Diesel engines for land and marine work . ver, which contains only one valve, thisbeing the ordinary fuel inlet valve in the centre of the valve is of the same type as that described for thesmaller Polar engines. The motor is practically of the open type, and naturallyowing to the arrangement of scavenge pumps, there is anexternal crosshead and connecting rod. The cylindersare supported at the back by means of a cast-iron framingcarrying also the guides for the crossheads, and at the frontby cast-steel columns, as with some other motors, notablythe Sulzer type and also the Werkspoor
Diesel engines for land and marine work . ver, which contains only one valve, thisbeing the ordinary fuel inlet valve in the centre of the valve is of the same type as that described for thesmaller Polar engines. The motor is practically of the open type, and naturallyowing to the arrangement of scavenge pumps, there is anexternal crosshead and connecting rod. The cylindersare supported at the back by means of a cast-iron framingcarrying also the guides for the crossheads, and at the frontby cast-steel columns, as with some other motors, notablythe Sulzer type and also the Werkspoor engine. The important feature of using the scavenging cylindersfor starting purposes is retained in this motor with theresult that not only is the simplest possible design of coverobtained, but also the undesirable admission of cool air CONSTRUCTION OF DIESEL MARINE ENGINE 237 into the heated combustion chamber during manoeuvringis avoided. The method involves a certain complicationin connexion with the valves for the scavenge cylinder,. Fig. 117.—Xear View of Cam Sliaft of 800 Polar Diesel :\Iarine Engine. but otherwise has much to commend it. The arrangement,however, can be reduced to comparative simplicity inoperation, since when starting up there is a two-way valve 238 DIESEL ENGINES FOR LAND AND MARINE WORK which shuts ojff the admission of atmospheric air into thescavenge pump, and allows compressed air at a pressure ofabout 75 lb. per sq. inch to enter the scavenging cylinderbeneath the piston, and start up the engine. The admissionand discharge valves on the scavenge pumps are mechanic-ally operated by means of eccentric rods from a horizontalspindle driven off the crank shaft. Although the pressureof the starting air in the scavenge pump only needs to be75 lb. per sq. inch it is supplied from res&rvoirs at 150 sq. inch to a reducing valve to bring it down to thedesired figure. For the operation of the fuel valve in the cylinder coverthere is one lever fo
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