🔍 Key Concepts

• helical vs. double helical (herringbone) gear tooth angles and the forces they create • how axial thrust is produced in a single helical gear • what design features (like dummy pistons and special bearings**) are used to deal with axial thrust in turbines and gears

💭 Think About

• When a single helical gear rotates, which direction(s) do the forces act on the shaft: only around (torque), only radially, or also along the shaft (axially)? • If you have two sets of helical teeth on the same gear, cut in opposite directions (left-hand and right-hand), what happens to the axial forces they each create? • Looking at the answer choices, which one directly relates to what happens to axial forces in the gear set, rather than to separate turbine or bearing design features?

✅ Before You Answer

• Identify which option talks directly about axial thrust in the gear itself, not in other turbine parts. • Ask yourself whether double helical teeth would mainly fix alignment/tooth contact problems or mainly balance out forces along the shaft. • Verify which listed components (dummy piston, spherically seated bearings) are parts of the turbine/bearing system, not inherent features of the gear tooth form.