Download Sathyabama Univarsity B.E Nov 2010 Design of Transmission

Register Number
SATHYABAMA UNIVERSITY
(Established under section 3 of UGC Act, 1956)
Course & Branch: B.E-MECH
Title of the Paper: Design of Transmission Systems Max. Marks: 80
Sub. Code: 615602
Time: 3 Hours
Date: 12/11/2010
Session: AN
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1.
PART - A
(10 X 2 = 20)
Answer ALL the Questions
Define the term creep in belts.
2.
Why are V-belts preferred than flat belts?
3.
State law of gearing.
4.
What is virtual number of teeth in helical gears?
5.
What are the forces acting on a bevel gear?
6.
Define normal pitch of a worm gear.
7.
State any three basic rules to be followed while designing a gear
box.
8.
What is step ratio?
9.
Compare disc clutches and cone clutches.
10. What is self locking brake?
PART – B
(5 x 12 = 60)
Answer ALL the Questions
11. A belt drive is required to transmit 12kW from a motor running at
720r.p.m. The belt is 12mm thick and has a mass density of 0.001
gm/mm3. Permissible stress in the belt not to exceed 2.5 N/mm2.
Diameter of driving pulley is 250mm whereas the speed of the
driven pulley is 240 r.p.m. The two shafts are 1.25m apart.
Coefficient of friction is 0.25. Determine the width of the belt.
(or)
12. Design a V-belt drive to the following specifications.
Power transmitted = 7.5 kW.
Speed of driving wheel = 1440 r.p.m.
Speed of driven wheel = 400 r.p.m.
Diameter of driving wheel = 300mm.
Centre distance = 1000mm
Service = 16 hours/day.
13. Design a spur gear drive required to transmit 45 kW at a pinion
speed of 800 r.p.m. The velocity ratio is 3.5:1. The teeth are 20
full depth involute with 18 teeth on the pinion. Both the pinion
and gear and gear are made of steel with a maximum safe static
stress of 180N/mm2. Assume medium shock conditions.
(or)
14. A pair of parallel helical gears consists of an 18 teeth pinion
meshing with a 45 teeth gear. A 7.5 kW power at 2000 r.p.m. is
supplied to the pinion through its shaft. The normal module is
6mm, while the normal pressure angle is 20. The helix angle is
23. Determine the tangential, radial and axial components of the
resultant tooth force between the meshing teeth.
15. A pair of straight tooth bevel gears has a velocity ratio of 4/3.
The pitch diameter of the pinion is 150mm. The face width is
50mm. The pinion rotates at 240 rev/min. The teeth are 5mm
module, 14½ involute. If 6kW is transmitted, determine
(a) The tangential force at the mean radius
(b) the pinion thrust force
(c) The gear thrust force
(d) Draw the free body diagrams indicating the forces
(or)
16. Design a worm gear drive to transmit 18kW at a worm speed of
1440 r.p.m. The speed ratio is 24. The minimum required
efficiency of the drive is 85%. Check the design for heat
dissipation and give your inference.
17. A nine speed gear box, used as a head stock gear box of a turret
lathe is to provide a speed range of 180 r.p.m. to 1800 r.p.m.
Using standard step ratio, draw the speed diagram and the
kinematic layout. Also find the fix the number of teeth on all
gears.
(or)
18. Design a 12 speed gear box for an all geared headstock of the
lathe. Maximum and minimum speeds are 600 r.p.m. and 25
r.p.m. respectively. The drive is from an electric motor giving
2.25 kW at 1440 r.p.m.
19. A plate clutch with maximum diameter 60mm has maximum
lining pressure of 0.35 MPa. The power to be transmitted at 400
r.p.m. is 135 kW and  = 0.3. Find inside diameter and spring
force required to engage the clutch. Springs with spring index 6
and material spring steel with safe shear stress 600 MPa are used.
Find the wire diameter if 6 spring are used.
(or)
20. A rope drum of an elevator having 650mm diameter is fitted with
a brake drum of 1m diameter. The brake drum is provided with
four cast iron brake shoes each subtending an angle of 45. The
mass of the elevator when loaded is 2000 kg and moves with a
speed of 2.5m/s. the brake has a sufficient capacity to stop the
elevator in 2.75m. Assuming the coefficient of friction between
the brake drum and shoes as 0.2, find
(a) width of the shoe, if the allowable pressure on the brake shoe
is limited to 0.3N/mm2.
(b) heat generated in stopping the elevator.