A tractor is an engineering vehicle specifically designed to deliver a high tractive effort (or torque) at slow speeds, for the purposes of hauling a trailer or machinery used in agriculture or construction. Most commonly, the term is used to describe a farm vehicle that provides the power and traction to mechanize agricultural tasks, especially (and originally) tillage, but nowadays a great variety of tasks. Agricultural implements 0may be towed behind or mounted on the tractor, and the tractor may also provide a source of power if the implement is mechanised. The word Tractor is derived prior to 1900, the Machine were known as traction motor (pulling-machine).After the year 1900 both the words are joined by taking ‘Tract’ from Traction and ‘Tor” from motor calling it a Tractor. In our Country tractors were started manufacturing in real sense after independence and at present we are self-sufficient in meeting demand of country’s requirement for tractors. Our country is basically an agricultural country where 75% of our population is directly or indirectly connected with agriculture. This cannot be produced with our conventional bullock pulled agricultural implements. Tractor is one of the basic agricultural machines used for speeding up agriculture production.

1. SOKOINE UNIVERSITY OF AGRICULTURE
COLLEGE OFAGRICULTURE
DEPARTMENT OF ENGINEERING SCIENCE AND TECHNOLOGY
DEGREE PROGRAM: BSc. AGRICULTURAL ENGINEERING
COURSE NAME: FARM POWER AND MECHANIZATION
COURSE ANTE: AE 215
GROUP 01: TRACTOR
INSTRUCTOR: Mr. PROCHES
SUBMISSION DATE: 15th
May, 2018

2. S/N NAME REG NO DUTY SIGN
1 LIBENA, FREDRICK AGE/J/2016/0182 Power Tiller
2 FAUSTINE, FOCUS AGE/J/2016/0143 Bio-fuels
3 MAGANGA, BURTON AGE/E/2016/0422 Component of
Tractor
4 MICHAEL, ALOYCE
PETER
AGE/J/2016/0127 Tractor
classification and
selection
5 MOSHA, HILLARY P AGE/J/2016/0150 Tractor
classification and
selection
6 NYANJALI, WILSON
MICHAEL
AGE/D/2016/0393 Tractor engine
performance
7 SHIJA, DEUS HERIBERT AGE/J/2016/0149 Mechanics of
tractor Chassis
8 IDDI, RAMADHAN
ATHUMAN
AGE/J/2016/0164 Power Tiller
9 MAPUNDA, FREDY J AGE/D/2016/0379 Tractor
components
10 MUSHAMBA, DIANA
MWEMEZI
AGE./D/2016/0391 Maintenance and
safety
11 ALEX, ERIC AGE/E/2016/0413 Component of
Tractor
12 DEUS ,FELICIAN AGE/J/2016/0131 Mechanics of tractor
chassis
13 KIHONGOSI, LAWRENCE W AGE/D/2016/0369 Tractor engine
performance
14 ELIESKIA , ESTER FADHILI AGE/D/2016/0364 Uses of Tractor
15 MICHAEL, EDWARD AGE/J/2016/0133 Traction and
Traction Theory
16 ALBERT, GENEROZA AGE/J/2016/0242 Introduction
17 NZIKU, DEVOTHA F AGE/D/2016/0394 Maintenance and
safety
18 SAWE,TUMAINI J AGE/D/2016/0401 Bio-fuels
19 ZACHARIA, SOSOMA AGE/D/2016/0408 Traction and
Traction Theory
20 SANGA, AYUBU KERIOTH AGE/D/2016/0399 Traction and
traction theory

3. 3
TABLE OF CONTENT
TABLE OF CONTENT.................................................................................................................. 3
INTRODUCTION TO TRACTORS.............................................................................................. 1
CLASSIFICATION AND SELECTION OF TRACTORS............................................................ 2
TRACTOR COMPONENTS.......................................................................................................... 4
TRACTOR ENGINE PERFORMANCE ..................................................................................... 14
ENGINE PERFORMANCE......................................................................................................... 15
MECHANICS OF TRACTOR CHASSIS.................................................................................... 19
TRACTION AND TRACTOR THEORY.................................................................................... 21
TRACTION THEORY ................................................................................................................. 22
TRACTOR SAFETY.................................................................................................................... 24
TRACTOR TESTING .................................................................................................................. 29
TRACTOR MAINTENANCE...................................................................................................... 29
SEVERAL USES OF FARM POWER TRACTORS .................................................................. 29
POWER TILLER.......................................................................................................................... 31
DESCRIPTION OF ENGINE POWERED BY ALCOHOL AND VEGETABLE OIL (BIO-
FUEL). .......................................................................................................................................... 35
EXAMPLE OF THE ENGINE USING VEGETABLE OIL ....................................................... 39
REFERENCES ............................................................................................................................. 41

4. 1
INTRODUCTION TO TRACTORS
A tractor is an engineering vehicle specifically designed to deliver a high tractive effort (or
torque) at slow speeds, for the purposes of hauling a trailer or machinery used in agriculture or
construction. Most commonly, the term is used to describe a farm vehicle that provides the
power and traction to mechanize agricultural tasks, especially (and originally) tillage, but
nowadays a great variety of tasks. Agricultural implements 0may be towed behind or mounted
on the tractor, and the tractor may also provide a source of power if the implement is
mechanised.
The word Tractor is derived prior to 1900, the Machine were known as traction motor (pulling-
machine).After the year 1900 both the words are joined by taking ‘Tract’ from Traction and
‘Tor” from motor calling it a Tractor.
In our Country tractors were started manufacturing in real sense after independence and at
present we are self-sufficient in meeting demand of country’s requirement for tractors. Our
country is basically an agricultural country where 75% of our population is directly or indirectly
connected with agriculture. This cannot be produced with our conventional bullock pulled
agricultural implements. Tractor is one of the basic agricultural machines
used for speeding up agriculture production.
In the UK, the Republic of Ireland, Australia, India, Spain, Argentina, Slovenia, Serbia, Croatia,
and Germany, the word "tractor" usually means "farm tractor", and the use of the word "tractor"
to mean other types of vehicles is familiar to the vehicle trade, but unfamiliar to much of the
general public. In Canada and the USA, the word may also refer to the road tractor portion of a
tractor trailer truck, but also usually refers to the piece of farm equipment
Tractors can be generally classified by number of axles or wheels, with main categories of two-
wheel tractors (single-axle tractors) and four-wheel tractors (two-axle tractors); more axles are
possible but uncommon. Among four-wheel tractors (two-axle tractors), most are two-wheel
drive (usually at the rear); but many are two-wheel drive with front wheel assist, four-wheel
drive (often with articulated steering), or track tractors (with steel or rubber tracks).

