steve h Posted May 8, 2008 Share Posted May 8, 2008 Just a quick question. Ive currently got 4 Mac250s hanging on the same bar. Looks great Only problem im having is that when they all start to move...so does the bar! I've lowered the p/t speed, but its still occuring when they all move. Is there anything I can do to the bar to help stop this? Its happened a couple of times now. This second bar is pretty close to the ceiling, as in there is only a few inches between the bolts holding it to the ceiling and the bar - Its held in 4 places by rods. The first bar I have had them on previously was about 3 foot below the ceiling on 4 rods. I thought this was why it was wobbling, but obviously not! As I've said, is there anything else I can do to help stop this? Thanks Steve Link to comment Share on other sites More sharing options...
david.elsbury Posted May 8, 2008 Share Posted May 8, 2008 Is there another bar nearby you can brace to with lengths of pipe and clamps? Link to comment Share on other sites More sharing options...
3guk Posted May 8, 2008 Share Posted May 8, 2008 We have stopped this before by bracing with lengths of scaff attached to floor plates used in reverse. You put the floor plate up against the ceiling to stop damage, and then the vertical scaff bar is attached to the lighting bar with a 90degree clamp. Has worked for us in a fair few number of venues in the past. Link to comment Share on other sites More sharing options...
dave_m Posted May 8, 2008 Share Posted May 8, 2008 If they're just doing a simple movement, such as in a disco, what about inverting pan on two of the units? This should help to counterbalance the other two units? Otherwise, is there nothing you can run a spreader to? Another bar perhaps? This makes it "harder" for the units to wobble the bar, as ther is an additional load for them to move. This might helpLinky Just a couple of suggestions, I'm not a rigger, and I'm sure if I'm wrong someone will correct me! Link to comment Share on other sites More sharing options...
matt c Posted May 8, 2008 Share Posted May 8, 2008 I'm no mechanical engineer, but I would guess that the fixings and/or the thing you are fixing to (the ceiling) are inadequate for the forces involved. I would look at bracing the bar in three dimensions, for example by using something (additional rod?) to form triangles (the strongest shape ever...) Matt Edit.. Beaten to it. Must learn to type quicker. Link to comment Share on other sites More sharing options...
steve h Posted May 8, 2008 Author Share Posted May 8, 2008 Thanks for all your replies so far. It does look like bracing is the right way to go. We've even got some spare poles backstage! I'm no mechanical engineer, but I would guess that the fixings and/or the thing you are fixing to (the ceiling) are inadequate for the forces involved. Just to point out before we bought the Macs I phoned the company that installed the bars and checked the limits on them and they said they were fine! Link to comment Share on other sites More sharing options...
ceecrb1 Posted May 8, 2008 Share Posted May 8, 2008 Is it possible to put a short bar perpendicular to the orriginal... with verticals on each end just touching the ceiling? Link to comment Share on other sites More sharing options...
paulears Posted May 8, 2008 Share Posted May 8, 2008 Moving heads on counterweight bars do exactly the same thing - however the weight usually cancels the movement fairly quickly. Link to comment Share on other sites More sharing options...
The Gaffa Posted May 9, 2008 Share Posted May 9, 2008 Bracing the bar works, If its a Flown bar try using brailling lines going upstage / down stage tied off to something solid. Link to comment Share on other sites More sharing options...
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