Description – A pendulum system refers to a flying system with points attached to the facility in a fixed location, and all flights center on that location. Once the points are installed, they cannot move. Although these systems may seem quite simple and restrictive, they allow for creative choreography when placed in the correct proximity to one another and at the best location in the facility.
Operation – A pendulum system can have more than one lift point, but the “simple pendulum” is the most common type. A simple pendulum system has one lift point and, traditionally, one flying wire. The spot directly under the lifting point is called the “home position.” An artist standing on their home position will fly straight up when lifted by the simple pendulum system. For pendulum flights that allow the artist to cover distance during the flight, imagine a clock face surrounding the artist on the stage floor, with rings radiating out from them like a bull’s-eye. If an artist is standing on the 5 ring at 3 o’clock when lifted, the artist will swing to a spot that lines up with the 5 ring at 9 o’clock. As long as the artist is standing still when lifted, the artist will pass directly over the home position and be able to land at the spot directly opposite of the original location.
Clearance – A simple pendulum system requires a cone of clear air space that begins with a large circle on the stage floor and ends with the fixed pendulum point over the stage. The typical size of the circle at the base is about half the height of the fixed pendulum point. If the fixed point is 40 feet over the stage, the maximum diameter of the circle will be about 20 feet, and that establishes the size of the cone of clear air space. If an electric is trimmed at 20 feet, it must be at least 5 horizontal feet away from the pendulum point (which is a radius of a circle drawn across the cone at 20 feet high). If that electric can trim at a higher location (say 30 feet), it can be closer to the pendulum point (2.5 horizontal feet). The same applies to scenery, borders and battens that are used to fly legs.
Clearance Solutions – There are several solutions to the challenge presented by pendulum clearance requirements. 1) Move the offending unit out of the way for the flight. An electric can be flown out 10-15 feet for an upstage-to-downstage flight and then flown back in after the flight. 2) Use tail-downs. Typically, the pendulum flights will take place on or around the center of the stage. If legs or electrics are needed at that location, simply fly two shorter battens (under the house batten) that are outside the cone of clear air space for the pendulum systems. 3) Limit upstage-to-downstage flights. If scenery, battens, lighting or sound equipment is too close to the pendulum system, we can simply mark the stage with limits and advise the artists not to go outside those marks while they are flying on the system.