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Why were trains with tungsten lighting still built so late on?

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AY1975

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Following on from the thread on why slam-door trains were still built so late on at https://www.railforums.co.uk/threads/why-were-slam-door-trains-still-built-so-late-on.172064/, does anyone know why BR continued to build trains with tungsten interior lighting for so long after it had started to build some trains with fluorescent lighting?

For example, loco-hauled Mark 1s started to be built with fluorescent lighting from about 1959 onwards, albeit only in saloon coaches, and some DMUs and EMUs such as the Class 123s, 124s and 309s were built with fluorescent lighting in the saloons (not in the compartments, though). On the other hand, Southern Region 4-CIGs and 4-VEPs were still being built with tungsten lighting into the early 1970s!
 
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AndrewE

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Incandescent (filament) bulbs are robust, especially heavy-duty ones with thicker filaments and last even longer if run below their official voltage. I don't know whether fluorescent tubes were available in "tractionised" versions...
When did solid state inverters come in? Lots of BR standard stock had motor-alternator sets for generating AC.
 

Journeyman

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I think it was just the sheer number of tungsten-lit vehicles already in existence that led the Southern to continue using this form of lighting so late on. Lighting operated at 70v on the SR, which I think was unique, so bulbs were manufactured specially in large quantities.
 

DerekC

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Incandescent (filament) bulbs are robust, especially heavy-duty ones with thicker filaments and last even longer if run below their official voltage. I don't know whether fluorescent tubes were available in "tractionised" versions...
When did solid state inverters come in? Lots of BR standard stock had motor-alternator sets for generating AC.

I was trying to remember when solid-state inverters came in. I think power transistors were widely available in the mid 1960s, which made an
inverter using a simple transistor oscillator driving a step-up transformer feasible. They wouldn't have been very efficient and probably produced lots of harmonics but probably nobody cared too much.
 

Bletchleyite

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Maybe a slight aside, but the last trains with tungsten lighting were built in the early 2000s - the Pendolinos had tungsten halogens in both the central row of spots and the reading lamps. These have now been replaced with LEDs. However, XC Voyagers and I think 222s still have tungsten halogens in those fittings.
 

Taunton

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I think it was just the sheer number of tungsten-lit vehicles already in existence that led the Southern to continue using this form of lighting so late on. Lighting operated at 70v on the SR, which I think was unique, so bulbs were manufactured specially in large quantities.
I think that until the 4-CIG etc came along, lighting was at full 750v (lights were daisy-chained so the bulbs were in series), so very simplistic switchgear. And I have to say that blacked out saloons of the Mk 2/3 type were far less prevalent on older stock.

I regret to report inadvertently smashing a protruding tungsten bulb in a 4-CEP (pre-rebuild) one morning at Charing Cross, swinging a bag up with great aplomb onto the rack in a heroic curving movement, to impress a girl. We were off to Paris for a weekend, hovercraft from Dover, and it had rather got to me! But why did the designer put them so close to the racks. Someone told me that because of the full voltage it needed a proper CMEE fitter to change the bulbs in those.
 

big all

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I think that until the 4-CIG etc came along, lighting was at full 750v (lights were daisy-chained so the bulbs were in series), so very simplistic switchgear. And I have to say that blacked out saloons of the Mk 2/3 type were far less prevalent on older stock.

I regret to report inadvertently smashing a protruding tungsten bulb in a 4-CEP (pre-rebuild) one morning at Charing Cross, swinging a bag up with great aplomb onto the rack in a heroic curving movement, to impress a girl. We were off to Paris for a weekend, hovercraft from Dover, and it had rather got to me! But why did the designer put them so close to the racks. Someone told me that because of the full voltage it needed a proper CMEE fitter to change the bulbs in those.
Motor alternators started with 1951 stock: EPBs, HAPs and Kent Coasters; before that all circuits were line voltage, apart from control circuits, which were reduced to 70volts by a Potentiometer (on SUBs, at least).
 
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yorksrob

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Surely the real question should be why they ever switched from lovely, gentle, warm tungsten lighting, to hideous, glaring flourescent tubes in the first place.
 

Bletchleyite

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Surely the real question should be why they ever switched from lovely, gentle, warm tungsten lighting, to hideous, glaring flourescent tubes in the first place.

It was the trend in the 80s. What I really don't get is why now LEDs can create a lovely warm and cosy feel TOCs insist on specifying stark bright white.
 

yorksrob

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It was the trend in the 80s. What I really don't get is why now LEDs can create a lovely warm and cosy feel TOCs insist on specifying stark bright white.

True on both counts. I'm sure they can even get better coloured flourescent tubes than some of the ones they use.

Travelling at night in a tungsten lit carriage is a pleasure.
 

PaxVobiscum

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True on both counts. I'm sure they can even get better coloured flourescent tubes than some of the ones they use.

I’m not acquainted with this technology - does it use ground wheat as a coating on the glass tubes rather than one of the usual phosphor compounds? ;)

I’m just being silly.
 

AY1975

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It was the trend in the 80s.

Yes, and I would guess that by that time, with vandalism, anti-social behaviour and violent crime on the increase, a lot of passengers felt safer in a more brightly lit environment.
 

Bletchleyite

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Yes, and I would guess that by that time, with vandalism, anti-social behaviour and violent crime on the increase, a lot of passengers felt safer in a more brightly lit environment.

Many still take that view now. There's as many people who call the Pendolino "cosy and subdued" as call it "dull and dowdy" or even "shadowy".
 

AY1975

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Also, do you know why fluorescent lighting was initially only considered suitable for saloons, not for compartments?

My guess would be that it was thought that passengers travelling in compartments preferred to be able to adjust the level of lighting according to their own personal preference (and whether they wanted to read or sleep). Because of this, side corridor compartments usually had reading lamps and a dim/bright switch for the ceiling lights.

Mark 2a/b/c/d Corridor and Brake Corridor Firsts had fluorescent lighting, but they had a dim/bright switch that turned the fluorescent light off and put a dim spotlight on instead. This arrangement is still often found in side corridor coaches in mainland Europe (and in some older coaches, such as in the Czech Republic, the reading lights only work when the fluorescent light is turned off and the spotlight on).
 
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