A seed transport and delivery mechanism for the revolving spade planter

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Title:
A seed transport and delivery mechanism for the revolving spade planter
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v, 119 leaves : ill. ; 29 cm.
Language:
English
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Yeon, JeMan, 1957-
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Subjects / Keywords:
Farm equipment -- Design   ( lcsh )
Sowing   ( lcsh )
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bibliography   ( marcgt )
theses   ( marcgt )
non-fiction   ( marcgt )

Notes

Thesis:
Thesis (Ph. D.)--University of Florida, 2000.
Bibliography:
Includes bibliographical references (leaves 117-118).
Statement of Responsibility:
by JeMan Yeon.
General Note:
Printout.
General Note:
Vita.

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University of Florida
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All applicable rights reserved by the source institution and holding location.
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oclc - 47122864
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Full Text












A SEED TRANSPORT AND DELIVERY MECHANISM FOR THE REVOLVING
SPADE PLANTER












By

JEMAN YEON


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENT FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA


2000















ACKNOWLEDGMENTS


I would like to express sincere appreciation to Dr. Lawrance N. Shaw for his

guidance, insight, and patience throughout my course work and research.

Special thanks go to Dr. Allen R. Overman, Dr. Richard C. Fluck, Dr. William M.

Stall, and Dr. John K. Schueller for their advice on my research as members of the

supervisory committee. In addition to their academic advice, they provided me great

academic experiences in study and research in this institution. I would also like to

acknowledge that all of this academic experience will be a great asset in my life as an

engineer.

Gratitude is expressed to Mr. Ralph Hoffman and Mr. Terry Slean for their support in

fabrication and installation of the research equipment.

I am also grateful to all professors and friends in the Department of Agricultural and

Biological Engineering at the University of Florida who have helped and inspired me

during my study and research.

I sincerely thank my mother and my brother and sisters for their patience and faith in

me.















TABLE OF CONTENTS

page

ACKNOWLEDGMENTS............................................................................................ ii

ABSTRACT......................................................................................................................... v

CHAPTERS

1. IN TR O D U CTION .................................................................................................. 1

2. REVIEW OF LITERATURE................................................................................. 5

2.1 Spade-Punch Planter..................................................................................... 5
2.2 Seed Metering and Transporting Mechanisms............................... ............ 6
2.3 Revolving Spade Planter and its Applications.............................. ........... .. 12

3. THEORETICAL ANALYSIS FOR SEED TRANSPORT AND DELIVERY
M ECHANISM DESIGN ....................................................................................... 17

3.1 Feature of a Revolving Spade Planter with Seed Transport and Delivery
M mechanism ................................................................................................... 17
3.2 Coordinate Frames of the Design.................................................................... 19
3.3 Theoretical Analysis for Feasible Design Cases of Seed Transport and
Delivery M echanism ................................................... .............................. 23
3.3.1 D esign Case I.............................................................................. 24
3.3.2 Design Case II................................................ ........................ 27
3.3.3 Consideration on the Theoretical Analysis for Design................ 33

4. DESIGN OF A SEED TRANSPORT AND DELIVERY MECHANISM
M O D EL ............................................................................................................... 37

4.1 Principle Methodology in Design............................................................ 37
4.2 Model Design and Preparation for Experimental Evaluation....................... 44

5. RESULTS AND DISCUSSION......................................................................... 60















6. CONCLUSIONS................................................................................................... 86

7. RECOMMENDATIONS FOR FUTURE STUDIES............................. ............ 88

APPENDIX A. COORDINATE TRANSFORMATION ............................................ 90

APPENDIX B. SOLUTION OF THE DESIGN CASE II ......................................... 92

APPENDIX C. SOLUTION FOR THE COORDINATE (x2, Y2)............................... 94

APPENDIX D. SEED MOTION IN GROOVE AND DELIVERY INTO SPADE....... 97


REFEREN CES ........................................................................................................ 117

BIOGRAPHICAL SKETCH.......................................................................................... 119
















Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirement for the Degree of Doctor of Philosophy

A SEED TRANSPORT AND DELIVERY MECHANISM FOR THE REVOLVING
SPADE PLANTER

By

JeMan Yeon

December, 2000

Chairman: Lawrance N. Shaw
Major Department: Department of Agricultural and Biological Engineering

A major objective of this study is to develop a seed transport and delivery

mechanism for the revolving spade planter for higher speed planting operations.

Based on the theoretical analysis of possible design cases for the planter concept, a

suitable transport and delivery mechanism was developed for the current design of the

revolving spade planter. The design planting speed for the planter was 5 MPH which was

higher than any other current revolving spade planter can successfully plant.

The experimental model was built and evaluated for the design planting speed. The

evaluation results showed that the design concept was suitable for the speed range up to

the design planting speed. The design method could be applicable to the revolving spade

planter at a higher planting speed.














CHAPTER 1
INTRODUCTION



Seeding methods have been developed to achieve a high yield in food production.

Applications of planting techniques have been concerned with the appropriate selection

of farming operations such as tilled or untilled planting and random or precision planting.

Drilling has been a widely used technique to deposit seeds into furrows opened by tools

such as shoes, discs, or packer rings. Broadcast-seeding has been used to place seeds

randomly over relatively wide areas. In most applications of broadcast-seeding, a

secondary tillage is necessary to cover the seeds with soil.

The improved performance of seed providing better germination and emergence, the

increased cost of seed, and the desire to eliminate overplanting and thinning have resulted

in the need for precision planting. Thus, precision planting could be one of the most

important operations for maximum yield and minimum costs. Precision planting is

referred to as accuracy in seed metering, planting depth control and spacing. Precision

drilling is an example of precision planting applied to crops planted in rows. Vegetable

and small grain production have been the object of studies and experiments in the

technology of precision planting (Giannini et al, 1967). An advancement in precision

planting has come with the development of punch planters equipped with plungers,

dibbles or spades. An early type of punch planter was a plunger type which has been

1










studied experimentally on spacing and depth control (Sawant, 1972). A development in

precision planting which could be applied to various types of crops is the spade-punch or

revolving spade planter (Shaw and Kromer, 1987).

The revolving spade planter has several design characteristics needed for precision

planting. The revolving spade planter has the ability to open or dibble holes to the

appropriate depth and spacing and to deposit seeds, which is significant to achieve the

uniformity of crop growing, the elimination of overplanting, and the reduction of thinning

operations. With the improvement of seed quality, the preparation of seed beds or soil

holes by planters might be as important as to achieve the desired germination and

emergence after planting. Desired conditions for seeds placed in the beds or soil holes are

proper contact between seed and soil which is necessary for water movement and

sufficient oxygen supply to seeds. The development of a well prepared soil hole by the

spade planter design (Shaw and Kromer, 1987) is explained in figure 1.1. The bottom

area of the soil hole where the seed is placed features a zone of a not-compacted but

simply cut smooth surface (Zone 1) and a zone of a slightly compacted soil surface (Zone

2). Zone 1 is useful to provide a good soil-seed contact with enough water movement to

seeds under normal soil-moisture conditions. Zone 2 is extremely important to provide

enough water movement to seeds under dry weather conditions. These two important

zones are obtained by the revolving spade planter constructed with the yaw angle (Shaw

and Kromer, 1987).

Most of the research on this type of planter has been focused on the design of spade-

punches and applications of commercially available seed metering devices. To extend the






























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performance of the spade-punch planter to the level of high speed precision planting, it is

necessary to study seed transport and delivery mechanisms to get the desired number of

seeds singulated from a seed hopper and transported to the soil opening spade. And also,

it is desired to minimize the number of moving parts on the planter; especially moving

parts like doors or valves that contact the soil.

