🔍 Key Concepts

• Direction of firing forces on the piston, pin, connecting rod, and crankshaft in a two-stroke diesel engine • How journal bearings carry load (upper vs lower halves) when the crankshaft is under power • Difference between main bearings and connecting rod bearings in transmitting combustion forces

💭 Think About

• Trace the path of the combustion force from the piston crown all the way to the crankshaft and bedplate—where is the force ultimately reacted? • Think about which half of a split bearing (upper or lower) is actually compressed when the engine is producing power and the crank is being pushed around its rotation. • Consider whether any bearing in the system would realistically see the same load as all others, or if some particular location must carry the highest reaction.

✅ Before You Answer

• Identify which bearing surface (upper or lower half) is on the loaded side of the crankshaft during the power stroke. • Verify which component is responsible for supporting the crankshaft in the block versus connecting the piston to the crank. • Check whether the connecting rod bearing and piston pin bushing carry the same type and magnitude of load as the main bearing that supports the crank throw.