Setting up trussing

[lonfire]

Hi,

I have recently bourght a whole load of second hand astralite 4.. I have used it a couple of times for small goalpost rigs and such like with no problems.. however the next time I need to use it I need to make a 9mx4mx3m (WxDxH) rectangle.. basicaly a rectangle with legs..

 

how do people suggest I go about setting this up? the legs are 3m peices, so making the top rectangle then trying to put the legs on might be difficult?

 

I did wonder if it would work better if I hired 4 windup stands and made the top rectangle on that and then wound it up and put the legs on?

 

any good books people recomend for doing trussing work??

 

thanks

chris

[Jivemaster]

Firstly there are two books by Chris Higgs Who is a member of this forum.

ISBN: 1 904031 12 9

Title: An Introduction to Rigging in the Entertainment Industry

 

ISBN: 1 904031 21 8

Title: Rigging for Entertainment: Regulations and Practice

 

 

www.etnow.com/books - check rigging and safety respectively

 

Secondly there are NO books that will teach you to rig. You need books and experience.

 

Assuming it is genuine Astralite 4, and every piece recently inspected Litestructures may guide you through the calculations.

9 metres is a long way for astralite Have you checked that this length is ok and has an adequate SWL

See this page http://www.litestructures.co.uk/products/t...ralite_spec.htm

 

and note their caveat;

NOTE ! - The load capacity stated above is meant as a general guideline. Details of weight loading can be obtained on request. Installation work should be carried out by qualified personnel and in compliance the the relevant legal regulations. We will not accept liability for applications that have not been tested by our technical department and approved in writing.

 

 

The wind up stands lift is one way, if the stands will take the load, lots of stands are only 35 - 50 kilos SWL. Also this doesnt mean that four stands wil lift four times the swl as the load will never distribute evenly as the stands are wound up. Four stands would typically take only twice the swl of one stand.

 

You need a competantly prepared method statement with all the calculations, to show that the design is ok, and the method of assembly and erection is safe. Without this you are un-insurable.

[lonfire]

hi,

thanks for the reply.. the rig will be put up with nothing in place.. and it will only be used to hold drapes along the back.. and about 8 par cans on the front (4 either side) .. I am going to put another leg in the middle of the back section so the span is shorter..

 

the litestructures website doesn't show the weight per m of astralite 4.. I would of thought that would be a useful figure to know!.. somebody told me its about 4kg per metre.. so my top rectangle will be around 24m around.. so thats 96kg.. so with 4 windup stands where you could have only two points loads if you wind un-evenly they would have to be able to hold around 50kg each.. that sounds ok to me..

 

rgds

chris

[j_b]

Never say 'only drapes' when calculating weights in rigging.

 

Drapes are firstly quite heavy, a serge wool drape this size is probably just as heavy as all those par cans, if not more. A starcloth much heavier again.

 

And that's indoors. Put it outdoors, and let the wind blow at it, then it really is serious loading on the truss.

[lonfire]

hi,

indeeed.. I understand that drapes are heavy.. when I said only drapes I meant rather than a whole load of movers or such like.. I'm putting an extra support along the back due to the weight of the drapes..

 

thanks for the advice guys..

 

if people were going to raising such a rig.. how would you go about doing it?

 

rgds

chris

[Pete McCrea]

Get a rigging company in to do it for me.........And ask for their risk assessment, Method Statements, PLI Certificate, Employees Liability Insurance etc.

[Jivemaster]

Assuming it is genuine Astralite4 and all pieces are inspected, then draw or CAD a design and liase in writing with Litestructures, They may likely assist you.

 

Remember that the SWL of a truss assembly DECREASES with increasing span. And also remember that the truss assembly has a limiting length where its own weight equals its swl so the applied load has to be ZERO. Beyond this span the truss cannot support its own weight.

 

Chris Higgs book does give a method for assembling this shape truss without extra stands, though you have to do the calcs for the size of your rig.

[slim_mcslim]

from a practical point of view - I have done this several times, did it once with windups and found that was really pants... best method I have found is assemble the top rectangle completly, then if your using 3m legs you will need a 1m high platform to stand on ( I always find a wedge case handy) then two people just lift up 1 end, whilst a third person slips the leg in the hole, quite simple, do both legs at one end and then move to the other end and repeat...

 

not sure on the health and safety implications on lifting the truss at a funny angle, but quite frankly I don't care! as it is a method which works and isn't akward to achieve.

 

paul...

[lonfire]

hi,

I was thinking of making the back of the truss flat.. then push that up and secure it to the wall.. then put the two cross peices on that connect to the front and support them with two windup stands.. then make the front section flat and push that up to connect to the two side peices..

 

although your method might work ok.. although as this rig is quite wide and has extra support legs along it so will be quite heavy to lift..

 

thats the sort of input I was looking for (i.e. "I have done this before this way...").. cheers ;-)

 

will be doing more trussing work in the future so gonna find some courses and buy those books also.. also I've got a contact in a hire company that does some really big stuff so will get some advice off them also..

 

rgds

chris