NAMES 1-RAMY EBRAHEM ABDEL RAHMAN 2-MAHMOUD AHMED ABDEL RAOUF 3-MOHAMED MAGD ALDEEN MOHAMED 4-MAHMOUD LOTFY ELHADY 5-ADEL REFAT ABD ELQADER 6-AHMED MOHAMED

NAMES 1-RAMY EBRAHEM ABDEL RAHMAN

2-MAHMOUD AHMED ABDEL RAOUF3-MOHAMED MAGD ALDEEN MOHAMED

4-MAHMOUD LOTFY ELHADY5-ADEL REFAT ABD ELQADER

6-AHMED MOHAMED ESAM

SUPERVISED BY/

PROF.DR./SAAD ABDELHAMEED

SIDE CAM

2

Single Overhead Cam (OHC)/(SOHC)

Single cam mounted in head.

Opens both intake and exhaust

valves.One cam on an

inline engine and two cams on a vee

engine.

3

Dual Overhead Cam (DOHC)

Camshafts mounted in cylinder head.

One cam opens intake valves and one opens exhaust valves.

Often used with 4 valves per cylinder.

Most high performance of all

types.Vee engines have 4

cams.

4

DOHC

5

Overhead Valve EnginesHas valves in cylinder

head increasing compression.

Camshaft still in block.

Uses lifters, pushrods and rocker arms.

Most common head design until 1990’s.

6

CamshaftsOpens the valves at the

right time.Actually converts rotary

motion to reciprocating motion.

Uses a cam lobe for each valve.

Usually made of cast iron.

Has a great effect on engine performance.

Can be given auxiliary functions like running the

oil pump or distributor.

7

CAMSHAFT CONSTRUCTIONCam lobesCamshaft thrust

plateCam bearingsCam housing and

cam cover

Patent Figures

9

Cam Lobe TerminologyHeel as known as

the base circle.Nose is the tip of

the lobe which determines cam

lift.Opening and

closing flanks and ramps.

Timing points are where the cam

starts to open and close the valve.

10

Cam Lobe LiftThe distance the

valve is pushed open.

It is determined by the height of

the lobe.

11

Cam Duration

This chart is in degrees of

crankshaft rotation.Note when the

valves open and close and on which strokes. This is the

duration.It’s not what it may

seem to be!

12

Camshaft DrivesGear on gearGear and chainBelt and notched

pulleyCam gear ALWAYS

is twice as large as the crank gear, this makes the

cam turn at ½ the speed of the

crank.

13

Gear to Gear Drive

Simplest drive system.

Reliable and strong but noisy.

Reverses Direction of Power 2 times

CW>CCW>CW

14

Gear and Chain Drive

Quieter the gear types.

Allows cam to be further away from

crankshaft.

15

Timing Belt

Used primarily on overhead cam

engines.Uses a kevlar belt.

(police vests)Can snap or stretch

causing catastrophic damage to non-free

running engines.Chains remain more

popular with engine makers.

16

PushrodsMetal rod which transfers force from the lifter

to the rocker arm.

Push Rod The push rod is used to control the

opening and closing of the valve. The push rod is controlled by the cam shaft. As the

rod is pushed up by the lob on the cam shaft, the push rod forces the rocker arm to

open the valve into the combustion chamber .

The push rod is used in engines where the camshaft is located in the block of the

engine .

18

VALVE LIFTERS

Solid LiftersRoller LiftersHydraulic LiftersFollowers

Valve Lifter or Tappet

May be solid, roller, or hydraulicThe lifter follows the cam lobes and

pushes on the pushrodSolid and roller lifters require adjustable

rocker armsHydraulic type lifters fill with oil and

lengthen to compensate for any clearances in the valve system

20

SOLID LIFTERS

21

ROLLER LIFTERS

22

HYDRAULIC LIFTERS

23

FOLLOWERSohc

24

Rocker Arms

Rocker arms are made of stamped steel, cast iron or

aluminum.They transmit the

force of the pushrod to the

valve.Some have

adjusters.

