In article ,
Harry Bloomfield writes:
After serious thinking Johny B Good wrote :
I'm afraid to say this, but that last paragraph is basically a load
of bull****. Regardless of 'poor quality of early filaments' the
design criteria is still affected by the same physical laws that
determine the life versus luminous efficacy trade offs made with
today's high quality filaments.

Is exactly right!

There has been little if any improvement or development in lamps and
filaments, since the 1950's maybe even back to the 1920's.

That's not true.

There have been deployments of better gas fills, which reduce
filament evaporation, and reduce heat loss by convection cooling
of the filament.

Tungsten Halogen lamp.

Move to low voltage filament lamps (more efficient).

Infra-red reflective coatings to reflect the IR emission back
onto the filament.

Most recently, there has been the development of tungsten filament
surfaces with an interference pattern to prevent emission of IR
wavelengths. (This has been demonstrated, but abandoned due to
many countries banning filament lamps, rather than banning lamps
below certain efficiences).


The improved quality of filament just allows for an improved luminous
efficacy for a given lamp life (1000 hours being the standard lamp
life arrived at all those years ago as offering the best TCO between
the electricity and lamp replacement costs).

They were quoting 1.00 hours back in the 1950's and coiled coils.

Coiled-coil is just to get around that 240V is a long way from
the most efficient filament lamp voltage for lamps below a few
hundred watts - it needs the filament to be so thin it has too much
surface area, which the coiled-coil counteracts to some extent.
(The most efficient design voltage for 100W filament lamp is
about 55V.)

My experience suggests life is reduced by much more than 1/2 the life.
My problems with the oven lamps is not the first time I have been sold
220 -240v lamps and have them need to be replaced within a very short
time.

I would expect oven lamps to typically last for several years in a
domestic oven, rather than just a week or so.

Oven lamps are heavily under-run. If yours have short life, it's
for some other reason - vibration of a fan or slamming the oven door,
stress on the lamp, overheating, etc.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]