The endeavor is made to effect the compensation of the disturbing motions above mentioned by at least a partial application of the required counter-weights and by equalizing beams or double lever-like parts, which uniformly distribute the weights and pressures. In Figure 5, for instance, an equalizing lever is placed in a notch in the frame above the coupling rod, between the coupled driving-wheels, for the reception of the one-sided spring pressures of these wheels, while Figure 2 (a/. 97) and Figure 6 OM 9S) show the counter-weights fastened in the driving-wheels.
Weigla and Tractive Power. —The locomotives built by A. Petzholdt weigh np to too,000 kilogrammes (t to tons), and are constructed with an adhesion-weight (pressure against the tracks) of from 25,000 to 30,000 kilo grammes (27;! to 33 tons) if intended for passenger trains, and with an adhesion-weight of from 30,000 to So,000 kilogrammes (33 to SS tons) if intended for freight trains. They exert on the peripheries of their driv ing-wheels a tractive power of, respectively, 2500 and 6000 kilogrammes (2:,;f and 6 tons), and have an effective capacity of, respectively, six hun dred and four hundred horse-power, that of a locomotive for passenger trains being, therefore, greater than that of one for freight trains, which is due to the greater speed of the first. Formerly, two hundred horse-power was considered an average of effective capacity.
Substitutes for Adhesion-weigh!: Fars System—The expedient of using magnetism instead of weight-adhesion has frequently been tried, but without success. The use of a sand-box, as shown in Figure (pi. 98), where it is in the shape of a cylinder close over the frame behind the smoke-box, for sanding the rails to increase the coefficient of friction, amounts to little more than a palliative and serves only for occasional emergencies. Another of the many expedients tried is the use of a cen tral rail with a locomotive constructed on Fell's system. Figures I and 2 (pl. ro4) show such a locomotive and track. Four horizontal wheels (two on each side) are pressed against a high central rail by a spring mechanism (rep resented half in section in the ground-plan in Figure 2). These are moved by a twin-engine so that the balanced compressing strains do not depress nor displace the central rail. There are two coupled driving-wheels, and the engine is a tender-locomotive with water-tanks on the side of the boiler over the frame. This locomotive was constructed for a temporary
road over Mont Cenis before that mountain was tunnelled, but it has many practical defects. On the railroads ascending the Riga and the Kahlen bergs, near Vienna, a return was made to the historical initial point— namely, a central rack-toothed rail. Locomotives with corresponding spur-gear wheels were used, this being necessary ou account of the enor mous grades. (See Vol. V., p. 233.) The form and even the dimensions of the steam-engines used in locomotive construction have undergone but little change since Robert Stephenson's time. Two practically horizontal cylinders are placed either on the outside, as in Figures 3 to 6, 8, to, and II (pl. 98), or on the inside, as in Figures I to 3 (pl. 97) and Figures I, 2, and 7 (p1. 98). The pistons, moving alternately backward and forward therein, generally drive directly, by means of piston-rods and connecting-rods, a crank-shaft, which is the principal driving-axle, and on which in most cases is placed the eccentric acting on a link-motion (usually Stephenson's). In Figures 5, 8, and (pl. 98) the eccentrics are outside, a construction by no means suitable.
saddle-tank on the top of the boiler has the disadvantage of not holding very much, and as the water-supply diminishes, the weight upon the drivers diminishes also, so that at one time there may be upon them too much weight, and at another there may be too little weight. Three types of American locomotive tanks are shown in Figures 3 to 5 (pi. too).
5 and 6 (pi. ror) show two tenders, the first of the ordinary American type, but the latter with the special provision that the water-tank can be filled without stopping the train. For this purpose a long water-trough is placed between the rails on a horizontal stretch of the track. In the interior of the water-tank of this tender (invented by Ramsbottom) is a pipe over an aperture in the bottom, and another which can be either pressed against this aperture or turned from it. This second pipe being dipped into the water-trough while the train is running, the water is scooped up and the tank filled by the momentum of the train and the inertia of the water.