When the Bridge is Built.
This article appeared in The Sydney Mail on November 21, 1923, one of a series of 29 by Kathleen Butler. The original poor quality newspaper printed images have been substituted with the same images from Bradfield's December 1923 DSc(Eng) thesis. As stated in the sub-heading Butler wrote the articles from the 'Notes of Mr. J.J.C. Bradfield.'
IN the bustle of a city the average citizen seldom stops to think what part an engineer plays in the amenities of modern life. The opening lines of the Sydney University engineering students’ song–
For second to none is the Engineer,
o Czar or King or Sirdar–
“modestly” acclaim this: but without doubt the opening up to civilisation of new countries by a winding thread of steel is the greatest romance in the world’s history.
The operation of the suburban railways by electricity will result in a quicker, cheaper, cleaner, and improved service, and more capacious passenger coaches. The annihilation of time and distance will enable many people to live in the glorious surroundings of Sydney’s outer suburbs. The construction of the Sydney Harbour Bridge will reduce the travelling time of the average suburban resident to and from the city by quite 15 minutes.
Railways have shrunk time and distance, and Sydney is now spending millions to save minutes – many minutes, indeed – when her suburban population are served by a quick and up-to-date electric railway service. From Bay-road to-day, if everything fits in, by train, ferry, and the railway tram, it takes quite 30 minutes to catch a train at Central Station; but within seven years – politics permitting – it will take only 12 minutes. This article briefly explains how this will be accomplished.
At this point the train will have reached a speed of 40 miles per hour on its run to Wynyard-square. The accompanying article shows that from Bay-road Station to Wynyard -square Station – a distance of four miles – the time taken will be 7 minutes 11 seconds, whilst from Bay-road to Central Station the time occupied will be 12 minutes, including stops. The average running speed, including stops, will be 24 miles per hour.
THE forces which oppose the motion of a train on a level stretch of railway are rolling friction of the wheels on the rails, the friction of the axles on the bearings, and the pressure due to the displacement of the air owing to the speed of the train. If there is a head or side wind the air resistance is increased; these are the “train resistances.” Then there is the opposing force of gravity, which reduces or increase the speed of a train travelling up or down the grades – i.e., “grade resistance;” and, lastly, there is “curve resistance,” due to the side friction of the wheel flanges when running on curved track. Then in opposition to the resistances is the tractive effort exerted by the motors, tending to haul the train along the rails.
For Sydney’s electric railways the motor-cars will be equipped with four motors wound for 750 volts each, or with two motors would for 1500 volts, and capable of not only overcoming the train resistance, but of increasing also the speed of the train at the rate of a mile and a half per hour per second on the level. In twenty seconds the speed of the train could be increased to 30 miles per hour, whilst the brakes are designed to decrease the speed of the train one and three-quarter miles per hour per second – i.e., a train running at 35 miles per hour would be stopped by the brakes in 20 seconds.
THE next factor which enters into the time of journey is the length of stop at each station. This depends chiefly upon the routine of the travelling public, so that those entering or leaving the cars or the station do not come into conflict. The designs of the car and of the station entrances and exits are thus essential factors. In the car the doors should be arranged to ensure rapid ingress and egress, and the essential in such a car is to encourage alighting passengers to gather about a door before the train comes to a stop. Efficient car lighting and platform lighting also assists quick passenger movement. The new all-steel cars now being constructed have a weight of 105,000lb for motor cars and 83,000lb for trailer cars, seating 79 and 83 passengers respectively; but, including standing passengers, the cars will each accommodate 120, or about 1000 passengers per eight-car train. Each car will have two doors on either side 5ft 10in wide; Three passengers can leave the carriage abreast, and it is anticipated that the time taken in stops at each station will not exceed 20 seconds, except at Wynyard-square, where 30 seconds may be taken. On the London tubes a normal station stop is from 10 to 15 seconds, whilst the average stop of 25 consecutive trains at one of the busiest stations in the evenings rush hour was 22 seconds.
HAVING determined on the grades and curves of the railway, the horse-power and characteristics of the electric motors, the design of the rolling stock and station entrances and exits, the speed of the train at any point and the time of journey for any distance can be ascertained. From Bay-road station to Wynyard-square station the time taken will be seven minutes eleven seconds, whilst from Bay-road to Central Station the time occupied will be twelve minutes, including station stops, the distance covered being four miles. The average running speed, including stops, will be twenty-four miles per hour, and the train will reach its maximum speed of about forty miles per hour just after passing over the main pier at Dawes Point, where shown in the picture.
