I didn't know the answer, so I had to look it up; it sems to be 2048 x
1080 for the current, second, generation of machines. This can be reduced if a wider or narrower aspect ratio is being shown. As an alternative, for 'Scope' films a 1.25x anamorphic lens can be used, with the full area of the imaging panels being used.
It's quite a lot. From memory, maybe 30Kg? Which'd be a total of 60Kg for the flex.
Hmm, point. There are ways it can be done, I'm sure. I'm not a rope-access technician, but there are no shortage of them around to get the gen on it (about 200 employed in town, I estimate). If I had to do such a job myself, I'd chuck a kruzclem'd sling around the pole while I'm climbing up the ladder (possibly a second one on cows-tail #2 if the lamp-set fittings are likely to get in the way), then use that as my second security device while levering off the rain cap. Then whatever skyhook [1] I have on my short cows-tail over the rim of the pole to act as the security for the main job, go down a couple of steps to get on with whatever the job at hand is. Total time added to the job (since you've got to put on the harness etc in either case) probably not even 2 minutes. Years of practice and training on the other hand ... would probably put the grunt on the ladder into a higher pay bracket. Oh, sorry, fatal flaw. What do the onshore scaffolding companies call the roped access people? Offshore they're "dopes on ropes", though the animosity seems to have died down somewhat over the last decade. [1] A "skyhook" is a range of products reasonably easily available on the mountaineering scene. They're designed for providing "security" on horizontal traverses. Been around for about 45 years - if I recall properly, the first commercial ones were made by Royal Robbins after the publicity from the big wall routes on El Capitan. The mountaineering community have always found the building community's amusement about skyhooks ... amusing. See
Nothing news to me. Which is one of the reasons I always found it amusing to hear the scaffolders refer to the roped access technicians as "dopes on ropes".
That's no surprise. The climbing world seems to only have one size too, possibly the same size. But stretch in ropes, slings, etc is an accepted factor. As is wear and tear on the soft stuff and the need to replace ropes, slings, harness etc after even quite modest falls. The industrial uses I see at work require a maximum working lifetime of, IIRC,
6 weeks for any of the semi-fixed soft stuff, and a deal less for harnesses and any other gear that's in constant use. There's a constant consideration of forces and hazards in the business too, rather than the scaffolding/ industrial habit of just going massively over the top on the materials strength front. Consider - climbing ropes, harnesses etc all have a breaking strength of 1800 to 2000 kg, but by changing materials you could easily go up to the 5000kg of even small steel slings, so why not make them stronger? The answer is that at about 2000 kg people start to come apart. So, to use a rope of 5000 kg breaking strength would just guarantee that the falling person would hit the ground in several chunks. By restricting the breaking strength of the items used to less than the strength of the people, you ensure that really severe falls end with one item of kit breaking (absorbing some of the energy generated by the fall), then another item in the string fails, then another, and eventually a very sore person is hanging around in mid-air on one of the two rope, possibly screaming that they should have shuffled their nuts out from under the "knackertrapper" straps. Which is arguably a better outcome.
Are you talking about within-company HSE staff, or HSE inspectors employed by the government to make companies adhere to the law and their (company's) rules? I'm talking about the latter.
Andrew's figures are correct (BS 7671 Table 4H3A) but apply in the absence of more specific information from a manufacturer. So if MK say
5 kg, that's OK.5kg!! I would be surprised if that's safe. Never mind the electrical hazard - what if it falls on your head? :-)
I was watching the fair set up in Loughborough this year, and noticed a couple of interesting performances.
The guy on the Wild Mouse with no harness, walking on the tie-bars between the top tracks, bending down every so often to use a powered wrench at foot level.
The guy on the Reverse Bungee who seemed to have neglected to grab the retractable line before deploying one of the arms, so had to climb all the way to the very top in order to clip on.
Chris
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Alex Coleman saying something like:
Go out and buy some lamp flex and try pulling it enough to break it. You'd be surprised.
In message , Aidan Karley writes
I've never been thrilled by the behaviour of either. Obviously the corporate safety people have a duty to serve their company and protect it's management, but equally the ratio of "small people with a big hat" in the official HSE is high. If it was made a legal requirement that anyone being employed as a health and safety officer had to serve a full trade apprenticeship and at least 5 years on the tools, then things would improve. Most of the nonsense we get exposed to is a direct result of the total detachment between the HSE and real life.
A memorable image is a female HSE inspector with her hand over her mouth rushing to get away from all the fibreglass dust billowing around the site as a result of labourers throwing bales of it to one another. Once she got to a lovely clean bright office she was fine. Was the risk of lung damage through breathing fibreglass raised? No! Is it ever raised?
