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B.E. (Mechanical Engineering / Power Engineering) Seventh Semester (C.B.S.)
Design of Mechanical Drives
P. Pages : 2 NRJ/KW/17/4615/4661
Time : Three Hours * 0495* Max. Marks : 80
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Notes : 1. All questions carry marks as indicated.
2. Solve Question 1 OR Questions No. 2.
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3. Solve Question 3 OR Questions No. 4.
4. Solve Question 5 OR Questions No. 6.
5. Solve Question 7 OR Questions No. 8.
6. Assume suitable data whenever necessary.
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7. Illustrate your answers whenever necessary with the help of neat sketches.
8. Use of non programmable calculator is permitted.
9. Use of Design Data book is permitted.
1. a) Design a bush-pin type coupling to couple the shaft transmitting 20 kw at 1000 rpm. 8
Assume suitable material for shaft, bolt, & hub Take shaft dia. as 45mm.
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b)
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A. punching machine makes 30 holes/min in a steel plate of 18mm thickness. The diameter
of hole is 25mm and shear strength of plate is 240N/mm2. If the actual punching operation
takes place during one tenth of revolution of crank, Design a suitable fly wheel which is
required to rotate at '9' times the speed of crank shaft. The permissible coefficient of
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fluctuation of speed is 0.1 and space limitation require that the diameter of the fly wheel
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should not exceed 1000 mm.
OR
2. a) A. 75mm diameter machine shaft is to be supported at the ends it operate continuously for 8
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8hrs/day, 300 days/year. for 10 years. The load and speed cycle for one of the bearing is
given below. Select suitable bearing.
Sr. No Fraction of Radial load Thrust load Speed (rpm) Load condn
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cycle (N) (N)
1 0.25 3000 2000 1000 Steady
2 0.25 2500 500 1500 Steady
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3 0.5 4000 2000 800 Light shocks
b) A Journal Bearing is proposed for centrifugal pump. The diameter of Journal is 150mm and 12
the load on it is 45 KN and it's speed is 900 rpm. The lubricating oil used is
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SAE = 30. Take oil temperature as 70ºC and room temperature as 30ºC complete the
design calculation for bearing.
3. a) A 500 mm diameter Pulley transmit power to 1200mm diameter pulley with center distance 10
between them is 2.5 meter. The pulley is of cast-iron and leather medium duty double ply
belt is used to transmit power. The belt is 400 mm wide. What maximum power can be
transmitted by this drive. If stress in belt is not to exceed 2.5 Mpa. What is speed of belt at
maximum power. Calculate stress due to initial tension?
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b) Design a roller chain drive used to transmit power from a 25 kw motor to reciprocating 10
pump. The pump is to operate continuously 24 hrs/day. The speed of motor is 900 rpm
and that of the pump is 300 rpm.
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4. a) Select a wire rope for a vertical mine hoist to lift a load of 55 KN from a depth of 300 16
meters. A rope speed of 500 m/min is to be attained in 10 second. Determine the shear and
drum dimensions.
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b) Give the classification and application of wire rope 4
5. Design a spur gear which is required to transmit 15kw. The speed of driving motor & driven 20
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machine are 400 rpm and 200rpm. Respectively. The center distance may be taken as 600
mm. The teeth have 20º full depth involute profile. Assume that both gears are made of cast
iron high grade having allowable strength. 105 MPa.
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6. a) State the factor responsible for dynamic tooth load in gear drive. 3
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b) A helical gear speed reducer is used to transmit 2kw from electric motor running at 1440 17
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rpm to centrifugal blower running at 300 rpm. The gears are to be hobbed with 20º full
depth. hobs. The pinion should have 22 teeth. Design the pair of gears for continuous duty
and give all specification including accuracy grade, assume suitable data, (gear blank
design not expected) Assume helix angle ψ 25º .
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7. a) Design a worm gear speed reducer to transmit 23 kw at 1440 rpm, the desired speed ratio 16
is 24:1 and efficiency is 85%. Assume that worm is made of hardened steel and gear of
phosphor bronze.
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b) Explain in brief the enveloping of worm gear. 4
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8. a) The cylinder of a four-stroke diesel engine has the following specification. 15
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Brake power – 3.75kw
Speed = 1000 rpm.
Indicated mean effective pressure – 0.35 MPa
Mechanical efficiency – 80%
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Determine the bore and length of cylinder liner.
b) What are the desirable properties of material for cylinders and cylinder liners. 5
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NRJ/KW/17/4615/4661 2
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