33 FARM MOTORS 



By means of the shorter grates the draft opening is re- 

 duced, and by the aid of the deflector a combustion 

 chamber is produced where all of the light particles are 

 consumed and the gases are heated to an incandescent 

 state before entering the tubes. The direction of draft 

 in this type is nearly always toward the straw, thus caus- 

 ing the heat as it passes the unburned straw to prepare it 

 for better combustion. 



BOILER ACCESSORIES 



450. Supply tank. Boilers used for 

 traction purposes require a small supply 

 'tank to which the boiler pump or the in- 

 jector is connected. This tank is gener- 

 ally placed in some position where it is 

 convenient, yet out of the way. 



451. Siphon or ejector When the 

 supply tank is placed so high that it can- 

 not be filled from a stock tank or other 

 similar source, a siphon (Fig. 225) is 

 generally used. The construction of 

 this is such that a jet of steam is passed 

 into a water pipe leading from the tank 

 or cistern to the supply tank. As the 

 steam comes in contact with the water 

 it is condensed ; this produces a vacuum 

 such that the water rushes in to fill, and 



the inertia due to the velocity of the steam sends it along 

 into the supply tank. 



Care musl be taken in regard to the amount of steam 

 used, since if too much steam be used the water will be- 

 come so warm that the feed pump or injector will not 

 work. 



452. Feed pumps. There are three types of pumps 

 now in use : the crosshead pump, the independent direct- 



FIG. 225 SYPHON 



FOR FILLING SUP- 

 PLY TANK 





