„- UP-TO-DATE RAILWAY STALLING.

Otago Witness, Issue 2810, 22 January 1908, Page 34

„- UP-TO-DATE RAILWAY STALLING.

THE, ELECTRO-PNEUMATIC SYSTEM. - - ; PIONEERED - AT, DUNEDIN: • TO BE INAUGURATED ON MONDAY. Dune Sin has been selected by the Railway Department as the first railway centre in New Zealand at which .to instalj the electron-pneumatic signaUing and"- vuiterlooking system, _and.<>its introduction marks a further advance in the. already up-to-date railway management"*6f the Dominion? The installation has been complete for some time, but its general use has been decayed) until those who would have the operating 1 of it were thoroughly conversant .with all details. Everything is ridw reftdy', and! since Monday all signalling in the Dunedin yard has been carried out by means', of tho new appliances. The following* is an. authoritative description of the general principles _ of the system: 1 — Points, including all looks and bars working in conjunction with same, signals of all kinds and forms, crossing bars, gates, etc., are operated by compressed 1 - ' air acting! through motors consisting of - small cylinders and> valves, which in general principle resemble the cylinder in use for working the Westinghouse brake. The valves controlling fchtT admission, and 'exhaust' of air _ to and from -the 'motors are "actuated*by electro magnets, through; ..which - smalK electric "currents circulate when , the levers " In" fche-oabinis 'are 'in 'i'cer&iin positions. looking' frame «&•' thp cabin-; ' ;o£ very, 6mall hand levers, five inches in length and spaced at two and. a-half inches apart. These levers are mechanically , interlocked, as in,, the case of -the presen^ system, of interlocking, but 'on a very muon" smaller scale. „ The movement "of one of these levers - operates suitable" electrics switches, which then transmit the electric current to the valves governing the admission of compressed air to the motors. In the case of facing •points, when the levexVoperating the points is v pulled by the signalman (assuming that everything dependent -upon that lever is, in its proper position) _>the electric current is transmitted to the points* motor, which, in turn, unlocks ' the points and reverses the bar, puts the switch in the position required, and rejocks i*. It will be observed that the looking of tho switch is the last movement that the motor makes, therefore it is, this movement^ that -is of the most Importance to the signalman before lowering- the signal fcfr a train. To fully safeguard against a signal! being put to •'clear" or "off "-before, the points aTe properly looked an electric indj-. cator is connected to the lock itpelf. This indicator forms a contact by which the signal lever, is releasec?. AU motors for working" points are double-aoting, and are secured to the sleepers to which the points themselves- are secured. This Is an invaluable feature' of the system, as it enables the points to be operated by line signalman from the> cabin while the road m beinff lined -up/'etoi " The' -motor, is * connected to the air main by moans of, a" flexible- pipe* Signal .motors are fitted ■to the sides of signal posts or) on ,fch'e disc timbers, as the case may b#. / The -difference' between, a point- motor and a : ~Bignal motor is ' tha* the former ie doable-actinff and'^the latter,-csingle-acting. /. The function of the signal) motor is '-to -force 'the arm to -the "lineclear" or "off" position. The force of gravity returns tbe arm to theypositioni of danger when the air pressure is released! from the back of the piston. In thus trusting to gravity to replace the arm _to " danger " all chances of the ..arm being; held "off" owing to the" failure of tha power supply are eliminated. The signal motor, like the point motor, is governed! by an electro-magnetic valve. A circuitj breaker is attached to all signal " arms - and "discs," and is connected to them irf suoh a way that directly the arm or dis* is -put to the "line clear" position the contact is broken. The movements of all points, signals, etc., are thus electrically indicated in the locking frame in the cabm in such a way that, should any movement be .ptertiallyj or wholly prevented^ the lever, and aU other levers, dependent ton it, 'awr locked up, and so cannot be aooved in< a -dangerous manner until the cause cf the obstruction is removed. . \ Another valuable feature of this systemi is the operating of a number of signals from one lever. As many~as six. signals will be operated from the 6ame lever when the- system is brought into operation at Dunedin. This is done with absolute) safety, and 1 is , explained thus.: — The signal* man requiring to turn ati incomings train into the "loop" road and to give the signal for, that road, first- pulls the levei; operating the loop road points " motor ;j then, as already described, the lock, operates the contact, which in turn transi mits the current' through the signal lever to. the -signal motor/ which operates met arm applying to the loop road. In the case of any other rdad j and signal apply* injj thereto the -operation is the same as described above: .The" signalman simply operates the points lever and then the same signal lever as he used for the "loop" road, the points indicator selecting 1 which "signal motor shall operate when the signalma-n, moves his lever. Under the old system of interlocking- no less than 150 levers would have been required to work the Dunedin yard, while with the new system it will be worked 1 wifih a total of 65 levers. These 65 levers are made up as follows:— 32 levers to operate 82 signals, and 33 leve ra •*« operate 61 points, locks, bars, etc. T;hera being no long leads of rodding and signal I wires used, and, as all air pipes and elec* trio wires will be underground, _ the shunters will run no risk of being tripped! up when running about the yard at night* time. This in itself is a valuable feature from a safety point of view.