Theory Of Machines Lecture 5(A) PDF - UMT-308

Theory of Machines (UMT-308) Lecture –5(a) (13th August, 2024) Presented By: Dr. Gagandeep Bhardwaj, Associate Professor, MED 1 Email: [email protected]  Inversions of Double Slider Crank Chain Scotch Yoke mech...

Theory of Machines (UMT-308) Lecture –5(a) (13th August, 2024) Presented By: Dr. Gagandeep Bhardwaj, Associate Professor, MED 1 Email: [email protected]  Inversions of Double Slider Crank Chain Scotch Yoke mechanism: This mechanism is used for converting rotary motion into a reciprocating motion. The inversion is obtained by fixing either the link 1 or link 3. The link 1 is fixed. In this mechanism, when the link 2 (which corresponds to crank) rotates about B as centre, the link 4 (which corresponds to a frame) reciprocates. The fixed link 1 guides the frame. 9/18/2024 Dr. Gagandeep Bhardwaj, AP MED, TIET 2  Inversions of Double Slider Crank Chain Oldham’s coupling: An oldham's coupling is used for connecting two parallel shafts whose axes are at a small distance apart. The shafts are coupled in such a way that if one shaft rotates, the other shaft also rotates at the same speed. This inversion is obtained by fixing the link 2. The shafts to be connected have two flanges (link 1 and link 3) rigidly fastened at their ends by forging. 9/18/2024 Dr. Gagandeep Bhardwaj, AP MED, TIET Problem 1: A crank and slotted lever mechanism used in a shaper has a centre distance of 300 mm between the centre of oscillation of the slotted lever and the centre of rotation of the crank. The radius of the crank is 120 mm. Find the ratio of the time of cutting to the time of return stroke. AC = 300 mm; CB1 = 120 mm 9/18/2024 Dr. Gagandeep Bhardwaj, AP MED, TIET 4  Mechanical Advantage It is defined as the ratio of the output force or input force or torque at any instant. The input torque T2 is applied to link 2 to drive the output link 4 with a resisting torque T4. power Input = Power output T22  T44 T4 2 M.A   T2 4 9/18/2024 Dr. Gagandeep Bhardwaj, AP MED, TIET 5  Transmission Angle The angle μ between the output link and coupler is known as transmission angle. AB – input link, the force acting to the output link DC is transmitted through the coupler BC For a particular value of force in the coupler Coupler rod, the torque transmitted to the output link (about the point D) is maximum when the Output link transmission angle μ is 90°. Input link If links BC and DC become coincident, the transmission angle is zero and the mechanism would lock or jam. If μ deviates significantly Fixed from 90°, the torque on the output link decreases. Applying cosine law to triangles ABD and BCD 9/18/2024 Dr. Gagandeep Bhardwaj, AP MED, TIET 6  Transmission Angle 9/18/2024 Dr. Gagandeep Bhardwaj, AP MED, TIET 7 THANKS 8