Set No.
1
Code No. 220304 II B.Tech. II Semester Supplementary Examinations, November-2003
or ld
.in
KINEMATICS OF MACHINERY (Common to Mechanical Engineering, Production Engineering and Mechatronics) MECHANICS OF MACHINERY (Aeronautical Engineering) Time: 3 hours Max. Marks:80 Answer any Five questions All questions carry equal marks --1.a) Distinguish between three, four and five bar chains. Why is the four bar chain considered as a 'basic chain'? b) Differentiate between a crank and a lever. State how their use gives different practical applications of a quadric cycle chain.
Explain how Grass- Hopper mechanism and Watt mechanism generate approximate straight-line motion.
3.
The dimensions of the various links of a pneumatic riveter, as shown in Figure, are as follows: OA = 175 mm; AB = 180 mm; AD = 500 mm and BC = 325 mm; Find the velocity ratio between C and ram D when OB is vertical. What will be efficiency of the machine if a load of 2.5kN on piston C causes a thrust of 4kN at the ram D.
Aj
nt
uW
2.
Contd..2.
or ld
.in
Code No. 220304 -2Set No.1 4. Locate all the instantaneous centers of the mechanism as shown in figure. The lengths of various links are AB = 150 mm; BC = 300 mm; CD = 225 mm; and CE = 500 mm. When the crank AB rotates in the clockwise direction at a uniform speed of 240 r.p.m. Find: (i) Velocity of the slider E and (ii) Angular velocity of the links BC and CE.
Derive the condition for correct steering. Sketch and explain Ackermann's Steering gear mechanism. List the merits and demerits of Ackermann and Davis Steering gear mechanism.
6.
A cam operating a knife - edged follower has the following data a) Follower moves outwards through 40mm during 60 of cam rotation. b) Follower dwells for the next 45. c) Follower returns of its original position during next 90. d) Follower dwells for the rest of the rotation.
uW
5.a) b) c)
The displacement of the follower is to take place with simple harmonic motion during both the outward and return strokes. The least radius of the cam is 50mm. Draw the profile of the cam when the axis of the follower is offset 20mm towards right from the cam axis. If the cam rotates at 300 r.p.m., determine maximum velocity and acceleration of the follower during the outward stroke and the return stroke. Two gears in mesh have a module of 8 mm and pressure angle of 200. The larger gear has 57 teeth while pinion has 23 teeth. If the addenda on pinion and gear wheel are equal to one module. Determine (i) the number of pairs of teeth in contact. (ii) The angles of action of the pinion and the gear wheel (iii) the ratio of the sliding velocity to the rolling velocity at the beginning of engagement, at the pitch point and at the end of engagement.
Aj
nt
7.
8.a) b)
What are the different types in an epicyclic gear trains. A pinion A has 15 teeth and is rigidly fixed to a motor shaft. The wheel B has 20 teeth and gears with A and also with the fixed annular wheel D. The pinion C has 15 teeth and is fixed to the wheel B and gears with annular wheel E which is keyed to a machine shaft. B and C can rotate together on a pin carried by an arm, which rotates about the shaft on which A is fixed. If the motor runs at 1000 rpm, find the speed of the machine. -x-
Set No.
2
Code No. 220304 II B.Tech. II Semester Supplementary Examinations, November-2003
b)
How are the slider crank chain and double slider crank chain derived from the quadric cycle chain? Describe with the help of sketches. Describe Oldham coupling. Where is it used in practice?
or ld
1.a)
.in
KINEMATICS OF MACHINERY (Common to Mechanical Engineering, Production Engineering and Mechatronics) MECHANICS OF MACHINERY (Aeronautical Engineering) Time: 3 hours Max. Marks:80 Answer any Five questions All questions carry equal marks ---
Explain the Scot – Russel mechanism and show that it generates straight-line motion.
3..
Figure shows a worth whit quick return motion mechanism. The various dimensions in the mechanism are as follows: OQ = 100 mm; OA = 200 mm; QC = 150 mm and CD = 500 mm. The crank OA makes an angle of 600 with vertical and rotates at 120 rpm in the clockwise direction. Locate all the instantaneous centers and find the velocity of ram D.
Aj
nt
uW
2.
Contd…2.
