Theatre Design & Technology - Summer 1977 - 32

high strength type bolt is recommended. The %" diameter holes are offset from the slot centerline to provide "lands" to park the cam follower in either the
up or down position. It will be noted, furthermore,
.that this offset is not quite symmetrical. This is done
to provide a large bearing surface on the weight bearing
end of the cam follower travel. The only significant
problem concerns the loose fit between %" round stock
core and the actual inside diameter of %" N.P.S. schedule
40 pipe (approx ..820"). A substantial "off the shelf"
improvement would be offered by 1" 0.0. x .755" 1.0.
mechanical tubing. However, we were unable to obtain
this material in small quantities locally. A wQrkable alternative has proved to be to reduce the effective inside diameter near the top and bottom of the sleeve by crimping.
This is a technique we use routinely to improve the fit
when sleeving various sizes of thinwall tubing and involves
using what amounts to be a very dull blade in an ordinary
pipecutter. Precise control of the inside diameter is impossible but a considerable improvement in fit closeness can
be achieved. 3
It is best to exclude threads of the cam follower from
the shear plane so a bolt with an unthreaded portion is
advisable. Furthermore, by running the bolt up to its
unthreaded portion it can be locked into the core. The
threaded end of the bolt should be cut off so as not to
protrude through the core. 4
Several schemes have been used to operate this jack.
The simplest is to use the cam follower bolt itself with
typical lengths ranging from about 4" to 6". Another
scheme that has found widespread application especially
where it is necessary to fasten the jack on the inside
rather than the outside of a wagon frame is to weld a
%" bolt size hex nut to the top end of the core. In this
way the jack can be operated through a suitable access
hole in the lid of the wagon with a socket wrench. Though
there is theoretically no limit to the depth of platform
through which one could operate these jacks by utilizing
wrench extensions, any installation over a few inches
deep should include a pilot tube to help the operator find
the nut end. Alternately, of course, one can simply extend
the core shaft up to just below the lid.
Another variation proved very serviceable for a series
of wagons that were moved a-vista. All sides of the wagon
were seen from a fairly close distance thus making external mounting undesirable. The solution involved operating
the jacks with long built-in extension handles (Figure 151.
The handles consisted of 3/16" x 1%" x 18" flat stock
welded to lengths of %" N.P.S. pipe. The pipe was long
enough to overlap the top end of the jack shaft by approximately 4". By slitting the bottom of the pipe on
one side approximately 3%" x 7/32" and pinning this
slot to the jack shaft with a short 3/8" bolt, a telescoping coupling was achieved. This arrangement permitted
the handle to be raised approximately 2" rotated 1800
and then placed back flush with the platform lid. The
lids were padded so the handles were self-recessing.
Clearly the possible variations on these techniques
for wagon stabilization are considerable. Special applications and heavy loads will require modification of
32

SUMMER,1977

these designs.
NOTES
1
2

3
4

Crawford, John C., "Theatrical Uses of Air Flotation Systems", Theatre Design & Technologv, May 1970.
Drilling a piece of 3/8" x 3*" threaded rod is not advisable
because of the thin walls remaining between the 5/32" diameter hole and the thread root.
Obviously if space permits it is also possible to improve radial
stability by increasing the length of both core and sleeve.
Though repeated operation will eventually tend to flatten
the lower cam node, experience has shown that friction is
quite sufficient to keep the cam from rotating.
_

Editorial

Continued from Page 8

U.S. Institute for Theatre Technology
Founders Award 1977
presented to
DONALD H. SWINNEY
in recognition of
his Valuable Leadership Services
to USITT
whose dedication as
worker, committee chairman, officer, president
has been vital
in the development of the Institute
from its very beginning
USITT Board of Directors
Washington, D.C.
March - 1977
U.S. Institute for Theatre Technology
USITT Award 1977
presented to
ZELDA FICHANDLER
in recognition of
her Outstanding Contributions as
co-founder, producer, director
of the Arena Stage
Washington, D.C.
and her achievement in
the success and influence
of this
outstanding Theatre Institution
USITT Board of Directors
Washington, D.C.
March - 1977
U.S. Institute for Theatre Technology
USITT Award 1977
presented to
CYRIL MANTON HARRIS
in recognition of
his outstanding contributions
as author, educator, physicist, and acoustical engineer
in Acoustical Design
for performing arts facilities
in America
USITT Board of Directors
Washington, D.C.
March - 1977
U.S. Institute for Theatre Technology
USITT Award 1977

THEATRE DESIGN AND TECHNOLOGY

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