Agricultural machinery chapter 2 tillage implement

BAHIR DAR UNIVERSITY
BAHIR DAR INSTITUTE OF TECHNOLOGY (BiT)
FACULTY OF MECHANICAL AND INDUSTRIAL
ENGINEERING
Course Title: Agricultural Machinery Technology(AEng5161)Course Title: Agricultural Machinery Technology(AEng5161)
CHAPTER TWO
Tillage Implements
By
Solomon Tekeste
7/11/2018 1

SOIL TILLAGE
INTRODUCTION
• Tillage may be defined as the mechanical manipulation of
soil for nurturing crops.
The objectives of soil tillage are:
– To develop a desirable soil structure for a seedbed
– To control weeds or remove unwanted crop plants.
– To manage plant residues.
– To minimize soil erosion by following such practices as
contour tillage
– To establish specific surface configurations for planting,
irrigating, drainage, or harvesting operations.
– To incorporate and mix fertilizers, manure, pesticides7/11/2018 2

Tillage
Classification of Tillage
• Depending on the quantity of soil disturbance
Primary Tillage
 More aggressive, deeper
operation and usually leaves
the surface rough
Secondary Tillage
 Works the soil to shallow
depth
Function :
 Function :
 Loosen the soil structure
 Bury the plant waste
 Erosion control
 Preparation for secondary
tillage
 Weed control
 Kill pests
 Function :
 Break the soil clods
 Shatters the soil clods
 Level the soil surface
 Harrow the soil and plant
waste (stubbles)
 Firm the soil
 Kill weeds and helps conserve
moisture7/11/2018 3

Tillage
• Tillage Implements
Primary Tillage Implements
• Mould board ploughs
• Disk ploughs
• Chisel ploughs
Secondary Tillage Implements
• Harrows
– Disc
– Spring tooth• Chisel ploughs
• Sub-soilers
• Rotary tillers
– Spring tooth
– Spike tooth
• Cultivators
– Spring
– Rigid tined
• Rollers
• Weed Control Implements
7/11/2018 4

Primary Tillage Implement
Mould board Ploughs
• This is most common primary tillage implement.
• Can effectively break many type of soils.
• Its basic function is to cut, invert and pulverize the
soil up to the depth of 20-30cm.
7/11/2018 5

Components of Mouldboard Ploughs
• Share:This penetrates into the
soil and makes a horizontal cut
below the surface.
• Mould board: It is curved, it
lifts and turns the furrow slice.
• Land side: Flat plate
which bears against and
transmits the rear side
lateral thrust of the
plough.
• Frog: This is where other
components of the plough
bottom are attached.
7/11/2018 6

• Beam: The part through
which the power is applied
and the other parts are
attached
Components of Mouldboard Ploughs
attached
• Gange wheel: Attached to
the end of the beam and
used to control ploughing
depth.
• Coulter: makes the vertical
cut separating the furrow
slice from the un-ploughed
land.7/11/2018 7

Mouldboard Ploughs
Two-way or Reversible Mouldboard plough
• It is a mouldboard plough which turns furrow slice to
the right or left side of direction of travel as required.
Such ploughs have two sets of opposed bottoms.
7/11/2018 8

 ∆s- distance of the plough edge
from furrow wall
 H- height of plough/ throatal
clearance
Design Parameters of Mouldboard plough
clearance
 a- Depth of furrow slice
 b- width of furrow slice
 S- width of share blade
 2-cutting angle of share blade
 Cp -Center of power
 Cr -Centre of resistance
7/11/2018 9

 - setting angle/rake
angle
 R- radius of the
directrix curve
 t- thickness of the
Design Parameters of Mouldboard plough
 t- thickness of the
moldboard
 w- landslide width
 l- landslide length
 Lp -Line of pull
 P-Pull
 D-Draft
7/11/2018 10

Disk Ploughs
• The basic function is
– soil is lifted, pulverized, partially inverted and displaced
to one side.
• Blades on disk ploughs are concave, usually representing
sections of hallow spheres.
7/11/2018 11

 Used when moldboard plow does not work
satisfactorily
 Hard sticky soils
 In hard dry soils
 Stony fields
Disk Ploughs
 Stony fields
 Soils containing heavy roots
 Loose, push type soils and abrasive soil
 Built with heavy frame and wheels; in a hard dry soil, a
disc plow can be forced into ground by its weight
7/11/2018 12

