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International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072
© 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 678
Design and Analysis of an 8-Speed Gear box.
Abhishek Chavan1, Abhiraj Baji2, Yash Darakh3, Chinmay Inamdar4
145Department of Mechanical Engineering, Vishwakarma Institute of Technology, Pune-48, Maharashtra, India
---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract - Lathe Machine is used in all the engineering
applications and in the college Workshops. Lathe machine is
used to perform all the basic operations such as drilling,
cutting, tapping, turning, etc. with the help of different tools
placed in the work environment There are 2 main types of
Lathe machines: Capstan Lathe and Turret Lathe. Turret
Lathes use a turret head to perform operations. A turret head
is a vertical cylindrical revolving tool-holder for bringing
different tools into action successively in the lathe machine.
The turret head needs to rotate at different speeds to perform
different operations on the workpiece. This is controlled by a
gearbox. A gearbox which converts high speed input into
various output speeds is called a multi speed gearbox. A 6-
speed gearbox is usually used. But 8-speed and 9-speed
gearboxes give a wider range of speeds and efficiency. The
aim of this project is to design and analyze 8-speed
gearbox which meets the functional requirements of a
turret gearbox. Design and Analysis have been conducted
and a detailed study has been performed for various
components in the gearbox.
Key Words: Lathe, Gearbox, Turret, Gears, Shaft, Ray
Diagram, etc.
1. INTRODUCTION
Ever since the development of the first gearbox by
Sturtevant in 1904 for automobileapplication,theutilisation
of this technology has evolved marking its presence in
various industrial sectors like power generation, petroleum
refining, mining and material handling,metal processingand
so on. Considering the metal processing and machining
aspect, a wide range of industrial gearboxesareusedinlathe
machines. These gearboxes offer a vivid range of operating
speed, and the main aim of this project is to design an 8-
Speed gearbox for using in turret lathe machines.
1.1 Deciding Input Requirements
Speed Requirement: Aftera comprehensivestudyonspeed
ranges (Nmin and Nmax) for turret lathe, we arrived at a
generic average value of 100rpm to 1100rpm. These values
are optimal for further processing and give a better design
result as compared to other experimental values as well.
Torque Requirement: Turret lathe gearboxes usually
require a power of approximately 5-8kW [2].
Motor Selection: Motor selection has been done taking
power and input speed conditions into account. An
approximate 8.5HP(6.33kW) and 650rpm motor has been
selected. The values will be explained further on in the
project.
1.2 Deciding Material
After trial and error with various materials in the design
process and opinions of industry professionals,materialsfor
the following components were decided mainly based on
strength and durability.
Gear: All the gear are made from ‘Grey Cast Iron’.
Shaft: All the shafts have been made of the material ‘Steel
FeE 580’.
Keys and keyways: All the keys have been made out of
‘Steel 50C4.’
Casing: The casing has been made from ‘Cast Iron’.
2. DETAILED DESIGN PROCEDURE
2.1 Derivation of Structural Formula
The structural formula gives information about various
aspects of the gearbox like number of shafts, number of
gears and a basic idea of transmission pairs. It tells about
transmission range as well. The procedurefollowedtoreach
the structural formula is explained below.
Law of Discretizing Speeds: Discretizing speeds between
minimum speed and maximum speed is very important to
know our output speeds. These speeds are decided by three
basic laws as depicted in the table below.
Fig -1: Laws of discretizing speeds.
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072
© 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 679
Justification of using Geometric Progression: The speeds
in gear boxes can be arranged in arithmetic progression
(A.P.), geometric progression (G.P.), harmonic progression
(H.P), and logarithmicprogression(L.P.).However,when the
speeds are arranged in G.P., it has the following advantages.
 The speed loss is minimum i.e., Speed loss=Desired
optimum speed – Available speed
 The number of gears to be employed is minimum.
 G.P. provides a more even rangeofspindlespeedsat
each step.
 The layout is comparatively very compact.
 Productivity of a machining operation, i.e., surface
area of the metal removed in unit time, is constant
in the whole speed range.
 G.P. machine tool spindle speeds can be selected
easily from preferred numbers. Because preferred
numbers are in geometric progression.
Deciding Speed Ratio from Standard Series: In gearbox
design a set of preferred step ratio or preferred numbers is
used to obtain the series of output speed of gearbox. The
preferred step ratio is mentioned as basic series named as
R5, R10, R20, R40 and R80. Each basic series has a specific
step ratio. In our case, we have Nmin as 100rpm and Nmax as
1100rpm.
Thus,
The Step Ratio 1.4 comes under R20 series.
Thus, the spindle speeds calculated are:
N1 = = 100rpm
N2 = = 140rpm
N3 = = 196rpm = 200rpm
N4 = = 274.4rpm = 280rpm
N5 = = 392rpm = 400rpm
N6 = = 560rpm
N7 = = 784rpm = 780rpm
N8 = = 1097rpm = 1100rpm
These are subject to change based on number of teeth
chosen.
Deriving Structural Formula:
Let,
n = Number of speeds available at the spindle.
p1, p2, p3….. = stage numbers in gearbox.
X1, X2, X3….. = Characteristics of the stages.
Then, structural formula is given as:
N = p1(X1).p2(X2).p3(X3).p4(X4)
Were,
X1 = 1; X2 = p1; X3 = p1 x p2; X4 = p1 x p2 x p3
Table -1:
SR NO: Number of speeds Preferred Structural Formula
1 6 Speeds 3 (1) . 2 (3)
2 (1) . 3 (2)
2 8 Speeds 2 (1) . 2 (2) . 2 (4)
4 (1) . 2 (4)
3 9 Speeds 3 (1) . 3 (3)
4 12 Speeds 3 (1) . 2 (3) . 2 (6)
2 (1) . 3 (2) . 2 (6)
2 (1) . 2 (2) . 3 (4)
For 8 – Speed Gearbox:
2 x 2 x 2 = 8
Therefore,
P1 = 2, X1 = 1
P2 = 2, X2 = 2
P3 = 2, X3 = 2 x 2 = 4
Then, structural formula = 2 (1) . 2 (2) . 2 (4)
Determining number of Shafts, Gears and
Transmissions: Calculation of No. of shafts to draw
kinematic arrangement:
No. of shafts = No. of stages + 1.
That is,
If 3 stages are there in gearbox design, then no. of shaft will
be = 3 + 1 = 4 shafts.
As per gear kinematics,
Shaft 1 = p1 gears = 2 gears.
Shaft 2 = (p1 + p2) gears = 4 gears.
Shaft 3 = (p2 + p3) gears = 4 gears.
Shaft 4 = p1 gears = 2 gears.
