1 74 Book of Engineering 



wasted. It goes without saying that the 

 boiler of a self-propelled vehicle is its most 

 important component, and the greatest 

 attention must be given to its construc- 

 tion. 



The fire-box of the Atkinson- Walker rail 

 tractor is especially efficient; it is made of 

 steel without stays or rivets; it is circular 

 in form, squared in its upper parts to 

 receive the tubes, but its lower flange and 

 firing and clinkering openings are welded to 

 the bottom portion of the outer shell, the 

 top portion of the outer shell, by the way, 

 is removable for cleaning inside. The circu- 

 lation is most rapid, and as the insides of 

 the tubes and the outside of the fire-box 

 can be kept clean, the steaming power of 

 the boiler and its original working pressure 

 remain practically unimpaired during its 

 life-time. The superheater is of rather a 

 unique form, consisting of a solid steel tube 

 placed right in the way of the hot gases. 

 The special firing device mentioned above 

 conduces to coolness in the cab, and totally 

 prevents glare from the furnace. 



