Transmissions Flashcards
The Function of the main gearbox is….?
Change direction
Change speed
Describe the profile of Gear teeth-
Straight cut/ spur
Most common type
Cut so leading edge is parallel to the shaft
Noisy
Describe the profile of Gear teeth-
Helical
Cut at and angle,to allow smoother meshing of gears
quieter
Describe the profile of Gear teeth-
Double Helical
Same as helical but doesn’t need thrust bearings
Describe the profile of Gear teeth-
Worm and Wheel
Where shafts are 90degrees to each other.
Worm is always the driver
Explain how gearwheels change direction & speed
- Direction can be changed by adding a second gear to the first
- Speed can be changed by adding different size wheels
The driving gear/input gear is called?
Primary pinion
The Driven gear is called?
Primary wheel
What is the purpose of the Shaft Brake?
To stop and hold the propeller shaft
What is the thrust block?
it absorbs the force of the propeller so the ship moves ahead/astern
What is Turning gear used for?
Used to slowly rotate the shaft and propeller in a controlled manner for docking & maintenance
What is the Forced lubrication system?
It provides lub to the gearbox
What is the Serckstat?
It directs Hot lub oil through the cooler & allows cool oil bypass the cooler
Name the Hazards associated with Gearboxes
- Noise
- Heat/Fire
- Rotating parts
- (Overalls to be worn & man below tally procedure to be followed)
Plummer blocks are…?
Used to support the weight of the shaft, without absorbing any thrust.
And keeps shaft aligned
What is the purpose of bulkhead glands (Hogging & Sacking)
To maintain watertight integrity as the shaft passes through compartments
what does the Stern Seal do?
Maintains a water tight seal as the shaft passes through the ships hull
Main & Intermediate A Brackets…
Support the weight of the propeller shaft
SKF coupling…
A hydraulic coupling designed so the tail shaft can be split from the intermediate shaft with out leaving a flange
Describe propellers
- Fixed blade
- Blade angle/pitch cannot be changed
- Efficient at full power
- less efficient at low powers & when moving astern
What is single gear reductions
High speed input gets reduced
What is double gear reductions?
Reduces speed further
What are the 3 Brake APPLICATION checks?
- No fire risks
- All brake are applied
- Shaft is stationary
What are the 3 Brake RELEASE checks?
- All Pads are clear
- No fire risks
- Shaft is turning