Theatre Design & Technology - Fall 1981 - 9

screw jack-driven platforms which would rise to accommodate
the then-active San Francisco Chorus. These platforms, along
with some upstage platforms called bridges, were both in front of
and behind the proscenium line. The screw jacks, however, are
no longer reliable, and as they were not particularly designed for
operation during performance, they were also too noisy to
seriously consider for driving the Lear platforming. The resultant
plan, then, demanded a whole new lift system that could fit into
the floor slots of the Opera House and allow the Lear platforms
to retract to floor level while also raising at least eight feet above
floor level. (See Figs. 3, 4).
The actual deck of the Lear platform needed to be as thin as
possible because it would raise so high exposing its edge and
lower surface. Priest chose to use a honeycomb lamination.
This provided a finished bottom surface for the platform in the
raised position, allowing the platform to present a clean, thin
line, while also providing a great deal of span capability. The
platformed areas were then modularized in construction drawings so that the modules could be reused in subsequent
productions. The center platform was divided into six sections of
4' x 16' laminated modules. After construction these modules
were attached to the lift hardware and joined together. The
resulting size of each center platform was then 12' deep and 32'
wide.
Flipper platforms attached to the offstage right and offstage
left ends of the center platform consisted of three sections of
laminated modules joined together and hinged to the center
platforms with six large countersunk strap hinges. The offstage
ends of these attached flipper platforms formed the ramp up or
ramp down and rode on the stage floor when used as a down
ramp. When used as an up ramp, the ends of the flippers were
raised by a '14" airplane cable bridle attached to batten ends.
Regular pipe battens served as carries for these bridles.
Jack Bogan of Landry and Bogan in Palo Alto was contracted
to engineer the honeycomb platform to help certify that the loadcarrying capacity of the platform was sufficient for the tremendous dead load, live performer and live scenic load. Rather than
having two sheets of plywood butt joined end-to-end with an
internal lap seam, the platform was laminated. And as it was to
be a stock platform after the production, it needed an optimal
live load characteristic. Through a boat-building contact, long
scarf joining machinery was located. Boat builders regularly
scarf join marine plywood and were set up to supply joined
plywood faces. The scarfed and glued plywood sheeting was
shipped to Los Angeles for lamination by LAOECO, Inc. The
finished lamination had a %" A-A marine ply top surface bonded
to 2'12" honeycomb paper core and bottomed with '12" COX
plywood. Morad spray adhesive bonded the structural platform.
The honeycomb was simultaneously closed out with 1 '12" stock.
To finish the edge, and not leave exposed plywood edges, the
entire assembly was faced out with 1fe" pine.
Each of the individual platforms had a dead load of 3,240 Ibs.,
and was able to carry a live load of thirty performers plus the
scenery. The machinery to operate this laminated platform went
through a couple of stages of evolution. In the model fabricated
by Larry Klein, the platform deck is essentially lifted by cable.
This was also true of the subsequent version designed by Jack
Bogan. The cabling system is quite ingenious. Because of the
large size of the platform, six points of carry were used under the
deck. The lifting cable was attached to the bottom of the stage
floor of the theatre, passed through a sheave welded to the
bottom of each of the six deck legs, and then went back up to the
underside of the stage floor. Each leg was thus resting in a cable
sling with a two-to-one mechanical advantage. The cable for
each leg was then reversed back down to the floor of the
basement trap room and passed through a mule block to direct
the cables to a common multi-pulley collecting sheave attached
to the floor. All six of the lines attached to a movable loft block
which acted as a clew. The movable loft block clew was rigged
through a stationary loft block and to the drum of the winch using

USITI/Fall, 1981

Figure 6. Floor mounted pulley block acts as a clew for the six
lines collected from the platform legs. This clew is rigged with a
mechanical advantage for the driving winch.

two separate lengths of cable. In this way it was not only rigged
with a mechanical advantage, but doubly rigged so that the
whole platform's load would not ultimately rest on one line. The
drum was driven by a DC variable speed reversing gearmotor
supplied by Peter Albrecht Corporation. Each of the platform
decks was rigged in this same way so the floor of the basement
trap room was a cobweb of '14" steel airplane cables under a
network of steel square tubing (Fig. 6).
The legging of the platforms was 3"-square steel tubing which
traveled in V-grooved castor guides assembled near the stage
floor opening. The rigid steel frame was capped with small kneebraced wight collection pads for bolting to the platform deck. As
these post tops were also cross-connected, they also served to
hold the individual deck platforms together. The actual control
point for the platform's machinery was placed backstage near
the locking rail of the counterweight system. Control of the

Figure 7. V-groove rigid castors track on the 3"-square steel
legs and center the posts while allowing them to travel up and
down. Two V-groove castors are mounted opposite one flat
roller. The mounting assembly fits into the existing floor opening.

Theatre Design & Technology 7

Table of Contents for the Digital Edition of Theatre Design & Technology - Fall 1981