Learning outcomes
- Place the main engine, thrust bearing, intermediate shafting, stern tube, and propeller in the correct order.
- Explain the difference between transmitting torque, supporting shaft weight, and transferring axial thrust.
- Recognise that the rudder steers the ship but is not part of the torque-transmission chain.
Follow the centreline aft
| Component | Principal function | 3D location |
|---|---|---|
| Main propulsion engine | Produces shaft torque in the training-model low-speed two-stroke arrangement. | Open |
| Thrust bearing | Transfers axial propeller thrust from shafting into the ship structure. | Open |
| Propulsion shafting | Transmits torque between engine and propeller. | Open |
| Line-shaft bearing | Supports and aligns the intermediate shaft. | Open |
| Stern tube | Provides the watertight structural passage for the shaft through the stern. | Open |
| Propeller and rudder | The propeller generates thrust; the rudder develops steering force. | Open |
Power, support, thrust, and steering
Torque follows the shaft line
The main engine turns the shafting, and the shafting turns the propeller. Intermediate and line-shaft bearings maintain alignment and support radial load. Their foundations transfer those loads into the surrounding hull structure.
Thrust must enter the hull
Propeller action creates an axial force along the shaft line. The thrust bearing transfers that force into a foundation and then into the ship structure. It therefore has a different function from a bearing that mainly supports shaft weight.
The stern tube protects the hull boundary
The shaft must pass through the watertight stern. The stern tube forms that structural passage and, in an actual vessel, incorporates bearing and sealing arrangements selected for the specific shaft line. Outside the hull, the propeller works ahead of the rudder in this single-screw arrangement.
Check your understanding
What transfers propeller thrust into the ship structure?
The thrust bearing and its foundation transfer axial propeller thrust from the shaft line into the hull structure.
What is the stern tube?
It is the watertight structural tube through which the propeller shaft passes at the stern, with bearings and seals in a real installation.
Does the rudder transmit engine power?
No. Shafting transmits torque to the propeller; the rudder changes water-flow direction to create steering force.