🔍 Key Concepts

• Crosshead vs. trunk pistons – note how the connecting rod is attached and whether there is a separate piston rod and crosshead bearing • Single-acting vs. double-acting – look for whether pressure acts on one side or on both sides of the piston crown • Pay attention to the right‑hand vs. left‑hand views in the illustration; they show two different piston arrangements

💭 Think About

• First decide: does this piston have a separate piston rod going down to a crosshead, or is the connecting rod pin located inside the piston skirt? What does that tell you about crosshead vs. trunk? • Then ask: is there any combustion or working space below the piston as well as above it, or is the working space only above the crown? How does that affect single‑acting vs. double‑acting? • Which of the four answer choices matches BOTH of the features you’ve just identified (type of piston AND acting type)?

✅ Before You Answer

• Identify where the gudgeon/wrist pin is located: inside the piston with the connecting rod directly attached (trunk) or in a separate crosshead (crosshead). • Confirm whether there is any pressure-tight sealing and working space on the underside of the piston crown (which would indicate double-acting) or only on the top side (single-acting). • Match your observations to the exact wording of the choices – you must correctly pair trunk/crosshead with single/double acting.