|July 1931, Vol. 24, No. 7
|Railway Signaling (Chicago IL)
New interlocking on the Toronto, Hamilton & Buffalo at Hamilton, Ont.
Old layout replaced by 72-lever plant—New cable distribution constructed under traffic without stopping a train
A large electric interlocking plant, involving a new interlocking machine, new signals and several new switch machines, together with an entirely new cable wiring distribution, was recently constructed by the signal department forces of the Toronto, Hamilton & Buffalo in the terminal area of Hamilton, Ont.
The track layout includes a large wye. The main line extends from the Hamilton station to the east end of the wye, the line to Toronto goes around the north leg, and the line to Waterford around the south leg. A cross connection, between the lines to the east and the west, forms the west leg of the wye. The several switches, crossovers and signals are shown in the illustration, including a picture of the illuminated track diagram. Briefly, the new plant includes a machine with 65 working levers controlling 26 switches, 12 derails, 9 high signals and 18 dwarfs; there are 7 spare levers. The new plant is the General Railway Signal Company's Model 5D.
In 1907, a General Railway Signal Company Model-2 electric interlocking plant was installed at this layout. This old machine had 75 working levers with 13 spares. The former enginehouse and shops were located within the area bounded by the tracks forming the wye, as explained previously. In 1929, a modern engine terminal and shop were constructed at a location about one-half mile west. The old engine facilities were removed, which necessitated several changes in and an addition to the track layout included in the interlocking. As the old interlocking had rendered satisfactory service under heavy traffic for 24 years, the T. H. & B. did not consider it logical to make extensive changes and additions to the present equipment. Likewise, so many important improvements have been developed in interlocking apparatus in the past decade, that it was decided to replace the old interlocking with new equipment.
The Interlocking Tower
The old tower, which was too small and not well located for the new lay-out, was razed and the well-constructed two-story brick building formerly used as the office of the superintendent of motive power, although slightly larger than necessary, but suitably located, has been transformed into an ideal interlocking station.
The Interlocking Machine
The new interlocking machine is the G. R. S. Model-5D, equipped for latch locking provided with forced-drop electric locks, the first machine of this type to be installed in Canada. The mechanical locking is so arranged that there is no definite order for manipulating the switch and derail levers, i. e., the switch and derail levers do not lock each other, but are locked mechanically by the signal lever governing the respective route set up. This arrangement facilitates the setting up of new routes and is a great help when clearing switches or derails in a storm, for, unless a signal is cleared or the track circuits are occupied, any switch can be thrown at will.
A small lamp is mounted behind each lever number on all switch and derail levers. If the lever is unlocked electrically, the pulling of the latch causes this lamp to be lighted. This indicates to the towerman that he is free to move the lever. Immediately above each switch or derail lever, there is another light, with a red lens, known as the "transit" light, which, when a switch machine starts to operate, is lighted and remains lighted until the switch is over and locked. If the light remains lighted, the towerman knows that something is wrong and he can reverse the switch to smash the snow, ice or other obstruction, and, if not successful, he can call the maintainer.
A separate common wire extends from the interlocking machine to each switch machine ; this practice confines any ground trouble to the individual circuit. Separate cross-protection relays are provided in the machine for each switch and derail control circuit.
Dynamic current from the motor of the switch machine operates a circuit selector located in the interlocking machine. The WP relay circuits from such ma chines are selected through contacts on these circuit selectors. The signal control circuits are selected through the track relays, and, in addition, through the WP relays, as a means of checking the position of the switches. The RP relays are energized when the respective signals are in the Stop position. The YR relays are energize when certain signals are in the red or yellow position. Finally, the forced-drop electric locks are controlled through the LR relays, which in turn are selected through the YR and RP relays, as well as track relays, time contactors and lever circuit breakers.
For all high signals the routes are approach locked by time contactors. If a train enters the approach section of a route, for which a signal lever has been pulled and the signal cleared, the signal lever can be restored to normal, permitting the signal to return to its most restrictive indication. However, none of the levers for switches or derails in the route can be moved until a time interval of 1 min. 45 sec, imposed by a time contactor, has elapsed. For dwarf signals, this time interval is set at 15 sec. If no train has entered the approach section, the whole route can be changed immediately.