 The basic component of plough is a disc of certain
diameter and curvature.
 It consists of a series of individually mounted,
concave, rotating discs characterized by disc and tilt
angle
Disk Ploughs
angle
7/11/2018 13

 The tilt angle is usually in the range of 150 to 250 and
the disc angle is in the range of 420 to 450.
 The disc angle can influence the width of cut in which
too great angle requires a greater pull.
 Tilt angle affects the penetration of plough and high
penetration is obtained when the tilt angle is closer
Disk Ploughs
penetration is obtained when the tilt angle is closer
to the vertical.
7/11/2018 14

Comparison of Mouldboard Plough & Disc Plough
Criteria
Implements
Mouldboard Plow Disk Plow
Inverting Good Medium
Mixing Hardly Medium
Crumbling Medium Medium/good
Mixing Hardly Medium
Crumbling Medium Medium/good
Burying long stubble Completely Not completely
Plough sole compaction Reasonably high Little
Susceptibility to damage Highly/More Little
Possible fields of use Clean field Heavy, dry, stony, etc.
Durability Medium High
Weight Lower High
Draught requirement high high
7/11/2018 15

 Example of secondary implements :
 Disc, spring tooth and spike tooth harrow
SECONDARY TILLAGE IMPLEMENTS
7/11/2018 19

 Spring and rigid tined cultivators
7/11/2018 20

 Roller pocket and roller harrows
7/11/2018 21

 Weed control implement
7/11/2018 22

CLASSIFICATION OF TILLAGE
IMPLEMENTS
 Based up on their attachment/ hitching system to the
tractor, tillage implements can be categorized in to
three follows.
Mounted implements Mounted implements
 Semi-Mounted implements
 Trailed implements
7/11/2018 23

IMPLEMENTS
Mounted implements
 Attached to the tractor by 3 point hitch linkages
 Implements can be raised or lowered by the
hydraulic system
 Example : A mounted disc ploughExample : A mounted disc plough
7/11/2018 24

IMPLEMENTS
Semi-mounted implements
 Attached to the tractor 2 point or 3 point linkage and
these implements are normally provided with wheels to
help in better performance of the machine
 Example : A seed drill – implement can be raised or
loweredlowered
7/11/2018 25

IMPLEMENTS
Trailed implements
 Attached to the tractor’s drawbar and this cannot be
raised or lowered
 Implement trailed the tractor as it moves
 Implement are heavy and usually provided with
wheels for easy hitching to the back of tractor and
better stabilitybetter stability
 Example : Trailed moldboard plough and trailer
7/11/2018 26

PERFORMANCE OF TILLAGE IMPLEMENTS
• The performance of tillage tools is determined by their
draft and power requirements and the quality of work.
• The effects of soil and tool parameters as well as the
operating conditions on the draft force and power
requirements are discussed.
• The draft is defined as the component of tractor pull
acting on the plow parallel to the line of travel.
• The specific draft is the draft divided by the cross-
sectional area of the furrow.
7/11/2018 27

• The specific draft of ploughs varies widely under
different conditions, these factors include;
– Soil type and condition
– Ploughing speed– Ploughing speed
– Depth of ploughing
– Width of furrow slice
– Plough bottom shape
– Implement weight
– Friction characteristics of the soil engaging surfaces
– Adjustment of the plough and attachment
7/11/2018 28

Soil Type and Condition
• Soil type and condition are by far the most important
factors contributing to variations in specific draft. It
is very high for very heavy clay soils and very low foris very high for very heavy clay soils and very low for
sandy soils.
• Soil moisture is an important factor in regard to both
draft and quality of work. A dry soil requires
excessive power and also accelerates the wear of the
cutting edge.
• Other pertinent soil factors include the degree of
compaction, the previous tillage treatment, and the
type or absence of crop cover.7/11/2018 29

Effect of Depth and Width of Cut
• Specific draft of a plough generally decreases as the
depth is increased to some optimum depth/width
ratio and then increases as the depth increased
further.
further.
• The initial decrease of specific draft with increased
depth is logical because the total force for cutting
the bottom of the furrow slice should be independent
of depth.
• The increase in specific draft beyond the optimum
depth is probably due to partly choking of the thick
furrow slice in the curvature of the mould board.
7/11/2018 30

