4 5924833094782682822

Commented [h1]: Do not use the word art for titles and
chapters
INSTITUTE OF TECHNOLOGY
SCHOOL OF MECHANICAL&INDUSTRIAL ENGINEERING
HOST COMPANY:
NYALA MOTORS S.C BAHIR DAR BRANCH
i
INTERNSHIP REPORT AT NMSC.
NAME ID NO
FIKIR GASHAW…………….. 766/2003
HENOK BIRHANIE……………2534/2003
MELKAMU ZERIHUN………….2468/2003
DURATION OF TIME:
OCTOBER 14/2013 TO FEBRUARY 6/2014
OUR MENTOR
Mr. KINDU WONDEM
SUBMISSION DATE:
18/02 /2014
I ii
PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

Partial View of Nyala Motors S.C Bahir Dar Branch
I i

Declaration
This report is prepared by us, FIKIR GASHAW from design, HENOK BIRHANE from
manufacturing and MELKAMU ZERIHUN from thermal streams of mechanical Engineering by the
continues guidance and advise of our mentor, Mr. Kindu. All of us have contributed equally to write
this report.
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Acknowledgement
Firstly, we would like to give a great praise to our God forthe help to write this report. Secondly,
we would like to thank our mentor Mr. Kindu for his continuous support and advise to write
and compile the report. Thirdly, we have a great thanks to Nyala motors share Company which
gives the opportunity to work with workers in the company. And also we would like to thank all
of Nyala motors share Company mechanics and electricians, specially our supervisor
Mr. Belay Zeleke who helps us to know the practical activity in the company.
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Executive summary
An internship is a work related learning experience for individuals who wish to develop hands on
work experience in a certain occupational field. It is necessary for students to develop the spirit
of self-supporting and hard working. Bahir Dar university institute of technology practices the
teaching model integrating internship regular class. We recently have done our internship at
Nyala Motors Share Company by combining theoretical knowledge and practical work.
Also we could learn the meaning of diligence, perseverance, frugality and trust worth. Thus
internship is very important to produce skill full generation for Ethiopia in both practical and
theoretical part.
This report contains the brief history of the Nyala Motors Share Company and its main product
as well as its main customers and the main goal, mission, vision and values of the company. The
report also includes the organizational structure and its work flow.
This report also contains the challenges that we have faced and measurements we have taken for
them. And also it includes benefits that we have gained in terms of improving our practical skills,
in terms of upgrading our theoretical knowledge; in terms of improving inter personal
communication skills and improving leader ship skills. And at last it contains recommendations
for the company, for the school and for UIL office.
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List of tables
Table 2.1……………………..material selection
Table 2.2……………………..material properties
What about list of figure Commented [h2]: ???????
List of acronyms
UIL- University industrial linkage
C. E .O –Chief executive officer
Coo. –coordinator
Dept.-department
Admn– Administrator
NMSC - Nyala Motors Share Company
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Table of Contents
CHAPTER ONE ............................................................................................................................................... 1
1. Back ground .......................................................................................................................................... 1
1.1 Brief History of Nyala Motors Share Company (NMSC) ..................................................................... 1
1.2 vision, mission, values and objective of the company ....................................................................... 2
1.3 It’s over all organization structure ...................................................................................................... 3
CHAPTER TWO .............................................................................................................................................. 6
2. over all Intern ship Experience ................................................................................................................. 6
2.1 Why Do We Select The Company? ..................................................................................................... 6
2.2 Section of the Company We Have Been Working .............................................................................. 6
2.2.1 Layout of the Company ................................................................................................................ 7
2.3 The Work Flow in the Working Section .............................................................................................. 8
2.4 Tasks that we have Been Executing .................................................................................................... 9
2.5 Mechanical Engineering Methods and Tools for Executing Tasks .................................................... 10
2.5. 1 The Most Important Hand Tools are the following .................................................................. 10
2.6 Quality (status) of our work in performance of tasks....................................................................... 17
2.7 Major challenges we have been facing............................................................................................. 17
CHAPTER THREE .......................................................................................................................................... 19
3. THE PROJECT .......................................................................................................................................... 19
3.1 Design of dual lifting mechanically operated bottle car jack: .......................................................... 19
3.2 Problem statement ........................................................................................................................... 19
3.3 OBJECTIVES ....................................................................................................................................... 19
3.4 Material selection: ............................................................................................................................ 20
3.5 Design Data ....................................................................................................................................... 21
3.6 Methodology to Avoid the Problem ................................................................................................. 21
3.7 Design of first nut ............................................................................................................................. 21
3.8 Design of second nut ........................................................................................................................ 24
3.9 Design of housing nut ..................................................................................................................... 24
3.10 Design of solid screwed shaft ......................................................................................................... 25
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3.11 Design of worm and worm gear ..................................................................................................... 26

3.12 Force analysis for worm gear ........................................................................................................ 27
3.13 Bevel gear Assembly ....................................................................................................................... 28
3.14 Determination of pitch angle for bevel gear .................................................................................. 29
3.15 Handle connecting the jacks ........................................................................................................... 31
3.16 Bearing selection ............................................................................................................................ 31
3.17 Selection of foot step bearing ....................................................................................................... 32
3.19 Working principle............................................................................................................................ 33
3.20Lubricants ........................................................................................................................................ 33
3.21 Short summery of dual lifting car jack ............................................................................................ 33
CHAPTER FOUR ......................................................................................................................................... 37
4 OVER ALL BENEFITS WE GAINED FROM THE INTERNSHIP ....................................................................... 37
4.1 parts of car and their function .......................................................................................................... 37
4.1.1 Parts of engine ........................................................................................................................... 37
4.1. 2 Braking System.......................................................................................................................... 44
4.1.3 Clutch and flywheel ................................................................................................................... 48
4.1.4 Differential ................................................................................................................................. 54
4.1.5 LUBRICATION SYSTEM: .............................................................................................................. 55
4.2 Parts of car to be maintained ........................................................................................................... 56
4.3 parts of car to be serviced ................................................................................................................ 57
4.4 Clarity of theoretical knowledge that we know before .................................................................... 57
4.5 Increasing of problem solving techniques ........................................................................................ 58
4.6 Developing of team work and interpersonal communication.......................................................... 58
4.7 Respecting work ethics ..................................................................................................................... 59
4.8 Leadership skill.................................................................................................................................. 59
4.9 Development of Entrepreneurship Skill............................................................................................ 59
4.10 Work Shop Safety ........................................................................................................................... 60
Chapter five ................................................................................................................................................ 63
5 Recommendation .................................................................................................................................... 63
I vii

Chapter six .................................................................................................................................................. 64

6 Conclusion................................................................................................................................................ 64
I viii

CHAPTER ONE
1. Back ground
1.1 Brief History ofNyala Motors Share Company (NMSC)

Nyala Motors Share Company was established in April 1973 in line with the commercial code of
Ethiopia. It can be said that Nyala Motors Share Company has been one of the front runners in
the development of the private sector in Ethiopia in the last 40 years. The continued expansion of
the company has become a trendsetter to others in laying a firm foundation for the success and
expansion of corporate development. Nyala Motors S.C is the sole importer and distributor of
Japanese made Nissan Motor Automobiles, Station Wagons, Pick Ups, Forklifts, UD Trucks,
Dump Trucks, Cargo Trucks, Tanker Trucks, Mixers, Asphalt Distributing Trucks, Fork-Lifts,
Agricultural Tractors and implements. Nyala Motors Share Company (NMSC) has four
branches. These branches are Bahir Dar, Deredawa, Mekele and Awasa. Addis Ababa is the
center of the branches. Nyala Motors Share Company (NMSC) in bahirdar branch was
established in May 2002E.C under the Commercial Law of Ethiopia. The company started by the
owner of Sheikh Mohammed H. Al-Amoudi.Now at this movement in the company there are so Commented [h3]: Write with time new roman, alignment is
justify, ….. check left, right, top and bottom margins, 3,2,3,and 2.2
many employers such as 4-Mechanics, 2-Electricians,4-Body mans,1-Program manager,1- cm respectively
accuntant,6-wach man sand 1-planter. NMSC is the Sole and Exclusive Distributor of countries
class brands; to mention few:
UD TRUCK (heavy duty)
Logging Trucks
Trick Tractors
All light vehicle Nissans (especially model)
Y-60
Y-61
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D-22
1.2 vision, mission, values and objective of the company

a) Vision
“To be the leading national assembler and distributer of superior quality Vehicles, Trucks and
Machineries supported by reliable after sales service”
b) Mission
“We strive to be customer oriented national company that is socially responsible and can bring
growth through delivery of better products and services. “
c) Values
The success of our company should be measured by the contribution it gives to shareholders,
Employees, Government and Community.
Our motto is safety and quality comes first.
Working towards customers’ satisfaction
Team work
d) Objectives.
Main objective of the Company:
According to by the law of the company the main objectives are;
 To engage in the supply of automotive spare parts. Commented [h4]: The first bullet used the dot like .
 To carry out all business of import/export and distribution of automotive and allied
products as well as industrial, construction and agricultural machineries.
 To participate in tenders geared towards the development of the country.
 Provision of after sales services for equipment imported in the country.
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 To carry out any business connected with the above objectives.
1.3 It’s over all organization structure

