ANOTHER MOTIVE POWER

Star (Christchurch), Issue 5427, 30 November 1895, Page 1

ANOTHER MOTIVE POWER

COMPRESSED AIR MAY COME 'NTO EXTENDED USE.

(Doiroit Free Press.)

Years ago, before electricity had made any headway worth speaking of as an agent for the transmission and. application of power, there was much talk about the utilization of compressed * air, as the mystic current from the dynamo has since been used. 'y'

Common air, Baid the* enthusiasts, is one of the most elastio substances known; it can be forced by the application of power to occupy much less than its normal space, and when so compressed is like myriada of ; finely tempered steel springs, in that as soon as the pressure iB removed it will at once re-expand bo as to fill its original space and in expansion give hack all the power used in packing its particles close together. This expansive quality is such as to -make the use of conipressed air by means of tho ordinary steam engine perfectly feasible, and, unlike steam, its expansive nature ia not destroyed by cold. Rightly handled the enthusiasts held, air might be made the great power transmitter of the future. It was to be but a short time then, before the horse was to be displaced by the new agent na a motive power on street railway lines; very shortly it would be distributed through pipeß in the streets to users of light running machinery, the samo as gas is now supplied to consumers for illuminating purposes ; tanks of air were soon to ba furnished from central pumping stations for the propulsion of horseless carriages and email launches, as storage batteries are. now in Borne. degree supplied, and practical uses of tho new agent were propossd in many other directions. Pneumatio transportation waa also soon to corns, certainly for mail and express matter, and probably for passengers ; in short, a rovolmion in the application of power was believed to be at hand, and. large sums of money; were expended here and there for

THE DEVELOPMENT OF THH NEW IDEA. But although compressed air has come into praotioal use in some few industries, the : more sanguine predictions of ' the enthusiasts have failed to materialise. In Paris and some other old world cities there are tram cara run by the power of air, but none as yet in America ; in most great European' capitals there is pneumatic mail and expreßß transmission, but very little this aide of the water. On both continents, in faot all over the world, where there is extensive mining and tnnnoling to be done, rock, ore and coal cutting drills are operated by compressed air, and it is also extensively used in certain engineering operations. It is in these directions, indeed, that this agent has made moßt notablo headway. *••■_.._ • Quite recently, however, renewed efforts have been made to br.ng compressed air to .the front in Amerioa as a factor in street •car traction, in the transmission of power over long distances, and in many other of the ways that it was intended to utilise it fifteen or twenty years ago. As a result of the experiments lately made in compressed air traction it is probable that air will soon be introduced as a motive power "on the surface lines' of sevoral oitieß, the first of which will be Eome, N.Y., and the second New York. . At Kome, where most of the experiments have been carried on, a single oar has been regularly operated by compressed air for Borne time, and bo successfully as to win the entire approbation of the State railroad commissioners. A month or Bix weeks ago these officers made special insnection of the