Effect of Speed upon Draft
• In general, increased forward speed increases the draft with
most tillage implements, because of the more rapid
acceleration of any soil that is moved appreciably. Soil
acceleration increases draft for at least for two reasons:
– Acceleration forces increase the normal loads on soil engaging
surfaces, thereby increasing the frictional resistance.
– The kinetic energy imparted or induced to the soil.
– The kinetic energy imparted or induced to the soil.
• Thus, in order to minimize the draft requirement it is
necessary to operate the implements at recommended
optimum forward speeds. The optimum forward speeds for
conventional implements are:
– Mould board ploughs------ 6 km/hr
– Medium depth tined implements -------- 8 km/hr
– Shallow cultivation and grain drilling ----- 10 km/hr
7/11/2018 31

Effect of Implement weight on draft requirement
• In general as the implement weight increases, the
draft requirement is also increases.
7/11/2018 32

Principles of Hitching
• With the plough body correctly fitted and set, it is
necessary to adjust the hitch and the wheels to
produce the required depth and width of work.
• If a single chain could be attached at the proper
hitching point, the plough could be pulled straight
hitching point, the plough could be pulled straight
ahead at a uniform depth and width.
7/11/2018 33

• Center of load on a plough bottom
7/11/2018 34

Center of load on a plough bottom
7/11/2018 35

• Horizontal Hitch Alignment
7/11/2018 36

• Vertical Hitch Alignment
7/11/2018 37

FORCES AND EQUATION OF IMPLEMENTS IN
OPERATION
• The engineers are concerned with the forces acting
on a tillage implement because of:
• Total power requirements.• Total power requirements.
• Proper hitching or application of pulling force.
• Designing for adequate strength and rigidity.
• To determine best shape and adjustment of
tools
7/11/2018 38

• A tillage implement (or tool) moving at a constant
velocity is subjected to three main forces or force
system which must be in equilibrium. These are:
– Force of gravity upon the implement.
OPERATION
– Force of gravity upon the implement.
– The soil forces acting upon the implement
– The forces acting upon the implement and the prime
mover.
7/11/2018 39

• If torque from rotary power transmission is not involved,
the resultant of these forces is the pull of the power
unit upon implement. Clyde sub-divides the total soil
reaction into two:
OPERATION
• Useful forces: - Are those forces which the tool must
overcome in cutting, breaking and moving of soil.
• Parasitic forces:- Are those forces (including friction
and rolling resistance) that act on stabilizing surfaces
such as land side and sole of plow or upon supporting
runners or wheels.
7/11/2018 40

• Forces acting on tillage implement or tool
OPERATION
7/11/2018 41

• If tool is not symmetrical about the vertical,
longitudinal plane through its center line, useful soil
forces usually introduce rotational effect.
• If P = Pull exerted by power unit has components in all
OPERATION
• If P = Pull exerted by power unit has components in all
the major planes
• R = Resultant of all useful forces acting upon tool or
implement
7/11/2018 42

• Let us resolve the forces in three components L, S, V.
• L = Horizontal component also called draft.
• V = Vertical component. It removes load from the front
wheel of tractor and effects on tractive ability
of tractor, stability and steerability. It helps in
OPERATION
of tractor, stability and steerability. It helps in
penetration and maintains working depth.
• S = Side draft or force. Maintains directional stability
on tractor and implement and affects on draft of
implement because of frictional forces.
•
7/11/2018 43

= ф
= ф
= ф
OPERATION
Where;
• θ = Angle of inclination of ‘R’ in vertical plane with
horizontal.
• ф =Angle of inclination of ‘R’ in transverse plane with
horizontal.
= ф
= ф
7/11/2018 44

• For mounted implements supported and pulled by tractor,
the force P between implement and tractor in vertical
plane is force containing L and V component.
OPERATION
= +
= ф + ф
= ф ( + )
= ф
7/11/2018 45

Terms Related to Field Performance of Machines
• The rate at which a machine can cover a field while
performing its intended function.
• Theoretical Field Capacity: is the rate of field capacity
that would be obtained if the machine were performingthat would be obtained if the machine were performing
its function 100% of the time at rated forward speed
and always covered 100% of its rated width.
• Theoretical field capacity (TFC)
widthRatedspeedRatedTFC 
7/11/2018 46

