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A lighting truss is a tubular frame made of steel or aluminum that is used for fastening and positioning lighting fixtures and related cables. Used primarily for stage performances, trade shows, and in night clubs, trusses can be suspended from portable lighting stands, permanently mounted to the building, or suspended by wire rigging. The metal used in the lighting truss varies with installation type. Fixed installations typically use steel for its durability and when weight is not an issue. Portable trusses for both small and large applications usually are made of aluminum alloy and have recommended weight capacities assigned by the manufacturer.
There are three main types of trusses, all consisting of parallel poles with welded cross-members for stability and strength. Trusses can be either standard or custom-cut lengths, and can be joined together to form longer lengths. An I-beam lighting truss is the simplest design, consisting of two poles. Triangular trusses use three poles in a triangular configuration, and box trusses use four poles in a square configuration. The type of truss used typically depends on the number of fixtures and the method of installation.
Special arc-shaped trusses are used for specialty lighting design applications and usually are available in I-beam, triangular, and box constructions. Arc-shaped lighting trusses are also modular and of fixed or custom-cut lengths. They may be joined together to form circles, arches, and other radius shapes.
Aside from convenient and safe mounting of lighting fixtures and wiring, the modular design of a lighting truss allows portability and ease of set-up for traveling and storage. Lighting fixtures and wiring are normally not removed from the truss during a move, which can considerably reduce set-up and break-down times. Large or complex lighting truss assemblies can use a number or code for each section, thereby allowing the lighting technician to replicate the original design.
In large music concert settings, motorized trusses are often used. Suspended by wire-rigging attached to the venue ceiling, a series of motors and pulleys connected to the rigging allow the lighting technician to raise and lower the entire truss assembly for set-up and break-down. Some motorized lighting truss systems allow the assembly to move during the show, resulting in special lighting effects.
Compact trusses are typically used for individual trade show booths and by traveling disc-jockeys and small music groups. Using the same types of truss construction but in smaller pole diameters and section lengths, the lighting truss is suspended on top of adjustable floor stands. These highly portable truss systems allow all the advantages of larger systems but suit the needs of smaller venues.