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Monday, March 14, 2011

AU2354 DESIGN OF CAM PROFILE & CAM SHAFT


AIM:-

 To design the cam shaft using design procedure and draw it using AUTOCAD 2000.

Function


To open and close the inlet and exhaust passage by operating the valves using valve train mechanism components


HARDWARE USED:-

1.128 MB RAM

2.20 GB-Hard disk

3. Mouse, Key board etc


SOFTWARE REQUIRED:-

AUTOCAD 2000

 

MATERIALS:


Medium carbon alloy steel

Production process

Drop forging and machining 


DESIGN PROCEDURE FOR CAM SHAFT:-

If

1. 2 cams are available in between two journals (or) supports of cam shaft=camshaft dia dc = 0.3 B
2. 4 cams are available in between two journals (or) supports of cam shaft=camshaft dia dc = 0.35 B
3. 8 cams are available in between two journals (or) supports of cam shaft=camshaft dia dc = 0.4 B

Assume,

 Maximum permissible deflection of the cam shaft under input load due to valve opening = 0.075 mm

we know that,
   y =PL3 / 6 EI [2x4 + 2x2 - 4x3]

Where

P = maximum impact load
L = distance between center of two journals
E = young’s modulus
I  = moment of inertia of the cam shaft
= p / 64 (Dc) 4
x = xL / L

xL  = calculate from crank shaft diagram
L  =  calculate from crank shaft diagram

From crank shaft diagram
L1 = [(front main journal length of crank shaft / 2) + (flange thickness) + (thickness
          Of Short crank arm) + (flange thickness) + (length of first crank pin / 2) +
          (C.D) + (Length of second crank pin / 2) + (flange thickness) + (thickness of
           Short crank arm) + (flange thickness) + (length of intermediate main journal of
Crankshaft / 2)]

Assumption:

                    Center of the front journal of crank shaft lies on the center of the front journal of cam shaft(length wise)
                    Similarly center of the intermediate journals of the crankshaft and cam shaft lies on the same axis.
                    Similarly center of the rear journal of the crankshaft and cam shaft lies on the same axis
                    Center of the crank pin (length wise)must be the center of the cylinder bore

L1 = distance between the center of the front to main journal of the crank shaft and
        intermediate main journal of the crank shaft

L2 = distance between the center of the intermediate journal and rear main journal of
         the crank shaft

       X L1 = distance between the center of the front journal of the cam shaft and center
            of the exhaust cam of the second cylinder.

         XL1= L1 - [Intermediate journal length of crank shaft / 2 + (flange thickness) +
           (Thickness of short crank arm) + (flange thickness) + crank pin length / 2 –
            5 – Exhaust valve head / 2]

        XL2 = distance between the center of the front journal of the cam shaft and center of
            the exhaust cam of the third cylinder.

         C.D = the center distance between two crank pins

        C.D = B / 2 + t + (water jacket thickness) + t + B / 2



DESIGN PROCEDURE FOR CAM PROFILE:

1. Thickness of piston bead (or) crown is calculated from the strength and beat dissipation consideration.

Cam profile is usually constructed in complaints with the chosen law of profile formation .In order to obtain cams relatively simple to manufacture modern tractor and automotive engines the following types of cams.

1. Convex

2. Tanqential

3. Concave

4. Harmonic

A tangential cam profile is formed by means of 2 st lines which is tangential to the base circle of radius (or) a + points A and A' and arc having radius (r2)

1. The cam profile is constructed, starting with a lease circle. Its radius is chosen to meet the requirement of providing enough rigidity of the valve gear with in the limits.

Vo = (1.5 to 2.5) hv max


2. The valve of camshaft angle is determined by selected valve timing

= For 4 stroke engine

Where

=          Advance angle

=          Angle of retarded closing

Point A & A' are the point at which the valve starts its opening and closing.

Point B is found by the valve of max follower lift

3. Neglecting last motion, if any while with over bead valve engines and the used of rocker arm.


Where,

lf & lv are the length of rocker arm to the follower and valve respectively.

(lf / lv)= 0.5 to 0.96


4. The cam nose radius is given by

                    To provide a clearance in the valve gear. The cam beal is made to radius less than     the radius to by the valve of the clearance is rc =ro – s



The valve of and an elastic deformation of the valve gear

= 0.25 - 0.35 mm for inlet

= 0.35 - 0.5 for exhaust


Conjugating the circle of radius rc should have to having radius r1 and st lines of tangential lines is parabola arc have certain radii

Cam width 0.9(dia of cylinder hole) mm

Outer diameter of cam shaft=2 x ro+ 2 mm

Inner diameter of cam shaft =>10mm is used for calculating lubricating oil to the cams and to ensure sufficient rigidity.





DRAWING PROCEDURE:-

  • After opening the drawing file, the limits are used.
  • According to the design, the drawing of the camshaft is drawn using, line, filler are used region is created.
  • The cam shaft is drawn in 3D and dimensioned
  • The finished drawing is saved in drawing files.

 


DESIGN OF TAPPET:


Minimum foot diameter:-

Minimum foot radius,

R1= √ (Wc /2)2 + (Rf - Rb) 2 sin 2  q


RESULT:-

 Thus the designs of camshaft using design procedure and drawing using AUTOCAD 2000 software.








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