The Daily Dispatch: August 22, 1861., [Electronic resource]

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A Novel experiment.
[from the London Mechanics' Magazine.]

On Wednesday some experiments on a rather large scale were made on the right bank of the Thames and immediately below the railway bridge, Batter sea, with a view to testing the efficiency of transmitting goods and parcels proposed by the Pneumatic Dispatch Company. The mechanical arrangements in connexion with the experimental line of cast-iron tubing — which, like a huge black snake, stretches for more than a quarter of a mile along the river side — are few and simple. Under a temporary shed a high-pressure steam engine of thirty-horse power, made by Watt & Co., and having its cylinder placed at an angle of forty-five degrees, is erected, and it gives direct motion through the medium of a crank to a large disc of sheet iron.

The disc runs on tubular bearings, and narrows from about two feet six inches in breadth at its centre to three inches at its circumference, its diameter being eighteen feet. Its interior contains simply four arms, to which the sheets of iron are fastened, and which serve as fans or exhausters. Through the hollow bearings upon which the disc is made to rotate at a speed of from one hundred and fifty to two hundred revolutions per minute, a communication exists with a vacuum chamber below, and by the laws of centrifugal action the latter is speedily exhausted, to a certain extent of air. The speed, in fact, of the disc determines that extent, and a water barometer registers it. The air rushes out with considerable force from the periphery of the wise. Between the vacuum chamber and the pneumatic tube, which is two feet nine inches high, by 2 feet 6 inches in breadth, and a transverse section of which resembles that of the Thames Tunnel, there are fitted valves with hand levers for opening and shutting them. These may be said to comprise the whole of the motive and propelling agencies of the pneumatic system.

The tube has been laid down in Batter sea Fields, in such a manner as to test severely the practicability of the scheme. It has several very sharp curves and sleep gradients throughout its length, and is socket-jointed, so as to leave its interior, which is just as it came from the sand, free from obstruction. The carriages are five feet in length, of sheet iron, and each runs upon four cast-iron wheels of eighteen inches in diameter. The rails — so to speak — are cast in the bottoms of the tubes, and require, therefore, no ‘"laying"’ but that which the setting of the tubes themselves gives them. A few strips of vulcanized India-rubber screwed round the circumference of the fore end of the carriage constitute the piston. This, however, by no means closely fits the tube. In fact, there is fully three-eighths of an inch clear between the exterior of the piston and the interior of the tube.

There is no friction, therefore; and, singular to say, the leakage of air does not interfere with the speed of transit. This can only be accounted for by the large end area which the carriages have, in comparison with the small area of leakage space and the comparatively low vacuum required. On wednesday last the first experiment made was by loading a carriage with one ton of cement in bags, and entering it into the open end of the tube. Upon a given signal the engineer to the company caused the starting valve to be opened, the water barometer showing a column of seven inches in height, and the disc running at the rate of 150 revolutions per minute.

In fifty seconds after, the carriage with its contents found its way into the engine house, through a door at the end of the tube, which it forced open, and then ran forward on rails to a butt placed to stop its progress. Next two tons weight were placed in one of the carriages, and its transit occupied eighty seconds, under similar circumstances. The vacuum was now lowered until the barometer gauge showed two inches of water only, and a living passenger, in the shape of a not very handsome dog, was placed with one ton weight of dead stock, in a carriage. The signal was made by the workmen at the open end of the tube, the communicating valve was opened, and in one minute and a half the carriage and its four-legged guard were in the engine-house, the latter apparently not at all the worse for the exhausting process to which he had been subjected.