Arbor Day - The Last Friday Before May!

Annual  -- To do something EVERY year.  Rigging Inspections should come to mind, and although 'Arbor Day' is intended to be the day we all plant a tree, or three, it should also be a reminder that the counterweight carriages (aka: 'Arbors') in our stage rigging need love, too.

We want to look over your equipment and make sure that everything is in proper order.

• Nuts are tight.  The top and bottom rod nuts should both be checked to ensure that they are properly clamping the top and bottom arbor frames.
• The rods and back-bone are straight.
• Each cable and rope is properly secured.
• The guide shoes are clean and properly fitted to the guide rails.
• Spreader plates are spaced-along the length of the weight stack and not buried at the bottom.
• Weight locks are present, and have screws in them to allow them to be tightened-down so they can hold the counterweights from jumping out of the arbor frame in the event of a run-away and crash.
• Take the time to enumerate the arbors so they are easily identifiable regardless of what level they are positioned.
• Check to see if anyone has maybe added extraneous weights to the system . . .
There are many more things to check as a part of the rigging system, so this wasn't a complete list.

Remember: People are the most dangerous things in the theatre, so make sure that each person using the rigging system understands how to handle the weights, are secure so they can't fall over the weight loading railing, and they fully understand about using spreader plates, rope locks, and weight locking collars.  Using the tools you have properly can save lives!

KEEP THOSE ARBORS BALANCED (also referred to as: "In weight").  Train your crews to pace their work so that the fly crew (loading bridge crew) can keep-up with the ground crew that may be loading or striping a batten.  Out of balance systems can lead to run-aways, and that can really rack-up a system:

Another one's down. Another one bites the dust.

March 5, 2012 - Reggio Calabaria, Italy.  One stage hand was killed and two other injured as a space frame style stage truss structure collapsed and fell forward into the stage right side tiers of audience seating.  Fortunately, the incident occurred during the initial set-up of the equipment and there were no audience members present.

Photo courtesy of Life In Italy

The incident happened about 2:00 AM preceding the planned show the following evening.  Witnesses say one side of the stage structure slipped and collapsed sending the overhead trusses filed with lighting equipment onto Matteo Armelini, age 32.  He was killed instantly under the weight of the equipment.

Experts will now have to decide whether the collapse was caused by the failure of the Palacalafiore Sports Center’s parquet flooring to bear the weight, by poor structure design, or by human error during the erection of the structure.  The evening’s concert was cancelled.  The Reggio Calabria public prosecutor’s office has opened an inquiry and placed the entire structure under judicial seizure. Firefighters who provided assistance at the scene are seeking to establish the dynamics and causes of the incident.  Forensic police scientists have also been called in.

The stage for the Laura Pausini concert was the middle sized unit of three different stages used by the Faenza-born singer.  The stage set-up required fifteen articulated trucks to transport all the equipment.



 
At 1:00 you can clearly see the broken sport court flooring that could have possibly initiated the collapse.

This fatality comes just three months after a 20-year-old man was killed preparing the stage for a show by Italian rock star Jovanotti in Trieste.  (http://theatresafetyblog.blogspot.com/2011/12/stage-truss-collapse-in-italy-kills-one.html).

Looking at these pictures and correlating them to images of other similar truss collapses shows that they almost never fall straight down, but instead topple to one side as the corner joints give-way.  More attention needs to be placed on diagonal bracing to help prevent this type of failure mode.

For those of you rigging these types of structures:  it's time to review the proper assembly instructions with the manufacturers and make sure that all the parts are being installed properly.  Checking load limits (not guessing - actually calculating real loads) and checking the structure components for signs of stress, like kinks, cracks, and metal fractures should be done for each and every build.

Those aren't all they're cracked-up to be.

Modern rope locks are made from formed & welded steel plates. Older ones were made with cast metal and are more prone to stress cracks, and ultimately failure. Another good reason to do an annual inspection! Never load you rope locks to more than the recommended 50 pounds - keep your sets balanced and 'in-weight'. The rope lock may be stronger, but do you really want to find-out? This is also why you don't want to use your rope locks for rope brakes -- a dynamic load like a moving set and/or counterweight carraige can place much more strain on a rope lock than you would ever imagine.