> I also had the P700 (which
> is really the "correct" headlamp for a sidescreen car)
Oops, you're right, of course.
> they did
> seem brighter to me than the typical US-spec tungsten filament sealed-beam,
> and the light pattern was rather better.
It's possible the Lucas ones I compared had tired reflectors and/or bulbs. Are
you sure you were comparing to fresh sealed beams ? BTW, the Lucas bulbs also
use tungsten filaments as did all incandescent bulbs since about 1910. Even the
"halogen" bulbs use tungsten filaments.
The light output of all incandescent bulbs decreases with time. Depending on
manufacturing tolerances, the reduction in light output may be quite severe
before the filament burns out.
> Biggest problem I ever had with either lamp was that, here in the sometimes
> damp and often salty (in wintertime) Northeast, the reflectors were
> very prone to rusting away.
Which is exactly the reason they were illegal here ! With "sealed beam"
headlights (which were required by US law from about 1940 until 1984 or so) the
filament and reflector are both sealed in the same glass housing**, which is
partially evacuated and filled with an inert gas. This prevents any corrosion
of the reflector, which is usually just a very thin film of aluminum sprayed
onto the housing.
** There is one exception (AFAIK) to this. Cibie made the 'Bobi' for awhile
that had the reflector hermetically sealed separately from the filament. This
allowed them to use the standard H4 halogen bulbs in a DOT-approved "sealed
beam" design. Unfortunately they weren't very popular, perhaps because of the
price or perhaps because one of mine just "fell apart" one day. AFAIK they were
discontinued shortly after the DOT quit requiring sealed reflectors in 1984 or
so.
> Again, the
> light pattern is nothing to write home about, but they're definitely way
> brighter than the old tungsten lamps (if you can even find those
> outside of a
> flea market or eBay?).
The standard 6014 non-halogen bulbs seem to be readily available in stores
around here. They might not say 'Tungsten' in big letters, but tungsten is
what's in there. Tungsten has the highest melting point of any metal, and is
also strongest at the temperatures found in an incandescent light filament.
There have been a few tungsten alloys used (eg thorium, which is radioactive)
but not in car headlights.
Randall
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