Nyala Motors Share Company is currently organized in four divisions and seven Departments that enable
to its customers and avail modern after sales facility; it has established four branches in four corners of
the country in the last eight years. Following the establishment of branches and sub-dealers network, our
customers have been privileged to have easy access to genuine spare part sales and maintenance services
provided by the company. These four divisions and seven main departments and their sub departments are
explained in the overall organization structure are shown below.
Since its establishment, Nyala Motors Share Company has invested huge amount of resources &
relentlessly renovated and upgraded its after-sales facility in material & manpower including modern
facelift of its premises to the standard demanded by the automotive industry. It has also increased the
stock availability of spare parts in quantity & line items. Accordingly, NMSC has set-up a well-organized
& fully equipped after sales service center intended to give efficient technical support to its customers
with the help of qualified, well-trained and skilled staffs. To this end, in addition to the Sub dealer’s
network operating in many corners of the country we have opened our own well-organized & state of the
art branches (Bahir Dar)serving as after sales service & sales centers in the regional capitals of Amharic
(Bahir Dar), Tigray (Mekelle), SNNPRS (Hawassa) & Dire Dawa City Adm. (Dire Dawa). This is
believed to ensure the continuous & on time supply of reliable after sales support during the lifetime of
the equipments supplied enhancing our proximity to our esteemed customers. The company has 200
Permanent employees and 10 Contract Employee's including Branches.
Nyala Motors Share Company is currently organized in four divisions and seven departments that enable
company to give the best service to its customers. In line with the company’s commitment to be close to
its customers avail modern after sales facility ; it has established four branches in four corners of the
country in last eight years. Following the establishment of branches and sub-dealers network, our
customers have been privileged to have easy access to genuine spare part sales and maintenance services
provided by the company.
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ShortHistory of Nyala Motors S.C Bahir Dar branch
Nyala Motors S.C Bahir Dar branch has been given supply and sale of Nissan genuine parts for about
five years. And now the company is giving maintenance and service of Nissan vehicles starting from
2002 E.C due to increasing of Nissan vehicles in the region. This branch is constructing building for the
maintenance and service of bull dozer. For the time being the company has twenty two workers those are
seven watch men, one gardener, one compound cleaner , five officers ,three mechanics , two
electricians, one painter and two body workers.
Organizational structure by chart
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Board of directors
C.E.O
Executive
secretary
Director of Director of Director of Director of

legal & finance and sales & product
admin. p/admin. marketing support
Service service
Service Branches Spare

Human General Machin parts
Finance&p IT UD dept.
resource Service ery & sales
rop.Adm.d Admini Truck manager
coos. superviso equip. dept.
ept.manag strator sales
r sales Manager
er dept.
manag dept.
Import & er manger
logistic
dept.
manager Nissan
Hawass Bahir Dire Mekel
motor sales
a Dar Dawa e
dept.
manag mana mana manag
manager
er ger ger er
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CHAPTER TWO
2. over all Intern ship Experience
2.1 Why Do We Select The Company?

Starting from the time when the University Industry Linkage (UIL) paper is given to us ,we were
searching a company to make a pre-set up for the internship work by sending the UIL paper through post
office, fax and by direct contact to different companies which are appropriate to mechanical engineering.
When we say appropriate to mechanical engineering, since one objective of the internship is to
develop our practical skill and to clarify the theoretical knowledge. Thus the companies for mechanical
engineering students should be those, their theoretical concepts found in mechanical engineering courses.
For example metal work and manufacturing in the course material science, parts of a vehicle in machine
elements etc.
Among the companies we sent and gave by direct contact the UIL papers, we were lucky to enter
Nyala Motors Share Company Bihar Dar branch by lottery. We gave the papers to the company by direct
contact and at one appointment day in September, we 14 students are selected from 28 students to work in
the company.
2.2 Section of the Company We Have Been Working

We have been working at the maintenance and service of vehicles with the director, three
mechanics, two electricians, two body workers, one painter and one car washer. This section is
the main practical working area and the last level of work flow. Damaged vehicles at specific
kilometer service came from the customers and the section workers responsibility is only
maintain and service those vehicles.
Most the vehicles enter to the company for specific kilometer wheel hub service and the
service is short and simple. The rest of vehicles enter to the company by the case of damage and
the work is time consuming and tedious. At this company only vehicles designed and
manufactured by Nissan Company Japan are maintained and serviced.
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2.2.1 Layout of the Company

The whole campus of the company is the practical work area except some offices for
manager, genuine parts store. In the area there are automobile parking for those to be maintained,
the car washing area, welding room, the site of bolo which is used to check whether a car is
damaged or not, the painting room, site of water and air compressor, site of lifting mechanisms
bend pack and crane, site of wheel balance and hydraulic press and tool sitting and clothe
changing room.
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2.3 The Work Flow in the Working Section

From this the work flow looks like the following; first the customers that have Nissan vehicles
to be maintained or serviced ask the company’s director. Then after the vehicle enter to the
company and registered in order of their time entrance. Then the director assign the workers
(mechanics, electricians, body men etc.) based on the need of customers. After the workers are
assigned at any vehicle in their specific ability of maintenance and service. The workers ask
genuine parts from shop workers to change the old and damaged parts.
Waste oil has a container in the company at which it is stored and gives income to the company
by selling to customers which need it for painting wood and other materials to prevent from
insects which bore wood.
The old (changed) parts of the vehicle are packed with the package of genuine parts and returned
with maintained and serviced to the customers.
When each worker finishes his/her assigned work ,he/she reports to the director and then the
director tell the customers, finally the customers come and pay the repairing cost to the finance
case team and take their vehicles out of the company. The work flow can be shown bellow.
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Director
Director assigns workers
Customers come with their vehicles
And ask the director

Workers Customers
Workers report to the director Commented [h5]: Check this figure over lap on the other
document
Maintained cars
drive out of the
Workers maintain and company
Ask genuine parts
service vehicles
Maintained car
2.4 Tasks that we have Been Executing

Even if we are not a professional, we have been as a mechanic, but we work in collaboration with the
known company's mechanics by asking everything which not clear in the practical work. Some of the
tasks that have been executed are: - assembly and disassembly of wheel hub parts, washing of dirty parts,
the engine assembly, Valve adjustment, Carrying of waste oils to containers, liftingofcars with the bend
pack and hydraulic jack etc.
Generally we can say that we have been participated in all working that company mechanics do. But we
work by assignment of mechanics both in the maintenance and service of the Nissan vehicles. In all
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mechanics works that had been done in the period of internship ,we had participated in all practices like,
engine maintenance ,differential maintenance, hub service, changing of fuel and oil filters, changing of
batteries ,maintenance of fuel tankers ,washing of radiators in power control in welding of body cars
and so on.
2.5Mechanical Engineering Methods and Tools for Executing Tasks

The tools that we have been use to perform our tasks in the mechanics work are those tools that w e
use in mechanical engineering workshop. There are two division of tools based on the source of energy
applied on the tools in the maintenance and service of vehicle .These are hand tools at which we apply
our force to operate with them, and power tools which operate by electric, compressed air or hydraulic
pressure.
2.5. 1 The Most Important Hand Tools are the following

