🔍 Key Concepts

• How power flows through a double-reduction gear train from the high‑speed turbine shaft to the low‑speed propeller shaft • The difference in size and speed between a pinion and a bull (or main) gear • Which component in the sketch is clearly the largest gear and which ones are the small driving pinions

💭 Think About

• Trace the path of rotation: which gears would logically be on the high‑speed side and which on the low‑speed side? • Compare the diameters in the illustration: what does a very large diameter gear usually indicate in a reduction gear set? • Ask yourself: is the part labeled IV driving other gears, or being driven by them, and what does that tell you about its role?

✅ Before You Answer

• Identify all the small gears vs. large gear in the picture before choosing • Decide which labeled component would be connected to the propeller (low‑speed) shaft in a marine reduction gear • Make sure your choice for IV matches the usual definition of a bull gear / first or second reduction gear in marine propulsion systems