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.
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.
Thanks for dropping by and checking out our venue. We have an amazing team of 7 technical directors running the 4 venues here. I do want to give credit to our supervisor, Michael Tipton, for allowing us to try out new and inventive ideas to make our operations safer. If anyone has any questions regarding this setup, feel free to email me at Robby.Elliott@MesaArtsCenter.com
ReplyDeleteI think is a really original setup. I would only be concerned about two things. When the rope grab is loaded is it applying the gripping force over a smaller area than say regular choker that is tied with a number of wraps around the rope. Also does the manufacturer of the rope grabs know you are using them in this fashion and is there a load rating on them?
ReplyDeleteThe manufacturer's data sheets for each of the components described, in addition to the rope hauling line, all show the devices to meet or exceed most reasonable out-of balance situations that might typically occur. In consideration that the rope lock and/or the rope lock mounting bolts are typically the weakest components in the system, this back-up safety arrangement appears to be a reasonable application of the available technology. The Rope Grab manufacturer was consulted and appeared to understand the application. Keep in mind that the rope grab (or a Choker / Prusik Hitch) is used in a pre-tensioned arrangement and is not intended to remain slack and then catch the line set moving at any substantial speed like might be encountered after a line set has already run-away for a few seconds. Keeping the system from moving is the goal, not catching it after it has gotten away from you.
DeleteHigher strength Rope Locks are available in the market place. An overview of them can be found at: http://theatreface.ning.com/profiles/blogs/rigging-runaways
Why are you using climbing gear for theatrical rigging? (i.e. the carabiner)
DeleteWhy would you allow your deckhands to unload linesets before the arbors are unloaded? Time constraint or not this is very basic safe practice. You should really know better.
Your roundsling is crushing the label.
To address many of your points for using this system....avoiding the need for this system by safe industry standard practice is the best way to keep your rail safe.
Neat use of "climbing" equipment my only concern is the possible cross-loading (twist) on the carabina if the system comes under load - there is a high possibility of the carabina failing across its gate as the rating on these devices is linear (along the long axis) and not a rotational load as pictured (sling and lock are at 90degrees to each other.
ReplyDeleteI have seen carabina's fail due to this cross-loading at as little as 80Kg of load when they are rated at 25Kn (check video whilst i accept the video is about climbing gear the same rules apply here also the applied load was directly across the gate) http://www.youtube.com/watch?v=5Fz0c1rC_88
Good point about the rotational loading of the carabiner. The addition of a second carabiner or a shackle would relax the system and nominally eliminate the twist. Note that more rhobust carabiners are also available (www.omegapac.com/itemdetail.php?id=93&secid=38), should you want to accommodate a larger margin of error.
ReplyDeleteIt should be noted that a SpanSet SteelTex Roundsling used in a Basket Hitch configuration (as shown around the Locking Rail) is rated for 10,600 pounds static load.
it should also be noted that rated climbing carabiners have a number for what load they can take across the gate. the most common ones will take 7kn.
ReplyDeleteI think this is a great idea, but I am having trouble buying the above product because it is intended for fall arrest applications and suppliers are not willing to sell the a rope grab for this application. I have also been looking for a manufactured Uncle Buddy, but have not turned up anything on that front either. Any ideas?
ReplyDeleteIt is my understanding that The Mesa Arts Center worked directly with the manufacturer to determine the applicability of their product to this use. Contact the manufacturer and see if they will connect you with an authorized reseller that will accommodate your needs or write you a letter that you can present to your local reseller.
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