Wrenches: are used to turn screws, nuts, and bolts with hexagonal heads. There are three types
of wrenches. Open end, box (closed) and combination wrenches.
1. Open wrench;are simplest to use and usually have different size on each end.
Fig .2.1 open wrench
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2. Closed wrench; it does the same job as open wrench but are of limited use in covered space
and have different size on each end.
Fig 2.2 closed wrech
3. Combination wrench; has box on one end and open end on the other end. Both ends are the
same size.
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Fig .2.3 combination wrench
Ratchets; are used to remove nuts from the joint and tighten nuts with bolts. It has detachable parts
called, socket and extension.
Torque wrenches: used to tighten nuts with bolts properly. Because it shows amount of toque.
Adjustable wrench; used to tighten and remove different size nuts that has a jaw that can be adjusted to
fit a nuts and bolts head with various size.
Pliers (pinesaps); used t grip different size of materials.
Chisel; they are driven by hammer to cut metal by holding it in one hand and the hammer by the other
hand.
Screw driver; used to drive or turn screws.it can be flat or Philips head.
Snap ring remover; used to remove rings from the assembly.
Fig 2.4 snap ring remover
Hack saw: used to cut metals by replaceable teeth.
Files: are used to smooze parts of metals.
Fig. 2.4 files
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Filer gauges: used to adjust the valves & to measure the air gap between assembled parts.
Centerpunches: used to knock out rivets. Pins and indent point from the assembly.
Bench vice: the most common shop tools which is used to hold a part that is being sawed, filed, chiseled
and other works.
Some of the power tools are the following
Electric drill: is used to drill metals and other works by electric power. It has electric motor
which drives the drill bit.
Car washer: it is forced by electrical motor and used to wash cars by pressurizing the water.
Electrical car lifter (bend pak): works by electrical system and used to lift cars above the height of a
man.
Fig 2.5 bend pak
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Air compressor: is driven by an electric motor and used to compress air for different purpose.
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Fig 2.6 air compressor
Electrical crane: it is used to displace cars from one place to another by human command. But at the
moment it is not functional to the company.
The most common tools used in the work area look like the above and the mechanical engineering
methods that we have been used to execute our tasks discussed as follows:
Hammer: used to strike the metal or plastic body. A hammer can be plastic or metal due to their
requirement.
Fig. 2.6 hammer
It has a wide range of application in the maintenance and service of cars. Basically it is more useful for
body workers to make straight damaged and bent body parts. Also for tightening and loosening of bolts,
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nut assembly which has high torque, we use this method to turn nuts or bolts by striking wrenches handle
with hammer.
Welding: is the basic permanent joining method of broken parts of vehicles. Also this welding is used for
cutting purpose to avoid unwanted metal part or when there is problem in nuts and bolts joint we cut with
welding and avoid from the car.
Fig. 2.7welding machine
Riveting: is also a permanent joining method of mechanical elements which is mainly applicable for
joining brake lining and brake shoe in drum type of brake.
Joining by bolts and screws : The tightening and loosening of bolts and screws are the back bone of the
car maintenance and service .Because to do the required work, first the bolts and screws must be loosen
and after maintenance those joints must be tightened properly. Without bolt and screws joints vehicle
will not be functional.
Extension of arms in tightening and loosening: from mechanical engineering cause we know that as
arm length increase in certain rotation system about a certain axis the moment will increase. We have
been done this method in practice when we tighten and loosen bolts, nuts, screws etc. when it is difficult
to rotate; we simplify it by increasing the handle.
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Lifting mechanism: Lifting of cars has a great role in the maintenance and service of cars, for wheel hub
service and to look the underside of car parts maintenance. This is one of the mechanical engineering
methods to lift things which have weight above man's lifting ability such that we have learned in machine
elements about power screws, bottlejacks and scissor jacks etc.
Lubrication: most of the movable part of a car has their specific lubricating oil which is used for smooth
motion and heat dissipation. But we also use lubrication to disassemble mechanical elements which are
difficult to disassemble by mechanical force .For example inner race of a bearing and shaft can be
disassemble by lubrication then applying smallest mechanical force.
Cutting: is used in mechanics where necessarily mostly it is applicable for body works. The most widely
used mechanical engineering methods and tools are those mentioned above.
2.6 Quality (status) of our work in performance of tasks.
In all period of the internship we had good performance in full filling our responsibilities and respecting
the rules of the company. We have been working as the professional workers such that we have a
goodprofessionalism.Also we were punctual, reliable, independence in work and we have good
communication skill with the whole workers of the company.
To satisfy our objective we were fast to learn and work any task responsible to us .Also we have many
contribution to the company in solving problems and in finishing very heavy and time consuming works
in cooperation with the workers.
2.7 Major challenges we have been facing

The main problems in the company are luck of technical tools.Because, Nyala motors at Bihar Dar
branches is new i.e. it did not work for long period of time. Such that the company does not full fill all
technical tools needed for the maintenance and service of vehicles. And the other reason is the tools to be
full filled are expensive to buy.
The other main problem in the company is the tools present need high labor force to operate with them.
Generally the identified problems in the company are;
 Absence of engine crane.
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 Absence of gear box loader and remover.

 Absence of waste oil installation.
 Absence of axle nut wrench.
 Instability and bending of hydraulic press.
 Absence of differential loader and remover.
 Non-functionality of mechanically operated bottle jack.
 Absence of oil container louder.
After we had been identified all the above listed problems, we had decided to solve them by taking them
as aproject.All the students that we have been working in the company take responsibility to solve or
simplify the problems and we divided them to do as a project.
Each problem is done as project by each group of students.i,e those problems are compiled with their
solution and given to the company and the Bahia Dar branch manager is asking to the central Addis-
Ababa Nyala motor manager (A.A.N.M.M)for the manufacturing of designed technical tools.Becuose the
solutions for the problems are design of those tools. Thus based on the willingness of the Addis Ababa
share company manager (A.A.S.C.M), the designed tools will be manufactured and the problems will be
avoided. Among those problems our group was responsible to solve the non-functionality of single car
jack, by designing a dual lifting mechanically operated car jack and its design procedure is expressed in
detail in the next chapter.
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CHAPTER THREE
3. THE PROJECT
3.1 Design of dual lifting mechanically operated bottle car jack: Commented [h6]: First letter is capital
3.2 Problem statement

The main problem which causes us to design the dual lifting car jack is the non functionality of
mechanically operated bottle car jack due to; Commented [h7]: When to design this dual lifting car jack the
company’s mechanically operating bottle car jack is non functional
and the system operated by human power
It needs high man power to work using it.
Need of safety stands.
Its lifting ability is low because it can lift one wheel side of a car. Commented [h8]: Unnecessary
3.3 OBJECTIVES
Main objective:
To design a dual lifting car jack that avoids the above problems. Commented [h9]: The main objective of this project is to
design a dual lifting car jack that avoids the system operated by
human power and substitute by simple machine
Specific objective:
Design of worm gears
Design of worms
Design of 1𝑠𝑡 nuts
Design of 2𝑛𝑑 nuts
Design of housing nuts
Design of bevel gears
Design of screwed solid shaft
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Design of handle
Design of bevel gear cover
Selection of foot step bearing
Selection of supporting bearing Commented [h10]: These are the methodology parts of the
project, so instead of this “ to reduce the human power, to analysis
the structural design, to be analyze the materials of the machine
and to optimize the cost of the machine etc..” u can add
3.4 Material selection:for the parts which will be subjected to comparison load the material
that we have been selected is castiron because it has high strength for compression load and for
handles, worm and bevel cover at which Small torque is applied the material is steel.
Part name Material
Worm gear Cast iron

Worm Steel
𝑠𝑡
1 nut Cast iron
𝑛𝑑
2 nut Cast iron
Housing nut Cast iron
Bevel gears Cast iron
Screwed solid shaft Cast iron
Foot step bearing Cast iron
Supporting bearing Cast iron
Handle Steel
Bevel gear cover Steel
Table 2.1 material selection Commented [h11]: This is chapter 3 so u should be table 3.1,
3.2……
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3.5 Design Data

Maximum weight to be lifted 𝑊𝑚 = 3 ton=294300N.Working load = 2 ton = 1296200N
Height at lower position = 330mmActual length of nuts are = 200mm
Maximum distance between two jacks = 1000mm.
Material properties that is elastic limit and modulus of elasticity.
tension(MN/m²) Compression(MN/m²) Share(MN/m²) E (GN/m²) C Density

(GN/m²) kg/m³
Cast 43.5 350 43.5 70 29.4 7210
iron
Carbon 217 217 140 203 78.4 7830
steel
Table 2.2 material property Commented [h12]: Table should be write on the top of the
tabel
3.6 Methodology to Avoid the Problem

To avoid the above listed problem we have design the dual lifting car jack which is done as follows;
First we design a gearing mechanism i, e assembly of three bevel gears which are positioned in such a
way that the two bevel gears are connected to the handle of the bottle car jack which is connected to the
worm. i.e. the driver of worm gear the handle of shaft at which these gears are connected are collinear to
each other or they are in line and the third bevel gear inserted between the two gears perpendicular to
them. The shaft of the third gear is perpendicular to the shaft of the two gears. And the assembly of three
gear shaft makes aT-shape.Also the gears assembly joined by box type housing. The two shafts inserted to
the box at right and left side and the third at the front. The two shafts are hands of the jacks which are in
line and the third shaft which is inserted at the front is the handle to be rotated by man power. To transmit
motion to the right and left side bottle car jacks.
3.7 Design of first nut

Since the nuts are subjects to compression load which leads to the buckling of nuts .we design by using
Euler‘s formula. This formula is applicable for long columns .First let us check whether the nut is long or
short column.
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𝜎𝑐𝑟 = Wcr⁄A =Cπ²E/ (L/K) ²
where 𝜎𝑐𝑟 - cripping stress of cast iron
𝑤𝑐𝑟 - Cripping load
C-fixity coefficient by considering the nut as one end fixed and the
Other free. C=0.25 from STD table
E – Modulus of elasticity E= 70Mpa for cast iron
L/K - slenderness ratio
Now equating the cripping stress to the crushing stress
𝜎𝑐𝑟 = Wcr⁄A =Cπ²E/ (L/K) ²=350Mpa
(L/K) ²= 493.48
L/K=22.2
Therefore the slenderness ratio is less than 80. Thus the nut is short column.
When slenderness ratio is less than 40 then diameter of nut can be obtained by equating the load acting
on the nut to its tensile strength.
𝜋
W = d²𝜎𝑡 but, area is for hollow tube or nut Commented [h13]: Editing of the document i.e. space and
4 alignment and so on….
𝜋
A = (D²-d²)
4
Where D - outer diameter of nut
d - Inner diameter of nut
W - Load acting on the nut
𝜎𝑡 –tensile stress
I 22

Based on the Eulerian formula the diameter of holes through the nut
d =0.8D
𝜋
Then W = (D²-0.8D²)*43.5
4
.D =154.7
D~155mm
From here d =0.8D
d =124mm
Thickness of the nut is
2t =D –d
2t=155-124
t =15mm
Note: thickness of nut is equal to thickness of housing t = 15mm.
50 200 depth of thread =6mm
Core diameter of inner 𝑑𝑐𝑖𝑛 =124+6 =130mm
Fig.3.1 first nut Core diameter of outer 𝑑𝑐𝑜𝑢𝑡 =155 – 6 =149mm
I 23

