192 SUCCESSFUL FARMING 



diseases which render battery ignition worthless. The most modern 

 engines do not require batteries even for starting the engines. 



Compression ignition is not so common at present in gas engine 

 operation. It may be found upon several recent crude-oil engines, some 

 of which are being used very successfully and cheaply for agricultural 

 purposes. The principle of this ignition depends upon the separation of 

 the heavy and light gases as the fuel is vaporized and drawn into the 

 cylinders with the charge of air. In the compression stroke the lighter 

 gases are ignited by the heat generated by the compression caused by the 

 advancing piston. The light gases in turn ignite the heavier ones. This 

 type of engine not only burns a very cheap grade of fuel, but may be 

 operated with gasoline, kerosene or most any mixture of the fuels used in 

 internal combustion engines. 



Cooling Systems. When a mixture of gas and air is exploded in a 

 gas engine the temperature rises to about 3000 F., which would melt 

 the cylinder of such an engine if a part of the heat was not conducted 

 away in some manner. Some manufacturers use water, some oil and others 

 air for cooling gas engines. Also a mixture of several liquids is some- 

 times used in extremely cold weather to prevent freezing and the conse- 

 quent bursting of the water jacket. Oil, when used for this purpose, 

 takes the place of an anti-freezing mixture. 



Some engines are cooled by water poured around the cylinder in a 

 hopper and the heat conducted from the engine by means of evaporation. 

 Other engines require a circulating pump which causes some liquid to be 

 circulated through the water jacket and thence over a screen where it 

 is partially cooled and used again. There are other types of liquid-cooled 

 engines which depend entirely upon the liquid circulating after the engine 

 is warm enough to cause convection currents. 



The air-cooled engines for agricultural purposes have not proven 

 altogether satisfactory on account of the small radiating surface; also 

 the poor material which enters into the make-up in order that it may sell 

 at a cheap price. 



Lubrication. Graphite is the true lubricant. It is not affected by 

 heat or cold. The reason it is not used more than it is, is because of 

 the inconvenience it offers in passing through small openings which are 

 ordinarily used for oils. A mixture of powdered graphite and oil might 

 be occasionally placed in gas engine cylinders to aid in lubrication, but 

 this could not be depended upon entirely because the operator may for- 

 get when it is time to replace the lubricant. 



All bearings may be lubricated with a cheap grade of animal or 

 vegetable oil, but the cylinders of a gas engine must not be lubricated 

 with any except the best grade of gas engine cylinder oil. The tempera- 

 ture in the cylinder of a gas engine is extremely high; therefore, a vege- 

 table or animal oil would burn and be worthless for lubricating. More 

 gas engines are sacrificed to the god of friction each year than from any 



