1. 1

2. 2

3. 3

4. VALVES AND VALVE GEAR DESIGN DEPENDS ON
THE ARRANGEMENTS OF THE VALVES IN THE CYLINDER BLOCK OR IN THE HEAD.
THE SHAPE OF THE COMBUSTION CHAMBER
THE ARRANGEMENT OF THE VALVES
UNILATERALLY ALONG THE ENGINES LONGITUDINAL AXI S
BILATERAL CROSS-WISE 4

5. ARRANGEMENT OF THE CAMSHAFT THE TYPE OF TAPPETS FLAT FACE ROLLER
DESIGN DEPENDS ON
ARRANGEMENT OF THE CAMSHAFT
THE TYPE OF TAPPETS
FLAT FACE
ROLLER
BARREL
LEVER 5

6. THE DESIGN OF THE ROKKERS ONE OR TWO ARM ROKKERS
DESIGN DEPENDS ON
THE DESIGN OF THE ROKKERS
ONE OR TWO ARM ROKKERS
THE NUMBER AND TYPE OF SPRINGS
CYLINDRICAL
TAPERED
THE TYPE OF DRIVE FROM CRANKSHAFT TO CAMSHAFT 6

7. VALVE DIMENSIONS 7

8. VALVE DIMENSIONS 8

9. TYPICAL INLET VALVE 9

10. 10

11. VALVE DIMENSIONS 11

12. INLET VALVE DIMENSIONS12

13. VALVE FLOW AREA FOR b = 45 o THE MINIMUM FLOW AREA CAN BE
REDUCED TO THE FOLLOWING RELATION :
WHERE 13

14. STRENGTH CONTROL for valve head thickness
THE HEAD OF THE VALVE IS SUBJECTED TO
UNIFORM MAXIMUM GAS PRESSURE
VALVE SPRING FORCE WHEN VALVE IS SEATED
CONCENTRATED LOAD DUE TO VALVE SPRING : 14

15. STRENGTH CONTROL for valve head thickness
CONCENTRATED LOAD DUE TO VALVE SPRING :
WHERE
P’ = PRESSURE DIFFERENCE BETWEEN THE EXHAUST GAS AT THE EXHAUST MANIFOLD AND THE IN- CYLINDER GAS PRESSURE DURING INTAKE
P1 = MINIMUM PRESSURE REQUIRED BETWEEN VALVE AND SEAT IN ORDER TO AVOID LEAKGAGE
P’ = BAR AND P1 = BAR 15

16. STRENGTH CONTROL for valve head thickness
BENDING STRESS AT VALVE HEAD DUE TO CONCENTRATED LOAD AT CENTER :
STRESS DUE TO UNFORM LOADING :
TOTAL STRESS : 16

17. STRENGTH CONTROL for valve seat
VALVE SEAT IS CHECKED FOR COMPRESSION : 17

18. DEFLECTION OF VALVE WHEN SEATED
VALVE SPRING
DEFLECTION OF VALVE WHEN SEATED
fd= Pretension (m)
i = number of effective turns
G = 8.5 x 107 kPa (Modulus of rigidity )
r = coil radius
dw = spring wire diameter 18

19. VALVE SPRING DEFLECTION OF VALVE WHEN SEATED fd= Pretension (m)
i = number of effective turns
G = 8.5 x 107 kPa (Modulus of rigidity )
r = coil radius
dw = spring wire diameter
fd= hmax
dw = (4 - 5) mm
2r = ( ) . dvi
(choose a rounded figure)
THEREFORE
ROUND OFF TO THE NEXT HIGHER INTEGER VALUE 19

20. VALVE SPRING MINIMUM LENGTH OF COMPRESSED COIL :
FREE LENGTH OF THE SPRING :
CHECKING AGAINST RESONANCE : 20

21. STRENGTH CHECK FOR VALVE SPRING
FORCE APPLIED TO THE SPRING AT MAXIMUM VALVE OPENNING:
MAXIMUM SHEAR STRESS : 21

22. CAMSHAFT
THE CAMSHAFTS OF IN-LINE ENGINES ARE USUALLY PROVIDED WITH SUPPORTS AFTER EVERY OTHER CYLINDER
TAPPETS :
LENGTH TO DIAMETER RATIO 22

23. KINEMATICS OF VALVES CONVEX CAMS
THEY CONSIST OF TWO ARCS WITH RAD I I : 23

24. KINEMATICS OF VALVES TANGENTIAL CAMS
THEY CONSIST OF TWO STARIGHT LINES TANGENTIAL TO THE BASE CIRCLE AND AN ARC
WITH A RADIUS rn 24

25. TAPPET AND ROKKER ARM MAXIMUM LIFT OF TAPPET
ROLLER TAPPETS ARE USED FOR TANGENTIAL CAMS 25