The term «air cushion» is used to describe a space containing air under pressure, generally placed under a vehicle or an object to be moved, and communicating with the surroundings. Thus this air must be constantly renewed, either by a fan or by the movement of the vehicle. the first case is that of the hovercraft, the second that of vehicles operating in ground effect, WIG short for «wing in ground effect».
The usefulness of the air cushion stems from the fact that its separate the vehicle from the surface over which it operates, thus allowing free movement over surfaces with little or no bearing strength. This usefulness is paid for by the power needed to maintain the flow of pressurised air under the vehicle. This power depends on the pressure existing under the vehicle and on the flow of air escaping from the cushion. In order to reduce the escape area under the vehicle, flexible structures are interposed between the hard structure of the vehicle and the operating surface. These flexible structures, called skirts, have contributed to making hovercraft a practical proposition. Diverse skirt systems have been developed, each having its own stability characteristics.
Air cushions have also industrial applications, allowing movement of heavy loads. When this is possible, water can be substituted for air, reducing the required power by an order of magnitude. Extrapolating in this direction, the air cushion, becomes a fluid bearing, thus joining the multitude of anti-friction devices of mechanical engineering.
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on March 3, 1997 by MALINA
Conseil inc.
Last update on December 4, 1997.