sunray

Errr... I am not a rigger and I could be one of those people who don't understand it but is this actually correct? For a static hanging load isn't the load on the bar the same whether it is secured to the bar or on a rope over a pulley held from the ground. There will of course be dynamic forces from pulling and getting the load moving as you mentioned. But I don't think you immediately put 200% load on the bar. I am going away to draw some force diagrams. Edit, ok I've thought about it more and you're right. If the load was equal to you in weight you'd be hanging from the rope and the force on the pulley would therefore be you + the load so 2x the load itself. So your assertion about a lot of people not understanding is obviously true. It's not obvious is it Tim? Thanks for following it through. One of my colleagues (who hangs lighting and sound kit) has read my post and didn't understand either, after I explained about 3 times I saw on his face that the penny dropped and his comment was: " ***k no... I mean yes" So I'll try to clarify my earlier comments. A static load of 30Kg suspended from a bar will exert 30Kg on the bar, regardless of the method of fixing it to the bar. Passing a rope over a bar with a load of 30Kg on one end will need a load of 30Kg on the other end to balance it (just like a balance scale or see-saw), therefore both loads will be exerting their 30Kg or a total of 60Kg on the bar. It matters not how that 30Kg balance load is applied, it can be a 30Kg weight, a person pulling or even a static fixing to the floor below. I hope that makes it easier to understand.

I have one of these: https://www.ebay.co.uk/itm/3KM-Long-Range-2CH-Remote-Control-Switch-System-Wireless-Transmitter-Receiver/312748523491?hash=item48d143bfe3:g:3OIAAOSw5wVdZ42O Single channel, latching. It seems to be instant and so far has worked perfectly up to 150m. Spec says 3Km It appears to be reprogrammable but I haven't looked at what it can do.

Just to jump in here - you need to check if that's the maximum load or the "safe working load" for these brackets or indeed anything else you ever use for rigging things over people's heads. A SWL is usually allowing 300% safety factor (ie something with 100kg SWL is actually designed to withstand 300kg) right up to an 800% factor depending on the product and manufacturers tolerances. This is especially important in theatre because of all the incidental forces applied whilst doing the job as a whole - suppose you had a bar with a maximum load of 200kg, you have 150kg of "lights" already on it and you decide to add a 30kg moving light; because it's heavy you use a rope and someone pulling on the ground to lift it up.... you're almost certainly going to be well over the maximum load for the part because a) everyone forgets or underestimates the weight of cables/clamps and b) the dynamic load caused by someone on the ground pulling the rope that goes up over the bar can easily exceed 30kg weight of the object so you potentially have a problem. Conversely if the bar you're rigging from has an SWL of 200kg then you don't need to be too concerned about going (briefly) over-load because there's a safety factor built in. There was an incident at Ringling Brothers Circus a couple of years ago where a dozen aerialists hanging from a frame were dropped to the ground suffering life changing industries - after all the investigations the main factor was that someone had used a component rated at XXXXkg and assumed that was actually its SWL so didn't take in to account the extra forces applied by the moving performers nor the inevitable decline in the parts strength as it sustained wear and tear. There's also added complexities that loads don't distribute evenly to the pick up points used so even if you have got a bar with 3x200kg SWL clamps on it that doesn't mean you could hang a 600kg object from the bar (unless it was multiple objects, evenly distributed and the bar itself was very strong) this is why there's lots of specialist engineering firms with expensive computer simulation software to calculate what really happens with the forces in play. I don't want this to sound like I'm criticising you in any way - by admitting you were not sure and doing some research you are already more safe and more sensible than the majority of people, I just want to make sure that no one else reads this little bit of knowledge and misuses it somewhere else Wow a brilliant post. I'll reiterate the bit about loading during hoisting and how it is not understood by far too many people involved in the practice, a load of 30Kg suspended on a rope over the bar and back down will instantly impose a load of 60Kg. The friction applied while hoisting may increase that by another 30Kg quite easily, then depending on the smoothness of the bar and the type of rope and the jerking action there is easily another 30Kg. The jerking is generated by the stop/start action of hand over hand and the bumps in the shape (make up) of the rope. this is usually visible by watching how the existing lamps vibrate during hoisting. It's easy to reach 400% of the weight or more of a load by running a rope over a fixed point, using a decent pully will usually reduce that to 300% but it is not possible to get down to anywhere near 200%. As above don't forget to include ancilliaries in the load calculations, I have seen a 20ft ali bar loaded with 24 parcans suspended on 2 blue ropes, the rigger knew the weight of the fittings as 2.5lbs and worked on 60lbs total weight. He had not allowed for the bar, hook clamps, colour frames, barn doors, 15A plugs & sockets or 24 runs of 2.5mm2 HO7 which all came from one end and were suspended from the wall several metres away. He had also not estimated the effect of the heat on the rope and one softened to the point it failed, the other rope failed as the bar swung down. Fortunatly the hall was empty during the rehearsal but the weight made it a bit of a struggle for 2 of us to lift it to one side.

