A description of the Blackpool tramway, written in 1890 for the Parliamentary Standing Committee on Public Works in New South Wales, Australia. The committee was considering a proposed tramway for use in Sydney, and looked at some of the tramways in use, in various countries.

Description of the Installation

The Blackpool system is described as electricity generated at a central station, and conveyed to the cars by the medium of an underground conductor lying centrally between the tram rails. The rails form the return circuit. The cars are worked in parallel.

The Blackpool line is nearly 2 miles in length. It is a single track, with ten pass-byes and one length of double line. The engine house and car sheds are placed near the centre; this position was selected as being the most convenient, and offering considerable advantages from an electrical point of view, compared with a generating station at one end.

The roadway runs along the sea coast and is exposed to the full force of the wind and tide from the Irish Sea. So strong are the periodical storms that, though the road level is well above ordinary high water mark, the waves dash over in such volumes that the road is flooded.

The difficulties in applying electricity underground in such a situation are therefore unusually great. When the tide is over the line, the current, of course makes earth. At one time it was intended to employ accumulators for haulage during the flooding, and horses were occasionally used; but owing to the amount of shingle brought over, the grooves in the rail were filled, and the cars kept running off. Working during the floodings has therefore been abandoned. These circumstances pointed to the necessity of allowing any dirt or shingle that might enter the slit in the surface of the centre channel to fall through freely to the bottom, and also of providing for its easy removal. The sump holes and traps for this purpose are placed at frequent intervals, and have direct drains connecting them with the sea.

The chairs are of cast-iron, 11 inches high with a 12½ inch base, and an internal width of 5½ inches; the bottom H rounded, and the ends have pockets for holding the side boards. These chairs are placed every yard, and support the steel troughing which is bolted to their surface; the nuts are covered and locked by a cast-iron cap.

The rest of the troughing is filled with wooden blocks. The sides of the troughs are inclined, so that when fixed, the space between them is ½ inch at the top, and 1 inch at the bottom, the object being that any stone having once passed the surface may easily fall through, instead of getting hopelessly jammed. Creosoted wood is used for the sides, with a view to adding to the insulation. The wood sides have a 2½ inch hole bored midway between the chairs, for the reception of the porcelain insulator; and ¾ inch holes are bored at right angles for the insertion of a wooden peg, which, passing through the groove in the insulator, locks it fast. This method has added greatly to the facility of construction. The roadway under the side-pieces is packed; the centre is concreted, and tooled to form the same curvature as the bottom of the chair.

The conductors are made of hard drawn copper, having a conductivity of 96 percent of pure copper. They are in lengths of 36 feet, and weigh almost exactly 1 lb. per foot.

A cross section of the conduit.

The tubes are connected one with the other by wedges made of drawn brass, exactly fitting the inside of the tube. Space is left between the ends to allow for expansion and contraction, and the wedges are secured from shifting by a wrapping of wire. The two tubes are electrically connected at every hundred yards by U-shaped loops of insulated and lead sheathed copper wire, placed in a groove that is cut in the sides and bottom of the channel. Over each of these loops is placed a hand hole, which is made by cutting both of the steel troughs and filling the place with two pieces of yard length, which are protected by suitable side plates. These hand holds are needful for many purposes, especially for the insertion of the scrapers used for cleaning the channels, and for the removal of collectors, should they become damaged or require adjustment. Only the positive electricity passes along the copper conductors. The return circuit is made by means of the rails; and to ensure its being electrically good, each rail is connected by a strip of copper passing from rail to rail, and plugged into holes punched in the ends.

Dealing with the points necessitated by the numerous pass-byes was a matter of no small difficulty, for in tramways it is desirable that the rail-points forming the turn-outs should be as fine as possible, so as to avoid strains and joltings of the car. In order to prevent the collector from fouling when taking the points, the ends of the secondary tubes are fitted with brass horns. Although the lay of the channel points is such that the collector has no tendency to take the wrong way, yet, for further security against such a mishap, a steel spring is placed at the toe, which guides the collector to the proper side in taking the points, and opens freely for allowing it to pass when leaving.

The collector consists of three main parts, namely, one centre-piece, and two clearing ploughs for enabling it to run in either direction. One of the elements of success in working electric tramways with conductors underground is the employment of a flexible conductor, flexibly connected. For this purpose the two ploughs are joined to the centre-piece, either by a tempered steel strip, or by a hinged wrought-iron plate. The tempered steel plates forming the ploughs are held by cast-iron cheeks, and being placed at a proper angle extend downwards a little past the bottom of the steel troughs; their upper ends terminate in a prong or finger, curved slightly backwards. The fingers receive the loop or ring of the hauling ropes, which are attached to the front and rear of the car. The ropes are strong enough to stand considerable strain, and their ends are fitted either with a releasing clip, or with a short loop of weaker cord, which is strong enough to bear the stress due to any ordinary obstruction; but should an absolute block occur, then the small loop breaks; or the slip lets go, and the collector is left behind, while the car travels forward.

