Load cells – rocking your world
This summer, thousands of people will flock to see US rock band The Killers perform live at the Isle of Wight festival, and on tour in the UK. And load cells will be right on stage alongside them, and many other acts, helping keep their stage sets safely rigged.
For those who have never stood under a massive rigged set, it’s actually quite scary! Look up from centre stage and you’ll find literally tonnes of equipment suspended above your head, including lighting, speaker stacks, video screens and more. Most of the set is remarkably heavy, quite a lot of it will probably move at some point during the show, and all of it needs to be dismantled and packed away into a truck, to be re-rigged somewhere else.
In the book “Entertainment Rigging for the 21st Century”** contributor Roy Bickel explains in his chapter on “Arena Rigging”:
“Shows are getting heavier too. Much heavier. The current roof load record for touring show is right around 240,000lbs. Load cells and other load of monitoring devices are frequently used to ensure these loads of complex structures are distributed properly… When you consider the sheer quantity of equipment hanging overhead, its weight, and the speed at which it is moving, the risks are too high to tolerate any sort of arrogant or careless behaviour. It’s also become clear that on-the-job training is no longer enough to provide the skills to work as an up or ground rigger.”
Keeping the show on the road
The stage set for The Killers “Wonderful Wonderful” world tour posed particular challenges, as outlined in an article for ET now. The set comprised of various different elements including the PA system, multiple lighting trusses, a surround video wall and large marquee style neon arrows suspended from the rigging. The finishing touch was an inverted triangle video wall suspended directly above the band’s heads. 56 load cells were used to pre-weigh the rig before the tour even started, and were used in the tour to monitor the 120 rigging points.
”One of the key concerns and reasons for implementing the load cells into the rig was to address the concern about safe and proper weight distribution across the spine truss and its five motors above. Triangles or pyramids are always tricky situations for rigging, having such a large portion of the weight of the element suspended in the middle.”
Michael Sorowka, CEO of Paradigm Rigging
The team also worked out a neat solution to avoid disconnecting the load cells between shows. Each truss was pre-rigged, and the load cells held in place during transport by bungee cords to avoid damage. Once at the venue, the wireless load cells were ‘woken up’ by the controller system, zeroed and checked. With the truss in place, the load cells would monitor the load distribution for the 12 individual motors used to build the video wall.
Circus circus
It’s not coincidence that another major festival, Bestival, has a circus theme this year. Circus has developed over the last two decades from its ring and sawdust origins to the high tech shows of Cirque du Soleil and similar groups. The need for reliable, robust rigs for aerial performances has grown immensely, and load cells have played their part. Aerial acts are now part of a wide variety of events from product launches to opera, and a whole range of venues, from traditional theatres to outside buildings.
For the riggers (those responsible for creating the structures required and assembling them), this can be a nightmare. Most non-theatrical spaces will feature unknown load capacities, or require a rig built from scratch. No wonder the forces generated in typical single point aerial dance trapeze acts became the subject of a thesis by James E. Vogel to:
“Provide myself, and other riggers, with the knowledge they need to properly rig aerial dance apparatus in spaces that were not originally designed as performance or rehearsal spaces.”
Load cell placement in an aerialist’s rig
A load cell was placed into the standard rigging required for this type of act, forming one of three links between the top sling that connects to the building structure, and the rope used by the aerialists. It’s interesting (and understandable) that the aerialists who featured in the research were initially suspicious of this new piece of kit introduced into their normal rig:
“To provide reassurance to the aerialists, a webbing loop was added in parallel to the load cell as a safety item. While the load cell rating was well over the anticipated load, it was a new piece of hardware and the aerialists were unfamiliar with it. The loop was long enough that it did not support any load.”
The load cell was used to monitor the forces exerted by the five principle movements in aerial dance: These five movements are: Sit-Mount; Track and Tap, Pegasus, Free-Fly, and SitBounce. The results surprised even the researchers:
“There appears to be only a loose correlation between the participant’s weight and the amount of force generated. While it might be expected that as the participant’s weight increases the force they generate also increases, in fact, in many cases, a lighter participant actually generated a significantly larger amount of force… much of the force generated depends on both the participant’s experience with aerial dance and the participant’s personal style of movement.”
Measuring sudden shock in single point rigging
Back in 2011, rigger Mike Estee wrote about the issues of designing rigging that was subject to sudden shock, such as the dropping in equipment. He used load cells to measure the shock load, and then developed a system which overlaid the data results over a video. Here’s the result for an aerial performer using a single rope:
Lifting load cells to new heights
We have years of experience in the design, manufacture and speedy delivery of both regular and bespoke load cells for a whole variety of research and entertainment applications. If you have an innovative project that requires load cells of any type, just give us a call.
REFERENCE:
** Entertainment Rigging for the 21st Century: Compilation of Work on Rigging Practices, Safety, and Related Topics • Bill Sapsis • CRC Press, 15 Sep 2014
