The document describes a project report for the design and fabrication of a two speed variable transmission gearbox. It was submitted by two students, G. Aravind and S. Arun Muzhithevan, in partial fulfillment of their Bachelor of Engineering degree in Mechanical Engineering at St. Joseph's College of Engineering. The report provides an acknowledgment of those who assisted and supervised the project, a table of contents, descriptions of gearboxes and gear types such as spur gears, and explanations of concepts such as pitch circles and lines of action.

1. DESIGN & FABRICATION OF TWO SPEED VARIABLE
TRANSMISSION GEARBOX
A PROJECT REPORT
Submitted by
G.ARAVIND (312313114021)
S.ARUN MOZHI THEVAN (3123131140)
In partial fulfilment for the award of the degree
Of
BACHELOR OF ENGINEERING
IN
MECHANICAL ENGINEERING
St. JOSEPH'S COLLEGE OF ENGINEERING
CHENNAI 600 119
1

2. ANNA UNIVERSITY: CHENNAI 600 025
APRIL 2016
BONAFIDE CERTIFICATE
DEPARTMENT OF MECHANICAL ENGINEERING
Certified that this project report “DESIGN AND FABRICATION OF TWO SPEED
VARIABLE TRANSMISSION GEARBOX” is the bonafide work of “G.ARAVIND
(312313114021) & S.ARUN MOZHI THEVAN (3123131140)” who carried out
the project work under my supervision.
SIGNATURE SIGNATURE
Dr S.ARIVAZHAGAN M.E. Ph.D., Mr.M.MUNINATHA KOTA M.E
HEAD OF DEPARTMENT ASSISTANT PROFESSOR
Department of Mechanical Engineering, Department of Mechanical Engineering,
St. Joseph’s College of Engineering., St. Joseph’s College of Engineering,
Jeppiaar Nagar, Jeppiaar Nagar,
Chennai-600119 Chennai-600119.
Submitted for project viva-Voice held on ________________
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3. CERTIFICATE OF EVALUATION
COLLEGE NAME: ST JOSEPH’S COLLEGE OF ENGINEERING
BRANCH: MECHANICAL ENGINEERING
SEMESTER: VI
S. No. Name of the Students who have
done the project Title of the Project
Name of the
Supervisor with
designation
1
2
G.ARAVIND
S.ARUNMOZHITHEVAN
DESIGN AND
FABRICATION
OF TWO SPEED
VARIABLE
TRANSMISSION
GEARBOX
MR.M.MUNINATHA
KOTA M.E
ASSISTANT
PROFESSOR
Department of Mechanical
Engineering.
This report of project work submitted by the above students in partial
fulfilment for the award of Bachelor of Mechanical Engineering Degree in Anna
University were evaluated and conformed to be reports of the work done by the
above students and then evaluated.
Submitted for UNIVERSITY VIVA EXAMINATION held on …………………
INTERNAL EXAMINER EXTERNAL EXAMINER
3

4. ACKNOWLEDGEMENTS
We would like to express our sincere thanks and gratitude to our college
Chairman Col Dr THIRU JEPPIAAR M.A., B.L., Ph.D., Managing Director Dr
BABU MANOHARAN M.A, BL, Ph.D. Director Mr JAIKUMAR
CHRISTHURAJAN B.E, M.B.A.
Principal Dr VADDI SESHAGIRI RAO M.E., Ph.D., F.I.E. for giving us this
opportunity to carry out this project.
We extend our thanks to the Head of the Department of Mechanical
Engineering, Dr S.ARIVAZHAGAN M.E., Ph.D., for his valuable support and
cooperation.
We also thank MR.M.MUNINATHAN KOTA M.E, Lecturer-Department
of Mechanical Engineering for his guidance and timely suggestions which helped us
to complete this project.
Finally, Mr BALAMURUGAN M.E,Ph.d of Mechanical Engineering for
his constant support and guidance throughout the process of the project.
4