The objective of this research is to combine a seed transport and delivery mechanism

with a revolving spade planter for high speed precision planting operations. The

mechanism will be conceptualized and studied theoretically to find the most appropriate

design. The design model will be tested to evaluate the design concept. The major

objectives include the following;

1. Theoretical analysis of the design concept of a seed transport and delivery mechanism.

2. Experimental model design of the seed transport and delivery mechanism for a

revolving spade planter.

3. Experimental evaluation of a design model.














CHAPTER 2
REVIEW OF LITERATURE



Planters have three major functions: soil opening, seed metering and placement and

seed covering. Precision planting has adopted two different concepts of soil opening:

furrows and holes (Kromer et al., 1987). Kromer et al. (1987) reported a hole seeding

method originated from the principle of hand seeding where seeds were pushed into the

soil. The hole seeding method was also considered to have advantage over the furrow

seeding method from the points of view of uniform seed spacing for planting into plastic

mulch (Shaw and Kromer, 1987). Seeding tools such as the plunger, dibber, punch or

spade have been used for hole seeding (Debicki and Shaw, 1996). Several dibble and

punch planters have been developed (Heinemann et al., 1973) including the spade planter,

and the latter concept will be addressed in the research.



2.1 Spade-Punch Planter

The design concept was called the revolving spade planter which was the application

of a new hole forming system (Shaw and Kromer, 1987). They reported that spades were

mounted perpendicular to the axis of the planter wheel to open the soil and form the seed

cavities. And also they suggested that the axis of the planter wheel be designed to be

inclined on an angle of 30from the vertical in order to mount a seed metering device as

5










closely as possible to the spades and to facilitate the penetration of the spades into the

soil. The most significant feature of the design was the yaw angle 7 of the planter disk

wheel. This yaw angle caused cavities for seeds to be formed in the soil and prevented the

dragging of seeds out of the dibbled holes when the spades withdrew from the soil. Based

on their theoretical analysis and model test on the concept about the yaw angle, a cavity is

formed into the cross-sectional shape of the end of a very thin ellipse as described and

referenced in figure 2.1. The cavity created by the spade was reported to provide a good

soil-moisture environment for seeds as described and referred to in chapter 1 using figure

1.1 .To simplify the design and construction of the planter, the inclination angle of the

planter disk wheel from the vertical might not be necessary if a seed metering and

transport mechanism was made as a part of the body of the planter disk wheel. The

CENTRA-FLO planter (anonymous, 1978) is an example of a planter whose seed

metering mechanism could satisfy the necessity of zero angle of the inclination. The

mechanism is called gravity ejection where seeds are metered by a stationary pick-up ring

on a rotating disk and transported while falling freely by gravity inside the rotating disk

grooves to be eventually released into a furrow. The seed spacing on this device can not

be easily adjusted and the machine is expensive, so it was not available for evaluation as

a delivery system for the revolving spade planter.



2.2 Seed Metering and Transporting Mechanisms

Seed metering (Srivastava et al., 1993) is accomplished by two functional processes,

which are metering rate, referring to the number of seeds released per unit time from a























\ Spade




\ hel


\
Seed



0 I Displaced Soil
0


Elliptical Path
of Spade


Open Gate
Area


Figure 2.1 Rear view of revolving spade planter soil opener(Shaw and Kromer, 1987).


\










seed container, and singulation, referring to individual seed placement into soil at proper

spacing. Early mechanisms for metering seeds adopted the principle of regulating the

volumetric flow rate by changing an orifice size (Srivastava et al., 1993). Usually metered

seeds are discharged and flow by gravity into a tube leading to the furrow. The fluted

wheel has been used as a seed metering mechanism for the drill seeder (Srivastava et al.,

1993). The flow rate of seed in the mechanism is controlled by an adjustable gate and the

effective width of the fluted wheel or by the rotating speed of the fluted wheel which is

positioned at the bottom of a seed container. The double-run or internal force feed

mechanism (Srivastava et al., 1993) has also been used for grain drills. The rotating rim

disk with corrugated inner surface carries seeds from a hopper into a delivery tube in

which seeds flow by gravity.

An application of the principle regulating the volume flow rate to planter design had

to be changed with the introduction of precision planting which was critical in the

production of vegetable crops. This led to the development of new seed devices (Giannini

et al., 1967) for metering individual seeds. As a first generation of individual seed

metering mechanisms, seed plate hoppers had been used to meter individual seeds for

precision planting (Richey et al., 1967). Various types of seed plates inside the hopper

could be installed to meter seeds. The metering device was classified by the type of plates

which were vertical, inclined or horizontal. The metering rate in this mechanism might be

considered to be controlled by volume even with improved control methods. As

technology progressed, the finger pick-up planter (Anonymous, 1968) might be

recognized as plateless seed planter which was found to be suitable for planting corn and










other large seeds. Each spring-loaded finger mounted in a rotating disk inside a seed

hopper picks up seeds in the bottom of the hopper and only one seed among all the seeds

is then passed on as the finger is pushed and held in an indentation of a stationary disk

onto a seed belt to be dropped into a seed tube. The rest of the seeds on the finger are

dropped and remain in the hopper. This design concept using rotating seed fingers is

found as a different form in a recently developed seeder (Chang et al., 1998) in which

seed holes or seed loading cells were adopted to pick up seeds.

The air planter (Anonymous, 1971) was also introduced and this featured a

pressurized-perforated seed drum running at approximately 35 rpm that singulated seeds.

Seeds flowing from a hopper into the drum are held at a shallow depth at the bottom of

the drum. Each seed orifice on the inner surface of the drum holds a seed by differential

pressure until it is released into a seed tube with the help of an external wheel which

blocks the orifice on the drum, removing the differential pressure. Other plateless planters

were developed about this time including the pressure-disk planters which were equipped

with separate seed reservoirs for each planting row. Giannini et al.(1967) reported this

design concept and the development of a vacuum seed metering mechanism where the

pressure differential was provided by vacuum. The major objective in the planter

development has been to improve the pick-up effectiveness of the vacuum metering

device for small, irregularly shaped seeds. Vegetable crops such as lettuce were difficult

to meter because small orifices were easily clogged by particles of dust or materials on

seed and caused the seed held on the small orifice to be easily dislodged. On one design

the orifices were like hypodermic needles which could be easily matched to the size of










the crop seeds. The vacuum pressure mechanism was designed so that each orifice was

independently connected to its own vacuum pressure pump cylinder (Giannini et al.,

1967). And also they demonstrated a unique feature of the design of a seed positioning

wheel which lifted seeds from the hopper to locate the seeds on each orifice to minimize

the seed dislodgement from the orifice. The minimization of seed dislodging tendency

was achieved by minimizing the relative velocity between the orifice and the seed.

Moysey et al. (1988) suggested that volume flow rate provides a better comparison

than mass flow rate because of the difference of bulk density in different kinds of seeds.

They reported empirical volume flow rate equations according to the design

characteristics of hopper and orifice. They obtained the empirical volume flow rate

equations for circular, square and rectangular orifices centered at the flat bottom of

hopper as


Q= -2.05+ 46.21A, gDv (2-1)

and for circular, square and rectangular orifices adjacent to the wall of a flat-bottom

hopper as

Q = -2.20 + 53.04 A. gsD (2-2)

where Q = volume flow rate from orifice of hopper (liter/min.)
A, = net effective area of orifice (mm2)
De = hydraulic diameter of orifice (mm)
g = gravitational acceleration (=9801 mm/sec.2)

The application rate in planting operation by volume metering is obtained by the

following equation (Srivastava et al., 1993):











10000ooooQp
R, WV (2-3)

where R, = seeding rate (kg/ha)
Q = flow rate of seeds from the metering unit (liter/sec.)
ps = seed density (kg/liter)
W = width of coverage of the planter (m)
V = travel speed of planter (m/sec.)

