Thomas P. Carswell
1887 Presented a Paper on lighting trains by electricity (incandescent lamps, instead of gas or oil), entitled 'On the Automatic Electrical Lighting of Trains' before the Philosophical Society of Glasgow. An abstract, with drawings was presented in Engineering 1887/09/23. 'A centre or third rail has been laid down from one end
of the tunnel to the other, but is omitted in the open air. ....' A spring-loaded steel wheel was provided at each end of the carriage to make contact with the centre rail. '.... The current of electricity for lighting the lamps is derived from a large Crompton compound-wound self-regulating dynamo, having a potential at the terminals of 110
volts. This dynamo is always kept running, the positive
lead being connected to the centre rail, and the negative
lead to the ordinary rails. It is driven by the same engine
as is used for lighting Queen-street high level station. .... It will be seen that by this system the train, or rather
each carriage, is.lighted and extinguished on entering or
leaving the tunnel—automatically, as it were. There are
no connections between the carriages, so that the train can
be broken up or shunted as usual, while the light is maintained whether the train is in motion or at a stand.
During the New Year holidays some of the trains were
running with only one carriage fitted, while others had
six or eight fitted and the remainder not.
During the passage of these trains through the tunnel
the speed of the dynamo was nearly constant, and their
presence in the circuit could only be detected by a slight
hissing noise at the commutator brushes, and faint sparking, if any. This system has now been in use four
months, and two trains have been running all this time,
only being off one day weekly to be cleaned. The number
of lamps in the two trains was on an average 60 ; and, in
the four months’ lighting, three of them have had to be
renewed. Two of the three were broken maliciously, the
outside globes having been broken also, while in the
other the carbon filament gave way, having burned
100 hours.
'... In order to prevent the rusting of the centre rail, and to
keep it clean so as to make good contact, a steel wire
brush is fixed on one carriage in each train. It is found
thatthe brush makes better contact and gives a steadier
light than the pulley, but, owing to the friction, the tear
and wear would be too great to adopt it entirely. ....
Since this paper was read, eight trains—or, in all, 74
carriages—have been fitted and are running daily. Taking the running of these trains for six months, the total
number of lamp hours is 39,642. During this time it has
been necessary to replace 44 lamps, so that the average
life of the lamps has been 900 hours each ; but as eleven
of these lamps were broken maliciously by passengers in
the trains, their actual life is 1210 hours.
In this system the electric light is not used at night, the
gas or oil lamps being still made use of, which are there
to fall back on should a breakdown take place. ....'