🔍 Key Concepts

• Remember that in a reduction gear train the pinion is always the smaller member that drives the larger gear. • In a two-stage (double) reduction: the first reduction handles the highest speed from the turbine, and the second reduction is closer to the output (bull gear/propeller shaft). • Look at how the shafts line up: the turbine (high‑speed) shaft, the quill/intermediate shaft, and the main/bull gear shaft.

💭 Think About

• On which shaft would you expect the highest speed, smallest gear (pinion) to be located in a double reduction gear set? • Compare the diameters of the parts labeled I, II, III, and IV. Which ones are clearly gears (large) and which are pinions (small)? • In the gear train shown, trace the power flow from the turbine to the propeller: where does it enter first, and which labeled part does it contact at that first stage?

✅ Before You Answer

• Confirm that pinions are the smaller driving members and gears are the larger driven members in each reduction pair. • Identify which member is involved in the first stage of speed reduction (closest to the turbine) versus the second stage (closest to the bull gear/propeller shaft). • Make sure the label "I" is on the component that matches both its relative size (pinion vs gear) and its location in the train (first vs second stage) before choosing.