In article ,
Robin writes:
On 14/01/2019 11:21, GB wrote:
On 14/01/2019 09:33, Robin wrote:

I thought hairpin style filaments weren't coiled - hence the tubular
design (up to at least 8 inches long IIRC) to make them long enough.

If you zoom in on the photo, you can see that this filament is coiled
quite loosely.

My terminological failu I grew up with "coiled" as shorthand for
coiled-coil, never having met a lamp that was a _single_ straight wire.
Indeed, ones like Daniele's which clearly has the filament passing up
and down were sometimes called "straight wire".

The squirrel cage filament lamps were not coiled, but had a
significantly longer filament than the lamp in the picture.

The double-ended tubular 30W and 60W filament lamps are single
coil to make the filament long enough. They are normally vacuum
tubes too, as any gas fill has a significant cooling effect
on such a long filament and it wouldn't get up to temperature.
To compensate for lack of gas fill, the filaments are underrun
to avoid the tungsten subliming too fast, but that also makes
them horribly inefficient, and they were still only rated 750
hours. Altogether, a bad idea.

--
Andrew Gabriel
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