362 



APPLIED SCIENCE 



exhaust pipe. The piston passes through the cylinder four 

 times, twice in each direction. The first mixture of air 



and gas is drawn 

 in during one 

 stroke; then the 

 mixture is ex- 

 ploded ; the force 

 of the explosion 

 starts the next 

 stroke, and on 

 the return the 

 burnt gases are 

 driven out. 

 The heat gen- 



FIG. 178. The Action of a Two-Cycle Engine. 

 The explosive mixture is taken into the crank 

 case through a non-return valve at a on the up 



stroke of the piston. It is compressed on the 



downstroke and allowed to flow into the cylin- 

 der when the piston passes over and uncovers 

 the port 6. The charge is compressed on the 

 upstroke of the engine, is fired and expanded 

 on the downstroke, and exhausted when the 

 piston passes over and uncovers the part c. 



erated 



by 



of 



the 

 the 



D is a deflecting plate to deflect the explosive burning 



mixture toward the top and preventing it from ., . 



going out ate. oil is so great 



that the walls of 



the cylinders would become red hot if water were not cir- 

 culated over them by a pump. The cranks of the engine 

 revolve in an oil-tight case and are dipped in oil so that it 

 will splash up into the cylinder and in this way keep the 

 piston well lubricated. 



408. Principal Parts of a Motor Car. To show the 

 " works" of an automobile it is necessary to remove the 

 body or top of the car. What remains is called the chassis 

 (Fig. 182). 



Starting in front of the seat we see the handle, which is a 

 leve for setting the engine in motion. Underneath the hood 

 is the engine. The lever connects to the engine. Front of 

 the engine is a heavy fly-wheel. The shaft of the engine is 