The volume flow rate for the fluted wheel (Srivastava et al., 1993) is suggested as


Q = (2-4)
60* 106

where Q = volume flow rate (liter/sec.)
Vc = volume of each cell (mm3)
= number of cells on periphery of fluted wheel
n = rotational speed of fluted wheel (rpm)

For an individual seed metering mechanism, the theoretical seeding rate is given by the

following equation (Srivastava et al., 1993):

10000
Rs = (2-5)
WXS

where Rt = theoretical seeding rate (seeds/ha)
W = row width (m)
Xs = seed spacing along the row (m)

For the equation (2-5), X, is obtained as

60V
X = (2-6)
ACn

where V = travel speed of planter (m/sec.)
kc = number of seeds delivered per revolution of the metering device
n = rotational speed of metering device (rpm)










Many seed transport mechanisms utilize vertical delivery tubes to carry seeds from

the seed meter to the soil opener. On broadcaster seeders, the seeds must be delivered in

the horizontal direction and it is necessary to consider the effect of friction between seeds

and the surface on which seeds contact (Srivastava et al., 1993). The theory of seed

transport for the broadcaster seeders was reported by Cunningham (1963) and Pitt et al.

(1982). If seeds are transported from the hub of a revolving spade planter, friction must

be taken into consideration.



2.3 Revolving Spade Planter and its Applications

The first spade-punch planter, the revolving spade planter developed by Shaw and

Kromer (1987), has been a model to study precision planters by researchers and

manufacturers for vegetable production and no-till field grain seed planting. Debicki and

Shaw (1996) developed a spade-punch planter which was equipped with a commercial

vacuum seed meter. The unique feature of this spade-punch planter was found in the

shape of the spade-punch, which was prismatic in shape with a rectangular base. The

prismatic shape was developed by analyzing the motion of the seed from the seed meter

to the spade. The partial opening in the base of the punch was used to deposit seed into

the soil opened by the side motion of the punch, which was caused by the yaw referred to

by Shaw and Kromer (1987). In the research, the mounting position of the vacuum seed

meter was experimentally optimized relative to the punch (Debicki and Shaw, 1996).

Molin (1996) reported on research of a spade-punch planter for no-till operations with a

study to optimize the shape of the spade-punches. He particularly studied the width of the








13

punch to minimize the penetration force. He suggested empirical equations of penetration

force for the spade-punch 30 mm wide as

= 12627+0.919*In(PFI)
PF =e (2-7)

and for a 60 mm wide spade-punch wide as

P2.0317+0.8791n(PFI) (2
PF = e (2-8)

where PF = penetration force of the spade-punch (N)
PF1 = penetration force of cone penetrometer (N)

He confirmed that the design concept of the 7 yaw angle (Shaw and Kromer, 1987) was

a key design factor to avoid soil adhering to the internal wall of the punch in no-till sandy

loam soil. He also reported that the planter wheel's inclination angle of 22 was optimum

in forming a good shape of hole in no-till sandy loam soil, as compared to the 300

inclination angle reported for wet and tilled rough clay soil (Shaw and Kromer, 1987).

Studies on the spade-punch planter have been focused on improving and applying the

design model of Shaw and Kromer (1987) in the areas such as soil opening and

deposition of seeds in various field conditions. Other aspects such as seed metering and

transport method, hole shape design, soil deformation in the soil zone created by the

spade- punch, and seeding depth control mechanism have been pursued in the studies of

the spade-punch planter for high speed precision planting operation by the following

researchers. Pearce et al. (1996) reported research results about the dibble shape and

depth on the germination and spiral root development of burley tobacco seedlings. They

evaluated both pyramid and dome shapes of dibbles. The treatment using the dome

shaped dibble at a depth of 0.5 to 0.75 inch gave good germination with the least spiral










root incidence. Sawant (1972) suggested that the draft required to operate a planter

equipped with plungers shaped as long solid rods attached on a wheel be obtained by the

equation as

T+_ A rh
H= i + + dz (2-9)


where H = draft (N)
T, = torque due to friction on cam ring holding plungers (Nm)
T2 = torque due to metering device (Nm)
r, = radius of the planter wheel including plungers (m)
A = area of plunger face (cm2)
L = plunger spacing (cm)
h = depth of penetration (cm)

J0h pdz = area under the curve of soil resistance versus depth (N/cm)

He also observed that the moisture transfer was improved in the compacted soil zone

compared to the undisturbed soil zone and the evaporation above the seed was not

reduced, particularly when the hole was only partially filled with soil.

The effects of seeding depth and the depth of soil cover in using a drill seeder were

reported by Rainbow et al. (1992) and McGahan et al. (1992) in grain farming. Rainbow

et al. (1992) studied the relationship of grain yields with seeding depth, soil cover depth

and firming, and correct seed placement using different types of soil openers and press

wheels with planters. They reported that optimum seeding depths were similar in all types

of soil openers but soil firming pressure was significant for the improvement in

emergence and plant growth with increased seeding depth, particularly when the seed bed

was left very loose by soil opening. McGahan and Robotham (1996) reported an

empirical equation as a function of planting depth to estimate potential yield of wheat as










the following:

y = 59.16+ 20.67x 0.16x2 (2-10)

where y = wheat yield (kg/ha)
x = planting depth (mm)

From the potential yield estimation function (2-10), the maximum yield could be

evaluated. They used nine drill seeders in the experiment to measure the seeding depth,

which was found to be highly variable, ranging from 30 to 100 mm from a planter, on a

number of different machines in different soil types.

Kromer et al. (1987) reported that the planting spacing in a planter utilizing the

principle of the hole seeding system could be calculated by the following equation:


2;r (R, S)
PDth = (1 ra) (2-11)
N

where PDt, = theoretical plant distance in the row (mm)
R = peripheral radius of the imbedding element (mm)
SD = seeding depth (mm)
N = number of seeding tools in effect on the periphery
a =slip

They also suggested a modified equation for plant distance considering the factors such

as germination rate, machine function and field factor affecting the plant distance as

PDSe = GR* F PD,, (2-12)

where PDeff = average of the actual plant distance distribution (mm)
GR = germination rate
Ff = field factor
PDt, = theoretical plant distance in the row (mm)

The method to measure the accuracy in planting spacing for planters using a single seed










metering device was suggested by Kachman and Smith (1995). They reported the

statistical measures such as the mean, standard deviation, quality of feed index, multiple

index, miss index and precision. Among those measures, they reported that the mean and

standard deviation were inappropriate as tools to indicate accuracy. They referred the

quality of feed index to the percentage of spacing more than half but no more than 1.5

times the theoretical spacing, the multiple index to the percentage of spacings less than or

equal to half of the theoretical spacing, the miss index to the percentage of spacings

greater than 1.5 times the theoretical spacing, and the precision to a measure of the

variability in spacing between plants after accounting for variability due to both multiples

and skips.














CHAPTER 3
THEORETICAL ANALYSIS FOR SEED TRANSPORT AND DELIVERY
MECHANISM DESIGN


3.1 Features of a Revolving Spade Planter with Seed Transport and Delivery Mechanism

The general design of the spade-punch planter for this study was developed from the

version of the revolving spade planter of Shaw and Kromer (1987). Figure 3.1 shows the

concept of a revolving spade planter for this study with the hub, seed path groove and

seed pocket as a seed transport and delivery system and with the spade-punch as a seed

placement system. The seed transport and delivery mechanism could be embedded in the

body of the planter wheel disk. This could make it possible to eliminate the inclination

angle from the vertical of the first version for structural design simplification.

