FIG. 75.—HERO’S ENGINE, 150 B. C.
The genesis of the steam engine belongs to ancient history, for in the year 150 B. C. Hero made and exhibited in the Serapeum of Alexandria the first steam engine. It was of the rotary type and was known as the “aeolipile.” During the middle ages the spirit of invention seems to have slept, for nearly eighteen centuries passed from the time of Hero’s engine before any active revival of interest was manifested in this field of invention. Giovanni Branca in 1629, the Marquis of Worcester in 1633, Dr. Papin in 1695, Savary in 1698, and Newcomen in 1705, were the pioneers of Watt, and gave to him a good working basis. Strange as it may appear, there was in 1894 and probably still is in existence in England an old Newcomen steam engine (see [Fig. 76]), which for at least a hundred years has stood exposed to the weather, slowly rusting and crumbling away. It is to be found in Fairbottom Valley, half way between Ashton-under-Lyne and Oldham, and is the property of the trustees of the late Earl of Stamford and Warrington. It is erected on a solid masonry pillar 14 by 7 feet at the base, which carries on its top, on trunnions, an oak beam 20 feet long and 12 by 14 inches thick. This beam is braced with iron, and has segmental ends with a piston at one end, and a balance weight at the other. The piston and pump rods are attached by chains. The cylinder is of cast iron, 27 inches in diameter, and about six foot stroke, the steam entering at the bottom only. It was formerly used for pumping a mine.
FIG. 76.—OLD NEWCOMEN ENGINE.
The distinct and valuable legacy, however, which the Nineteenth Century received from the past, was the double acting steam engine of James Watt, disclosed in his British Pat. No. 1,321, of 1782. Prior to this date steam engines had been almost exclusively confined to raising water, but with the invention of Watt it extended into all fields of industrial use. Watt’s double acting engine is shown in [Fig. 77]. It comprised a cylinder A, with double acting piston and valve gear E F G H; the parallel motion R for translating the reciprocating motion of the piston into the curved oscillatory path of the walking beam; a condenser chamber K, with spray I, for condensing the exhaust steam; a pump L J to remove the water from the condenser, and also the air, which is drawn out of the water by the vacuum; a water supply pump N; the automatic ball governor D, and throttle valve B. Two pins on the pump rod L strike the lever H and work the valve gear, and a collecting rod P and crank Q convert the oscillations of the walking beam into the continuous rotation of the fly wheel.
FIG. 77.—WATT’S DOUBLE ACTING STEAM ENGINE.
Watt’s automatic ball governor is shown in [Fig. 78] and its function is as follows: When the working strain on an engine is relieved by the throwing out of action of a part of the work being performed, the engine would run too fast, or if more than a normal tax were placed on the engine, it would “slow up.” To secure a regular and uniform motion in the performance of his engine Watt invented the automatic or self-regulating ball governor and throttle valve. A vertical shaft D is rotated constantly by a band on pulley d. Any tendency in the engine to run too fast throws the balls up by centrifugal action, and this through toggle links f h, pulls down on a lever F G H, and partially closes the throttle valve Z, reducing the flow of steam to the engine. When the engine has a tendency to run too slow the balls drop down, and, deflecting the lever in the opposite direction, open the throttle valve, and increase the flow of steam to the engine. This double acting engine of Watt marks the beginning of the great epoch of steam engineering, and his patent expired just in time to give to the Nineteenth Century the greatest of all natal gifts.