3.8 Design of second nut
To get the outer diameter of the 2𝑛𝑑 nut, we can add twice of thickness in outer diameter of the 1𝑠𝑡 nut.
Outer diameter of first nut is equal to inner diameter of second nut d =155mm. The outer diameter of
second nut is equal to 185mm or D Length of 1𝑠𝑡 nut = 200mm
50 150 200
155
185
Fig.3.2 second nut
3.9 Design of housing nut

The diameter of second nut is equal to inner diameter of housing nut is equal to 185mm.
Outer diameter of housing nut = 185 +2t =215mm or D = 215mm
I 24

Core diameter 𝑑𝑐 =185 +6 =191mm
Note: the housing nut is manufacturing by casting
3.10 Design of solid screwed shaft

The diameter of solid shaft = inner diameter of the first nut =124mm.
200
40
124
Fig .3.3 solid screw
To 118mm which is Core diameter of the screw is equal calculated as
𝑑𝑐. = d - 2𝑑𝑝 = 124 -2*6 =118mm where 𝑑𝑝 is depth of thread of a screw taken from kermis text book of
mechanical engineering.
I 25

3.11 Design of worm and worm gear
Fig. 3.4 worm and worm gear
Take in put speed of man power
NW =10 rpm
Center distance between shafts x = 150mm
Modulus of gear m =12mm
Velocity ratio = 4
𝑁𝑊 10
V.R= ,4= , NG =2.5rpm
𝑁𝐺 𝑁𝐺
Diameter of worm DW =3pc where pc =m =12*π =37.68mm
DW =3*37.68 = 113mm
𝐷𝐺+𝐷𝑊 𝐷𝐺+113
Center distance x = 2
, 150 = 2
I 26

DG =300-113 =187mm
𝐷𝐺 187
Teeth of gear TG = = =16
𝑚 12
𝑁𝐺 2.5
Lead angle λ, tan λ³ =𝑁𝑊 = 10
Pressure angle from STD table is 25˚.
3.12 Force analysis for worm gear

First take input data
Power p =1kwatt
Worm gear speed NG =2.5rpm
𝑃
Torque T = , ω is angular speed =2πN
𝜔
6000
T = 2𝜋𝑁 = 955Nm.
Check tangential load
The formula that tangential load acting on the gear
2𝑇 2∗955
𝑊𝑇 = = =122N, we know that the tangential design load is
2𝜋𝑁𝐺 2𝜋∗2.5
6 𝜋𝐷𝐺∗𝑁𝐺
𝑊𝑇 =(𝛿𝑜 * CV)*b *π *m *y where CV – velocity factor CV = , V -velocity = = 0.024mm
6+𝑉 60
0.92
so CV =0.99. y –tooth form factor y =0.154 - 𝑇𝐺
=0.097 𝑏-face width from text book, b= 2.15𝑝𝑐 +5mm
= 86mm.
𝑊𝑇 = 𝛿𝑜 *CV* b* π *m *y =56* 0.99*86*3.14*12**0.097 =17426.3N
𝑠𝑖𝑛𝑐𝑒𝑡ℎ𝑖𝑠𝑖𝑠𝑚𝑜𝑟𝑒𝑡ℎ𝑎𝑛𝑡𝑎𝑛𝑔𝑒𝑛𝑡𝑖𝑎𝑙𝑙𝑜𝑎𝑑𝑎𝑐𝑡𝑖𝑛𝑔𝑜𝑛𝑡ℎ𝑒𝑔𝑒𝑎𝑟 17426.3N> 122N so, design is safe.
Check for dynamic load
I 27

𝑊𝑇 17426.3
We know that dynamic load 𝑊𝐷 = = =17602.4N>17426.3N dynamic load should be greater
𝐶𝑉 0.99
than tangential load so, design is safe.
C) Check for static load
We know that the static load 𝑊𝑆 = 𝛿𝑒 *b*π*m*y where 𝛿𝑒 −endurance limit stress =84Mpa
for cast iron. 𝑤𝑠 =26403.4N since 𝑊𝑆 > 𝑊𝐷 that is 26403 .4> 17602.4
So the design is safe.
d) Check for wear load
We know that the wear load is calculated as
𝑊𝑊 = DG * b*k where k- load stress factor for cast iron K =1.035
𝑊𝑊 = 187*86*1.035 =16644.8N
Since wear load is greater than tangential load that acting on the gear, so the design is safe.
3.13 Bevel gear Assembly

The bevel gear assembly is used to transmit power the hand the lifting jacks. Thus to avoid the human
power loss we select a one-to-one velocity ratio and miter gear assembly. The number of gears is three
that is one connected to handle and other two to left and right splined shaft connected to the worm of the
jacks. The one connected to the handle is used to drive the other two gears with one to another one to one
velocity ratio.
Commented [h14]: Not clear since during the editing the figure
is detached
I 28

Fig .3.5 bevelgear assembly
All three gears have equal diameter so that they have One to one velocity ratio.
Let DGR-right side gear diameter
𝐷𝐺𝑅 𝐷𝐺𝐿 𝑁𝑃 𝑁𝑃
DGL -left t side gear diameter V.R = = = = =1
𝐷𝑃 𝐷𝑃 𝑁𝐺𝑅 𝑁𝐺𝐿
3.14 Determination of pitch angle for bevel gear

Let Ѳ𝑝 =pitch n angle for pinion gear.
Ѳ𝑃𝑅 -Pitch angle for right side gear Ѳ𝑃𝐿 - Pitch angle for left
Ѳ𝑆 -angle between two shaft axes Ѳ𝑠 = Ѳ𝑝 + Ѳ𝑃𝑅 = Ѳ𝑃 + Ѳ𝑃𝐿 =90˚.
1
Ѳ𝑃 =tan−1 ( ), but V.R =1 Ѳ𝑝 =tan−1 ( 1) =45˚
𝑉.𝑅
Given data
2𝜋𝑁
P = 1Kwatt Np =10 rpm ωp = =1.05rad/s T =P/ ωp =953Nm.
60
Since we have not means of calculation the pitch diameter for the gears which can give
Appropriate diameter Which can fit to the designed worm ,so that the diameter is Dp =DGR =DGL
0.912
=80mm.Gear and pinion shaft diameter can be assumed to tooth form factor , y =0.154-
𝑇𝐺
Tooth profile Ф =20˚ full depth m-module =5mm taking number of teeth from STD table = 16 Tp
𝐷𝑃 𝐷𝐺𝑅 𝐷𝐺𝐿 80
=TGR = TGL = = = =5mm.
𝑚 𝑚 𝑚 16
The formative number of teeth for pinion TEP =sec 𝜃𝑃 TEGR = TGRsec 𝜃 𝐺𝑅 TEGL
=TGLsec 𝜃𝐺𝐿
But 𝜃𝐺𝐿 = 𝜃𝐺𝑅 =𝜃𝑃 = 45° ,therefore TEP = TEGR = TEGR = TEGL =16*sec 45 = 22.63°.
Tooth form factor YP =YGR =YGL, So that the design is based on the pinion gear.
I 29

3 𝜋𝐷𝑃𝑁𝑃
Take velocity factor CV = , V= = 0.042 m/s , CV =0.98
3+𝑣 60
𝐷𝐺 80
Length of pitch cone element L = = =56mm.
2 sin 𝜃𝐺𝐿 2 sin 45
L/b should be not exceed 3, taking L/b =3 then b =56/3 =19mm.
𝑏 𝐷𝑃
Mean radius of pinion Rm = (L -2) * 2𝐿 =33mm. Tangential force acting on the mean radius,
𝑇 955
WT =𝑅𝑚 = 33
= 29N
Axial force acting on the pinion and gear shaft WRH =WTtan ∅ sin 𝜃𝑝 =29tan 20 sin 45 = 7.5N is equal
to vertical force WRV = WTtan ∅ sin 𝜃𝑝 7.5N.
Bending moment due to WRV & WRH M1 =WRV* over hung -WRH* Rm, over hung =500mm.
M1 =7.5*500- 7.5*33 =3502.Nmm. Bending moment due to WT
M2 =WT* Over hung =29* 500 =145000Nmm. Resultant bending moment m = √(m1²+m2²) =
14917Nmm. Since the shaft is subjected to twisting and bending moment it is nessaccery to calculate
equivalent twisting moment 𝑇𝑒 = √(𝑚² + T²) = 14947.6Nmm. Here we can calculate diameter
of internally hollow spilled shaft
𝜋𝐷³
𝑇𝑒 = τ , D³ = 16*14947.6/140π Where τ =140Mpa for cast iron.
16
D =∛2708.3 = 60mm.
I 30

3.15 Handle connecting the jacks

The hollow shaftsplined internally are connected to the solid worm shaft which is externally spliced the
outer diameter of hollow shaft is 60mm and to get the diameter of the hollow
Fig .3.6 spline
d =0.8D, d =0.8*60 =48mm
Taking b=5mm t= 5mm
Direction of threads on the nuts and solid shafts
The direction of nuts for two jacks must revolve in opposite direction because the right and left side bevel
gears rotate in opposite direction of the thread must be with respect to the direction of motion of the
bevel gears. Threads look like
Left side right side
Fig .3.7 threading system
3.16 Bearing selection