5. 2
The classic farm tractor is a simple open vehicle, with two very large driving wheels on an axle
below and slightly behind a single seat (the seat and steering wheel consequently are in the
center), and the engine in front of the driver, with two steerable wheels below the engine
compartment. This basic design has remained unchanged for a number of years, but enclosed
cabs are fitted on almost all modern models, for reasons of operator safety and comfort. In some
localities with heavy or wet soils, notably in the Central Valley of California, the "Caterpillar" or
"crawler" type of tracked tractor became popular in the 1930s, due to superior traction and
flotation. These were usually maneuverer through the use of turning brake pedals and separate
track clutches operated by levers rather than a steering wheel.
CLASSIFICATION AND SELECTION OF TRACTORS.
Classification of tractors.
There are three classes of tractors;
(i) Wheel tractor:
Tractors, having three or four pneumatic wheels are called wheel tractors. Four wheel
tractors are most popular in performing different farm activities such as tillage, weeding and
harvesting. They are fast running speed and are not performing construction activities.
Furthermore can be subdivided into either two wheel tractors or four wheel tractors this
division is based on the power transmitted by the engine to the wheels Example of companies
producing wheel tractors are Massey Ferguson and John deer.
(ii) Crawler tractor:
This is also called track tractor. This type of tractor are chain type, in such tractors there is
endless chain or track in place of pneumatic wheels, this kind of tractors are specifically
designated to perform in areas where pneumatic tyres cannot pass such as mountainous and
juggles areas and normally these machines have high horse power and one of the most
usefulness of this tractor is in construction activities. Example of these tractors are excavators
(iii) Power tiller:
Power tiller is a walking type tractor. This tractor usually fitted with two wheels only. The
operator, walking behind the tractor performs the direction of travel or in other type of power
tiller the driver may control this device while sitting.

6. 3
On the basis of purpose, wheeled tractor is classified into three groups.
i) General purpose tractor:
It is used for major farm operations such as ploughing, harrowing, sowing, harvesting and
transporting work. Such tractors are characterized by having Low ground clearance,
increased engine power, good adhesion and wide tyres to lower the pressure that will help to
avoid compaction of the soil during operation.
ii) Row crop tractor:
It is used for furrowing crop cultivation. Such tractor is provided with replaceable driving
wheels of different tread widths. It has high ground clearance to save damage of crops. Wide
wheel track can be adjusted to suit inter row distance.
iii) Special purpose tractor
It is used for definite jobs like cotton field, marshy land, hill sides, garden, industrial, earth-
moving tractors etc. Special designs are there for special purpose tractor.
iv) Orchard tractors:
These are special type of tractors, are mainly used in orchards. These tractors have big height
so that while sitting on the tractor the driver can easily pluck the fruit or the trees can easily
be trimmed. There is no part of this machine outside the surface and allows easy passage in
between the trees. Such tractors have
 Less weight
 Less width and
 No projected parts.
Selection of tractors.
 Land holding: Under a single cropping pattern, it is normally recommended to consider 1
hp for every 2 hectares of land. In other words, one tractor of 20-25 hp is suitable for 40
hectares farm.
 Cropping pattern: Generally 1.5 hectare/hp has been recommended where adequate
irrigation facilities are available and more than and crop is taken. So a 30-35 hp tractor is
suitable for 40 hectares farm.
 Soil condition: A tractor with less wheel base, higher ground clearance and low overall
weight may work successfully in higher soil but it will not be able to give sufficient depth
in black cotton soil.

7. 4
 Climatic condition: For very hot zone and desert area, air cooled engines are preferred
over water-cooled engines. Similarly for higher altitude, air cooled engines are preferred
because water is liable to be frozen at higher altitude.
 Repairing facilities: It should be ensured that the tractor to be purchased has a dealer at
nearby place with all the technical skills for repair and maintenance of machine.
 Running cost: Tractors with less specific fuel consumption should be preferred over
others so that running cost may be less.
 Initial cost and resale value: While keeping the resale value in mind, the initial cost
should not be very high, otherwise higher amount of interest will have to be paid.
Test report: Test report of tractors released from farm machinery testing stations should be
consulted for guidance.
TRACTOR COMPONENTS
Due to the development of technology makes tractors to be digitals (the tractor which uses
electronics systems to operates) or analogy (tractors which uses manuals components for
operations).
Tractor components refers to basics components that makes tractor to operate.
The following are main components of Tractors:
(i) I. C. engine
(ii) Clutch
(iii) Transmission gears
(iv) Differential unit
(v) Final drive
(vi) Rear wheels
(vii) Front wheels
(viii) Steering mechanism
(ix) Hydraulic control and hitch system
(x) Brakes
(xi) Power take-off unit
(xii) Tractor pulley and
(xiii) Control panel.
Note: Every tractor is fitted with an I. C. engine, the engine may be carburettor type or diesel
type but nowadays almost all the tractors are diesel tractors.

8. 5
(i) Internal combustion engine(I.C.engines)
I.C engines refers; to engines that creates energy by burning fuel inside itself. The engine
of tractor is the main chief component that drives the tractors to work in all activities in
farms.
I.C engines are classified according to the following;
 Ignition system
 Number of strokes
 Internal combustion
 Fuel systems.
(ii) Clutch
Clutch is a device, used to connect and disconnect the tractor engine from the
transmission gears and drive wheels. Clutch transmits power by means of friction
between driving members and driven members

9. 6
Types of clutch Clutches
Clutches are mainly of three types these are;
 Friction clutch
Friction clutch is most popular in four wheel tractors, Friction clutch may be
subdivided into three classes:
(a) Single plate or single disc clutches
(b) Multiple plate clutches or multiple disc clutch
(c) Cone clutch.
 Dog clutch. Mostly used in power tillers.
 Fluid coupling, is also used in some tractors these days.
(iii) Transmission gears
Gears are used to reduce the engine speed as the rear wheels of the tractor require power to low
speed and high torque. Speed varies according to the field requirements and so a number of gear
ratios are provided to suit the varying conditions. Gears are usually made of alloy steel. As the
tractor has to transmit heavy torque all the time, best quality lubricants, free from sediments, grit,
alkali, moisture, is used for lubrication purpose. SAE 90 oil is generally recommended for gear
box.

