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Old 9th Mar 2023, 5:18 pm   #21
Nickthedentist
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Default Re: Philips Bakelite BC-to-ES switched adaptor

I bet HKS has one in his workshop!
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Old 9th Mar 2023, 5:43 pm   #22
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Default Re: Philips Bakelite BC-to-ES switched adaptor

This has turned into a fascinating lesson for me. It would actually have been quite a novelty to have three levels of brightness at one lamp, back in the day. Nowadays we are all used to touch-sensitive table lamps with three brightness levels.

Twin filament bulbs would have been costly to make. And what do you do with it when one filament burns out, either scrap the bulb or soldier on with a single brightness lamp till the second filament fails too?

To add to the list of twin-filament bulbs, Freeplay released a wind-up torch in the late 1990s called the FPSL or “Freeplay Self-powered Lantern” which used a dual-filament 2.4 Xenon volt bulb rated at 300mA and 1,000mA, no doubt unobtainable now. The one I have still works.

It has occurred to me to check whether a conventional single-filament ES bulb will in fact be safe when inserted into this adaptor, as the second off-centre contact may foul the screw thread, depending on the shape of the insulation at the base of the cap.
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Old 9th Mar 2023, 6:36 pm   #23
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Default Re: Philips Bakelite BC-to-ES switched adaptor

For other than low priority domestic purposes, most twin filament bulbs should be replaced when one filament fails.

Examples, boat navigation lamps should be replaced when one filament fails, dont wait for the other one to fail as well.

Bulbs in railway signals should be replaced well before the first filament fails.

Operating theatre lamps should be replaced when the main filament fails, or preferably before then. Most such lamps, when discarded probably had the 12 volt filament almost unused.

Motor vehicles are not fully roadworthy without the tail light and the brake light working, so prompt replacement as soon as one filament fails is required. Main beam and dipped beam headlights likewise.

Domestically, most people hated buying light bulbs and I suspect that most 3 way light bulbs remained in use until both filaments failed.

Twin filament lamps were cheaper to manufacture than two individual bulbs.
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Old 9th Mar 2023, 7:07 pm   #24
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Default Re: Philips Bakelite BC-to-ES switched adaptor

Yes, good point.

I pulled out the inner lampholder section and checked with a normal ES bulb inserted that the secondary (line) contact didn’t touch the threaded (neutral) cap. It didn’t, but it comes quite close (to within 1mm) if the bulb is screwed down hard. I think I’m going to keep this adaptor as a curiosity, not to be used in anger.

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Old 10th Mar 2023, 12:18 am   #25
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Default Re: Philips Bakelite BC-to-ES switched adaptor

The Titanic used dual filament bulbs in its state rooms, though i can't find if they used BC or ES fittings. And that's from 1909!
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Old 10th Mar 2023, 1:26 am   #26
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Default Re: Philips Bakelite BC-to-ES switched adaptor

My copy of the GEC catalogue for 1911 shows what appears to be a BC base with three contacts, as one of a number of bases that can be supplied to special order. The catalogue itself does not list any lamps with this type of base.

Their only double filament lamp is a "Robertson" carbon filament lamp for marine use, with two filaments internally connected in parallel, to satisfy a Board of Trade regulation.
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Old 10th Mar 2023, 1:40 pm   #27
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Default Re: Philips Bakelite BC-to-ES switched adaptor

Interesting point, Kevin. It looks like dual-filament bulbs went the same way as the ship!
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Old 10th Mar 2023, 5:56 pm   #28
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Default Re: Philips Bakelite BC-to-ES switched adaptor

I'm pleased to know that I helped solve the mystery of the adaptor, though I have to admit I've never come across a dual-filament household light bulb in the UK. I first encountered one in use many years ago when I visited family relatives in Canada. One of my uncles, whom I was staying with, had such a lamp in his house. It was instantly fascinating to me, since I had never seen one before. That's why I remembered it vividly.

They seem to have disappeared pretty much without trace in the UK. Your adaptor is the only piece of evidence I've come across that shows they were marketed here. We do of course have dual-filament automotive bulbs in the UK - it seems the idea of a twin filament bulb goes back as far as the 1880s.

In the USA and Canada, dual-filament household light bulbs - commonly called 3 way bulbs - are still widely available in hardware stores, as are the matching lampholders. Incandescent bulbs for household lighting are banned from sale in the UK so you won't be able to buy one here. However, I noticed there are energy-saving equivalents on sale as well. Maybe we should persuade the manufacturers to produce 230-240v versions

Some LED and incandescent examples from the retailer Canadian Tire (yes, that's how they spell tyre. Originally they sold car tyres but diversified into all sorts of hardware)
https://www.canadiantire.ca/en/searc...3%20way%20bulb

The lampholder : https://www.leviton.com/en/products/7090-BR

Archived page showing a Philips Trilight energy-saving compact fluorescent bulb with twin spiral tubes. That's fun!
https://web.archive.org/web/20130308...t-white/917987

The Home Depot website now appears to be geo-blocked from the UK - I get 403 Forbidden when trying to access it. It used to work. I've attached the images in case the links go dead in the future. This is actually a neat illustration of the progress of technology. Original incandescent 50/100/150W, Compact fluorescent 11/23/34W and LED 6/12/19W power consumption.
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Old 11th Mar 2023, 11:55 am   #29
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Default Re: Philips Bakelite BC-to-ES switched adaptor

3 way bulbs were at least somewhat used and available in The Netherlands. My father had a small lighting, appliances and materials store and always stocked one or two during the 1990's and early this century.
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Old 11th Mar 2023, 10:06 pm   #30
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Default Re: Philips Bakelite BC-to-ES switched adaptor

Not a technology I'd seen in mains applications.

