🔍 Key Concepts

• Trace direction of rotation from the propeller back through the reduction gear to the turbines • Each gear mesh reverses direction of rotation between the two gears that are in mesh • Relation between a right‑hand propeller’s ahead/astern rotation and the turbine astern element when the ship already has sternway

💭 Think About

• If a right‑hand propeller is producing astern thrust, which way must it be turning when viewed from astern, and how does that compare to when it is producing ahead thrust? • Starting from the propeller shaft, count each meshing gear in the illustrated train back toward the high‑pressure astern turbine: after an even vs odd number of meshes, is the final gear rotating the same or opposite direction as the shaft you started from? • Compare the high‑speed gear on the high‑pressure side with both the low‑speed pinion on the low‑pressure side and the high‑speed gear on the low‑pressure side—how many meshes separate each pair?

✅ Before You Answer

• Be clear about your viewpoint in the picture (aft end vs forward end of the reduction gear) before deciding on clockwise vs counterclockwise • Carefully identify which gear is the high‑speed gear on the high‑pressure side and which is the low‑speed pinion on the low‑pressure side in the illustration • Verify that you have correctly counted the number of gear meshes between the shafts you are comparing so you know whether their rotations match or are opposite