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:

Don't Get Carried-Away - Grab This

While touring the Mesa Arizona Arts Center (which is a fantastic set of four venues:  www.mesaartscenter.com) the Technical Director, Robby Elliot, showed me a simple rig that they use to prevent unexpected run-aways in the fly system.  Robby explained that due to the short time constraints imposed during some show strike operations, sometimes the stage crew gets ahead of the fly crew when unloading the battens.  This leaves the counterweight arbors heavy and prone to accidents while the weight loading crew plays catch-up.

To make the system safer, they install a Ultra-Safe rope grab (www.ultrasafeusa.com/pdfs/US-5000%20manual.pdf) on the hauling lines and anchor it to the locking rail with a SpanSet type roundsling (www.spanset-usa.com/lifting-steeltex.cfm) and an Omega Pacific HMS Jake 3-Stage Lock-action Carabiner (www.omegapac.com/itemdetail.php?id=59&secid=25).  They chose the Ultra-Safe US-5000 rope grab because it is designed to fit over the hauling line ropes (it will fit up to 3/4" diameter ropes).

When a rope lock is released (or slips!) the rope grab will hold the line until the line set is restored to a balanced condition.  Flexible, easy to move around, and simple to train the users on.

Arbor Day is Time to Check Your Arbors

Your Counterweight Arbors are stressed-out.  Make them feel better by giving them a thorough check-up.  Doctor's Orders.

Things to check:

Top Plate Connections:

• Make sure that all the screws, nuts, and bolts, are tight.
• Check the Hauling Line rope to see that is secure and not worn.
• Check the Lift Line Terminations to see that they are all secure.

Not Good Example . . .

 Check to see that Spreader Plates are accessible and Weight Locking Rings are in-use.

Not buried like this . . .

Check to see that the rods nuts are tight:

Tight nuts are good to keep your rod in place.

And check to see of the lower rope connection is properly tied-off:

Note the thimble to keep the rope from abrading on the lower arbor eye.

Keep a good eye on your arbors and watch for loose parts!  If something gives-way it could be deadly!

Every Day is Arbor Day in the Theatre

Lineset Numbering - It's not just for the index strip!

Here are some good examples of rigging management. Not only are the index strips and arbors CLEARLY numbered, but the batten end, loft blocks, and head blocks are also marked.

This also makes it easy to keep lineset inspection records straight during your annual safety check-up.

[Wire] Rope Terminations at Arbors

This picture shows a single purchase cast iron arbor top plate. The wire ropes are not supported by thimbles allowing them to deform and separate strands under load. Additionally, only one wire rope clip was used for termination, in lieu of the required minimum of two. Some of the "Crosby" clips (u-bolt cable clips) are installed backwards with the dead (unloaded) end of the cable run under the saddle (Remember: "Never saddle a dead horse").

The fiber hauling line does not have a thimble either, which acts to buffer the abrasive casting finish against the rope surface. Here is a picture of an arbor bottom plate with a plastic rope thimble (they are also available as a metal type):

This is a very old wire guided arbor with extended eye bolts for attachments (again, no thimbles to reduce the point-load on the rope bending point). You can also see that the top plate is tilted showing that the arbor has been racked and is skewed diagonally.

Here is the top of a double-width arbor (carries two stacks of weight). Again, no thimbles. It appears that the installer tied a clove hitch and then terminated the cable with just one wire rope clip. I don't know where the loose nut (partially hidden) that was laying on top of the arbor top plate came from . . .

And here is a the top of a new arbor that is properly terminated. Note that the load lines can be disconnected without cutting the cable. This makes them much easier to work on and replace if necessary. You can also see how the wire rope cables are not deformed as they bend around the thimble. Also of note is the safety wire (mousing) on the screw-pin shackle to keep it from coming apart. It's unknown why the front-most line was attached with a shackle when the other lines were looped around a through-bolt.