At the same time the ring of the trailing rope slips off the finger of the rear plough; if this were not so, the force required to break the loop of the trailing rope would make the collector kick up, and would cause the contact-making part of the centre-piece to short circuit with the underside of the steel troughing. The centre piece consists of a cast-iron cheek, holding a plate of strong brass, which is thoroughly insulated and protected by hardened steel guards where it passes through the troughing. The bottom of the insulated plate is bared of insulating material, and has attached to it either a short plate of brass, or two brass wires forming a T, and holding at each end hard metal wings specially prepared. The forward wing is bent so as to press against the left-hand conductor-tube, end the rear one is bent so as to press against the right-hand tube. To the upper end of the insulated plate is fixed a clip, surrounded by an india-rubber ring. The clip is bored to receive a heart-shaped terminal, which can be easily pushed into it, but requires a fair snatch to withdraw it. A similar clip is fixed to the receiving wire under the car, end a short length of curled insulated wire, with a heart-shaped terminal at each end, makes a ready connection between the collector and the car.

The track and conduit.

The cars are of various designs. The smallest are light, open summer cars, seating thirty passengers. The largest are provided with transverse seats on the roofs, and carry fifty-six passengers. The levers of the ordinary chain break are placed outside the wheels, so as to leave a clear space under the centre of the car for the motor and the gearing. The mechanical construction of the motor was specially designed for allowing it to be fixed in position. The bearings are held in a circular frame, large enough for allowing the armature to be passed through it.

The motors are series-wound, and of such proportions that they yield a high efficiency, running in either direction, without giving any lead to the brushes. Reversal is effected by changing the internal coupling, that is to say, while the current through the field is always in one direction, the current through the armature can be reversed, thus changing the relative polarity and consequent direction of motion. Each brush consists of a thin steel plate, insulated from the studs and free to work on them. The steel plates are divided into fingers, which carry little blocks made of a special metal, and capable of being easily renewed. The blocks are made to press against the commutator by small bands of india-rubber stretching from tip to tip of the fingers. The pressure of the brushes is thereby regulated and equalised, and the vibration and jolting are compensated.

With regard to the gearing, it may be explained that to the circular frame of the motor is bolted the base of an elbow bracket, which carries the invert wheel-gearing into a gun-metal pinion on the end of the armature spindle. The box holding the invert wheel has upon its back a chain pinion, from which the power is taken to the large wheel keyed upon the axle of the car. The elbow bracket can be turned upon its base, so as to either slacken or tighten the chain at pleasure, without moving the motor or disarranging the centres of the armature pinion and invert wheel. But for the inevitable stretching of the chain, and the noise when new, this gear would be all that could be desired.

The wiring of the cars is carried out as follows: In order to control the quantity of current, and the consequent speed resistance, coils are placed in certain positions, and are coupled with the switch-boxes under the car steps. A removable handle is used for driving, end a plug fly-switch for reversal; these are in charge of the driver, and when the car has completed its run in one direction, he carries them to the other end of the car; this plan prevents any accidental derangement, as it is impossible for the switches to be worked without them.

Medium sized car, seating 48 passengers.
 

Underframe.

As the cars have to work all day, the engines and dynamos are in duplicate, each being capable of doing the full ordinary work, while in case of need both can be used at once. The engines are 25 nominal horsepower, compound none condensing, of the semi-portable type, with locomotive boilers. A second motion-shaft is employed, in order that either or both of the engines may drive either or both of the machines. The dynamos are placed on a higher level than the engines, which enables the wheels controlling the friction couplings to be placed in a position where they can be worked conveniently by the engineman.

The generators are four pole shunt wound dynamos; but, instead of allowing any current from their own armatures to pass round the field magnets, these are separately excited by the little machines. As the electro-motive force of the external circuit varies directly with the intensity of the field, it can be regulated to a nicety by varying the resistance in the circuit of the exciter. This resistance is, by preference, placed in the armature circuit of the exciter. The maximum electro-motive force of the generators is 300 volts; and each will yield 180 amperes. They can, when required, be run in parallel. The total length of No. 17 wire (0.06 inch thick) on the magnets of each generator is about 14 miles.

Measures were taken of the insulation of the line during construction, and 150 yards length was found to give 4,490 ohms. The average working loss through leakage may be taken at 25 amperes, which at an electro-motive force of 220 volts is equal to 7.2 horsepower.

As the efficiency of the generators is about 90 percent, and of the motors about 80 percent, much further economy must be looked for in them, though it should be possible for the loss of the generator to be not more than 5 percent, and in the motor 10 percent. The chief part in which to look for further economy is the line itself; and in this, the first point is more perfect insulation, and, consequently, less loss in leakage; and the next is, more perfect continuity in the conductors, and therefore less loss through resistance.

From the minutes of evidence prepared for the Australian Parliamentary Standing Committee on Public Works, for New South Wales.