Transmissions ⚙️⚙️ Flashcards
What are the main functions of a gearbox?
To speed up, slow down or change directions of the vessel.
What are the main components of a gearbox?
Pinions, wheels, shafts, and bearings.
How do you change the speed of a gear in a gear train?
Change the size of one of the gears/wheels.
Name 4 types of gear profile.
Spur, helical, double helical, worm & wheel.
Explain the construction and advantages of double helical gears?
The teeth in the spurs are cut at an angle, which allows for more teeth to be in contact at any one time, which means it is far stronger. There are two gears cut at opposing angles next to one another. This means that the axial thrust generated from each wheel pushes against one another, which cancels the axial thrust out. The advantage is a high torque can be generated, and it is quieter.
Explain the construction and advantages of the worm and wheel.
The worm and pinion are perpendicular to one another (90°). This allows for more teeth to be in contact with each other. This, in turn, makes it quieter, whilst an extremely high amount of torque can be generated.
State 3 methods of gear reduction.
Single gear reduction.
Double gear reduction.
Dual tandem gear reduction.
Explain the purpose of a quill shaft?
The quill shaft is the hollow shaft that the gears in a gearbox are fixed to. The hollow shaft allows for torsion and flexion, and compensates for misalignment.
State the checks when applying and releasing the shaft brake.
Applying: Pads make contact. Ensure no fires have started. Ensure shaft stops turning.
Releasing:
All pads have stopped making contact. Shaft is turning.
What is the purpose of the thrust block?
The thrust block fixed the shaft itself to the hull of the ship. This stops the shaft from pushing through the gearbox and allows for it to drive the entire ship.
What is the Turning Gear?
The turning gear allows the propeller to turn in small, slow increments and lock it into place when necessary. Such as dry dock.
What is the plummer block?
The plummer block supports the weight of the shaft.
What is the bulkhead gland seal?
The bulkhead gland seal creates a water tight seal where the shaft passes through the bulkhead from one compartment to another. It uses grease and grease nipples to create a water tight seal.
What is the stern seal?
This creates a water tight seal where the shaft passes through the hull of the ship.
What are ‘A-Brackets?’
These are brackets shaped like upside down ‘A.’ The support the external portion of the shaft.
