Oil Engines. 



443 



valve / being mechanically lifted at the proper time, so that the 

 relative periods of admission of air and of carburetted air are 

 predetermined. On the return stroke of the piston the charge 

 of air and carburetted air are compressed into the combustion 

 space o and the passages or chambers b and i of the carburettor, 

 and the cycle previously explained is repeated. 



To start the engine the ignition tube i is heated by a lamp 

 which is afterwards removed, the heat of the compression and 

 combustion of the working charge maintaining the carburettor, 

 and especially the tube z, at a sufficiently high temperature to 

 cause the ignition of the vapour at the moment of maximum 

 compression. Surrounding the carburettor is a cover n with an 

 air valve at the top, by means of which the temperature of the 

 carburettor may be varied. When adjusted for working, the 

 speed of the engine is controlled by the governor, but the 

 strength of the working charge may be varied by varying the 

 quantity of air entering the vapouriser. 



To enable the engine to be easily started by the attendant, an 

 exhaust controlling device is employed, which holds the exhaust 

 valve m open at first during the whole compression stroke, so as 

 to enable the attendant to get the fly-wheel into motion ; it then 

 allows the exhaust valve to close in sufficient time to retain a 

 working charge, which is ignited, and afterwards automatically 

 allows the exhaust valve to perform its functions normally. 

 The makers arrange the compression and the period of ignition 

 so that even when working at full load the maximum pressure 

 is obtained slightly after the commencement of the piston 

 stroke, and combustion continues during a sensible part of it. 

 The engine consumes from less than three-quarters of a pint 

 of Russolene oil per brake horse-power in engines of about 

 10 horse-power to under a pint per brake horse-power for 

 smaller engines down to 5 horse-power. 



A further example may be given of that type of engine which 

 is made to run without external lamp for igniting the working 

 charge after the engine has been started. This is the engine of 

 fixed and of portable forms made by Messrs. Clayton, Shuttle- 

 worth & Co. It is illustrated sufficiently as to its particular 

 features by Figs. 6 and 7. The fixed engine is shown by Fig. 6. 

 Fig. 7 is a horizontal section of the engine cylinder with its 



