant system natural frequency throughout the normal vehicle load range, thus maintaining good ride and lower shock inputs.
  3. Permits a low system natural frequency for normal road surfaces and improved shock control for the extreme cases.

Concepts:
  1. The most basic principle utilized is that air is compressible and when compressed, it exerts a force on the structure confining it and that the force exerted is proportional to the pressure.
  2. Changes in volume of a constant mass of confined air under pressure result in appropriate changes in pressure. P1V1=P2V2 This creates a non-linear spring rate and a nearly constant system frequency in the pressure ranges normally used.
  3. The ability of the air spring to support a given mass is governed by the effective area and the confined gas pressure.
  4. The energy storage capacity of air is far greater per unit weight than that of mechanical spring materials (steel or rubber).

See also: Air, Spring Constant.

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Subjects: Mechanical Engineering Physics