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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

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

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

VALVE DIMENSIONS 7

VALVE DIMENSIONS 8

TYPICAL INLET VALVE 9

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VALVE DIMENSIONS 11

INLET VALVE DIMENSIONS 12

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

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

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’ = 0.2 BAR AND P1 = 0.7 BAR 15

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

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

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

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 = (0.63 - 0.88) . dvi (choose a rounded figure) THEREFORE ROUND OFF TO THE NEXT HIGHER INTEGER VALUE 19

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

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

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

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

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

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