Another advantage of delivering the seed to the wheel at the hub would be the

elimination of the problem of synchronizing the seed drop with the movement of the

spade as was the situation with the design used by Debicki et al. (1996) and Molin

(1996). With these earlier designs, desired seed delivery was only achieved within a

certain range of planter speed without adjustment of the seed drop timing. Since there is

only relative rotational motion between the planter frame and the wheel at the hub, it was

decided to explore the possibility of delivering the seed to the wheel at the hub and then

transporting it out radially on the wheel to each spade. The planter wheel disk is ground

driven with the angular velocity o following the towing velocity V, of a tractor. The













18

























E0




aa














Cd)
U d, U



b c 00-1














bto
al I QEE -iU








19
towing velocity VT is assumed to be constant, which results in a constant angular velocity

co. The individual seeds metered inside the hub as shown in figure 3.1 enter into the path

groove with a small velocity to slide down to the spade. It was initially desired to drop the

seed directly from a seed groove into a spade when the latter was at maximum soil

penetration. It was desired to transport the seed from the hub to the spade in possibly a

quarter revolution of the wheel. After some preliminary analysis, it was found that this

was not possible over a wide range of planter speeds, so it was decided to explore the use

of some type of "seed pocket" that could receive and hold a seed near a spade and have it

positioned to drop into the spade at the time of maximum soil penetration.

The initial velocity of the seeds at the moment when the seeds move into the path

groove is assumed to be nearly zero in the following design analysis. Since the hub and

path groove are embedded in the whole planter disk wheel rotating with the angular

velocity o, the hub and path groove are also rotating with the same angular velocity as the

planter wheel disk. The sectional width of the path groove is wide enough to

accommodate the largest seed. The seeds are assumed to keep contact with the surface of

the groove without bouncing in order to prevent being damaged while they are moving

through the groove to the seed pocket.



3.2 Coordinate Frames of the Design

Figure 3.2 shows coordinate systems related to the planter wheel traveling on the

ground. The XiYZ, coordinate system is a fixed reference frame on the ground. The non-

rotating XYZ coordinate system yawed with angle y about Y, is translating from the

















A










3 / ~ E

I!f


*1

2 4C4
K I Hi
* -*
g I.
a -~
/ i
/ v
V






0 V


if C.-








21

X,YZ, coordinate frame with the traveling speed, VT, of the planter. The xyz coordinate

system is rotating with angular speed co about z or Z axis on the XYZ coordinate system

and translating with the traveling speed, V,. The xyz coordinate system is embedded on

the planter wheel disk. Since the seed path groove on the planter wheel disk is designed

in terms of the xyz coordinate system, it is necessary to define the coordinate systems

related to the seed and planter wheel motion. As shown in figure 3.2, the planter wheel

disk is positioned with a fixed yaw angle y about the towing direction X, in the moving,

translating only, reference frame XiYZ, where the axis X, is parallel to the ground

surface and assumed to be horizontal. The origins of the coordinate systems of XY,Z,,

XYZ and xyz are made to coincide as denoted by O in figure 3.2. The rotating angle 0 of

the xyz coordinate system about the XYZ coordinate system is measured between the x

and X axes and between the y and Y axes. When the rotating angle 0 is equal to zero, it is

assumed that the inlet of the path groove is positioned on the Y or y axis and the seed

should start moving into the inlet with zero initial velocity. Thus, the coordinate

conversion between the coordinate systems XYZ and xyz is obtained as the following

(refer to appendix A):

X cos0 sin90 0 x
Y sin cosO 0 (3-1)


or

x cos0 sin f 0 X
y = -sin0 cos 0 (3-2)
z 0 0 1 Z











Assuming that the planter wheel disk is rolling without slip, the angular velocity o of

the planter wheel disk is expressed as


d) (3-3)
Reff cosy

where o = angular velocity of the planter wheel disk (rad/sec.)
VT = towing velocity of the tractor (m/sec.)
Rff = R Dp, effective radius of the planter wheel disk (m)
R = radius of the planter wheel disk (m)
y = yaw angle (rad)
D, = seeding depth (m)

The towing velocity for planting operation is assumed to be constant, which results in the

constant angular velocity of the planter wheel disk. Since the slip was assumed to be zero,

the planting spacing regarding with equation (2-11) is obtained as, referring to figure 3.1,

2l(R- D,)
Sp = N p (3-4)
N,

where Sp = planting spacing (m)
R = radius of the planter wheel disk (m)
Dp = seeding depth (m)
N, = number of spade punches of the spade punch planter

A theoretical analysis for the seed metering and transport mechanism is particularly

focused on obtaining the most appropriate shape of the seed path groove since a high

speed planting operation with the design concept as shown in figure 3.1 depends on

whether the seed could be transported as quickly as possible from the inlet of the groove

to the spade. Thus, the path of the seed should be designed to transfer the seed from the

inlet to the spade in the shortest time under gravity. The seed is assumed to enter

downward into the inlet of the groove with zero or very low initial velocity when the inlet









is positioned on the Y axis in the positive direction of the axis. The seed sliding on the

surface of the groove is assumed as a particle. The air resistance on the seed will be

ignored in the following analysis (refer to table 18.1 on page 188 ofRichey et al., 1961).

One of the most important features in the revolving spade planter is the concept of the

yaw angle y mentioned with figure 1.1 for the formation of soil hole. To describe the

motion of seed and revolving spade, it is necessary to convert the coordinate of the

relationships expressing the motion. With the existence of the yaw angle, the coordinate

systems of XYZ and XY,Z, are converted in a similar manner referring to appendix A as

X cosy 0 sin7 X
Y$ = 0 1 0 (3-5)
Z, -siny 0 cosy Z

Thus, the coordinates between xyz and XYZ, are transformed using the relationships of

(3-1) and (3-5) as

Xl cosy cos -cosysin9 siny ]x
S= sinO cosO 0 y (3-6)
Zl -siny cos0 siny sinI cosy z




3.3 Theoretical Analysis for Feasible Design Cases of Seed Transport and Delivery
Mechanism

The design of a seed transport and delivery mechanism was intended to achieve a

higher planting speed than was possible when seeds are dropped directly into the spades.

It is desirable to transport metered seeds in the shortest time from an initial position at the










hub to a final position at the spade for a higher planting speed. This path from an initial

position to a final position was mentioned as the path groove on the planter wheel disk in

figure 3.1. The path can be described as using design data in the xyz coordinate system.

When the seed path is observed moving with the same traveling speed, it can also be

described using the XYZ coordinate system. The observation of seed motion in the XYZ

coordinate system can be transformed by the relationship (3.2) to determine the actual

design data for the seed path groove. While the initial position in seed motion is fixed to

the inlet of the seed path groove, the final positions could be considered in various ways

from engineer's point of view. The first possible final position could be considered a

point on Y axis as shown in figure 3.3 to obtain a path of the shortest time, which is noted

as design case I. But the second final position could be considered a point on the fourth

quadrant as shown in figure 3.5 to determine a path of shortest time, which is noted as

design case II. These two feasible cases of design will be considered to determine the best

way of design in terms of accuracy in delivering seed into a soil hole and advantage in

design and fabrication.



3.3.1 Design Case I

Since the final position was selected as a point on Y axis in case I, the solution for a

path of a shortest time between the initial and final position is a straight line which is a

straight line on Y axis. Thus, the particle motion should be a free fall under gravity

without any resistance such as friction between the particle and the path. The straight line

is observed on XYZ coordinate system and it should be transformed into the xyz













25


















IN


etc



















C)
wl,















rnU




8A
4-4cca
0



o
Aa










coordinate system using the relationship (3-2) for designing the seed path groove. The

first case in design is described in figure 3.3 as the concept that seed entering into the

inlet of the path groove falls freely to the final position which could be an inlet position

of the spade. The seed enters the groove with zero initial velocity when the inlet reaches

the positive side of Y axis. In this case of design, the seed would reach the final position

when the corresponding spade is fully penetrated into soil. Thus, the seed would be

deposited into the soil hole during the time the spade is withdrawing out of the soil.

