Kinematics Of Machinery Mechanics Of Machinery Nr220304

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Code No: NR220304

II B.Tech II Semester Supplementary Examinations, Apr/May 2006 KINEMATICS OF MACHINERY MECHANICS OF MACHINERY ( Common to Mechanical Engineering, Mechatronics, Production Engineering and Aeronautical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) Find out the degrees of freedom of the gear system shown in the following Figure 1. (b) The distancce between two parallel shafts is 15 mm and they are connected by an Oldham’s coupling. The driving shaft revolves at 150 r.p.m.What will be the maximum speed of sliding of the tongue of the intermediate piece along its groove? (c) What are resistant bodies? Is it necessary that the resistant bodies be rigid? Give reasons for your answer.

Figure 1: [4+8+4] 2. (a) Show the Peaucellier mechanism generates an exact straight line as its path. (b) Classify the straight line motion mechanisms with examples.

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Code No: NR220304

3. Figure 2 shows a quick return motion mechanism in which the driving crank OA rotates at 120 r.p.m in a clockwise direction. For the position shown, determine the magnitude and direction of (a) the acceleration of block D and (b) the angular acceleration of the slotted bar QB. The lengths of various links are OA = 200 mm; CQ = 15 mm; CD = 500 mm.

[16]

Figure 2: 4. Explain with sketches how the instantaneous centers of the following mechanisms are obtained. (a) Four bar chain (b) simple slider crank chains.

[8+8]

5. (a) Describe the working of Davis steering gear mechanism giving neat sketch. Derive the condition for correct steering of the above mechanism. (b) The Distance between the steering pivots of a Davis Steering gear is 1.3m. The wheel base is 2.75 metres. What will be the inclination of the track arms to the longitudinal axis of the vehicle if it is moving in a straight path. [8+8] 6. Draw the profile of a cam operating a knife edged follower from the following data. (a) It lifts the follower through 3.75 cm during its 600 rotation with S.H.M. 2 of 3

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Code No: NR220304 (b) The follower remains at rest for next 400 rotation of the cam.

(c) The follower then descents to its original position during 900 rotation of the cam with S.H.M. (d) The follower remains at rest for the rest of the revolution. The least radius of the cam is 5 cm. If the cam rotates at 300 RPM. Find the maximum velocity and acceleration of the follower during ascent and descent. The axis of the follower passes through the axis of the cam shaft. [16] 7. A pinion 120 mm PCD meshes with a gear wheel 400 mm PCD. The teeth are of involute form, 2 mm module pitch and 250 angle of obliquity. Addendum for each wheel is 6 mm. Find the angle that the pinion turns through while any one pair of teeth continue to maintain contact. If the pinion is the driven and rotates at 200 rpm, find the velocity of sliding at the instant contact ceases. Prove any formula you use in this latter part. [16] 8. (a) Explain the difference between a compound gear train and an epicyclic gear train. (b) In an epicyclic gear train, as shown in Figure 3, the number of teeth on wheels A,B and C are 48, 24 and 50 respectively. If the arm rotates at 400 r.p.m., clockwise, find: i. Speed of wheel C when A is fixed and ii. Speed of wheel a when C is fixed.

Figure 3:

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