10. 7
Common gears used on tractor are of two (2) types, these are;
a. Selective sliding type
b. Constant mesh type
(iv) Differential unit
Differential unit is a special arrangement of gears to permit one of the rear wheels of the tractor
to rotate slower or faster than the other. While turning the tractor on a curved path, the inner
wheel has to travel lesser distance than the outer wheel. The inner wheel requires lesser power
than the outer wheel, this condition is fulfilled by differential unit, which permits one of the rear
wheels of the tractor to move faster than the other at the turning point. The output shaft coming
from the gear box is provided with a bevel pinion at the end of the shaft. The Bevel pinion is in
mesh with a large bevel wheel known as crown wheel.
The main functions of crown wheel assembly are
To transmit power through right angle drive to suit the tractor wheels.
To reduce the speed of rotation.
The differential unit consists of:
(a) Differential casing;
(b) Differential pinions;
(c) Crown wheel:
(d) Half shaft and
(e) Bevel gear

11. 8
Diagram showing differential unit
(v) Final drive
Final drive is a gear reduction unit in the power trains between the differential and the drive
wheels. Final drive transmits the power finally to the rear axle and the wheels. The tractor rear
wheels are not directly attached to the half shafts but the drive is taken through a pair of spur
gears. Each half shaft terminates in a small gear which meshes with a large gear called bull gear.
The bull gear is mounted on the shaft, carrying the tractor rear wheel. The device for final speed
reduction, suitable for tractor rear wheels in known as final drive mechanism

12. 9
(vi) Steering mechanism (system)
This system governs the angular movement of front wheels of a tractor, it minimizes the efforts
of the operator in turning the front wheel with the application of leverages. The different
components of this system are: (i) steering wheel; (ii) steering shaft; (iii)steering gear; (iv)
pitman arm: (v) drag link; (vi) steering arm; (vii) tie rod and (viii) king pin

13. 10
vii)Hydraulic control and hitch system
Hydraulic system
This is the mechanism in a tractor to raise, hold, lower the mounted or semi mounted equipment
by hydraulic means. All tractors are equipped with hydraulic control system for operating three
point hitch or the tractor.
Components of the hydraulic system are;
Reservoir, Pump, Relief valve, Control valve, Cylinder, Filter or strainer
viii) Hitch system

14. 11
This is the mechanism where the tractor implements or equipments can be towed or pulled
through the tractive power of the engine via drawbar or power take off system, the hitching
system consists of drawbar and three point hitches or quick hitches.
ix) Brakes
Brake is used to stop or slow down the motion of a tractor. It is mounted on the driving axle and
operated by two independent pedals. Each pedal can be operated independently to assist the
turning of tractor during the field work or locked together by means of a lock.
Principle of Operation.
Brake works on the principle of friction. When a moving element is brought into contact with a
stationary element, the motion of the moving element is affected. This is the due to frictional
force which acts in opposite direction of the motion and converts the kinetic energy into heat
energy.
Classification of Brake.
Brakes can be classified as:
(i) Mechanical brake and
-Internal expanding shoe type
- External contracting shoe type
-Disc type.
(ii) Hydraulic brake.

15. 12
x) Power Take off Shaft (P.T.O Shaft)
Power take off shaft usually known as P.T.O shaft. In now-a-days a standard fitting on
all tractors and is used for running rotator, fertilizer spreader, duster, sprinkler and many
more machines which are stationary such as: threshers, water pump, portable flour mill
etc.
These shafts either run on 540 or 1000 rpm old standard (1938) specified speed of 540
rpm and number of P.T.O shaft splines was 6 in number. While the new standard has
specified 21 splendid P.T.O shaft running at 1000 rpm with new generation high
performance machine it was necessary for more speed. But we have lots of old tractors
having 540rpm P.T.O shaft while the equipment now available is for 1000rpm.

16. 13
xi) Rear wheels and Front wheel
Rear wheels
The rear wheel s of the tractor are large in size compared to the front wheels , the
rear wheels they receive power from the engine and trapped to the differential units
which make the rear wheels to work independently so the rear wheels are the one
which provide the traction power that moves the tractor back and forth, and when
cornering the outer wheel rotate faster than the inner wheel.
Front wheels. The front wheel of the tractor are small in size compared to the rear
wheels.
Diagram showing both rear and from wheel of John Deere Tractor

17. 14
TRACTOR ENGINE PERFORMANCE
Is the machine that convert energy from heat energy to mechanical energy.
Also can be defined as powerful motor-driven vehicle with large heavy treads, used for pulling
farm machinery to work, it uses energy from liquid fuel/steam to produce movement.
Types of tractor engines
Tractor engines are classified according to the type of fuel used to power the engine and so we
have;
(i) Steam powered tractor engine
This is a machine that burn goal to release the heat energy. It’s a bit like grant kettle
sitting on top of a coal fire. The heat from the fire boils the water in the kettle and turns it
into steam but instead of blowing off uselessly into air, like the steam from the kettle, the
steam is captured and used to power machine. The steam create high amount of pressure,
this pressure is then sent into cylinders which are used to move the wheel and mechanical
farm implement.

18. 15
(ii) Gasoline powered tractor engine
Tractors using gasoline engines were developed not long after their steam counterparts.
Gasoline engine fuel and air is injected into small metal cylinders. A piston compresses
the mixture making it explosive and a small electric spark from a sparking plug sets to it
that makes the mixture explode, generating power that pushes the piston down the
cylinder and turns the wheels. The fuel injector ensures that the fuel is broken down into
small droplets and that is distributed evenly. The heat of the compressed air vaporized
fuel from the surface of the droplets. The vapor is then ignited by the heat from
compressed air in the combustion chamber, the droplets continue to vaporize from their
surface and burn getting smaller until all the fuel in droplet has been burnt. Combustion
occurs at a substantially constant pressure during the initial part of the power stroke. The
start of vaporization causes a delay before ignition and the characteristics diesel knocking
sound as the vapor reaches ignition temperature and causes as abrupt increases in
pressure above the piston. When combustion is complete the combustion gas.
(iii) Diesel powered tractor engine
These are generally powered by large diesel engine which are particularly good at
providing high pulling power at very low speed.
It is the type of internal combustion engine (I.C.E)
Internal combustion engine is simply one where fuel is burned inside in the main part of
the engine (cylinders) where power is produced. That’s why internal combustion engines
are more energy than the same volume of fuel.
Diesel tractors are able to operate on bio-diesel fuel meaning that they can grow their
own plant fuel and use it directly in these machines.
Diesel machines are usually simpler than the gasoline and use air heated under
compression in cylinders to Ignite fuel without use of spark plugs.
ENGINE PERFORMANCE
The engine performance is measured by power output, economy, durability and emission. They
can as well be summarized as input and output which are
 Output; transmitted in rotational form and hence measured in terms of torque as
rotational effort (N.m) and speed as rotational motion (rad/sec).the torque will be
represented by the way the torque load is applied the engine varies with the speed.