Since the seed falls freely under gravity, the acceleration of the particle is equal to the

gravitational acceleration, g. The velocity of the particle, Vp, observed in XY coordinate

frame is obtained by integrating the acceleration as

V,p= fgdt=gt+c, (3-7)

where Vp = particle velocity at time t
g = gravitational acceleration (9.801 m/sec.2)
c, = constant of the integration which is equal to zero by the condition of zero
initial velocity of the particle

Since the motion of the particle was assumed as a free fall with referring to figure 3.3, X

coordinate of the particle position, (X,Y), is equal to zero. And Y coordinate of the

particle position at time t is given as

Y= Vdt
1 (3-8)
2gt2 +c2

where the integration constant c2 is determined using the initial value of Y.

Since the initial position of the particle is equal to Rh of the hub radius, the constant c2 is

also equal to Rh. Therefore, the position coordinate, (X, Y), of the particle at time t is










obtained as

X=0
1 (3-9)
Y= -gt2 + Rh

The seed path in figure 3.3 is obtained by the coordinate transformation using the

relationship (3-2) using the coordinate, (X, Y), of equation (3-9) as


x(t) = (Igt2 + Rh)sinO
2 (3-10)
y(t) = (Igt2 + Rh)cos

where 0 is equal to cot for constant angular velocity of the planter disk wheel. The

solution for case I is shown in figure 3.4 at various traveling speeds. The time

required for seed to move from the inlet of the path groove to the spade is obtained from

equation (3-9) as

t, = 2(R, R)/g (3-11)


where t, = traveling time of seed from the inlet to the spade in design case I (sec.)
R = radius to the position of the seed pocket (m)
Rh = radius of the hub, as shown (m)
g = gravitational acceleration (9.801 m/sec.2)


3.3.2 Design Case II

Figure 3.5 describes the concept of the design of the seed path groove where the seed,

particle, slides into the inlet of the path groove with zero initial velocity to reach the

spade. The effects of sliding friction and air resistance on the seed are ignored. And also

the seed is assumed to reach the spade when the corresponding spade is about to contact

























C
.a .C -a .E



a E ES
00 0 r o












E-~ 000.2'.









cc
I I:








b0




























I . ... .. .
... . ... ..:. . .. C

. . .. . C r > v

0 Nr Cs
C~l M C- "I








29
the ground surface to penetrate into the soil. The path of the seed motion is designed for

the seed to move from the inlet to the spade in the shortest time for the high speed

planting operation. In this design, the seed could be deposited in the opened soil hole

before the spade starts to withdraw out of the soil, which is an advantage in terms of

simple construction design of the planter.

The path observed on xy coordinate frame is the seed path groove, and the path

observed on XY coordinate frame might be a curved path shown as the dotted curve in

figure 3.5. Since the surface of the groove is assumed to be frictionless, the normal force

N acting on the particle does not constrain the analysis of the motion. Figure 3.5 shows

the particle motion observed in XY coordinate frame. The curved path shown as the

dotted curve in figure 3.5 is shown in figure 3.6 with normal and tangential coordinates to

the path curve. Since the path, the seed path groove, was intended to have the feature that

the traveling time of the particle motion on the path should be minimized, the particle

motion observed on XY coordinate frame should be completed in the minimum time.

From the particle motion in figure 3.6, Newton's law of motion gives an equation as

dV
d gsina (3-12)

Substitution of the relationships as

dY
sina
dS (3-13)
dS
dt

into equation (3-12) and multiplying V on both sides of the equation (3-12) gives the








































P)L

o ,~
Ch
cry









































CU

Cu
0*-

C.


0:

0








32
relation as

d dY
(V)= 2g (3-14)
dt dt

Integration of equation (3-14) with the initial conditions of

V(t = 0) = 0
(3-15)
Y(t = 0) = Rh

gives the relationship for the velocity as

V= /2g(Y- Rh) (3-16)

which could be also obtained from conservation of energy. The traveling time from the

inlet to the spade is given as


= 2dt (3-17)


where J = traveling time from the inlet to the spade
t, = time measured when the particle enters into the inlet, considered to be zero
t = time measured when the particle reaches the spade

Using the following relationship as



dS + dXX
dt = ( R (3-18)
V 2g(Y-Rh)

since the differential arc length, dS, of the path is given as dS = dX2 + dY2 the


functional (3-17) can be written as











J = -dX (3-19)
Jo 2g(Y- Rh)

where the coordinate (X2, Y2) as in figure 3.4 for the final position of the particle is used.

Therefore, this design problem is formulated as the following optimization problem:


Sx, Vl+ y2
minimize J= J dX (3-20)


where the prime denotes differentiation with respect to X. Referring to appendix B, the

solution for the path of a shortest time in the problem (3-20) was obtained as

Y= Rh + c3(1 cos)
.X=c3(-sin) (3-21)
X=C, (f sincf)

The solution (3-21) for the case II is shown in figure 3.7 compared with the solution for

the case I in an example of a planter disk with radius 305.31 mm (12.02 inch), which

shows the final position close to the Y axis. Both solutions have a common ground that

the particle moves under only gravitational force from the initial to final position. But

they are different only in the assigned final position.



3.3.3 Consideration on the Theoretical Analysis for Design

The final position of the design case II is very close to Y axis as shown in figure 3.7.

In the design case I, the final position is given on Y axis. When the final position is

assumed to be the spade, it could be very difficult to drop the seed into the spade at time

of maximum soil penetration. Probably the seed will not arrive at the exact final position



































u)


U)
N
C\j


No
CD


N -' b

cli

. . .) 4 ) .. .
cu r-





00 W)0







. ..
Ci








0* 1-

I U)
--4



a
M,








........

a) LC)
... ...... *... ...... .. ...... .. ...U)
cts ------

LO
LO U LO O U LO O L 0 L Lo
C CQ C r-.: C








35
at theoretically expected time as desired. The seed could arrive at the final position either

earlier or later. Thus, it could be considered to use some type of "seed pocket" to hold the

seed at the position 1 as shown in figure 3.8. The seed which is held inside the seed

pocket will be contained inside the pocket until the position 2 as shown in figure 3.8. If

the seed pocket has an open side, the seed could slide down on the inclined surface under

gravitational force through the open side. Since it is necessary to control the release

position into the spade, the seed sliding out of the seed pocket should be held on the

inclined surface with the help of a stationary ring as illustrated by position 3 in figure 3.8.

The seed held by the stationary ring will be released at the open end into the spade.

This description of the open and closed side of the seed pocket, the inclined surface

and the stationary ring will be adopted to design a model for this research. Since the final

position of the design case II is very close to Y axis as shown in figure 3.7, it is very hard

to expect that there is enough time to drop the seed into the spade at time of maximum

penetration. There is no great advantage in the design case II over the design case I.

Therefore, design case I will be used to design the seed transport and delivery

mechanism.















4.
g ( .


I *lid is
(B S i c -a A,



W 0 t 0/1 a
~ -1178


Uo g

uI Ig


-g4
u














CHAPTER 4
DESIGN OF A SEED TRANSPORT AND DELIVERY MECHANISM MODEL


4.1 Principal Methodology in Design

The first design parameters to be considered are planting spacing (S,) and planting

speed (VT) for a revolving spade planter. As discussed in section 3.3, the planting speed

could be the maximum speed which would be recommended for any seed planting

operation with the revolving spade planter. Considering the number of spades (Ns,) and

the planting depth (Dp), the radius (R) and the angular velocity (o) of the planter disk

wheel are determined from equations (3-3) and (3-4) as

S, N,
R= + DP (4-1)

2xV,
0 = o(4-2)
S, N, cosy

where R = radius of the planter wheel disk (m)
co = angular velocity of the planter wheel disk (rad/sec.)
VT = planting speed (m/sec.)
Sp = planting spacing (m)
Nsp = number of spades
y = yaw angle (rad)
Dp = planting depth
SpNp = effective wheel circumference

From equations (4-1) and (4-2), the design value of the planting depth is fixed for each

crop. Then, the number of spades would be determined. Figure 4.1 shows the conceptual

feature of a hub in a revolving spade planter. The hub of a radius, Rh, is used to contain a

37








38
seed singulation device from which single or multiple seeds would be released and guided

to move into the inlet of the groove under the assumed zero initial velocity. The hub

radius should be determined considering the dimension of the seed singulation device and

the width (w,) of the groove. And the width and depth (ds) of the groove must be given

depending on the size and the number of seeds to be delivered.

