UNIT-VI

SPUR & HELICAL GEAR DRIVES

Short Answer Questions

1. In which gears, is the axial thrust minimum?

2. For non-intersecting perpendicular shafts, the gears used are_______________.

3. In case of spur gears, the higher pressure angle results in ________________.

4. The minimum number of teeth on a pinion for 14-½ full depth system is

_____________.

5. The size of the gear working depth is equal to _________________.

6. For a gear, working depth is equal to _____________________.

7. The product of diameteral pitch and circular pitch of a gear is equal to

_____________.

8. If the number of teeth on two bevel gears in inch is 30 and 60, then cone pitch

angle of the gear will be________________.

9. In the above problem the cone pitch angle of the pinion will be ______________.

10. The minimum number of teeth on the pinion for 20 degree full depth system is

_______________.

11. Contact ratio for a gear is in the range of ______________________.

12. The helix angle for single helical gears ranges from ________________.

13. An automobile gearbox has ____________________ gear train.

14. Which type of gear profile is free from interference?

15. Low pressure angle on gears results in _____________.

16. Give the reason why operation of helical gears is silent and quite while the

operation of the spur gear is noisy.

17. The characteristic of a cycloidal tooth profile is ____________________.

18. In a gear box the input torque is 40 Nm (CCW) and is overcoming a CCw torque

of 80Nm. The net torque on the gear box casing is ________________.

19. When bevel gears having equal teeth and equal pitch angle connect two shafts

whose axes intersect at right angle, they are known as________________.

20. Specify the reasons for using stub tooth on gears.

21. What is the function of gearbox in an automobile?

22. The number of starts on the worm for a velocity ratio of 40 should

be____________________.

23. In the worm gears, the angle between the tangent to the thread helix on the pitch cylinder and the plane normal to the axis of worm is called ______________.

24. The radial distance of a tooth from the pitch circle to the top of the tooth is called

______________.

25. An imaginary circle which by pure rolling action gives the same motion as the actual gear is called as _______________.

26. Gears are termed as medium velocity gears if their peripheral velocity is

__________.

27. When two non coplanar non intersecting shafts are connected through gears, the arrangement is known as _____________________.

28. Specify the configuration of axes of shafts in skew bevel gearing. 29. The minimum no. of teeth on the pinion is 12 for which system. 30. Automobile gears are made of ______________ material.

31. Specify the position of the axes of the shafts in case of hypoid gears.

32. Specify the position of the axes of the shafts in case of bevel gears.

33. What do you mean by Herringbone gears? 34. The dedendum circle diameter is equal to ________________.

35. Backlash for spur gears depends upon____________________.

36. The ratio of pitch circle diameter in ‘mm’ to the no. of teeth is called

______________. 37. The difference between the tooth space and the tooth thickness along the pitch

circle is known as __________________. 38. The contact ratio of two meshing gears is the ratio of ________________.

39. For a gear with involute tooth profile, $ is the pressure angle, center distance

between two mating gears is equal to______________________.

40. Lewis equation for gears is used to find ____________________ stress.