42 ANNUAL OF SCIENTIFIC D1SCOVEKY. 



her serves also to keep the axle-boxes at all times in close contact with the 

 faces of the horn 1 docks, so as to secure a good lit, and obviate the neccssiry 

 for that constant lining which they ordinarily require, in consequence of the 

 wearing away of the working- faces. 



That the leading and trailing wheels may have still further flexibility of 

 adjustment, a small play is permitted to the axle-box laterally, in the direc- 

 tion of the axle, by making the recesses in the axle-box, which receive the 

 face-plates, wider than the plates themselves by ^ inch. But to keep the 

 axle-boxes in position in straight portions of the road, these plates are made 

 wedge-shaped in plan, so that the elastic pressure of the india-rubber on the 

 face-plates restores the axle-boxes to their central position, whenever the 

 pressure on the flanges of the wheel is relieved. The inclination of the 

 wedge is made such that 1 inch movement of the axle-box laterally, in 

 either direction, cQmpresses the india-rubber -^ inch. 



The india-rubber is employed in the form of rings or washers if inch 

 thick.; and it is found convenient, in order to maintain an accurate fit be- 

 tween the working surfaces of the axle-boxes, that these washers, when in 

 position, should be compressed T 3 S inch, which is equivalent to a pressure of 

 about one ton on each side of the axle-box, tending to maintain the contact 

 of the working surfaces. With this pressure, the axle-boxes slide more 

 freely on the case-hardened surface of the plates, than in the usual construc- 

 tion; whilst the motion which permits the wheels to accommodate them- 

 selves to the curvature of the road does not in the least increase the oscilla- 

 tion of the engine, and prevents the excessive wear of the shoulders of the 

 journals and the flanges of the wheels, which are such fertile causes of 

 unsteadiness in ordinary engines. 



In the case of the driving-wheels of the engine, it is not advisable to allow 

 so much play to the axle-boxes; and hence, while the admirable fit between 

 the working surfaces obtained by the above arrangement renders its employ- 

 ment advantageous, it is modified in this case by the use of a band of india- 

 rubber, 12} by 2i inches, and | inch thick, covered by a wrought-iron plate, 

 case-hardened as before, but not wedge-shaped, since in this case all lateral 

 play is to be avoided. A longitudinal play of -yV inch only is allowed on 

 each side^, between the case-hardened plate and the horn-blocks, to permit 

 the action of the india-rubber spring, which is compressed in this case, so as 

 to exert an initial pressure of about fifteen tons on each side of the axle- 

 box, to resist the action of the force driving the engine. Notwithstanding 

 this large pressure on the working faces of the box, it is found, in practice, 

 to fall readily with the weight of the wheel itself. In the case of the driving- 

 wheel, the advantage derived by this construction does not consist in the 

 adjustment given to the wheels, but in the perfect fit at all times maintained 

 between the sliding surfaces; the elasticity of the india-rubber also forms an 

 elastic cushion to receive the shocks of the machinery. A small strip of 

 leather prevents the oil from gaining admission to the india-rubber. The 

 perfect freedom of motion, the small wear of the axle-box, in consequence of 

 the case-hardening of the slides, the ease with which the engine passes curves, 

 and the diminished wear of the wheel-flanges, are important advantages, 

 which have been derived, in practice, from this construction of axle-box. 



A similar application of an india-rubber spring to the outside coupling-rods 

 of an engine had also been made. In this construction of rods, the use of 

 cotters for tightening the brasses was dispensed with, by employing a set- 

 screw at the end of the rod, secured by a lock-nut from risk of working 

 loose. 