5. TABLE OF CONTENTS
TITLE PAGE NO
Abstract 7
1 Introduction 8
2 Literature review 9
3 Description of equipment 11
3.1 Gearbox 11
3.2 Spur gears 11
3.3 Shafts 15
3.4 D.C motor 17
4 Design and drawing 18
4.1 Calculation for gears 19
4.2 Drawing of sliding mesh gearbox 20
4.3 3D Modeling 21
5 Working principle 22
6 Merits & demerits 23
7 Applications 24
8 Material Considerations 24
9 Conclusion 27
10 Bibliography 28
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6. LIST OF FIGURES
1. Figure 1 11
2. Figure 2 16
3. Figure 3 20
4. Figure 4 22
5. figure 5 17
LIST OF TABLES
1 Table 1 25
6

7. ABSTRACT
Conventional gearboxes are capable of varying a given input speed. It is
achieved by meshing of gears in various gear ratios. The torque values are different
during different gear ratios. Hybrid gearboxes are capable of transmitting various
torque levels at the same gear ratio. They have a high torque producing capacity
compared to a conventional gearbox. These gearboxes have provisions for several
inputs and several outputs, unlike one input and one output of a conventional
gearbox. It allows the choice of varied speeds to the inputs.
These gearboxes can be used in a lot of practical applications. As they have
very high loading capacities, they can be used in off-road, commercial vehicles,
military vehicles and other specialty vehicles. They can also be used in cranes,
pumps, tractors, lawn mowers etc. Its most important application is that it can be
used in a hybrid car.
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8. CHAPTER I
INTRODUCTION
The main objective of our project is to create a gearbox with several inputs and
a single output. For this purpose, we have selected two input shafts and one output
shaft. It is a two speed sliding mesh gear box, controlled by a dog clutch for the
required sliding mechanism. It is simple, effective and a cost efficient design.
It is a hand feed gearbox. Adequate provisions have been given to adapt a
motor or an engine to it. It is designed with utter care to withstand high loading and
has a high factor of safety. The gearbox was fabricated with high accuracy milling
machines and tools with good engineering practices.
CHAPTER II
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9. LITERATURE REVIEW
TRANSMISSION
An assembly of parts including the speed-changing gears and the propeller
shaft by which the power is transmitted from an engine to a live axle. Often
transmission refers simply to the gearbox that uses gears and gear trains to
provide speed and torque conversions from a rotating power source to another
device.
The most common use is in motor vehicles, where the transmission adapts the
output of the internal combustion engine to the drive wheels. Such engines need to
operate at a relatively high rotational speed, which is inappropriate for starting,
stopping, and slower travel. The transmission reduces the higher engine speed to the
slower wheel speed, increasing torque in the process. Transmissions are also used on
pedal bicycles, fixed machines, and where different rotational speeds and torques are
adapted.
Often, a transmission has 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.
In motor vehicles, the transmission generally is connected to the
engine crankshaft via a flywheel and/or clutch and/or fluid coupling, partly because
internal combustion engines cannot run below a particular speed. The output of the
transmission is transmitted via driveshaft to one or more differentials, which in turn,
drive the wheels. While a differential may also provide gear reduction, its primary
purpose is to permit the wheels at either end of an axle to rotate at different speeds
9

10. (essential to avoid wheel slippage on turns) as it changes the direction of rotation.
Early transmissions included the right-angle drives and other gearing in
windmills, horse-powered devices, and steam engines, in support of pumping,
milling, and hoisting.
Most modern gearboxes are used to increase torque while reducing the speed
of a prime mover output shaft (e.g. a motor crankshaft). This means that the output
shaft of a gearbox rotates at a slower rate than the input shaft, and this reduction in
speed produces a mechanical advantage, increasing torque. A gearbox can be set up
to do the opposite and provide an increase in shaft speed with a reduction of torque.
Some of the simplest gearboxes merely change the physical rotational direction of
power transmission.
Many typical automobile transmissions include the ability to select one of
several different gear ratios. In this case, most of the gear ratios (often simply called
"gears") are used to slow down the output speed of the engine and increase torque.
However, the highest gears may be "overdrive" types that increase the output speed.
USES:
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.
Assembly of parts including the speed changing gears and the propeller shaft
by which the power is transmitted from an engine to a live axle. Often
10

