Apogee APL-220, Руководство пользователя

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(6) Flying the APL-220, -500, and -800
For many applications, the APL-220, -500, or -800 may need to be flown. This
requirement commonly occurs in television work, political conventions, the-
atrical productions, rock concerts, permanent installations, and numerous
other applications. Flying an APL-220, -500, or -800 or an array of them offers
many advantages – the downward angle can easily be adjusted, the horizon-
tal rotation may be easily adjustable (depending on the hanging method), and
the height can usually be optimized for best coverage with minimal bleed
onto the stage.
APL-220, -500, and -800 speakers perform perfectly well when flown; in fact,
they have been factory optimized for a free field environment and often
sound better when in the air as opposed to on the ground. Some loss of bass
response will occur, however, when any speaker is suspended in space as
opposed to being located near a wall, floor, ceiling, or other boundary sur-
face(s).
The APL-220, -500, and -800 are equipped with four rigging points – two on
the top and two on the bottom. These points are supplied with either Apogee
nutplates or Aeroquip pan-fittings, as specified at purchase (types of fittings
can be changed easily in the field to accommodate varying requirements).
If the rigging fittings are to be changed, always use the screws that are sup-
plied from the factory – never use generic screws purchased at a hardware
store, they are unsafe for this application!
Nutplates are circular steel plates with a welded 3/8-
1
6 threaded fastener in
the center, designed to accept 3/8-
1
6 threaded bolts (also available in Metric
M- 1 0 version). Each nutplate can sustain a straight-line-of-force load of 2500
lb. before failure. An APL-500 weighs 80 lb., so if only two nutplates are used
to suspend the speaker, the safety factor will be 62:
1 (NOTE: OSHA requires
a 5:
1
safety factor, whereas most theatrical rigging shops have voluntarily
adopted a 7: 1 safety factor).
It is vitally important that all hardware used to suspend the APL-220, -500, or
-800 be of the highest grade materials and construction. All bolts must be
SAE Grade 7 or better. The American bolt-grade rating system is often
depicted by a number of linear hash marks on the head of the bolt – five
marks means Grade 7, six marks means Grade 8.
If eyebolts are used, they must be forged and of the shoulder-type. Eyebolts
are designed for a straight-line-of-force. They de-rate rapidly and become
unsafe as the load angle deviates from the 0 degree axis (in line with the
length of the threaded bolt).
All bolts must be tightened securely, but not over-tightened (5-7 ft. lb. of
torque is generally sufficient for 3/8" bolts). Over-tightening can cause much
of the tensile strength of the bolt to be used before any external load is
placed on it. An exception to this rule is when the bolt is used in sheer, such
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