MATTU UNIVERSITY

COLLEGE OF ENGINEERING AND TECHNOLOGY

DEPARTMENT OF MECHANICAL ENGINEERING

COURSE TITLE: MACHINE DESIGN PROJECT - Ⅱ

PROJECT TITLE : GEARBOX DESIGN

NAME ID. NUMBER

ANWAR MOHAMMED RU 5293/12
OBSA GADISA RU 4905/12
AMANUEL GEAHEGN RU 4847/12

PRESENTED TO:
PRESENTATION DATE:
Mr. JEMA JAN - 4 - 2024
CONTENTS

 INTRODUCTION
 TYPES OF GEARBOX
 COMPONENTS OF GEARBOX
 FUNCTION OF GEARBOX
 OBJECTIVES
 METHODOLOGY
 LITERATURE REVIEW
 DETAIL DESIGN ANALYSIS
 DESIGN OF GEAR, SHAFT, KEY, BEARING AND HOUSING
 LUBRICATION SELECTION
 CONCLUSION AND RECOMMENDATION
 REFERENCE
 INTRODUCTION

 Gears are the part of machinery that changes the machine’s motion accordingly, and the process of changing gears is called
gearing.

 A gearbox is a complex structure of circulating machines that can control the speed and torque of a motor. In simple words,
it is a system of gears in a vehicle. It is also known as transmission due to its transmitting capacity.

 Gearbox often referred as transmission is a unit that uses gears and gear train to provide speed and torque conversions from
a rotating power source to another device.

 Gears are used to transmit torque and angular velocity in a wide variety of applications. The spur gear is designed to operate
on parallel shafts and having teeth parallel to the shaft axis.

 The first transmission system was given by French Inventors Louis-Rene and Emile Levassor who invented the world
largest ever transmission system with 3-speed sliding mesh transmission in 1894.
 A gearbox is a transmission device used between the engine's output shaft and the final drive to transfer the torque and
power required for the vehicle's wheels, the gearbox consists of a set of gears (i.e. spur, helical, bevel, worm depending on
the types of gearboxes used.

 It serves different purpose in the transmission system of an automobile; It exchanges engine power for greater torque and
thus provides a mechanical advantage to drive the vehicle under different conditions. also, It exchanges forward motion for
reverse motion.

 The relative speed of the two meshing gears is called Gear ratio. which obtained by dividing the number of teeth on the
driven gear to the number of teeth of the driving gear.

 A small gear driving a larger gear increases torque and decreases speed. When large gear driving a smaller gear decreases
torque and increases speed.

 A gearbox can be used in many different applications such as, industrial, power generation and construction.
 TYPES OF GEARBOX

 There are two main types of Gearbox in an Automobile; those are : Manual Transmission and Automatic Transmission.

 Manual Transmission: In a manual transmission type of gear system, the driver gets total control and chooses all gear
manually operating both a movable gear selector and a driver-operated clutch.

 This manual transmission allows the driver to either drop a gear to make the faster process or choose an increased gear to
conserve fuel.

 Here are 4 major types of Manual transmission; those are:

 Sliding Gear transmission: It consists of three shafts: clutch shaft, lay shaft, and main shaft, & arranged in a specific order.

 Synchromesh Gearbox: it uses a synchronizer ring and hub to engage output gears with the output shaft.

 Constant Mesh transmission: all the gears of the main shaft get in constant mesh with the connected gears of the lay shaft
.

 Pre-selector transmission: It is used as a planetary gear system to preselect gear ratios by operating a small lever on the
steering section.

 Automatic Transmission: The gear lever of the automatictransmission is normally an electronic switch that guides and
sends an instruction to the software that manages the gearbox.

 The following are the different types of Automatic Transmission:

• Torque Converter: which uses a torque converter to transmit the engine’s rational power to the wheels.

• Automated Manual Transmission: it utilizes a regular clutch and gear configuration, and also uses sensors, actuators,
processors, and pneumatic to boost manual gear use.

• Dual - Clutch Transmission: In its most original form, these will be two different clutch systems; one for odd and one for
even digit gears.

• Continuous variable Transmission: The band shifts up and down to vary its length and the gear ratio.
 COMPONENTS OF GEARBOX

 In a transmission box at least four components are required to fulfill its function. These components are:-

1. COUNTER SHAFT: Counter shaft is a shaft which connects with the clutch shaft directly. It contains the gear which
connects it to the clutch shaft as well as the main shaft.

2. MAIN SHAFT: It is the shaft which runs at the vehicle speed. It carries power from the counter shaft by use of gears and
according to the gear ratio, it runs at different speed and torque compares to counter shaft.

3. GEAR: Gears are used to transmit the power from one shaft to another. They are most useful componentof gear box
because the variation is torque of counter shaft and main shaft is depends on the gearratio.

