MANUFACTURING OF SOLAR GRASS CUTTER

MAIN PROJECT REPORT

Submitted in partial fulfillment of the requirement for the award of degree

of

Bachelor of Technology

in

Mechanical Engineering

Submitted by REGISTRATION NO.

JATINDER KUMAR 11205556

ABHISHEK THAKUR 11211886

RAVINDER SINGH 11201247

RAHUL KASHYAP 11202570

GROUP CODE 230

Under the esteemed guidance of

Mr. Vikas Rathore B.tech M.tech

SCHOOL OF MECHANICAL ENGINEERING

LOVELY PROFESSIONAL UNIVERSITY PHAGWARA

INDEX

Chapter 1 - INTRODUCTION

Chapter 2 - DESIGN

Chapter 3 - SELECTION AND MOUNTING

Chapter 4 - THEORATICAL ANALYSIS

Chapter 5 - RESULTS

ABSTRACT

The design objective is to come up with a mower that is portable, durable, easy to operate and

maintain. It also aims to design a self-powered mower of electrical source; a cordless electric

lawn mower. The heart of the machine is a battery-powered dc electric motor. It comprises of a

system of speed multiplication pulleys which drive the cutting blades and the charging unit

comprising of a 12V alternator and a lift mechanism meant to alter the height of cut. This is

achieved by means of a system of v-belt pulleys with minimal slip effect; collapsible blades to

reduce the common problem of wear. The use of collapsible blades and incorporation of an

alternator for recharging the battery make the design unique such that no engine is involved.

Performance test gave a cutting efficiency of 89.55% with 0.24kN human effort. Thus, the

machine is considered highly efficient and is readily adaptable to different cutting conditions.

THE BASIC IDEA

An electric Lawn mower There are so many complication with Electric Lawn mower Like

Electricity, Wiring,

Efficiency, Ecofriendly etc. And design is so complicated so behalf of Electric lawn mower we

have made Solar power grass cutter which is efficient ,less noisy,No need of any external

wiring.

The basic idea is that we have made grass cutter with electric motor that runs from a 12 volt

battery. This battery will be charged using solar panel of 5W.

CHAPTER 1

INTRODUCTION

Nowadays pollution is a major issue for whole world. Pollution is manmade and can be

seen in own homes. In case Gas powered lawn mowers due to the emission of gases it is

responsible for pollution. Also the cost of fuel is increasing hence it is not efficient. So the Solar

powered lawn cutters are introduced. Solar powered lawn mower can be described as the

application of solar energy to power an electric motor which in turn rotates a blade which does

the mowing of a lawn. Solar energy is the renewable energy.

Grass cutter or lawn mowing with a standard motor powered lawn mower is an

inconvenience, and no one takes pleasure in it. Cutting grass cannot be easily accomplished by

elderly, younger, or disabled people. Motor powered push lawn mowers and riding lawn

mowers create noise pollution due to the loud engine, and local air pollution due to the

combustion in the engine. Also, a motor powered engine requires periodic maintenance such as

changing the engine oil. Even though electric lawn mowers are environmentally friendly, they

too can be an inconvenience. Along with motor powered lawn mowers, electric lawn mowers

are also hazardous and cannot be easily used by all. Also, if the electric lawn mower is corded,

mowing could prove to be problematic and dangerous. The self-propelling electric remote

control lawn mower is a lawn mower that has remote control capability. This prototype is

robotic user friendly, cost efficient, safe to use, efficient to use, and environmentally friendly. It

can save significantly on labor costs.

TYPES OF LAWN MOWERS

Commercial mower

In the 1850s, Thomas Green & Son of Leeds introduced a mower called the SilensMessor

(meaning silent cutter), which used a chain to transmit power from the rear roller to the cutting

cylinder. These machines were lighter and quieter than the gear driven machines that preceded

them, although they were slightly more expensive. The rise in popularity of lawn sports helped

prompt the spread of the invention. Lawn mowers became a more efficient alternative to the

scythe and domesticated grazing animals.

2.Rotary lawn mower

Rotary mowers were not developed until engines were small enough and powerful

enough to run the blades at sufficient speed. Many people experimented with rotary blade

mowers in the late 1920s and early 1930s, and Power Specialties Ltd. introduced a gasoline-

powered rotary mower. KutKwick replaced the saw blade of the "Pulp Saw" with a double-

edged blade and a cutter deck, converting the "Pulp Saw" into the first ever out-front rotary

mower.

