2. Mechanical Engineering Design

3. : Contents Preface ……………………………………4 What is a gearbox?………………………5
Project description………………………..7
Bulky characteristics of gearbox………..8
Gear design……………………………….9
Shaft design………………………………34
Deflection consideration…………………37
Bearing selection…………………………41
Computer programming…………………54
Acknowledgments………………………..55
References………………………………..56

4. Preface:
The present work is a class project of mechanical engineering design
on Samand’s gearbox. The quad did as much as possible in order to
analyze ,collect, calculate and present the results. At first we have a
historical vision on gearbox then all the parts of gearbox’s
evaluations (some with more details) will be considered. we have
utilized some CAD soft wares like ANSYS,solidworks , catia &Mdesign and the programming is MATLAB language.
We are really grateful of Dr.vakili on behalf of the recommendations and hope to satisfy him about the process.

5. ? What is a gearbox Gears are about as old as any of
the machinery of mankind. The oldest machine
is the potter's wheel. At first time over 3000
years ago primitive gears first meshed
with each other and transmitted rotary motion .
Water wheels were used to convert energy of
moving water into energy that would power
machines. Wooden gears connected water
wheels to machines that would grind wheat
and hammer metals.
A transmission or gear box provides speed
and torque conversion and from a rotating
power source to another device using gear
ratios. In British English the term
TRANSMISSION refers to the whole drive
train, including gearbox, clutch, prop shaft,(
for rear wheel drive), differential and final
drive shafts. The most common use is in
motor vehicals,where the transmission
adapts the out put of the internal combustion
engine to the drive wheels.

6. Often, a transmission will have multiple gear ratios (or simply
"gears"), with the ability to switch
between them as speed varies.
This switching may be done
manually (by the operator), or
automatically. Directional (forward
and reverse) control may also be
provided. Single-ratio
transmissions also exist, which
simply change the speed and torque (and sometimes
direction) of motor output .
Gearboxes have found use in a wide variety of different—often stationary—applications, such as wind turbines.
Transmissions are also used in agricultural, industrial, construction, mining and automotive equipment. In addition to ordinary transmission equipped with gears, such equipment makes extensive use of the hydrostatic drive and electrical adjustable-speed drives.

7. Project description
It is desired to design a gearbox To get this we first anaylzed
the forces and power generated in the internal combustion engine
then according to the inpute data like the maximum torque and maximum power gears designed Then by considering the shasfts distans and gears diameters the critical gear mated during the engaging identified Then all diameters of shafts were found out It is important to note that we used some steps through the shafts inorder to reduce the material used in manufacturing
At last all the bearings were selected for the most critical
condition and all the data and informations were wrote besides .the figures

8. Bulky characteristics of gearbox
39.15Kg
Total weight
420mm
length
240mm
width
310mm
height
0.0312m^3
Occupied volume
195$
Approximate cost
150(mm)
Normal distance of shafts
360mm
Upper shaft length
410mm
Lower shaft length
40mm
Distance of gear 5,4
5mm
Distance of gear 4,3
20mm
Distance of gear 3,2
Distance of gear 2,REV
60mm
Distance of gear REV,1

9. Gear design
There are some important notes to be informed. First we calculated the power generated ,from some principle physics and fluid mechanics. During the engaging of the gears to the higher speeds, the power increases and the torque reduces. For the rear gear we assumed the conditions as well as 1stt gear,inorder to have the worst situation. the assumption for the overload factor was according to the speed of the shaft. when we have low speeds it should be less than 1.5 and when the speed increases ,the unbalanced forces increases and the overload factor shouldn’t be less than 2.The gear strength for live assumed 10^8 cycles & the reliability was set 99%.Temperture factor was not considered. The surface condition factor was almost 1 because of our gear materials. All the gears are from steel but different hard nesses.

10. Gear1(pinion): Mn D N F Material W H Ko Wt*nd SF SH Qv 2.5 70mm 24
St,grade2
,550HB
Material
3000rpm W
64.5hp H
13128N
Wt*nd 20 n 30 1 Ko
1.2 SF SH 8 Qv

11. (more details)

12. Gear1(gear): Mn D N F Material W Ko H SF Wt*nd SH Qv 2.5 230mm 80 40mm
St,grade2
,550HB
Material
913rpm W
64.5hp H
13128N
Wt*nd 20 n 30 1 Ko
1.4 SF
1.3 SH 8 Qv

13. (more details)

14. Rear gear (pinion): Mn D N F Material W H Ko Wt*nd SF SH Qv 2.5 70mm28 N
40mm F
St,grade2
Carburized & hardened
Material
3000rpm W
64.5hp H
13128N
Wt*nd 20 n
1.25 Ko
1.5 SF
1.2 SH 8 Qv

15. (more details):

16. Rear gear (gear): Mn D N F Material W H Ko Wt*nd SF SH Qv 2.5 230mm 92
St,grade2
Carburized & hardened
Material
913rpm W
64.5hp H
13128N
Wt*nd 20 n
1.25 Ko
1.02 SF
1.1 SH 8 Qv

17. (More details)

18. 2nd gear (pinion): Mn D N F Material W Ko H SF Wt*nd SH Qv 4 105mm 22
St,grade2
Carburized & hardened
Material
3700rpm W
70hp H
7700N
Wt*nd 20 n 30
1.5 Ko 2 SF
1.2 SH 8 Qv

19. (more details)