I do know of a low voltage apllication where two separate lamps were used with different intensities / power outputs in the same cluster but different pockets. If the lower power one failed (that was in use for much more time) then the control system detected this and ran the higher power lamp, dimmed while giving a warning to the operator that a lamp had failed.
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Old 12th Mar 2023, 12:17 am   #31
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Default Re: Philips Bakelite BC-to-ES switched adaptor

Quote:
Originally Posted by Maarten View Post
3 way bulbs were at least somewhat used and available in The Netherlands…
Well, I’m a Dutchman…! (sorry) but that makes sense in that this adaptor/lampholder is branded “Philips” so there’s an obvious Netherlands connection. I wonder if we have any members in the Low Countries who might have a bulb, or know where one could be obtained? Clearly they would have been rated for 230 volt operation.

With reference to earlier posts that mentioned hospital operating theatre lights, I was a Hospital Engineer for 30 years and the only operating lights I encountered were 24 volt, operating from a float-charged battery of NiFe cells. In the event of a mains failure, the room lights went out (for 8 seconds or so until the standby generators started and took load) but the operating lamp was unaffected.
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Old 16th Mar 2023, 10:58 am   #32
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Default Re: Philips Bakelite BC-to-ES switched adaptor

3 way light bulbs were almost always used in lamp holders or adapters with a built in four position switch.

As a far less common alternative, lamp holders were available without any built in switch, for control by a wall switch.
These had three terminals, common neutral, live to smaller filament, and live to larger filament, plus a protective earth if needed.

Very few electricians seemed able to understand how these wall switches should be wired.
Option one was a four position rotary switch to give a choice of OFF, A, B, or A+B.
One switch could control a number of lamps , limited only by the fuse size and switch rating. A common error was mixing up the two live feeds to the lamps

Option two was a pair of standard single pole switches, one for all the smaller filaments and one for the all the larger filaments, turn on both switches for full light. A common error was to use a two way switch such that the smaller or larger filaments could be used, but not both.
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Old 21st Mar 2023, 6:39 pm   #33
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Default Re: Philips Bakelite BC-to-ES switched adaptor

Philips "3 light lamps" are listed on page 9 of this 1964 catalogue.
http://http://www.lamptech.co.uk/Documents/Catalogues/Philips%20-%20Catalogue%20-%201964%20UK.pdf
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Old 21st Mar 2023, 7:04 pm   #34
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Default Re: Philips Bakelite BC-to-ES switched adaptor

Thanks BG, that is really interesting. They were, however, quite expensive in their day. I remember ‘ordinary’ light bulbs costing under two shillings retail in the 1960s, so a dual filament bulb at a wholesale price of over six shillings plus P.T. would have been an expensive luxury item to buy. Perhaps that limited demand, together with the fact that 160 watts is very bright for a table or standard lamp.

Page 203 (sheet D89) also shows a tall standard lamp fitted with a 3-light bulb.
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Old 22nd Mar 2023, 6:23 pm   #35
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Default Re: Philips Bakelite BC-to-ES switched adaptor

There WAS a dual-filament domestic lamp available as an 'extended-life' gimmick.
It fitted a normal BC holder, and when the first filament broke, you took it out, turned the outer sleeve of the cap to the second position, and put it back in.
There were three contacts on the lamp base; one of normal length, and two shorter ones, with an insulating gap.
I suspect it didn't catch on, because I've seen exactly ONE of them, and that was a long time ago.
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Old 24th Mar 2023, 10:06 am   #36
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Default Re: Philips Bakelite BC-to-ES switched adaptor

Here is a data sheet for twin filament railway signal lamps.
Lumax, part of the CEAG group are the most well known maker of these lamps, but other brands exist.

https://www.rivval.com/Product_Folde...35%20Lamps.pdf

Railway signals often use a 110 volt supply with a transformer for each lamp.
Failure of the main filament automatically brings into use the auxiliary filament.
Failure of both filaments or of the power supply automatically causes the preceding signal to show a red stop light.
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Old 24th Mar 2023, 12:27 pm   #37
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Default Re: Philips Bakelite BC-to-ES switched adaptor

Quote:
Originally Posted by Brigham View Post
There WAS a dual-filament domestic lamp available as an 'extended-life' gimmick.
It fitted a normal BC holder, and when the first filament broke, you took it out, turned the outer sleeve of the cap to the second position, and put it back in.
There were three contacts on the lamp base; one of normal length, and two shorter ones, with an insulating gap.
I suspect it didn't catch on, because I've seen exactly ONE of them, and that was a long time ago.

That BC lamp base seems to be similar to the lamp base depicted at the centre of the bottom line of the second attachment to post #26.

Last edited by emeritus; 24th Mar 2023 at 12:28 pm. Reason: typo
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