Y adaptor for 2 bulbs in celing pendant lampholder?

I am in the UK.
I have got a lampsocket hanging from the ceiling in the middle of a room like this: http://www.toolstation.com/messages.html?closeUp '046
A single CFL is not bright enough so I want to hang two CFL lamps from one lampsocket.
Is it possible to get a "Y" adapter which plugs into the existing lampsocket and then allows me to plug in two CFLs?
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Yes, and here it is in all it's bakelite glory:
http://cgi.ebay.co.uk/EDISWAN-BIJOU-ADAPTOR-BAKELITE_W0QQitemZ190057703523QQihZ009QQcategoryZ72397QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
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On 10 Dec 2006 03:29:56 -0800, snipped-for-privacy@gglz.com wrote:

Yep those are the devices, not seen any on retail sale for donkeys years. Not sure if I still have a couple kicking about and the matching BC plugs so you could power, say your electric iron, from the lighting circuit.
I wouldn't advise using such a device though, much better to fit extra fittings in the right place(s) or up the wattage of your CFL.
--
Cheers snipped-for-privacy@howhill.com
Dave. pam is missing e-mail
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On Sun, 10 Dec 2006 13:45:17 +0000 (GMT) someone who may be "Dave

They are amusing if one wants to horrify a "safety" person.

Indeed.
--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
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David Hansen wrote:

To do that you need the full set, 2-way bulb adaptor & BC plug. Pvc flex should not be used in the BC plug, only rubber, since the flex sits directly on the hot bulb. The worst part of these things wasnt the adaptor/plug/cable, which was dodgy enough, but the fact that users would handle the top end of the fitted bulb holder, which in the later years of round pin wiring had frequently lost some if its (single) insulation, so you were fumbling with bare uninsulated mains wires that you couldnt see too much from below, with the bulb in your face, while standing on a chair or bed.
Maybe thats why iron beds declined in popularity, darwin effect....
NT
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I have never understood how it is still permitted to have a lampholder like in the OP http://www.toolstation.com/messages.html?closeUp '046
The way the lampholder is suspended depends on the grip of the actual screw-fittings on the bare wires.
If a moderately heavy lampshade is used then the whole thing seems to be asking for trouble.
Does the US have ceiling pendant lampholders as dodgy as this?
There is so much safety in electrical products these days that I just wonder how this sort of lampholder is not obliged to have a decent flex grip in it.
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writes

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.

Some excessive glass lampshades are just asking for trouble in any scenario.

No. ALL their wiring accessories are dodgy. :)
--
Clive Mitchell
http://www.bigclive.com
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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.
ISTR that a UK ceiling flex is about 6A (0.75 mm^2 and perhaps made up of 24 strands of 0.2mm diameter). For example: http://www.maplin.co.uk/Module.aspx?ModuleNoa98&C=SEO http://uk.farnell.com/jsp/endecaSearch/partDetail.jsp?SKUs0858
One link happens to show 3 cores but usually there will be only two cores holding a ceiling lampholder & shade.
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?

--
PS: groups widened to alt.engineering.electrical & sci.physics

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Max permitted weight supported by a two-conductor flex in UK Wiring Regs is:
0.5mm 2kg 0.75mm 3kg

--
Andrew Gabriel

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Andrew Gabriel wrote...

Indeed - from product specifications for MK ceiling roses and pendant sets:
"Suitable for fittings of up to 5kgs. Heavier fittings must be installed using independent support eg. ceiling hook."
Although MK pendant sets are supplied pre-fitted with "0.75mm2 two core circular cable", so there is some discrepancy with your quoted max permitted weight.
David
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David Lee wrote:

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.
--
Andy

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

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

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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.
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| > | > 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.
Yes. | | 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.
We don't have 100 lb lampshades, those are chandeliers with other means of support. As you correctly stated, you "don't know".
| | ISTR that a UK ceiling flex is about 6A (0.75 mm^2 and perhaps made up | of 24 strands of 0.2mm diameter). For example: | http://www.maplin.co.uk/Module.aspx?ModuleNo=6198&C=SEO | http://uk.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=730858 | | One link happens to show 3 cores but usually there will be only two | cores holding a ceiling lampholder & shade. | | What is the breaking strain of those two cores alone without any outer | sheathing?
About 100 lbs.
Is anyone able to test this and get a reading of the | required force?
Yes, hang on it with one of these:
http://www.humboldtmfg.com/images/products/h-4490.jpg
Why are you so concerned when there a several million in use?
What's black, charred and hangs from the ceiling?
An (Irish/Polish/Belgian/Chinese/Pakistani * ) electrician.
* choose ethnic group to suit your locality and create raucous laughter.
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It's quite a lot. From memory, maybe 30Kg? Which'd be a total of 60Kg for the flex.
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Ian Stirling wrote:

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
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Ian Stirling wrote:

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
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We were somewhere around Barstow, on the edge of the desert, when the
saying something like:

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

Dave

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| 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.
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