Carriage lighting

[mike57]

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.

 

[contrex]

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]

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.