Phil Hobbs wrote:

On 10/11/2012 07:18 PM, Dave Plowman (News) wrote:
In ,
Jeff wrote:
The lobby and foyer lights were mounted on the ceiling, pointing down.
One would think that there would be plenty of hot air accumulating
near the ceiling, but that wasn't the case. That's where the fan
ducts were located which helped to cool the lights. Few of those
lights ever burned out.

The marquee lamps were mounted on a vertical structure, with the lamps
pointed horizontally.

Vertical mounting for a GLS lamp seems to give a better life than other
orientations. A rough service type may have had a better life in this
application.


The filament temperature goes up more slowly than the ambient, since
it's radiatively cooled, but a rise of, say, 50 degrees would probably
have a significant effect on bulb life.


The projector bulbs in the old RCA TP66 film chain were mounted in a
vertical line. If you used the bottom lamp, and let it switch the to
spare on top, they had a short life of a little over 20 hours. If you
ran the top lamp, with the spare at the bottom, the life was over five
times longer. The projector used a motorized track, with a relay in
series with the filament. When the filament opened, the relay dropped
out and turned on the motor. In either position, it would run to look
for the other bulb when the one in use failed. I would pull the bad
lamp and move the good lamp to the top at the next film change, then put
the new lamp in the bottom socket. I averaged over 130 hours per lamp,
that way.