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Old 11th Jun 2019, 10:37 pm   #61
emeritus
Dekatron
 
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
Posts: 5,316
Default Re: The lightbulb conspiracy

Getting back to the alleged "conspiracy" theme, I just dug out my GEC 1911 lighting catalogue. Something I hadn't noticed before is a series of graphs of light output versus time for "Robertson" carbon filament lamps. The "Life" axis ends at 800 hours, and seems to reflect the then-current British Standard. The graphs show that, at the 800 hour point, light output was still in excess of the British Standard end of life criterion. I know from another contemporary book about Robertson lamps that Robertson defined the end of life with reference to the "Smashing point", being the point at which the lamp had blackened so much that the light output was no longer adequate, and not the point at which the filament failed.

No corresponding information was supplied for their Tungsten lamps. Possibly as they were new technology at the time, a British Standard hadn't yet been established.

Regarding series operation of low wattage lamps, it appears that this was an absolute necessity at the time because it was not possible to manufacture Tungsten wire thin enough to make satisfactory low wattage bulbs for 200-250V operation. Striplight fittings for shops that took small or candle bulbs were available with multiple lampholders connected either in series for 200V operation or parallel for 25V to 120V operation. While "Robertson" tubular striplight Carbon lamps were available for up to 200-250V operation, "Osram" Tungsten tubular striplight lamps were only available for 25V.

GEC also supplied transformers and autotransformers for operating low voltage lamps from 200- 250V mains supplies, 50 Hz as standard, 25 to 100Hz to special order.

Lamps intended for series burning could be supplied in matched pairs.
Attached Files
File Type: pdf GEC 1911 low watts lamps .pdf (746.5 KB, 101 views)

Last edited by emeritus; 11th Jun 2019 at 10:54 pm.
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