Have you? Or were you yellow carded for that... and then red carded for your response to the yellow.... Yes the later. Initially I thought the H&S guy was having a laugh when he told me I had to use the trapdoor and got back on the platform then received the yellow, I asked him to demonstrate the process (which he refused) as I was not prepared to put myself at risk by concorting myself through the trapdoor, I asked for a second opinion and when he stated his decision is final I phoned HSE for their thoughts. HSE seemed very interested when I mentioned which site I was on and they suggested that my RA should be good enough in that specific situation and actually asked me to step down, if I was confident it was the safest method, while on the phone. I did and was promptly red carded. HSE asked me to remain where on the phone and were I was, they were there within a few minutes and got the site closed pending some issues. The site H&S guy was quickly moved off site and things improved without him. I called HSE to another site where we were wiring (soldering) floor boxes and removed our boots to prevent toes being damaged by the toe caps, HSE agreed with us and site gave us dispensation to wear trainers while kneeling to do the job. I know H&S is difficult to administer but it doesn't have to be made worse by dictatorial Hitleresque idiots without common sense. They are not all like that, in fact I'd say that in more recent times most are pretty good at assessing situations quite well.

Thanks, I thought it was something like that when I looked at the website. It seems Harman are taking over many companies.

Agreed, I have been yellow carded for using a 6x4ft 3m high tower without outriggers to reach the 4m high slab in a room less than 8x6ft. The hire company didn't even suggest outriggers for such a small hire. I've also been yellow and red carded for not using the trap door in a platform less than 600mm off the floor.

Sorry, totally OT but what has happened to Martin these days.in 1995/6 I worked for an install company who 'rented' one of their properties in Maidstone,and were one of their preferred contractors. Last year I went to Martin's ex place to attempt to get a part but of course they're not there anymore.

I don't know about NZ but I think Clive has it just about right over here. In my experience with schools they tend to get one person to train for rigging lights and add that to their insurance. Hands immaculately scrubbed.

I tried some about 30 years ago but they were carp. One half was basically the head end of a nail and the other passed over it and 'clamped' under the head. They felt firm but there was not enough friction to stop the two halves rotating with only a little effort, even the weight of the cable was enough to turn it. I don't do enough mic stand work to make the effort to look again.

One guy I used to meet ocassionally carried broken clothes pegs to use as wedges

In my experience schools [in particular for the summer fete] seem to rely on PAT stickers as a safe practice system. The alarm bells ring when I'm presented with a JoJo style domestic reel for the PA system and as described above it frequently consists of a series of similar cables, often feeding multiple stalls from the daisy chain including the tea tent with an urn or two. It's rare that I go to these events without having done a site survey and my own mains cables and I've lost count of the number of times I've sorted their system.

I remember the days when we could rely on the squelch and would regularly leave leave a radio mic open on a PA system for the MC to use it whenever he wished, we also used VOX or the squelch line to mute the music without notable issues.

Likewise - makes an excellent stage-weight or doorstop :) The Behringer PS400 fits you size criteria, but has no gain adjustment, & needs 12V, which isn't ideal for battery-powering. I bought a Studiospares Red-something at a trade show some years back, which did have a gain control. Unfortunately this cut from zero to about 20dB gain as you moved the pot from near zero . Used once, causing a highly embarrassing moment, & promptly returned for refund. This was the last time I trusted any of their specs. At school (1970-72) we had a microphone mixer - metal box 2x2x6", 5 sockets, 4 rotary pots and a PP3 but no power switch so it was always flat when we tried to use it. The first 1/4 of movement did nothing for the channel concerned but it did affect the other 3 channels, then to full volume in about 30o and the remainder of the travel did nothing.

I have known a whole 48 way XLR patch cable (4U plate at each end of a cable in racks) wired with a 1/2 flip and it had been in use for a couple of years before I tried running a phantom powered mic. The installers had blamed the noise on the cable route as the multicore ran through a very large plant room and a busy cable riser. It took me less than an hour to correct it. And the conferencing system on a boardroom table (XLR's mounted in table for gooseneck mics) XLR's wired incorrectly and the correction made in an EDAC so the cable screen and red wire were flipped at the back of the rack. Again it had been like it for a while with constant conplaints of noise on audio but I suspect there was no data or video running when inspected. Yes a very easy mistake to make especially when wiring a mixture of male and female chassis mounted connectors.