As shown in figure 4.1, design of the groove needs first to establish the coordinates

(x(t), y(t)) the surfaces on which the seeds slide. The coordinates (x2(t), y2(t)) of the

surface on the other side are obtained from equations as (refer to appendix C)

SIGN(tan a2 (t))
x2(t)= x(t)+ w ,s1+
V1+ tan2 a2 ()
(4-3)
tana2 ()
Y2(t)= y(t)- W,
1+ tan a2 2(

where x(t) and y(t) from equation (3-10)
w, = width of the groove
SIGN(A) = +1 when A is positive, or -1 when A is negative
a(t) = the angle in radian at time t between X axis and the normal direction at
the position of x(t) and y(t)

Since a seed pocket is adopted to hold seeds before delivering seeds into the

corresponding spade, the motion of the seeds needs no longer to follow the path defined

by equation (3-10). On the path defined by equation (3-10), the normal force between the

seed and the groove path is zero since the seed is falling nearly free through space.

However, upon entering the new path of the seed pocket, the normal force between the

seed and the contact surface inside the seed pocket could be greater than zero. This

normal force greater than zero could prevent the seeds from sliding forward, which means


















4-

I-
12
0
o
0
o,-







SI Y
I) I





---- I
c I




"-\ \ "-.-.

S o 0. -









4-" 0

0

0
0i I



















0
-- -



Soo



I +0
4-





-a
'i








40

that in a critical situation the seeds might stick to the surface inside the seed pocket when

a centrifugal force is greater than the gravitational force. Therefore, the position of the

seed pocket must be determined to avoid the situation that the normal force between seed

and contact surface inside the seed pocket is greater than zero particularly when seed

might be positioned at the critical position as shown at the top of figure 4.2. The normal

force (FN) acting on the seed at the critical position is obtained as:

FN = mRco 2 mg (4-4)


where FN = normal force acting on the seed at the critical position (N)
R, = radius to the critical position of the seed (m)
co = angular velocity of the planter wheel disk (rad/sec.)
m = mass of the seed (Kg)
g = gravitational acceleration (9.81 m/sec.2)

The seed entering into the seed pocket is observed as a motion following the Y-axis as

discussed in chapter 3. Thus it might be reasonable to make the seeds inside the seed

pocket hold the lower or bottom position inside the seed pocket in any rotating position,

which might be better way to get the seeds ready to slide out of the outlet to be delivered

into the spade. This design constraint could be achieved by determining the position of

the seed pocket to prevent the normal force in a possible critical position of seed from

being greater than zero. Thus, the position of the seed pocket could be determined using

the value of R. from equation (4-4) when the normal force, FN, of equation (4-4) is less

than or equal to zero.

As discussed in the design concept in chapter 3, the seed held in a seed pocket should

be released into a spade at the proper time or position for uniform planting depth. It might











































































0 3
0. zo
> 4 p E


3






























)~x a8


S o 0
/ 0o

/0


F-
U U;










be necessary to release seed at a proper position of the rotating planter wheel disk, for

example a proper angular position (0,) as shown in figure 4.3, to place the seed into a soil

hole opened by the revolving spade. The proper angular position is also related to the

design and construction of a device called the stationary ring shown in figure 4.3 which

would retain the seed on the rotating disk until being released into the spade after sliding

out of the seed pocket. The release angular position (0,) is obtained from the following

relationships (4-5);

X(t) = R, sin 0 Rot cos0,
1 (4-5)
Y(t) = R, cos s + Rct sin 0, + gt2
2

where X(t) and Y(t) = position coordinates of the seed after leaving the stationary ring
observed on X-Y coordinate frame
R, = inside radius of the stationary ring
08 = angle between Y axis and the edge of the stationary ring, which is equal to Otf
where tf is a time measured at the moment of the spade center line passes the
Y axis and time, t, is zero at the moment of the seed leaves the edge of the
stationary ring
o = angular velocity of the planter wheel disk
t = time measured from the instant when the seed is to leave the edge of the
stationary ring
g = gravitational acceleration

Using the relationships (4-5) to obtain a proper value of 0,, some conditions should be

considered for the best planting operation which is satisfied by proper delivery of seeds

into the soil hole opened by a spade. As shown in figure 4.3, the shape of a spade adopted

in this research has a open gate in the opposite side of the spade side face which pushes

the soil to open the soil hole by the function of the yaw angle discussed in section 3.1 and

shown in figure 2.1. The seed moving inside a spade after being released from the










stationary ring must reach the gate area after the gate area is fully engaged in the soil as

shown in figure 4.3. This condition in obtaining the proper value of the angle, 0s, can be

described as a constraint in simulating the relationships of equation (4.5), as illustrated in

figure 4.3, as


X(t)2 + (t2 < (RW d when O(t) > 0 (4-6)


X(t)2 + Y(t)2 (R d ) when O(t) < O (4-7)

X(t) > 0 (4-8)

where R, = radius of the planter wheel disk
dg = open gate height of a spade
0(t) = cot where t is measured from the instant of the seed leaving the edge of the
stationary ring
co = angular velocity of the planter wheel disk
9, = angle measured between Y-axis and the spade center line passing to the center
of the planter wheel disk at the time when the open gate of the spade starts
to be fully engaged into the soil as shown in figure 4.3


4.2 Model Design and Preparation for Experimental Evaluation

As discussed in the design methodology, initial design requirements for a specific

crop should be given for the design of the seed transport and delivery mechanism for the

revolving spade planter. The initial design requirements for a specific crop include a

maximum planting speed (VT), a required spacing (Sp), and a planting depth (Dp). Given

these data shown in figure 4.4, the design could proceed to determine first the radius of

the planter wheel disk which determines the basic shape and size of the planter. The

number of the spade (Nsp) is arbitrary initially in the design process and is determined in

the relation with the width of the spade since there should be enough space between










INITIAL DESIGN DATA :
Planting Speed(VT)
Planting Spacing(Sp)
Panting Depth(Dp)
Number of Spade(N ,)
Hub Radius(Rh) min. and max.
Spade Width(wsP




Compute the Effective
Radius (Rx ) Ns, = Np -1


Nsp = Np/2






of the Planter Wheel Disk


RP = min. ofRP
no ,

e ma Compute the Design Data of the Groove:
-mayesx. (x, y) and (X21 Y2
when R2Z = x2Z + y2Z, (x0, 20) = (x2 y2)


R= Rh= +AR



,bsp tan-'(x20/y2o)> s O



Compute: (x, y), (x,, yz), and (x,, YO)S


Figure 4.4 Design procedure for the seed transport and delivery mechanism.










neighboring spades, which is explained as the relationship;

ebsp > esp (4-9)

As shown in figure 4.5, the angle, Obsp, between the center lines of the neighboring spades

is obtained as

2)r
Obsp = N (4-10)
sP

and the angle, Osp, for each spade is obtained as, considering ground clearance C,,


S= 2smi- (4-11)
2(R, Cg,)

where ground clearance Cg = Rf R, (refer to figure 4.5)
Wsp = the width of the spade
Rff = the effective radius of the planter wheel disk

After the effective radius with the proper number of spades is determined, the angular

velocity of the planter wheel disk is obtained by the relationship (4-2).

