Installation manual

Community S-Series - Operation and Installation Manual - Page 46
10. Support Points & General Practices
A vital part of planning the mounting or suspension system is to first determine the
strength of the building’s support points. Nothing should be assumed, even for the lightest
loads. A ten pound loudspeaker falling from ten feet can maim or kill just as readily as a
heavy loudspeaker array falling from thirty feet. The services of a registered structural or
professional engineer should be employed to determine if the materials and design of the
supporting structure are adequate to support the intended load, and how to best install
mounting brackets or derive suspension points.
Fabric Webbing, Slings, and Spansets
Fabric webbing, fabric slings, and polyester Spansets can be very useful to the rigger. They
are strong, lightweight, and do not have stray wires on their ends that can cut fingers like
wire rope slings. They’re particularly useful as a means of securing a personal safety
device such as a climbing harness, when working at elevation. That said, be cautious of
using them in permanent installations as they are far more prone to damage by fire than
their steel counterparts.
Fasteners
As a general rule, lag bolts driven into wooden beams should be avoided whenever
possible, as they can pull out as the wood ages or swells due to changes in temperature
and humidity. Safe riggers will instead utilize machine bolts of Grade 5 ratings or higher,
rated beam clamps, brackets fabricated and welded by certified welders, wire rope wrapped
around beams with cushioning materials, and so on.
Certain wooden beams, or trusses, made of many laminations (often called Glue Lams) are
intolerant of holes. These beams are commonly used in modern construction, particularly
in tilt-up concrete industrial buildings. Drilling a hole through such beams can set up
internal fractures, resulting in total failure of the beam. Alternatives to drilling include
fabricating steel brackets to surround the beam, or wrapping the beam with a steel sling
and fabric cushions, to derive a hang point.
Concrete expansion bolts, such as Hilti Kwik-bolts or equivalent, can provide an excellent
means of attaching moderate loads to concrete surfaces. However, as they rely on an
expanding wedge to obtain their strength, they must always be used in strict accordance
with the manufacturer’s instructions. Such instructions specify the diameter and depth of
the hole, the composition of the concrete, permissible spacing of the anchors, and the
torque of the bolts. As a general rule, they should only be used for sheer loads, not tension
loads.
11. Liability
When you install a loudspeaker that is mounted or suspended over people’s heads, it is
your responsibility and yours alone to insure that the installation is performed in a safe
manner. Never take the word of someone who tells you, “That beam is safe to drill into,”
or “This point can handle the load,” or “I’ll take responsibility if anything happens.” To
paraphrase Harry Donovan from his excellent book on safe rigging practices entitled
Entertainment Rigging
, ‘How is it going to sound to the jury at your manslaughter trial
when you use such statements by others as your defense?’
Never do anything you aren’t 100% sure is safe. If a manufactured product looks poorly
designed and built, it probably is poorly designed and built. If you aren’t absolutely sure
where the wire rope came from or how strong it is, don’t touch it. If the bolt looks too
flimsy to hold the load, it probably is too flimsy. Always use your best judgment, just as
you do when driving at high speeds in traffic. The life you save may be your own.