172 Book of Engineering 



the uniflow principle which is simplicity 

 itself, besides ensuring economy ; the engine 

 is easily reversed, and eccentrics, radial 

 valve gear, piston or slide valves are 

 absent. The makers supply their own 

 steam valves (there are no exhausts), and 

 these only require facing, grinding or ring 

 renewal. 



In place of the usual side coupling rods, 

 with their rather complicated joints, we find 

 simple roller chains. The boiler is rather 

 small, of a vertical type, fitted with water 

 tubes; it is especially well lagged and pro- 

 tected from draughts. It is built of steel 

 throughout, and consists of a two-piece 

 welded structure without screwed stays, 

 steam-joints, rivets or crown bridges, and 

 it is so arranged that by breaking two joints 

 it may be taken easily apart for cleaning 

 the steam and water spaces. As far as the 

 fire-box can be made indestructible that of 

 the rail tractor may be so classed, the only 

 parts of the boiler proper which require 

 renewal are the water tubes; these are short 

 and are very easily replaced. 



