Oil Engines. 



455 



On the compression stroke a portion of the charge is forced 

 through the little passage covered by the valve k> past the 

 valve h and into the igniter, which is, as before stated, filled 

 with asbestos in a containing cage b, by which it is ignited. 

 When running with a load the point of ignition (although this, 

 as will be seen, is automatic), is controlled by the valve k y 

 which is called a timing valve. This timing valve, as well 

 as the vapour valve g, is actuated by the same shaft and 

 governor-controlled cams, and is on the same side as the 

 vapour valve, though for convenience is shown in Fig. 16 on 

 the opposite side. 



For heating the ignition tube for starting, the outer tube wall 

 is turned half round so as to bring the port i at which the air 

 normally enters on its way to the engine, opposite a similar 

 port in the inner tube wall, thus forming a direct passage from 

 the outside to the ignition tube. Into this passage is directed 

 the flame of a Bunsen heating lamp, so that the neck of the 

 igniter is raised to a sufficient temperature to fire a working 

 charge in the cylinder. From this time the asbestos gradually 

 becomes incandescent, and retains sufficient heat without the 

 outside lamp to ignite the working charge at the period of 

 maximum compression, or thereabouts, as controlled by the 

 operation of the vapour valve g and timing valve //. The 

 products of combustion of the heating lamp escape through 

 holes j, and when the lamp is removed the outer tube wall is 

 turned round to the position shown. 



The engine is also fitted with a self-contained starting 

 apparatus ; a cylinder k is placed inside the foundation tank 

 of the engine. At / is a valve opening communication between 

 the vessel K and the engine cylinder. When the engine is at 

 work, the valve being opened and the valve / acting as a back 

 pressure or check valve, a part of the exploded charge can 

 pass into the vessel K, and in this way the vessel may be filled 

 with a gaseous but inert mixture to a pressure of 2501b. per 

 square inch. When a sufficient pressure is shown by the 

 pressure gauge the valve ;// is closed, and no more of the 

 exploded working charge passes into the vessel. For starting 

 the engine it is only necessary, after putting the crank a little 

 above the centre line, to open the check valve quickly by the 