19. 16
 Input; is in the form of fuel metered into the air by the carburetor during its passage to
cylinder (diesel) and air drawn into the engine acting as pump.
The maximum output of the engine is effectively determined by the maximum input, the limiting
factor being the quantity of air (charge) drawn into the cylinder on each stroke. This in turn will
depend on:
(i) The size of the cylinders
(ii) The restriction offered by the air passages, valves, etc
(iii) The time available for the air to be drawn in.
For a given engine at high speed, the time available for the air to enter the cylinders is so short
that the air charge is reduced and at low speed, the time available for the air to enter the cylinders
is longer but heating of the air in the cylinder reduces the charge. Hence, for a given engine,
there is an optimum speed at which most air is drawn in; at both higher and lower speeds, less air
enters.
Because the output (torque) from the engine depends on input (air), the maximum output
(torque) coincides approximately with maximum air charge .More fuel will give slightly greater
output torque, but most of the extra fuel will be wasted and will appear as black, un-burnt carbon
in the exhaust gas.

20. 17
The types of engine which are commonly used in our country are the fuel type engines which are
also part of the combustion engine. The combustion engines are categorized into two mainly
types external combustion engines and the internal combustion engine; whereby the fuel type
engine are in the external combustion engine category. Combustion engines also vary based on
the type of fuel they burn.
 Gasoline is a liquid fuel derived from petroleum (crude oil). Grades of gasoline differ based
on octane rating (premium or "leaded" vs. regular or "unleaded"). Higher octane gasoline can
withstand more compression before combustion, and is needed in some engines
designed for higher compression to prevent knocking (uncontrolled combustion in the
cylinder). Gasoline engines are also called spark ignition engines, meaning the fuel is burned
by generating a spark from a spark plug in the cylinder.
 Diesel is a liquid fuel made of long hydrocarbons derived from crude oil. Diesel has a high
energy density and thus has better fuel economy (over 33% more efficient) than gasoline, but
burns more dirty. Ultra-low sulfur diesel (ULSD) is a standard for diesel with low sulfur
content; most grades of diesel fuel used today are ULSD. Diesel engines are compression
ignition engines, meaning the fuel is burned by using compressed (high pressure) air to raise
the temperature beyond the self-ignition (auto-ignition) point of the fuel. Because they do not
use an ignition source (spark), diesel engines often require warming up under very cold
conditions before use. Diesel engines also provide more torque than gasoline engines.

21. 18
TRACTOR ENGINE WITH LABELLED PARTS
SECTION VIEW OF AN ENGINE

22. 19
MECHANICS OF TRACTOR CHASSIS
Chassis is the base frame of a farm tractor on which all the components and assemblies like
Engine, Transmission, Tires, Front Axle, Steering Systems and Electrical Systems are attached.
So, the overall structure which binds all these components together in a tractor is called tractor
chassis. It is built very strong to bear the heavy lad and shocks received while working on the
farms.
Functions of Tractor Chassis Frame
The various functions of tractor chassis are listed below:
• The load of assemblies like engine, transmission, steering etc is aptly supported by chassis
frame design.
• The rear and front wheels are connected to each other using tractor chassis.
• The load of implements is also carried easily by this frame.
• The working on an uneven field normally causes more load production. This extra load is
managed by the frame efficiently.
• The load incurred when tractor is working on the field along with an implement is also
managed by this frame.
• The load produced by sudden application of brakes or acceleration is also managed.
• The cornering forces are nicely negotiated by these frames.
Types of Tractor Chassis Frames
These frames are divided into 2 types of categories. These divisions are listed below:
(i) Chassis less Tractor
(ii) Tractor having Chassis Frame
Chassis less Tractor
As the name implies, these tractors do not need any type of chassis frame. The normal of a
tractor chassis frame is done by the Engine block itself. These machines are tough in nature to
fulfill the requirements.
The front part of the engine block is fastened or attached to the front cross member while the
engine block at rear side is attached to the transmission box. The front axle in front side is fixed.
The different brands of tractors use these types of frames. Massey Ferguson Tractors use perkin
engine. Here, sump is made extra heavy duty and acts as a connecting link between front cross

23. 20
member and transmission links. It has been observed that tractors which use Automotive Engines
have heavy duty sump which works as connecting link.
Tractor with Chassis Frame
The extra load is carried by the tractor chassis mechanics in this case. The engines in these
vehicles are light in weight and cannot take extra load to act as chassis alternative. In this case, it
is necessary to provide a chassis on which engine is mounted.
The chassis frame is connected to front cross member at front side and the rear side is attached to
the transmission box.
The long members of these frames consist of following cross sections.
1) Tubular Section
2) Channel Section
3) Box Section
Tubular Section:
This type of section is mostly used in tractors where brackets are welded to the front and rear of
tubular frame for the purpose of connecting.
Channel Section:
This is mostly used sections as it has more strength for a specific load. Here, 2 long members are
fixed to the front end while the rear sides are attached to the clutch housing. This clutch housing
is an important part of transmission box.
The major components are listed below:
• Gear Box interface
• Fixing the Bolts
• Clutch Housing
• Engine Mounting
• Chassis Long Members
• Front Cross Member
The Maintenance of Tractor Chassis
Tractor Chassis is made very strong to withstand the extra loads. So, these frames generally do
not require much care during their life span apart from keeping the bolts tightened. In some
cases, tractor might be used in extreme conditions and thus may cause some defects. These
defects are specified below:

