Configuring a stadium or other large venue to accommodate huge crowds can be a challenge. That was the case with Chicago Scenic Studios, Inc. (CSSI), a provider of scenic theatrical systems, when it faced transforming the Boston Fleet Center into a convention hall for the Democratic National Convention. One of the engineering hurdles was developing an automated system of raising and lowering three main podiums, slip stages, and monitor walls.
The biggest technical challenge was vertically lifting and retracting two transparent, 300-lb podium backing acrylic walls, each of which contained a series of flat-panel video monitors within the top portion of the walls so they could be hoisted away from the set with rigging.
Nook’s engineered screw jack solution met CSSI’s tight deadline and budgetary demands by using ActionJack screw jacks. Nook provided specially configured ball screws with a custom length and diameter for moving the podium backing monitor walls.
CSSI contacted motion control systems and components manufacturer Nook Industries to develop custom 50-mm ball screws that could lift loads upwards of 1,000-lb quickly, quietly, and within an 8-in. footprint. Nook recommended its two-ton ActionJack ball screw jacks to efficiently lift the walls over a travel length of 8-ft and dampen vibration and resonance while sustaining a 6-in./sec lift speed. CSSI needed a means for cutting the height of the wall in half by lifting and retracting the lower portion inside the upper portion so the collapsed 8-ft wall could be removed from or brought onto the set.
The ActionJack product line was originally designed for the home direct-satellite market. Each model incorporates a rugged worm gear set arrangement that uses an alloy steel worm which drives a high strength bronze worm gear. The worm shaft is supported on anti-friction tapered roller bearings with external seals to prevent loss of lubrication.
Nook increased the diameter of the lead screws and used a steep pitch thread pattern to provide the speed that was required. Additionally, using an oversized 50-mm shaft ensured that the screw would not vibrate or resonate while turning. The specially reconfigured 50-mm ball screws were then mounted in the sides of the upper wall.
To drive the screw jacks, a 2 HP-AC electric motor raised the ball nut on the lower wall and lifted the wall completely. According to Mark Ewing, CSSI’s head of automation.