Limiting Value of (Ig)stage:
2.2 Structural Ray Diagram
Drawing Structural Ray Diagram: The ray diagram is
graphical representationofthedrivearrangementingeneral
from. In other words, the ray diagram is a graphical
representation of the structural formula, as shown in figure.
It provides the following data on the drive:
 The number of stages (a stage is a set of gear trains
arranged on two consecutive shafts).
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072
© 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 680
 The number of speeds in each stage.
 The order of kinematic arrangement of the stages.
 The specific values of all the transmission ratios in
the drive.
 The total number of speeds available at the spindle.
Procedure: The following is the procedure to plot
structural ray diagram:
 In this diagram, shafts are shown by vertical
equidistant and parallel lines.
 The speeds are plotted vertical on a logarithmic
scale with log  as a unit.
 Transmission engaged at definite speeds of the
driving and driven shafts are shown on the diagram
by rays connecting the points on the shaft lines
representing these speeds.
 Figure shows the ray diagram for a 9-speed gear
box, having the structural formula, Z = 2 (1). 2 (2).
2(4).
Fig -2: Structural Ray Diagram
2.3 Speed Ray Diagram:
Significance: A speed ray diagram is a diagram depicting all
possible exact values of speeds at which the multi speed
gearbox can run. It gives us a clear picture of gear ratios as
well.
Plotting Speed Diagram: A basic procedure which is
followed is as follows-
 Draw u+1 vertical line atconvenientdistance where
u= Number of stages (for above formula u=4 three
transmission group) Note : first vertical line
represents the transmission from motor shaft and
the rest represent the transmission groupsofspeed
box. 2).
 Draw array of horizontal lines is equal to the
number of speed steps z of speed intersecting the
vertical lines distance of log Ø from each other.
Fig -3: Speed Ray Diagram
2.4 Preliminary Gearbox assembly:
Basic Assembly Diagram Optimisation: The following
diagram shows the basic gearbox assembly where Gn is the
number of the nth gear and Zn is number of teeth of Gn
th gear.
Fig -4: Preliminary Gearbox assembly
2.5 Determining Gear Ratios and Number of teeth:
Approximating Gear Ratio from Speed Ratio and
Constraints: As we have seen in the picture above,thereare
12 gears of which we need to find the numberofteeth.There
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072
© 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 681
are a few constraints to take care of after which we can
easily select number of teeth from the design data book.
The summation of number of teeth of the meshing gears
between two shafts should be exactly equal.
m = constant for all
thus,
thus,
similarly,
and
Therefore, by selecting standard number of teeth from
design data book to satisfy the above given gear ration
equation, we get the following number of teeth per gear:
Table -2:
Gear Number Number of Teeth
01 Z01 = 20
02 Z02 = 25
03 Z03 = 45
04 Z04 = 40
05 Z05 = 24
06 Z06 = 34
07 Z07 = 34
08 Z08 = 24
09 Z09 = 20
10 Z10 = 40
11 Z11 = 40
12 Z12 = 20
Corrected final speeds:
Old Speed
(rpm)
New Speed
(rpm)
Difference
(rpm)
% Change
100 98 2 2%
140 137 3 2.1%
200 196 4 2%
280 276 4 1.4%
400 392 8 2%
560 551 9 1.6%
780 787 7 0.8%
1100 1106 6 0.5%
2.6 Determining final gear dimensions:
Determination of module:
Fig - 5: Determination of Module
By our calculations, we got a module of 2.8. Rounding this
off, we chose a module of 3mm.
Module m = 3mm.
Determination of Gear diameter:
Gear Number Diameter of Gear (mm)
1 D1 = m*Z1 = 60
2 D2 = m*Z2 = 75
3 D3 = m*Z3 = 135
4 D4 = m*Z4 = 120
5 D5 = m*Z5 = 72
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072
© 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 682
6 D6 = m*Z6 = 102
7 D7 = m*Z7 = 102
8 D8 = m*Z8 = 72
9 D9 = m*Z9 = 60
10 D10 = m*Z10 = 120
11 D11 = m*Z11 = 120
12 D12 = m*Z12 = 60
Determination of Gear dimensions:
We have selected 20 full depth involute teeth system. As we
input our module, system of teeth and number of teeth into
Solid works, it gives us the remaining outputs.
Fig - 6: Types of teeth system
By considering 20-degree full depth system:
 Addendum (ha) = m = 3mm
 Dedendum (hf) = 1.25 m = 3.75mm
 Clearance (c) = 0.25 m = 0.75mm
 Working depth (hk) = 2 m = 6mm
 Whole depth (h) = 2.25 m = 6.75mm
 Tooth thickness (s) = 1.5708 m = 4.7mm
 Tooth space = 1.5708 m = 4.7mm
 Filet radius = 0.4 m = 1.2mm
Weights of individual gears:
Post obtaining the dimensions required for each gear, we
design them on modelling software and then obtain the
weights as follows:
Sr. No. Gear with teeth Weight(N)
1 20 4.28
2 24 6.76
3 25 7.595
4 34 14.98
5 40 21.98
6 45 28.616
Design of shaft:
Torque input to individual shafts: The selected motor
provides an input power of 6.33kW to the initial shaft. The
first shaft rotates at 625rpm. From the formula,
We get Torsional moment of first shaft T1 = 96.71 N-m.
Similarly, finding out all the possible torsional moments of
all shafts, we consider the maximum one for calculation
purposes. The results are tabulated as follows:
The torques marked in red are the highest torques acting on
the respective shafts. This be our torsional moments to be
considered during design.
Calculation and Direction of Gear Forces: There are 3
main types of forces acting when a gear pair meshes. They
are as follows:
 Tangential Force Ft: The force acting tangential to
the gear surface at the point of contact with
meshing gear.
 Radial force Fr: The force actingtowardsthecentre
of the gear at the point of contact with the meshing
gear.
 Axial Force Fa: The force that acts in thez-direction
along the shaft due to the angle of the teeth is the
axial force. As our teeth don’t have an angle with
respect to the gear base, this force for our
consideration, is 0.
As our gearbox is a spur gear system, we will consider the
tangential and radial forces of all gears for calculation
purposes.
For each gear
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072
© 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 683
Gear Force Type Value
(N)
G1 Tangential force Ft 3223.6
Radial Force Fr 1173.3
G2 Tangential force Ft 2758.9
Radial Force Fr 938.65
G3 Tangential force Ft 322.2
Radial Force Fr 117.28
G4 Tangential force Ft 362.5
Radial Force Fr 131.93
G5 Tangential force Ft 426.47
Radial Force Fr 115.22
G6 Tangential force Ft 604.16
Radial Force Fr 219.89
G7 Tangential force Ft 427.78
Radial Force Fr 115.69
G8 Tangential force Ft 301.96
Radial Force Fr 109.90
G9 Tangential force Ft 513.33
Radial Force Fr 186.83
G10 Tangential force Ft 256.67
Radial Force Fr 93.41
G11 Tangential force Ft 513.33
Radial Force Fr 186.83
G12 Tangential force Ft 1026.6
Radial Force Fr 373.67
Modified Weight of Gear: From Solid works, we have the
weight of the solid gear. As there will be a shaft of diameter
‘d’ through this, we must reduce that much weight.
