STEAM AND GAS ENGINES 



211 



from exploding gas only at every other rotation of the 

 fly wheels. The energy 

 stored in the fly wheels 

 by one explosion keeps 

 the machinery running 

 until another explosion. 

 High power gas engines 

 have two or more cylin- 

 ders in which explosions 



occur alternately, thus GAS ENGINE 



the loss of power and 



speed between explosions is avoided. The best auto- 

 mobile engines have from six to twelve cylinders which 

 insure a continuous supply of power and not by jerks 

 as given by a single cylinder engine. The development 

 and perfection of the gas engine have made the auto- 

 mobile a very effective machine and have also made it 

 possible for aeroplanes to fly with considerable safety. 



The diagrams illus- 



E- ' 



trate the operation of 

 one cylinder of a gas 

 engine. In No. i a 

 mixture of gas and air 

 is being drawn into the 

 cylinder through the 

 valve as the piston, P, 

 moves to the right. In 

 No. 2 the valves are 

 closed, and the piston moving to the left compresses the 

 mixed gases. In No. 3 just as the piston starts to move 

 to the right an electric spark which ignites the gas is 

 made in the cylinder, and an explosion results which 

 drives the piston to the right with considerable force 



3. Explosi 



4. 



PRINCIPLE OF THE GAS ENGINE 