The bearing is used to support the worm shaft .the type of bearing is ball bearing and the selection is
based on the shaft diameter d =38mm
I 31

The appropriate bearing size for this shaft is
Bearing number Bore diameter mm Outside diameter Width

mm Mm
208
308 40 85 18
408
Fig. 3.8 support bearing
3.17 Selection of foot step bearing
10
Fig 3.9 Foot step bearing
3.18 Selected threads
Selection of threads of the nuts and solid screw shafts had is given a great care because of if we do not
select the appropriate type of threads for lifting of load, it will cause failure and damage. So that to avoid
thus problem square thread is selected.
I 32

Due to strength, efficiency and ability to eliminate radial component of force between the screwed solid
shafts and nuts square thread is the best, but others cannot fulfill thus property, so square thread is
suitable for our design to prevent failure.
P/2
Fig.3.10 Square thread
3.19 Working principle

The dual lifting car jack works when the person applies small torque to worm shaft or handle at the center
this rotation will be transmitted to the worm shaft though the bevel gears assembly and as worm rotates
the worm gears, rotates with the solid screwed shaft and the nuts will be lifted up and down with load step
by step.
3.20Lubricants
Lubricants may be gaseous liquid or solid.liguid or solid lubricants share the properties of low shear
strength and high compressive strength.liguid lubricants such as petroleum oil is essentially
incompressible at the levels of compressible stress encounter in bearing, but it readily shear lubricants can
also act as contaminants to the metal surface and coat them with monolayer’s of molecules that inhibit
adhesion even between compatible metal.
Liquid lubricants are the most commonly used and minerals oils the most common liguid.Grease are oil
mixed with soaps to form athicker,stricker lubricants used where liquids cannot be supplied to or retained
on the surface. Solid lubricants are used to in situations where liquids either cannot be kept on the
surfaces. Or lack some required properties such as high temperature resistance.Gaseaus lubricants are
used in special situations.Such as air bearings to obtain extremely low friction. Lubricants especially
liquids also remove heat from the interface. Lower bearing temperature reduces surface interactions and
wear.
3.21 Short summery of dual lifting car jack

The dual lifting car jack is the modified design of the single car jack. This jack is the combination of two
single mechanically operated car jack connected by a handle located at the mid of the two. And the lifting
mechanism works by a single handle. The modified design of this lifting mechanism is obliged from the
I 33

sack of problems seen in the company that is in Nyala motors Share Company in Bahir Dar branch .So
that based on the question of the company mechanics, we have designed this dual lifting car jack. The
modified design car jack has the following advantages over the single car jack;
A single person can maintain and service a vehicle with this jack. Because in a single lifting car jack
when one person is lifting the car with the jack another person has to insert the safety stand and then go to
the next wheel and so on. Thus as we see from this is tedious and power consuming.
In this mechanism of lifting car jack no need of safety stand because jack has two supports of the two
sides and can act as two safety stands. In this cause another person is not needed for inserting the safety
stands and only one person can work on this system.
It has high mechanical advantage because with small input torque. It can lift the whole car but in case
single car jack it lifts only at one wheel side of the car.
The distance between the two single jacks is not fixed.i.e adjustable so that it can lift the front and back
(rear) wheels at the same time.
I 34

Commented [h15]: By using the crop you should be editing like

shown below
Fig .3.11 assembly drawing
I 35

I 36

CHAPTER FOUR
4 OVER ALL BENEFITS WE GAINED FROM THE INTERNSHIP Commented [h16]: 4.

And check the guide book of the school when I gave u during
mentoring and the chapter not much the subtitle description then
4.1 parts of car and their function you should be revised the school guide for report writing
4.1.1 Parts of engine
Fig .4.1 engine
The main parts of engine are;
Cylinder head: this includes valves, valve guides, valve springs, valve cover, intake manifold,
exhaust manifold etc.
Cylinder block: this consists cylinder, piston, crank shaft, piston connecting rod, oil screener etc.
I 37

Crank case: this carries the oil pan and the lower part of the engine.
Piston rings: there two piston rings these are;
a) Oil ring: it keeps oil in the sump from leaking into the combustion area.
b) Compression rings: it consists two rings which prevent fuel air mixture and exhaust gas in the
combustion chamber from leaking to the sump during compression and combustion.
Cylinder: the core of the engine block in which the piston moves up and down.
Piston: cylindrical piece of metal that moves up and down in the cylinder.
Fig .4.2 piston assembly
Piston pin: a pin that attaches one end of the connecting rod to the piston.
Crank shaft: is the part of the engine which changes the reciprocating motion of the piston to rotary
motion.
Cam shaft: is the single most important component which controls the power characteristics of
engine. And its function is;
 Open intake and exhaust valves.

 Executing the fuel and oil pump.
I 38

Fig .4.3 cam shaft

 Timing operation.
Push rods: are used on an engine that has their camshafts inside the engine block. These rods are
designed simply to transfer motion from the camshaft to the rocker arms. As the camshaft turns, the cam
lobe pushes up on the valve lifters. The lifters transfer this motion to the pushrods. The pushrods, in
turn, transfer this motion from the block to the cylinder head. There they push on the rocker arms. The
rocker arms change the upward motion of the pushrods to a downward push on the valves.
Rocker arm:The main purpose of the rocker arm is to transmit the camshaft motion by pivoting
around its shaft to the valve stem. It pivoted at the center transmit the lifting of the camshaft directly to
the valve but in opposite direction. Usually rocker arms are located in pairs separated by a support
bracket. This pair of rocker arms is held apart by a spring, spacer tube.
Valves: The majority of engines have two valves for each cylinder, intake and exhaust valves. During
intake stroke, the valve permits the air fuel mixture or air alone to enter the cylinder. The exhaust valve
to let the exhaust gases leave the cylinder in the exhaust stroke. In the other two strokes, compression and
power strokes, both valves must tightly seal, with the closed valves, the valve face must fully contact the
seat.
Value guide: The valve stems rides in a hole in the cylinder head. This guide keeps the valve
properly aligned. It also keeps the valve from tilting and provides a way to transfer heat from the valve
stem to the cylinder head. Inaddition; the guide prevents excessive oil from interring to the combustion
chamber. To ensure this, the valve guides produce with a close tolerance to the valve stem. However,
there is a clearance between them so that the valve can slide freely up and down.
I 39

Valve seat: is the surface on which the valve comes to rest to have a tight seal. The valve seat can be
integral or replaceable. The contact area between the seat and the valve face provides a tight seal. The
valve seats also help cool the valves. The exhaust valves operate at high temperatures because they open
into the hot combustion chamber gases. These temperatures are so high that the valve will quickly burn
or crack unless they are kept properly cooled.
Valve spring: provides the force needed to close the valve. The ends are ground flat to apply an
evenly distributed pressure and helps the spring to stand square. This eliminates any tendency of the
spring to tilt the valve and cause wear in the guide. Usually one spring is used for each valve. In some
engine, two springs, one inside the other, are providing.
4.1.1 .1Classification of engines

As we have seen in the practical work engines are classified based on
 Type of fuel used

 Cooling system
 Number of cylinders
 Type of stroke
Type of fuel: based on the fuel they used engines can be diesel engine and gasoline (benzene)
A) Diesel engine: it works as follows. First air enters through the air sucker and then passes to the air
cleaner and then pass to the intake manifold then to the valves and it is sucked by the piston of the engine
and then compressed at this compression fuel is injected by injector nozzles .air heats up when it is
compressed, so that the fuel ignites and power developed and the exhaust gas pass through exhaust
manifold to the surrounding. As a result the crank shaft rotates and torque transmitted through flywheel
and clutch to the gear box and differential to wheels and then the vehicle can move.
The fuel transmission units in diesel engine
Fuel tank: is the storage unit of fuel.
Feed pump: used to suck the fuel from the tank and pass to the fuel filter.
I 40

There are two types of fuel filter this are primary and secondary filters. They are used to clean the fuel.
Injection pump: it pumps fuel into the cylinders of the diesel engine and to rise the fuel pressure, fuel
delivery in each cylinder in firing order of sequence.
Injector nozzle: it produces forceful energy by taking the fuel from the injection pump to the cylinder.
Return line: each injector nozzle has its own alignment which collects the left over fuel from the injector
nozzle and passes it to the tank.
Glow plug: heating device used to aid starting diesel engine.
Generally the fuel flow in diesel engines looks the following.
Primary Secondary Injection

Fuel tank Feed
pump fuel filter pump
Fuel filter
Engine Injection
nozzle
Left over fuel
Return line
Fig. fuel flow in diesel engine
B) Gasoline engine
The fuel transmission units of gasoline engine are same to diesel engine, except the following
which are found only in gasoline engine. These are;
I 41

Carburetor: it mixes the fuel with air as the air flows into the engine. Air and fuel are mixed
before entering the engine by the carburetor.
Throttle valves: these are rotating valves which control the flow of air fuel mixture from
carburetor to cylinder and thus the quantity of air fuel mixture that the system will deliver is by
regulating engine power and speed.
Choke: it is used to provide extra fuel to the carburetor.
4.1.1 .2Energy transformation in engine

The energy flow in engine is, first chemical energy Changed to heat energy
and then to mechanical energy.
Chemical Heat energy

