DTS

1. 5616169
B.Tech. DEGREE EXAMINATION, APRIL/MAY 2017
Sixth semester
Mechanical Engineering
DESIGN OF TRANSMISSION SYSTEMS
Part A
1. What are the commonly used materials for sliding contact bearing?
Commonly used materials for sliding contact bearings are: Babbits (white metals), Bronze,
Aluminium alloys, Copper-lead alloy, Cast iron, Sintered metal or porous metal, on-metallic materials.
2. What are rolling contact bearings?
A rolling Contact bearing, also known as a rolling bearing, is a bearing which carries a load by
placing rolling elements (such as balls or rollers) between two bearing rings called races. The relative
motion of the races causes the rolling elements to roll with very little rolling resistance and with little
sliding.
3. Write two factors upon which the coefficient offriction between the beltand the pulley depends.
The factors are,
 Materials of the belt and pulley
 Slip of belt
 Speed of belt
 Smoothness of contact surfaces.
4. What are the advantages ofthe gear drives over other type ofdrives?
 Gear drives are positive drives.
 Suitable for shorter centre distance.
 The gear drives are better than others in case of amount of power transmission and efficiency.
 Change of speed is very easy in gear drives
5. What are the failures ofgear tooth?
Gera Tooth failures are:Tooth breakage, Surface failure, Abrasion, Seizure/scaring, Pitting.
6. What are the applications ofbevel gear?
Bevel gears are used in
 Rear axle drives of automobiles
 Vertical spindle of a drilling machine
 Elevating screws of cross rail of planner
 Milling & shaping machine.
7. What is a pivot in a chain?
Pivot is a point which connects the pin with link plate, so that the chain turns with respect to the
pivot point.
8. What is self-locking in worm gear drive?
A self-locking gear cannot be driven by the load in the opposite direction from its intended
direction of rotation; this means that worm gear cannot drive the worm.
9. Give two application of the speed reducer.
The speed reducer are used in turbine generators, between motor and machine tools, in rolling
mills, between engine and road wheels in automobile and in many industrial processing like cement
factories, paper – plants, chemical industries etc.
10. What is a multi-speed gearbox?
A Multi speed Gearbox is a mechanical device that is used to provide Speed and Torque
conversions from a rotating power source to output shaft. As the speed of the shaft increases, the torque
transmitted decreases and vice versa. Multi-speed gearboxes are used in applications which require
frequent changes to the speed/torque at the output shaft.

4. 12. A ball bearing for a drilling machine spindle is rotating at 300 rpm. It is subjected to a
radial load of 2000 N and an axial thrust of 1000 N. It has to work 45 hours/week for one
year. Designa suitable ball bearing, if the diameter of the spindle is 40 mm.

5. 13. Design a flat drive to transmit 25kW power at 720 rpm to an aluminium rolling
machine, the speed reduction being 3. The distance between the shafts is 3 m. Diameter of
rolling machine pulley is 1.2 m.

6. 14. Design a chain drive to activate a compressor from a 15 kW electric motor at 960 rpm. The
compressor speed 300rpm. The minimum centre distance be adjustable. The chain tension may be
adjusted by shifting the motor on rails. The compressor is to work 8 hours/day.

8. A= bearing area 140 mm2
. Since this more than the allowable bearing stresses whose value is 22
N/mm2
. Let us select a higher strength chain as TR 50 chain whose breaking strength is 66600 N
and bearing area is 210 mm2
.
Theinducedstressis lessthan allowablestress,theselectionofTR50chainsatisfactory.