This set of Machine Design Multiple Choice Questions & Answers (MCQs) focuses on “Eccentric Load on Circular Base”.
1. A flange of radius 200mm is fastened to the machine screw by means of four cap screws of pitch circle radius 150mm. The external force P is 20kN which is loaded at 160mm from the machine screw. There are two dowel pins to take shear load. Determine the maximum effective tensile force acting on the bolt. The four bolts are equally spaced radially.
Explanation: Maximum force F=2Pl[a+bCos(90/2)] / 4(2a²+b²).
2. A flange of radius 200mm is fastened to the machine screw by means of four cap screws of pitch circle radius 150mm. The external force P is 20kN which is loaded at 160mm from the machine screw. There are two dowel pins to take shear load. Determine the core diameter of cap screw if permissible tensile stress in cap screw is 40N/mm².
a) None of the listed
Explanation: Maximum tensile force=4777.6N or πd² x σ/4=4777.6N.
Answer the questions 3-5 with respect to this figure
A round flange bearing is fastened to the machine frame by means of 4 cap screws. The angle made by central axis of bolt 2 and horizontal is θ. Also the radii of flange and pitch circle are a & b respectively. Given: Sum of squares of distance of bolts from axis of tilt is 2a² +b²
3. Are all the four bolts under equal effective tensile load?
c) Depends on magnitude of load
d) Cannot be stated
Explanation: All the bolts are at different distance from the axis of tilt and hence unequally loaded.
4. Determine the angle θ so that the force in the bolt 1 has maximum value.
Explanation:F₁=2Plx(a-b Cos θ)/4(2a²+b²), hence for force to be max Cosθ=-1 or θ=180’.
5. Which bolt is under maximum stress if dowel pins are used to relieve cap screws from shear stress?
Explanation: The screw farthest from the axis of tilt is under maximum stress.
6. Which of the following statements are true about eccentrically loaded circular base?
a) All bolts are symmetrically spaced with equal angle on either side of vertical
b) Bolts are not preloaded
c) Bearing is rigid
d) Dowel pins are used to relieve stresses
Explanation: Bolts are symmetrically placed only in a special case.
7. Certain types of radial bearings can also take thrust load.
Explanation: Sometimes radial bearings can take thrust load and vice versa.
8. Balls and the races of the deep groove ball may roll freely without any sliding.
Explanation: There is a point contact between the balls and the races.
Sanfoundry Global Education & Learning Series – Machine Design.
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