4. BEARING: bearings are required to support the revolving part and reduce the friction. In the gear box both counter and
main shaft are supported by the bearing.
 FUNCTION OF GEARBOX

• The gear box is necessary in the transmission system to maintain engine speed (or torque) at the most economical value
under all conditions of vehicle movement.

• Provides speed and torque conversions because of the limitations of internal combustionengines. 

• Also facilitates change of direction of output shaft for reversing.

• Automotive gearboxes are used to reduce load on the engine by manipulating torque and speed.

• It is advisable to increase the gear to reduce the engine rpm to reduce wear on the engine, allow more control, and greater
speeds, better acceleration, and better fuel economy.

• Most gearboxes are used to increase torque & reduce the speed of output shaft. This produces a mechanical advantage.

• To convert the engine torque into the wheel traction required to overcome the motion resistance.
 OBJECTIVES

 GENERAL OBJECTIVE

• The general objective of this project is to design:- spur gear sliding mesh ; Drive power 15KW ; speed of 1000 r.p.m ;

speed ratio 20:1 & 10:1 ; ≥ 2 stage ; Parallel shaft arrangement Gearbox.

 SPECIFIC OBJECTIVE

• To design each and individual components of sliding mesh gearbox, such as:

:- gear, shafts, bearing, housing

• To select the appropriate material for the components.

• To select bearing and to solve geometrical analysis of sliding mesh gearbox.

• To compute force and stress analysis and to analyze the result.

 METHODOLOGY

• In order to design a gearbox, we can follow many steps. And for our design we follow the following Methodologies:

Collect Brief introduction

Justification of
Information and And description of Literature
Data Design
Sliding mesh gear review
Consideration
box

Model using Detail design

SOLID WORK Proper material
Based on given
2018 Selection
Specification
 LITERATURE REVIEW

 There is different scope for design and development of gearbox for use free longer life.

• RAHUL KUMAR has presented on [Design and simulation of 7 speed manual gear box]. in the late 19th century. in his
paper a gear box with 7 forward gears and 2 reverse gears has been described and the detailed 3D parametric model was
developed in Solid work.

• ATTHURU MANIKANTA REDDY1, AAKASH.K has presented on [Design and study of four speed sliding mesh gear
box] in 19th century. shows that in their paper deals with understanding of the gear transmission system principles with its
design and working.

• JIRI TUMA has presented on [Electric Hydraulic Accelerator Control Device in AMT] late 19th century, shows that in order
to regulate the fuel injection quantity for the non-electronic controlled engine.
 DETAIL DESIGN ANALYSIS

• Transmission box change the engine speed into torque when climbing hails and other uses depending on the condition. The
main components that we have designed includes gear, shafts, bearing, key and housing.
 GIVEN PARAMETERS :-

Power [kw]:- 15KW ; Input speed [rpm]: 1000 ; speed ratio: 20:1 and 10:1

; Shaft Arrangement:- parallel and Stage ≥ 2.

 GEAR DESIGN:

The gear material should have the following properties:

 ; High tensile strength to prevent failure against static loads

 ; High endurance strength to withstand dynamic loads

; Low coefficient of friction

 For First stage gears

Material : Harder Cast Steel

Bending strength = (172 - 223) Mpa

Allowable contact stress = (585 - 655) Mpa

 For Second stage gears

Material: Harder Cast Steel

Bending strength = (290 - 386) Mpa

Allowable contact stress = (1069 - 1172) Mpa

 The speed ratio of our drive is i=10, according to the standard, when i, is between 8 and 40: we have two stage speed
reducer. therefore, our design of gearbox is double stage and have 4 gears.
 SHAFT DESIGN
 A shaft is a component of a mechanical devise that transmits rotational motion and power.

 The material used for ordinary shafts is carbon steel of grades 40 C 8, 45 C 8, 50 C 4 and 50C12. The mechanical properties
of these grades of carbon steel are given in the following table.
Indian standard designation Ultimate tensile strength (MPa) Yield strength (MPa)

40 c 8 560-670 320

45 c 8 610-700 350

50 c 4 640-760 370

50 c 12 700 390

Sut = 700Mpa
Yield strength = 390Mp
 we selected 50c 12
 DESIGN OF INPUT SHAFT

A = E, bearing face width

B, distance between the left bearing and the next gear on the input shaft.
C, face width of gear
D, clearance between two gear and bearing
Assuming bearing face width to be equal to 30mm, and clearance between any two gears and Estimating
D1 = D5 =15mm
D2 = 24mm
D3 = 20mm
D4 = 16mm
  DESIGN OF INTERMEDIATE SHAFT

