1887. 2-8-0 CLASS R
IN 1885 the Pennsylvania Railroad designed and built at its Altoona Shops a new class of Consolidation engine for freight service. It was so successful that a considerable number were built both by the company's shops and the Baldwin Locomotive Works up to the nineties. These were the Class R (new classification H3) locomotives. They are particularly interesting in that they had the first Belpaire boilers to be used on Pennsylvania Railroad motive power.

Cylinders 20 by 24 inches Total weight 114,620 pounds Driving wheels 50 inches in diameter Weight on drivers 100,590 pounds Total wheelbase 21 feet 9 inches Rigid wheelbase 13 feet 10 inches Tractive force 22,850 pounds

The lower section of the illustration shows a cross section of the same locomotive and gives an idea of its various parts. The principles of a steam locomotive's operation are, of course, the same today as always and to the uninitiated perhaps a short resume of their functions might be interesting.

The illustration does not show the grates or firebox but they are located above the ash pan. The sides as well as the back of the firebox have "water spaces" so that as much heating area as possible is provided. The tubes in the boiler, a few of which are shown, are for the same purpose. Steam is taken from the highest point in the steam dome, being controlled by the throttle valve. From this the steam pipe takes it to the cylinders, the slide valves in the steam chests above them controlling its admission into each end alternatively and thus acting on the piston. The eccentrics shown on the third axle may be set by means of the reverse lever to control the slide valves, both for forward motion or reverse. This method has been superseded by the present external "valve gear" used on more modern engines, but its purpose was the same.

For supplying water to the boiler, the injector is used. This forces water into the boiler by means of a steam jet. A steam cylinder operates the air pump which automatically maintains a fixed pressure in the air reservoir. This supply of compressed air is used for the brake system and all the brakes on the train are simultaneously controlled with the engine brakes. Dry sand kept in the sandbox is applied to the rails if they are slippery or to help adhesion when starting.