Electro-Voice XLC manual Complex Structural-Rating Analysis

Figure 7 includes a graph of the working-load weight-versus-angle limit rating for the XLC enclo- sures. This working-load weight limit is applicable to every enclosure in an array, and includes the weight of that enclosure plus the total weight of all enclosures and rigging hardware suspended below it. The absolute enclosure angle is the vertical angle of that enclosure, where 0° represents an upright enclosure facing straight ahead (0° elevation angle). These working-Ioad-versus-angle limits take into account the complex forces generated in the front button bars, the rear swing arms, the quick-release pins, the rigging frames, the enclosures and the (optional) pull-up line, as a result of the complex weight distribution throughout the array.

Also included in the simplified structural-rating guidelines in Figure 7 are side-to-side and front-to- back angle limits for the front button bars and rear rigging arms on the top enclosure.

WHEN APPLYING THE SIMPLIFIED STRUCTURALRATING GUIDELINES TO ANY XLC LOUDSPEAKER SYSTEM SUSPENDED OVERHEAD, THE USER MUST OBEY THE FOLLOWING RULES:

1.Never exceed the working-Ioad-versus-angle limit for any enclosure in the array.

2.Never exceed the side-to-side angle limits for the front button bar assemblies on any enclosure.

3.Never exceed the side-to-side angle limits for the rear swing arm assemblies on any enclosure.

4.Always make sure that every front button bar is securely locked in the front rigging tube on every enclosure (and grid, when applicable) before lifting overhead.

5.Always make sure that every rear swing arm is securely locked in the rigging frame with the quick-release pins on every enclosure (and grid, when applicable) before lifting overhead.

6.If a pull-up grid is used, never exceed the side-to-side angle limits for the pull-up grid.

Discussion of Array Examples: For example, if the top enclosure in a column was angled down 30°, the enclosure working-Ioad-versus-angle limit from the simplified structural-rating guidelines shown in Figure 7 would indicate that a total of 1950 pounds (885 kg) could be safely suspended. This would include the weight of the top enclosure plus all of the enclosures and rigging sus- pended below.

If, however, the top enclosure in a column was angled up 30°, the total allowable weight would then only be 1863 lb (845 kg) - including the weight of the top enclosure plus all of the enclosures and rigging suspended below. The enclosure working-load-versus-angle limit shown in Figure not only applies to the top enclosure in an array column, but also applies to every enclosure in an array column. In arrays where a pull-up grid is not used, the top enclosure is always the limiting factor because it supports the most weight. However, in arrays where a pull-up grid is used to achieve substantial downward angles, it is possible that a lower enclosure could be the limiting factor.

3.4 Complex Structural-Rating Analysis

For a complete structural-rating analysis, the forces in each individual piece of attachment hard- ware throughout the XLC system must be determined, as well as the forces on each enclosure. Determining these forces requires complex mathematical calculations. All of these forces must then be compared to the working-load limits detailed below for each of the rigging points and the overall enclosures.

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