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646 hearth steel, heat-treated forging. Each main section carries two cranks for a 4-cylinder and three cranks for a 6-cylii:der engine. Integrally forged flanges are provided at both ends. The two main sections are interchangeable with each other. The third section carries the cranks for driving the scavenging pump and air compressor and is equipped with an_ integral flange for bolting to the main section, All corners are filleted. The shaft is bored to permit examination of the THE MARINE REVIEW the main bearing caps which are fitted and rigidly bolted to the bed plate. Seats for the bottom half shells are aligned before the shells are placed in position. After the shells are seat- ed in place, they are scraped to the crankshaft for alignment. The flywheel is carried on an ex- tension shaft which is connected to the crankshaft by a solid forged coup- ling flange. The flywheel rim is pro- vided with slots to facilitate barring over the engine by motor. The out- December, 1920 through the scavenging pump is m Hig.' 13, suction and discharge valves the "shutter" type mounted in cages. These valves are interchange- able. The intake side of the pump is provided with a valve chest arranged so that the scavenging air may, if de- sired, be brought from outside the engine room. The discharge side ig provided with a valve chest with con- nections to the scavenging air ceiver which, in turn, provides section shown The are of re- the FIG. 12--BED PLATE WITH LOWER material and to afford a passage for the lubricating oil, The shafts are made to specifications especially cover- ing the class of steel and quality of manufacture required for marine serv- ice. The main bearings are cast iron, made in "halves, cylindrical in shape and lined with babbitt which is an- chored and tinned in place. The bot- tom half shells are fitted and. scraped into bored seats in the bed. The top half shells are fitted into bored seats in the bearing caps. Between the two sections, shims are provided to furnish means of adjustment. The shells are securely held in place by BEARING SECTIONS IN PLACE--THESE ARE SCRAPED TO BRING THEM IN ALIGNMENT board bearing which is combined with the thrust bearing, supports the ex- tension shaft beyond the flywheel and is carried by a section bolted to the main bedplate. The scavenging pumps of 4-cylinder engines for providing low pressure scavenging and charging air for the working cylinders, are mounted verti- cally on the crankcase at the opposite end from the flywheel, next to the forward working cylinder with which it is in line. They are directly driven from the cranks on the extensions to the main crankshaft and are provided with crossheads and guides similar to those in the working cylinders, A connection to the working cylinders. The scavenging air receiver is cast iron extending along the front of the engine and is bolted to faces on the working cylinder jackets. It provides a firm support for the gears, camshaft bearings and The receiver is fitted with a pressure relief valve. The and discharge valve chests are fitted with large cov- to. the valve casings. suction access ready ers to provide The is equipped with covers for access to valves. scavenging air receiver the rotary scavenging valves. ne "Hie providing compressed air for fuel injection and vertically on compressor for for starting, is placed