24. 21
1. Loose Rivets
2. Cracks
TRACTION AND TRACTOR THEORY
Meaning of traction.
Traction is the force used to generate motion between a body and a tangential surface, through
the use of dry friction through the use of shear force of the surface. Also can be defined as the
force developed by the traction device medium (soil) and transferred to the vehicle.
The power developed in engine, it goes to wheel or tracks which move the tractor with or
without an attached load. During the movement of wheels, some slip occurs which causes
reduction in speed. The slippage also occur with increasing load.
Traction can be increased by
(i) Using rubber tires with grooves
(ii) Placing tires chains
(iii) Using ribbed treads on tracks links
(iv) Putting lugs cleats or grousers on the wheel rim.
Terms used in tractions.
 Traction device
It is a device for propelling a vehicle using the traction forces from the supporting
surface.
 Coefficient of traction
It is the ratio of the total force output of the traction device in the direction of the
travel to the dynamic weight on the traction device.
 Tractive Efficiency
It is the ratio of output power usually expressed in percentage.
Also tractive efficiency is affected by several factors such as
(i) Tyre inflation pressure
(ii) Soil condition
(iii) Wheel size
(iv) Speed of travel
(v) Slope of the land
(vi) Height of the hitch
(vii) Shape and size of lugs.

25. 22
 Rolling resistance
It is the force required in the direction of travel to overcome the resistance of motion.
 Coefficient of rolling resistance
It is the ratio between rolling resistance and dynamic weight.
 Wheel slip or track slip
It is the relative movement of the wheel or track in the direction of travel for a given
distance under load and at no load condition. It can be calculated by the formula.
Wheel slip = N1 – N0/N1
Wheel slip percentage = (N1 – N0/N1) x 100%
Where: - N1 – Number of revolutions of driving wheel or sprockets for a given distance under
load.
N0 – Number of revolutions of the driving wheels or sprockets for the same distance at no load.
 Rim pull.
Is a term which is used to designate the tractive force between the rubber tyres of the driving
wheels and the surface on which they travel. The coefficient of traction is high enough to
eliminate tyre slippage. The maximum rim pull is a function of the power of the engine and the
gear ratios between the engine and the diving wheels.
TRACTION THEORY
Pneumatic tyres are used for common tractors when such a tractor moves over soil, it has to
overcome the rolling resistance R as shown.
Where F = Force of traction in the direction of travel
P = Pull used for useful work
R = Rolling resistance
In order to calculate pull P and rolling resistance Bekker has suggested the following equation
F = A[C+P ]
F = [AC+W ]
Where, A=Area which will shear off
P = Soil pressure

26. 23
C = Cohesion of soil
Angle of internal friction of soil
W = AP= Vertical load over the shearing area.
It is evident that tractive force is usually dependent upon vertical force and the area of shearing
for a track type tractor, the soil pressure P is given by
Where B is the width of each track and L is the length of track in contact with the soil.
For pneumatic tired wheel the contact area with the soil is an ellipse and for that uniform soil
pressure P is given by.
 Rolling resistance.
The rolling resistance due to soil compaction can be approximated by assuming that
the energy required to overcome the rolling resistance is equal to the work done in
deforming the soil. The rolling resistance R can be obtained by the relationship.
Where
N = coefficient of wheel sinkage
Kc = Cohesive modulus of soil deformation
Kα = Friction modulus of soil deformation
B = Width of each track
W = Vertical load over the shearing area.
L = Length of track in contact
This equation is derived by assuming a flat plate as in a crawler tractor. This equation is
approximately correct also for rubber tired tractors when the rolling resistance and tractive force
are calculated the useful pull P can be obtained by the equation.
P = F - R

27. 24
TRACTOR SAFETY
The following matters need to be considered in relation to tractor safety;
1. Do not engage clutch rapidly or use incorrectly hitching.
2. Many tractors are difficult to mount and there is a risk of injury by falling, mount tractor
carefully, being sure not to sleep.
3. Check noise and smoke of driver position under varying conditions because they endanger
health of drivers.
4. Brakes should be kept correctly adjusted at all times and locked together when riding tractor
on the road
5. Never allow extra driver on tractor
6. Be careful refilling radiator on over heated tractor or with pressure cooling system
7. Do not operate tractor in a closed building or where exhaust will contact flammable
materials
8. Stay on seat while tractor is in motion never dismount until it stops
9. Keep tractor in gear going down steep hill or grades
10. Always stops the tractor before removing or replacing a belt
11. Avoiding refueling or other services while tractor is running or extremely hot
12. Engage clutch gently ,especially when pulling up hills, out of ditches or heavy loads
13. Observe standards traffic signals when operating public high ways
14. See if every one is in clear before starting the tractor engine
15. Use lights for night operations , don’t operate in dark
16. Use wide wheel treads whenever possible
17. Keep tractor in good mechanical conditions , check brakes, clutch, lights, fuel line and
control mechanism frequently
18. Avoiding wearing loose sloppy clothing while operating tractor.

28. 25
NOTE:
A copy of all operating manuals and other relevant safety materials should be kept on file
for quick reference.
Use Tractor for Intended Purposes
The tractor has many uses around the farm, however, improper use can result in an accident. For
example, using the tractor to round up the cattle is dangerous because the operator may
encounter rough, uneven ground and make sharp turns at high speeds.
Check Tractor Before Operating
A pre-operational check of the tractor will assure you that it is in safe operating condition. Check
the tires for proper inflation and defects, windows for visibility, seat position, seat belts, brakes
for adjustment, steering response, rear view mirrors, slow-moving vehicle emblem, reflectors,
and running lights for day or night time operation.
Safety Check:
Walk around the tractor and any attached implement checking the area for obstacles that may be
under or near the tractor. This includes stones, boards, children's toys etc. Make sure there are no
bystanders; remember this is a work area. Check that the wheels are free, not frozen or stuck in
the ground. If the rear wheels are frozen to the ground, then the tractor may flip backwards
around the axle when power is applied. Check for any loose parts or objects on the tractor such
as tools on the platforms or around brakes and other controls.
Service Walk around:
Walk around the tractor a second time to check the tractor itself. This time look at the tires for
wear and inflation, the power takeoff shaft for shielding and guarding (rotate the shield to make
sure it moves freely), the hitch for proper hitch pin and safety clip. Pay particular attention to the
ground under the tractor for any signs of liquid leaks such as oil, coolant or fuel.
Check the oil:
Remove the dipstick, wipe it clean and check the oil level. If oil is required, remember to wipe
off the filler cap before you remove it to avoid dirt falling into the engine. Use a Clean funnel
and clean the top of the oil can to prevent rust or other foreign objects going in with the oil.
Check the radiator: Slowly remove the red cap and check the liquid level.

