Theatre Design & Technology - May 1970 - 29

When the air bearings on a wagon unit are
deflated, the unit is as steady as the same
unit without any casters at all.
Platform units can usually be constructed
using fewer air bearings than would be the
case with standard casters. The placement
of air bearings is based primarily on the
maximum amount of span allowable without
sag and the maximum amount of cantilever
that can be counter-balanced. An air bearing
is so low and its lift capacity is so great
that it enables you to increase the beef of
structural members by more than double
that which is possible with standard swivel
casters.
If the weight of a person stepping on the
canilevered corner of a platform causes the
bearing at another point to be lifted off the
floor, place counter weights on the other
caster. Generally, it seems that the greater
the difference between the stable weight
and the ambient weight the less effect
the ambient weight will have on the unit
as a whole. To provide as much latitude as
possible in this regard it is often wise to
use a larger bearing than is necessary to
carry the estimated weight of the platform
and its expected ambient load. The difference in price between a 1000 lb. capacity
bearing and a 2000 lb. bearing is only

$7.90.
A similar situation arises if the platform is
not rigid enough. If you step on a platform
between bearings and the platform sags,
this may tilt the bearings up enough on the
outside to lose their lifting ability. Before
you rebuild the platform, however, try loosening the bolts that connect the air bearing to
the platform. If the point at which the
weight of the platform sits on the bearing
is centered on the bearing, the amount of
pivot thus achieved may solve the problem.
When designing the mounting arrangement
on a platform, it is often wise to anticipate this and make the bearing point as
narrow as possible and center it over the
bearing with the Iine of pivot at a right
angle to the area of expected sag.
The only sound produced by an air bearing
in operation is the sound made by the escaping air which is of considerably less magnitude than the sound of the air being let
out of your car's tires. It is possible to
eliminate some of this problem by putting
a sound deadening material on the underside
of the platform and on the back of the
facings. This, however, only eliminates the
resonance of the platform. Since the point
from which the sound originates is between
the bearing and the floor total, silence can
only be achieved when the platform is
masked in some manner.
Though the noise of operation is not very
loud, it is a factor to be reckoned with.
In any case, the sound produced is certainly
more acceptable than the drum-like rumble
of a standard caster. In fact, when you
hear it, you may like it so much you may
want to amplify it and write it into the
show.

ITITII:J THEATER DESIGN AND TECHNOLOGY

Joining airplane wings is one of the many uses for the Air
Bearing Caster Jack.

MAY, 1970

29



Table of Contents for the Digital Edition of Theatre Design & Technology - May 1970

Contents
Theatre Design & Technology - May 1970 - 1
Theatre Design & Technology - May 1970 - 2
Theatre Design & Technology - May 1970 - 3
Theatre Design & Technology - May 1970 - Contents
Theatre Design & Technology - May 1970 - 5
Theatre Design & Technology - May 1970 - 6
Theatre Design & Technology - May 1970 - 7
Theatre Design & Technology - May 1970 - 8
Theatre Design & Technology - May 1970 - 9
Theatre Design & Technology - May 1970 - 10
Theatre Design & Technology - May 1970 - 11
Theatre Design & Technology - May 1970 - 12
Theatre Design & Technology - May 1970 - 13
Theatre Design & Technology - May 1970 - 14
Theatre Design & Technology - May 1970 - 15
Theatre Design & Technology - May 1970 - 16
Theatre Design & Technology - May 1970 - 17
Theatre Design & Technology - May 1970 - 18
Theatre Design & Technology - May 1970 - 19
Theatre Design & Technology - May 1970 - 20
Theatre Design & Technology - May 1970 - 21
Theatre Design & Technology - May 1970 - 22
Theatre Design & Technology - May 1970 - 23
Theatre Design & Technology - May 1970 - 24
Theatre Design & Technology - May 1970 - 25
Theatre Design & Technology - May 1970 - 26
Theatre Design & Technology - May 1970 - 27
Theatre Design & Technology - May 1970 - 28
Theatre Design & Technology - May 1970 - 29
Theatre Design & Technology - May 1970 - 30
Theatre Design & Technology - May 1970 - 31
Theatre Design & Technology - May 1970 - 32
Theatre Design & Technology - May 1970 - 33
Theatre Design & Technology - May 1970 - 34
Theatre Design & Technology - May 1970 - 35
Theatre Design & Technology - May 1970 - 36
Theatre Design & Technology - May 1970 - 37
Theatre Design & Technology - May 1970 - 38
Theatre Design & Technology - May 1970 - 39
Theatre Design & Technology - May 1970 - 40
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