Rigging Question (Tieing off a line set)
- Thread starterwemeck
- Start date
We are thinking more along the lines of a claw type mechanism that would clamp onto the pully and push the rope into the pully and make the tip of the clamp a rubber material. The down-side is that it isn't moveable and it isn't a tool that can be used anywhere. Just doing some brainstorming and throwing out ideas!
Thanks again everyone! Really appreciate it.
Thanks again everyone! Really appreciate it.
porkchop
Well-Known Member
I work at a theatre at home that more or less has one set of locks at stage level and one more full set and the mid rail. They are both standard rope brakes though and are not made for more than 50 pounds out of weight.
That sounds to me like something to me that might damage the rope if used very often. Since you said you have to figure this out yourself I will say just remember that a Klein Haven’s® Grip (a.k.a. porkchop, no relation) works great but will cause serious damage to aircraft cable over time.
That sounds to me like something to me that might damage the rope if used very often. Since you said you have to figure this out yourself I will say just remember that a Klein Haven’s® Grip (a.k.a. porkchop, no relation) works great but will cause serious damage to aircraft cable over time.
I've never worked in such a theatre. But it seems to me from the houses I've seen, they keep ALL the locks at either deck OR fly floor open. I think it would get very confusing if some were locked and others open, in both locations.
Sure, after the 1000th show, it becomes automatic, muscle memory takes over.
porkchop
Well-Known Member
You sir are correct. I never said it was a good system, I just said it was the system they had. As a side note, unless the particular show requires otherwise during the run the locks on the mid rail are left open. On the other hand during a rig call when you have crew members at both levels it's not uncommon to have both brakes closed as well as hands on the line at times (again not the best way, just their way).
lwinters630
Well-Known Member
A lot of discussion seems to be focused on using this proposed tool to lock an out of balance line set. The head block, steel cables and arbors can hold about 1000# however the point is that the line (not just the lock) is not rated nearly that high.
Assuming this tool is being used as a safety devise as to not rely on the lock, it would need to be able to release and re-grip quickly.
A tool in the wrong inexperienced hands IE high schools, will result in death.
Assuming this tool is being used as a safety devise as to not rely on the lock, it would need to be able to release and re-grip quickly.
A tool in the wrong inexperienced hands IE high schools, will result in death.
MPowers
Well-Known Member
Ummmmm, your math needs a touch of re-figuring.
First, head blocks, are rated far higher than 1,000#. They are manufactured and rated for the loads of the particular line set they are intended for. A standard 6 line head block from a major manufacturer for example:
Second, Wire rope, A.K.A. Galvanized Aircraft Cable (GAC) or Small Diameter Specialty Cable is also sized for the purpose. The most common GAC size for manual counterweight systems is 1/4" with a breaking strength of 7,000# and a rated WLL of 875#. With a minimum of 4 lift lines per line set, that is a total load capacity of 3,500# (some systems installed prior to 1960 and not upgraded to match current standard rigging practice, may have only 3 lift lines.)
Third, Although a standard rope lock is intentionally limited to a 50# load holding capacity, both J.R. Clancy and Tiffin have models rated at 1,500#.
Fourth, 3/4" Multiline II, arguably the most common purchase line in the U.S., has a WLL of 1,505#. Stage Set X is rated at 2,514#. Those are WLL not breaking strength.
Fifth, the tool being discussed is intended as a safety device, NOT a rope lock. It is intended to secure a line set ONLY while loading or un-loading, NOT during normal use. Therefore it has absolutely no need to
.
Last, I agree with the concept that any tool, in the wrong, inexperienced or untrained hands, can be dangerous. Stage rigging, especially what the public calls "Fly" systems are inherently dangerous under the best of circumstances. Theatre/Entertainment Industry is the only industry in the world that allows lifting, moving and suspending loads above people, i.e. performers, presenters and audience members. The fact that we, the industry, and the national education program, entrusts these systems to administrators, English teachers, choir directors et al, with absolutely no training or education in their use; mystifies me. Any device, program or inventions that improves the safety of rigging systems, without completely compromising their use, has my stamp of approval.