Therefore, giving a new modified weight to work with.
Let,
Wnew = Modified Weight in Newton
Wold – Solid works output weight in Newton
Wr - Weight of Inner part to be removed in Newton.
d – diameter of shaft in m
f – face width of gear in m
ρ – density of gear in kg/m3
g – acceleration due to gravity in m/s2
Fig -1: Name of the figure
Wnew = Wold – Wr
Wr = Weight of cylindrical part of gear
Wr =
Calculating Maximum Bending Moment for each Shaft:
Our aim right now is to calculate maximum bendingmoment
acting on the shaft for the calculation of shaft diameter. This
can be done in terms of ‘d’ as all values in our SFD are in
terms of ‘d’.
The maximum bending moment isarea betweentheSFDand
the shaft axis above the shaft axis and the point of maximum
bending is the point where the SFD graph crosses the shaft
axis. Thus, calculating the areas, we get the followingresults.
Shaft Maximum Bending
Moment (Mb)
Maximum Torsional
Moment (Mt)
1 252261.7 346544.50
2 282504.30 264387.4
3 294134.50 357548.00
4 263150.23 346753.82
Determining Shaft Diameter: We will be designing the
shaft using ASME code of shaft design. According to this
code, the permissible shear stress τmax for the shaft without
keyways is taken as 30% of yield strength in tension or 18%
of the ultimate tensile strength of the material, whichever is
minimum. Therefore, τmax = 0.30 Syt or τmax = 0.18 Sut
(whichever is minimum).
If keyways are present, the above values are to be reduced
by 25 per cent. According to the ASME code, the bendingand
torsional moments are to be multiplied by factors kb and kt
respectively, to account for shock and fatigue in operating
condition. The ASME code is basedonmaximumshearstress
theory of failure.
were,
d
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072
© 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 684
kb = combined shock and fatigue factor applied to bending
moment
kt = combined shock and fatigue factor applied to torsional
moment
Mb = Maximum Bending moment acting on shaft
Mt = Maximum torsional moment acting on shaft
Fig -7: Shock and fatigue factors
For the gearbox, it is a minor shock application. Thus, the
load is applied suddenly. We have taken as intermediate
value of kb = 1.5-2.0 and kt = 1.0-1.5.
Our shaft material is ‘Steel FeE 580 (Sut = 770 and Syt = 580
N/mm2).
Calculating permissible shear stress,
0.30 Syt = 0.30(580) = 174 N/mm2
0.18 Sut = 0.18(770) = 138.6 N/mm2
The lower of the two values is 138.6 N/mm2 and there are
keyways on the shaft.
τmax = 0.75(138.6) = 103.95 N/mm2
Combining values of τmax from both above equations,
Using max bendingmoment andtorsional momentvalues for
each shaft, we get the following shaft diameters which are
taken in accordance with the standard shaft table.
Fig -8: Shaft diameters
Shaft Number Shaft diameter (mm)
1 28
2 30
3 30
4 28
2.7 Design of keys and keyways:
Type of key: There are various types of keys. We have
selected Rectangular Saddle Key. Its design has been
conducted as follows.
Design on load basis: The material for key is Steel 50C4(Syt
= 460 N/mm2) and the factor of safety is taken as 3. For key
material, the yield strength in compression can be assumed
to be equal to the yield strength in tension. Keyways are on
the second and fourth shaft.
Syc = Syt = 460 N/mm2
N/mm2
According to maximum shear stress theory of failure,
Ssy = 0.5*Syt = 0.5(460) = 230 N/mm2
b – breadth of key
h – height of key
l – length of key
d – diameter of shaft
Industry standard is to select a basic dimension of
b = h = d/4 = 30/4 = 7.5 = 7mm
or
Taking maximum value using both equations, we get key
length = 28.7mm
Now selecting from standard table,
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072
© 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 685
Fig -9: Determination of keys and keyways
Thus, we select the key with dimension (b,h) as (8,7) and a
length of 30mm.
Fig -10: Shafts
2.8 Selection of bearings:
Defining Bearing Life: To select bearings, it is necessary to
specify life of the bearings. This can be done from standard
bearing selection table. The recommended bearing life for
gear applications is given in the table below:
Fig -11: Bearing life.
The values given in the above table are only for general
guidance. For a particular application, the designer should
consider the experience, the difficulties faced by the
customer in replacing the bearing and the economics of
breakdown costs.
As we are relatively new to the designing aspect, we have
taken an estimated 15,000 hr( due to it being an
intermediate value for a service machine.
Selection from Manufacturer’s Catalogue: To select the
final bearings, we will need radial force acting. As thereis no
axial force, total force P = Fr. Diameter of all 4 shafts are
taken into consideration. Then using max speed of all shafts,
we calculate the rated bearing life L10 by the formula,
After we get this value for all shafts, we calculate the
dynamic load capacity C by,
Thus, we get the values of C as follows:
Shaft Number Dynamic Load Capacity
(N)
1 9682
2 12500
3 5411
4 3700
Based on these values of C, we must selecta bearingfromthe
manufacturer’s catalogue whose dynamic load capacity is
more than our requirement. The table for selection is given
below.
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072
© 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 686
Fig -12: Bearing selection
The following table tells us which bearings are sufficient to
satisfy our requirement and are thus selected.
Shaft
Number
Bearing
Number
Principal
Dimensions(d,D,B) (all
mm)
1 6006 30,55,13
2 6006 30,55,13
3 6006 30,55,13
4 16006 30,55,9
Fig -13: Selected bearings
2.9 Casing Design:
Casing consideration: Followingstepshavebeentakeninto
consideration while designing the casing of the gearbox.
 Compact
 Weight optimisation
 Leak proof (bearing fitted in casing)
Visual Representation: The part of the casing which holds
the gearbox looks as follows.
Fig -14: Gearbox casing
2.10 Final Gearbox assembly:
Final Gearbox assembly: The final Gearbox assembly with
corrected values is as follows:
Fig -15: Schematic of final assembly
3. 3D Modelling and Analysis of gearbox.
Now that we had all the parameters required for designing
the gearbox on CAD tools, the CAD models for all the gears,
shafts, bearings, and the casing was created. The CAD was
modelled in Solid works software.