A = G, bearing face width

B = F, clearance between bearing and gear
C = E, face width of gear
D, clearance between two gears
Assuming bearing face width to be equal to 30mm, and clearance between any two gears and between bearing
and a gear to be 20mm, the following dimensions can be assigned.
A = G = 30mm
D = 20mm
B = F = 78mm
And as determined in the previous chapters face width of all gears in this design is 38mm, therefore,
C = E = 38mm
By adding each dimension the total shaft length can be determined as follows
L=A+B+C+D+E+F+G
L = 176mm
D4 = 48mm
D3 = D5= 40mm
D2 = D6 = 31.2mm
D1 = D7 = 30mm
  DESIGN OF OUTPUT SHAFT

A = E, bearing face width

B, distance between the left bearing and the next gear on the input shaft.
C, face width of gear
D, clearance between two gear and bearing
Assuming bearing face width to be equal to 30mm, and clearance between any two gears and between
bearing and a gear to be 20mm, the following dimensions can be assigned.
A = E = 30mm
D = 78mm
B = 20mm
And as determined in the previous chapters face width of all gears in this design is 38mm, therefore,
C = 38mm
By adding each dimension the total shaft length can be determined as follows
L=A+B+C+D+E
L = 176mm

D1 = D5 =30mm
D2 =48mm
D3 = 40mm
D4 = 31.2mm
 KEY DESIGN
• A key is a piece of mild steel inserted between the shaft and hub or boss of the pulley to connect these
together in order to prevent relative motion between them.
• It is always inserted parallel to the axis of the shaft and it used as temporary fastenings and are subjected to
considerable crushing and shearing stresses.
• Therefore the key material must be, 50C12, With Sut = 700Mpa & σy = 390Mpa

 For input shaft: The input shaft diameter is equal to d = 20mm, from standard table, the key which are
essential for the design are selected based on the diameter of the shaft.

For a 20mm diameter shaft

w = 8mm

t = 7mm
 For intermediate shaft:The intermediate shaft diameter is equal to d = 40mm & the key which are essential
for the design are selected based on the diameter of the shaft.

For a 40mm diameter shaft

w = 14mm

t = 9mm

 For output shaft: The output shaft diameter is equal to d = 40mm & the key which are essential for the
design are selected based on the diameter of the shaft.

For a 40mm diameter shaft

w = 14mm

t = 9mm
 BEARING DESIGN

 Bearings are manufactured to take pure radial loads, pure thrust loads or a combination of both.

 Depending on the type of friction between the shaft and the bearing surface, bearings are classified into two
main groups
: Sliding contact bearing.
: Roller contact bearing.

 For this design, we selected roller contact bearing

because it is anti-friction, which must satisfy a life
hour of Lh = 12000hrs
 HOUSING DESIGN

 Gear box housings or casings are containers in which the internals, namely, the gears, shafts, bearings, oil seals,
bearing covers and other components are mounted.

 As a material for gear box casings, good quality cast iron is used in most of the cases. Cast iron housings have good
damping properties and are free from noise.

 Known values will be:

Outside diameter of gear one(OG1) = 72mm

Outside diameter of gear one(OG4) = 328mm

Center distance between input shaft and intermediate shaft(C1) = 160mm

Center distance between intermediate shaft and output shaft(C2) = 192mm

Clearance between a gear and the gear box(C’), making it 60mm

 Having these dimensions the wall thickness(S) of the gear box can be found according to the following table.

Where (L) is the largest dimension of the housing in (mm).

L = OG1/2 + C1 + C2 + OG4/2 + C’
L = 36 + 160 + 192 + 164 + 60
L = 612mm
Selecting welded construction, non-case hardened gear
s = 0.004L + 4 mm =0.004x 612 + 4 ≈ 7 mm
Top cover thickness:
Sc = 0.8s =0.8x7 ≈ 6 mm.
  LUBRICATION SELECTION

 When one surface moves over another, there is always some resistance to movement, and the force which
opposes movement is called friction.

 Lubrication is simply the use of material to improve the smoothness of movement of one surface over
another, and the material used to facilitate this process is called lubricant.

 Lubricants are usually liquids or semi liquids, but may be solids or gases or any combination of solids, liquids
and gases.

 Lubricants are usually divided into four basic classes, these are:

 Oils: - a general term used to cover all liquid lubricants, whether they are mineral oils, natural oils,
synthetics, and also process fluids.
  Greases: - there are oils which contain a thickening agent to make them semi solid, but it is sometimes
convenient to include anti-seize pastes and the semi-fluid greases under the same leading.

 Dry lubricants: - there include any lubricants which are used in solid form and may be bulk solids,
point like coatings or loose powders.

 Gases: - the gases usually used in gas bearings is air, but any gas can be used which will not attack the
bearings, or itself decomposed.

 The two main factors needed for selecting the type of lubricants are speed and the load. At high speed we
need less viscous lubricant, where as to increase the load and decrease the speed, we need higher viscous
lubricant.

 From the oil type lubricants, we selected mineral oil because of:

Wide range of viscosity are available, Good boundary lubrication, Long life, Cheap(low cost)
 CONCLUSION AND RECOMMENDATION