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N the recent evolution of various types of machines for the development of power, it is questionable if even electricity or compressed airor even the much-talked-of steam turbine -has aroused greater interest among mechanical and economic experts than the gas engine as manufactured to-day. While found in more common use in Europe than in America because of the high cost of steam fuel, this type of mechanism has been sufficiently tested by practical operation in the United States to prove its great value. In fact, such has been the progress made in this country in designing gas engines, that machines of this type are now manufactured which develop no less than 4,000 brake horse-power.

The gas engine does away entirely with the boiler house, and transforms over 25 per cent of the heat energy of gas into useful work at the shaft; where

as the efficiency of an ordinary highgrade condensing steam engine is seldom found to be more than 12 or 13 per cent. As modern gas processes have been brought to such a state of efficiency that 80 or 85 per cent of the original heat value of coal appears in producer gas, whereas a boiler efficiency of 70 per cent is regarded as high in steam practice, the basic superiority of the gas engine over the steam engine in high fuel economy may readily be appreciated. The gas engine's special advantages are not alone a minimum fuel and heat consumption, and the elimination of boilers, steam pumps, condensers, return traps, and other steam plant auxiliaries, and of the heat losses and leakage from such auxiliaries, both when the steam engine is in operation and when it is shut down. It has special fields of service, also, in the effective utilization for power purposes of millions of horse-power of blast-furnace

Some of the most advanced types of gas engines operate on what is known as the four-stroke cycle. The piston draws in a mixture of gas and air on the forward stroke, and compresses it to a high degree within the clearance space on the return stroke, whereupon it is ignited by an electric spark. The pressure resulting from the expansive force of the rapidly burning gas mixture drives the piston forward, and the exhaust valves open at the end of the stroke for the escape of the burned gas; while the piston, upon the fourth or exhaust stroke, completely cleans the cylinder, thus preparing for a new charge of gas and air.

gas daily going to waste in the mills of the world, or consumed to poor advantage in the production of steam power; in the operation of high-pressure waterpumping systems for city fire service, wherein it is not economically practicable to maintain constant steam pressure, with service required at only rare intervals; in the equipment of central electric lighting plants operated in connection with large gas works; and in general power application wherever natural gas is abundant.

As already intimated, the efficiency and economy of this type of power generator have been demonstrated beyond question. One series of tests may be cited as an illustration:

A two-cylinder vertical engine of 65 horsepower was kept in operation for 1,157 hours without stopping, and then it was shut off to permit replacing a broken belt. Out of a period of 8,472 hours, it was in motion 8,230 hours. During the time when work was suspended, necessary repairs were made; but these were so slight as to require but 40 hours in all.

In another instance, the performance of a 1,250-horse-power steam station having compound-condensing engines, and a gas engine station of 650 brake horse-power, was compared. The coal used was purchased at the rate of $4 per ton for both stations. It was found that the gas engines, which were of the Westinghouse pattern, could be operated at a saving of 45 per cent in the cost of fuel alone compared with steam, yet performing the same service.

This cycle of operations is repeated in each cylinder. In single-acting engines, pressure is exerted upon only one side of the piston; in double-acting engines, it is exerted upon both sides. The doubleacting arrangement is peculiarly adapted to the driving of large electric generators, especially alternating-current generators working in synchronism upon the same supply circuit.

The accompanying views are of some of the more interesting types of Westinghouse gas engines which were in service at the World's Fair. One is a doubleacting engine having a rated capacity of 200 brake horse-power, while the other is a three-cylinder engine. It will be noted that the double-acting engine has its two cylinders arranged tandem with a common piston-rod, so that the engine gives one power impulse at each forward and backward stroke, as in a steam engine. It operates at a speed of 200 revolutions a minute. The cylinders are 141⁄2 inches in diameter and the length of stroke 22 inches, the maximum diameter of the shaft being 934 inches and the diameter at the bearings 71⁄2 inches. The length of the unit over all is 27 feet 41⁄2 inches; and the width, 13 feet 3 inches. The engine is 7 feet wide, and 8 feet 2 inches high, the fly-wheel diameter being 8 feet.

9 inches. Ignition may be by storage battery, primary battery, or motor-generator set. Because of the tandem arrangement of the cylinders, the fly wheel of the double-acting engine is lighter than that necessary in the single-acting type. Piston and piston-rods are hollow in order that cooling water may be circulated through them, the water entering at the cross-head through a telescopic joint, and emerging through the "tail rod" at the rear of the engine. The starting is a simple matter, readily accomplished by one attendant; and as soon as the engine is fairly started, the combustion cycle begins in the forward cylinder, the air is shut off, and the rear cylinder is thrown into service. Lubrication of the internal working parts, one of the most difficult problems of the internal-combustion engine, is automatically performed by small-power oil-pumps driven from the cam lever.

The three-cylinder vertical gas engine has a rated capacity of 125 brake horse-power, and operates at a speed of 265 revolutions per minute. The cylinders are 13 inches in diameter; and the length of stroke, 14 inches. The maximum diameter of shaft is 72 inches, the diameter at bearings being 61⁄2 inches, and at outboard bearings 54 inches. The length of the unit over all, including fly wheel, is 17 feet 3% inches; and the width 6 feet 9 inches. The engine is feet 4 inches wide, over all; and 10 feet 434 inches high, the fly-wheel diameter being 6 feet.

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sure of the expanding gases. A longtrunk piston is, therefore, employed, thus dispensing with the cross-head. The distinguishing characteristic of the vertical engine is its self-contained construction, all the main moving parts being enclosed in a castiron casing, which is filled with oil up to the shaft, the cranks during their revolution dipping into this oil and furnishing splash lubrication to all internal parts, including connecting rods, pins, and cam shaft, the latter also being mounted inside the crank case.

The performance of the vertical engine is approximately the same as that of the horizontal type, when proper consideration is given to the difference in size and construction, the same working cycle be

The principal difference in construction from that of the horizontal engine, apart from the different arrangement of cylinders, is in the employment of the single-acting principle, in which only the upper side of the piston receives the pres

ing employed in both types. The generator, which was direct-connected to the vertical engine, had a rated capacity of 75 kilowatts, direct current, at 125 volts. It had six field poles, compound-wound; and weighed 8,350 pounds.

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NE of the largest manufacturing plants in the U. S. where armorplate is made is that of the Bethlehem Steel Company at South Bethlehem, Pennsylvania. The works cover an area of nearly 200 acres, and include blast furnaces, puddling mills, Bessemer steel converters, open hearth furnaces, and hydraulic forge press shops, as well as tempering and treating departments, all of which are equipped with the latest labor-saving devices.

The storage plant for the blast furnaces covers a very large area, and is served by an enormous traveling cantilever crane electrically operated. The ore, coal, and coke are delivered by the railroad cars to this crane, the material being dumped from the car through chutes into the bucket, and then simply stored in piles until required at the furnaces. The storage capacity of the plant is about a third of a million tons. The blast-furnace equipment comprises