One company that produced rotary mowers commercially was the Australian Victa

company, starting in 1952. Its mowers were lighter and easier to use than similar ones that had

come before. The first Victa mowers were made at Mort lake, an inner suburb of Sydney, by

local resident Mervyn Victor Richardson. He made his first model out of scrap in his garage and

then moved to a shed behind St Mary's Church of England, where the first Victa mowers were

manufactured, going on sale on 20 September 1952. The new company, Victa Mowers Pty Ltd,

was incorporated on 13 February 1953.

3.CYLINDER LAWN MOWERS

Cylinder lawn mowers consist of a cylinder and a number of horizontal blades that spiral

around it. If adjusted to the correct height a cylinder mower will give the best cut of any lawn

mower. They are however, best suited to flat lawns and can be difficult to use on bumpy or tall

grass.

3.1 THE MAIN PARTS OF A CYLINDER REEL MOWER

Blade reel cylinder consist of numerous (3 to 7) spiral blades that are attached to a

rotating shaft. The blades rotate, creating a scissor-like cutting motion.

Bed knife is the stationary cutting mechanism of a cylinder/reel mower. This is a fixed

horizontal blade that is mounted to the frame of the mower.

Body frame the main structural frame of the mower onto which the other parts of the

mower are mounted.

Wheels these help propel the mower in action. Generally, reel mowers have two

wheels.

Push handles the "power source" of a manually operated reel mower. This is a sturdy T-

shape handle that is connected to the frame, wheels and blade chamber.

Motor the power source of a reel mower that is powered by gasoline or electric

4. PETROL LAWN MOWERS

These lawn mowers fall under the rotary type mowers. They are powered by internal

combustion engines. Such engines can be either two-stroke or four-stroke cycle engines, running on

gasoline or other liquid fuels. Internal combustion engines used with lawn mowers normally have only

one cylinder. Power generally ranges from two to seven horsepower (1.5 to 5.25 kW).

Petrol lawn mowers come in both the 2 stroke and 4 stroke cycle engines;

2 stroke lawn mowers are more powerful, less expensive, have a better power to weight

ratio, and can be operated in any orientation. However, they are also louder, less fuel

efficient, and do not last as long due to the high revolving engine. They also require the

petrol to be mixed with oil prior to use in order to lubricate the engine.

4 stroke lawn mowers by comparison are not as powerful, but contain an oil sump (a

separate oil chamber) and don't need the fuel to be pre-mixed. This saves the operator

from mixing the fuel but it also means that the mower cannot be tipped. On one side as it

will cause the oil to fall out of the sump into the fuel chamber.

5. HOVER LAWN MOWERS

Hover mowers are powered rotary push mowers that use a turbine above the spinning blades to

drive air downwards, thereby creating an air cushion that lifts the mower off the ground like a

hovercraft. The operator can then easily move the mower as it floats over the grass.

Hover mowers can also be applied to very long grass and even light scrub, since their lightness

permits most operators to lift the mower up and then let it sink slowly down while the blades

progressively chop up the vegetation.

4 Hover Lawn Mowers

The lifting action is made even easier when the mower is swung around with the handle held

against the operator's mid-body to provide leverage. The action of air lifting the mower off the grass

makes it hover a few centimeters above the ground thus making it very easy to push around the garden

and, providing that you are not interested in getting stripe.

6. ELECTRIC LAWN MOWERS

Rotary mowers powered by electric motors are increasingly popular. Usually, these

mowers are moved by manual motive power the on-board engine or motor only spins the

blades. These have the disadvantage of requiring a trailing power cord that limits its range and

so these are only useful for relatively small lawns, close to a power socket.

There is the obvious hazard with these machines of mowing over the power cable,

which stops the mower and may put users at risk of electrocution.

7.SOLAR POWER LAWN MOWER

A sloar grass cutter is machine that used rotary blades to cut a lawn at even length.even more

sophisticated devices are there in every field.power consumption becomes essential for future.

Solar grass cutter consists of solar panel of 5w that charge the battery using charge controller.

