Tutorial 2
.docx
School
University of Management & Technology, Lahore**We aren't endorsed by this school
Course
MECHANICAL 101
Subject
Mechanical Engineering
Date
Jan 9, 2025
Pages
3
Uploaded by mubashiranjum23
Page 1of 3School of EngineeringMechanical Engineering DepartmentBachelor of Science in Mechanical Engineering Subject: Mechanics of Machines ME224Tutorial # 21.A cam is to give the following motion to a knife-edged follower: 1. Outstroke during 60° of cam rotation; 2. Dwell for the next 30° of cam rotation; 3. Return stroke during next 60° of cam rotation, and 4. Dwell for the remaining 210° of cam rotation. The stroke of the follower is 40 mm and the minimum radius of the cam is 50 mm. The follower moves with uniform velocity during both the outstroke and return strokes. Draw the profile of the cam when (a) the axis of the follower passes through the axis of the cam shaft, and (b) the axis of the follower is offset by 20 mm from the axis of the cam shaft.2.A cam is to be designed for a knife edge follower with the following data: 1. Cam lift = 40 mm during 90° of cam rotation with simple harmonic motion. 2. Dwell for the next 30°. 3. During the next 60° of cam rotation, the follower returns to its original position with simple harmonic motion. 4. Dwell during the remaining 180°. Draw the profile of the cam when (a) the line of stroke of the follower passes through the axis of the cam shaft, and (b) the line of stroke is offset 20 mm from the axis of the cam shaft. The radius of the base circle of the cam is 40 mm. Determine the maximum velocity and acceleration of the follower during its ascent and descent, if the cam rotates at 240 rpm.3.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 : 1. To raise the valve through 50 mm during 120° rotation of the cam ; 2. To keep the valve fully raised through next 30°; 3. To lower the valve during next 60°; and 4. 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 (a) the line of stroke of the valve rod passes through the axis of the cam shaft, and (b) the line of the stroke is offset 15 mm from the axis of the cam shaft. 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 cam shaft rotates at 100 rpm. Draw the displacement, the velocity and the acceleration diagrams for one complete revolution of the cam.4.A cam drives a flat reciprocating follower in the following manner: During first 120° rotation of the cam, 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 simple harmonic motion. The follower
Page 2of 3dwells for the next 90° of cam rotation. The minimum radius of the cam is 25 mm. Draw the profile of the cam.5.Draw a cam profile to drive an oscillating roller follower to the specifications given below: (a) Follower to move outwards through an angular displacement of 20° during the first 120° rotation of the cam; (b) Follower to return to its initial position during next 120° rotation of the cam; (c) Follower to dwell during the next 120° of cam rotation. The distance between pivot center and roller center = 120 mm; distance between pivot center and cam axis = 130 mm; minimum radius of cam = 40 mm; radius of roller = 10 mm; inward and outward strokes take place with simple harmonic motion.6.A cam, with a minimum radius of 50 mm, rotating clockwise at a uniform speed, is required to give a knife edge follower the motion as described below: 1. To move outwards through 40 mm during 100° rotation of the cam; 2. To dwell for next 80°; 3. To return to its starting position during next 90°, and 4. To dwell for the rest period of a revolution i.e., 90°. Draw the profile of the cam (i) when the line of stroke of the follower passes through the center of the cam shaft, and (ii) when the line of stroke of the follower is off-set by 15 mm. The displacement of the follower is to take place with uniform acceleration and uniform retardation. Determine the maximum velocity and acceleration of the follower when the cam shaft rotates at 900 rpm. Draw the displacement, velocity and acceleration diagrams for one complete revolution of the cam.7.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 20° of cam rotation. The lift of the valve is 37.5 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.8.A cam rotating clockwise at a uniform speed of 1000 rpm. is required to give a roller follower the motion defined below: 1. Follower to move outwards through 50 mm during 120° of cam rotation, 2. Follower to dwell for next 60° of cam rotation, 3. Follower to return to its starting position during next 90° of cam rotation, 4. Follower to dwell for the rest of the cam rotation. The minimum radius of the cam is 50 mm and the diameter of roller is 10 mm. The line of stroke of the follower is off-set by 20 mm from the axis of the cam shaft. If the displacement of the follower takes place with uniform and equal acceleration and retardation on both the outward and return strokes, draw profile of the cam and find the maximum velocity and acceleration during out stroke and return stroke.9.Construct the profile of a cam to suit the following specifications: Cam shaft diameter = 40 mm; Least radius of cam = 25 mm; Diameter of roller = 25 mm; Angle of lift = 120°; Angle of fall = 150°; Lift of the follower = 40 mm; Number of pauses are two of equal interval between motions. During the lift, the motion is S.H.M. During the fall the motion is
Page 3of 3uniform acceleration and deceleration. The speed of the cam shaft is uniform. The line of stroke of the follower is off-set 12.5 mm from the center of the cam.10. It is required to set out the profile of a cam to give the following motion to the reciprocating follower with a flat mushroom contact face: (i) Follower to have a stroke of 20 mm during 120° of cam rotation; (ii) Follower to dwell for 30° of cam rotation; (iii) Follower to return to its initial position during 120° of cam rotation; and (iv) Follower to dwell for remaining 90° of cam rotation. The minimum radius of the cam is 25 mm. The out stroke of the follower is performed with simple harmonic motion and the return stroke with equal uniform acceleration and retardation.11. It is required to set out the profile of a cam with oscillating follower for the following motion: (a) Follower to move outward through an angular displacement of 20° during 90° of cam rotation; (b) Follower to dwell for 45° of cam rotation; (c) Follower to return to its original position of zero displacement in 75° of cam rotation; and (d) Follower to dwell for the remaining period of the revolution of the cam. The distance between the pivot center and the follower roller center is 70 mm and the roller diameter is 20 mm. The minimum radius of the cam corresponds to the starting position of the follower as given in (a). The location of the pivot point is 70 mm to the left and 60 mm above the axis of rotation of the cam. The motion of the follower is to take place with S.H.M. during out stroke and with uniform acceleration and retardation during return stroke.12. Draw the profile of the cam when the roller follower moves with cycloidal motion during out stroke and return stroke, as given below: 1. Out stroke with maximum displacement of 31.4 mm during 180° of cam rotation, 2. Return stroke for the next 150° of cam rotation, 3. Dwell for the remaining 30° of cam rotation. The minimum radius of the cam is 15 mm and the roller diameter of the follower is 10 mm. The axis of the roller follower is offset by 10 mm towards right from the axis of cam shaft.