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The New Zealand Railways Magazine, Volume 1, Issue 3 (July 24, 1926)

The Evolution of the Westinghouse Automatic Air Brake

page 37

The Evolution of the Westinghouse Automatic Air Brake

The mechanism and appliances for controlling railway trains on grades and for stopping at stations, like many other important inventions, started from very small beginnings. In the early days, when four wheel stage coaches were the principal means of travelling, it was found necessary on descending steep grades and inclines to have some means whereby to check the speed of a vehicle so that it could be controlled in safety. A practical means of carrying out this idea dates back only about 272 years.

Before this the means of controlling wagons, carts, or coaches when moving down steep places was very crude. It generally consisted of placing a sprag through the spokes of the wheel and allowing them to skid along the surface of the road, the friction produced helping to retard and govern the speed. Other methods for the same purpose were in use, such as chaining a log of wood, or a stone to the back of the vehicle, and this dragging along the ground acted as a check or brake.

Improved methods of controlling stage coaches, wagons and such like vehicles, date back principally to the time when the condition of the public roads was being improved, and it was becoming possible to travel more quickly than formerly from one part of the country to another. The stage coach between London and Bristol ran a distance of 117 miles in 15 hours, or an average of about 7 3/4 miles an hour, including all stops for changing horses, etc., so that the maximum speed must have been much faster. And so the braking and controlling of road vehicles improved as the demand for higher speeds increased.

From 1770 to 1870 there were granted 190 patents for braking appliances for common road vehicles. Of these, forty-six were applied to the rim of the wheel, twenty-eight to the nave, twenty-seven were actuated by the movement of the horses, twenty-one were applied to fly or brake wheels; eight were applied to the axle, ten were worked by a spring; four were automatic; three electro-magnetic; three pneumatic, four relying on momentum, three accumulated power for subsequent propulsion.

In America 170 patents were registered, 21 of which were for automatic designs.

The first brake devices adopted formed the basis generally for all later types of braking appliances. The early stage coaches were provided with an iron shoe which, on going down hill, was placed under the wheel so as to drag along on the surface of the ground, and thus retard the vehicle from going too fast or getting out of control. This method is still in vogue at the present time on heavy horse-drawn vehicles.

The arrangement of two brake blocks with a beam connected to each so that the driver could manipulate them by a lever, was and still is in common use, on many New Zealand horse-drawn road vehicles.

The beginning of railways and railway appliances dates back to 1630, when a coal mine-owner at Newcastle-on-Tyne, finding the roads between his mine and the river so bad as to seriously interfere with the handling of the coal, placed on the roadway wood rails and ran thereon wagons with wooden wheels. The tractive effort was so much decreased, that the necessity of some controlling con-trivance to check the speed on the inclines was found essential, and brought out some simple forms of braking appliances. One of these consisted of a metal tipped beam fastened to the frame of the wagon in such a way as to scrape along the ground at the side of the track. Another was a simple lever attached to the side of the wagon. This, when desired for use, was pressed down by hand or foot on to the top part of the wheel.

The invention of the locomotive and the laying of railways as we know them to-day created a demand for an efficient train brake, and many interesting and ingenious devices were made and patented.

In Britain 650 patents were granted for various railway brakes. Of these, twenty-one were electro-magnetic; twenty hydrostatic; thirty-two pneumatic, fifty steam; the balance being mostly handbrakes and designs of foundation brake gear.

In 1833, Stephenson patented a steam brake, which consisted of a simple steam cylinder with a piston, the rod of which connected through a system of levers to a cam brake. The first air brake was a vacuum brake patented by James Nasmyth and Charles May in 1844. In 1848 Samuel C. Lister patented page 38 an air brake having an axle driven pump, and suitable reservoir to be placed on the guard's carriage or van. Suitable cylinders, pipes and connections on the various vehicles constituted a straight air brake equipment (similar to that on our electric cars to-day). This was operated by the guard.

In the U.S.A., up to 1870 there had been granted 305 patents for railway brakes, of which eight were automatic; three electro magnetic; five steam; one vacuum and two air brakes. Some of these inventions were put into service and, at the time, seemed to meet requirements.

The Cramer brake came into use in 1853. This consisted of a large spiral spring attached to the brake shaft at the end of the car; this spring was wound up by the brakemen immediately after leaving a station. Attached to the mechanism was a cord running through the train to the engine cab. This brake was so designed that when the enginedriyers pulled the cord, coil springs on each vehicle were released at once winding up the chains attached to the brake levers, bringing the brake shoes against the wheels.

Fern Arch, Buller Gorge

Fern Arch, Buller Gorge

The Longbridge chain brake came in 1855. This consisted of a system of rods and chains connected throughout the train. On each vehicle were two pairs of small pulleys, each sliding towards the other upon an iron framework, but held apart by a spring. To each pair was connected a top rod leading to the foundation brake gear. Upon the engine was placed a drum connected by a worm and gear to a small friction wheel. When the lever was pulled the friction wheel came into contact with the driving wheel, causing the drum to wind up the chain and shorten its length throughout the train, thus bringing the pulleys on each vehicle closer together and applying the train brakes.