Mechanical
energy Fuel mixed with ignition
energy
(fuel)
Compressed air
Cooling system: based on cooling system engines are classified as water cooled and air
cooled.
a) Water cooled engine: the cooling parts of water cooled engine are the following.
Radiator: it acts as a heat exchanger. it is design to transfer heat from the hot coolant that
flows in it to the air blown though it by the fun. the water enter to cap of radiator and the fun
keyed to the water pump shaft is used to cool the water and this cooled water go to the lower
hose (inlet) plastic pipe and enter to the engine through the thermostat and it will stay in the
engine until 74 ℃.Above this temperature the radiator will be opened and the hot water comes
back to radiator.
This type of cooling system is indirect cooling. Because first the fun cool the hot water in the
radiator and then the cooled water used to cool engine.
I 42

Radiator cap: radiator has two valves. These are;

A) Pressure valve: when the water in the cooling system heats up it expands causing
the pressure to build up. When the pressure reaches maximum point the pressure pushes the
valve open allowing the coolant to escape from the cooling system .This coolant flows
through the over flow tube in to the bottom of over flow tank.
B) Suction valve: when the radiator cools back down a vacuum is created in the cooling
system that pulls the over flowed water to radiator.
Thermostat: its main job is to allow the engine to heat up quickly and to keep the engine at
constant temperature, it does this by regulating the amount of water that goes through the
radiator .at low temperature the out let of radiator is completely blocked and the coolant
circulate in the engine.
Fan: used to maintain temperature of the engine by forced convection.
Water pump: used to circulate the coolant that the engine is running .the fluid leaving
the pump enter to the engine block and cylinder head then to the radiator finally back to the
pump.
Water jacket: hollows in the engine block which allows coolant circulation to prevent
engine overheating.
b) Air cooled engine: the engine block is covered with aluminum fins that conduct heat
away from the engine. A powerful fan forces air over these fins which cool the engine by
transferring the heat to air.
Safety measures for cooling system
 The cooling parts must be clean.

 Damaged parts must be replaced by new parts.
 Leaking parts must be checked and replaced.
Stroke type: based on the type of stroke engines can be two stroke or four stroke engine.
a) Two stroke model; it has no moving valves and the spark plugfires each time ,the
piston hits the top of its cycle a hole in the lower part of cylinder wall lets in fuel and air.
I 43

As the piston moves up it is compressed the spark plug ignites, combustion and exhaust
exits through another hole in the cylinder.
b) Four stroke model: with both valves closed the combination of the cylinders and the
combustion chamber form a completely closed vessel containing air fuel mixture.
Pairing and adjustment of valves in four stroke model:

Pairing of valves means the pair of pistons which will do the same function at the same time i.e.
piston which compresses at the same time, suck air the same time etc. to know the pairing of
cylinders we give number for each cylinder starting from the front as first ,second and third etc.
thus the way of deciding the pair is adding the numbers given for cylinders to give a summation
value of one greater than the number of cylinders . For example, for an engine having six
cylinders the pairs are; 1&6, 2&5, 3&4 and for engine having four cylinders the pairs are;
1 & 4, 2&3 and their firing orders are 15,36, 24 and 13, 42respectivly.
4.1.2 Braking System

There are two types of brakes in vehicles. These are disc brake and drum brake.
a)Disc brake: consists of two main parts: the disc, also called the rotor, and the caliper
assembly. The disc rotates with the wheel hub. The caliper, which straddles the disc, is held
stationary. In front wheel brakes the caliper is bolted to the steering knuckle, in rear-wheel
brakes the caliper is bolted to the axle flange. The caliper assembly includes a hydraulic cylinder,
piston & the brake.
With the brake in the released position, the pads are slightly clear of the disc, which rotates
between them. When the brake is applied, pressure from the master cylinder forces the pistons
against the pads, which are then forced against the disc. This produces a clamping action, which
slows or stops the disc.
When the brake is released, the pistons retract slightly to allow the pads to move away from the disc. The
pads have no return springs, but the pistons are returned slightly in their bores by the resilience of the
piston seals.
Components of disc brake
I 44

1. Brake discThe disc is usually shaped to fit the wheel hub to which it is bolted. . This is of
hollow construction, consisting of two flanges separated by fins.
2. Disc brake calipers
The typical disc brake caliper assembly has a caliper housing, one or more pistons seal on each
piston, adjust boot for each piston, and two brake pads.
The disc brake caliper may be fixed, sliding, or floating. but we had seen the fixed type .the fixed
caliper has piston on both sides of the caliper. The force of each piston is applied directly to a
brake pad. The reaction force of the caliper applies the out-side pad.
3. Disc pads
A disc pad consists of a steel backing plate with friction material bonded to it surface. The pad is
positioned by guide lugs that fit into slots in the caliper.
4 .Caliper Pistons
Caliper pistons have the piston seal mounted stationary in the housing and the piston in the seal.
Mounting the seal in this way produces the force to pull the released piston and pad away from
the rotor to reduce drag. This design provides "self-adjustment" to automatically maintain the
correct lining-to-rotor clearance.
5 .Piston Seals
. Fixed-caliper has the seal mounted on the piston and the seal slides on the cylinder bore. The
cylinder bore in these calipers must have a smooth surface finish for maximum seal life. The seal
does not move the piston back into the cylinder on release.
6 .Pad Wear Indicator
When pad thickness is reduced the pad wear indicator, fixed to the backing plate of the pad,
come into contact with the rotor disc and produces a screeching noise during driving.
I 45

b) Drum brakes
 Brakes not applied

Pistons inside the wheel cylinder are constantly pushed backward, via brake shoes, by the return spring.
They are pushed back to the strut touches the shoes.
The compression spring in the wheel cylinder is fitted so that piston and shoes will contact each other at
all time. This prevents unusual noise from the brakes.
 Brakes applied
When the brake pedal is depressed, hydraulic presser inside the master cylinders, forces shoes apart so
that they rub against the lining and stop the wheel rotation. The hydraulic pressure in the wheel cylinder
also acts on the lips of the piston cup. It pushes the lips against the cylinder and prevents from leaking.
I 46

Component of drum brake
Fig 4.4 parts of drum brake
1. Brake drum
It rotateswith wheel of the vehicle and provides a braking surface against which the brake linings operate
.The brake shoes are expanded inside the drum and so the drum must be capable of withstanding the force
applied by the brake shoes without distorting .The brake drum must be capable of absorbing the heat
produced by friction between the shoes to prevent excessively high temperatures developing in the brake
assembly
2. Backing plate
The backing plate for the front brake is mounted to the steering knuckle and the backing plate for the rear
brake is mounted to the axel flange. The backing plate carries all the stationary brake parts, which include
the wheel cylinders, brakes shoes, return springs, retaining spring, anchor and adjuster .It is not only acts
as a support for the brake shoes and associated parts, but also acts as a shield to exclude road dirt..
I 47

3. Brake linings
The brake shoes are shaped to fit the contour of the brake drum with which they are used .A shoe consists
of the web and the flange .The web is provided to stiffen the flange. The flange is fitted with a lining of
friction material, which is either riveted or bonded to it.
4. Brake springs
Springs are fitted to the brake shoes to locate the shoes on the backing plate. The return springs oppose
the action of the brake shoes when the brakes are applied and return the shoes to their normal position
when the brakes are released.
Retaining springs and clips are used to hold the brake shoes against the backing plate. Other springs are
used to locate the shoes in position or to hold the ends of the return springs.
4. Anchors
Anchors are used to locate the ends of the shoes by providing an abutment against which the shoes can
rest. Anchor pins are used to hold the ends of the return springs.
5. Adjusters
Various types of adjusters are used to adjust the working clearance between the brake shoes and the drum.
6 .Wheel cylinders
The wheel cylinder is bolted to the backing plate. It forms an anchor for one end of the shoe and expands
the shoes when the brakes are applied.
4.1.3 Clutch and flywheel

The clutch is located between the engine and the transmission/transaxle. An automotive clutch is used to
connect/engage and disconnect/disengage the engine and manual (hand-shifted) transmission or transaxle,
both starting up and during gear shifting. A friction type of clutch is used in motor vehicles with manually
operated transmission or transaxle.
I 48

Fig 4.5main part of car
A manual clutch works on the principle of friction. Its function depends upon sufficient friction being
developed between the contact surfaces of two or more members to transmit the desired torque.
COMPONENT CONSTRUCTION AND OPERATION:.
An engine clutch consists primarily of four parts:
1. Fly wheel
2. Friction/clutch disc
3. Pressure plate assembly and
4. Release/control mechanism
The Flywheel
The flywheel is a fairly large wheel that is connected to the crankshaft. The clutch assembly is mounted to
the flywheel, sandwiching the clutch disk in between. It also provides a friction surface to the clutch.The
clutch disc is clamped and held against the flywheel by the spring action of the pressure plate. The face of
the flywheel is precision machined to a smooth surface.
Friction/Clutch disc
the clutch disc, also called friction disc, consists of a splined hub and a round metal plate covered with
friction material (lining). The clutch disc friction materialalso called disc liningor facing, is made of heat-
resistant asbestos, cotton fibers, and copper wires woven or molded together. Grooves are cut into the
I 49

friction material to aid cooling and release of the clutch disc. Rivets are used to bond the friction material
to both sides of the metal body of the disc.
The splines in the center of the clutch disc mesh with the splines on the input shaft of the manual
transmission. This makes the input shaft and disc turn together. However, the disc is free to slide back and
forth on the shaft.
Pressure plate assembly with coil spring:
The main parts of a pressure plate assembly are:

Pressure plate cover
Pressure springs (coil springs)
Pressure plate
Release levers
Eye bolt Commented [h17]: Check the space between the lines
The pressure plate cover is bolted to the flywheel. Its main purpose is to hold the assembly together.
Holes around the outer edge of the cover are for bolting the pressure plate to the flywheel.
The pressure plate springs are pre compressed between the pressure plate and cover.
The face of the pressure plate is a large, flat ring that contacts the clutch disc during clutch engagement.
The release levers are hinged inside the pressure plate to pry on and move the pressure plate face away
from the clutch disc and flywheel.
The eye bolt (fulcrum point of the release lever) is screwed in to a flange nut, which is locked by the lock
nut. This arrangement provides the clutch release lever adjustment.
Clutch Fork
The clutch fork, also called a clutch arm or release arm, transfers motion from the release
mechanism to the release bearing and pressure plate. The clutch fork sticks through a square hole
in the bell housing and mounts on a pivot.
I 50

Body repair:
The body is the external parts of the vehicles. it is mostly done by welding. In the company body
repair is mainly performed by arc welding and oxy-Acetylene welding.
Metal welding methods

Welding is one method of repair in which heat is applied to the pieces of metal to fuse them together in to
the shape desired.
a) Arc welding. Pieces of metal are heated to the melting point Joined together with a filler rod,
and allowed to cool.
b) Oxy –Acetylene
Gas welding processes are so called because the welding heat is provided by a flame produced by the
combustion of a mixture of gasses. A variety of gasses are used commercially but an Oxy-acetylene
mixture is the most common because of its high flame temperature and because the gases are convenient
to handle.
To obtain the oxygen in a state that makes it usable for welding, it is necessary to separate it from the
other gasses. Oxygen is produced commercial either by the electrolyte process or by a separation method
known as the liquid air process.
Suspension system
The suspension system mainly consistsof:
Leaf spring, coil spring, shock absorber and wheels. Its basic purpose is to isolate the vehicles body from
unwanted vibration.
Leaf springs
Leas springs are made of a number of curved bands of spring steel, called “leaves”, stacked together in
order from shortest to longest. This stack of leaves is fastened together at the center with a center bolt or a
rivet. Also, to keep the leaves from slipping out of place, they are held at several places with clips. Both
I 51

ends of the longest (main) leaf are bent to form spring eyes, used to attach the spring to the frame or to a
structural member such as a side member.
Fig .4.6 leaf spring
Coil springs
Coil springs are made from rods of special spring steel formed into
the shape of a coil. When a load is placed on a coil spring, the entire
rod is twisted as the spring contracts. In this way, the energy of the
external force is stored, and shock is cushioned.
Fig 4.7 coil spring
Shock absorber (fluid damper)
A device that controls unwanted spring motion through the process known as fluid damping. It slows
down and reduces the magnitude of vibratory motion by changing kinetic energy of suspension movement
into heat energy that can be dissipated by the fluid.
I 52

Steering system
It is used to enable the driver to control the position of the front wheels. The basic parts of steering system
are;
Steering wheel: a hand wheel that is used for steering .it is the part of steering system that is
manipulated by the driver.
Steering shaft:transfer steering motion from the steering wheel to the steering gear box.
Steering gear box; serves two basic functions.
 It produces a large portion of the mechanical advantage required to provide easy and safe
steering.
 It provides convenient means of converting the turning motion of the steering wheel in to
back and forward motion required to operate the steering li
 Sector shaft
Receives energy from the steering gearbox and pass it to the tires though the tie rod and
control arms by makes the tires to turn left and right to the steering wheel direction.
Boll joint
A flexible coupling of a vehicles suspension that connects the control arm to the steering
knuckle. A boll joint is so named because of its boll and socket constrain.
Tie rod
It is used to connect the steering arms to the center link. Boll joint at each end provide the
necessary flexibility. The boll joints are threaded in to each end of the tie rod to provide a
means of adjusting.
I 53

4.1.4 Differential
Fig 4.8 differncial
Car differential
A differential is a device, usually, but not necessarily, employing gears, which is connected to
the outside world by three shafts, chains, or similar, through which it transmits torque and
rotation.
In automobiles and other wheeled vehicles, a differential is the usual way to allow the driving
roadwheels to rotate at different speeds. This is necessary when the vehicle turns, making the
wheel that is travelling around the outside of the turning curve roll farther and faster than the
other. If the engine is running at a constant speed, the rotational speed of each driving wheel can
vary, but the sum (or average) of the two wheels' speeds cannot change. An increase in the speed
of one wheel must be balanced by an equal decrease in the speed of the other. (If one wheel is
rotating backward, which is possible in very tight turns, its speed should be counted as negative.)
I 54

Power flow in vehicles
Engine Clutch Gear Drive Differen Axle

box shaft tial
Wheel
4.1.5 LUBRICATION SYSTEM:

The engine lubrication system supplies lubricating oil to all engine moving parts. The oil flows through
the oil gallery to lubricate the main bearings of the crankshaft, con rod bearings, camshaft bearings; valve
trains parts, piston, piston rings, piston pin, etc.
The lubrication oil flows up to the rocker arm and valve stems through hollow pushrods. And the main
bearings, connecting rod bearings, piston, piston rings, and piston pins are lubricated in the same way.
Lubrication is very necessary for satisfactory motor vehicle performance. It is only necessary to
provide minimum wear or low frictional losses between the adjacent moving surfaces, but it is also a
necessity for performing other jobs in the various moving parts of the motor vehicle. It is needed to
lubricate the moving parts for;
1) Minimizing the wear and the power loss due to friction.
2) Removing heat from the moving parts (using as a cooling agent by absorbing the heat from the
moving parts and by surrounding air through the oil pan or crankcase).
3) Absorbing shocks between bearings and other engine parts.
4) Forming a seal between piston rings and cylinder walls (to prevent compressed air escape to the oil
pan).
Electrical system: is generally classified in to four major parts.
I 55

Ignition system: its main function is to create the electrical spark in the engine combustion chamber at
exactly the right time in order to ignite the mixture. It is found only in gasoline engine.
Starting system: it consists of battery, ignition key, and starter motor.
Battery; is where the electric power begins to generate.it changes chemical energy to mechanical
energy.it consists of 35 percent of acid and 65 percent of distilled water.
Ignition key; isswitch helps to transfer electrical current from battery to startor motor and other
components.
Stator motor; used to start up the motor by charging electrical energy from battery to mechanical energy.
Charging system
Generator; a system of charging battery is driven by the engine crank shaft by belt and changes
mechanical energy to electrical energy and charges the battery and supplies to other parts.
Electric regulator; it limits the electrical force not to create damages.it regulates the electrical flow from
generator to battery, prevent over charging of battery.
Lighting system; consists of head and back lights, turn signal lights e t c.
Wiper motor; operates by changing the electrical energy to mechanical energy for washing the front
glass.
4.2 Parts of car to be maintained

Maintenance means the repairing of damaged (broken) parts by avoiding the broken or the non-functional
element from the vehicle and substituting by new. Thus the maintenance of a vehicle will be done, if car
I 56

as damaged by any accident or if it elements the vehicle works for a long period of time, there may be
non-functionality of parts which leads to the maintenance. The main parts of car to be maintained are;
 The engine
 Gear box
 Electrical parts
 Suspension system
 Body parts
 Differential etc.
Generally the whole part of car will be maintained if damaged.
4.3 parts of car to be serviced

Service means changing of oil or damaged parts at scheduled period of time .this service takes place at
specific kilometer scheduled by the designer of the parts. At the scheduled kilometer the parts are
assumed as they will loosen their proper functioning. Thus by reading the distance from the kilometer
gauge the service will be done. For example some of the services are;
From 5000 kilometers to 10,000 kilometers –wheel hub service.
From 10,000 kilometers to 60,000 kilometers-engine oil change.
From 20,000 kilometers to 40,000 kilometers –air cleaner change.
4.4 Clarity of theoretical knowledge that we know before

The internship plays a great role in increasing our understanding, theoretical knowledge that we have
learned in mechanical engineering courses. As we have seen in the practical work some of the
understandings we got from the internship are; how parts of a vehicle vibrate and the use of dampers to
decrease or to avoid the vibration, the reciprocating mechanisms and how they are changed to rotation i.e.
in piston reciprocation and crank shaft rotation, the cam mechanism and its application in timing
operation in engine firing and also the use of s-cam in pneumatic braking.
I 57

The balancing system and its application in wheel balance, the application areas of fasteners
(bolts,screws,rivets,snap rings, welding),lubricants and their multipurpose ,how the mechanical elements
(brake,clutch,belts,gears,keys,splinesetc.) work ,heat transfer and heat exchanger in water cooled engines
the radiator and fins in air cooled engines, the use of seals and gaskets .
Condenser and compressor in air conditioning system ,hydraulic and mechanical lifts, different types
of bearings and their application area, sensors and their application area ,fluid flow in pipes ,the
transformation of energy from one form to another which is the basic principle of vehicles movement ,it
is chemical energy is changed to heat energy and to mechanical energy.
The two types of welding (arc and carbo acetylene) welding, casting and pres work and their application
in vehicles body ,the types of fits and their application areas in cars, the electrical machines in vehicles
stator motor generator, the effects of friction and wear etc.
4.5 Increasing of problem solving techniques

