power train

Question 1

main reduction gears (MRGs)

Answer 1

main propulsion turbines operate most efficiently at several thousand RPM. Shafts revolve most efficiently up to 200 RPM. Gears mechanically slow the propulsion shaft

Question 2

double helical (reduction gear)

Answer 2

two sets of gear teeth cut across the face of the gear, at opposite but complementary angles. Stronger, quieter and eliminates axial thrusts

Question 3

double reduction ( reduction gear)

Answer 3

speed reduction takes place in two separate steps. High speed pinion is first reduction gear. Low speed pinion is the Bull gear which allows for smaller MRG

Question 4

Locked train (reduction gear)

Answer 4

Each speed pinion drives two first reduction gears. distributes power equally to the bull gear. ensures equal lubrication across all gears

Question 5

articulated (reduction gear)

Answer 5

long gear shafts absorb more torque. short gear shafts are better suited for small spaces. effectively lengthen the gear shaft without actually increasing the space the gear set occupies. 1st reduction gears are connected to the 2nd reduction pinions by an internal shaft

Question 6

journal bearings

Answer 6

also known as shaft bearings. support the shaft radially, prevent sagging or bowing. constructed of a hard shell with a softer inner Babbitt

Question 7

thrust bearings

Answer 7

support the shaft axially. Pushes it forward or pulls it back. kingsbury design

Question 8

lube oil tolerance of purity

Answer 8

loses lubricating properties over time. due to contamination by foreign substances/chemical breakdown. dirt, water, sludge

Question 9

lube oil tolerance of pressure

Answer 9

system pressure maintains steady lube oil supply to all components

Question 10

lube oil tolerance of temperature

Answer 10

lube oil moves through a closed system. removes heat from bearing surfaces

Question 11

newton’s third law of motion

Answer 11

for every action there is an equal and opposite reaction

Question 12

controllable pitch propeller

Answer 12

ability to hydraulically turn each propeller blade on its own axis. Ship can move ahead or astern without reversing direction of the shaft rotation

Question 13

fixed pitch propeller

Answer 13

blades of prop are fixed in place. ship moves astern by reversing direction of shaft rotation

Question 14

cavitation

Answer 14

extreme low pressure on back of propeller blades. Seawater then vaporizes at low-pressure points and forms a spiral trail of bubbles that emerge from each blade tip. As vapor bubbles move into regions of higher pressure

Question 15

cavitation damage

Answer 15

results in loss of efficiency and pitting of the propeller