Theatre Design & Technology - May 1970 - 28

THEATRICAL USES OF AIR FLOTATION SYSTEMS
JOHN C. CRAWFORD

University of California
at Los Angeles

Did you ever have difficulty making wagons
track as accurately on stage as they did on
the floor plan?
Did you ever have the need to move several
wagons accurately, simultaneously with a
small crew? .. A turn table that wouldn't
turn?
Did you ever have to move a large wagon
with a heavy set and several people riding
on it, smoothly?
Did you ever try to make a swivel caster
turn a square corner?
Did you ever have difficulty mounting casters
on a unit when the required platform height
and structure dimensions did not fit the
size caster avai lable?
Cheer up! Perhaps you have simply overlooked the answer. An industrial product
largely overlooked by the theater is the
Compliant Air Bearing. It was originally developed by General Motors as an assembly
line aid and is used by Boeing to assemble
the 747. The Air Bearing 1 is the space age
answer to the swivel caster. It is omnidirectional, virtually frictionless and comes in
a variety of sizes; the smallest of which
will carry 1000 lbs. and is less than 1"
high and 12" wide, and sells for about
$20.50. The largest is 2" high and 44"
wide, it will lift 1 5,000 lbs. and sells for
about $151.00.

Despite this enormous weight capability, an
air bearing can lift 4 tons with an air flow
of 30 cubic feet per minute. Low pressure
blowers may also be used.
The smoother the floor, the more efficient
the device. Rough floors provide extra paths
for the air to escape. Large cracks or gaps
in the floor or a porous floor act the same
way. Covering these cracks or pores with
sheet plastic, masonite, sheet metal, masking tape, or a good coat of paint, will reduce this loss. The gap between a loading
dock and a box car or across a ship hatch
can be bridged the same way. Air bearings
have been used on asphalt though considerably more air is required to bolster the
lessened efficiency. Specific information
pertainiing to use on such problem surfaces
can be obtained from TASC. Moving from
a flat floor onto an inclined plane is not
usually practical.
On a recent production we used four 16"
air bearings to move a very large jackknife
wagon which carried a double-faced set, a
bar, two step units, many props (both fragile
and heavy) and 7 actors (in violent action).
The movement was effected by one stage
hand (wearing tennis shoes). NBC uses air
bearings to move its audience around on the
Andy Williams Show.
Since air bearings have a very low silhouette (a 12" bearing is 1 / 4" thick when

deflated), we are hoping to develop a system which will replace the casters on our
9' concert grand pianos. We also have plans
to install them under a 7000 lb. pipe organ
which gouges the floor each time it is
moved.
Dollies or pallets using air bearings are extremely low and easy to load-about 2 '/2'
high. They are available as self-contained
battery operated units; with recharger, with
air bottles, or for use with your house air
system.
Air bearings do not require turn-around space
as do units with standard swivel casters,
since they are omni-directional. Units using
air bearings will follow a track with great
accuracy.
There is relatively no friction and no appreciable increase in friction with ambient
increases in load. One pound of push is
needed to move each 1000 lbs. of load
(or load + 1000 = push necessary). As
long as the load is within the capacity of
the bearing, it will not damage a floor.
The ride provided is extremely smooth as
long as sufficient air is available. Air bearings will usually not jam or bump when
passing over small debris, such as nails,
screws, small wood chips, metal shavings,
etc. On the jackknife unit mentioned we inadvertently punctured the rubber envelope
with a nail, but the caster continued to
function.

The Air Bearing supports your load on a
frictionless film of air. Compressed air is
held in a donut-shaped envelope which conforms to the floor. Air escapes between
this envelope and the floor in a thin layer
(3/1000 of an inch) forming a frictionless
film between the load and the floor.
The area underneath the envelope is called
the footprint. Its air pressure is higher than
that outside the envelope, and the load is
pushed up when the bearing is actuated.
Typical footprint pressure is 10 Ibs. per
square inch, thus a 2 foot-diameter bearing
will lift 4000 Ibs. Four 2 foot-bearings will
carry a truck.

1. Now being manufactured by TASC (Transocean Air Systems Corporation (805) 964-3508,
P.O. 80x 30363, Santa 8arbara, California).

The TASC Structural Air Bearing shown above has a capacity
of 18,000 pounds. Sizes range from 1,000 to 30,000
pounds.

THEATER DESIGN AND TECHNOLOGY

MAY, 1970

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