The radius, Rh, of the central hub is initially made large enough to accommodate a

device supplying seeds into the inlet of the seed groove. However, as shown in figure 4.1,

since it is necessary to have an appropriate circumferential space where seeds are staying

just before sliding into the groove, the radius of the hub should be determined under the

consideration of the groove width and the circumferential space. The appropriate

circumferential space is described by the angle, 08,, in figure 4.1 which should be

determined and given according to the size and number of seeds supplied into the groove

at one time. If the initial radius of the hub is not large enough to create the required

circumferential arc space as shown in figure 4.1, the radius of the hub should be increased














































-o



U,



U


.. .. .










until it could create the space. To determine the appropriate hub radius, the coordinate

(x2, Y2) for each coordinate (x, y) should be computed using equation (4-3) until the

coordinate has the relationship as


Rh = X2 + Y22 (4-12)


And then, the angle (0,,) is checked as

2r x
= -tan 2 (4-13)


to see whether the angle is enough for a specific seed. For this experimental model design

to use bean and corn seeds, minimum value of the angle (0s,) was 6 considering the size

of those seeds. The seeds' size can be compared with the corresponding circumferential

arc (Sa,) to the angle using the following relationship:

Sarc = OtRh (4-14)

After the hub radius is determined, the seed groove is to be determined by obtaining

the coordinates of (x, y) and (x2, Y2). Next it is necessary to check the critical radius (Re)

in equation (4-4). The possible center position (xos, yo) of the seed pocket must be

determined so the relationship

RC = Rpk + VXo2 + yos2 (4-15)

is satisfied where Rpk is a given radius of the seed pocket. When the relationship (4-15) is

satisfied, the process of determining the shape of the seed groove and the seed pocket

position is finished. For the model design, the following data were used;










1. width of seed path groove: 12.7 mm (0.5 inch)
2. diameter of cylinder hole for seed pocket: 50.8 mm (2.0 inch)

As shown in figure 3.8 to describe an idea of a seed pocket, the seed motion

following the positions which were noted as position 1, 2 and 3 in figure 3.8 could be a

motion following the position p2, p3 and p4 as shown in figure 4.6. The motion following

the position p2, p3 and p4 could be a motion following a spiral. When a seed sliding in

the groove reaches the seed pocket (position p2 in figure 4.6), it should be kept sliding in

the spiral groove under its own gravitational force so it progresses in the positive z

direction as shown in figure 4.6 while the planter wheel is rotating. As it progresses

through the spiral of the seed pocket (from p2 to p3 and from p3 to p4), it reaches an

appropriate position to be released into the exit groove which transports it to the spade. If

the seed arrives prematurely at the radius of the wheel disk, it may be held by the retainer

ring until the appropriate time for it to be released into a spade. After it was concluded

that a seed pocket would be desirable to carry a seed or seeds for nearly three quarters of a

planter wheel revolution until they could be discharged into a spade, the question was

what design would be appropriate. Several features were required for a satisfactory design

and these included simplicity and some means of preventing the seed from falling back

toward the hub when the spade wheel had turned about half a revolution after the seed

initially entered the seed groove. The idea of incorporating a spiral path into the seed

pocket as shown in figure 4.6 was developed. With this design, seed could travel radially

away from the planter wheel hub through a seed groove and enter the seed pocket spiral

while the wheel was turning. In space the spiral would actually rotate and carry the seed



























9<


/ .







o
I:z




a
"\ ^"
I:,
O



U
\0







*.
\ou



': 4)*T
(a









: 5
4
t.. ** ** y IO


..
* / \ "
y~


......................










in the positive z direction and trap the seed so it couldn't fall back toward the hub. The

spiral could be designed so that the seed could be discharged into an exit groove that

would carry it radially out to an individual spade. To provide for timely delivery of the

seed into the individual spades, an adjustable, stationary retainer ring could be used. The

retainer ring provides adjustment of the final drop into each spade.

In model design, a left hand spiral which is shown schematically by a wire frame

model as shown in figure 4.7 and the photo of the solid model is shown in figure 4.8. For

the design model, the following data were fixed to develop the helix:

1. major diameter (Do) = 50.8 mm (2.0 inch)
2. minor diameter (D,) = 19.05 mm (0.75 inch)
3. lead in axial direction for 2700 rotation angle (0), L, = 19.05 mm (0.75 inch)

The shape of helix as shown in figure 4.7 is obtained using the following relationship:

Do
x= cos0
2

Do sin0
y= sm0
2 (4-16)

2 = tan-( )
0.75;rDo
z= 125- Do tan2

where x, y, z = coordinates in figure 4.7
X = helix angle

The left hand screw has 25.4 mm (1 inch) pitch, 9.04306 helix angle and 50.8 mm (2.0

inch) outside diameter with 19.05 mm (0.75 inch) inside diameter.

After the seed moves to the end of the spiral described by the out-direction in figure

4.7, it is necessary that the seed be released to the exit groove. The seed moving into the







































--
o
0
i0









* 2









..


L 1 T- LA 0 LO
c1i 0 r-


z


; : .



/.. ... .

; ; ;-. -;I


/.. .. ..


:


'


~"~""...........


I-








































































1

i








54

exit groove is sliding and reaching to the inside wall of the stationary ring. At the end of

the stationary ring, the seed is no longer retained and is dropped into the open top of the

spade. When the seed is released at the end of the stationary ring, the corresponding spade

is beginning to engage the soil to open the soil hole. The seed released at the end of the

stationary ring is falling free inside the open space of the spade to be delivered into the

bottom of the soil hole. The seed should contact the bottom of the soil hole before the

spade starts to leave the ground after full penetration into the soil, as was discussed with

equation (4-5). The final position of the seed on the bottom of the soil hole after release

from the end of the stationary ring was plotted to obtained a best release angle 0, shown

in figure 4.3. From figure 4.9, the release angle of 31.5 was selected to design the model

for evaluation as shown figure 4.11. This model for the revolving spade planter was

designed using a maximum planting speed of 8.0 km/hr (5 mile/hr), after considering

speeds that many planters operate at of about 4.8 km/hr (3.0 mile/hr). A design for corn

planting was modeled with the plant spacing of 16.5 cm (6.496 in) and the planting depth

of 5.08 cm (2.0 in). The planter wheel disk based on the design featured in figure 4.10 is

shown in figure 4.12 to show all seed path grooves, seed pocket holes and exit grooves.

The planter wheel disk and spade of the working model as shown in figure 4.11 was

fabricated with plexiglas to observe the seed motion. The spiral pocket is made of

"Delrin". The rotating speeds of the planter wheel were adjusted by an electrical motor

driven Zero-Max variable speed drive. The rotating speeds were measured by ZIVY

speed indicator reading by rpm. The evaluation was focused on whether the motion of

seed followed the design concept by examining the video image of the motion. First, an















55






eu!l pl!os tG1eu!pJooo- A
to to to LO LO) t LO to
Co C) c,-c co c t --, Lo t Lo co c6 N C

to

to






LO





to




CV)





.. .. .. ... ... .. .. .. .. .. .. .


Cr) 03 :


.. .. .. . .. C 0




.. .~ . .. .t o.. .
C 0
1 14








..............


.. ... ... ... ... ......
0) S















.. .


.. . .. . .0.


L.)





............ .... .... .. .
to .-



1 C14





















00
ouNl to: to p e
0



U!j P8IO vUpOO-























^"
o
N 0 *S
r~ oi a;

*" m a

rwovo v >r> *
I, II *
^sgS^" ^

II I1 11 I r
^^i^


~...-....................................


co I
.,. 00 N ^OtM
0 00-' %` 9 -
.1
II II.I II
0 a. A 40)v


00
o


















C.,



















It







to
ci
a.)
3








au


















i
o














a)










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r:
o ,3,











57





aa)






~. a)





cFs



Q) )
I-'
0







a- -a



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I-i

4-h
P ~I~~CC~ -C IL% C .
a)P
,~9s~s~8~-~a)
a)

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a)J












58


















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(0





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I.......~! ~ ..........., ,
cr ....... Go


cli
C~ oC/ I D 0 0 j C








59

artificial seed was used for the evaluation. Later seeds including corn and bean were used

to take images of their motion during operation of the apparatus. Since the design speed

was 8.0 km/hr (5 mile/hr), the evaluation tests were conducted with the planting speeds of

8.0km/hr (5 mile/hr), 7.2 km/hr (4.5 mile/hr), 6.4 km/hr (4.0 mile/hr), 5.6 km/hr (3.5

mile/hr), 4.8 km/hr (3.0 mile/hr), 4.0 km/hr (2.5 mile/hr) and 3.2 km/hr (2.0 mile/hr).














