Question

Which one of the following is the most common type of gear assembly used for coupling steam turbine and propeller shafts?

• A. Spur
• B. Single helical
• C. Double helical
• D. Worm

Hint:

Double helical gears are widely used in marine propulsion systems to balance axial thrust and reduce vibration during high-torque transmission.

Answer 1

The Correct Option is C

Step 1: Understanding gear assemblies in marine propulsion.
In marine applications, particularly in steam turbine to propeller shaft coupling, gears need to transmit high torque smoothly and efficiently while minimizing axial thrust.

Step 2: Evaluate the options.
Spur gears are simple but noisy and inefficient for high-power transmission.
Single helical gears provide smoother engagement but produce axial thrust.
Double helical gears (also called herringbone gears) cancel out axial thrust and offer smooth operation, making them ideal for marine use.
Worm gears are not suitable for high-torque applications like main propulsion systems.