Air Floatation
From half a tonne to 5,000 tonnes - float it on a film of air!
History - AeroGo
In the 1950's, General Motors Corporation developed a Compliant Air Film
Bearing for materials handling use in industrial applications.
Air floatation had been used in the die-making industry for moving heavy
loads, but only where the two mating surfaces were machined smooth and
were almost perfectly parallel.
General
Motors developed a design which permitted one operating surface to be made
of flexible material which would conform to (or comply with) irregularities
in a second, unmachined surface. This development widened the potential
applications.
The results of General Motors' efforts have come to be known as "air bearings" although it is more correct to call them "compliant" air bearings (because the torus "complies" with variations in the operating surface).
General
Motors licensed the technology to others in the mid-1960's. The Boeing
Commercial Aircraft Company became an early user, employing "air bearings" in
the movement of sub-assemblies on the B-707 production line. Significant
operating limitations with the GM bearing became apparent which lead to
R & D efforts by Boeing to improve the design. These changes resulted in
a design so unique that Boeing sought, and was awarded, a separate letters
patent. The registered trade name "Aero-Caster" identifies the
AeroGo air bearing.
In 1967 two of the Boeing engineers involved in the R & D work were permitted to leave Boeing and form AeroGo, Inc. For many years, Boeing was AeroGo's largest share holder, owning stock provided as compensation for a paid-up license agreement. The ensuing years have seen the technology mature from a novelty to a practical method of rotating, aligning, transferring, locating or moving materials and products in tight quarters.
AeroGo has advanced the state of the art to utilise air, water and other
liquids as the fluid film medium.
In
the movement of very heavy loads (usually from 1,000 tonnes and up), the
cost of pumping water or liquids, is about 12% of the cost of compressing
air. The use of liquids has lead to the broader, more accurate term for
the technology: Compliant Fluid Film Technology.
Backgrounds in aerospace, aircraft, automotive, custom machinery and marine engineering, provide AeroGo's staff with a broad capability to relate to a variety of applications and requirements. AeroGo Inc has been operating in Seattle for 40 years and is Quality Accredited to ISO 9001, as well as being an approved supplier to NASA, Boeing, McDonnell Douglas and the United States military.
Air & Hydraulic Systems Pty Limited is a 100% Australian owned company and has been applying AeroGo as a solution to materials handling problems throughout Australia for almost 30 years. We are accredited to ISO 9001 and have been the Australian Distributor for AeroGo since 1979.
Aero-Caster Evolution
Compliant Fluid Film Technology
The technology was originally developed in the late 1950's by the General
Motors Corporation, which sought to advance the well known theory of the "air
bearing". For years heavy loads had been moved by forcing air between
two machined surfaces, primarily in the die-making industry. This method
of movement had two significant pre-requisites: both operating surfaces
required a very smooth finish and both had to be very flat.
Two
major goals of General Motors' product developmemt programme were:
- Develop a general purpose product on which a load could be placed, moved and then unloaded.
- Develop a product that could be utilised on surfaces like factory floors rather than on a machined surface.
The results
of General Motor's efforts have come to be known as "air bearings" although
it is more correct to call them "compliant" air bearings (because
the torus "complies" with variations in the operating surface).
AeroGo has advanced the state of the art to utilise air, water and other
liquids as the fluid film medium. In the movement of very heavy loads (usually
from 1,000 tonnes and up), the cost of pumping water or liquids, is about
12% of the cost of compressing air. The use of liquids has lead to the
broader, more accurate term for the technology: Compliant Fluid Film Technology.
The Aero-Caster Principle
An Aero-Caster (or air bearing) is something like a short stroke air cylinder. The compliant torus bag forms the cylinder wall.
When pressurised air is introduced, the flexible torus, once sealed against the operating surface, inflates and lifts the load.
This occurs when the air pressure multiplied by the effective lift area
equals the downward force of the load: (force = pressure x area, or F =
P x A). The lower surface of the torus will then lift off the operating
surface and a thin film of air will begin flowing around the entire lower
surface of the torus. At this point, the load is suspended on a film of
escaping air.
This air film virtually eliminates friction as long as the operating surface is smooth and non-porous. The Aero-Caster captures a "bubble" of compressed air within the compliant torus and allows just enough compressed air to escape to create the air film. So long as the bubble is continually re-supplied with compressed air, at or above the operating pressure, and at sufficient volume to replace the air that escapes, the load will "float" above the operating surface, virtually without friction. Omni-directional movement (with significantly lower forces, often manpower alone), will then be possible so long as the "bubble" is maintained.
Under ideal conditions, the friction factor may be reduced to as low as .001, this means, a 10 tonne load may require only 10 kg of force to move it.
Select The Aero-Caster
Like
legs on a stool, a minimum of three Aero-Casters are required for the support
of any load, and for most applications a minimum of four is preferred.
For both technical and economic reasons, it is normally better to supply the fewest number of larger size Aero-Casters to support a given load. For example, eight K15N Load Modules will support 12 tonnes at rated pressure, as will four K21N Load Modules.
The four K21N Load Modules require only half the number of lift points and air supply hoses, and cost about 30% less than eight K15N Load Modules.
Furthermore, it is usually best to consider the use of even larger Aero-Casters
than the rated capacity would indicate, and operate these at lower-than-rated
pressures. Larger Aero-Casters operating at low pressures best accommodate
surface irregularities because the lower the pressure, the more compliant
the torus.
In
other words, an Aero-Caster is softer and therefore better able to conform
to surface irregularities at lower pressures. Also, offset loading may
require one or more of the bearings to operate at higher pressures than
the others.
The choice of which size to use is determined by the physical dimensions of the load, anticipated future applications, and the desired (or required) operating pressure.
Air
Floatation