Theatre Design & Technology - Feb 1967 - 23

Synchros are capable of transmitting a torque of several
cmp per degree. This is sufficient for transmitting the information necessary to move a pointer. For special tasks
such as motorizing regulator mechanisms the receiver is
connected to an amplifier which controls a servomotor.
Indicators with a frontal scale are used for normal installations into panel boards or as single units for wall installation. The most common panel forms are the clock-type and
the linear scale. Straight-scale indicators are especially suited
for illustrating the movement of a large piece of stage
machinery whose movement is linear: a vertical scale for
drops, a horizontal scale for wagon stages, etc. In many
cases it is necessary to be able to regulate the movement
of a piece of stage machinery down to the inch; for this
purpose it is possible to equip the indicator with fine definition. The standard form for data-transmitters is a waterproof Alpax housing fitted with the proper fastening flange.
(See Illustration 2.l

Illustration 3 shows a mechanical elevation scale for a
scenery set which is driven by an auxiliary cable connected
to a reverse shaft butt in the flies and indicates the elevation of the pipe batten. On two side-mounted leader rods
there are two contact assemblies with a preliminary and a
main contact each. The contacts are set by hand for the
proper elevation. On test runs the scales can be adjusted
using a milled set screw so that for a total elevation of
approximately 90 feet it is possible to reach a given elevation accurate within + - .4 inches. This degree of accuracy
is absolutely necessary when hung scenery is supposed to
reach stage level without making a sound. During the performance the pipe can be set into motion via remote
control. A preliminary contact in the switching mechanism
sets the drop into slow motion and then it moves slowly
toward the switch-off position (main contact). If for practical
reasons it is impossible to couple the linear scale directly
to the fly lines, it is still possible to hook up an electric
wave transmitter via synchros situated anywhere in the theatre, at the stage manager's desk, for instance. The advanvantages of an automatic switch-off mechanism driven by
electrical contacts remain the same.

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Fig. 4: Five-way Indicator for Light Bridges

Fig. 2 and 3: Transmitter and Mechanical Indicator fora
Counterweighted Set of Lines

Telemeters for Overhead Machinery. It is necessary to
be able to lift sets of Iines to an .exact height, especially
during the performance, in order to achieve a particularly
dramatic lighting effect. The stagehand responsible for raising the back drop has the task of reaching this trim with
as much accuracy as possible. For this purpose telemeters
as well as mechanical indicators without synchros can be a
great aid. It makes no difference whether the sets are
driven electrically, hydraulically or manually; it is completely
irrelevant to the installation of telemeters.

FEBRUARY 1967

Lighting bridges and drop battens are normally machinedriven. Here it is also normal operating procedure to install
the straight-scale indicator vertically: analogous to the movement of the particular piece of machinery. Illustration 4
shows a picture of a five-way indicator for light bridges
and pipe battens. On this scale the values are adjusted
so that stage level is located at the same point on each
scale.
Scene, act and show curtains rigged to draw, present a
much more difficult problem when the attempt is made to
illustrate their actual movement on an indicator. A simple
clock-type or linear-type scale is insufficient for the purpose
as such scales can neither illustrate the actual movement of
the curtain nor its overlapping. For this reason another solution has become popular. The scale is composed of a wide
horizontal slit in front of a horizontally-mounted cylinder
painted with three different colors. The painted conical
markings on the cylinder provide an amazingly accurate description of the actual movement of the curtain when the
cylinder is in motion. An additional linear scale above the
slit provides for accurate placing of the curtain when it is
to be only partially opened or closed. (Illustration 5).

Table of Contents for the Digital Edition of Theatre Design & Technology - Feb 1967