MARINE ENGINES.

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taking the joint at the bottom of the trunk. In this way amplebearing surface is obtained, and the shaft is not so liable to befractured as when the strain is re-ceived on the middle. The eccen-trics should also be placed as nearthe main bearings in the head-stock or top frame for taking theshafting as can be convenientlydone, as the strain on the inter-mediate shaft is thereby betterdistributed.

The feed and bilge pumps aresometimes worked off a double

lever arm, fitted to the end of the trunnions; this plan necessitatesa large diameter of pump, having a very short stroke, owing to thelength of the vibrating arm. This arrangement does not make so

Fig. 228.—Cranked Shaft for Air Pump .

S Cranked shaft. b, Main bearing. c, Bearingfor eccentric. d, Crank pin for air-pump rod.e, Part for the piston-rod crank.

' |“ !

O O

Fig. 229.—Feed and Bilge Pumps .

a, Feed pump, b, Bilge pump, c, Rocking arm and rods. d, Plunger and stuffing box.e, Suction valve. f, Discharge valve. g, Relief valve and spring.

effective a pump as when the stroke is increased, giving less dia-meter of plunger, which can be readily attained by placing thepumps on each side of the air pump, and connecting them to thecrosshead fitted to the top of the trunk, when they have the same

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