Hydraulic train brakes were also brought into service, worked by liquid stored under pressure in an accumulator. The pressure was obtained by a direct acting steam pump on the engine. In the case of automatic brakes, water under pressure was stored in receptacles under the cars. These brakes applied, on emergency, in a manner quite similar to the automatic air brake.

In 1869 the Westinghouse non-automatic air brake was brought into service. It consisted of a steam actuated air pump placed upon the side of the engine, and a reservoir for compressed air. Connected to this reservoir was a three-way cock having a pipe which carried throughout the train, connections between the vehicles being made by means of flexible hoses and couplings. Each vehicle was provided with a simple castiron cylinder, the piston rod being connected to the brake lever. When compressed air was admitted to the cylinder, the piston was forced out and the brakes applied. Compressed air passed into the train pipe and brake cylinders by means of the three-way cock, when desirous of releasing brakes the three-way cock could cut off the reservoir pressure and exhaust the air pressure from the train pipe and brake cylinders to the atmosphere.

This was the most simple and efficient railway brake that had been brought into service so far and was largely adopted by the American railways. Experience soon indicated that there were several weak points in it, however. The applications throughout the train were very slow, and if a hose coupling between the vehicles burst, or the train parted, the centre braking power was lost. Experience soon made very clear the fact that a railway brake to be satisfactory must be perfectly automatic.

This led to the introduction of the Westing house ordinary automatic brake which was designed in 1872, and complied with all page 39 the requirements then found wanting in the non-automatic system. Although the change to the automatic principle provided a reliable apparatus, and safer and more efficient than any other method then in use, it met at first with considerable opposition. The objection, however, disappeared as it became better understood, and its value was recognised and fully appreciated.

The automatic principle, first introduced by Mr. Westinghouse, has long since been generally accepted as the principle upon which continuous brakes should act.

For many years the Westinghouse ordinary brake rendered valuable service, but the progress of the railways developed new conditions. These were met by the invention of the Westinghouse quick-acting brake in 1887. Its action is practically instantaneous and simultaneous on all vehicles of a train of any length. The difficulties, which before this prevented the application of continuous brakes to long trains, were overcome. In actual tests with trains 4,000 feet long the quick acting brake applied from the engine to the last vehicle on the train in about two seconds. The extremely rapid action obtained by this means considerably reduced the distance in which trains could be stopped.

In 1909 Mr. H. H. Jackson, then Chief Mechanical Engineer of the New Zealand Railways, carried out some air brake tests in the South Island. The following was one of these tests:-

A train consisting of a tank Wf engine, 30 La iron wagons, and a bogie brake van; weight about 212 tons, speed 33 miles per hour; train stop 330 feet; time of stop 16 seconds; level track.

Although the Westinghouse quick-acting brake was a considerable improvement and gave better results than any previous brake, the still further rapid advance of the railways and the desire for higher speeds called for some improved methods of making shorter and smoother station stops. To meet this demand of the railway world, the Westinghouse Brake Company in 1908 brought out an improved triple valve, designed to give a quicker and smoother brake application when making station or emergency train stops. The improvement consisted of quickening the application of the air brake on every vehicle on the train by the simple method of automatically making local train pipe reductions on each vehicle, causing an earlier action of the rearward triple valves, and a more simultaneous braking effect being produced with every train stop.

In America the Westinghouse air brake has developed to a very high standard of efficiency making it possible to control trains safely running at a speed of 60, 70 and 80 miles per hour, and also heavy trains weighing 16,000 tons on the grades and 17,600 tons on the level track, the length of the heavier train being over a mile and a quarter, the weight of the engine alone being 450 tons.

Few people travelling on railways have any conception of the appliances installed for their protection and safety. On the New Zealand railway trains the proportion of brake power available on any train is about 70 per cent of the empty weight of that train. For example:-a train, weight 100 tons, has a brake stopping force of 70 tons. This high brake power is always available and is easily controlled by the enginedriver. By moving his brake valve handle he can apply the Westinghouse brake lightly or with its full force and give air brake graduations or applications according to the train stop he desires to make.

If the train should part the air brake will immediately automatically apply on every vehicle in the train, while in cases of necessity or emergency the guard can apply the Westinghouse brake from his brake van.

The whole working parts of the Westinghouse Automatic air brake are very simple and the principles to operate and manipulate when (1) charging (2) applying or (3) releasing, consists of (1) equalising (2) decreasing and (3) increasing the compressed air in the brake apparatus.

Tour Of Indian Hockey Team.

The following is the text of a letter recently received by the District Traffic Manager, Dunedin, from the Secretary of the Otago Hockey Association in connection with the visit of the Indian Army Hockey Team:-

The generous manner in which you assisted the officials of the above Association in connection with the recent visit of the Indian Army Hockey Team is very much appreciated. Your valuable co-operation considerably minimised our difficulties, and I now on behalf of the local Association tender you our very best and sincere thanks for your help and support.

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They are never alone who are accompanied by noble thoughts.-Sir Philip Sydney.

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Education is the giving or withholding of opportunity. Equality of opportunity means first and foremost a liberal education.-Professor N. Bateson.