1. Chapter 15 Shafts Key Terms: shaft spacer bearing cap shaft shoulder
flexible retaining ring
fixed retaining ring
torque diagram
bending moment diagram

2. bearing
gear
A shaft is an important component which used to support rotating elements and transmit rotational motion and power.
shaft

3. 15.1 Types and Materials of Shafts
1) according to the loads:
a. Shafts with bending and torsional moments
b. Shafts with only bending moments, i.e. axle,
c. Shafts with only torsional moments, i.e. spindle

9. 2) according to the axle shapes
straight shafts
crank shafts
flexible shafts

10. No-diameter-change Shafts

11. Crank Shafts

12. Flexible Shafts

14. 2. Materials table 15.1 15.3 Considerations for Shaft Geometry
The location of elements on shaft;
2) The mount & dismount of elements on shafts;
3) The way of improving the strength of shafts;
4) Manufacturability of shafts ;
5) Diameter and length of shafts.

16. 1. The location of elements on shafts
1) Axial location
a. shaft shoulder
Location shoulder (①②⑤):
h=(0.07~0.1)d
Non-location shoulder (③④):
h=1~2mm

17. Note: 1) Height of shoulder should be smaller
than that of bearing inner race;
2) Radius of shaft fillet should be smaller
than that of fillet or chamfer on bore of
mating element: r<R;

18. right
wrong

19. b. spacer

20. c. bearing cap

21. d. locknut & setscrew

22. e. flexible retaining ring

23. f. fixed retaining ring

24. g. end cap

25. 2) radial location
spline
key

26. pin
press fit

27. 2. The mount and dismount of elements on shafts

30. 3. The way of improving the strength of shafts

31. 4. manufacturability of shafts

33. 5. Diameter and length of shafts
1) Specify dmin:
2) d1=dmin+2h, d2=d1+2h, ……
3) Length is dictated by the element to be mounted there.

34. Note
1) Diameter of shafts should be compatible with the diameter of elements mounted on the shafts. such
as rolling contact bearings and couplings.
2) The length of shaft should smaller than mating length of the hub of the element on the shaft.

38. Example
There are some mistakes in a shaft system shown below, pick them out and explain.

39. 1- axial have not located 2- circumferential has not located
Solution
1- axial have not located
2- circumferential has not located
3- axis segment sizes should short in gear wheel hub length 2~3mm
4- sleeves should not surpass the bearing inner loop altitude highly
5- shoulders should not surpass the bearing inner loop altitude highly

40. 6- are unable the assembling and dismantling, the application circlip
7- between the end covers and the axis should have the gap
8- should make a connection with
9- key to be too long, the sleeve place should not have the key
10- the axis should have stair

41. 15.3 The Strength of Shafts 1. Designing shafts only by shear stress
T——torsional sheer stress
P——transmitted power
n——rotational speed of shaft
WT——section modular of shaft, table 15.3
[T]——permissible torsional sheer stress,
table15.2

42. C——coefficient, table 15.2

43. 2. Designing shafts with combined bending and torsional stressFr Ft T

44. Procedures 1) Prepare the loading diagram.
Determine the forces that are exerted on the shaft for perpendicular planes.
Distributed Loads concentrated forces exerted on the midpoint of hub.
Specify the location of bearing to support the shaft.

46. 2)Prepare the bending moment diagrams for two perpendicular planes of the shaft.
3)Prepare the resultant bending moment diagram of the shaft.
4)Prepare the torsional moment diagram of the shaft.
5)Prepare the equivalent bending moment diagram of the shaft.

47. According to the third strength theory:

48. ——coefficient related to the variation ways of the torsional moment compared with bending moment
, for constant torsional moment
, for pulsanting moment
, for reversing torsional moment

49. Check Equation:
Design Equation:

50. 3. Checking the fatigue Strength of the Designed Shaft
Where

51. Example

54. （GB/T ）

56. 15.2 The Procedure of Shaft Design
1) choose material;
2) asks most minor diameter dmin;
3) axis structural design;
4) axis intensity examination.

58. Solution 1- bearings have not located
2- axis segment sizes should be supposed to be lower than the bearing inner loop altitude highly short in the wheel hub length
3- sleeves
4- should make steps and ladders
5- to be too long between
6- end covers and the axis should have the gap
7, 8- should add the adjusting shim

59. The end Thanks!