Air caster

Animation of how an air caster operates. Blue represents compressed air, purple represents the air film (or cushion) that the device rides on.

An air caster (or air bearing) is a pneumatic lifting device used to move heavy loads on flat, non-porous surfaces. Its operation is similar to a hovercraft, as it uses a thin layer of air as a way to float a very small distance off the ground. Compressed air enters an airbag shaped like a torus, and when the bag is filled it creates an airtight seal with the ground, and forces more air into the centre of torus, eventually causing the air to flow over the bag and to raise the load above the ground.

The compressed air is forced under the airbag, pushing it and the load less than a millimetre off the ground.

Advantages

Because air casters are virtually friction-free, the force required to move them is very low, often around one to five lbs. per 1,000 lbs. of weight. Air casters are also omni-directional, meaning they move with equal ease in any direction.

Limitations

Air casters require a smooth, non-porous surface in order to maintain lift and operate properly. Cracks and other surface defects can interrupt the proper flow of air, causing the air cushion to dissipate and thus lose its ability to lift. This limits their application to fields like manufacturing, where such surfaces are abundant. Also necessary is connection to a system which provides compressed air, as well as a power supply.

Usually, a standard concrete warehouse or factory floors provide an adequate surface. Some large cracks and filling expansion joint repairs may be required. Overlay material can provide options for moving over rough surfaces. (Example: You can use an overlay material to move onto an area of broom finished concrete outside. The overlay material can be sheet metal or a heavy gauge plastic sheet material.)

History

The air caster was invented in the late 1960s at the General Motors Technical Center in Warren, Michigan. The original inspiration for the technology occurred at an auto show when a large sign fell off a wall then “floated” several yards across the show floor on a naturally occurring film of air. After much experimentation, the air caster was born.

One of the GM engineers, Dave Snoeyenbos, struck out on his own in 1968 to commercialize the new technology, which he had licensed from the automaker. The company he founded, Decatur, Illinois-based Airfloat, remains in operation today.

Applications

Air casters have been successfully deployed around the world in numerous industries. In 1978, McDonnell Aircraft used air bearing transporters to create a “floating” assembly line at its St. Louis, Missouri manufacturing facility for the F-15 fighter jet. The new technology allowed jets to be moved down the line without removing their assembly jacks and without the aid of a mechanical tugger, resulting in a savings of over 29 man-hours per aircraft.

In 1977, AEP Service Corporation used a specially designed air bearing platform to move 44-ton tube bundles of moisture separator re-heaters at the Cook Nuclear Plant in Bridgman, Michigan. Previously, the company had used a complicated rail system involving a network of steel plates, I-beams and transporter cars.

Aloha Stadium in Honolulu, Hawaii, uses air film technology to reconfigure its four grandstands for different sporting events. Each grandstand weighs approximately 3.5 million pounds and rotates up to 200 feet through a 40-degree arc. They are moved by air bearing transporters located under the stands, which travel on concrete runways. Each grandstand stand is designed to be moved in only 20 minutes.

At the GE Transportation plant in Erie, Pennsylvania, air bearing technology is used to "float" 200-ton diesel locomotives from one assembly station to another. Workers at the plant euphemistically refer to the assembly line as the "world's largest air hockey table." Thanks in part to more efficient movement and positioning of the locomotives, the company says it reduced build time by 16%.