MPowers
Well-Known Member
I have indeed seen the product, but only in the demo version. The concept is excellent and a product that is long past due in the industry. At least one other major manufacturer, that I have close contact with, liked the idea so much that they are in the process of developing a similar product. Of course they are also working on staying away from any patent infringements while they are at it.
As for the Clancy product, talking with one of their engineers, in October, they expected it to actually be on the market by this year's USITT or sooner. However, at that time it was still in the beta +1 stage, there still some things to improve on.
Some unanswered questions are:
What happens in the real world when the unit is activated? Is there a shock load imparted on the system and if so, what are the results of that shockloading on the other components of the system or the building structure.
The JRC head block is a head block, not a traction drive pulley. If the system is in motion, how fast is out of ballance condition detected and how rapidly is it stopped? If it locks up instantly will the lines breifly slip, effectively "sawing" the grooves of the block?
How many times can a unit be activated before it needs to be replaced? Note: if you experience enough run-aways to need an answer to this question there is a major problem with your system and/or your loading proceedure.
As for the Clancy product, talking with one of their engineers, in October, they expected it to actually be on the market by this year's USITT or sooner. However, at that time it was still in the beta +1 stage, there still some things to improve on.
Some unanswered questions are:
What happens in the real world when the unit is activated? Is there a shock load imparted on the system and if so, what are the results of that shockloading on the other components of the system or the building structure.
The JRC head block is a head block, not a traction drive pulley. If the system is in motion, how fast is out of ballance condition detected and how rapidly is it stopped? If it locks up instantly will the lines breifly slip, effectively "sawing" the grooves of the block?
How many times can a unit be activated before it needs to be replaced? Note: if you experience enough run-aways to need an answer to this question there is a major problem with your system and/or your loading proceedure.
BillConnerFASTC
Well-Known Member
If the tension block or welsh block is today's typical such block that is mounted to the "T" or "J" bar guides, those guides and that mounting have not traditionally been designed for the out of balance loads that an Uncle Buddy tool would put on it. Blocks that are mounted to the floor and don't slide, or perhaps if a manufacturer has done the engineering to show the guides are indeed strong enough, would of course change this. The purchase line is plenty strong enough to hold most arbors hanging on it as are the head blocks. I much prefer designing and installing the lockrail with snubbing links to tie off the out of balance load.
Jury is still out on the JRC SureStop head block, IMHO.
Jury is still out on the JRC SureStop head block, IMHO.
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What Rigger?
I'm so fly....I Neverland.
Not so sure that Petzl makes a rope grab for this application. Are you talking about a Croll toothed ascender? An I'D? Or an ASAP? What type of rope was in their system? Very curious to know.
Is these things breaking a common thing?
We want to use them to hold our electrics during hang. Never more than maybe 150 out of weight tops.
Is this a dangerous option?
Yes. It is dangerous. Also, during hang you should have all the weight dropped from the arbor anyway.... In my view there is NEVER a time when and electric should be arbor heavy or out of weight for that matter. These methods should really only be used when hanging an item like a soft good or hard scenery that can not have the full weight on the pipe until it is in the air. Electrics on the other hand can be hung while the pipe is at working height/bottomed out then weighted.
I realize that I made it sound like we were stripping the E and leaving weight on the arbor. Its more a process of "morphing" the rep plot into the show plot. We never change the pipe weight by more than maybe 50-100#at most, usually it is only a brick out of weight. Does that change the circumstances?
How much welding have you done? How much structural design have you done?
I have flown people 40' off deck on my welds... and I still won't make one of these. A properly done snub line does nothing more then keep the wraps of the purchase line together... and that is where the real holding power is. You add that to bull lines on the deck with meat on them and you have a safe-er situation. I have seen uncle buddies go flying across fly floors before because they get over loaded or more likely not installed right.
I've been welding since high school metal shop where I got four years of instruction. so just shy of a decade.
When it comes to structural design, I am more of a as needed problem solver.
Then nope, your not qualified to do this even if it was a good idea... Listen to your professor.
