496 



ENGINEERING ON THE FARM 



This pressure forces the gasoline up the desired height, and 

 the gasoline control is usually by means of a float and float 

 chamber similar to that in the gravity system. 



Vacuum system. 

 The vacuum system 



l/oeuurn 

 forth— 



PiP'\ 



I 



/nfoke 

 manifo/o'. 



£= 



Fig. 385. 



"" Mixture 



to combustion 

 — chamber 



(Fig. 385) is a rather 



. 1 recent development. 



reesptpe/ * A vacuum pipe is 



The vacuum gasoline feed system, attached to the in- 

 showing connections , •<• i 1 1 • 1 



taKe manifold which 

 provides a suction sufficient to draw gasoline from a tank 2 

 or 3 feet below the engine and deliver it to a float chamber. 

 From the float chamber the carburetor is supplied as in the 

 gravity system. The vacuum system permits the placing 

 of the gasoline tank in a position that is both convenient 

 for filling and safe with reference to fire. Only a small 

 quantity of gasoline is maintained in the vacuum system 



float chamber, and 

 this is warmed. 



Carburetor. A 

 carburetor is a device 

 for vaporizing vola- 

 tile fuel and mixing 

 this vapor with the 

 proper quantity of 

 air. It requires a 

 large proportion of 

 air to burn vaporized 

 gasoline completely. 

 The best mixture is 

 produced by 62 to 



Fig. 386. Showing the parts of a spray-nozzle or 70 Cubic feet of air 

 atomizer carburetor and their relative positions cubic foot of 



gasoline vapor. The vaporizing of the gasoline is accom- 

 plished by decrease of the pressure, increase of the surface 

 exposed, increase of air movement, and the application of heat. 



Jpray nozz/e 

 float 



Gas#/ine 

 Chamber 



/J/'r/h/et 

 ^//eeo J /e va/re 