I have (very buried under loads of unused kit) a 'Drake' card frame with a number of cards containing one pre-amp each running on +/- 15v with a fairly good input transformer. They are obviuosly larger than your suggested size and will take a while to dig out. But they may make a starting point. It's been a long time since I've seen the unit so I'll predict there are about 6 cards.

Well as far as I'm concerned the original thread was the 1/2", in the 50's we had (and possibly may still have) microphones by Trix, Lustraphone and Vortexion. We had (and possibly may still have) 2 mic stands to match and then the inevitable happened and a new mic in about 1962 had a 1/4" female fitting and an adapter was quickly sourced and fitted to make it compatible. We stayed with that format until 1977 when Jubilee celebrations required loads of kit and suddenly 5/8" seemed to be the 'new' standard and we suddenly had a load of adapters of all sizes (and chaos). Then the lighting bolt size of 3/8 joined in. By then all of the old mics were retired and allof our stands became 5/8". We also had a massive stand with a heavy 1/2cwt cast base and matching big brass mic which had a much bigger thread, more like 1". Users these days are soooooo lucky!

That's cool, as I said it would have taken a while to sort.Update:Following a chat with me they were in fact retired when he had a big clear out a little while back. A quick work out tells me the last time they were used may have been last century so it was certainly time they did go.

These are 12" (and some 9" too) CRT's which stack very well, not these models: https://www.ebay.co.uk/itm/Sony-PVM-9040ME-Monitor-/303284645438 but that general design and only RGB/RGBHV. I've sent a message asking if they're still available but as I said he is away and virtually out of contact with the world. I'll only be looking for delivery costs from Kent. These are 12" (and some 9" too) CRT's which stack very well, not these models: https://www.ebay.co.uk/itm/Sony-PVM-9040ME-Monitor-/303284645438 but that general design and only RGB/RGBHV. I've sent a message asking if they're still available but as I said he is away and virtually out of contact with the world. I'll only be looking for delivery costs from Kent.

I lent some 12" RGB/RGBHV CRT monitors in square metal cases a while ago, he used them as camera monitors when helping out at a school. I know they are not currently being used. I also know he had a clearout earlier this year and he is away for the rest of this month. Any use?

Does it have to sit on the back of a monitor? I think I still have a Sony switcher (3u unit) originally tailored to a CRT projector with I'p modules. I'm pretty sure it would have had RGB/RGBHV. I'd love to find a home for it... and the damaged video multicore that went with it.

I have a Cobra clone and a Chauvet designer 50, they are both S/H off Ebay and have back up batteries of unknown vintage and I've found the symptoms described with both.My theory is the desk fails start up checks due to the flat battery after a long period of no use. Unplugging and repowering does nothing and neither does leaving it plugged in.But after several hours of being plugged in and the battery is charged, I've found powering down, leaving for 30 seconds or so and repowering it then completes its checks and works OK. It even still has the memories safe.

If these are for permanent install, my go to was always Schroff racks. The company I used to get them from ceased trading (Believe it or not, due to 9/11 when many of their customers folded) but I'd get occassional spares from RS. Prism make 'Data' cabinets but are lighter weight. None of this type of kit is suitable for road use. A search for 'flightcase rack' brings a selection.I'm sure others will start offering their preferred makers names

I used this sort of stuff: https://www.ebay.co.uk/itm/UK-Neon-LED-Light-Glow-EL-Wire-String-Rope-Tube-Car-Xmas-Lights-Battery-Operated/254342217485?hash=item3b37fa3f0d:m:m3y0W9NcePuGkZMclzJPRCw to make up a multipurpose sign, on the single board we had 'Hotel', 'Coffee Shop' & 'Home Sweet Home' in 5 different colours. In our case it was mounted on a (Rotten) black painted scaff plank suspended behind a border made of plain domestic net curtains sprayed with matt black rattle can. We had the luxury of being able to avoid illuminating the border with other lamps as I suspect the shiny tube would have shown through. Prior to that I did a sign 'Bar' with an arrow under by drilling every 1/4" along the writing and glueing a 3mm LED in place. 'Bar' was alternate red and green to be able to make it change colour and the arrow was wired as 4 circuits to be able to make it move.The board was about 3x2ft 4mm ply painted matt black after drilling and before the LEDs fitted.

+1 for that. People still turn up with CDs and weird media. I'm finding cassettes are coming back. And if I record an event (ie: I do PA for real eastate auctions) I always use a cassette in addition to digital, in case there's a power failure.

That's good.Let us know how it goes.