 Toggle clamps are Broadway
mainstay
Since 1981, air-powered,
hold-down-action, and straight-line plunger-action toggle clamps manufactured by De-Sta-Co
Industries, Birmingham, MI, have been an integral part of the power behind the performance
in a host of popular Broadway shows.
The clamps play important roles in stage machinery designed and built by Feller
Precision Inc, Tappan, NY, as a part of custom automated-motion systems used to precisely
move and position theatrical scenery structures.
In developing the automated systems, Feller Precision designers, engineers,
programmers, and fabricators work closely with the client's production team to transform
an original artistic vision into workable visual effects. Finished systems, built at a
fully equipped 26,000-sq-ft production facility, combine the company's Showtrak
computerized motion-control systems, AC and DC electrical winches, and hydraulic and
pneumatic devices.
A better clamping solution
According to Feller Precision's president, Peter Feller, the automation builder was the
first technical-support firm on Broadway to incorporate De-Sta-Co toggle clamps into its
machines and structures. The clamps have played a part in a host of major stage
productions.
"The shows are almost all musicals," Feller notes. "Musicals are the
kind of productions that have moving scenery and the budgets to make use of
automation."
De-Sta-Co clamps are used in these shows to add rigidity to moving scenery structures
that are inherently unstable. To keep stagehands out of the play action, all of the clamps
are pneumatically powered for remote actuation.
"We use only two clamp designs," Feller notes. "The hold-down-action and
straight-line plunger-action clamps are best suited to our needs, and we may use anywhere
from one to twelve clamps in a given application."
Before discovering the positive-locking toggle clamps in catalogs and technical
publications, the automation builder had been limited to clamping methods that were
serviceable, but primitive and limiting.
"In many cases, stagehands had to manually engage cane bolts into floor receivers,
bolt and unbolt important structural components, and make and break C-clamps," Feller
says. "We would also manually insert locating pins and chocks where practical, but
this couldn't be done when it interfered with cueing or sightlines."
The De-Sta-Co clamps offer important advantages over all these earlier methods,
according to Feller, including faster set-up and tear-down times, superior holding power,
and increased versatility and reliability.
A wide range of clamping roles
De-Sta-Co toggle clamps have played a variety of roles in the automated systems built
by Feller Precision.
In one scene of Cats, a huge, floating tire had to be moved from its storage
position on the floor near the back wall of the stage to an elevation of about 10 ft at
the front of the stage. To meet this requirement, the automation builder designed a system
in which a hydraulically-operated telescoping vertical post in the cellar below the stage
travels up and down on I-beam rails.
"The problem was that the telescoping post had to pass through a solid portion of
the stage," Feller points out. "To do that, we engineered a series of
pneumatically operated trap doors in the path of the tire. Under the cover of artificial
fog, the trap doors first drop away to allow the post to pass, then close up behind it in
a strictly coordinated sequence."
An additional challenge was to make sure that the trap doors were both rigid and safe
when they closed up flush with the stage floor. To provide this security, the system
builder placed a row of pneumatically powered hold-down-action toggle clamps along the
bottoms of the nonhinge side of the doors. This created a solid feel to the stage floor,
and also ensured the physical safety of the actors.
The toggle-locking design of the clamps used in this application provides more than a
ten-to-one ratio of holding force to the manual or power force needed for clamp actuation.
The toggle design also yields positive locking through an over-center toggle linkage
arrangement that secures the holding force indefinitely.
According to Feller, the over-center positive locking makes the clamping system so
secure that the trap doors could not be loosened even if the power air system actuating
the clamps should fail completely. Security is further enhanced by continuous real-time
inspection of the clamping system.
"The stagehand operating the show automation is in the cellar no more than five or
six feet from the clamps," Feller says. "The clamp system and the trap door
operating system are electronically interlocked to prevent illegal sequencing, and the
operator makes sure the interlock is working through visual verification every step of the
way."
A versatile tool
Feller notes that the role is rooted in the challenge to reconcile two competing
requirements in the use of theatrical scenery.
"Scenery structures must be free enough to be maneuvered backstage and delivered
to on-stage playing positions without obvious handling," he says. "At the same
time, they have to be rigid and stable enough to look realistic, provide reliable use, and
ensure the safety of the actors."
Because artistically designed scenery structures are typically not massive enough to be
stable, the De-Sta-Co clamps are used to provide added rigidity. At the same time, Feller
notes, the clamps can be applied strategically to hide their use from the viewing
audience.
"That makes them a very versatile tool for automation designers," Feller
adds. De-Sta-Co Industries, Birmingham, MI. e-mail: cust.serv@destaco.com
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