11. transmission refers simply to the gearbox that uses gears and gear trains to
provide speed and torque conversions from a rotating power source to another
device.
CHAPTER III
DESCRIPTION OF EQUIPMENTS
3.1 GEARBOX
(Figure 1)
3.2 SPUR GEARS
Spur gears or straight-cut gears are the simplest type of gear. They consist of a
cylinder or disk with the teeth projecting radially, and although they are not straight-
sided in form (they are usually of special form to achieve constant drive ratio,
mainly involute), the edge of each tooth is straight and aligned parallel to the axis of
rotation. These gears can be meshed together correctly only if they are fitted to
parallel shafts.
11

12. Number of teeth, N
How many teeth a gear has, an integer. In the case of worms, it is the number
of thread starts that the worm has.
Gear, wheel
The larger of two interacting gears or a gear on its own.
Pinion
The smaller of two interacting gears.
Path of contact
Path followed by the point of contact between two meshing gear teeth.
Line of action, pressure line
Line along which the force between two meshing gear teeth is directed. It has
the same direction as the force vector. In general, the line of action changes
from moment to moment during the period of engagement of a pair of teeth.
For involute gears, however, the tooth-to-tooth force is always directed along
the same line—that is, the line of action is constant. This implies that for
involute gears the path of contact is also a straight line, coincident with the line
of action—as is indeed the case.
Axis
Axis of revolution of the gear; center line of the shaft.
Pitch point
Point where the line of action crosses a line joining the two gear axes.
Pitch circle, pitch line
Circle centered on and perpendicular to the axis, and passing through the pitch
point. A predefined diametric position on the gear where the circular tooth
thickness, pressure angle and helix angles are defined.
Pitch diameter, d
12

13. A predefined diametric position on the gear where the circular tooth thickness,
pressure angle and helix angles are defined. The standard pitch diameter is a
basic dimension and cannot be measured, but is a location where other
measurements are made. Its value is based on the number of teeth, the normal
module (or normal diametric pitch), and the helix angle. It is calculated as:
in metric units or in imperial units.
Module or modulus, m
Since it is impractical to calculate circular pitch with irrational numbers,
mechanical engineers usually use a scaling factor that replaces it with a regular
value instead. This is known as the module or modulus of the wheel and is
simply defined as
where m is the module and p the circular pitch. The units of module are
customarily millimeters; an English Module is sometimes used with the units
of inches. When the diametric pitch, DP, is in English units,
in conventional metric units.
The distance between the two axis becomes
where a is the axis distance, z1 and z2 are the number of cogs (teeth) for each of
the two wheels (gears). These numbers (or at least one of them) is often chosen
among primes to create an even contact between every cog of both wheels, and
thereby avoid unnecessary wear and damage. An even uniform gear wear is
achieved by ensuring the tooth counts of the two gears meshing together
are relatively prime to each other; this occurs when the greatest common
divisor (GCD) of each gear tooth count equals 1, e.g. GCD(16,25)=1; If a 1:1
gear ratio is desired a relatively prime gear may be inserted in between the two
gears; this maintains the 1:1 ratio but reverses the gear direction; a second
13