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
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© 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 687
3.1 CAD Models – Gears and shafts
Fig -16: Shaft 1 Gear 1
Fig -17: Shaft 1 Gear 2
Fig -18 Shaft 2 Gear 1
Fig -19: Shaft 2 Gear 2
Fig -20: Shaft 2 Gear 3
Fig -21: Shaft 2 Gear 4
Fig -22: Shaft 3 Gear 1
Fig -23: Shaft 3 Gear 2
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
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Fig -24: Shaft 3 Gear 3
Fig -25: Shaft 3 Gear 4
Fig -26: Shaft 4 Gear 1
Fig -27: Shaft 4 Gear 2
Fig -28: Shaft 1
Fig -29: Shaft 2
Fig -30: Shaft 3
Fig -31: Shaft 4
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
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3.2 Final 3D Model:
Fig -32: Final Gear box assembly
3.3 Gearbox and shaft analysis:
Analysis of Gearbox
The gear pairs have been analyzed on ANSYS 18.1 software.
Analysis of components can be done in various ways like
static, dynamic, transient, etc. depending up on application.
Static analysis is concerned with determination of response
of a gear to steady loads whoseresponseremainsunchanged
with time. The response of the gear is expressed in terms of
stress, strain, displacement. Thetool usedin staticanalysisis
Static structural.
Procedure: The finite element analysis procedure of the
spur gear was given below:
1. A three-dimensional model of the spur gear was
created using the pro/engineer CAD software.
2. The material properties were defined for gears.
3. The model was meshed using finite element
software.
4. Boundary conditions for ANSYS Workbench as
mentioned below.
5. Fixed displacement constraint was applied on gear.
6. Moment was applied on gear.
7. To arrest the displacement on x, y, z directions and
rotations on x, y directions remote displacement
constraint is applied on pinion surface.
Contacts – Frictionless contacts between the gear pairs and
the gear and shaft pairs.
Boundary Conditions – Torques have been applied to the
input gear surfaces.
Material – Cast Iron has been considered for all the gear
pairs.
Deformation Results:
Fig -33: Total deformation for meshing pair 1
Fig -34: Total deformation for meshing pair 2
Fig -35: Total deformation for meshing pair 3
Fig -36: Total deformation for meshing pair 4
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Fig -37: Total deformation for meshing pair 5
Equivalent Stress:
Fig -38: Equivalent stress for meshing pair 1
Fig -39: Equivalent stress for meshing pair 2
Fig -40: Equivalent stress for meshing pair 3
Fig -41: Equivalent stress for meshing pair 4
Fig -42: Equivalent stress for meshing pair 5
Factor of Safety:
Fig -43: Factor of safety analysis
The value obtained for the FOS for all the gear pairs is
mentioned below –
Gear Pair FOS Min FOS Max
1 1.3674 15
2 1.3896 15
3 1.2645 15
4 1.3564 15
5 1.2313 15
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Hence, we can conclude that the design is within the
permissible limits for the given material and geometry.
Analysis of shafts:
The tool used in static analysis is Static structural.
Procedure: The finite element analysis procedure of the
shafts was given below:
1. A three-dimensional model of the shafts was
created using the pro/engineer CAD software.
2. The material properties were defined for shaft.
3. The model was meshed using finite element
software.
4. Boundary conditions for ANSYS Workbench as
mentioned below.
5. Fixed displacement constraint was applied on gear.
Contacts – Fixed contacts have been provided at the ends of
the shafts.
Boundary Conditions – Forces were applied on theshaft as
Point loads and UDL.
Total Deformation:
Fig -44: Shaft 1
Fig -45: Shaft 2
Fig -46: Shaft 3
Fig -47: Shaft 4
4.0 Analysis Results summary:
4.1 Gear Analysis:
Pair Min Def ( m) Max Def (m)
1 7.622e-6 5.202e-5
2 8.303e-6 4.303e-5
3 3.794e-6 1.446e-5
4 1.353e-6 7.533e-5
5 9.050e-6 4.197e-5
Pair Min stress Max stress
1 4536 1.45e8
2 2144.7 1.30e8
3 2101.6 6.01e8
4 3077.5 1.91e8
5 2153.4 1.01e8
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072
© 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 692
4.2 Shaft Analysis
Shaft Min def (m) Max def (m)
1 0 5.51e-7
2 0 4.64e-7
3 0 4.59e-7
4 0 5.31e-7
Shaft Min stress (Pa) Max stress (Pa)
1 69.6 3.854e5
2 1590.6 2.763e5
3 189 3.017e5
4 666.45 2.814e5
Shaft Min strain Max strain
1 1.523e-9 1.938e-6
2 1.041e-9 1.394e-6
3 7.205e-9 1.571e-6
4 3.332e-9 1.414e-6
5. CONCLUSIONS
In conclusion, a standard design procedure for the designof
this 8-speed gearbox was followed considering various
research papers and textbooks. Normally, in lathe machine
applications, 6 speed gearboxes are used and using an 8-
speed gearbox will provide more operating speeds along
with offering more smoother and uniform machining
operation as the intervals between two successive speeds
will reduce. Post designing, thorough analysis considering
the working and static conditions of the gearbox was done
and all critical parameters were found to be well within the
permissible range.
REFERENCES
[1] N. Siva Teja and K. Dinesh Babu, “Design and analysis of
differential gear box in automobiles” IJMET, vol. 8, May
2017, pp. 175 – 185.
[2] PNV Sai Mahesh and MVV Sai Ram, “Design andAnalysis
of a 4-speed, dual input hybrid gear box” IJPAM, Volume
118, No. 24, 2018.
[3] Ye Mint and Zaw Maw Oo, “Analysis of Gear Box Design
in head stock for CNC lathe machine” IJSRP, Volume 9,
Issue 8, August 2019.
[4] D Mohammed Rafi and Mr. B Raja Kumar, “Design and
development of gearbox for multi-purpose milling
machine” AIJREAS, Volume 1, Issue 12, Dec 2016.
[5] Pawan Kumar and M. Y. Patil, “Design and Thermal
Analysis of helical gearbox” GRA, Volume2,Issue4April
2013.
[6] A.Y.V Gopi Krishna and R.V. Kiran, “Design and Analysis
of two stage reduction gearbox” IRJET, Volume 6, Issue
12, December 2019.
[7] Thite Sagar, “Modal and stress analysis of gear train in
portal axle system” IJERT, Volume 6, Issue 5, May 2017.
[8] Nihad Hassan Talib and Gopi Krishna, “Design and
finite element analysis of high-speed compressor
gearbox” IJIRCT , Volume 1, Issue 1, 2015.
[9] Reji Mathew and Linto P Anto, “Gearbox design for CNC
lathe” IRJET, Volume 5, Issue 4, April 2018.
