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CAT -2 EXAMINATION, SEPTEMBER - 2013Mechanical Engineering
ME 2203 - KINEMATICS OF MACHINERYAnswer ALL Questions
PART - A (10 X 2 = 20)1. State the expression for maximum
acceleration of a follower moving with cycloidal motion.2. Axes of
translating roller followers in cam follower mechanisms are offset
from the axis ofrotation of cam?3. Define the term arc of
contact.4. Name two applications of reverted gear train.5. Sketch
the shapes of displacement, velocity and acceleration diagrams for
uniformacceleration and retardation.6. What are the advantages of
planetary gears?7. Define pressure angle of a cam mechanism and
state the best value of the pressure angle.8. What is epicyclic
gear train? Give practical example.
9. Why is roller follower preferred to knife edge follower?10.
What is the use of differential in automobile?
PART - B (5 X 16 = 80)11. a) A disc cam used for moving a knife
edge follower with SHM during lift and uniformacceleration and
retardation motion during return. Cam rotates at 300rpm CW. The
line ofmotion of the follower has an offset 10mm to the right angle
of the cam shaft axis. Theminimum radius of the cam is 30mm. The
lift of the follower is 40mm . the cam rotationangles are: lift 60,
dwell 90, return 120 and remaining angle for dwell. Draw the
camprofile and determine the maximum velocity and acceleration
during the lift and return. (16)
(Or)b) What is tangent cam? Derive the expression for the
velocity and acceleration of a rollerfollower in the tangent cam.
(16).
12. a) Draw a cam profile for operating an exhaust valve of an
oil engine. It is required to giveequal uniform acceleration and
retardation during opening and closing of the valve
whichcorresponds to 60 of cam rotatation . The valve must remain
fully open position for 20of camrotation. The valve is 37.5mm and
the least radius of the cam is 40mm. The follower isprovided with
roller follower of radius 20mm and its line of stroke passes
through the axis ofthe cam. (16)
(Or)
b) A cam drives a flat reciprocating follower having SHM moving
outwards through adistance of 20mm during first 120 rotation of
cam. It dwells during next 30 of cam rotation.Then it moves inwards
with SHM for next 120 of cam rotation and dwells for
remainingperiod. Draw the profile of the cam when the radius of cam
is 25mm, also calculate maximumvelocity and acceleration during
outward and inward motion of follower assuming speed to be200rpm.
(16)
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13. a) In a symmetrical tangent cam operating a roller follower
the least radius of cam is30mm and roller radius is 17.5mm. The
angle of ascent is 75 and the total lift is 17.5mm.The speed of the
cam shaft is 600rpm. Assume there is no dwell between ascent and
descent.Calculate the principal dimensions of cam. Find the
acceleration of the follower at thebeginning of the lift and draw
the profile of cam. (16)
(Or)b) In a symmetrical circular cam operating a flat face
follower of least radius= 25mm, noseradius= 8mm, lift of valve=
10mm angle of action of cam= 120, cam shaft speed = 1000rpm.Find
flank radius, determine the maximum values of velocity,
acceleration and retardation offollower and also draw the profile
of the cam. (16)
14 a) State and prove the law of gearing. Show that the involute
curves as the profiles ofmating gears satisfy the law of gearing.
(16)
(Or)b) (i) A pair of spur gears with involute teeth is to give a
gear ratio of 3:1. The arc of approachis not to be less than the
circular pitch and smaller wheel is the driver. The pressure angle
is
20. What is the least number of teeth that can be used on each
wheel? What is theaddendum of the wheel in terms of circular pitch.
(8)(ii) A pinion of 20 involute teeth and 125mm pitch circle
diameter drives a rack. Theaddendum of both the pinion and rack is
6.25mm. What is the least pressure angle which canbe used to avoid
interference? With this pressure angle find the length of arc of
contact andthe minimum number of teeth in contact at a time.
(8)
15 a) Two involute gears of 20 pressure angle are in mesh. The
number of teeth on pinion is20 and the gear ratio is 2. If the
pitch expressed in module is 5mm and the pitch line speed is1.2m/s
assuming addendum as standard and equal to one module, find (i)
angle turnedthrough by pinion when one pair of teeth is in mesh
(ii) the maximum velocity of sliding. (16)
(Or)b) In an epicyclic gear train, an annular wheel A having 54
teeth meshes with a planet wheelB which gears with a sun wheel C,
the wheels A and C being rotated about hte axis of thewheels A and
C. If the wheel A makes 20rpm in CW direction and the arm rotates
at 10rpmin the ACW direction and the wheel C has 24 teeth.
Determine the speed and direction ofrotation of wheel C. (16)
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