201h - Camshaft & Follower Fundamentals Flashcards
Camshaft gear train may also drive what components?
-Fuel injection pump
-fuel transfer pump
-oil pump
-tachometer
-Water pump
What is the role of camshaft lobes?
Convert rotary motion of camshaft into reciprocating motion of cam follower
What is the camshaft lobe nose?
Very top of the cam lobe, maximum lift point.
What is the camshaft base circle?
Base diameter of camshaft lobe. No valve opening.
What is camshaft lobe lift?
Distance cam follower moves as cam rotates.
Lift = Lobe height - base circle
What is camshaft duration?
Number of crankshaft degrees from valve opening to closing.
What are the camshaft manufacturing methods?
- Casting
- Machined or forged allow steel
- Modular
What is the black coating on new cam lobes?
Coating which retains oil to prevent scuffing and promote quick break-in
(Molybdenum disulphide or manganese phosphate)
Where are modular camshafts used?
Large displacement engines for ease of manufacturing and maintenance
What are the two general camshaft locations within an engine?
In-block & overhead
What are 3 benefits of an overhead cam?
- Fewer moving parts
- Less friction
- More accurate valve timing
How are in-block camshaft bushings held in place?
By a press fit
What type of bearings are used in overhead cams where the camshaft is removed vertically off the block?
Shell
Where is the cam thrust bearing located?
Behind the cam drive gear
What controls camshaft end play?
Thrust bearing
How are camshaft lobes lubricated?
- spray from cam bearings
- splashed from valve operating mechanisms
What is the purpose of camshaft followers?
Convert rotary motion of the cam into reciprocating motion as they follow the profile of the cam lobe
What are the AIT 3 basic types of cam followers?
- solid
- roller
- hydraulic
What are the two types of solid cam followers/lifters/tappets?
- Straight body
- Mushroom
Straight body and mushroom are two types of what?
Solid type cam followers
What advantage do mushroom cam followers have?
Greater surface area in contact with the cam lobe. Can withstand higher contact pressure.
What provides the changing wear surface on solid cam followers?
Tapered cam lobe of 0.001”, slight convex bottom face of follower, and an offset centreline.
On what type of cam followers is there a convex face and tapered lobe?
Solid type follower
What do solid followers not compensate for which results in needing regular adjustments?
Regular wear and heat expansion.
What benefits do roller type cam followers have?
Reduces friction, wear, and side thrust
What type of cam follower has reduced friction, wear, and side thrust?
Roller type
From a roller type follower, what benefits are there for the engine? (3)
- Reduced frictional losses
- Can handle higher operating loads
- Quicker rate of valve opening and closing
What are the benefits of hinged cam rollers?
- Eliminate the need for lifter bores in engine block
- Eliminates side thrust
What type of cam roller eliminates side thrust entirely?
Hinged type roller follower
What advantages do hydraulic lifters have?
- Compensate for heat expansion and normal wear, eliminating valve clearance adjustments
- Quieter valve train
How are camshafts driven?
- Gear
- Chain
Do idler gears affect the speed of camshaft rotation?
No
How do idler gears affect camshaft rotation?
No affect to rotation speed
Do change rotation direction
- even # gears = opposite direction
- odd # gears = same direction
What are the two types of cam chains used in heavy equipment?
- Silent
- Roller (stronger)
What is lobe separation angle?
Number of degrees that the intake and exhaust lobes are offset from each other.
What will incorrect camshaft timing result in? (4)
- Altered valve opening and closing points
- Poor engine performance
- Damage to engine components
- Alter fuel injection timing on engine camshaft actuated injectors