Solar powered lawn mower

CHAPTER 2

DESIGN

DESIGN CONCEPT

All component which has used to design solar power lawn mower written following

Component fig 1.1 grass cutter specification/features

Mild steel Rods To make frame of grass cutter

Battery 12V battery

DC motor 12VDC

Electrical circuit (resistance,capacitor) Bridge type resistance

Blades 6 TPI saw

3 wheels wheels

Fig

Drawing of

lawn

mower.

battery

Fig.1.3Orthographic View of the Mower

Fig 1.4 circuit daigram

2.1 Description

The lawn mower is made up by DC motor,battery and blades Speed of blade shaft is increased

by an arrangement of a speed multiplication pulley system mounted on a steel platform. At

once only one thing can work Charging battery or Motor .The DC motor forms The heart of

machine and provide the Power to blade To cut the grass.

This is achieved by the combined effect of

mechanical action of cutting blade and forward thrust of mower. The system is powered by an

electrical switch which complete the circuit comprising the DC motor and battery.

we have made frame with three wheels ,2

In back and 1 front, front wheel will give direction to mower from handle .

Bridge

circuit DC motor

Solar

panel

The main components of the solar powered grass cutter

Solar panel

Brush less DC motor

Mechanism used

Circuit breaker

Blades

Battery

SOLAR PANEL

Solar panel refers to a panel designed to absorb the sun's rays as a source of energy for

generating electricity or heating.

Solar modules use light energy (photons) from the sun to generate electricity through

the photovoltaic effect. The majority of modules usewafer-based crystalline silicon cells or thin-

film cells based on cadmium telluride or silicon. The structural (load carrying) member of a

module can either be the top layer or the back layer. Cells must also be protected from

mechanical damage and moisture. Most solar modules are rigid, but semi-flexible ones are

available, based on thin-film cells.

Specification of solar panel

solar panel - Solar Panel PV Cell- 12V 5watt with aluminum body free

Key Features:

Nominal Power - Pmax ( Watts ) Nominal 3.3

Open circuit Voltage - Voc ( Volts ) 12v

Short Circuit Current - Isc ( Amps ) 0.42

Solar Cells per Modules - Unit 18 (9x2 Matrix)

Dimensions - ( L x W x T ) mm 185 x 200 x 22

Weight - Kgs 0.5

DC MOTOR

An electric motor is a machine which converts electrical energy into mechanical energy.

Principle:

It is based on the principle that when a current-carrying conductor is placed in a magnetic

field, it experiences a mechanical force whose direction is given by Fleming's Left-hand rule and

whose magnitude is given by

�� � = ��� ��

Where B is magnetic field in w/m2

I is current in amp,L is length of coil in meter

DC motor 12V

Torque of DC motor is given by

� = �� sin �

Where F=force on linear direction

R is radius of object being operate

Theta is angle The force is making with R vector

Brush

A brushed DC electric motor generating torque from DC power supply by using internal

mechanical commutation, space stationary permanent magnets form the stator field.

Advantages of a brushed DC motor include low initial cost, high reliability, and simple control of

motor speed.

Disadvantages are high maintenance and low life-span for high intensity uses. Maintenance

involves regularly replacing the carbon brushes and springs which carry the electric current, as

well as cleaning or replacing the commentator. These components are necessary for

transferring electrical power from outside the motor to the spinning wire windings of the rotor

inside the motor. Brushes consist of conductors.

The brushed electric motor generates torque directly from DC power supplied to the

motor by using internal commutation, stationary magnets and rotating electrical magnets.Like

all electric motors or generators, torque is produced by the principle of Lorentz force, which

states that any current-carrying conductor placed within an external magnetic field experiences

a torque or force known as Lorentz force. Advantages of a brushed DC motor include low initial

cost, high reliability, and simple control of motor speed. Disadvantages are high maintenance

and low life-span for high intensity uses.

Maintenance involves regularly replacing the brushes and springs which carry the

electric current, as well as cleaning or replacing the commentator These components are

necessary for transferring electrical power from outside the motor to the spinning wire

windings of the rotor inside the motor. Brushes are made of conductors.

Brushless

Typical brushless DC motors use a rotating permanent magnet in the rotor, and

stationary electrical current/coil magnets on the motor housing for the rotor, but the

symmetrical opposite is also possible. A motor controller converts DC to AC .This design is

simpler than that of brushed motors because it eliminates the complication of transferring

power from outside the motor to the spinning rotor.

Advantages of brushless motors include long life span, little or no maintenance, and high

efficiency. Disadvantages include high initial cost, and more complicated motor speed

controllers. Some such brushless motors are sometimes referred to as "synchronous motors"

although they have no external power supply to be synchronized with, as would be the case

with normal AC synchronous motors.

5.8.1 HOMOPOLAR MOTOR

A homopolar motor has a magnetic field along the axis of rotation and an electric

current that at some point is not parallel to the magnetic field. The name homopolar refers to

the absence of polarity change. Homopolar motors necessarily have a single-turn coil, which

limits them to very low voltages. This has restricted the practical application of this type of

motor.

.

Fig:5.8.1Homopolar Motor

5.8.2 BALL BEARING MOTOR

A ball bearing motor is an unusual electric motor that consists of two ball bearing-type

bearings, with the inner races mounted on a common conductive shaft, and the outer races

connected to a high current, low voltage power supply. An alternative construction fits the

outer races inside a metal tube, while the inner races are mounted on a shaft with a non-

conductive section (e.g. two sleeves on an insulating rod).

This method has the advantage that the tube will act as a flywheel. The direction of

rotation is determined by the initial spin which is usually required to get it going.

BLADES

We have used saw blade for cutting grass ,blades are attached with motor when motor

rotating blade will rotate .

In our project we have used 6 inch metal blade which cut grass very smoothly.

This tough saw can be a remodeler's best friend, rapidly chewing through demanding

demolition tasks. A 6-inch blade with six teeth per inch (TPI) is a good choice for most jobs

because it combines ample capacity with fast cutting and ample rigidity. For demolition jobs, it

pays to buy good-quality blades that will slice through nails without complaint. For jobs where

you're attacking thicker material, move to a longer blade such as a 9-incher. Like the shorter

version, this blade also has six teeth per inch.

A blade with 10 TPI will yield a smoother surface, but you'll rarely use a reciprocating saw for

finished cuts. For metal cutting, select a blade that's engineered to handle the job. Choose a

blade with 18 to 24 TPI, depending on the thickness of the metal -- the thinner the stock, the

more teeth

blade used

BATTERY

A rechargeable battery, storage battery, secondary cell, or accumulator is a type of electrical

battery which can be charged, discharged into a load, and recharged many times,

The active components in a secondary cell are the chemicals that make up the positive and

negative active materials, and the electrolyte. The positive and negative are made up of

different materials, with the positive exhibiting a reduction potential and the negative having

an oxidation potential. The sum of these potentials is the standard cell potential or voltage.

12V battery

ELECTRICAL CIRCUIT

Project needed electrical circuit to charge the battery and to transmit power to motor, That all

done by capacitor, resistor diode etc.

In This we have used Wheat stone bridge electrical resistance system

This is actual circuit diagram using in project

ELECTRICAL CIRCUITS

Function of wheat stone bridge circuit

For measuring accurately any electrical resistance Wheatstone bridge is widely used. There are

two known resistors, one variable resistor and one unknown resistor connected in bridge form

as shown below. By adjusting the variable resistor the current through the Galvanometer is

made zero. When the current through the galvanometer becomes zero, the ratio of two known

resistors is exactly equal to the ratio of adjusted value of variable resistance and the value of

unknown resistance. In this way the value of unknown electrical resistance can easily be

measured by using a Wheatstone Bridge.

Wheatstone Bridge Theory

The general arrangement of Wheatstone bridge circuit is shown in the figure below. It is a four

arms bridge circuit where arm AB, BC, CD and AD are consisting of electrical resistances P, Q, S

and R respectively. Among these resistances P and Q are known fixed electrical resistances and

these two arms are referred as ratio arms. An accurate and sensitive Galvanometer is

connected between the terminals B and D through a switch S2. The voltage source of this

Wheatstone bridge is connected to the terminals A and C via a switch S1 as shown. A variable

resistor S is connected between point C and D. The potential at point D can be varied by

adjusting the value of variable resistor. Suppose current I1 and current I2 are flowing through

the paths ABC and ADC respectively. If we vary the electrical resistance value of arm CD the

value of current I2 will also be varied as the voltage across A and C is fixed. If we continue to

adjust the variable resistance one situation may comes when voltage drop across the resistor S

that is I2.S is becomes exactly equal to voltage drop across resistor Q that is I1.Q. Thus the

potential at point B becomes equal to the potential at point D hence potential difference

between these two points is zero hence current through galvanometer is nil. Then the

deflection in the galvanometer is nil when the switch S2 is closed.

What is p-n junction semiconductor diode?

A p-n junction diode is two-terminal or two-electrode semiconductor device, which allows the

electric current in only one direction while blocks the electric current in opposite or reverse

direction. If the diode is forward biased, it allows the electric current flow. On the other hand, if

the diode is reverse biased, it blocks the electric current flow. P-N junction semiconductor

diode is also called as p-n junction semiconductor device.

In n-type semiconductors, free electrons are the majority charge carriers whereas in p-type

semiconductors, holes are the majority charge carriers. When the n-type semiconductor is

joined with the p-type semiconductor, a p-n junction is formed. The p-n junction, which is

formed when the p-type and n-type semiconductors are joined, is called as p-n junction diode.

Operation Principle

Electrical energy of the battery is converted to mechanical energy through a set of blades

designed to achieve cutting operation. The electric circuit ensures power transfer from the

battery to run the D.C. motor, The cutting blades tap power from the D.C. motor. When the

power switch is on, the electrical energy from the battery powers the motor which in turn

actuates both the blades . The rotating blades continuously cut the grass as the mower is

propelled forward .

DESIGN

Theory

The shearing force most annual and perennial grass found

On most lawn is usually between 9.2N to 11N.

Force required by cutting blade to shear the grass is given by

F =T/R

Where T= shaft torque R= radius of blade

But shaft torque is given by � = �/2��

Where P =power developed by shaft

T= torque required

N=speed in Rpm

To figure out how long it takes to charge the battery I use this calculation

(Amp Hour Rating * 100of charge needed / Amps) * 1.25 = hours of charge time)

TOTAL HOURS TO GET FULL CHARGE

(7AH*1)/0.57)*1.25= 15 hours of charge time

CHAPTER 3

SELECTION AND MOUNTING

Selection of Electric Motor

For smooth grass cutting, a motor power of not less than 628.3W (0.84hp) having a rotational speed of not less than 3,000 rev/min and producing a shear force of about 10.5 N is recommended However, due to non availability of wide range of DC motors in the market, a 1¼ hp (932.5 W) having a rotational speed of 2,500 rev/min was used. Though this gives a sufficient torque with a high cutting force, using an average blade radius of 210 mm, the speed is still not sufficient enough for easy grass cutting.

Mounting the motor

When mounting the motor to the mower deck the most important thing was to make sure it

was centered and properly secured. I made sure it was centered by measuring an equal

distance from the sides of the motor to the outside diameter of the mower. I secured the motor

to the deck with welding joint on specific height from the surface .It is mounted below the

frame so it is not seen from the top.

This method of battery mounting is working out well. I have had no issues. Mounting the blade

Mounting the blade is very difficult task for us but we tried so many ways after so many ways

we choose one way to mount blade on motor shaft .we mount blade on motor with welding.

Mounting the battery

Once the motor was mounted I needed to find a place for the battery to sit. As I mentioned in

the mounting the motor section, the base of the motor was facing the rear of the mower and

would provide a solid mounting surface for the battery mount. To get the proper weight

distribution I wanted to mount the battery as close as I could to the back wheels. This would

allow the handle bars to serve as a lever and allow the mower to easily pivot when on its back

wheels.

Using a piece of stainless steel I purchased from a local scrap yard I fabricated the battery

mount. I started by placing the battery in the center of the square piece of stainless steel. Then

I marked the outline of the battery on to the steel. Next I cut the corners to allow the sides that

extend beyond the battery to be folded up. After folding up all four sides I welded them

together for support. The battery fits tightly into the mount so no excess strapping is needed.

