🔍 Key Concepts

• Force path in a large low-speed, crosshead diesel engine during the power stroke • Difference between members that are in tension vs in compression • Structural role of tie rods, piston rod, and attached fasteners in holding the engine together

💭 Think About

• Trace the gas pressure acting on the piston crown and follow how that load is transmitted down through the moving parts to the crankshaft—on which part is the load pushing, and on which parts is it pulling? • For each option, decide whether that component is mainly designed to resist compressive forces or tensile forces during firing. • Look at where the crosshead and piston rod meet in the illustration: when the piston is forced downward, which element is being squeezed, and which elements are being stretched to keep the structure together?

✅ Before You Answer

• Verify which component directly connects the piston/crosshead assembly to the crankshaft during the power stroke. • Check which parts (like long vertical rods) are specifically intended to hold the frame and bedplate together against upward firing loads—these are usually in tension, not compression. • Confirm that small items like nuts or lubrication devices are not primary load-carrying members under firing pressure but mainly serve retaining or lubricating functions.