system and unanimously authorised the' local street railway company, which, had secured a charter to operate its road by means of the trolley, to substitute ▲IR FOB ELECTRICITY as its motive power. Preparations are, therefore, now going on with all speed to fully equip the line upon that basis. In the meantime, satisfactory investigations of the new system have been made by the Metropolitan Traction Company of New York, and within the next seven or eight weeks it will put six cars, fitted with the necessary tanks, and engines, upon its Ninth Avenue line. In appearance the new compressed air cars are very similar to the cara of- the overhead trolley systems, the trolley pole being conspicuous by its absence, of course.. The chief other difference in appearance is furnished by " aprons " that extend from the sides of the car nearly down to the track level, and serve to conceal the compressed air engines (each consisting of cylinder, piston rod slides, connecting rod and crank, the same as the working parts of a steam locomotive) that are placed on each. side of the car. The air is stored in tanks, so disposed under the seats and elsewhere as to "be quite out of fight. Some years ago a compressed air line was operated for a time at Pullman, 11., on, which, the air was furnished from a pipe running between the rails, which was tapped at intervals by an ingenious contrivance reaching downward from the car, but in the system about to be introduced, air tanks on each car are to be charged at stated intervals, from a central compressing station at a pressure of 20001 bto the square inch. It is . understood that there is no danger from this high pressure, since the tanks are teßted to stand twice as muoh, or 40001 bto the square inoh, and when by raising the pressure to 70001 bor 80001 b, they have been ruptured, there has been no explosion, only a smart puff of cold air, quite harmless in its effects. By a simple reducing device the pressure of the air in the tanks is brought down to 1501 b before it readies the engines, and it haß been found that, at thia pressure, there ia no noise of exhaust, as ' there is of course no smoke. Iv very cold weather there is a slight vapour, as of the breath of a man or a horse, due to the fact that the air is passed through hot water after leaving the compressor and before entering the tank. IT "WILL BB POSSIBLE TO RUN COMPEESSED AIR CABS as rapidly aB steam locomotives working at 1501 b pressure, with driving wheels of tha same diameter (26in) could be run— say fifteen or twenty miles an hour. It is claimed by the sponsors of the new agent that these cars can be run more safely than any others since they can be controlled mora ' effectively, and with much leas exertion on the part of the motor man. Air breaks of the utmost efficiency can b 9 used, the air being furnished direct from, tbe tanks and the entire pressure of 20001 bto the square inch bßing available if required, while the exertion on the part of the motorman in bringing his car to a full 8 top need only be that necessary to turn a little hand lever. A most important use of compressed air is for ; , the operation of signals at railroad terminals aud other points where the air is furnished through pipes from a central compressor to ; small cylinders, each of which operates a signal and a switch, and is controlled by a lever in the hands of a signal man located at some central point. The introduction of this system has been found to greatly inorease both the Bafety of trains and their rapid dispatch. Compressed air is also used to operate many small and somo large machines in many of the great railroad and other shops of the land. "••;..■■

A very interesting and simple maohine is the compressed air pump, whioh will force water or any other.' liquid from any depth or to any height,; and that without regard to the amount of dirt, sticks, stones or other foreign Bubstances that maybe contained ■in the liquid. Thia pump iB simplicity itself, consisting merely of two pipes, an air pipe being run alongside the one through which the liquid to be pumped is discharged. The air is then liberated at the lower end of the pipe, and the liquid is forced to the surface. There are no valves or. pistons or buckets to get out of order, and nothing smaller than the discharge pipe's diameter can clog the apparatus. Of course there must be a compressor aud engine with every pump, but with these provided all that is necessary to do is .to turn on the air and see the stream flow. This is a, comparatively new contrivance and so is the employment of

AIR FOR REFRIGERATION PURPOSES in place of anhydrous ammonia. The use of compressed air as a freezing agent waß explained to the writer by W. D. Saunders, of New York, to whoso courtesy the writer is indebted for a large portion of the information in thiß article :— " When air is brought to a high pressure," said Mr Saunders* ."the particles are; crushed closely together and thora is a tremendous lot of friotion, and this generates an immense amount of heat. So great is this heat that the air cylinders of compressors have to be jacketed with water to keep them from becoming red hot. Now, when the air expands, after having coolod in ita compressed state, it steals heat from whatever it cornea in contact with, thua producing^ refrigeration much more cheaply and with greater' safety and cleanliness than can be produced by any other means."

So much impressed have been certain men in one of the cities of the west that a proposition has been made to lay pipes iv

the streets there for the purpose of supplying, customers with cold air and doing away with the consumption of ice. In pneumatic transportation through tube., the atmosphere is employed at too low a pressure to be properly termed compressed air, and in some cases a vacuum and no pressure at all is used. Pneumatic tube transportation is used on a small scale in thousands of business and manufacturing establishments in America for the moving of small caßh and other packages, but its nse npon a large soale in this country is not extensive.