"death Slide"

[APATM]

Hello everyone!

 

For a show I ma working on I am rigging a , shudder to say it, "Death Slide". I'm planning to use a steel wire rope under tension with a pulley. Working to a safety factor of 12:1, all rated, tested equipment.

 

Does anyone have an idea of how much tension the rope should be under, and any ideas on how to workout the forces on the fixing points and on the rope itself.

 

I have tried "Arena Rigging"( Great book) but this particular problem is a bit different.

 

Any help appreciated.

[PeterT]

I hate to say this but if I were asked to do this I would say no and tell them to get a professional flying effects company or circus rigging company to install it. I would recommend Freedom Flying as a fantastic company to deal with.

Don't forget it's not just the cable you need, it's the points that you attach it to that need to be strong as well, especially if your rope is under tension.

[robloxley]

Unfortunately it's a bit tricky. Firstly, you have to remember that your wire will never be straight - it'll always hang down at the point where the pulley and load is - and that point will change. Also you need to know things like the stretch characteristics of the wire rope. Also given the application, you need to thing about dynamic as well as static loading & there's a lot of room for nasty things to happen - e.g. the load is suddenly applied to the system. Really, you probably want to speak to a structural engineer.

 

As for your points, Hilti (and probably others) do a test guage that tests pull-out strength of your fixings. Often used by scaffolders to test points holding scaffolding to buildings.

[Kevin Robertson]

I agree with peter on this one.

Your safety factor of 12:1 is commendable, however I feel it will be of little use given the forces that will come into play here.

if you treat the tensioned wire rope as a bridle then you can work out the forces involved.

for instance:

If your tensioned wire rope has a SWL (using 12:1 SF) of 1000kg at an angle of 0 (hanging straight down). At an angle of 89 degrees the resultant SWL is only 17.4 kg.

There are massive forces at work here and every part of the system must be absoulutly safe to these forces. I would say that if you have any doubt about rigging this at all then don't. It could be potentially fatal.

However, I have done this on a number of occasions, and as long as you have done the maths before hand and have certification of the MBL of you equipment AND fixing points then it should not raise too many eyebrows.

[Rob]

As for your points, Hilti (and probably others) do a test guage that tests pull-out strength of your fixings. Often used by scaffolders to test points holding scaffolding to buildings.

 

How does this work then? Does it virtually pull the fixing out the wall to test it?

[Ike]

For a show I ma working on I am rigging a , shudder to say it, "Death Slide".

I have done this a few times before but never in a theatre environment. When I worked as a climbing instructor we used Petzl who gave some useful (free) advice as well as supplying equipment.

 

 

http://www.petzl.com/

[Chris Higgs]

The forces involved can be significant, but that is not the problem.

The engineering is relatively straightforward.

It the combination of length of line/angle, the environment over which the trick is rigged and the person doing the trick.Don't do it.

 

I have rigged a large number of these from as high as 50 feet high.

In every case the problems were either the means of access, the lack of 'bottle' on the part of the artiste and the speed of descent that resulted from the artiste going either too fast or too slow.

Show conditions make it all the more hazardous.

There is no redundancy in the system so a large factor of safety is required.

 

My advice is (strongly) do not do it yourself.

Get a rigging company or professional rigger to do it for you, include the 'emergency' planning, the risk assessment and the insurance!!

Sorry to pour cold water on the idea, but that is my best advice.

[Tom Baldwin]

There is no redundancy in the system so a large factor of safety is required.

Thanks for the interesting post, Chris.

 

To satisfy my idle curiosity, I wonder if you could share with us any thoughts on why these things are only done with a single wire, rather than say a pair of wires running through some sort of "dolly" type arrangement?

Would using two wires halve the risk of falls due to cable snapping/ point detachment, or is there more to it that that?

Obviously there is extra cost associated with more hardware and rigging, but how does the risk assessment work for that, in terms of the "as far as reasonably practicable" thing?

 

I've got no interest in attempting this myself, just seeking to be better informed.

 

Thanks,

 

Tom

[cybergibbons]

I have done this many a time with climbing gear - where the safety factors aren't quite as high... and there aren't any rules or laws governing you.

 

I know that SWR is very low stretch (once the initial stretch has been hung out), but it seems that doing it this way needs a lot of experience and work.

 

With rope, you use static rope and leave a fair bit of slack in the system. If you were to use dynamic, the tension has to be extremely high to stop huge amounts of sagging. This leaves very little overhead for the actual load on the rope. Static rope doesn't need this huge tension, and is in general stronger anyway.

 

Still, the loads on the anchors are immense - it can cause sizeable trees to bend and jam knots entirely. I'd never allow anyone but myself and friends who know what is going on onto the rope either - there is just too much risk involved.

 

Andrew

[Chris Higgs]

There are a number of reasons why a single line will be satisfactory, mainly engineering decisions.

The large safety factor is used because there is no redundancy in the system.

Friction and the amount of stuff involved (particularly in the type used by the military with handbrakes and so on) should mean only a minimal amount of housekeeping needs to be done by the slidee.

One type I used a lot for amateur "Barnum!"s was a combination rope with a leather sleeve. The tension is minimal, but the knack is the angle and length of slide and the tension/friction ratio required.

The problems stem from the bottle (or lack of it) of the trained and rehearsed, insured and authorised performer. The rescue facility and procedure must be in place before the first rehearsal, and the rehearsal should be graded from a few feet progressively up to the full distance.

Running out of steam, grip or whatever 30 feet above the ground is not in the plan.

 

Not wishing to repeat myself again, if you do not understand it, don't do it.

Are your insurers aware that you are carrying out this kind of work?

 

Many of these posts suggest "a little knowledge is a dangerous thing".

There is little understanding of safety factors or safe working loads displayed.

I would implore everyone to check their figures with a competent person before posting advice on these types of topic, and certainly before acting on any advice, (including mine!).

[dominicgross]

If I recall correctly, they used a 'death slide' type thing on ITV Gladiators in the olden days.

 

It was rigged by unusual who are quite a helpful bunch. Maybe it is worth giving them a call and seeing what they recommend?

[trussmonkey]

maybe you could look at rigging some sort of controlled slide. where by the performer is lowered by a rigger along a cable rather than allowed to free slide.

[Chris Higgs]

Unusual did the one over the Thames for the TV thing as well. Ask for Robin Elias.

(Hope this doesn't count as advertising........)

[Kev.L]

I would also recommend speaking to Ken Memhed @ Vertigo Rigging as I worked with him installing the same type of system at legoland for the summer season a few years back and he designed and built a carriage system which had a brake and safety system built into it.