• Theoretical Time: is the time that would be required
at the theoretical field capacity to till a specified
area.
• Actual Field Capacity:- Actual field capacity is the
• Actual Field Capacity:- Actual field capacity is the
actual average rate of coverage by the machine,
based upon the total field time.
• Actual field capacity (AFC)
timeTotal
PlowedAreaTotal
AFC 
7/11/2018 47

• Field efficiency (FE): is the ratio of actual field
capacity to the theoretical field capacity.
100(%) 
TFC
AFT
FE
7/11/2018 48

• It includes the effects of time lost in the field and failure
to utilize the full width of the machine.
• Time losses during farm operation include:
 Time lost in turning at the ends or corners of the
 Time lost in turning at the ends or corners of the
field.
 Time lost in idle travel – across the ends of the field
 Time lost during rest stops
 Time lost for adjusting or checking equipment
 Time lost during field obstructions such as clogging
 Time lost for adding fertilizers or seeds, filling
sprayer tanks.
 Time lost during equipment breakdown7/11/2018 49

Design Procedure of Mouldboard Plough
& Disc Plough& Disc Plough
7/11/2018 50

Design Procedure of mouldboard ploughs
1. Establish the following points
– Type and kind of mouldboard
– Tillage depth, a
– Furrow slice width, b
– b/a ratio (1.1 to 1.5)
2. Design the angles of the share2. Design the angles of the share
– Load angle = 14-18 degrees
– Share angle = 35-45 degrees
– Cutting angle = 22-28 degrees
• Details of various angle of share
7/11/2018 51

3. Calculate drawbar horse power (DBHP) of tractor
• DHBP = 60% of BHP
4. Calculate drawbar pull
Drawbar pull available from tractor is given by
Drawbar pull available from tractor is given by
7/11/2018 52

5. Calculation of width of implement (Wi)
• The width of an implement (Wi) can be calculated from the
following formula:
Where,
• Di = draught requirement of implement, kg
• n = Number of bottoms in mouldboard plough
• dp=Depth of ploughing, cm
• R = Specific resistance of soil, kg/cm2
Soil type Unit draft(N/cm2)
Light soil 2.1-4.1
Medium soil 3.4-6.2
Heavy soil 5.88-9.7
Very heavy soil 8.82-14.71
7/11/2018 53

6. Forces acting on the mouldboard plough bottom
Various forces acting on plough bottom as shown in
figure
7/11/2018 54

7. Design of share of mouldboard plough
i. the best throat angle (share angle) of the share should be
an angle along which soil rapture takes place
Soil share angle (θ ) = 45 -φ
Where, φ = angle of friction between metal and soil
• Where, φ = angle of friction between metal and soil
ii. Now, the share may be assumed like a rectangular plate of
area (∆ABC + ∆BCD) subjected to bending.
7/11/2018 55

7/11/2018 56

• From the similar triangles ABC and BCF
7/11/2018 57

iii. Find values of CE by using sine theorem
iv. Calculate the total soil pressure on the share
iv. Calculate the total soil pressure on the share
• Unit draught of medium soil = 0.5 kg/cm2 and
• factor of safety as 2.0.
• Therefore, unit draught of share = 0.5 kg/cm2 x f.o.s =
0.5 x 2.0
7/11/2018 58

v. Total design draught of plough bottom = width x
depth x unit draught
– The total draught force will act on entire area of
share.
– It is assumed that the soil pressure is uniformly
distributed on the share.
distributed on the share.
Total area of share = area of ∆BCD + area of ∆ABC
vi. Therefore, soil pressure on share = total load, kg/area
of share cm2
– This load is acting on the share at ψ = 20⁰
7/11/2018 59

vii. Calculate length breadth ratio of share = L/b
viii.Calculate share thickness (t)
In the design of plough share law of bending of rectangular
plate with one side fixed and three sides freely supported
may be applied.
• For uniformly distributed loads on rectangular plate.
• For uniformly distributed loads on rectangular plate.
Where,
• Smax = max stress developed in share, kg/cm2
• F = Uniformly distributed load, kg/cm2
• B = A constant, depends on the length-breadth ratio of share
• t =Thickness of share, cm
7/11/2018 60

8. Design of landside of mouldboard plough
• landside takes side thrust of plough bottom caused during
turning of furrow slice.
• Usually force encountered by the landside is about 25-50% of
longitudinal force (Pull) acting on the plough bottom.
longitudinal force (Pull) acting on the plough bottom.
• Length of landside (Lls)
Length of landside (Lls) is calculated by using following
expression:
b = Width of landside, cm
φ = Angle of soil granular friction, degrees
α = Angle of pull with vertical plane, degrees
7/11/2018 61