14. relatively prime gear could also be inserted to restore the original rotational
direction while maintaining uniform wear with all 4 gears in this case.
Mechanic engineers at least in continental Europe use the module instead of
circular pitch. The module, just like the circular pitch, can be used for all types
of cogs, not just evolving based straight cogs.
Operating pitch diameters
Diameters determined from the number of teeth and the center distance at
which gears operation.
Pitch surface
In cylindrical gears, cylinder formed by projecting a pitch circle in the axial
direction. More generally, the surface formed by the sum of all the pitch
circles as one moves along the axis. For bevel gears it is a cone.
Angle of action
Angle with vertex at the gear center, one leg on the point where mating teeth
first make contact, the other leg on the point where they disengage.
Addendum
Radial distance from the pitch surface to the outermost point of the
tooth.
Dedendum
Radial distance from the depth of the tooth trough to the pitch
surface.
Whole depth
14

15. The distance from the top of the tooth to the root; it is equal to addendum plus
dedendum or to working depth plus clearance.
Diametric pitch
D
Ratio of the number of teeth to the pitch diameter. Could be measured in teeth
per inch or teeth per centimeter, but conventionally has units of per inch of
diameter. Where the module, m, is in metric units
In English units.
3.3 SHAFTS
Shafts are rotating members that transmit power through them. They are
splined or slotted for a properly transmitting power and also acts as a coupling
medium.
(Figure 2)
15

16. Shaft
Spur gear
SHAFT LOCK RING
3.4 D.C MOTOR SPECIFICATIONS
16

17. • 300 RPM at 12V D.C motor with Metal Gearbox
• 18000 RPM base motor
• 6mm shaft diameter
• Gearbox diameter: 37 mm.
• Motor Diameter: 28.5 mm
• Length 63 mm without shaft
• Shaft length 15mm
• 300gm weight
• 10kgcm torque
• No-load current = 800 mA(Max), Load current = upto 9.5
A(Max)
CHAPTER IV
DESIGN AND DRAWING
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18. 4.1 DESIGN CALCULATIONS
Using Buckingham’s and Lewis Equations:
1) Selection of Material:
Gears, pinion and shafts are made of mild steel.
2) Calculation of Transmissibility Ratio:
I = (Z2/Z1) = (30/20) = 1.5
3) Calculation of tangential load:
Ft = (K0*103
*W) / Vm
K0 = 1.5 (for median life)
= (1.5*750)/Vm
Vm = (Пd1N1)/60 = (ПmZ1N1)/ (60*1000)
= (П*m*20*300)/ (60*1000)
Vm = 0.314m
Which implies,
Ft = (1.5*750)/Vm
= (3582.8)/m
4) Calculation of initial dynamic load:
Fd = Ft * Cv
Cv = (6 + Vm)/ 6 = 3 (Assume Vm = 12)
Fd = (3*3582.8)/m = 10748.4/m
5) Calculation of Beam Strength:
b= 10m
FB= [σb] by*Pa = 720*10*m*y*П*m
Y=0.1084
FB = 2450.70 m2
6) Calculation of module:
2450.70m2
= (10748.4)/m
18

19. m= 1.6 2mm (standard)ᴝ
7) Revaluation of Beam strength:
FB = 98028 N
Ft = 1791.4 N
8) Calculation of Dynamic load:
Vm = 0.628mm
d1 = mZ1
= 2*20= 40mm
Fd = 1796.17 N
Fs > Fd (Hence design is safe)
Fw = d1*Q*Kb
= 20*1.2*1.1*20
= 528 N
Q = 2(1.5)/ (1.5+1) = 1.2
19

20. (Figure 3)
Drawing of sliding mesh gearbox
20

21. 3-D MODELLING
21

22. IMAGES ATTACHED
(figure4)
CHAPTER V
WORKING PRINCIPLE
The spur gears in the gearbox having same pitch mesh against each other. The speed
and torque produced depend upon the gear ratios. The input power of the gearbox is
usually constant, thus the output power too is constant.
The gear ratios are changed by changing the gears using a gear shifting mechanism
by the use of a dog clutch. The dog clutch is connected to a handle or knob for the
gear selection.
CHAPTER VI
22

