Question

. CAM DESIGN lower type. Knife-edged follower • Lift = 26 mm • Base circle radius = 28 mm Outstroke: Cycloidal motion for 120° cam rotation Dwell for 750 • Return stroke: Simple harmonic motion for 100° cam rotation • Dwell for the remaining 650 Cam rotates at 600 rpm in CW direction Cam shaft diameter: 18 mm • Cam thickness: 4+1 mm

Please be sure that the SCALE is 1:1

Answer 1

Hi, thanks for the question.

So, as per the conditions given, the outward stroke is 120^$\degree$cycloidal motion, followed by a 75^$\degree$ dwell period, and then followed by 100^$\degree$SHM in inward stroke and then dwells for the final 65^$\degree$stroke.

So, first, we will consider the displacement diagram.

The vertical height of the diagram will be of the length of the follower, i.e. 26mm. Then, we divide the sections into parts depending on the motion of the follower in outward stroke, dwell, inward stroke, and dwell.

Then, we will divide the outward and inward stroke into 6 equal parts vertically to determine the solution accurately. Name the vertical lines in the outward stroke from left to right from 0-6. And then, in the inward stroke, label the vertical lines from left to right from 6-0.

Then, draw a diagonal line in the outward stroke, which goes from top right corner to the bottom left corner, and extends past the bottom left corner. Then, draw a semi circle on the right side of the graph of diameter same as the stroke length, i.e. 26mm.

You will get a figure that looks like this:

4 3 2 0 1 S 6 4 f OUTWARD DWELL =+5° INWARD STROKE = 100 OWELL 65° CS Scann STROKEITEZAM Scanner
Now, divide the semi circle into 6 equal parts, and draw a circle at any point on the extended part of the diagonal. The diameter of that circle will be the length of the follower divided by $\pi$ .

Once that is done, divide the semi-circle into 6 equal parts of 30^$\degree$each, and then divide the circle on the diagonal into 6 equal parts of 60^$\degree$ each. Label them all from 0-6. The points 0 and 6 will fall on the same point on the circle, but the same is not the case for the semi circle. It will have separate sections from 6-0 that will go from top of the graph to the bottom. And you will get something like this.

Now, draw parallel horizontal lines from the semi circle till the corresponding vertical lines in the inward stroke. So, as you join the corresponding lines, you will find the intersection points in the inward stroke for drawing the displacement diagram.

0 4 4 3 2 1 s 6 . a scanneytwap GamScannet INWARD DWELL STROKE = 100'! : 6 sº STROKE

For the outward stroke, draw a horizontal lines to the vertical line passing through the center of the circle, and then, draw diagonal lines from the intersection points on the vertical lines and join them with corresponding vertical lines in the inward stroke. So, for point 0, draw a horizontal line from the periphery of the circle to the center line, and then draw a diagonal line from the point on the vertical line to point 0 on the graph. And then, the graph will look like this:

Then, just join the points to obtain the final displacement curve which will look like the following:

26 4 6 4 3 2 1 si INWARD OWELL OUT WARD DWELL CS Scaftente Caṁ Statsmeri STROKE = 100°

4 3 2 1 2 . 34 S6 > OUTWARD DWELL INWARD STROKE = 100* DWELL 6 Č5 Scansiero weitheamScanner
To draw the cam profile. Draw the base circle with 28mm radius, and then,draw another circle of 9mm radius in the center for the camshaft. Then, from the center, draw a vertical line that cuts the bigger circle in two equal halves. Then, since the follower is not offset, draw it inline with the center of the cam profile. The length of the follower should be 26mm. Then, divide it into the angular paths as per the stroke conditions. 120^$\degree$ outward stroke, followed by 75^$\degree$ dwell, then followed by 100^$\degree$ inward stroke, and then 65^$\degree$ dwell. And you will get something like this:

Then, divide the outward part of the circle and inward part of the circle into 6 equal parts and label them from 0-6 in the outward stroke, and 6-0 in the inward stroke. Then, take a compass and measure the vertical distances corresponding to each label in the displacement graph and cut an arc of the same distance from the periphery of the circle. So, measure the vertical distance of intersection point of line 1 on the vertical line on the inward stroke, and then, cut an arc on the drawn out line 1 from the periphery of the cam profile. Repeat this for all the points, and you will get something like this:

umur=4 Dwebb 65° 120° OUTWARD INWARD 100 779MG est CS Scanned with CamScanner

Finally, just join the points to obtain the cam profile which will look like the following:

unur=4 Dwelli 65° *20° WARD T WWARD + DWELL ?SO و - CS Scanned with CamScanner

P.S. Sorry about that straight section in the cam profile.

h=26 mm DWELL olzi Ty umano INWARD ngo DWELL 75 s CS Scanned with CamScanner