Code No.220304
-2-
Set No.2
The crank OA of a mechanism, as shown in figure rotates clockwise at 120 r.p.m. The lengths of various links are: OA = 100 mm; AB = 500 mm; AC = 100 mm and CD = 750 mm. Find by instantaneous centre method: (i) velocity of point C; (ii) velocity of slider D; (iii) Angular velocities of the links AB and CD.
5.a)
Derive an expression for the ratio of the shaft velocities for Hooke's joint and draw the polar diagram depicting the salient features of driven shaft speed. Two shafts with an included angle of 160 connected by a Hooke's Joint. The driving shaft runs at a uniform speed of 1500 R.P.M. The driven shaft carries a fly wheel of mass 12kg and 100 m.m radius of gyration. Find the maximum angular acceleration of the driven shaft and the maximum torque required. A cam rotating clockwise with a uniform speed is to give the roller follower of 20mm diameter with the following motion. a) Follower to move outwards through a distance of 30mm during 120 of cam rotation. b) Follower to dwell for 60 of cam rotation. c) Follower to return to its initial position during 90 of cam rotation; and d) Follower to dwell for the remaining 90 of cam rotation. The minimum radius of the cam is 45mm and the line of stroke of the follower is offset 15mm from the axis of the cam and the displacement of the follower is to take place with simple harmonic motion on both the outward and return strokes. Draw the cam profile.
nt
6.
uW
b)
or ld
.in
4.
Two 200 gears have a module pitch of 4 mm. The number of teeth on gear 1 is 40 and on gear 2 is 24. If the gear 2 rotates at 600 rpm, determine the velocity of sliding when the contact is at the tip of the tooth of gear 2. Take addendum equal to one module. Also find maximum length of path of contact and the maximum velocity of sliding. Take Case: 1) pinion as driver and Case: 2) gear wheel as driver. Contd…3.
Aj
7.
Code No. 220304
Set No.2.
An epicyclic train is composed on a fixed annular wheel A having 150 teeth. Meshing with A is a wheel B which drives wheel D through and idle wheel C, D being concentric with A. Wheels B and C are carried on an arm which revolves clockwise at 100 rpm about the axis of A and D. If the wheels B and D have 25 and 40 teeth respectively, find the number of teeth on C and the speed and sense of rotation of C.
Aj
nt
uW
or ld
-x-
.in
8.
-3-
Set No.
Code No. 220304
3
II B.Tech. II Semester Supplementary Examinations, November-2003
or ld
.in
KINEMATICS OF MACHINERY (Common to Mechanical Engineering, Production Engineering and Mechatronics) MECHANICS OF MACHINERY (Aeronautical Engineering) Time: 3 hours Max. Marks:80 Answer any Five questions All questions carry equal marks --1.a) List different inversions of double slider brank mechanism. Explain the function of any of them with a neat sketch. b) The distance between the axes of the two parallel shafts is 10-2 m. They are connected by Oldham coupling having flanges each 0.2 m diameter. Find the maximum kinetic energy of the intermediate piece when the shafts revolve at 250 rpm. The intermediate piece is 0.025 m thick and has tongues each 0.01 m wide X 0.005 m deep. The specific weight of C.I., of which the coupling is made, is 72,000 N/m3. Classify the straight-line motion mechanisms. Describe “a copied straight-line mechanism”.
3.
A quick return mechanism is shown in figure, Link 2 rotates at 20 rod/S and has a length of 0.15m. Draw the velocity and acceleration diagram. Determine the magnitude of corili’s component of acceleration.
Aj
nt
uW
2.
Contd…2.
Code No. 220304
-2-
Set N o.3
A mechanism as shown in figures has the following dimensions: O1A = 60 mm; AB 180 mm; O2B = 100 mm; O2C = 180 mm and CD = 270 mm. The crank O1C = 180 mm and CD = 270 mm. The crank O1A rotates clockwise at a uniform speed of 120 r.p.m. The block D moves in vertical guides. Find by instantaneous centre method, the velocity of D and the angular velocity of CD.
5.a)
Describe the working of Davis steering gear mechanism giving neat sketch. Derive the condition for correct steering of the above mechanism. 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. A cam with 30mm as minimum diameter is rotating closewise at a uniform speed of 1200 r.p.m. and has to give the following motion to a roller follower 10 mm in diameter. a) Follower to complete outward stroke of 25mm during 120 of cam rotation with equal uniform acceleration and retardation. b) Follower to dwell for 60 of cam rotation. c) Follower to return to its initial position during 90 of cam rotation with equal uniform acceleration and retardation. d) Follower to dwell for the remaining 90 of cam rotation Draw the cam profile if the axis of the roller follower passes through the axis of the cam. Determine the maximum velocity of the follower during the outstroke and return stroke and also the uniform acceleration of the follower on the outstroke and the return stroke.
