Perpendicular Wall Mounting of Scaff Tube?

[Seano]

The engineering company I use simply welded a large L bracket up, with a decent sized wall plate, and 75mm top plate that had bolt through clamps for the tube, and 10mm bolt holes for rawlbolt style fixings to the wall. Probably over the top, but it wasn't that expensive.

 

My first thought when I read the OP was a custom fabrication too. I'd also echo the suggestion to use a lightweight truss rather than a single bar, unless its a very short span.

 

 

Difference there is that with 5 SWR pickups, the majority of the load was likely suspended from those points. The clamps were likely just preventing the bar from moving around. Because SWR is not rigid, not securing the ends would permit movement of the bar which would look a bit rubbish in terms of the lights wobbling around.

 

Ah yes, no doubt that'll be why you never see an LX bar on a counterweight set in a theatre.

Oh, hang on...

[J Pearce]

Actually the end clamps in question make the bar movement worse, as they tend to oscillate in simple harmonic motion rather than just gently sway.

 

I'd agree though that they probably don't take much weight and probably have more use in holding the end of the bar in location allowing it to be wired in with solid core singles rather than flexible cable.

[brainwave-generator]

Difference there is that with 5 SWR pickups, the majority of the load was likely suspended from those points. The clamps were likely just preventing the bar from moving around. Because SWR is not rigid, not securing the ends would permit movement of the bar which would look a bit rubbish in terms of the lights wobbling around.

 

Ah yes, no doubt that'll be why you never see an LX bar on a counterweight set in a theatre.

Oh, hang on...

 

I would say that counterweight counts as 'secured'. I didn't say it had to be secured to something immovable.

 

I said if you want a bar that stays still. I would say that, generally speaking, the whole point of a counterweight system is quite the opposite to "a bar that stays still", would you not?

[kerry davies]

Yes truss would be better and could form a box above the stage giving you far more flexibility though I suspect costs are a factor. What Paul suggests, L beams on the wall with U-bolts locating the tube, is also a good method and allows removal of the tube more easily than the end brackets.

 

Unless the hall/stage is very narrow I can't see a single span being long enough to cross the great divide and you might need to span from one wall to the centre, in which case end brackets are a little risky and Paul's L beam is your answer. Might even be a good idea to fix long L beams front to back to give ultimate flexibility.

[gafferted]

This may be a dumb answer, but I'd be quite keen to find out why it wouldn't work if it is that silly a suggestion!

 

 

Do you have to go to the expense of brackets? Why not drill the wall with a core drill say 3 inch diameter and bed the ends of the bars into the wall with mortar?

 

If the bars run wall to wall they can't com out and will surely take all the weight you want?

 

Builders rest beams, joists etc in holes in brickwork all the time.

[Brian]

If the bars run wall to wall they can't come out and will surely take all the weight you want?

As the bar is loaded and unloaded it will flex. As it flexes it will crack the rigid mortar. This is clearly a Bad Thing

[gafferted]

Agree.

Flexing of the bar is a real problem.

With a rigid bracket the effective shortening (however small) will surely cause the wall bolts to work loose.

At least with the bars in holes in the wall they will never be in danger of falling even if they are not a dead tight fit.

They will tend to gradually damage the wall if there is any end float but the gravloks to the centre I-beam should prevent that.

[Rigger]

Perhaps I am missing something but how big are the wooden beams? If a structural engineer inspects the premisis it may be the case that the central beam and off stage wooden beams may be ample to take the (currently un specified) weight required of the project. A local theatre used to have 3 wooden beams each with a UDL rating of 350Kg each. calculations may work out that the central beam may take in excess of 50% of the gross load and it may be that no weight is required to be taken by the wall at all. Surely the best advice is don't ask people who arent there, employ a professional to inspect the premises and give you an answer. This may prove cheaper than you think.

 

There is no need to stabalise a non dynamic installation.