From looking different practical works and the working mechanisms; we gained several problem solving
techniques. Such that we have designed modified mechanisms of existing mechanically operated bottle
car jack which is done as a project .it is designed after we have looked the working mechanism of
differential gears.
Also from looking the oil pump which is used to fill the gear box and differential oil, we have a plan to
design a water pump that can work mechanically. Therefore the internship helps us to develop our
industrial problem solving techniques.
4.6 Developing of team work and interpersonal communication

Since maintenance and service of vehicles is a team work, we have been working with many workers
together such that we have developed our team work and communication skill to others. Especially in
vehicles maintenance and service team work has a great role because the duties are huge and difficult to
operate by a single person. Our opinion to team work is changed, after we had worked in the internship
.for team work interpersonal communication has great value to do qualified work. As we have understood
from the internship, working in team has greater advantages than working individually because from
members’ team different ideas can be developed to solve any difficulties in the working area. In addition
vehicles maintenance and service needs high man power due to the presence of high weight of the
mechanical elements and this may damage for a single worker.
I 58

4.7 Respecting work ethics

In the period of internship we have understood that to work in both governmental and nongovernmental
companies respecting the work ethics is the main criteria of workers. Each worker respects the rules and
ethics of the company.
Also we interns have been respecting the work ethics .Someone who is out of the work ethics
will follow punishment .punctuality,loyality,integrity,taking responsibility ,respecting collogues
etc. are some of the work ethics.
4.8 Leadership skill

In addition to other skills we also developed our leadership skill from the managing ability of the
company’s manager and the director. The knowledge we gained for improving our leadership
ability are;
 Controlling and guiding workers wisely.
 Respecting and treating customers fairly.
 Follow up the working flow.
 Social interaction to people.
4.9 Development of Entrepreneurship Skill

Entrepreneurship is creating of new jobs based on problem. In the process of problem solving
basic things can be created as solution which can give job opportunity to money people. Thus
from the internship work we had seen the presence of money problems in a single company and
different company’s in Ethiopia there may be large number of problems.
In the company , we had given solutions for the basic problems by designing the tool which is
not present, such that from this we understood that if we continue this searching of problems and
giving solution, many new jobs will be created which leads to our country is development.
Generally from looking different problems, our entrepreneurship skill is developed.General
Safety Rules
I 59

4.10 Work Shop Safety

Safety means protecting oneself from possible danger and injuring in the shop, you are ' Safe' when you
protect your eyes, your fingers, your hands all of yourself from danger as well as others.
Hazards in the work shop

a) Faulty work habits
b) Misuse of equipment
c) Misuse of hand tool)
Faulty work habits
i) Smoking around fuel and solvents
ii) Incorrect handling of paint, thinners, solvents, flammable liquids etc..
iii) Blocking exits. A block exit could mean serious injury or even death during an
emergency case such as fire.
b) Misuse of equipment’s
Incorrect safety guarding of moving machinery

i) Misuse of flexible electric cords or worn cords. When used through holes the may cause
fire
ii) Improperly stored composed gas cylinders
iii) Using hand held electric tools improperly grounded
C) Misuse of hand tools
i) Keeping hand tools dirty and in poor conditions

ii) Improper storing of hand tools
iii) Using defective hand tools
iv) Keeping sharp tools in pockets
Fire Prevention
i) Store fuels properly
ii) Keep the shop doors open, will ventilation where fuel vapors can exit
iii) Wipe up the spilled fuel at once and keep the rags in a closed waste containers
iv) Never smoke or light a cigarette around fuels. ( Do not smoke in the workshops!)
v) Fix leaking carburetors, fuel pumps fuel lone and fuel tank immediately
I 60

vi) Make fine extinguishers available in the workshop and know perfectly well how to use
them in case of fire
Personal Safety
Most of the dangers for an auto mechanic involve a running parts, road tests, etc.
A) Working on Vehicles
i) Fan on vehicles
 Never stand around the fan when an engine is being run
 Keep hands, rags and clothes away from the moving fan beat.
ii) Ignition high voltage circuit
 So not grab the spark plug cables with your bare hand when the engine is running
iii) Carburetors and fuel lines
 Never look in to the carburetor throat when starting or running an engine
 Never use an open can of gas to prime carburetors
 If you replace any part of the fuel system, do not drive the car for road test before you
crank the engine for a while and check for any leaks
IV) Radiator when the engine is hot, take care of removing the radiator cap
V) Manifold and Exhausts
 Always treat the radiator and manifolds as if they were hot

 Be sure to connect the exhaust tube to the engine exhaust before running the engine
in the shop.
Vi) The hood
 Always drop the hood open with an " iron stick" when working on an engine
Vii) Welding
 Always wear goggles while you are welding

 While welding a fuel tank drain it, and full it with mater or below it out with a
compressed air
I 61

Viii) Road test
It is best to have two men in the car during a road test. One does the testing the other watches the road
b) Working switch chemicals

i) Fire:-
 Know where the fire extinguishers and fire exits are:-
 Do not get in to confined area with a carbon tetrachloride type extinguishers
ii) Oil and other lubricants
 Make sure that there are no oil leakage on your working area
iii) Battery acid
 Do not smoke around a battery being charged. It gives off hydrogen which is
extremely explosive.
 Avoid battery acid from setting in to your eyes or touching your skin.
 When mixing acid always pour slowly the acid in to the water the reverse mixing
procedure may cause the mixture to boil and spatter with the force of apparent
explosion.
c) Working on power tools
 The instruction for using any equipment should be studied carefully before the
equipment is operated
 Hands and clothes should be kept away from the running machineries
 Disconnect the power source when you stop working on machines
 Clean, lubricate and cover the machine every time you finish working
 Never get under a vehicle which is standing on a jack. Support it with car stands and
chock the wheels to keep the car from rolling
I 62

Chapter five
5 Recommendation
1. Provide safety shoes and wear to every employer based on their buy sections Commented [h18]: Chapter five and six are one chapter
Conclusion and Recommendation
2. We advise them to employ atrained mechanics in order to reduce power losses, life transition system,
big time losses such as easily movable use system mechanism.
3. We advise them replacing man power partially by modern system such as simple machine.
4. Reducing coast out.
5. Improve combination work in every section and increasing workers.
6. The workers in the company are very kind beginning to the manager up to the watch men.
I 63

Chapter six
6 Conclusion
Nyala Motors Share Company Bahir Dar branchensures big advantage to the public services and with
better efficiency, quality with a short period of time. It also increases the manufacturing capacityof Nissan
Company of Japan spare parts required for maintenance and service activity. In addition to that the
company has well experienced workers those can maintain and service vehicles as the
customers’interest.
Internship practice has vital role in improving our practical skill and clarity of theoretical knowledge. It
also helps us to develop our interpersonal communication skill, respecting work ethics, team work,
entrepreneurship skill, professional skill and leadership skill.
I 64

References
 Nyala Motors S.C 40𝑡ℎ years anniversary magazine.
 R. S Kurmi and Gupta text book of machine design 2002 G.C.
 Manual of automotive mechanics.
 Internet at www.automotive engineering.
 Practical work of Nyala Motors S.C.
I 65

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SCHOOL OF MECHANICAL&INDUSTRIAL ENGINEERING

NYALA MOTORS S.C BAHIR DAR BRANCH

Mr. KINDU WONDEM

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

Partial View of Nyala Motors S.C Bahir Dar Branch

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

C. E .O –Chief executive officer

NMSC - Nyala Motors Share Company

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

3.11 Design of worm and worm gear ..................................................................................................... 26

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

Chapter six .................................................................................................................................................. 64

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

1.1 Brief History ofNyala Motors Share Company (NMSC)

UD TRUCK (heavy duty)

All light vehicle Nissans (especially model)

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

1.2 vision, mission, values and objective of the company

Our motto is safety and quality comes first.

Working towards customers’ satisfaction

Main objective of the Company:

According to by the law of the company the main objectives are;

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

 To carry out any business connected with the above objectives.

1.3 It’s over all organization structure

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

ShortHistory of Nyala Motors S.C Bahir Dar branch

Organizational structure by chart

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

Director of Director of Director of Director of

Service Branches Spare

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

2. over all Intern ship Experience

2.1 Why Do We Select The Company?

2.2 Section of the Company We Have Been Working

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

2.2.1 Layout of the Company

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

2.3 The Work Flow in the Working Section

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

Director assigns workers

Customers come with their vehicles

And ask the director

2.4 Tasks that we have Been Executing

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

2.5Mechanical Engineering Methods and Tools for Executing Tasks

2.5. 1 The Most Important Hand Tools are the following

Fig .2.1 open wrench

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

Fig 2.2 closed wrech

PREPARED BY: FIKIR G. HENOK B. MELKAMU Z. 2006 E.C

Fig .2.3 combination wrench

Pliers (pinesaps); used t grip different size of materials.