Engineers and Mechanics Encyclopedia 1839: Railways: Samuel W. Wright
The application of compressed air to the propulsion of carriages, was also attempted by the ingenious Samuel W. Wright, who had a patent for the same in April, 1828. As the mechanical combinations of this gentleman usually possess great interest, from their originality and a skilful mode of applying them, we shall here introduce a description of his locomotive machine, with reference to the following cut.
The above figure represents a side view of the machine, partly in section. a-a-a is the frame work upon which the engines, machinery, and body of the carriage are mounted; at b there are two long metal cylinders (one being behind the other), having semi spherical ends for containing the compressed atmospheric air; these vessels are filled by means of pipes and cocks, either from a stationary reservoir under the required pressure, or by means of air pumps.
For the purpose of increasing the elastic force of the compressed air, it is allowed to enter through pipes and cocks at d into a third cylinder e, placed above the two, and extending over one of their extremities; under the middle of this third cylinder there is a small furnace, whereby the air is heated, and its expansive force increased before entering the working cylinders of the engine, which are situated at 1. This heating is chiefly effected by a pipe y, proceeding from the furnace, and entering a series of tubes contained in the cylinder e. When the air has acquired sufficient elasticity, it is admitted through a pipe h into the slide valves i, and thence into the cylinders; the valves being worked by eccentrics and rods in the usual manner, as partly shown. The force is communicated by the piston rods to connecting rods at n-n, which give rotation to the cranks at o, the shaft p, and the drums q, which are connected by bands or straps to the drums at s; these being fixed upon the naves of the running wheels t-t, communicate motion thereto, and propel the carriage.
Steam may be generated by the furnace f in a small boiler or pipes, and be then conducted to the cylinder e, where giving out a portion of its heat to, and combining with, the compressed air, the air is thereby rendered more elastic. The heat or steam from the furnace f may be conducted to the engines (without using the third cylinder e-e), and there unite with the compressed air from the cylinders.
Mr. Wright does not describe, but merely mentions that the man having charge of the machinery may, by "any proper connecting gear, control the working of the engines, valves, cocks, and force pump, and stop or abate the speed of, or set the carriage going, as may be requisite;" and he proposes that an eccentric motion be added to the shaft p, which, by a connecting rod, shall "work a pump, to compress and force air into either of the cylinders, when the carriage is going down hill, and which will serve also as a brake to check the speed in descending."
When the carriage is to be guided out of the straight line, the winch-handles l-l are to be turned round, and a bevel wheel on their shaft 2, acting on another bevel wheel on the end of the upright rod 3, communicates motion to the pulley 4; upon this pulley are attached the ends of two chains, 5, their other ends being connected to the pulley 6, upon the shaft 7; on this shaft is another pulley 8, with the ends of two chains 9-9 fastened to it, their other end being connected to the opposite sides of the axle of the fore-wheels; upon motion being given to these drums, the chains are wound on and off them, and cause the axletree 9-9 to turn out of the right angle to the track of the carriage, thus causing it to travel in a curved line.
At different stations on the road on which the carriage is intended to travel, strong metal reservoirs are to be placed, which are to be filled with atmospheric air, compressed to the required density by a common force pump, worked by steam or water power. From these reservoirs the air is to be passed through proper connecting pipes and cocks into the cylinders b, b contained within the carriage, for the supply of the engines.
Mr. Wright's patent also includes a rotative engine, to be worked by air or steam, for propelling the carriage, which possesses no peculiarities demanding of notice in this place. The claim as to the application of the locomotive power, relates "to the propelling, drawing, or moving wheel carriages by the agency of compressed air, heated and used in the manner above described."