Roll No ..................

TokNo.ofQuestions:09] Paper ID [PE207] [Total No. of Pages: 03

~(please fill this Paper ill in OMR Sheet)

B.Tech. (Semester- 3rd)THEORY OF MACHINES (PE - 207)

Maximum Marks: 60Time: 03 Hours

Instruction to Candidates:

1) Section - A is compulsory.

2) Attempt any Four questions from Section - B.

3) Attempt any Two questions from Section - C.

Section - A

(JOx2=20) .

Why is the power transmitted by a crossed belt drive more than thatof

. an open belt drive? In which case is the belt likely to wear out quickly.~dw~? .

Distinguish between 'slip' and 'creep' in belt drive.

What is friction circle? Derive ~ .expression for its radius.

d) State and briefly explain the law of gearing.

e) Write the principle of hydrodynamic lubrication.

f) Derive Grtibler's Equation for planer mechanisms of lower pairs.

g) A mechanism is to be designed to generate the function y =XO.6for the

range lsxs3, using three precision points. Find the values of x and y.

h) Write the expression for the frictional torque for conical pivot bearingassuming uniform pressure.

i) Differentiate between period of ascent and period of decent.

j) What is a compound epicyclic gear train? .

'\

Ql)

a)

1 b)

c)

,~ection -B ~

(4 x 5 = 20)

Q2) Explain what interference ~sand how it is prevented? ,~

Q3) Detennine the angular positions, angular.velodties, and angular accelerationof all the members of the linkage shown in Fig.l when link AB is at 60° to thehorizontal. Also find the position, velocity, and acceleration of point E in the

coupler member of !he linkage. LinkAB is driven at a constant angular velocityof 10 rad/sec CCW.

8 Cem

B 8em

..

8em

Fig. 1

Q4) A pinion and rack are in mesh. The rack is driven by pinion of 125 mmpitch circle diameter. The number of involute teeth on the pinion is 20. Theaddendum of both pinion and rack is 6.25 mm. If the interference is to be,avoided, find the least pressure angle.

Q5) Draw the carn profile for the data given:Base circle radius of carn:' 50 mmLift : 40 mm

Angle of ascent : 60°Angle of-dwell : . 40°

Angle of decent : 90°Speed of Cam : 300 rpmMotion of follower : SHM

Type of follower : Knife-edge.'

J-1255 2

Q6) Prove that the angle of contact (8) is equal to (180-2 a) for an open-belt'(' whereas it,is equal to (180 + 2 a) for a crossed-belt.

;~ Section - C

(2 xlO = 20)

Q7) Write short notes on:

(a) Klein's construction for acceleration diagram.

(b) Hydrostatic lubrication.

(c) Epi-cyClic train dynamometer.

""

Q8) A multi-plate friction clutch has to be designed to transmit 75kW from an

engine rotating at 2000 rev/min. The inner and outer diameters are respectively100 rom and 150 rom, the pressure is to be assumed uniform at 150 kN/m2

and '/-l =0.25. Determine the necessary end thrust and the number of plates

required. "

If this clutch is then used to transmit power from a larger engine to a rotorwhich has a mass of 1150 kg and a radius of gyration of 200 rom, determine

the time required for this rotor to reach 1500 rev/min from standstill, assumingthat the clutch is transrhitting the maximum possible torque.

Q9) In an internal expanding shoe brake the co-efficient of friction is 0.35, and

the braking'torque required is 25N-m. Calculate the total cam force requiredto operate the brake when the brake drum rotates' clockwise. Internal radius'

of the brake drum is 120 rom, distance' between fulcrum ap.d centre of thebrake drum is 80 rom, distance between cam and fulcrum (L) is 160 mm.(angle between fulcrum, centre of the brake drum, and heel of the brake is

, ,

(8) =30°)and (angle between fulcrum, centre of the brake drum, and brake

toe is (82) = 150°).