Arbor Day is Every Day in the Theatre

[Erich Friend]

Trees are great.  When on falls in the woods and no one is around – does it make a sound?  Who cares!  However, if a counterweight falls off of an arbor in your theatre – then it’s time to care.  Care A Lot!  You don’t want to be on the receiving end of that!

Each time I walk onto a stage one of the first things I check are the locking rings (or weight locks) on the counterweight arbors to see if the last person that handled them tightened the lock rings down properly.

Weight locks everywhere except where they are supposed to be.

9 times out of 10 they are loose, and 5 times out of 10 they are left in an elevated position so they don’t even touch the weights.  About 2 times in 10 they are missing the tightening screw / knob and can’t be secured.  About 1 time in 10 they are completely missing.  And occasionally they are present, but there never was a means to tighten them down (I guess the installer thought maybe they worked by gravity – let’s see . . . a 40 pound weight is held back by a 6 ounce weight – I think NOT!)

Weight Lock Ring simulated by a U-Bolt?  Note the other one wedged behind . . .

GOT FRICTION?  If the line set gets away from the fly operator and goes into a run-away condition, then the only thing holding the counterweights in-place are the weight lock rings.

Weight Locks - Don't fly without them.

Physics 101:  “An object in motion tends to stay in motion.”

This means that when the arbor crashes into the upper arbor stop or head beam, and the arbor stops suddenly, then the weights will try to keep in travelling upwards.  If the weights are not locked down, then the y can levitate right up off of the stack and fly loose from the arbor.  No. this isn’t anti-gravity at work, it’s inertia.

The last thing you want around your fly rail is a 20 pound chunk of steel randomly ricocheting off of your fly gallery structure, other arbors, and/or lift cables.  You simply can’t predict where it will go.  Except down.

Note the missing screws to secure the weight locks to the arbor rods.

Physics 102:  “An object falling will continue to accelerate downwards towards the earth under the force of gravity” until it:

a.)    Reaches terminal velocity due to air resistance (about 120 miles per hour), or

b.)    It hits something that causes it to stop moving (could be your head, or the floor – only the latter will be obvious to you, the former you won’t remember until you meet your maker).

Oops!  They installed the locking ring and never drilled and tapped a hole for the screw . . .

Physics 103:  “An object struck at high velocity by a heavy mass will typically be severely damaged or destroyed.”

Arbor Day – Lock ‘em down.  Every time.  No excuses.

And be green - go plant a tree, too!

[Erich Friend]

More info about Arbor Day here:

http://theatresafetyblog.blogspot.com/2011/04/arbor-day-is-time-to-...