Article by Josh Peklo
Josh Peklo is the Technical Director at the Guthrie Theater and an ETCP Certified Theater Rigger. Josh is adaptable, innovative and principled, and is a well-regarded leader and manager. Josh has taught several workshops for us, and I’ve enjoyed working with and getting to know him over the years. - Wu Chen Khoo
Control the Load
All rigging starts with one guiding principle, safely control the load without ignoring (but many times exploiting) gravity. Whether a simple static load or a complex dynamic load, a rigger’s job is simply to safely support or move an object without dropping it. In the theatre business, we typically have the added constraint of supporting the aesthetics of the designers and directors while safely controlling the load. One cannot exist without the other or we have failed. Accidents happen when a system becomes out of control; out of weight linesets, 1 person lifting a 2 person load, overloaded hardware to name a few. If we fly Peter Pan with a thick purple climbing rope we likely will not drop the actor but the magic will be lost; conversely, if we hang a scenic ceiling over an audience with undersized wire rope that fails and falls catastrophically the “invisible” attachment will not be remembered by any of the audience.
The following is not meant to be an ultimate all encompassing guide to any rigging you might encounter but more as a framework for a safe rigging mindset. Rigging for entertainment is a broad and complex topic that combines science, math, engineering, management and art.
Know your load-
Foremost you must determine the weight of the load that you are hanging. Get in the habit of calculating weight estimates of the items being rigged. If you are hanging a commercially made lighting instrument or speaker you can obtain the weight from the manufacturer. If you are hanging a piece of scenery estimate the weight using material weight values that you can look up. Some rules of thumb exist and these are fine to use, but strive for a thorough estimate rather than a guess. Paint and texture are often overlooked when estimating scenery weight but on large units this can become significant. A gallon of paint weighs about 10 lbs, and that weight remains when applied to scenery. Like paint, don’t forget about hardware and the actual weight of the rigging. If you have access to a scale, load cell, or dynamometer actually weighing the item is the most efficient method of determining the weight. For items like soft goods that are used repeatedly develop a list or chart or label the goods themselves so you know every time you hang them how much they weigh.
Evaluate the entire system-
Think of every rigging instance as a complete system. If we hang a single chandelier from the pipe grid in a black box theater from a single piece of wire rope a system still exists and every part of the system must support the load of the chandelier. After finding the weight of the chandelier and placing the chandelier in the space based on the designer’s specification, determine the attachment point at the top. Is there structure directly above the point capable of
supporting the weight? If there is only a ceiling, is there a way to securely attach into it or does the cable have to be redirected somehow to a more secure attachment point. Once the point is selected and deemed appropriate to the load, hardware needs to be selected to connect the point (upper attachment location) to the load (the chandelier). This could be as simple as a rope tied to the grid and the other end tied to the chandelier or a length of wire rope with end terminations and connecting hardware. If the latter, the wire rope and the connecting hardware must be sized or rated to hold the chandelier. Last the attachment point on the chandelier must be secure. If it is a commercially built chandelier, it should have an appropriate attachment point but it is not uncommon practice to reinforce or solidify this connection especially if the chandelier flies in a production. The chandelier purchased at the local home store is likely built to hang in a dining room from the ceiling but not likely engineered to move during a production. After evaluating all of the components in a system I like to determine what the weakest link is and reaffirm that the weak link is still capable of supporting the entire system. If not, the entire system needs to be redesigned.
Know your limits-
Many limiting factors exist in rigging but staying within them allows the rigger to control the loads
safely and effectively. Often in our business we are attaching elements to an existing house rigging system. The rigger must know the capacity of the system that is in use but also what that number reflects. A single purchase counterweight arbor that holds 1700 pounds cannot support 1700 pounds in infinite configurations. A question I ask in every rigging class is “What is the weak link in a typical counterweight lineset?” The answer is the batten. 1700 pounds evenly distributed, such as an electric with evenly spaced units and cable is likely no problem on an 1-½” schedule 40 pipe. Change the load to a scenic wall that has four attachment points spaced so that they attach at the system lift lines also likely not a problem. If the lift lines are 10 feet apart and our load attaches halfway between the lines the capacity of the 1700 pound lineset is limited by the strength of the batten between the lift lines: about 150lbs per point. Every rigging situation is different and the rigger must balance the limits and configuration of the system with the parameters of the load.
The other often overlooked limiting factor is the means or process to hang the actual load. If the system supports 1700lbs and a large scenic wall is designed to work within these limits do we have the crew or process to safely attach the wall and stand it up. Does the counterweight system having a loading rail, a mid-rail, access to a capstan winch or just crew members and brute strength? The rigging plan must be tailored to the resources at hand both equipment and personnel. The training and skill of the crew must also be evaluated as part of the plan. An experienced crew of four with access to a chain motor package could probably hang the 1700 pound wall more safely and efficiently than a crew of 20 inexperienced volunteers. Don’t overlook the fact that every static load has a dynamic state during the hanging or striking. The dead hung wall unit is most dangerous and prone to the most forces when it is being moved into place.
Invest in Hardware-
Shortcuts in rigging often start with the selection of the hardware. In the same way that a rigger must know the load or loads present, the rigger must also know and trust the capacities of the hardware used. Hardware selection is obviously a topic worthy of more than a paragraph but this should serve as an introduction to best practices in hardware selection. Hardware largely falls into two categories: rated and unrated. Manufacturers of unrated hardware do not specify and sort of load rating or capacity. The most recognizable piece of unrated theatrical hardware is a D-Ring. They have been used for decades to safely and effectively hang lightweight scenery but as a rigger you cannot definitively trust that is will support a specific load. Unrated hardware has its uses but the rigger is making a choice based on instinct or experience not science. As loads have become heavier, the industry has wisely chosen to rely on rated hardware. A rated piece of hardware will typically have a load rating stamped or engraved on it and more importantly the user can look up via the manufacturer the load rating, how it was calculated, how the piece of hardware is designed to be used according to the manufacturer, and how to inspect it. The manufacturers who build this hardware stand behind the hardware as long as it is used in accordance with their recommendations. This trust between user and manufacturer is necessary so that the rigger can trust their own work. As a rigger I want to be able to literally stand under a piece of scenery that weighs 1000 lbs knowing that every piece in the system will hold the 1000 pound weight. Part of trusting a rated piece of hardware goes beyond a stamp or engraving that says 500 pounds. Using a shackle that only contains a 500 pound stamp and a country of origin in my opinion is not a trustworthy piece of hardware. Use hardware from reputable manufacturers- if you can’t contact or identify the manufacturer you can’t verify any information about the piece of hardware.
Ask for help; Find training; Trust yourself.
If you don’t understand how a rigging system or a particular piece of hardware works ask for help. Come up with a total plan before having an out of balance load and a missing component. Make a scale mock-up to prove out an idea with ounces instead of tons. Find an expert, take a class, read a book, build up your experience however you can, watch how other industries rig. I can’t walk past a construction site without looking to see what the crane is doing. In the grand industry of rigging our loads are smaller but the principles and hardware (although scaled down) are the same. When a director or designer ask us to hang a speaker cluster in a specific spot they are trusting that we will do it safely and accurately and that the speakers will stay securely in their spot; our success reinforces this trust but I think more importantly the rigger must trust their own plan and choices. We did not get specifically into math and design factors in this article but a final factor of my own which requires no math I refer to as the “Sleep At Night Factor”- a rigger must be able to walk away from a project without doubts- this does not replace the empirical engineering side but it should not be ignored.