Dave Liquorice wrote:

How do you get the rain cap off if you "can't work" without being clipped
on?

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
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.

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:

At end of the day, with or without strain relief hooks, the weight of
the lampshade is going to be carried at one point by only the two copper
multi-stranded mains wires and their respective insulation.

The heavier gauge protective outer sheath of the flex is not used in the
UK ceiling pendants I have seen.

I don't know what the breaking strain is of those two little wires but
it can't be all that much.

Go out and buy some lamp flex and try pulling it enough to break it.
You'd be surprised.
--

Dave

In message valid,
Aidan Karley lid
writes
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.

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.

--
Clive Mitchell
Death by electrocution is NOT "heart failure"!
http://www.bigclive.com

"Grimly Curmudgeon" wrote in message news | 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:
|
| At end of the day, with or without strain relief hooks, the weight of
| the lampshade is going to be carried at one point by only the two copper
| multi-stranded mains wires and their respective insulation.
|
| The heavier gauge protective outer sheath of the flex is not used in the
| UK ceiling pendants I have seen.
|
| I don't know what the breaking strain is of those two little wires but
| it can't be all that much.
|
| 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:-

At end of the day, with or without strain relief hooks, the weight of
the lampshade is going to be carried at one point by only the two copper
multi-stranded mains wires and their respective insulation.

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.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On 15 Dec 2006, Sorcerer wrote:


"Grimly Curmudgeon" wrote in
message news | 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:
|
| At end of the day, with or without strain relief hooks, the
| weight of

| the lampshade is going to be carried at one point by only the two
copper
| multi-stranded mains wires and their respective insulation.
|
| The heavier gauge protective outer sheath of the flex is not used
| in
the
| UK ceiling pendants I have seen.
|
| I don't know what the breaking strain is of those two little
| wires
but
| it can't be all that much.
|
| 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.


That's the nicest thing anyone has said to me all day.

Ian Stirling wrote:
In sci.engr.lighting Alex Coleman wrote:
On 10 Dec 2006, Clive Mitchell wrote:
In sci.engr.lighting and uk.d-i-y Alex writes:

The way the lampholder is suspended depends on the grip of the
actual screw-fittings on the bare wires!

It's not just relying on the wire being clamped. When assembled
correctly the wires are looped over strain relief hooks which
remove a lot of the pull force.

At end of the day, with or without strain relief hooks, the weight of
the lampshade is going to be carried at one point by only the two copper
multi-stranded mains wires and their respective insulation.

What is the breaking strain of those two cores alone without any outer
sheathing? Is anyone able to test this and get a reading of the
required force?

It's quite a lot.
From memory, maybe 30Kg?
Which'd be a total of 60Kg for the flex.

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

Ian Stirling wrote:
In sci.engr.lighting Alex Coleman wrote:
On 10 Dec 2006, Clive Mitchell wrote:
In sci.engr.lighting and uk.d-i-y Alex writes:

The way the lampholder is suspended depends on the grip of the
actual screw-fittings on the bare wires!

It's not just relying on the wire being clamped. When assembled
correctly the wires are looped over strain relief hooks which
remove a lot of the pull force.

At end of the day, with or without strain relief hooks, the weight of
the lampshade is going to be carried at one point by only the two copper
multi-stranded mains wires and their respective insulation.

What is the breaking strain of those two cores alone without any outer
sheathing? Is anyone able to test this and get a reading of the
required force?

It's quite a lot.
From memory, maybe 30Kg?
Which'd be a total of 60Kg for the flex.

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

Alex Coleman wrote:

5kg!! I would be surprised if that's safe. Never mind the electrical
hazard - what if it falls on your head? :-)

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] http://en.wikipedia.org/wiki/Tensile_strength
--
Andy

In article , Clive Mitchell wrote:
I've never been thrilled by the behaviour of either.

I refer the commentator to my previous description of "Paper
Tigers".

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.

Shoot the messenger. Sounds about normal.

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.

Yep, done the cash-in-hand work for asbestos demolition companies
too. It's called exploitation. The Nazis did it a couple of generations ago
; 10 generations ago Britain and Britons were getting rich on exploitation
in the slave trade ; 100 generations ago pharaohs were exploiting the
toilers in the fields ; 1000 generations ago, Cro-magnons were probably
just about finishing off the Neanderthals ; 10000 generations ago the big
Homo habilis (or Homo heidelbergensis, I can't remember this week's names)
was threatening the little Hom.h with a club to take the day's hard-won
food off him.

--
Aidan
Aberdeen, Scotland
Written at Sun, 17 Dec 2006 22:32 GMT, but posted later.

On 16 Dec 2006, David Hansen wrote:

On Fri, 15 Dec 2006 09:49:35 GMT someone who may be Alex Coleman
wrote this:-

At end of the day, with or without strain relief hooks, the weight
of the lampshade is going to be carried at one point by only the
two copper multi-stranded mains wires and their respective
insulation.

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.




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?

On 16 Dec 2006, Andy Wade wrote:

Alex Coleman wrote:

5kg!! I would be surprised if that's safe. Never mind the
electrical hazard - what if it falls on your head? :-)

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] http://en.wikipedia.org/wiki/Tensile_strength


What about the "bodge factor"?

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.

On Wed, 20 Dec 2006 10:45:31 GMT, Alex Coleman
wrote:

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?

The same sort of thing happens all the time - on power pylons.

--
Frank Erskine

On Wed, 20 Dec 2006 10:45:31 GMT, Alex Coleman
wrote:

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?

On 20 Dec 2006, Frank Erskine wrote:

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.

Alex Coleman wrote:

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.

Much ado about nothing where most of us are concerned.

You'll never prevent stupidity though you sound like
someone who should not be attempting DIY.

Alex Coleman wrote:

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.


On 20 Dec 2006, unsettled wrote:

Much ado about nothing where most of us are concerned.

You'll never prevent stupidity though you sound like
someone who should not be attempting DIY.



Joe Soap is the character. I am real. Don't mix us up!