29. 26
Check the air pre-cleaner and air cleaner. Remove and shake out any dirt.
Check the fuel level. Fill if necessary, but it should have been filled at the end of the last day the
tractor was used.
Check the fire extinguisher. Your tractor should have a fire extinguisher in case of fire during
operation or refueling. Make sure it is charged and easily accessible.
Any noted defects should be corrected immediately. These can affect performance and
your safety!
BATTERIES: HANDLE WITH CARE!
Occasionally it may be necessary to handle, adjust or change the battery on your tractor.
Batteries contain sulfuric acid which can cause considerable harm if it comes into contact with
your skin. They can also produce mixtures of hydrogen gas and oxygen which can explode if
contacted with heat or sparks. Remember these safety points:
1. Do the work or adjustments in an area free of sparks and heat sources. Don't smoke while
working near the battery. Make sure the area is well ventilated.
2. Always wear personal protective equipment, covering the eyes and hands. A full face
shield will offer the most protection.
3. Never work leaning directly over the battery.
4. Always disconnect the ground cable first and identify the cables as positive and negative
so that you don't re-attach them wrong.
5. Make sure that you clean the terminals and cable connections before re-attaching them.
Make sure the new battery is secured with the hold-down assembly provided.
6. While installing the battery make sure that the terminals don't come into contact with
metal parts on the engine or tractor body.
7. Make sure that you connect the ground cable last to prevent sparks and tighten the
connections!
HYDRAULIC SYSTEMS AND SAFETY
Working with or on hydraulic equipment can be dangerous. Some of the hazards cannot even be
seen readily. Hydraulic systems are under tremendous pressure and this is where the unseen
danger lies.

30. 27
Before servicing hydraulic systems:
1. Shut off the engine powering the hydraulic pump.
2. Lower the implement to the ground.
3. Relieve pressure by moving the hydraulic control lever back and forth.
4. If working around or under a raised implement, make sure that it is blocked or supported
by something other than the cylinder itself.
5. Use a piece of cardboard or wood to check for leaks in hoses and fittings. Even a small
amount of pressurized hydraulic fluid can be injected through the skin and cause severe
health problems. Seek medical attention immediately if hydraulic fluid penetrates your
skin.
6. Use caution when releasing blocks or transport locks on equipment. If a cylinder has
leaked and lost pressure, the implement may fall to the ground as the locks are released.
OPERATOR'S CHECKLIST FOR PERSONAL SAFETY
Before even considering starting the tractor, ask yourself the following questions:
Yes No
Are you in good health?
Are you free from the effects of drugs and alcohol?
Are you wearing hearing protection?
Are your close snug-fitting?
Are you wearing safety glasses?
Is any long hair tucked under a hat?
If you answered NO to any question, DO NOT OPERATE THE TRACTOR!
STARTING AND STOPPING YOUR TRACTOR
1. If your tractor is indoors, you must provide adequate ventilation by opening doors or
windows and using exhaust fans if available. Carbon monoxide is a deadly gas and can
build up rapidly in a confined or relatively closed area. Carbon monoxide is always
present in the exhaust of all engines.
2. Start the tractor only from the operator's platform. Many modern tractors cannot start
unless the clutch pedal is depressed, but some older tractors still in use can be started
while the operator is standing on the ground. This must never be done. There are
recorded cases of farmers who have been killed while attempting to start the tractor while
standing next to it. The tractors in question were either in gear or the operator bumped the

31. 28
gear shift, causing the tractor to lurch forward and run over them. Never attempt to
bypass the safety start switch.
3. Check the Power Takeoff controls to make sure that they are disengaged, and that the
transmission is in neutral and the clutch depressed.
4. Start the engine following recommended starting procedures in your operator's manual.
5. Allow the engine to warm up before staring to work with it. Working a cold engine is a
major source of contamination of engine oil.
6. Check all the instruments. Make sure that there is proper oil pressure, that the battery is
charging etc.
Shutting down the engine:
1. Always allow an engine to cool down at a fast idle before shutting it off. This allows the
valves and pistons to cool down uniformly. Lower all hydraulic lift equipment to the
ground.
2. After shutting off refill the fuel tank when the tractor has cooled a bit. Make sure that the
park brakes are locked. Check that there is no combustible debris near the exhaust system.
Note: Everyone on the farm including family and employees should be taught how to safely shut
off machinery. This is especially important in an accident situation. The first person on the scene
must know how to shut things off. It could save a life!
Take Special Care with Large Four-Wheel Drive Tractors with Articulated Steering
Operating large four-wheel-drive tractors with articulated steering requires skills in addition to
those necessary for operating a two-wheel-drive tractor. The operator must be especially
concerned about safety because of the increased power and large dimensions of the tractor, faster
speeds, and different visual perspective.

32. 29
TRACTOR TESTING
The information on the power performance on the tractor is required for various purposes for
management and for selection between models. The need for having reliable data performance
through tractor testing is very important.
In testing tractor the following areas are very important;
1. Identification of stock model, which includes: manufacturer, tractor from, ground drive,
transmission, implement working system, tractor serial number, engine number,
recommended fuel, fuel setting.
2. Power output supply, includes Engine, crankshaft, belt pulley, drawbar.
3. Accommodation, attachment and accessories.
4. Power take- off.
5. Steering stability, belt pulley and belt speed.
6. Fuel power test.
7. Performance generally; high or low
TRACTOR MAINTENANCE
Maintenance of tractor basically can be done before and after work hours for better detection of
the problems;
(i) Before work hours.
 Check oil level by using deep stick, deep stick has two levels which are maximum
and minimum levels, level of oil should not be at minimum level.
 Water level, water should be fully at the radiator.
 Tyres pressure should be at its required quality.
 Hydraulic at the steering should also be at its best level.
Generally it can be done whenever there is any problem for safety and life span of your
tractor.
SEVERAL USES OF FARM POWER TRACTORS
Agricultural equipment’s any kind of machinery used on a farm to help on farming process. The
best known example of this kind is tractor. Farm power tractor used for several functions such
as:-