Width of landside (b)
• Usually width of landside is taken as one third of
throat width of share of plough bottom.
Thickness of landside (t)
• it is assumed that one side is fixed on one end and
the other ends are free and side thrust is uniformly
the other ends are free and side thrust is uniformly
distributed over entire are of the landside.
• Now permissible stress in the landside is given by
ft = permissible stress in the landside, kg/cm2 or N/mm2
W = Uniformly distributed load on landside surface, kg/cm2 or
N/mm2
t =Thickness of landside, cm or mm
7/11/2018 62

9. Design of beam of mouldboard plough
• The mouldboard plough bottom of tractor drawn
plough is attached to a curved beam
• As the beam is curved therefore, theory of curved
beam is applied. According to theory of curved beams
of rectangular section, the bending stress is given by:
of rectangular section, the bending stress is given by:
f = Bending stress at any point at ‘y’ distance from axis = 500kg/cm2.
M = maximum bending moment induced in the beam
Ro = the initial radius of neutral surface, cm = R – e
e = distance between the neutral axis and the principal axis through centroid, cm
A = area of cross section of beam, cm2
7/11/2018 63

10.Design of frog:
• The frog is one soild piece suit fitting of share,
mouldboard and landside with considerable strength.
• It is usually made from pressed steel sheet, cast or
wheel steel.
wheel steel.
• The hardness of frog made from steel casting should
be 130-201 HB and for heavy duty cast iron the
hardness should be of 160-260 HB.
7/11/2018 64

Design of procedure for disc plough
7/11/2018 65

1. Calculate drawbar horse power (DBHP).
• Drawbar horse power (DBHP) is given by
DBHP = 60%BHP
2. Calculate diameter of disc (Dd).
• The diameter of disc is given by• The diameter of disc is given by
– K = a coefficient which varies from 2.5 – 3 for deep tillage
– dp = Depth of ploughing, cm
– β = Tilt angle of disc which is 15⁰ – 25 ⁰ -with vertical
• Also, the width of cut disc plough (W) is given by
7/11/2018 66

3. Radius of curvature of disc (R). The radius of
curvature of disc is given by
Where
Dd = diameter of disc, in cmDd = diameter of disc, in cm
φ = Half center angle of the arc of circle formed by
cutting disc on equatorial plane which is given by the
formula
α = disc angle, 45 ⁰
ε = Back cleaning angle, 3-5 ⁰
l = Sharpness/taper angle of disc, 15-25⁰
7/11/2018 67

4. Calculate disc spacing (Sd) in plough.
• The spacing between the discs (Sd) is given by
• Rh = ridge height, cm which is = 0.3dp for plough
• Dp= Depth of ploughing, in cm
• Dd = Diameter of disc, in cm
• α = Disc angle, 45⁰
• β = Tilt angle of disc which is 15⁰-25 ⁰ -with vertical
• e = Eccentricity of disc. Let e = 2
• Moreover, Sd > 2dp
7/11/2018 68

5. Width of cut (Wc).
• The width of cut of one disc is given by
6. Thickness of disc (Td).
• The thickness of disc for heavy soils is given by
7/11/2018 69

7. Number of bottoms or discs in plough (n)
– n = number of bottoms or discs in plough
– WC =Width of cut, in cm
– dp = Depth of ploughing, in cm
– k = Constant, for heavy soils k = 0.75-80 kg/cm2
– F =Factor of safety. (FOS=1.5)
7/11/2018 70

8. Design of main frame (Tabular section).
• For rectangular section
Where,
• f = bending stress at any point at y distance from neutral
axis = 500 kg/cm2
• M = Maximum bending moment = max draught x distance
7/11/2018 71

Reference
1. Ajit K. Srivastava et. al. 2012. Engineering Principles
of Agricultural Machines. Second Edition. American
Society of Agricultural and Biological Engineers.
2. D. N. Sharma and S. Mukesh. 2010. Farm Machinery
Design Principles and Problems. Second Edition.
Pusa Agri-Book Service, IARI, New Delhi.Pusa Agri-Book Service, IARI, New Delhi.
7/11/2018 72

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