🔍 Key Concepts

• Identify from the illustration whether this is a slow‑speed crosshead two‑stroke or a four‑stroke trunk piston engine • Recall how camshaft speed relates to crankshaft speed in a two‑stroke vs a four‑stroke engine • Determine whether the propeller shaft is directly coupled to the crankshaft (no reduction gear) on this type of engine

💭 Think About

• From the crosshead, piston rod, and arrangement shown, what type of diesel engine is this likely to be? • On that type of engine, how many crankshaft revolutions occur for one complete cycle, and how fast must the camshaft turn relative to the crankshaft to time fuel and valve events correctly? • If the propeller is directly driven by the crankshaft on this engine type, what does that tell you about the relationship between propeller RPM, crankshaft RPM, and camshaft RPM?

✅ Before You Answer

• Confirm the engine cycle: 2‑stroke vs 4‑stroke using features visible in the illustration (crosshead, scavenging air receiver, etc.) • Check whether there is any reduction gear between the crankshaft and propeller in this arrangement • Match the camshaft speed to the proper fraction or multiple of crankshaft speed required for correct valve/fuel timing before selecting among 135 or 270 RPM or a variable speed answer