[10] Joginder Singh amd M R Tyagi, “Analysis of stresses and
deflections in spur gear” IJMET, Volume 8, Issue 4, April
2017.
[11] Sushil Kumar Tiwari and Upendra Kumar Joshi, “Stress
Analysis of mating involute spur gear teeth” IJERT,
Volume 1, Issue 9, November 2012.

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Design and Analysis of an 8-Speed Gear box.

  • 1. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072 © 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 678 Design and Analysis of an 8-Speed Gear box. Abhishek Chavan1, Abhiraj Baji2, Yash Darakh3, Chinmay Inamdar4 145Department of Mechanical Engineering, Vishwakarma Institute of Technology, Pune-48, Maharashtra, India ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - Lathe Machine is used in all the engineering applications and in the college Workshops. Lathe machine is used to perform all the basic operations such as drilling, cutting, tapping, turning, etc. with the help of different tools placed in the work environment There are 2 main types of Lathe machines: Capstan Lathe and Turret Lathe. Turret Lathes use a turret head to perform operations. A turret head is a vertical cylindrical revolving tool-holder for bringing different tools into action successively in the lathe machine. The turret head needs to rotate at different speeds to perform different operations on the workpiece. This is controlled by a gearbox. A gearbox which converts high speed input into various output speeds is called a multi speed gearbox. A 6- speed gearbox is usually used. But 8-speed and 9-speed gearboxes give a wider range of speeds and efficiency. The aim of this project is to design and analyze 8-speed gearbox which meets the functional requirements of a turret gearbox. Design and Analysis have been conducted and a detailed study has been performed for various components in the gearbox. Key Words: Lathe, Gearbox, Turret, Gears, Shaft, Ray Diagram, etc. 1. INTRODUCTION Ever since the development of the first gearbox by Sturtevant in 1904 for automobileapplication,theutilisation of this technology has evolved marking its presence in various industrial sectors like power generation, petroleum refining, mining and material handling,metal processingand so on. Considering the metal processing and machining aspect, a wide range of industrial gearboxesareusedinlathe machines. These gearboxes offer a vivid range of operating speed, and the main aim of this project is to design an 8- Speed gearbox for using in turret lathe machines. 1.1 Deciding Input Requirements Speed Requirement: Aftera comprehensivestudyonspeed ranges (Nmin and Nmax) for turret lathe, we arrived at a generic average value of 100rpm to 1100rpm. These values are optimal for further processing and give a better design result as compared to other experimental values as well. Torque Requirement: Turret lathe gearboxes usually require a power of approximately 5-8kW [2]. Motor Selection: Motor selection has been done taking power and input speed conditions into account. An approximate 8.5HP(6.33kW) and 650rpm motor has been selected. The values will be explained further on in the project. 1.2 Deciding Material After trial and error with various materials in the design process and opinions of industry professionals,materialsfor the following components were decided mainly based on strength and durability. Gear: All the gear are made from ‘Grey Cast Iron’. Shaft: All the shafts have been made of the material ‘Steel FeE 580’. Keys and keyways: All the keys have been made out of ‘Steel 50C4.’ Casing: The casing has been made from ‘Cast Iron’. 2. DETAILED DESIGN PROCEDURE 2.1 Derivation of Structural Formula The structural formula gives information about various aspects of the gearbox like number of shafts, number of gears and a basic idea of transmission pairs. It tells about transmission range as well. The procedurefollowedtoreach the structural formula is explained below. Law of Discretizing Speeds: Discretizing speeds between minimum speed and maximum speed is very important to know our output speeds. These speeds are decided by three basic laws as depicted in the table below. Fig -1: Laws of discretizing speeds.
  • 2. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072 © 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 679 Justification of using Geometric Progression: The speeds in gear boxes can be arranged in arithmetic progression (A.P.), geometric progression (G.P.), harmonic progression (H.P), and logarithmicprogression(L.P.).However,when the speeds are arranged in G.P., it has the following advantages.  The speed loss is minimum i.e., Speed loss=Desired optimum speed – Available speed  The number of gears to be employed is minimum.  G.P. provides a more even rangeofspindlespeedsat each step.  The layout is comparatively very compact.  Productivity of a machining operation, i.e., surface area of the metal removed in unit time, is constant in the whole speed range.  G.P. machine tool spindle speeds can be selected easily from preferred numbers. Because preferred numbers are in geometric progression. Deciding Speed Ratio from Standard Series: In gearbox design a set of preferred step ratio or preferred numbers is used to obtain the series of output speed of gearbox. The preferred step ratio is mentioned as basic series named as R5, R10, R20, R40 and R80. Each basic series has a specific step ratio. In our case, we have Nmin as 100rpm and Nmax as 1100rpm. Thus, The Step Ratio 1.4 comes under R20 series. Thus, the spindle speeds calculated are: N1 = = 100rpm N2 = = 140rpm N3 = = 196rpm = 200rpm N4 = = 274.4rpm = 280rpm N5 = = 392rpm = 400rpm N6 = = 560rpm N7 = = 784rpm = 780rpm N8 = = 1097rpm = 1100rpm These are subject to change based on number of teeth chosen. Deriving Structural Formula: Let, n = Number of speeds available at the spindle. p1, p2, p3….. = stage numbers in gearbox. X1, X2, X3….. = Characteristics of the stages. Then, structural formula is given as: N = p1(X1).p2(X2).p3(X3).p4(X4) Were, X1 = 1; X2 = p1; X3 = p1 x p2; X4 = p1 x p2 x p3 Table -1: SR NO: Number of speeds Preferred Structural Formula 1 6 Speeds 3 (1) . 2 (3) 2 (1) . 3 (2) 2 8 Speeds 2 (1) . 2 (2) . 2 (4) 4 (1) . 2 (4) 3 9 Speeds 3 (1) . 3 (3) 4 12 Speeds 3 (1) . 2 (3) . 2 (6) 2 (1) . 3 (2) . 2 (6) 2 (1) . 2 (2) . 3 (4) For 8 – Speed Gearbox: 2 x 2 x 2 = 8 Therefore, P1 = 2, X1 = 1 P2 = 2, X2 = 2 P3 = 2, X3 = 2 x 2 = 4 Then, structural formula = 2 (1) . 2 (2) . 2 (4) Determining number of Shafts, Gears and Transmissions: Calculation of No. of shafts to draw kinematic arrangement: No. of shafts = No. of stages + 1. That is, If 3 stages are there in gearbox design, then no. of shaft will be = 3 + 1 = 4 shafts. As per gear kinematics, Shaft 1 = p1 gears = 2 gears. Shaft 2 = (p1 + p2) gears = 4 gears. Shaft 3 = (p2 + p3) gears = 4 gears. Shaft 4 = p1 gears = 2 gears. Limiting Value of (Ig)stage: 2.2 Structural Ray Diagram Drawing Structural Ray Diagram: The ray diagram is graphical representationofthedrivearrangementingeneral from. In other words, the ray diagram is a graphical representation of the structural formula, as shown in figure. It provides the following data on the drive:  The number of stages (a stage is a set of gear trains arranged on two consecutive shafts).
