TRACTION ENGINES 437 



which are of the locomotive type, having the engine 

 mounted beneath the boiler. These are known as under- 

 mounted engines. 



581. Boiler mounting. There are four general methods 

 of mounting the boiler. The most common method is 

 to attach the drive wheels to brackets at the side of the 

 boiler and is known as side mounting. Another common 

 method is to mount the drive wheels on an axle at the 



FIG. 3l6 SIDE-MOUNTED PORTABLE ENGINE 



rear end of the boiler and is known as rear mounting. 

 As a rule, the return tubular boilers are mounted on an 

 axle which passes beneath the boiler. This style of 

 mounting is given no special name, but might be called 

 under-mounted boilers. There is now on the market a 

 type of mounting which might be known as frame mount- 

 ing; that is, there is a frame to which the drive wheels are 

 attached, and it also supports the boiler. 



582. Side mounting. Fig. 316 shows the method of 

 side mounting a portable engine. This is similar to a 

 great many side-mounted traction engines. Fig. 