Reciprocating Engine Design and Construction

Rocker Arms

Transmits the lifting force from the cam to the valve.

26

Rocker ArmsRoller- Stamped

Stamped

CastAdjuster

Pivot

Rocker arms•Wear on faces & push rod

sockets•Wear in adjusting screws

•Stamped rockers cannot be refaced •Forged, cast, & fabricated rockers can be

refaced

ComponentMaterialYield Strength (GPa)

Base Plate, Cylinder Head

Aluminum Alloy 29669

Camshaft, Fulcrums, Rocker Arms,

Tappets, Tappet Guides

Cast Iron (ASTM 60)150

Rocker Arm Supports, Rocker Arm Pins

1020 Steel200


Valves


Valves

Fuel/air mixture enters the cylinders through the intake valve.

Burned gases are expelled through the exhaust valve.

Mushroom or tulip type depending on shape.



Valve Construction

Intake valves, because of lower operating temperatures, can be made of chrome-nickel

steel.

Exhaust valves are made of exotic metals such as inconel, silicon-chromium or cobalt-

chromium alloys.


Valve Construction

Head

Face

Neck

Tip

Stem


Valve Construction

Valve head has ground face which forms a seal against the ground valve seat in the cylinder

head.

Valve face ground to an angle of either 30° or 45°.

Valve face made more durable by the application of stellite (an alloy of cobalt and

chromium).


Valve Construction

Valve stem acts as a pilot for the valve head and rides in the valve guide.

Surface-hardened to resist wear.

Some stems are hollow and partially filled with metallic sodium.


Valve Construction

The neck is the part that forms the junction between the head and the stem.

The tip is hardened to with stand the hammering of the valve rocker arm.


Valve Construction

Machined groove near tip receives the split-ring keys which form a lock ring to hold the

valve spring retaining washer.


Valve-Operating Mechanism

Each valve must open at the proper time, stay open for the required length of time, and close

at the proper time.

Timing of the valves is controlled by the valve-operating mechanism.



Intake valves open just before the piston reaches top dead center, and exhaust valves

remain open after top dead center.

At this particular instant both valves are open at the same time (end of the exhaust stroke

and beginning of the intake stroke).

This valve overlap results in better volumetric efficiency and lower operating temperatures.


Valve-Operating Mechanism (Opposed engine)



(Radial engine)


Valve Springs

Function is to

close the valveand to hold thevalve securely

on the valveseat.


Valve Springs

Two or more springs used to eliminate spring vibration or surging during different engine

speeds.

Held in place by split locks installed in the recess of the valve spring upper retainer

washer.


Bearings


Bearings

Any surface which supports, or is supported by, another surface.

Composed of material that is strong enough to withstand the pressure imposed on it.

Permit the other surface to move with a minimum of friction and wear.

Lubricated bearings.


Bearings

Three types of lubricated bearings used:

Plain BearingsBall BearingsRoller Bearings

Bearings are required to take radial loads, thrust loads, and a combination of the two.


Plain BearingsUsed for crankshaft, cam ring, camshaft,

connecting rods, and accessory drive shaft.

Subjected to radialloads.

Made of nonferrousmetals.


Ball BearingsUsed in supercharger impeller shaft bearings

and rocker arm bearings.

Special deep groove ball bearings are used in some aircraft engines to transmit propeller

thrust to the engines nose section.


Roller BearingsStraight roller bearings used where the

bearing is subjected to radial loads only.

Tapered roller bearings used where bearing is subjected to both radial and thrust loads.

Documents

NAMES 1-RAMY EBRAHEM ABDEL RAHMAN 2-MAHMOUD AHMED ABDEL RAOUF 3-MOHAMED MAGD ALDEEN MOHAMED 4-MAHMOUD LOTFY ELHADY 5-ADEL REFAT ABD ELQADER 6-AHMED MOHAMED