  • 3. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072 © 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 680  The number of speeds in each stage.  The order of kinematic arrangement of the stages.  The specific values of all the transmission ratios in the drive.  The total number of speeds available at the spindle. Procedure: The following is the procedure to plot structural ray diagram:  In this diagram, shafts are shown by vertical equidistant and parallel lines.  The speeds are plotted vertical on a logarithmic scale with log  as a unit.  Transmission engaged at definite speeds of the driving and driven shafts are shown on the diagram by rays connecting the points on the shaft lines representing these speeds.  Figure shows the ray diagram for a 9-speed gear box, having the structural formula, Z = 2 (1). 2 (2). 2(4). Fig -2: Structural Ray Diagram 2.3 Speed Ray Diagram: Significance: A speed ray diagram is a diagram depicting all possible exact values of speeds at which the multi speed gearbox can run. It gives us a clear picture of gear ratios as well. Plotting Speed Diagram: A basic procedure which is followed is as follows-  Draw u+1 vertical line atconvenientdistance where u= Number of stages (for above formula u=4 three transmission group) Note : first vertical line represents the transmission from motor shaft and the rest represent the transmission groupsofspeed box. 2).  Draw array of horizontal lines is equal to the number of speed steps z of speed intersecting the vertical lines distance of log Ø from each other. Fig -3: Speed Ray Diagram 2.4 Preliminary Gearbox assembly: Basic Assembly Diagram Optimisation: The following diagram shows the basic gearbox assembly where Gn is the number of the nth gear and Zn is number of teeth of Gn th gear. Fig -4: Preliminary Gearbox assembly 2.5 Determining Gear Ratios and Number of teeth: Approximating Gear Ratio from Speed Ratio and Constraints: As we have seen in the picture above,thereare 12 gears of which we need to find the numberofteeth.There
  • 4. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072 © 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 681 are a few constraints to take care of after which we can easily select number of teeth from the design data book. The summation of number of teeth of the meshing gears between two shafts should be exactly equal. m = constant for all thus, thus, similarly, and Therefore, by selecting standard number of teeth from design data book to satisfy the above given gear ration equation, we get the following number of teeth per gear: Table -2: Gear Number Number of Teeth 01 Z01 = 20 02 Z02 = 25 03 Z03 = 45 04 Z04 = 40 05 Z05 = 24 06 Z06 = 34 07 Z07 = 34 08 Z08 = 24 09 Z09 = 20 10 Z10 = 40 11 Z11 = 40 12 Z12 = 20 Corrected final speeds: Old Speed (rpm) New Speed (rpm) Difference (rpm) % Change 100 98 2 2% 140 137 3 2.1% 200 196 4 2% 280 276 4 1.4% 400 392 8 2% 560 551 9 1.6% 780 787 7 0.8% 1100 1106 6 0.5% 2.6 Determining final gear dimensions: Determination of module: Fig - 5: Determination of Module By our calculations, we got a module of 2.8. Rounding this off, we chose a module of 3mm. Module m = 3mm. Determination of Gear diameter: Gear Number Diameter of Gear (mm) 1 D1 = m*Z1 = 60 2 D2 = m*Z2 = 75 3 D3 = m*Z3 = 135 4 D4 = m*Z4 = 120 5 D5 = m*Z5 = 72
  • 5. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072 © 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 682 6 D6 = m*Z6 = 102 7 D7 = m*Z7 = 102 8 D8 = m*Z8 = 72 9 D9 = m*Z9 = 60 10 D10 = m*Z10 = 120 11 D11 = m*Z11 = 120 12 D12 = m*Z12 = 60 Determination of Gear dimensions: We have selected 20 full depth involute teeth system. As we input our module, system of teeth and number of teeth into Solid works, it gives us the remaining outputs. Fig - 6: Types of teeth system By considering 20-degree full depth system:  Addendum (ha) = m = 3mm  Dedendum (hf) = 1.25 m = 3.75mm  Clearance (c) = 0.25 m = 0.75mm  Working depth (hk) = 2 m = 6mm  Whole depth (h) = 2.25 m = 6.75mm  Tooth thickness (s) = 1.5708 m = 4.7mm  Tooth space = 1.5708 m = 4.7mm  Filet radius = 0.4 m = 1.2mm Weights of individual gears: Post obtaining the dimensions required for each gear, we design them on modelling software and then obtain the weights as follows: Sr. No. Gear with teeth Weight(N) 1 20 4.28 2 24 6.76 3 25 7.595 4 34 14.98 5 40 21.98 6 45 28.616 Design of shaft: Torque input to individual shafts: The selected motor provides an input power of 6.33kW to the initial shaft. The first shaft rotates at 625rpm. From the formula, We get Torsional moment of first shaft T1 = 96.71 N-m. Similarly, finding out all the possible torsional moments of all shafts, we consider the maximum one for calculation purposes. The results are tabulated as follows: The torques marked in red are the highest torques acting on the respective shafts. This be our torsional moments to be considered during design. Calculation and Direction of Gear Forces: There are 3 main types of forces acting when a gear pair meshes. They are as follows:  Tangential Force Ft: The force acting tangential to the gear surface at the point of contact with meshing gear.  Radial force Fr: The force actingtowardsthecentre of the gear at the point of contact with the meshing gear.  Axial Force Fa: The force that acts in thez-direction along the shaft due to the angle of the teeth is the axial force. As our teeth don’t have an angle with respect to the gear base, this force for our consideration, is 0. As our gearbox is a spur gear system, we will consider the tangential and radial forces of all gears for calculation purposes. For each gear
