LOGGING LocomoTtrEs. The locomotives or dinarily known as logging locomotives are of two types. One is built after the general pattern of the four-wheeled switching locomotive, with the exception that the wheels have broad grooved tires a foot or so in width that are adapted to running upon a track formed of logs placed end to end. The other is known as the Shay loco motive and is fitted to run on ordinary rails. Such an engine is shown in rig. 10. It is built on three four-wheeled centre-bearing swiveled trucks, the wheels of which are driven by bevel gearing attached to the right-hand wheels of each truck with steel pinions meshing into them, carried by a shaft running in hearings attached to the journal-boxes, and extending from axle to axle of each truck. The power is communi cated in these pinion shafts with flexible coup lings extending from the engines, which are placed vertically on the side of the boiler. This arrangement leaves each truck free to adjust it self to curves and irregularities of the track.
The three trucks lucre spoken of include the tender truck. which is a driving truck also. The trucks are built of steel, are equalized, and have coiled springs. The object of this construction is to have the shortest possible rigid wheel-base and the longest possible flexible wheel-base, thus utilizing all the weight for traction. It is possi ble to work the locomotive on very sharp curves, the one illustrated running easily on a 65-degree curve. Its use is confined to roads having heavy grades and sharp curves, and it is restricted to low speeds. The frames of both engine and tender are made of 10-inch I-beams, one on each side, that of the engine being strengthened by a truss-rod as shown. Steam brakes are provided to act on part or all of the drivers, either separately or together.