REQUISITES OF A HIGH-SPEED LOCOMOTIVE.
The first essential for a high-speed locomotive is the means of generating steam freely as fast as it is used up by the cylinders. The next consideration is properly designed steam-distribution gear, and well-proportioned machinery, so that the heat energy produced by the boiler may be converted into useful work in propelling the engine with the least possible loss of power. To handle the fast trains between New York and Philadelphia, the mechanical talent of the Pennsylvania Railroad, aided by fifty years’ inherited experience, has produced the form of engine known as Class K. This is an anthracite-coal-burning locomotive, with 1,205 square feet of heating-surface to supply steam to cylinders 18 inches by 24 inches, which turn two pairs of coupled drivers 78 inches in diameter. The traction force of the engine is thus (182 × 24)/78 = 99.69 pounds for each pound of effective pressure per square inch of the pistons. The valves are the plain slide, with 1¼ inch outside lap, no inside lap, 1/16 inch lead in full gear, and a full travel of 5½ inches. The steam-ports are 16¾ inches long and 1½ inches wide; while the exhaust port is 3¼ inches wide, securing free emission of steam.