20. 2nd gear (gear): Mn D N F Material W H Ko Wt*nd SF SH Qv 4 195mm 42
St,grade2
Carburized & hardened
Material
2000rpm W
70hp H
7700N
Wt*nd 20 n 30
1.5 Ko 2 SF
1.2 SH 8 Qv

21. (More details)

22. 3rd gear (pinion): Mn D N F Material W H Ko Wt*nd SF SH Qv 4 130mm 30
St,grade2
450HB
Material
4500rpm W
80hp H
5845N
Wt*nd 20 n 30
1.5 Ko 2 SF
1.12 SH 9 Qv

23. (more details)

24. 3rd gear (gear): Mn D N F Material W H Ko Wt*nd SF SH Qv 4 170mm 40
St,grade2
450HB
Material
3440rpm W
80hp H
5845N
Wt*nd 20 n 30
1.5 Ko 2 SF
1.12 SH 9 Qv

25. (more details)

26. 4th gear (pinion): Mn D N F Material W H Ko Wt*nd SF SH Qv 4 152mm 33
St,grade1
300HB
Material
5300rpm W
90hp H
4775N
Wt*nd 20 n 30 2 Ko
1.1 SF SH 9 Qv

27. (More details)

28. 4th gear (gear) Mn D N F Material W H Ko Wt*nd SF SH Qv 4 148mm 32
St,grade1
300HB
Material
5443rpm W
90hp H
4775N
Wt*nd 20 n 30 2 Ko
1.1 SF SH 9 Qv

29. (More details)

30. 5th gear (pinion) Mn D N F Material W H Ko Wt*nd SF SH Qv 4 172mm 38
St,grade1
350HB
Material
6000rpm W
100hp H
4140N
Wt*nd 20 n 30 2 Ko
1.1 SF
2.5 SH
9-10 Qv

31. (More details)

32. 5th gear (gear) Mn D N F Material W H Ko Wt*nd SF SH Qv 4 128mm 28
St,grade1
350HB
Material
8062rpm W
100hp H
4140N
Wt*nd 20 n 30
2.5 Ko
1.1 SF SH
9-10 Qv

33. (More details)

34. Shaft design:
Now it is the time to design the shafts. The most important note is the gears weight. For the upper shaft, we assumed concentrated weight at the center of the gears but at the lower shaft because of their large size, we assumed uniform distributed force. The other note is the steps. During the calculation, we saw that there are some parts that can be manufactured with less diameters. saw we considered some steps and used 3mm fillet radius. The fatigue failure was one of the important factor. this is stated after evaluating the other parameters like critical frequency and defelction.the SODERBERG was the relation for the fatigue failure. The deflection would result in larger diameters, so we used one more bearing in each shaft to reduce the deflection.
The calculations resulted in the critical condition when engaging the rear or the 1st gear. so we examined the gear 4 in order to reject it as the bad condition then we solved the problem on the base of rear and 1st gear.

35. Upper shaft: 36mm 50mm 45mm 1030HR Diameters from left to right
Critical situation
is when rear
gear is engaged.
36mm
50mm
45mm
Diameters from left to right
1030HR
Material

36. Lower shaft: 50mm 47mm 34mm 1045 CD Diameters from left to right
Critical situation
is when rear
gear is engaged
50mm
47mm
34mm
Diameters from left to right
1045 CD
Material

37. Deflection considerations(ANSYS)
Other gears just vanished.
Modeling

38. Showing the fillets of the steps.
Uniform load distribution of the gear.

39. (before middle bearing) (after middle bearing)
Stress distribution.
(before middle bearing)
Stress distribution.
(after middle bearing)

40. (after middle bearing) (after middle bearing)
Stress distribution.
(after middle bearing)
Stress distribution.
(after middle bearing)

41. Bearing selection:
We were supposed to select 4 bearings ,two for the upper shaft and two for the lower shaft. But when evaluating the deflections we saw that it is worth to try the 3rd bearing for each shaft and reduce the undesirable deflection which can cause force increased during the engaging. So we did it and
According to the critical forces, we selected the suitable bearing from SKF online bearing selection for a long life.Ofcourse in bearing selection, its diameters ,mass and cost were considered.

42. Upper shaft (right side):

43. Upper shaft (right side):

44. Upper shaft (Left side):

45. Upper shaft (Left side):

46. Upper shaft (middle)

47. Upper shaft (middle)

48. Lower shaft( right side)

49. Lower shaft( right side)

50. Lower shaft( left side)

51. Lower shaft( left side)

52. Lower shaft (middle)

53. Lower shaft (middle)

54. Computer programming:
In order to computerize the evaluations ,we wrote the program which gets some input data like m,Np,Ng,Wt,speed and some others and predicts the coefficient of safety for pitting and bending.Ofcourse we are really grateful of Mr.milanchiyan for his prior program which we have extended it .There is an animation which shows the operation.

55. Acknowledgment:
At first we really thanks GOD which provided the conditions in order to work on the project as much as possible. Then we are really grateful of our wise master,Dr.vakili on behalf of the recommendations. We really thanks from TAKARAN CO(ISACO bureau in TEHARAN) , our dear engineer ,Mr.Ghorbani and our classmate Mr.milanchiyan.We hope to develop our performance in future works.enshalah….

56. References:
1.Budynas,Nisbett,shigley’s mechanical engineering design,6th,7th,8th edition,Mc graw Hill,
2 .دکتر محمد رحیمیان،تحلیل و طراحی توسط نرم افزار ANSYS
3.طراحی در ANSYS،نیما جمشیدی،مجموعه کتابهای مثلث نارنجی 4.

57. The Group: