THE DESIGN AND FABRICATION OF MECHANCIAL LAWN MOWER

CHAPTER ONE

INTRODUCTION

          In the past, cutting of grasses in the schools, sports track, or field, industries hotels, pubic center, etc was done by cutlass this method of manual cutting is time consuming a s it is human effort that is needed for cutting, there was also inaccuracy in cutting level using the manual cutting system.

          Apart from all these old method of cutting there is also risk of accident.

          The problems of the manual was meant to be overcome with the aid of this project (the construction of a mechanical lawn mower) which is used for cutting of grasses to equal height or level for speedy cutting.

          This project lawn mower, is also the accident free as well, it reduced labour and also reduced number personnel that is needed in a particular operation, it also reduced man power as it an internal combustion engineer that dose the actual cutting while the operator provides the efforts, great portion of land can easily be cut with lawn mower.

          Again to encourage beauty in our environment this project was embarked on to help in keeping our environment clean because most labourers are finding it difficult in handily tool for gasses cutting.  It is also used for cutting sports field, (like foot ball pitch as well as crowns in hotel and business premises so this project reduces human effort and should be encouraged in school, hotel, business area, etc although mowers can be of electric type too, but we decided to fabricate a mechanical type to overcome the problem of electricity and as such this our lawn mower can be used every where even were there is no electricity.

IDENTIFICATION OF NEED

          Early before now, West Africa as a whole, the peasant farmer depends on the hoe and cutlass for practically all farm operation.  There tools vary in shape and size from place to place in the high forest zone of Nigeria the small farmer must clear thick bush every three or four years.  All this job is being done either hoe or cutlass for weeding of farm land.  These farm operation depend entirely on the energy of the farmer using the tools which he has at this disposal.   This inability that facing the farmer, has triggered these project group to research into the lasting solution to the problem.

          Also, with meant development in the country, daily labour in farm operation is highly exorbitant for the farmer to afford but with these project (mechanical lawn mower) this problem of high payment of local labour can lead to reduction importation cost from Germany USA of this machine Nigerian with high profitability to the farmers.

1. 1. LITERATURE REVIEW

1. 1. HISTORICAL BACKGROUND OF THE PROJECT (SCOPE)

Based on the developing countries, technology in farm operation is highly increased.  It is clear that developments in farm machinery in West Africa started far back 1960.  This project must related to the social and ecological condition prevailing in different parts of this great region at the present time two trends a re apparent.

1. 1. Increase in the use of tractors and large agricultural machinery of farms of large extent both in the high forest and savanna zones, but particularly in the latter.

1. 1. The increased use of animal power and small machines on peasant farms operation in West Africa will become increasingly mechanized, and that stage of mechanization mechanized, and that stage of mechanization which lies between the hoe and cutlass on one hand and the tractor combine harvester on the other is referred to as intermediate technology.

1.4     IMPORTANCE OF THE PROJECT TO SOCEITY  

          Generally this project (mechanical lawn mower) has a great effect towards development and maintenance of any community in the societies which one nominated below.

1. 1. Cutting grass of secondary primary and tertiary field thereby reducing human effort needed.

1. 1. Great portion of farmland can easily cut or brushed with lawn mower in one day.

1. 1. This project reduced number of personnel that needed in a particular farm operation.

1. 1. To reduce manpower

1. 1. To improve the economy of the country

1. 1. Provisions of foreign exchange in the country

1. 1. t reduce importation cost t o our country (Nigeria)

1. 1. It encourage pupils, and student to be regular and the school because no more cutting of grass with cutlass by pupils or students.

1.5     AIMS AND OBJECTIVES OF THE PROJECT

          In the past, several investigation w ere made in the lawn mower industry at USA, Germany etc. Nigerian market, from which this production is a development of already existing ones.  It was localized to smite our environments condition aim and objectives of the investigation on the project are nominated below.

1.5.1  REDUCTION OF LABOUR COST

          In application of lawn mower machine in any government field and farm land causes seriously reduction in number of labour needed in the maintenance of the yard, brushing and clearing of the grass but with aid of lawn mower machine, the job is easily performed without much wasting of time.  This project IMT can get the yard well cutted and cleared.

1.5.2  IMPROVEMENT OF FOOD PRODUCTION

          Local farmer can embark on maintenance of 100 hectares of farm land with aid of lawn mower machine.  This project will extract some lazy farmer to embark on farming operation, also many people will developed interest and rendering agricultural engineering or course related to farm.

1.5.3  TIME FACTOR

          The production of this project (lawn mower machine) brings reduction in man hour consumed in cutting of grass which is being improved using lawn  mower machine which employed some minute of an how for  the job.

1. 1. 1. IMPROVEMENT IN ECONOMY.

Having farmer embark on large farm land for production of food to the citizen birth aid of lawn mower machine but not hand tools is bound so produce supply enough quantities food to market which extract improvement of country and also ensure stability and the foreign exchange.  Also boosting of employment to the youth of the town.

CHAPTER TWO

SPECIFICATON OF PROBLEM

          A simple mechanically hand pushed lawn mower is used for cutting of grass and clearing of light bush.

SCOPE OF SPECIFICATION

          Metric unit were used throughout

CONDITION OF USE

          The mower is fabricated to be used in cutting even stubborn grass, etc, but stones should be avoided during operation.  It is advised that the body is washed with water and the blade sharpened after use to avoid rusting and encourage fast and smooth cutting the oil level of the engine should be checked and roped with oil if the oil levels falls after period the oil should be change with a new one.

          Before starting the engine, make sure that the blade is well tightened after which you cover the grass exist the unit as the engine is in operation; use only petrol the fuel tank.

          Because the engine will be vibrating the entire body as well as the wheels and handle, it is advisable to check the units and bits and tightened than well after each operation.  After which the engine should be stored in a moist free and fire room.

CHARACTERISTICS

          The overall mass of the lawn mower should not exceed 25kg.  The handle carried the engine firing regulator the level of cutting varies from 2cm to 7cm and is achieve by varying the wheels. The blade rotation should be parallel to the ground and it cuts tangentially.

          The blade cuts any grass that enters the blade.

PERFORMANCE

          The lawn mower has a maximum cutting force of 77N and is advisable to cut maximum force of 70N efficiency of the mower is ……………………………

APEARANCE

          The mower looks like a small car with curved edges.  The shape is to create room for the blade and is also for beauty the wheels and tyres are for easy.  Movement and is attached to the body through roller bearing/bolt.  The body covers the blades to avoid accidental cutting of any person.

RELIABILITY AND LIFE

          The life of the cutter depends on doing work as well as rate of filing.  The engine life depends on number of hours worked.  Therefore, the full loading capacity for 12 hours per day year operation should not be less than 10 years.

SYNTHESIS OF SOLUTIONS

          In producing a lawn mower of this size and shape.  Three alternative are likely considerable.  Viz (I) manually operation lawn mower, (2) electrically operation lawn mower and (3) mechanically operation type.

          The conceptualization of these three solutions above lead us to studying their simplicity of the layout case of manufacture/purchase operation efficiency, cost of producing, ease maintenance etc.

THEORY AND ANALYSIS PROBLEMS

          The lawn mower cutting grass by using rotational motion of the engine to create a centripetal force on the blade hits the grass at a tangent and cut it.  The centripetal force (ft) is defined as the inward force required to keep an object moving with a constant speed in a circular path.  This centripetal force (ft) is given by mve/t m = mass of object (mass of blade) V = uniform velocity, R = Circular path or radius blade.

                Now the power utilized during this cutting is produced by an (.1 on the four stroke cycle of a petrol engine and our own is a single cylinder four stroke cycle internal combustion engine which are (1) induction (2) compression (3) power and exhaust stroke. In the process, the crank shaft rotate making the piston to move downward from the TDC making the exhaust port to close and allowing the inlet port to open by introducing air fuel mixture to enter the combustion chamber at B0C the inlet port close, the cylinder, than the piston now rises again and compresses the air fuel mixtures piston approaches the TOC both ports are closed, the compressed gas is ignited by a spark plug, than piston is forced down the cylinder by the piston risks up and push the exhaust gas out through the outlet port as the piston approaches the TDC the outlet close and the piston once again commence the cycle.  The engine carried its stroke by the energy stored in the flywheel.

CALCULATION INVOLVED

Centripetal force Ft = Mv2/t v = 3/t = r0/t = r0/t but W = 0/t

W            =              2TIN radius

                                                60

V             =              Wr

DETERMINATION OF TORQUE THAT DEVELOPED FROM THE WORKING STROKE OF THE ENGINE

                From the formula show below

                P              =              Tw

Given that W = 3600 rpm, P = 3.5 HP by the manufacture but hp =   7 4b watt or IN/S

                If hp = 746 watt

                3.5 hp      =              P (watt)

P (watt)   =              3.5 x 7.46                                =              2611 watt

3.5hp       =              2611 watt

Torque developed by the engine

                F              =              P              N/M          =                 Power Produce 

                                                M                                            Angular speed engine

Where      W            =              2TIN

                                                                  60

W            =              2 x TI x 3,600         =              377.04rods

                                                60

T              =              P              (N/M)      =                  Power developed

                                W                                                            No of revolution produce

T              =              2611                        =              6.92 N/M

                                377.04

Torque produced (T) = 6.92 N/M

2.4           DETERMINATION FO THE CUTTING FORCE OF THE BLADE (F) =

                Torque produced in engine

                Diameter of the blade

F              =              6.92 N/M

                                0.1812M

F              =              2 x 6.92

                                   0.18

Cutting for (F) = 77N(w)

1. 1. DETERMINATION OF CUTTING SPEED OF THE BLADE SHOWN BELOW

Cutting speed (cs) – No of  rev.x circumference of the blade

                                                                                1000

=              No of rev. x circumference of the blade /100c

Cs            =              Nx d/1000               =              3.600 x 0.18

                                                                                                                100

Cutting speed (cs) = 2.0mls

1. 1. TO DETERMINATION OF THE MINIMUM OF CIRCULAR SHAFT THE WILL TRAMS MITI A TORQUE OF 6.92 N/M WITH MAXIMUM SHEAR STRESS OF 6 MPA

d3            =                16T                            16 x torque produced         

                                11 max    II x maximum shear stress

d3            =              16 x 6.92

                                3.142 x 6

d3            =              5.873

                                3.5873

d              =              1.8m = maximum diameter of shear of shaft weed to carried torque of 6.92 N/M.