Technical Drawing - Exam Papers - Ordinary - 2007 - Engineering

Question 3

  (Compressed Cam Assembly)   (Compressed Loci Assembly)

(a) A radial plate cam has a minimum radius of 42mm and a camshaft diameter of 20mm.
The cam rotates in a clockwise direction and imparts the following motion to an inline
knife-edge follower:

0° to 30° Dwell;
30° to 210° Rise 54mm with uniform acceleration and retardation;
210° to 270° Fall 14mm with uniform velocity;
270° to 360° Fall 40mm with simple harmonic motion.

Draw the profile of the cam.
Include the displacement diagram as part of the solution.

(b) Fig. 3 shows a link mechanism. Crank OA rotates in an anti-clockwise direction about
the fixed point O. A and B are pin joints. Crank BC pivots about the fixed point C.

(i) Using a line diagram to represent the mechanism, plot the locus of point P for one
revolution of the crank OA.

(ii) Draw the profile of a simple machine guard about the mechanism with a minimum
clearance of 15mm.

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