33. 30
(i) Planting
Done with another frame mounted three point hitch implement that has row
opener planter boxes and packing wheel that drop seeds at the desired spacing and
depth in the soil.
(ii) Fertilizer spreader
Tractor used to spread fertilizer in the farm by mount the implement that can be
able to spread fertilizer on the field. Some incorporate plough assemblies to
deposit the fertilizer directly along rows other broadcast it over the field.
(iii) Harvesting
Also tractor gathering some crops like peanut that do not have a dedicated
machine to do the job.
(iv) Tilling
Tractor digging into and till soil to turn plant matter under and prepare for
planting. It is done with a power take off (P.T.O) implement with a gear driven
tires.
(v) Mowing
This involve the cutting for hay or silage or simply cleaning overgrown field. Can
be done with a rotary cutter (bush hog) a sickle bar or drum mower depend on the
activity that you want to do.
(vi) Spraying
Tractor as a farm device can also be used to spray pesticide and other chemical in
the farm, this can be done with tank sprayer.
(vii) Plowing
By using a frame which supporting different type of plows tractor can be used for
breaking, cultivating or sub soiling.
All these are uses of tractor not only that but also can be used for transportation of
goods from the farms and to the farms.

34. 31
POWER TILLER
Are machine powered with 1-5 horse power engine and design to propel forward and backward
different agricultural implements .Also can be operated by walking or sitting depends on the
implements it push or pull e.g. to pull disc plow or push reaper harvester. As a safety feature
most Power Tiller can propel forward and not backward. It is a prime mover in which the
direction of travel and its control for field operation is performed by the operator (man) by
holding the two hands of Power Tiller in his or her hands. The concept of power tiller came in
the world in the year 1920. Japan is the first country to use power tiller on large scale. Power
tiller was first introduced in India in the year 1963. Average size of holding in Tanzania is about
2.5Hectares. There are 89% of total land holdings of less than six hectares. Under such
conditions, power tiller may be useful as a power unit.
Components of power tiller:
A power tiller consists of the following main parts:
(i) Engine
(ii) Transmission gears
(iii) Clutch
(iv) Brakes
(v) Rotary unit.
All the power tillers are fitted with an I. C. engine. At present, most of the power tillers are fitted
with diesel engine. The main clutch is a lever on the handle. The lever can be shifted to on or off
position while operating in the field. When the lever is shifted to on position, the power from the
engine is transmitted through the main clutch to the various parts of the power tiller. When the
lever is shifted to off position the power from the engine is cut-off from the rest of the
transmission.

35. 32
Pull power tiller

36. 33
Power transmission in power tiller:
For operation of power tiller, the power is obtained from the IC Engine, fitted on the power
tiller. The engine power goes to the main clutch with the help of belt or chain. From main clutch,
the power is divided in two routes, one goes to transmission gears, steering clutch and then to the
wheel. The other component goes to the tilling clutch and then to the tilling attachment.
The flow diagram for transmission of power is given below:-
Transmission gear Steering clutch wheels
Engine Main clutch
Tilling clutch Tilling attachment
 V-belt is usually used to transmit power from the engine to the main clutch, because V-
belt has very high efficiency and it works as a shock absorber also.
 Main clutch: Power goes from the engine to the main clutch. Clutch may be: (i) Friction
clutch or (ii) V-belt tension clutch.
Friction clutch is generally used for bigger power tiller. Usually it is a dry type multiple
disc clutch.
V-belt tension clutch is used for small power tillers. The main functions of clutch in a
power tiller are:
(i) to transmit engine power to transmission gears
(ii) to make power transmission gradual and smooth.
 Transmission gears: Transmission box consists of gears, shafts and bearings. The speed
change device may be; (a) gear type or (b) belt type.
 Brakes: All power tillers have some braking arrangement for stopping the movement.
Most of the power tillers use inner side expansion type brake.
 Wheels: Usually 2 to 4 ply pneumatic tyres are used in power tillers. The pressure of the
tyre ranges from 1.1 to 1.4 kg/cm2.
 Rotary unit: Power tiller has a rotary unit for field operation.
Rotary unit is of two types:
(a) Centre drive type
Has got transmission at the Centre and the side drive type has transmission at
one is light in weight

37. 34
(b) Side drive type.
(i) Deeper tilling is possible
(ii) The arrangement is useful for hard soil
(iii) It has two points support on the ground.
(c) Fixing of attachment is easy
(d) The tine shaft can be detached easily
(e)Mounting and dismounting of rotary unit is very easy
(f) It may leave some portion of the field untilled
(g) It has one point support on the ground.
 Rotary tines: Rotary tines are used in rotary unit for soil cutting and pulverization
purpose. Rotary tines are of three types:
 (i) Straight tines
(a) Power consumption is less
(b) Fine pulverization of soil is possible
(c) Poor soil turning
(d) Grass entangles in the tines very easily
(e) It is suitable for hard soil.
(ii) Curved tines
(a) Good soil turning is possible
(b) It is suitable for avoiding grasses
(c) Pulverization of soil is coarse
(d) Power consumption is high.
(iii) Sliding tines.
(a) Good soil turning is possible
(b) It is suitable for avoiding grasses
(c) Pulverization of soil is coarse

38. 35
 Sliding tines have the characteristics of sliding on their positions according to the
requirement.
 Steering cutch lever: Steering clutch is provided on the grip of the right and left handles.
When the left side is gripped, power is cut-off on left side of the wheel and the power
tiller turns to the left. Similarly when the right side is gripped, the power tiller turns to the
right.

Benefit and added value of the Power Tiller in agricultural operation
Power Tiller can power the operation of various farm implements such as; plow disc, rotary
puddler, leveler, thresher, and a trailers. Power tiller is light and easy to manipulate in the field
during dry and wet
 It allows expansion of cultivatable land.
 Improves timelines of farm operations
 Improves quality of work and products
Drawback of power tiller
 It is an investment of high costs but can be used for all farming operation including
transport of agricultural products.
 It requires regular maintenance by skilled operator.
DESCRIPTION OF ENGINE POWERED BY ALCOHOL AND
VEGETABLE OIL (BIO-FUEL).
This is a fuel that is produced through contemporary biological processes, such as agriculture
and anaerobic digestion, rather than a fuel produced by geological processes such as those
involved in the formation of fossil fuels, such as coal and petroleum, from prehistoric biological
matter.
Biofuels can be derived directly from plants, or indirectly from agricultural, commercial,
domestic, and/or industrial wastes. This biomass can be converted to convenient energy-
containing substances in three different ways:
 Thermal conversion
 Chemical conversion,
 Biochemical conversion.