Aj
nt
6.
uW
b)
or ld
.in
4.
Contd…3.
Code No.220304
-3-
Set No.3
Two mating involute spur gears of 200 pressure angle have a gear ratio of 2. The number of teeth on the pinion is 20 and its speed is 250 rpm. The module pitch of the teeth is 12 mm. If the addendum on each wheel is such that the path of approach and the path of recess on each side are half the maximum possible length each, find (i) the addendum for pinion and gear wheel (ii) the length of arc of contact (iii) the maximum velocity of sliding during approach and recess. Assume pinion to be driver.
8.
In an epicyclic train an annular wheel A having 54 teeth meshes with a planet wheel B which gears with a sun wheel C, the wheels A and C being coaxial. The wheel B is carried on a pin fixed on one end of arm P which rotates about the axis of the wheels A and C. If the wheel A makes 20 rpm in a clockwise direction and the arm P rotates at 100 rpm in the anticlockwise direction and the wheel C has 24 teeth, determine the speed and sense of rotation of arm P.
or ld
.in
7.
Aj
nt
uW
-x-
Set No.
4
Code No. 220304 II B.Tech. II Semester Supplementary Examinations, November-2003
.in
KINEMATICS OF MACHINERY (Common to Mechanical Engineering, Production Engineering and Mechatronics) MECHANICS OF MACHINERY (Aeronautical Engineering) Time: 3 hours Max. Marks:80 Answer any Five questions All questions carry equal marks --1. Sketch slider crank chain and its various inversions, stating actual machines in which these are used in practice. Derive the necessary equations for Hart’s straight-line mechanism.
3.
The following data refer to a quick return motion of crank and slotted lever type shown in figure. Distance between fixed centers O and A = 25 cm Length of driving Crank AB = 10 cm Length of slotted link OC = 40 cm Length of rod CD = 15 cm Angle O A B = 1200 Uniform speed of the crank in clockwise direction = 60 rpm Line of stroke of ram is perpendicular to OA Determine velocity and acceleration of D.
Aj
nt
uW
or ld
2.
Contd…2.
Code No.220304
-2-
Set No.4
The lengths of various links of a mechanism as shown in Figure are; OA = 0.3m; AB = 1m; CD = 0.8 m; and AC = CB. Determine, for the given configuration, velocity of slider D if the crank OA rotates at 60 r.p.m in the clockwise direction. Also find the angular velocity of the link CD. Use instantaneous centre method.
5.a)
What is the function of a steering gear. What are the mechanisms used in general. Explain any one of them. In a Davis Steering gear the distance between the pivot's of the front axle is 1 metre and the wheel base is 2.5 metres. Find the inclination of the track arm to the longitudinal axis of the car when it is moving along a straight path. 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 60 rotation with S.H.M. b) The follower remains at rest for next 40 rotation of the cam. c) The follower then descents to its original position during 90 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.
nt
6.
uW
b)
or ld
.in
4.
A pair of 200 involute gears in mesh has a module of 6 mm. The number of teeth on pinion is 17 and that of gear wheel is 49. The addendum on pinion and gear wheel is one module. Calculate (i) the length of path of contact, arc of contact and the contact ratio. (ii) The angle turned through by the pinion and the gear wheel when one pair is in contact. (iii) The ratio of the sliding to rolling motion at the beginning of engagement, at the pitch point and at the end of engagement. (iv) What would be the effect of increasing addendum on pinion while maintaining the working depth the same as before?
Aj
7.
Contd..2.
Code No.220304 8.
-3-
Set No. 4
A speed reduction gear between two shafts having the same axis consists of an epicyclic train as follows:
Aj
nt
uW
or ld
-x-
.in
Wheel A is keyed on the driving shaft. Wheel B gears with A and also with a fixed annular wheel C. Wheels B and D are fixed to the common spindle which is carried by an arm which can rotate about the axis of the wheel A and the wheel D gears with an annular wheel E which is keyed to the driven shaft. If E has 20, B 24 and D16 teeth and all teeth have the same pitch, find the velocity ratio of the two shafts.
