BOGIE, an under-carriage possessing freedom to move in such a way that wheels can turn or follow a track with the least effort and friction. Familiar examples are those of locomotives, and long carriages, vans, wagons, tenders, and tramcars. There may be two wheels only thus carried, if conditions of length im pose restriction, or the weight does not require four wheels. This type, called a "pony" truck, has a triangular frame, terminating in a pivot some way from the axle, and connecting thus to the main framing. It is employed to a large extent for engines not requiring high speeds. Six-wheel bogies are fitted on very large tenders, and some of the heaviest carriages and vans, but the four-wheel meets ordinary requirements for rolling-stock and lo comotives when the length is too much for rigid wheels. Tramcar bogies often have two pairs of wheels of unequal diameter, the driven axle carrying the larger pair, but in double-motor trucks (four motors per tram) all the wheels are of equal size.
The railway bogie was originated soon after 183o. Some of the first designs had ball-and-socket joints to form the union with the framing, but a pivot pin soon came into favour. Then the Adams bogie was invented, having the pin in a sliding-block controlled by rubber blocks, thus affording a little lateral freedom. This style, but with steel springs, is in great vogue. Another kind of bogie has a swinging link device for lateral play, instead of the sliding action. The "radial axle," with two wheels, is controlled by curved guides in the framing, without pivotal movement.
The diagram represents the features of a four-wheel bogie de signed by Sir John Fowler, K.C.B., for L.M.S. express locomo tives. The casting which turns around the pivot-pin has a cross movement in between castings secured to the frame-plates of the bogie, four powerful springs tending to keep the pin central. The axle-boxes are not sprung with separate coiled springs, as in some instances, but by two centrally-located leaf springs, controlling beams which reach over the boxes. This bogie is rather distinctive from the fact of having four 7in.-bore steam cylinders, operating links which move the brake-shoes on to the 3 f t. 3 tin. diameter wheels, the action taking place simultaneously with the applica tion of the brake-shoes on the driving wheels.
A bogie annealing furnace is a long unit into which piles of material for heat treatment may be carried on low bogies or trolleys, moved along on rails by an hydraulic ram or a crane. The bogies, after a certain period of heating, come out with their loads at the rear end of the furnace for cooling down.