Sectional route locking is effective so that various sections of each route can be released behind a train so as to permit the line up to be changed quickly.
The machine is equipped with plunger-type circuit controllers mounted at the rear of the machine.
A slot cut in the floor beneath the interlocking machine permitted the construction of a passage way or pit 6 ft. 6 in. in height. This pit facilitated construction and is a decided assistance in making inspections or locating trouble.
From this rack, the wires are run through a special conduit to the terminal cabinet in the basement. This conduit is made of wood, lined with asbestos and covered with sheet metal.
Power Supply and Battery
The main operating battery for the plant consists of 56 Exide DMGO-9 cells of lead battery rated at 240 a. h. and has the capacity to operate the plant 67 hours in case the a-c. supply is cut off. The battery shelves are arranged for convenient inspection. Each shelf is made for one row of cells only, and the shelves are 2-1/2 ft. apart and set on concrete piers 3 ft. high.
Seven other sets of battery, totaling 27 cells of Exide KXHS-7 are used for the various relay control and lock circuits, as well as furnishing an emergency standby for the lamps on certain signals near the tower.
The main battery is on floating charge of about 2.5 amp. from a motor-generator set rated at 7 amp. 120 volt. As a reserve set, to be used for cycle charging if required, a Crocker-Wheeler motor-generator set rated at 35 amp. 150 volts is held in reserve.
The two-section switchboard is equipped to throw the incoming two-phase four-wire a-c. feed to either one or the other of these machines. Each machine is in turn controlled by a compensated automatic push-button starter with the buttons for starting and stopping located on the switchboard. These buttons are located in positions corresponding to the machines so that they may be manipulated without confusion as to which machine is controlled by each set of buttons. Mounted on the second panel are the meters and switches for the various batteries.
The switchboard is mounted four feet from the wall, to provide plenty of space in which to mount cut-over relays, rectifiers and auxiliary devices on the wall. All lighting and power wires are in metal conduit.
Signals and Switches
The old semaphore signals were all replaced with SA searchlight-type signals. These signals are equipped with permanent magnets for the field, and are understood to be the first of this type manufactured. The high signals are mounted with the center of the top light 12 ft. above the level of the rail, which brings the signal about on a level with the engineman. Call-on signals are used on all high and intermediate speed signals ; these call-on units are controlled by push-buttons above the respective lever.
Some of the old Model-2 switch machines were over hauled and used in the new layout. The new switch machines are all the Model-5A.
As the old wiring distribution, installed 14 years ago, consisting of single conductors run in wood trunking, was in rather poor condition, an entirely new system was provided, using cable exclusively. The main leads from the tower to main junction boxes are run in 30-conductor No. 12 parkway underground cable, each wire having 5/64-in. insulation, with a protection of two wraps of steel and a jute covering. From these main junction boxes, aerial cable made up of single conductor wire is run along to other junction boxes. From these boxes parkway cable is run to the switches, signals, etc. The aerial cable is made up of single conductors supported from a stranded messenger by Raco straps spaced 14 in. apart. These single conductors have 5/64-in. rubber insulation with a covering of two thicknesses of braid. Porcelain-base A. R. A. terminals are used in the junction boxes, no wires being spliced in runs.
A special telephone circuit extends from the tower to various points located over the plant and loud-ringing gongs are used at these outlying points so as to call the maintainer to the phone in case of trouble.
The entire construction of this plant was handled under traffic, with no train delays. The new dwarf signals were installed as required. The new SA signal heads were clamped on the masts of the old high signals. The control circuits for the old wiring and the new wiring were brought together at double-throw switches installed temporarily in the new tower. In cutting over from the old machine to the entire new layout, these switches were thrown and the new plant was ready for operation almost before the towerman could walk from the old to the new tower. Seven minutes elapsed, without any train delay, during this cut over.
This plant was designed and constructed by the signal forces of the Toronto, Hamilton & Buffalo under the jurisdiction of R. L. Lathan, chief engineer, and under the supervision of Aden A. Hurst, signal supervisor, to whom Railway Signaling is indebted for the information in this article.
Railways: T.H. & B.Ry.