Special bearing and shaft mounting equipment must be used with helical gear drives due to the ____ created by the gear drive.

• A. Radial load
• B. Thermal expansion
• C. End thrust
• D. Vibration

Answer: (C)

The main idea is that helical gear drives generate axial forces along the shaft, called end thrust. Because the teeth are cut at an angle, the contact forces between gears have a component that acts along the gear axis. This axial load tends to push or pull the gears and shafts in the axial direction, which standard bearings may not adequately contain. To keep the gears properly meshing, maintain correct alignment, and prevent bearing and shaft damage, special bearing arrangements and mounting equipment are used that can carry this end thrust.

Radial loads are handled by usual bearing design, but they don’t capture the axial component created by the angled teeth. Thermal expansion and vibration can be factors in gear systems, but the specific requirement for special mounting comes from the axial end thrust produced by helical gears.