Carriage lighting

mike57 · 2026-10-15T07:12:18+0100

The exile said:
it hit the first truly 750V section true - or an urban myth

Probably exaggerated, assuming bulbs were 70v in a series string there would have been 9 in a string, so would probably end up seeing around 80v, they would certainly burn bright, wouldn't last (as) long, and any close to the end of their life would blow, protecting the rest of the string. Memories of the 4SUBS were that the lighting was quite yellow = lower filament temperature = longer life, a bit like the 'rough service' lamps we used to have for things like inspection lights.

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contrex · 2026-10-15T08:43:43+0100

The exile said:
Is the story about the 4-SUB that ventured beyond the lower-voltage inner suburban lines (? Further out than Woking) only to have every bulb blow when it hit the first truly 750V section true - or an urban myth?

They were certainly forbidden, along with BILs and HALs I guess, to venture beyond Pirbright Junction onto the 1967 Bournemouth electrification unless the lighting and heating circuits had been isolated by a member of the CM&EE's staff. This might happen for a special trip to Eastleigh Works. The same applied to the Kent Coast scheme, which was 750v from the start. SUBs didn't go on that part of the SR much but a 4-SUB railtour to an Ashford open day in August 1982 had to have the lighting fuses removed for the Kent Coast section because of the higher voltage. The heating was isolated at that time of year. 1930s mainline stock such as COR, PUL/PAN etc were OK because their lighting (and heating I think) came from motor-generators. I don't think all the bulbs would have blown at once from a 13% overvoltage (750v vs 660v) but their lives would probably have been shortened somewhat. The bulbs were wired in a number of series chains, so that one failure/removal* would not darken the whole train. If one bulb failed, all the bulbs in that particular series chain would go out.

* E.g. by naughty schoolboys.

The exile · 2026-10-15T08:56:28+0100

contrex said:
They were certainly forbidden, along with BILs and HALs I guess, to venture beyond Pirbright Junction onto the 1967 Bournemouth electrification unless the lighting and heating circuits had been isolated by a member of the CM&EE's staff. This might happen for a special trip to Eastleigh Works. The same applied to the Kent Coast scheme, which was 750v from the start. SUBs didn't go on that part of the SR much but a 4-SUB railtour to an Ashford open day in August 1982 had to have the lighting fuses removed for the Kent Coast section because of the higher voltage. The heating was isolated at that time of year. 1930s mainline stock such as COR, PUL/PAN etc were OK because their lighting (and heating I think) came from motor-generators. I don't think all the bulbs would have blown at once from a 13% overvoltage (750v vs 660v) but their lives would probably have been shortened somewhat. The bulbs were wired in a number of series chains, so that one failure/removal* would not darken the whole train. If one bulb failed, all the bulbs in that particular series chain would go out.

* E.g. by naughty schoolboys.

No doubt that is the source of the urban myth.

contrex · 2026-10-15T14:28:56+0100

The exile said:
No doubt that is the source of the urban myth.

It might be exciting to see and hear. I did once read that now old fashioned incandescent filament 240v bulbs could fail explosively if connected between phases of a 415v three-phase supply.

6PAN · 2026-10-15T18:55:28+0100

contrex said:
They were certainly forbidden, along with BILs and HALs I guess, to venture beyond Pirbright Junction onto the 1967 Bournemouth electrification unless the lighting and heating circuits had been isolated by a member of the CM&EE's staff. This might happen for a special trip to Eastleigh Works. The same applied to the Kent Coast scheme, which was 750v from the start. SUBs didn't go on that part of the SR much but a 4-SUB railtour to an Ashford open day in August 1982 had to have the lighting fuses removed for the Kent Coast section because of the higher voltage. The heating was isolated at that time of year. 1930s mainline stock such as COR, PUL/PAN etc were OK because their lighting (and heating I think) came from motor-generators. I don't think all the bulbs would have blown at once from a 13% overvoltage (750v vs 660v) but their lives would probably have been shortened somewhat. The bulbs were wired in a number of series chains, so that one failure/removal* would not darken the whole train. If one bulb failed, all the bulbs in that particular series chain would go out.

* E.g. by naughty schoolboys.

Yes, those naughty schoolboys. One of my classmates used to delight in taking the 70v bulbs from the train on the way to school and replacing the 240v bulbs in the classroom with them. When the teacher switched the lights on there was a spectacular but brief event!

Also back on topic I do remember the lights in 2BIL/HAL units becoming very dim when a 12 car CIG/BIG train accelerated away from the adjacent platform at Lewes.

contrex · 2026-10-15T19:04:34+0100

6PAN said:
Also back on topic I do remember the lights in 2BIL/HAL units becoming very dim when a 12 car CIG/BIG train accelerated away from the adjacent platform at Lewes.

They used to dim for a longish moment in SUBs when the driver started away from a station. I knew a little gentleman at Alleyn's School who was had up in court for vandalising a SUB in 1964, including hurling seat cushions out of the windows.

43096 · 2026-10-15T19:12:19+0100

Tetragon213 said:
Iirc, in heritage the lights are only used when going into tunnels, or when it gets genuinely dark; usually, it's to protect the batteries. I believe some coaches also have manual switches on them which are completely independent of the guard's actions, e.g. the buffet coach lighting.

That doesn’t apply to more sophisticated preserved stock i.e. Mark 3s.

edwin_m · 2026-10-15T21:24:00+0100

43096 said:
That doesn’t apply to more sophisticated preserved stock i.e. Mark 3s.

Mk2 aircons and Mk3s get their power for lighting (and everything else) from the train supply which is jumpered through from the locomotive or power car. I assume they also have a battery for emergency lighting when no supply is available.

s491 · 2026-10-16T06:35:50+0100

edwin_m said:
Mk2 aircons and Mk3s get their power for lighting (and everything else) from the train supply which is jumpered through from the locomotive or power car. I assume they also have a battery for emergency lighting when no supply is available.

All UK coaches have batteries, its just how they're charged. Mk2 air con, Mk3, Mk4 and Mk5 batteries are charged via the train supply and battery charger, thereby providing emergency lighting for several hours in the case where no supply is available. So you can't go hauling them around all day with no heat locos....... (You'll also be in some trouble with Wheel Slide Protection on Mk3 coaches too as that's powered from the batteries)

Route115? · 2026-10-16T06:56:10+0100

I remember in BR days that the lights on Waterloo & City line stock dimmed when the train accelerated. I presume that they were fed directly whereas LT trains used a motor alternator rectifier which would supply a much more constant voltage.

I know that various types of LT stock used to have a couple of battery fed tungsten bulbs - the rest were florescent tubes - which were the only ones that stayed on when the train went over gaps in the conductor rail, With the 1973 stock on the Piccadilly line half the lights would go out in turn - I presume that one half was fed from either end of the train.

Dstock7080 · 2026-10-16T08:55:19+0100

Route115? said:
I presume that they were fed directly whereas LT trains used a motor alternator rectifier which would supply a much more constant voltage.

District Q Stock were the last with traction feed bulbs, withdrawn 1971 (although a few remained in service Stock use, which I trained upon.)
District CO/CP Stock had 50v generator fed bulbs but from a bus-line between two motor cars, thus keeping the lights on almost continuously with the switch on.

Route115? said:
I know that various types of LT stock used to have a couple of battery fed tungsten bulbs - the rest were florescent tubes - which were the only ones that stayed on when the train went over gaps in the conductor rail, With the 1973 stock on the Piccadilly line half the lights would go out in turn - I presume that one half was fed from either end of the train.

Half lights except the two emergency battery lights on one side.

Carriage lighting

mike57

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contrex

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The exile

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