39. 36
This biomass conversion can result in fuel in solid, liquid, or gas form. This new biomass can
also be used directly for biofuels.
Bioethanol
This is an alcohol made by fermentation, mostly from carbohydrates produced in sugar or starch
crops such as corn, sugarcane, or sweet sorghum.
Cellulosic biomass
This is derived from non-food sources, such as trees and grasses, is also being developed as a
feedstock for ethanol production. Ethanol can be used as a fuel for vehicles in its pure form, but
it is usually used as a gasoline additive to increase octane and improve vehicle emissions.
Biodiesel
This can be used as a fuel for vehicles in its pure form, but it is usually used as a diesel additive
to reduce levels of particulates, carbon monoxide, and hydrocarbons from diesel-powered
vehicles. Biodiesel is produced from oils or fats using transesterification and is the most
common biofuel in Europe.
EXAMPLE OF THE ENGINE WHICH USE BIODISEL
Using Biodiesel in John Deere Engines
All John Deere engines can use biodiesel blends. B5 blends are preferred, but concentrations up
to 20 percent (B20) can be used providing the biodiesel used in the fuel blend meets the
standards set by the American Society of Testing Materials (ASTM) D6751 or European
Standard (EN) 14214Studio image of the 6090 PTP 403970 Engine Studio image of the 6090
PTP 403970 Engine

40. 37
Types of fuels
The following fuels can be produced
Ethanol
Biologically produced alcohols, most commonly ethanol, and less commonly propanol and
butanol, are produced by the action of microorganisms and enzymes through the fermentation of
sugars or starches (easiest), or cellulose (which is more difficult)
Biobutanol (bio gasoline) is often claimed to provide a direct replacement for gasoline, because
it can be used directly in a gasoline engine.

41. 38
Ethanol fuel is the most common biofuel worldwide. Alcohol fuels are produced by fermentation
of sugars derived from wheat, corn, sugar beets, sugar cane, molasses and any sugar or starch
from which alcoholic beverages such as whiskey, can be made (such as potato and fruit waste,
etc.). The ethanol production methods used are enzyme digestion (to release sugars from stored
starches), fermentation of the sugars, distillation and drying
Ethanol can be used in petrol engines as a replacement for gasoline; it can be mixed with
gasoline to any percentage. Ethanol has a smaller energy density than that of gasoline; this means
it takes more fuel (volume and mass) to produce the same amount of work.
An advantage of ethanol (CH3CH2OH) is that it has a higher octane rating than ethanol-free
gasoline available at roadside gas stations, which allows an increase of an engine's compression
ratio for increased thermal efficiency
Biodiesel is also safe to handle and transport because it is non-toxic and biodegradable, and has a
high flash point of about 300 °F (148 °C) compared to petroleum diesel fuel, which has a flash
point of 125 °F (52 °C).
Other bio-alcohols
Methanol is currently produced from natural gas, a non-renewable fossil fuel. In the future it is
hoped to be produced from biomass as bio methanol.
Butanol (C4H9OH)
This is formed by ABE fermentation (acetone, butanol, and ethanol) and experimental
modifications of the process show potentially high net energy gains with butanol as the only
liquid product. Butanol will produce more energy and allegedly can be burned "straight" in
existing gasoline engines (without modification to the engine or car), and is less corrosive and
less water-soluble than ethanol, and could be distributed via existing infrastructures
Green diesel
Vegetable oil refining
Green diesel is produced through hydrocracking biological oil feedstock’s, such as vegetable oils
and animal fats. Hydrocracking is a refinery method that uses elevated temperatures and pressure
in the presence of a catalyst to break down larger molecules, such as those found in vegetable
oils, into shorter hydrocarbon chains used in diesel engines.

42. 39
Vegetable oil
Vegetable oil fuel unmodified edible vegetable oil is generally not used as fuel, but lower-
quality oil has been used for this purpose. Used vegetable oil is increasingly being processed into
biodiesel, or (more rarely) cleaned of water and particulates and then used as a fuel.good
performance at low temperatures, no storage stability problems and no susceptibility to microbial
attack
EXAMPLE OF THE ENGINE USING VEGETABLE OIL
Biogas
Biogas is methane produced by the process of anaerobic digestion of organic material by
anaerobes. It can be produced either from biodegradable waste materials or by the use of energy
crops fed into anaerobic digesters to supplement gas yields. The solid byproduct, digestate, can
be used as a biofuel or a fertilizer.

43. 40
Solid biomass fuels
Examples include wood, sawdust, grass trimmings, domestic refuse, charcoal, agricultural waste,
nonfood energy crops, and dried manure.
When solid biomass is already in a suitable form (such as firewood), it can burn directly in a
stove or furnace to provide heat or raise steam. When solid biomass is in an inconvenient form
(such as sawdust, wood chips, grass, urban waste wood, agricultural residues), the typical
process is to identify the biomass.
One of the advantages of solid biomass fuel is that it is often a byproduct, residue or waste-
product of other processes, such as farming, animal husbandry and forestry. In theory, this means
fuel and food production do not compete for resources, although this is not always the case
A problem with the combustion of solid biomass fuels is that it emits considerable amounts of
pollutants, such as particulates and polycyclic aromatic hydrocarbons. Even modern pellet
boilers generate much more pollutants than oil or natural gas boilers.
Biomass and Environmental damage
Biofuels are similar to fossil fuels in that biofuels contribute to air pollution. Burning produces
carbon dioxide, airborne carbon particulates, carbon monoxide and nitrous oxides

44. 41
REFERENCES
Makungu,P.J.,and Dihenga,H.O.(1995) Sources of farm power.Sokoine University of
Agriculture,Morogoro,Tanzania.
http://en.wikipedia.org/w/index.php?title=Tractor&oldid=645513239" .
Nakra, C. P. 1986. Farm Machinery and Equipment. Dhanpat Rai and Sons, New Delhi.
Klenin, N.I., Popov, I.F., and Sakun, V. A. 1985. Agricultural Machines. Amerind publishing
Co. Pvt. Ltd., New Delhi.
Jagdishwar Sahay. 2006. Elements of Agricultural Engineering. Standard Publishers and
Distributors, New Delhi.
Michal, A. M., and Ojha, T. P. 2008. Principles of Agricultural Engineering, Vol. I Jain Brothers,
New Delhi