Question 4: Attempt any THREE of the following:
a) State the different ‘Follower Motions’. Draw a sketch of any one follower motion (Displacement diagrams).
A follower in a cam mechanism can move in several ways depending on the cam profile. The most common types of follower motions are:
1. Uniform Velocity:The follower moves at a constant speed throughout its stroke.
2. Simple Harmonic Motion (SHM): A smooth motion used for moderate speeds, following a semi-circular path in its displacement diagram.
3. Uniform Acceleration and Retardation (UARM): The follower starts slowly, speeds up to the midpoint, and then slows down.
4. Cycloidal Motion: The smoothest motion, ideal for high-speed operations as it reduces jerk and noise.
b) Differentiate between belt drive and chain drive (Any four points).
c) Define the following terms related to Spur Gear:
1. Addendum: The radial distance from the pitch circle to the top of the gear tooth.
2. Dedendum: The radial distance from the pitch circle to the bottom (root) of the gear tooth space.
3. Module (m): The ratio of the pitch circle diameter (D) to the number of teeth (T). It defines the tooth size (m = D/T).
4. Pressure Angle: The angle between the line of action (common normal to the teeth) and the common tangent to the pitch circles. Common values are 14.5° or 20°.
e) Define ‘Free vibration’ and ‘Forced vibration’.
Free Vibration: This occurs when a system is given an initial displacement and then left to vibrate on its own without any external periodic force. The system vibrates at its "natural frequency."
Example: A plucked guitar string.
Forced Vibration: This happens when a system is continuously subjected to an external periodic force. The system is "forced" to vibrate at the frequency of the applied force.
Example: The vibration of a building due to a nearby heavy machine.
Question 5: Attempt any TWO of the following:
a) Define relative velocity. State the inter-relation between linear and angular velocity and acceleration.
Relative Velocity: It is the velocity of one object as observed from another moving object. If body A moves at V_a and body B at V_b, the relative velocity of A with respect to B is V_{ab} = V_a - V_b.
Inter-relation:
Velocity: Linear velocity (v) is the product of radius (r) and angular velocity (\omega).
Acceleration: Linear acceleration (a) is related to angular acceleration (\alpha) by:
b) Explain with sketch “Elliptical trammel”. State its application (Any two points).
An elliptical trammel is a mechanism that translates reciprocating motion into circular/elliptical motion. It consists of two grooves at right angles to each other and a rod with two sliders that move within these grooves. As the sliders move, a fixed point on the rod traces a perfect ellipse.
Applications:
1. Used in drawing offices to trace accurate elliptical shapes.
2. Used in certain specialized high-torque engines or mechanical linkages to convert motion.
c) Cam Profile Data (Conceptual Explanation):
This question asks for a cam profile construction. To solve this, you would plot:
1.Outstroke (0° to 60°): Use the SHM formula to plot the rise.
2. Dwell (60° to 90°): A straight horizontal line (no movement).
3. Return Stroke (90° to 150°): A st
raight sloping line because the velocity is "uniform."
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