Mounting the blade

Mounting the battery

CHAPTER 4

THEORATICAL ANALYSIS

Material and Methods

The cutting blade, the force required to cut the lawn as well as the force acting on the

blade was considered. The force required by any sharp object to have impact on the grass is

less than 10 Newton.

It is also dependent on the height, density and the area covered by the

object. Therefore, in designing the blade of the solar powered lawn mower, the force required

for effective mowing should be greater than 10 Newton. A stainless steel was used in the

construction of the cutting blade because of its strength and weight which can transmit same

speed as that of the DC motor or a little less cause of friction.

Mass of Blade

The area of the blade = length × width

Mass of the blade = density × volume

The density of a stainless steel is 7922kg/m

= 7922 × 1800 × 10-9

= 0.014kg.

Weight And Torque on the cutting blade

The weight of the blade, W = Mg

Where, M = mass of the blade = 0.014kg

g = acceleration due to gravity = 9.8 m/s2

Therefore, W = Mg

= 0.014 × 9.81

= 0.14N

Hence, the torque produce by the blade is given by

T = Wr

Where, W is the weight

r is the radius of the blade

r = 450/2 = 255mm

Therefore, T = Wr

= 0.14 × 225

= 31.5Nm

CALCULATIONS AND RESULT

P = πNT6 watts

P = power

N = Speed of motor

T = Torque

Then P=V*I

V=voltage

I=current

TORQUE AND POWER OF A MOTOR WITH NO LOAD CONDITIONS :

P=V*I

=12*25 =300W

N= 800 RPM

Then

P = πNT6 300=2∗π∗800∗T60

8 = *π*8 *T

T=3.58N-m

TORQUE AND POWER OF A MOTOR WITH LOAD CONDITIONS :

P=V*I

=12*29 =348W

N=600 RPM

Then

P = πNT6 348=2∗π∗600∗T60

88 = *π*6 *T T=5.53 N-m

Mechanical arrangement In the first phase we just considered only about the mechanical arrangements, which is

responsible for rotating the dynamo. For this the team members divided the work into two

divisions. The mechanical arrangement consisting of

External framework

Solar frame

External Framework

The external frame work is having 20/15 inches .There are four pairs of cylindrical

hollow pipes are welded as pillars, which will give the support for the surface of the platform.

Solar framework

The solar frame having the iron cylindrical hollow pipes are welded in square shape

which is used to carry the solar panel. The solar panel is 5watts which is connected to the

battery.

CHAPTER 5

RESULT

WORKING OF SOLAR GRASS CUTTER

The solar powered grass cutter was manufactured and developed. The solar energy is

generated due to solar panel and the energy is stored in battery , which converts the solar

energy into the electrical energy. The blade with dc motor connected to the battery. This solar

grass cutter cut all types of grass. The Test was carried out using four species of grass and the

CONCLUSION

PROJECT GOAL

Our project entitled Manufacturing of solar powered grass cutter is successfully

completed and the results obtained are satisfactory. It will be easier for the people who are

going to take the project for the further modifications. This project is more suitable for a

common man as it is having much more advantages i.e, no fuel cost, no pollution and no fuel

residue, less wear and tear because of less number of moving components and this can be

operated by using solar energy. This will give much more physical exercise to the people and

can be easily handled. This system is having facility of charging the batteries while the solar

powered grass cutter is in motion. So it is much more suitable for grass cutting also. The same

thing can be operated in night time also, as there is a facility to charge these batteries in day

light.

The mechanism which we used ie scotch yoke mechanism does not given excepted

efficiency. This efficiency can be increased by using some other mechanism. and speed of

motor is reduce because we have used heavy material and this material can be replaced by

using light weight material .and design of blades should be done based on types of grass is used

to cut. The project which we have done surly reaches the average families because the grass

can be trimmed with minimum cost and with minimum time Finally this project may give an

inspiration to the people who can modify and can obtain better results.

REFERENCES

http://www.appropedia.org/Solar_Charged_Lawnmower

Agarwal M.P, Solar Energy, S.Chand& Company Ltd, New Delhi IJAEEE,Volume1,Number 1 Nor Fatima al.ISSN:2319-1112 /V1N1:9-14 ©IJAEEE Mukherjee, D.,

Chakrabarti, S., Fundamentals ofrenewable energy systems, New Age international limited publishers,

New Delhi, 2005