Crankshaft and Related Components Fundamentals Flashcards
Crankshaft Nose
Usually at the front of shaft and is a mounting surface for the gear and vibration damper/hub
Crankshaft Journal
Are the load bearing surfaces of the crankshaft, has main and rod journals
Crankshaft Throw
The distance from the centerline of the main to the centerline of the rod
Crankshaft Web
Connects the main and rod journals to form the throw of the crank
Crankshaft Fillet
A rounded corner between the journal and the web, helps reduce stress of crank compared to square corners
Crankshaft Counterweight
Masses of metal located opposite the rod journals
Crankshaft Flange
Usually located on rear of crank and is the mounting surface for the flywheel
Crankshaft Oil Passages
Internal drillings in the crank that provide a path for oil to flow from the main journals to the rod journals
Crankshafts are usually manufactured in one of what two ways?
- Casting
2. Forging
What method is commonly used to harden crankshaft journals?
Induction Hardening - heated by electromagnetic induction and then quenched
Diesel engine crankshafts are usually manufactured from?
Forged Alloy Steel
The relative position of throws on a crank are determined based on what factors?
Number and Arrangement of cylinders
Firing order
Engine balance
Main bearing loads
Nitriding
A chemical surface treatment that may be used to harden the journal surfaces
Some of the effects of an unbalance engine are?
Run rough with excessive vibration and stress on components
Have reduced mechanical efficiency
Inertia forces
Forces created by the acceleration and deceleration of the piston and con rod assembly
Inertia forces are greatest at?
TDC & BDC
Unbalanced couple
The result of two forces acting in opposite directions and in different planes
Flywheel
Heavy mass of steel attached to the rear flange of the crankshaft
Flywheels are matched to the engine based on what?
Number of cylinders
Displacement
Application
What is the purpose of a vibration dampener?
To counteract or oppose the torsional forces acting on the crankshaft
What are the two types of vibration dampers commonly used on diesel engines?
Rubber element
Viscous
What are the two main functions of the crankshaft gear?
Transfers power from the crank to drive engine components and accessories
Time crankshaft to the cam and rest of motor
What are the two common ways the crankshaft gears are attached to the crankshaft?
Pressed on and keyed
Bolted to a flange
Crankshaft oil seals
Commonly referred to as front and rear main seals. Seals used in diesel engines are normally a one-piece lip seal
What are the 3 basic purposes of friction type bearings?
Reduce friction between the moving parts of an engine
Support and maintain the alignment of a shaft or component
Provide a durable and replaceable wear surface
Common bearing types
Bushing - Can be either full round or seamed
Shell type
Thrust - Can be either separate washers or part of the bearing shell
4 basic properties that the material used in engine bearings must possess
Embeddability
Conformability
Fatigue resistance
Corrosion resistance
Embeddability
Ability of the bearing lining to material to absorb dirt or hard foreign particles that are suspended in oil
Conformability
The ability of the lining material to conform to shaft for minor damage and slight mis-allignment
Fatigue resistance
Ability of a bearing to withstand continual loading without breaking down
What are the 3 common layers found in a multi-layered bearing ?
Backing layer
Inner Layer
Overlay
Bearing spread
Free spread diameter is the extra distance across tje parting faces of the bearing half
Is necessary is ensure proper seating of the bearing on the bore
Crush relief
Bearing is tapered slightly at the parting line to provide relief from crush pushing bearing towards shaft at parting line
Bearing grooves
Annular grooves
Spreader grooves
lateral groove
Thrust face
Hydrodynamic lubrication
When the shaft acts as a pump forcing oil between the shaft and bearing surface
Crankshafts used in medium and high speed diesel engines are usually:
One piece forged alloy steel
List the four factors that determine the arrangement of the throws on a crankshaft?
- Number and arrangement of cylinders
- Firing order
- Engine balance
- Main bearing loads
What are the 3 basic functions of the flywheel
- Smoothes out engine operation by storing and releasing energy
- Carry the ring gear
- Provide a mounting and friction surface for clutch assembly
What are the 2 purposes of the oil film between the bearing and the crankshaft journal?
- Reduce friction
2. Carries the heat away from the bearing and journal
