Lighting nuts & bolts:-

The actual mechanics of stage lighting are rarely covered in any detail in text books, so we hope to offer a few guidelines here.
In broad terms stage lighting fixtures, (lanterns) are either hung from bars or supported by stands. ‘Trussing’ is sometimes used on bigger events, and this is really just the same as bars, but with extra strength to handle more weight across a wider unsupported span.
Within the theatre and stage industry bars are always 50mm diameter (one and seven-eights inch in real measures)…that’s standard scaff bar size. The hook clamps used to hang lanterns from bars are designed to fit this size.
Whatever methods of suspension or support you use, the major priority is to ensure that it is secure. A stand that falls over or a bar that falls down will cause extensive and expensive damage to your lighting equipment. (or ours if it happens to be hired!)
(And it might hurt someone!)
Stands generally need a bit of thought if an audience is present, as the legs will almost invariably stick out into the hall floor area. Audiences, being universally clumsy by nature, will immediately trip over these legs. Even if they can be forced to see the legs by having them fenced in, or made conspicuous by hazard warning tape etc. the audience will tend to crowd close to them.
If you can tie off any stands that you use to reduce the chance of them being toppled by this sort of clumsiness so much the better. Remember always to adjust any gangways or seating to suit the needs of stand based lighting (or sound), and to make sure that you are complying with any local regulations on gangway widths and so on.
That said, at the top of the stand there are two ways in which lanterns may be attached:-
A spigot fitting arrangement, that will take a single lantern, and consists of a pin that drops into the top of the stand tube (or sometimes a sleeve that fits round the outside of the stand top.
Or a ‘T’ bar, which will be fixed to the top of the stand by either a spigot, or a fitting that slides over the outside of the top of the stand, and is usually a bar with about 4 drillings through it to take bolts to suspend lanterns.
In all cases the fixing bolt is now usually M10 (M12 for bigger heavier lanterns) and is passed up through the yoke of the lantern so that the bolt-head is inside the yoke. The bolt then passes through either the hook-clamp, or the T bar, and is secured by the nut or wing-nut. It is customary to put a washer between the nut and the hook-clamp or T bar drilling and sensible to put a split washer next to the nut to reduce the risk of the nut working loose.
Wing-nuts are usually perfectly adequate for most lanterns. There is a tendency to use hex-nuts and tighten them when focussing with a spanner. This has some slight advantages in big rigs where access is difficult and there is a risk of lanterns being knocked out of focus, but is generally a curse in small scale rigs as re-focussing is rendered more awkward, and in any case amateur shows tend not to run for long enough to have problems with lanterns drifting out of position.
The ‘fixture’ or lantern should have a secondary means of support in case the nut & bolt assembly does come undone. This was traditionally a ‘safety chain’ but has been replaced by a steel wire bond.
Don’t forget that there may be a requirement to secure accessories such as barndoors, effects wheels and so on to the rigging by a secondary bond too.
Where there are no rigging positions (lighting bars) it is sometimes possible to install a temporary bar by hanging from beams or RSJs in the building. Make sure, when doing this, that the building structure you are fixing to is sufficient for the weight of the bar and associated lanterns and cable, (seek expert advice if necessary) and that the method you use to attach the bar is safe. Suitable fixing methods for a temporary bar slung below an RSJ would include:- specialist RSJ clamps & steel fixings to the bar, hanging chains (that’s not safety chains), steel hanging wires, or specialist webbing slings & shackles. Remember with any of the flexible fixings listed above that weight capacity is reduced when they are used in certain configurations. In any case ensure that the SWL of the fixings you are using (and there should always be 3 or more for a bar) is adequate. Again seek expert advice.
It’s worth remembering that stands have a, usually quite small, SWL (weight carrying capacity), so take some care not to overload a stand or stands.
When working out your weights don’t forget to allow for the weight of the bar (which may not be too great if you are (as you should be) using aluminium bar) and for the cables as well as the lanterns. Cable weight is much more significant than you think!
Internally wired bars (where the cables are run through the bar and come out at a series of outlets along the length), can be hired and save much labour during rigging as well as cable tangles in the air!
Structures having vertical pillars (such as churches or marquees) may lend themselves to lashing the bars directly to the post or pillar at a suitable height (we generally use a ratchet-strap) or ‘handyclamp’, which is quite a clever little gadget designed specifically for these sorts of situations. Handyclamp provides a right-angled bracket with 2 M10 studs on the end, and is available for hire.
Churches may be sensitive about lashing to pillars. Arrange to protect the building fabric in some way from contact with nasty hard metal. (?car mats again!)
Phosphene now also stocks wind up stands in hire. Although these do not gain you great heights (just over 4m… that’s a bit over 13 feet in real measures) they do take much of the effort out of shoving LX gear up when extending the stand.
Remember with all LX rigging that the lanterns get very hot. If you are lashing stands or bars off, make sure that the tie is well clear of the equipment. Keep your lanterns away from curtains and marquee roofs and linings.