23. MERITS & DEMERITS
MERITS
 Quicker operation.
 Easy transmission.
 Low cost machine.
 It is used for carrying out multiple operations in a single machine.
 Both Forward and reverse speeds can be obtained
DEMERITS
 Suitable only for small purpose applications.
 Heavy weight(around kgs)
23

24. CHAPTER VII
APPLICATIONS
 Used in automobile workshops for drilling carburetor holes .
 Used in small scale industries that work on a tight budget.
 In robots for locomotion
 For performing the operations in huge parts which cannot be done in ordinary
machines.
 In such places where frequent changes in operation are required.
CHAPTER VIII
MATERIAL CONSIDERATIONS
FACTORS DETERMINING THE CHOICE OF MATERIALS
The various factors which determine the choice of material are discussed
below.
1. Properties:
The material selected must posses the necessary properties for the proposed
application. The various requirements to be satisfied
Can be weight, surface finish, rigidity, ability to withstand environmental attack
from chemicals, service life, reliability etc.
The following four types of principle properties of materials decisively affect
24

25. their selection
a. Physical
b. Mechanical
c. From manufacturing point of view
d. Chemical
The various physical properties concerned are melting point, thermal
Conductivity, specific heat, coefficient of thermal expansion, specific gravity,
electrical conductivity, magnetic purposes etc.
The various Mechanical properties Concerned are strength in tensile,
Compressive shear, bending, torsional and buckling load, fatigue resistance, impact
resistance, eleastic limit, endurance limit, and modulus of elasticity, hardness, wear
resistance and sliding properties.
The various properties concerned from the manufacturing point of view are,
 Cast ability
 Weld ability
 Surface properties
 Shrinkage
 Deep drawing etc.
2. MANUFACTURING COST:
Sometimes the demand for lowest possible manufacturing cost or surface qualities
obtainable by the application of suitable coating substances may demand the use of
special materials.
3. QUALITY REQUIRED:
This generally affects the manufacturing process and ultimately the material.
For example, it would never be desirable to go casting of a less number of
components which can be fabricated much more economically by welding or hand
25

26. forging the steel.
4. AVAILABILITY OF MATERIAL:
Some materials may be scarce or in short supply; it then becomes obligatory
for the designer to use some other material which may not be a perfect substitute for
the material designed. The delivery of materials and the delivery date of product
should also be kept in mind.
5. SPACE CONSIDERATION:
Sometimes high strength materials have to be selected because the forces involved
are high. In such cases it is of extreme importance to ensure that the space
optimization is not compromised on in the venture to impart high strength and
rigidity.
6. COST:
Factors like scrap utilization, appearance, and non-maintenance of the
designed part are involved in the selection of proper materials.
(Table 1)
CHAPTER IX
S.No DESCIRPTION QTY Material
1 Spur Gears 4 Mild Steel
2 Shafts 3 Mild Steel
3 D.C Motor 1
4 Dog Clutch 1 C.I
5 Gear Box 200mm*200mm Mild Steel
6 Shaft lock rings 6 Mild Steel
26

27. CONCLUSION
This project is made with pre planning, that it provides flexibility in operation.
Smoother and easy handling operation by the principle of “Gear Mechanics”
The comparative gain that can be accomplished is the utilization of roller bar.
This innovation has made the more desirable
This project “Design and fabrication of Hybrid Gearbox” is designed with the
hope that it is very much economical and help full to many industries and workshops
This project helped us to know the periodic steps in completing a project work.
Thus we have completed the project successfully.
BIBLIOGRAPHY
27

28. 1. Design data book -P.S.G.Tech.
2. Automobile Engineering - Dr. Kirpal Sen
3. Machine tool design handbook –Central machine tool Institute,
Bangalore.
4. Strength of Materials -R.S.Kurmi
5. Manufaturing Technology -M.Haslehurst.
6.Design of machine elements- R.s.kurmi
28

29. 29

30. 30