🔍 Key Concepts

• Medium-speed main propulsion diesel engines and how their crankshafts are constructed • How lubricating oil is delivered specifically to crankpin/crank journal bearings in larger engines versus small/simple engines • The difference between splash, jet, and pressure-fed (drilled passage) lubrication systems

💭 Think About

• Think about the size and power of a medium-speed main propulsion engine. Would a simple splash system be reliable enough for its crankpin bearings? • Which of the listed systems allows oil to be delivered under pressure directly to the highly loaded crankpin and journal bearings? • On a large or medium-speed marine diesel, how is oil usually routed from the main bearings to the crankpins?

✅ Before You Answer

• Identify which option is normally used on small/simple engines versus large/medium-speed marine diesels • Consider which method ensures continuous, positive (pressure) lubrication to the crankpins regardless of engine speed or load • Ask yourself which method is most compatible with an engine-driven lube oil pump feeding through the crankshaft structure