One job I was on I got tipped off that the ceiling that was being ripped down during the work may have contained asbestos. I contacted the HSE who simply didn't want to know and gave me the number for environmental health. I called them and they said they couldn't do anything about it now, but might look into it later. Next shift there was a site management witch-hunt for the contractor who had raised the risk of asbestos. The environmental officer had contacted them and they wanted to know who was responsible. As a result I had to keep quiet and work the job with these tiles being pulled down and smashed all around me, with nothing more than a paper dust mask that clearly said "not suitable for asbestos use" on it.
| >the lampshade is going to be carried at one point by only the two = copper=20 | >multi-stranded mains wires and their respective insulation. =20 | >
| >The heavier gauge protective outer sheath of the flex is not used in = the=20 | >UK ceiling pendants I have seen. | >
| >I don't know what the breaking strain is of those two little wires = but=20 | >it can't be all that much. |=20 | Go out and buy some lamp flex and try pulling it enough to break it. | You'd be surprised.
I rather think the plastic hooks in the ceiling rose will break first. The troll "Alex Coleman" is clearly a total moron.
On Fri, 15 Dec 2006 09:49:35 GMT someone who may be Alex Coleman wrote this:-
Only the bit between the ceiling rose and lamp holder. As has been said, the cable can carry far more then the masses stated in the Wiring Regulations or by the manufacturer.
In the fittings themselves one could only ignore the strain relief fittings if they were frictionless ideal pulleys in the Newtonian model. However, they are not frictionless ideal pulleys.
That's the nicest thing anyone has said to me all day.
One can lift a grown man off the ground with 3 core 3A flex wrapped around them. So 2 core not wrapped would carry at least 1/3 of that weight.
That weight rating will drop by a half again when youre standing atop a chair and wobble sideways, using the light as a support, since under sideways pull one core is in tension and the other in compression. When the tensioned core breaks, then the other core will take over, but with the same breaking strain, so you get 2 bites of the half cherry.
But the bigger risk is the lack of effective cordgrip in the lampholder, because a) if those wires come out you get left with bare live wires dangling instead of dead ones b) wires usually fail at the ends rather than the middle, for various reasons. c) loose or damaged copper at that point causes arcing, which can cause fire.
NT
One can lift a grown man off the ground with 3 core 3A flex wrapped around them. So 2 core not wrapped would carry at least 1/3 of that weight.
That weight rating will drop by a half again when youre standing atop a chair and wobble sideways, using the light as a support, since under sideways pull one core is in tension and the other in compression. When the tensioned core breaks, then the other core will take over, but with the same breaking strain, so you get 2 bites of the half cherry.
But the bigger risk is the lack of effective cordgrip in the lampholder, because a) if those wires come out you get left with bare live wires dangling instead of dead ones b) wires usually fail at the ends rather than the middle, for various reasons. c) loose or damaged copper at that point causes arcing, which can cause fire.
NT
Look at it this way: 5 kg is about 50 N and the combined CSA of the copper conductors is 1.5 mm^2. Ignoring any load borne by the insulation, the tensile stress in the conductors when supporting 5 kg is
50/1.5 MPa, i.e. ~33 MPa.Wikipedia [1] gives a typical yield strength for copper of 70 MPa and an ultimate tensile strength of 220 MPa. So why should anything fall on your head?
[1]
Isn't the notion of using live mains-carrying uninsulated copper wire (at the bulbholder terminals) to provide physical support just a bit more risky than it needs to be?
In other words, when the insulation is cut off one of the cores, some strands will also be cut. Mr Average will cut more than Mr Professional.
But the infamous Mr Half-Asleep will cut more strands off than Mr Average. Mr Half-Asleep might cut as many as a third of the strands and still think he has done a good job.
Then Mr Half-Asleep gives a simple twist to the remaining filaments and shoves them into the brass electrical conductor and screws it down.
Some of his filaments ....
... never go under the screw. ... get completely severed by over-tightening the screw. ... get damaged but not severed from the over-tightening. ... might get charred over time with use.
So the "bodge factor" (or "real life" if you prefer) may reduce the cross-sectional area of the copper by, well, who knows? We may end up with only a fraction of what we started with.
The same sort of thing happens all the time - on power pylons.
Yes. And with suitable design precautions taken when designing pylons and their wires. With only professionls allowed to mess with them.
OTOH I am talking about Joe Soap and domestic use.
Good old Joe may see a very heavy lampshade (intended for a standard lamp) and think it must also be ok on his home-installed lampholder. It could be too heavy. And in this case we are talking about potentially dangerous mains electricity.
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