American Locomotive American engines had their truck axles as near together as they could be placed, which would answer for engines with inclined cylinders, but was not necessary when the cylinders were put lower down and made horizontal. The most commonly-used engine truck in America is thai designed by Rogers about 1850, the frame being rectangular, with pedestals bolted to it, and having a pair of bent equalizing levers on each side and the spring between the wheels, each spring having its convexity upward and bearing at its middle against the lower edge of the frame, while its ends draw from points about midway between the centre and the ends of the equalizing lever. About 1852 there was introduced a truck which had journal bearings inside and out side of the wheels, and springs to each journal, there being double springs and two equalizing bars on each side of the truck.
Bissell or Pony 1857, previous to which time all trucks were centre-bearing, Bissell patented the truck since known by his name. The first Bissell truck had four wheels (p1. too, jigs. 16, 17), its distinctive features being that the frame was extended backward, and the pin, instead of being in the centre of the truck, was behind the rear axle (C), so that the entire truck, instead of making a partial rotation around its centre, made a vibration about this point behind the rear axle; the weight of the engine being taken by a pair of V-shaped inclined planes where the old centre bearing had been. The object of this arrangement was to enable the engine better to adapt itself to the curves of the track. In 1858, Bissell introduced the single-axle or " pony " truck, with the same vibrating fea ture. In 1862, A. P. Smith substituted for the inclined ways of the Bissell truck a set of pendent links to allow the engine to have lateral motion, the engine resting upon a bolster swung from the truck. Hudson in 1864 brought out a variation of the Bissell-Smith truck, using a long radius bar pivoted at its front end to a pair of lugs attached to the centre pin plate of the engine, the back end having some motion, but being confined by a guide. A very important invention was that of Hud son in 1864, in which an equalizing lever was placed between the two-wheeled truck and the front driving-wheels, so that these accom modated themselves to the vertical as well as to the lateral motion of the engine.
1834, Baldwin patented the improvement of cast ing together the hub and the spokes of the drivers, the spokes terminating in separate flanges or segments of a rim having wooden felloes, outside of which came the tire. For altering wide-gauge to narrow-gauge drivers, where the change of gauge in the road is expected at the time that the engines are built, Rogers casts a circular projection on the inside of the wheel-centres. The tires are then set to conform to the wide gauge.
When the time collies to change the gauge the tires are simply moved farther in to cover the projection, and the portions of the centres thus exposed on the outside of the wheel are turned off, which leaves the wheel seats in proper condition for the narrow gauge. A driving-wheel for an American locomotive is seen in Figure 15 (p. 100). It is made of good strong, close-grained iron. The counterweights are generally cast in; the rim and arms are solid or cast hollow as desired. Both the rim and the counterweights are divided in several places to diminish the inherent strains due to cooling.
Equalizing the wheels of early American locomo tives there were used ordinary equalizing levers, their method of attach ment and arrangement varying according to the design of the engine and the fancy of the builder. The main features of the leading system at pres ent are elliptical leaf-springs, which have their convexity downward, and which arc attached at their outer ends to links drawing on the bar of the frame, and drawing at their inner ends on a lever which also draws on the frame at its centre. By this means any excess of draft of the leading pair of drivers is partly thrown upon the springs of the following pair, and rice versa. For narrow-gauge engines Rogers uses a long lever extending from pedestal to pedestal, and having the two links drawing upon the two ends of the spring, which has its convexity upward and which thrusts against the lower edge of the frame. For "Consolidation" engines the spring over the central driving-axle bears at its centre upon that axle, and its ends draw on the inner ends of two levers, the other ends of which receive the pull of the inner ends of the springs of the first and third axles, while the outer ends of the springs of these last axles draw upon the top of the frame. Good examples of equalizing levers are seen in Figures it to 13, being respectively main, truck, and pony-truck levers. In 1834, Bald win patented a method of throwing a part of the weight of the tender upon the driving-axles to increase the traction, and thus to make up for the tractive advantage that Norris had by having the drivers in front of the fire-box. Baldwin proposed to equalize the pressure between the two driving-axles by connecting by a pipe two air-springs on each side. East wick and Harrison patented the equalizing beam.