GAS ENGINES 



365 



Brakes. There are usually two brakes on each car a 

 side hand-lever that acts on the axle of the driving wheel 

 and another, operated by the 

 foot, that acts on the trans- 

 mission gear. 



Governor. The speed of 

 the engine may be regulated 

 in three ways by a centri- 

 fugal ball governor. When 

 the speed exceeds a certain 

 limit it either raises the ex- 

 haust valve so that no fresh 

 charges are drawn in, pre- 

 vents the opening of the inlet 

 valve, or throttles the gas 

 supply. The last arrange- 

 ment is the one most com- 

 monly employed. 



Gear-Box. The gear-box 

 of a motor car is very im- 

 portant. An explosion en- 

 gine must be run at a high speed to develop its full power. 

 There are times when a machine must do heavier work 

 than usual, as for example, when it passes from a level 

 road to a steep hill. It accomplishes this task by alter- 

 ing the speed ratio of the engine to the driving wheel. 

 This change in the speed ratio is made possible by the 

 mechanism of the gear-box. 



Spark-Plug. An accumulator and induction coil is an 

 arrangement for producing a spark. It consists of a disk of 

 insulating material mounted on a cam or half-speed shaft 

 with a piece of brass, called a contact piece, attached. A 



FIG. 181. Electrical Gas Engine. 

 Notice the two fly-wheels and 

 the pulley attached on the left. 

 Power is transmitted from the 

 pulley by means of belting. 



