Re: Slightly OT. Heat and a Bench Light ...

Arfa Daily wrote:


"Baron" <baron.nospam@xxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:g4lfhd$75u$1@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
Arfa Daily Inscribed thus:

For twenty odd years, I have had the same Terry's Anglepoise bench
lamp in service. I have always used perfectly normal 60 watt
incandescent lamps in it, without any problem at all. Although the
metal shade used to get quite warm, it was never enough to actually
burn you when your forehead accidentally connected with it.

Recently, the light bulbs I've been seeing and buying, seem to have
reduced in size from the old 'tennis ball' size, to something closer
to a snooker or pool ball (but not as small as the established 'golf
ball' types often used in multibranch ceiling lights and light / fan
fittings.)

I have noticed that these new smaller bulbs run a whole quantum leap
hotter than the older larger size, and they hot up the shade on the
bench light until it is unbearably hot to touch. Today, I left the
workshop for a while, and when I came back, the air was full of that
'fishy' sort of smell you get when something like a wall socket or
the plug that's in it, is burning. A hunt around for the source,
brought me to the bench lamp, which was still alight. When I moved
it, it went off. When it had cooled down a bit, I took the bulb out
(a UK bi-pad bayonet cap rather than a U.S. edison screw type) and I
was horrified to see that one of the solder pads had just about
burnt away completely, and the black insulation material in the base
had started to burn as well. Fortunately, the brass lampholder was
undamaged.

Don't count on the lampholder being undamaged ! The springs in the
holder that apply pressure to the contact pads on the bulb, weaken
with
both age and heat. It would be wise to replace the lamp holder.

So, has anyone else noticed how hot these smaller bulbs run ? Are we
talking dangerous here if they are used in any fitting where they
hang downwards ? Any suggestions as to why there is such a large
increase in temperature ? Yes, I can see that the glass envelope is
closer to the filament, and that it has somewhat less surface area
to radiate the heat away from, but I'm not sure that either of those
are enough to account for just how much hotter they seem to run. And
why had one pad burnt away?Anything to do with the solder being
lead-free and less malleable than before, reducing the spring loaded
contact area maybe ?

Yes the smaller glass envelope does increase the heat considerably !
The bulb produces a little more light as well. I don't know that
being lead free makes a lot of difference, the heat sure does though
!

A bit worrying as I'm sure that there will be many situations where
a fitting that has previously been quite happy with a 60 watt bulb
in it, will now overheat, with possibly catastrophic consequences
...

Arfa

Yes I agree, overheating is a problem. I enlarged the vent holes on
my
desk lamp for that reason. I used a nibbling tool that I bought at
Radio Shack when I was in the USA a few years ago.

--
Best Reagrds:
Baron.

The lampholder is ok. Oddly enough, I renewed the cable to the lamp a
few weeks ago, as it had gone intermittent at one of the bend loops,

Yes ! The middle one. The original cable was fabric woven sheath over
rubber. I replaced it with "electric iron" cable but that didn't last
as long as the original one. I've now got a modern plastic insulated
cable in there. Its much thinner and more flexible. I used cambric
spaghetti over the wires at the bulb holder end just in case the heat
damaged the plastic insulation.

and as the holder was original, and looking a little worse for wear, I
put in a new one, and a new pressel switch as well, which had failed
and been bypassed
long ago ... :-)

Arfa

That little push on push off switch went a very long time ago ! There
is just the hole now, adding to the ventilation !

--
Best Regards:
Baron.
.

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