2161901_DOM_GTU Paper Analysis_12022019_021056PM.pdf - GTU Paper Analysis(New Syllabus Questions Sr No Chapter 1 \u2013 Balancing of Rotating Masses Theory

2161901_DOM_GTU Paper Analysis_12022019_021056PM.pdf - GTU...

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GTU Paper Analysis (New Syllabus) Dynamics of Machinery (2161901) Department of Mechanical Engineering Darshan Institute of Engineering & Technology Chapter 1 Balancing of Rotating Masses Sr. No. Questions 07/12/18 10/05/18 23/11/17 10/05/17 27/10/16 19/05/16 Theory 1. Explain the method of balancing of several masses in different planes. 03 07 2. Explain the balancing of several masses rotating in same plane by Graphical Method. 04 3. Why is balancing of rotating parts necessary for high speed engines? Explain clearly the terms static balancing and dynamic balancing. State the necessary conditions to achieve them. 07 2. What are the reasons for unbalance in rotating machine elements? Give two practical examples of rotating unbalances in systems. 04 3. What is meant by field balancing? Explain the procedure in detail. 07 4. A statically balanced system need not to be dynamically balanced always. Justify the statement. 03 5. Explain the balancing of several masses rotating in same plane by Graphical Method. 04 6. What is static and dynamic balancing? 03 Examples 1. Four masses A, B, C & D are completely balanced. Masses C & D makes an angle of 90 0 and 195 0 respectively with that of mass B in the counterclockwise direction. The rotating masses have the following properties: masses at B, C & D are 25 Kg, 40 Kg and 35 Kg respectively with their radii of rotations are 200 mm, 100 mm & 180 mm respectively. The radius of rotation of mass A is 150 mm. Planes B & C are 250 mm apart. Determine the (i) mass A and its angular position with that of mass B, (ii) position of all the planes relative to plane of mass A. 07
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GTU Paper Analysis (New Syllabus) Dynamics of Machinery (2161901) Department of Mechanical Engineering Darshan Institute of Engineering & Technology 2. A rotating shaft carries four unbalanced masses A=20 kg, B=15kg, C=18kg and D=12kg. The mass centers are 50, 60, 70 and 60 mm respectively from the axis of the shaft. The second, third and fourth masses rotates in planes 100, 150 and 300 mm respectively measured from the plane of first mass and at angular locations of 60º, 120º, and 280º respectively, measured clockwise from the first mass. The shaft is dynamically balanced by two masses, both located at 50mm radii and revolving in planes midway between those of first and second masses and midway between those of third and fourth masses. Determine the balancing masses and their angular positions. 07 3. The four masses m1, m2 m3 and m4 having their radii of rotation as 200 mm, 150 mm, 250 mm and 300 mm are 200 kg, 300 kg, 240 kg and 260 kg in magnitude respectively. The angles between the successive masses are 45˚, 75˚ and 135˚ respectively. Find the position and magnitude of the balance mass required, if its radius of rotation is 200 mm. Use analytical method. 07 4. Four masses 150 kg, 200 kg, 100 kg and 250 kg are attached to a shaft revolving at radii 150mm, 200 mm, 100 mm and 250 mm ; in planes A, B, C and D respectively. The planes B, C and D are at distances 350 mm, 500 mm and 800 mm from plane A. The masses in planes B, C and D are at an angle 105 0 , 200 0 and 300 0 measured anticlockwise from mass in plane A. It is required to balance the system by placing the balancing
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