328 



FARM MOTORS 



worked by a lever in 

 such a manner that all 

 fine ashes will drop 

 through. 



448. Straw burners. 

 For burning straw there 

 must be special arrange- 

 ments within the fire 

 box. The fuel is light 

 and generally chaffy, 

 and as a result flashes 

 up very quickly, and un- 

 less prevented will be 

 carried by the draft 

 some distance through 

 the tubes before it is all 

 aflame. Not only this, 

 but straw must be 

 burned rapidly in order 

 to produce heat enough to make steam as fast as needed. 

 To handle straw under these conditions, the return-flue 

 boilers are generally constructed similar to the type 

 shown in Fig. 223: a is an extended fire box with a drop- 

 hinge door ; b is the upper grate ; and c is the lower grate, 

 where as much of the straw as is not burned in the upper 

 grate, or as it falls from it, is consumed ; d d are deflectors 

 which hold the flames next to the upper side of the flue. 



FIG. 221. END VIEW OF RETURN-FLUE 

 BOILER 



FIG. 222. ROCKER GRATED 