  • 6. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072 © 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 683 Gear Force Type Value (N) G1 Tangential force Ft 3223.6 Radial Force Fr 1173.3 G2 Tangential force Ft 2758.9 Radial Force Fr 938.65 G3 Tangential force Ft 322.2 Radial Force Fr 117.28 G4 Tangential force Ft 362.5 Radial Force Fr 131.93 G5 Tangential force Ft 426.47 Radial Force Fr 115.22 G6 Tangential force Ft 604.16 Radial Force Fr 219.89 G7 Tangential force Ft 427.78 Radial Force Fr 115.69 G8 Tangential force Ft 301.96 Radial Force Fr 109.90 G9 Tangential force Ft 513.33 Radial Force Fr 186.83 G10 Tangential force Ft 256.67 Radial Force Fr 93.41 G11 Tangential force Ft 513.33 Radial Force Fr 186.83 G12 Tangential force Ft 1026.6 Radial Force Fr 373.67 Modified Weight of Gear: From Solid works, we have the weight of the solid gear. As there will be a shaft of diameter ‘d’ through this, we must reduce that much weight. Therefore, giving a new modified weight to work with. Let, Wnew = Modified Weight in Newton Wold – Solid works output weight in Newton Wr - Weight of Inner part to be removed in Newton. d – diameter of shaft in m f – face width of gear in m ρ – density of gear in kg/m3 g – acceleration due to gravity in m/s2 Fig -1: Name of the figure Wnew = Wold – Wr Wr = Weight of cylindrical part of gear Wr = Calculating Maximum Bending Moment for each Shaft: Our aim right now is to calculate maximum bendingmoment acting on the shaft for the calculation of shaft diameter. This can be done in terms of ‘d’ as all values in our SFD are in terms of ‘d’. The maximum bending moment isarea betweentheSFDand the shaft axis above the shaft axis and the point of maximum bending is the point where the SFD graph crosses the shaft axis. Thus, calculating the areas, we get the followingresults. Shaft Maximum Bending Moment (Mb) Maximum Torsional Moment (Mt) 1 252261.7 346544.50 2 282504.30 264387.4 3 294134.50 357548.00 4 263150.23 346753.82 Determining Shaft Diameter: We will be designing the shaft using ASME code of shaft design. According to this code, the permissible shear stress τmax for the shaft without keyways is taken as 30% of yield strength in tension or 18% of the ultimate tensile strength of the material, whichever is minimum. Therefore, τmax = 0.30 Syt or τmax = 0.18 Sut (whichever is minimum). If keyways are present, the above values are to be reduced by 25 per cent. According to the ASME code, the bendingand torsional moments are to be multiplied by factors kb and kt respectively, to account for shock and fatigue in operating condition. The ASME code is basedonmaximumshearstress theory of failure. were, d
  • 7. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072 © 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 684 kb = combined shock and fatigue factor applied to bending moment kt = combined shock and fatigue factor applied to torsional moment Mb = Maximum Bending moment acting on shaft Mt = Maximum torsional moment acting on shaft Fig -7: Shock and fatigue factors For the gearbox, it is a minor shock application. Thus, the load is applied suddenly. We have taken as intermediate value of kb = 1.5-2.0 and kt = 1.0-1.5. Our shaft material is ‘Steel FeE 580 (Sut = 770 and Syt = 580 N/mm2). Calculating permissible shear stress, 0.30 Syt = 0.30(580) = 174 N/mm2 0.18 Sut = 0.18(770) = 138.6 N/mm2 The lower of the two values is 138.6 N/mm2 and there are keyways on the shaft. τmax = 0.75(138.6) = 103.95 N/mm2 Combining values of τmax from both above equations, Using max bendingmoment andtorsional momentvalues for each shaft, we get the following shaft diameters which are taken in accordance with the standard shaft table. Fig -8: Shaft diameters Shaft Number Shaft diameter (mm) 1 28 2 30 3 30 4 28 2.7 Design of keys and keyways: Type of key: There are various types of keys. We have selected Rectangular Saddle Key. Its design has been conducted as follows. Design on load basis: The material for key is Steel 50C4(Syt = 460 N/mm2) and the factor of safety is taken as 3. For key material, the yield strength in compression can be assumed to be equal to the yield strength in tension. Keyways are on the second and fourth shaft. Syc = Syt = 460 N/mm2 N/mm2 According to maximum shear stress theory of failure, Ssy = 0.5*Syt = 0.5(460) = 230 N/mm2 b – breadth of key h – height of key l – length of key d – diameter of shaft Industry standard is to select a basic dimension of b = h = d/4 = 30/4 = 7.5 = 7mm or Taking maximum value using both equations, we get key length = 28.7mm Now selecting from standard table,
  • 8. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072 © 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 685 Fig -9: Determination of keys and keyways Thus, we select the key with dimension (b,h) as (8,7) and a length of 30mm. Fig -10: Shafts 2.8 Selection of bearings: Defining Bearing Life: To select bearings, it is necessary to specify life of the bearings. This can be done from standard bearing selection table. The recommended bearing life for gear applications is given in the table below: Fig -11: Bearing life. The values given in the above table are only for general guidance. For a particular application, the designer should consider the experience, the difficulties faced by the customer in replacing the bearing and the economics of breakdown costs. As we are relatively new to the designing aspect, we have taken an estimated 15,000 hr( due to it being an intermediate value for a service machine. Selection from Manufacturer’s Catalogue: To select the final bearings, we will need radial force acting. As thereis no axial force, total force P = Fr. Diameter of all 4 shafts are taken into consideration. Then using max speed of all shafts, we calculate the rated bearing life L10 by the formula, After we get this value for all shafts, we calculate the dynamic load capacity C by, Thus, we get the values of C as follows: Shaft Number Dynamic Load Capacity (N) 1 9682 2 12500 3 5411 4 3700 Based on these values of C, we must selecta bearingfromthe manufacturer’s catalogue whose dynamic load capacity is more than our requirement. The table for selection is given below.
  • 9. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072 © 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 686 Fig -12: Bearing selection The following table tells us which bearings are sufficient to satisfy our requirement and are thus selected. Shaft Number Bearing Number Principal Dimensions(d,D,B) (all mm) 1 6006 30,55,13 2 6006 30,55,13 3 6006 30,55,13 4 16006 30,55,9 Fig -13: Selected bearings 2.9 Casing Design: Casing consideration: Followingstepshavebeentakeninto consideration while designing the casing of the gearbox.  Compact  Weight optimisation  Leak proof (bearing fitted in casing) Visual Representation: The part of the casing which holds the gearbox looks as follows. Fig -14: Gearbox casing 2.10 Final Gearbox assembly: Final Gearbox assembly: The final Gearbox assembly with corrected values is as follows: Fig -15: Schematic of final assembly 3. 3D Modelling and Analysis of gearbox. Now that we had all the parameters required for designing the gearbox on CAD tools, the CAD models for all the gears, shafts, bearings, and the casing was created. The CAD was modelled in Solid works software.
