Chapter 5

Question 1

List the two functions of the crankshaft:

Answer 1

Converts the reciprocating motion of the piston and connecting rods to rotary motion.
Drives camshaft and engine accessories.

Question 2

What is the purpose of the internal drillings of the crankshaft?

Answer 2

The internal drillings provide a path for oil to flow from the main bearing journals to the connecting rod journals.

Question 3

Crankshafts used in medium and high speed diesel engines are usually:

Answer 3

one piece forged alloy steel

Question 4

The crankshafts used in diesel engines are usually hardened to improve wear characteristics of the:

Answer 4

Journals

Question 5

List four factors that determine the arrangement of the throws on a crankshaft:

Answer 5

Number and arrangement of the cylinders.
Firing order.
Engine balance.
Main bearing loads.

Question 6

Determine the number of degrees between firing impulses on a two stroke cycle engine with sixteen cylinders.

Answer 6

22.5 Degrees.

Question 7

Determine the mating cylinders on a four stroke cycle, eight cylinder engine with a firing order of 1-5-4-8-6-3-7-2.

Answer 7

1/6, 5/3, 4/7, 8/2

Question 8

An unbalanced engine would have reduced:

Answer 8

Mechanical efficiency.

Question 9

List 3 basic functions of the flywheel:

Answer 9

Smoothes out engine operation by storing and releasing engergy.
Carries the ring gear.
Provides a mounting and friction surface for the clutch assembly.

Question 10

The balance weights used in some four stroke cycle diesel engines:

Answer 10

Counterbalance inertia forces generated by the piston and assemblies.

Question 11

List two types of vibration dampeners used on diesel engines:

Answer 11

Rubber element.

Viscous.

Question 12

Briefly explain the purpose of a vibration dampener.

Answer 12

The vibration dampener counteracts or opposes the twisting forces acting on the crankshaft, reducing torsional vibration.

Question 13

The front and rear crankshaft seals:

Answer 13

Prevent splash oil from leaking out around the rotating crankshaft.

Question 14

List two functions of the crankshaft gear:

Answer 14

Transfers power from the crankshaft to drive engine components and accessories.
Time the crankshaft to the camshaft.

Question 15

List two types of friction bearings used in diesel engines:

Answer 15

Bushing.

Shell.

Question 16

What is bearing spread?

Answer 16

The small extra distance across the parting faces of a bearing half in excess of the actual diameter of the bearing bore.

Question 17

Locating lugs and dowels are used to:

Answer 17

Position bearing shells in the main bearing bore.

Question 18

List the four basic properties that friction type bearing materials must posses.

Answer 18

Embeddability
Conformability.
Fatigue resistance.
Corrosion resistance.

Question 19

Briefly explain the purpose of bearing crush.

Answer 19

The press fit that seats the two bearing halves to provide good heat transfer and keep them from rotating in the bore.

Question 20

What is the purpose of an oil spreader groove?

Answer 20

An oil spreader groove aides in oil distribution across the bearing face.

Question 21

What is the purpose of bearing clearance?

Answer 21

Bearing clearance allows oil to flow between the bearing surface and the shaft.

Question 22

List the two purposes of the oil film between the bearing and the crankshaft journal.

Answer 22

Reduces friction.

Carries heat away from the bearing and the journal.

Question 23

Maintaining the film of oil between the bearing and the crankshaft journal is dependent on engine oil pressure and the principle of:

Answer 23

Hydrodynamic lubrication.