312 RAILWAY CONSTRUCTION. 



wear of the tyres, and of the inside of the rail-heads clearly 

 demonstrate the enormous amount of friction and abrasion that 

 takes place. 



Fig. 477 represents a type of eight-wheel-coupled engine 

 designed for hauling passenger or goods trains over long lengths 

 of heavy mountain inclines. The engine is a large one in every 

 way, and of great total weight, but the weight is distributed 

 over a long wheel-base and without imposing a greater tonnage 

 per pair of wheels than is done in some of the smaller and less 

 powerful engines. The flanges are turned off the leading pair 

 and third pair of coupled wheels reducing the rigid wheel-base 

 for curves to 9 feet 8 inches. The four-wheel bogie truck in 

 front carries only a moderate weight, being so close to the 

 coupled wheels. Engines of this description require a strong 

 permanent way, as there is a total weight of 60 tons on the four 

 pairs of coupled wheels standing on a wheel-base of 15 feet 

 6 inches. 



Figs. 478 and 479 are types of tank-engines in use on some of 

 the narrow-gauge (3 feet) railways. In general design they are 

 somewhat similar to the modern class of engine on main lines of 

 4 feet 8 inches gauge, with four-wheel bogie truck in front, and 

 four wheels or six wheels coupled, but with all the parts and 

 weights smaller, to suit the narrow gauge and lighter permanent 

 way. 



The extended use of the bogie truck is an admission of its 

 advantage over the fixed-wheel arrangement, both for distribu- 

 tion of weight and facility in passing round curves; but although 

 it is now so largely adopted for engines and carriages on our 

 home and continental railways, it is somewhat of an anomaly to 

 find it so very rarely used for tenders. In the United States all 

 the locomotive tenders and many of them of very large size 

 and weight are carried on two four-wheel bogie trucks, and 

 traverse the curves as easily as the engines. On this side of the 

 Atlantic, the prevailing custom is to mount the tender on six 

 rigid wheels ; and as many of these tenders weigh as much as 

 from 35 to 40 tons in working order, and have a rigid wheel-base 

 of 15 feet, it will be seen at a glance that much unnecessary 

 friction and wear and tear would be avoided by substituting two 

 four-wheel bogie trucks for the fixed wheels. 



