Cams and Followers

A cam drives a flat reciprocating follower in the following manner: During first 120° rotation of cam, the follower moves outwards through a distance of 20 mm with simple harmonic motion. The follower dwells during next 30° of cam rotation. During next 120° of cam rotation, the follower moves inwards with uniform velocity motion. The follower dwells for next 90° of cam rotation. The minimum radius of the cam is 25 mm. Draw the profile of the cam. Determine the maximum acceleration of the follower when the cam shaft rotates at 100 rpm and sketch the acceleration profile nature.

A cam, with a minimum radius of 25 mm, rotating clockwise at a uniform speed is to be designed to give a roller follower, at the end of a valve rod, motion described below: to raise the valve through 50 mm during 120° rotation of the cam; to keep the valve fully raised through next 30°; to lower the valve during next 60°; to keep the valve closed during rest of the revolution i.e. 150°. The diameter of the roller is 20 mm and the diameter of the cam shaft is 25 mm. Draw the profile of the cam when the line of the stroke is offset 15 mm from the axis of the camshaft. The displacement of the valve, while being raised and lowered, is to take place with simple harmonic motion. Determine the maximum acceleration of the valve rod when the camshaft rotates at 100 rpm.

Design a cam for operating the exhaust valve of an oil engine. It is required to give equal uniform acceleration and retardation during opening and closing of the valve each of which corresponds to 60° of cam rotation. The valve must remain in the fully open position for 30° of cam rotation. The lift of the valve is 40 mm and the least radius of the cam is 40 mm. The follower is provided with a roller of radius 20 mm and its line of stroke passes through the axis of the cam.