  • 10. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072 © 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 687 3.1 CAD Models – Gears and shafts Fig -16: Shaft 1 Gear 1 Fig -17: Shaft 1 Gear 2 Fig -18 Shaft 2 Gear 1 Fig -19: Shaft 2 Gear 2 Fig -20: Shaft 2 Gear 3 Fig -21: Shaft 2 Gear 4 Fig -22: Shaft 3 Gear 1 Fig -23: Shaft 3 Gear 2
  • 11. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072 © 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 688 Fig -24: Shaft 3 Gear 3 Fig -25: Shaft 3 Gear 4 Fig -26: Shaft 4 Gear 1 Fig -27: Shaft 4 Gear 2 Fig -28: Shaft 1 Fig -29: Shaft 2 Fig -30: Shaft 3 Fig -31: Shaft 4
  • 12. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072 © 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 689 3.2 Final 3D Model: Fig -32: Final Gear box assembly 3.3 Gearbox and shaft analysis: Analysis of Gearbox The gear pairs have been analyzed on ANSYS 18.1 software. Analysis of components can be done in various ways like static, dynamic, transient, etc. depending up on application. Static analysis is concerned with determination of response of a gear to steady loads whoseresponseremainsunchanged with time. The response of the gear is expressed in terms of stress, strain, displacement. Thetool usedin staticanalysisis Static structural. Procedure: The finite element analysis procedure of the spur gear was given below: 1. A three-dimensional model of the spur gear was created using the pro/engineer CAD software. 2. The material properties were defined for gears. 3. The model was meshed using finite element software. 4. Boundary conditions for ANSYS Workbench as mentioned below. 5. Fixed displacement constraint was applied on gear. 6. Moment was applied on gear. 7. To arrest the displacement on x, y, z directions and rotations on x, y directions remote displacement constraint is applied on pinion surface. Contacts – Frictionless contacts between the gear pairs and the gear and shaft pairs. Boundary Conditions – Torques have been applied to the input gear surfaces. Material – Cast Iron has been considered for all the gear pairs. Deformation Results: Fig -33: Total deformation for meshing pair 1 Fig -34: Total deformation for meshing pair 2 Fig -35: Total deformation for meshing pair 3 Fig -36: Total deformation for meshing pair 4
  • 13. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072 © 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 690 Fig -37: Total deformation for meshing pair 5 Equivalent Stress: Fig -38: Equivalent stress for meshing pair 1 Fig -39: Equivalent stress for meshing pair 2 Fig -40: Equivalent stress for meshing pair 3 Fig -41: Equivalent stress for meshing pair 4 Fig -42: Equivalent stress for meshing pair 5 Factor of Safety: Fig -43: Factor of safety analysis The value obtained for the FOS for all the gear pairs is mentioned below – Gear Pair FOS Min FOS Max 1 1.3674 15 2 1.3896 15 3 1.2645 15 4 1.3564 15 5 1.2313 15
  • 14. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072 © 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 691 Hence, we can conclude that the design is within the permissible limits for the given material and geometry. Analysis of shafts: The tool used in static analysis is Static structural. Procedure: The finite element analysis procedure of the shafts was given below: 1. A three-dimensional model of the shafts was created using the pro/engineer CAD software. 2. The material properties were defined for shaft. 3. The model was meshed using finite element software. 4. Boundary conditions for ANSYS Workbench as mentioned below. 5. Fixed displacement constraint was applied on gear. Contacts – Fixed contacts have been provided at the ends of the shafts. Boundary Conditions – Forces were applied on theshaft as Point loads and UDL. Total Deformation: Fig -44: Shaft 1 Fig -45: Shaft 2 Fig -46: Shaft 3 Fig -47: Shaft 4 4.0 Analysis Results summary: 4.1 Gear Analysis: Pair Min Def ( m) Max Def (m) 1 7.622e-6 5.202e-5 2 8.303e-6 4.303e-5 3 3.794e-6 1.446e-5 4 1.353e-6 7.533e-5 5 9.050e-6 4.197e-5 Pair Min stress Max stress 1 4536 1.45e8 2 2144.7 1.30e8 3 2101.6 6.01e8 4 3077.5 1.91e8 5 2153.4 1.01e8
  • 15. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 10 Issue: 04 | Apr 2023 www.irjet.net p-ISSN: 2395-0072 © 2023, IRJET | Impact Factor value: 8.226 | ISO 9001:2008 Certified Journal | Page 692 4.2 Shaft Analysis Shaft Min def (m) Max def (m) 1 0 5.51e-7 2 0 4.64e-7 3 0 4.59e-7 4 0 5.31e-7 Shaft Min stress (Pa) Max stress (Pa) 1 69.6 3.854e5 2 1590.6 2.763e5 3 189 3.017e5 4 666.45 2.814e5 Shaft Min strain Max strain 1 1.523e-9 1.938e-6 2 1.041e-9 1.394e-6 3 7.205e-9 1.571e-6 4 3.332e-9 1.414e-6 5. CONCLUSIONS In conclusion, a standard design procedure for the designof this 8-speed gearbox was followed considering various research papers and textbooks. Normally, in lathe machine applications, 6 speed gearboxes are used and using an 8- speed gearbox will provide more operating speeds along with offering more smoother and uniform machining operation as the intervals between two successive speeds will reduce. Post designing, thorough analysis considering the working and static conditions of the gearbox was done and all critical parameters were found to be well within the permissible range. REFERENCES [1] N. Siva Teja and K. Dinesh Babu, “Design and analysis of differential gear box in automobiles” IJMET, vol. 8, May 2017, pp. 175 – 185. [2] PNV Sai Mahesh and MVV Sai Ram, “Design andAnalysis of a 4-speed, dual input hybrid gear box” IJPAM, Volume 118, No. 24, 2018. [3] Ye Mint and Zaw Maw Oo, “Analysis of Gear Box Design in head stock for CNC lathe machine” IJSRP, Volume 9, Issue 8, August 2019. [4] D Mohammed Rafi and Mr. B Raja Kumar, “Design and development of gearbox for multi-purpose milling machine” AIJREAS, Volume 1, Issue 12, Dec 2016. [5] Pawan Kumar and M. Y. Patil, “Design and Thermal Analysis of helical gearbox” GRA, Volume2,Issue4April 2013. [6] A.Y.V Gopi Krishna and R.V. Kiran, “Design and Analysis of two stage reduction gearbox” IRJET, Volume 6, Issue 12, December 2019. [7] Thite Sagar, “Modal and stress analysis of gear train in portal axle system” IJERT, Volume 6, Issue 5, May 2017. [8] Nihad Hassan Talib and Gopi Krishna, “Design and finite element analysis of high-speed compressor gearbox” IJIRCT , Volume 1, Issue 1, 2015. [9] Reji Mathew and Linto P Anto, “Gearbox design for CNC lathe” IRJET, Volume 5, Issue 4, April 2018. [10] Joginder Singh amd M R Tyagi, “Analysis of stresses and deflections in spur gear” IJMET, Volume 8, Issue 4, April 2017. [11] Sushil Kumar Tiwari and Upendra Kumar Joshi, “Stress Analysis of mating involute spur gear teeth” IJERT, Volume 1, Issue 9, November 2012.