Transmissions

Question 1

What are the main functions of a gearbox?

Answer 1

1. Transmit power from the prime mover to the shaft
2. Allow for variations in speed and power
3. Allow for changes between ahead and astern thrust

Question 2

What are the main components of a gearbox?

Answer 2

pinions
wheels
shafts
bearings

Question 3

How do you change the speed of a gear train?

Answer 3

Add wheels to the train of different sizes smaller to higher the speed and larger to slow it down the max ratio is 15:1

Question 4

How do you change direction of a gear train?

Answer 4

Add another wheel

Question 5

State 4 type of gear profile.

Answer 5

Straight spur
Helical
Double Helical
Worm Wheel

Question 6

Explain the construction and advantages of a double helical gear.

Answer 6

Each pair of gear wheels with opposing angled teeth form a “V” that produces thrust in both directions that cancel each other out. They can be directly interchanged with spur gears without any need for different bearings

Question 7

Explain the construction and advantages of a worm gear.

Answer 7

Worm gears can be used in application where the shafts are at 90̊ to each other. The worm gear, resembling a screw with a continuous tooth forming parallel helical teeth, mates with a Spur gear.
When placed correctly the worm acts like a safety device when it loses power it slows an locks in place

Question 8

State the three methods of gear reduction.

Answer 8

Single gear reduction
Double gear reduction
Double gear reduction duel tandem

Question 9

Explain the purpose of a quill shaft.

Answer 9

A quill shaft is a thin, solid shaft which is designed and machined so that it carries the same torque as a larger shaft by operating at higher stress levels, carrying torque the quill shaft acts like a torsional spring, twisting along its length. By having the ability to move, load can be evenly distributed and any misalignment can be compensated for.

Question 10

State the checks when applying and releasing a shaft brake.

Answer 10

• Ensure no fire risk exists
• All Brake Pads are APPLIED
• The shaft is stationary
• All Pads are clear/released
• No fire danger exists
• The shaft is turning

Question 11

Where can the shaft brake be operated from?

Answer 11

The shaft brake can be operated from the control room or from the local position

Question 12

What are the main components of a gearbox?

Answer 12

pinions
wheels
shafts
bearings

Question 13

How is the gearbox oil kept at the correct temperature?

Answer 13

Serckstat

Question 14

How often are the FL cut-ins checked and at what pressure will they energise the MD pump?

Answer 14

they are checked everyday and energise the MD pump at 18.5psi

Question 15

What is the purpose and construction of the Thrust Block?

Answer 15

Thrust Block contains a Thrust Bearing and is mounted just after the gearbox on the Thrust Shaft

It’s purpose is to absorb the forces by the action of the propeller and transmit the to the ship’s hull, so that the ship moves ahead / astern

Question 16

What is the purpose and construction of the Turning Gear?

Answer 16

The turning gear is used to slowly rotate the shaft and propeller It is mounted on top of the gear case and provides drive onto the upper quill shaft in the gearbox.
It uses a worm and wheel the worm is always driving not driven

Question 17

What is the purpose and construction of the Plummer Block?

Answer 17

Plummer blocks are used to support the weight of the shaft, within the ship, without absorbing any thrust

They are lubricated by dynamic lubrication, using oil from an oil bath. A plummers block has bearings, a casing, a dipstick, journal pads and an oil cooler.

Question 18

What is the purpose and construction of the Bulkhead Gland Seal?

Answer 18

The purpose of the bulkhead glands is to maintain watertight integrity as the shaft passes through compartments, without absorbing any thrust

It has a white metal lined bearing, lubricated with grease forced in via grease nipples

Question 19

What is the purpose and construction of the Stern Seal?

Answer 19

The Stern Seal maintains a water tight seal as the shaft passes through the ship’s hull. It is fitted to the inboard end of the stern tube and is a mechanical seal. An inflatable seal is used in an emergency should the normal sealing arrangement fail. It consists of a neoprene seal which is inflated to form an interference fit on the shaft, thus preventing water ingress. It will only work when the propeller shaft is stationary.

Question 20

What is the purpose and construction of the A – Brackets?

Answer 20

These brackets take no actual thrust but support the weight of the propeller shaft. Lubrication of the bearings in the brackets is by sea water using the Hydro-Dynamic principle

Question 21

What are the main components of a Plummer block?

Answer 21

A plummers block has bearings, a casing, a dipstick, journal pads (individual supports with white metal bearings) and an oil cooler

Question 22

What principle does a Plummer block use for lubrication?

Answer 22

dynamic lubrication

Question 23

What substance does a bulkhead gland seal use and how is it inserted?

Answer 23

It uses grease and is fitted with grease nipples

Question 24

What is fitted to a stern seal in the event of an emergency?

Answer 24

An inflatable seal is used in an emergency should the normal sealing arrangement fail

Question 25

What do the A brackets use for lubrication?

Answer 25

sea water using the Hydro-Dynamic principle

Question 26

What are the three sections of shaft Line?

Answer 26

Tail Shaft is connected to the Intermediate Shaft with a SKF Coupling, Intermediate shaft is connected to the Thrust Shaft with bolted flanges

Question 27

How are the thrust and intermediate section connected?

Answer 27

with a SKF Coupling

Question 28

How are the intermediate and tail section connected? And explain how this connection works.

Question 29

What are two main types of propeller used?

Question 30

What Hazards are associated with a Transmission System?

Question 31

Draw the Shaft Line Layout diagram.