4 BULLETIN 480, U. S. DEPARTMENT OF AGRICULTURE. 



not exceeding 40,000 pounds. The pump is attached to the engine by 

 a durable clutch, with gear and pinion. Connected with the pump 

 are two automatic safety release valves, one set at 300 pounds and 

 the other at 350 pounds. By having two release valves a variation 

 of pressure can be obtained from 275 pounds to 375 pounds without 

 making any change in the release valve and not running the engine 

 at an excessive rate of speed. These valves are properly set and 

 should not be adjusted in the field. 



THE ENGINE. 



The engine is a 4-cycle, water-cooled type, having four cylinders, 

 with a maximum of 14 horsepower, and is equipped with a high-ten- 

 sion magneto, and so oiled as to require little attention from the en- 

 gineer. The cooling system consists of a coil of pipe submerged in 

 the spray tank and fed by a supply tank located near the engine. 

 The gasoline tank has a capacity of 10 gallons. The agitator consists 

 of three long paddle blades extending the entire length of the tank 

 and has proven more satisfactory than single propeller blades. 



The safety or release valve is so arranged on the delivery line that 

 the solution is automatically released into the spray tank whenever 

 the nozzles are shut off. The piping, wherever subjected to high pres- 

 sures, is extra heavy, with double-strength fittings, and is so arranged 

 on the pressure side that the solution may be delivered into the hose 

 for spraying or diverted into the tank when filling. The suction 

 line is arranged so that the solution may be drawn directly from the 

 tank or water from the suction hose when the tank is being filled. 



While this arrangement is not essential in spraying work, it enables 

 this apparatus to be used for other purposes, such as fighting 

 fires, etc. 



THE HOSE. 



Hose used in high-power solid-stream spraying should be con- 

 structed to stand a working pressure of 600 pounds, with couplings 

 especially adapted for high-power work. Hose used in this work 

 not only has to stand high pressures, but is also subject to severe 

 strain in pulling and hauling that is necessary especially in wood- 

 land spraying. Unless a very high grade 10-ply hose is used, with 

 heavy inner tube and outer walls, it is advisable to have 7 or 8 ply 

 hose covered with a cotton jacket treated to prevent mildew and in- 

 crease wearing quality. It is also advisable to use high-grade hose, 

 whether covered or not, as the life of it will be so extended as to re- 

 duce the yearly cost to a considerable extent. Couplings should be 

 constructed so as to make it impossible for them to blow off under 

 pressure and to offer as little resistance as possible when the hose 

 is being pulled. In woodland spraying parts protruding from cou- 



