Tuesday, June 9, 2009

It should be well hung when its wall hung.

Not everything gets rigged from above. Sometimes it is necessary to hang a cantelever load off a wall. This speaker weighs about 125 pounds and is supported from below by a steel bracket bolted to the wall, and the top is tied-back with an interesting mix of hardware.
This is a close-up of the top rigging. I could not see how the link chain was terminated to the top of the speaker. There is link chain (not rated for overhead lifting), connected to an aluminum turnbuckle (not moused, not rated for overhead lifting) via an open-ended hook at one end and an open eye bolt at the other; connected to a forged turnbuckle eye; via a stainless steel screw-pin shackle (unknown rating, but clearly not marked) that is not safety-wired (moused). The forged turnbuckle eye that was used to go through the wall should have been a sholder eye bolt with a large diameter hardened flat washer -- you can see how the base of the eye in pulled into the CMU block, possibly cracking it due the wedging forces.
When we go around to the back-side of the wall we find that the installer drilled through from the front and spalled the CMU block, then installed a mild steel flat washer and no lock-washer.
This speaker, and it brother on the opposite side of the stage, were mounted right above the walking paths of all those that came onto the stage. Also of note, although not a safety issue, was that this speaker was pointed straight-out from the wall toward a point about eight feet above the last row of seats -- whatever happened to the idea of aiming a speaker at the people? Obviously installed by someone that did not understand rigging or acoustics!

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