CHAPTER 5
RESULTS AND DISCUSSION


Since the seed transport and delivery mechanism was designed based on the

maximum operation speed of 8.0 km/hr (5 mile/hr) for the revolving spade planter, it was

also evaluated at speed ranges lower than the maximum operation speed. The operation

test to evaluate the design concept was conducted with several operation speeds as 8.0

km/hr (5 mile/hr), 7.2 km/hr (4.5 mile/hr), 6.4 km/hr (4.0 mile/hr), 5.6 km/hr (3.5

mile/hr), 4.8 km/hr (3.0 mile/hr), 4.0 km/hr (2.5 mile/hr) and 3.2 km/hr (2.0 mile/hr). The

seed path groove in the mechanism model was first evaluated visually with video images

captured every 1/30 second of the seed movement. The artificial seed was made of a

plastic "Delrin". The sliding motion of the artificial seed following a path in the grooves

was compared to theoretical motion along the Y axis at the design speed of 8.0 km/hr.

The positions of an artificial seed were determined by examining sequential video images

as the seed progressed from the hub to the spiral pocket at a planting speed of 8.0 km/hr.

The path of the seed was compared to the theoretically expected drop and is shown in

figure 5.1. Measurements were made of the Y coordinate position of the artificial seed for

ten passages of the seed and these are given in table 5.1. Figure 5.2 shows the video

images of the motion of the artificial seed at the design speed of 8.0 km/hr. They show

very stable motion following the path groove by moving very close to the Y-axis.













61














-d












A .
So
I TO










E 0o






- - -o
o I G2


























0

"0
I--




IA
-I -i 4 ^ .-













^ '\ -- _




























2 I =
00 0 '-i N





S 0- vi *q 0 0

0 e ?




000


SIf 0 00 I 0









rf -
Soo fm

















N 00 If
o o o '* ^














00 I t 00
S- 00 0 N







00; in ad
g0\ s-


















412 00 0` 0 0 0







H o ?m


b0 0
0006
oEo










00 N o0



as EE 0 E






0 00
e E EE 0
000 0 0 0 00 00
Si li
a s | 5












o4 0 0-S2
^ *" e s c "" ^'
O M r f CB OrC-C r
$g | .^
e c ^ swos- C-s-s
o'^^^^uSa h ?
~~~S3oS0!~N S6
3o oac c o ~e

3 i E~-^ o


= N Y































(1) at time t = 0/30 sec.
(1) at time t = 0/30 sec.


(2) at time t = 1/30 sec.
Figure 5.2 Artificial seed motion at the planting speed of 8.0 km/hr.





























(3) at time t = 2/30 sec.


Seed .-

(4) at time t = 3/30 sec.
Figure 5.2 Artificial seed motion at the planting speed of 8.0 km/hr (continued).




















See (5










(5) at time t = 4/30 sec.


(6) at time t = 24/30 sec.
Figure 5.2 Artificial seed motion at the planting speed of 8.0 km/hr (continued).


Mwww- ) L


~PL~L~'~
/ ----~-"'


f






























(7) at time t = 25/30 sec.
(7) at time t = 25/30 sec.


(8) at time t = 26/30 sec.

Figure 5.2 Artificial seed motion at the planting speed of 8.0 km/hr (continued).































(9) at time t = 27/30 sec.


(10) at time t = 28/30 sec.

Figure 5.2 Artificial seed motion at the planting speed of 8.0 km/hr (continued).
























Seed






(11) at time t= 29/30 sec.


(12) at time t = 30/30 sec.

Figure 5.2 Artificial seed motion at the planting speed of 8.0 km/hr (continued).































(13) at time t = 31/30 sec.


(14) at time t = 32/30 sec.

Figure 5.2 Artificial seed motion at the planting speed of 8.0 km/hr (continued).








70

The positions of the artificial seed were measured from the center of the hub at each

time as in figure 5.1. The differences between the theoretical distances and the mean

distances in table 5.1 suggest some contact between the artificial seed and the groove

surface, particularly at the time frame of 3/30 second. As discussed in chapter 3, the seed

motion on the groove surface was expected to have a nearly zero normal contact force.

The difference between the theoretical value and measured value of the travel distance

could be understood as some existence of contact between the seed and the sliding

surface of the seed path groove. From table 5.1, the maximum mean difference from the

theoretical position is 3.5 mm (0.138 inch) for the position at time t = 3/30 sec. This

difference of distance is equivalent to seed moving time difference of 0.004 sec, which

could be considered acceptable. Based on the observation that the final motion of the seed

entering into the seed pocket was timely, the difference might be acceptable. Entering

motion into the seed pocket with the error of 1.954 % might be understood that seed

could avoid some damage caused by bumping or bouncing off possibly caused by

untimely entering into the seed pocket. The seed motions during the remainder of the tests

at lower operation speeds are referred to appendix D, which show an existence of sliding

motion under the positive normal force between the seed and the groove surface as

expected in the design analysis from figure 3.4.

In order for the seed to be placed into the soil hole without being damaged, the seed

should be released into the spade from the end of the stationary ring before the center line

of the spade leaves the Y-axis as shown in figure 5.2. As in the photographs of figure

5.3, the seed is observed to reach the bottom line of the spade before the spade reaches














71



x

C* C






(u
__ __M_ __ (0d ''







. .. C )












.
....... ........














-o ~
. . I


. .. .
vv















.. .
HIC\ l


















. . CO
cli
















C0D 0 w to 04N 0 N l CD co 0 N Q- C.0
i -
A~





















0 P


N4-* C4. *4 -t *1



OX + vvo D I


. .... .. ....... .. .. .. .... .... .....




\ \ x .



.-.. \ .: .
.\ .*X \ .X\
\.
: ,'. ...* ..* *"





~... ;...' x \
\ .
f.\ .:.. "N









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: i it


0(0

o


0

C,



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o
c c


0 '






S





>T


r


. . : .. :
.. .










maximum penetration in the soil. This observation could be interpreted as a satisfactory

delivery and placement of the seed into the soil hole. In figure 5.3 the seed motion after

release from the end of the stationary ring are in good comparison at each corresponding

position with the theoretically expected positions. Figures 5.3 and 5.4 show data plot

from the evaluation of seed delivery into the soil hole after seed release from the end of

the stationary ring at the design speed. The data plot on figure 5.4 shows that data of the

evaluation test spreads within the range of 5% (dashed line plot) from theoretical

expectation (dotted line plot).

The design of the seed metering mechanism was based on assuming a seed as a

particle as discussed in design analysis of chapter 3. However, crop seeds are all different

and irregular in shape. Thus, tests at a design speed of 8.0 km/hr (5 mile/hr) were also

conducted to see the versatility of the performance with crop seeds as shown in figure 5.5.

The bean seed is similar in shape to the artificial seed in dimensions and weight. But the

corn seed is very irregular and flat in shape. The lettuce seed was considered but was not

tested because of its size. The lettuce seed which is tiny, needle-like and light weight

might be applicable to this mechanism if coating on the seed changes the shape. Figure

5.6 shows a bean seed moving on the groove, which shows very close positions to Y axis.

Test of corn seed shows a different feature form what was observed in the tests of the

artificial seed and the corn seed. Figure 5.7 for test of corn seed shows seed positions on

the left side of Y axis, which could be interpreted as a retarded motion. The retarded

motion might be caused by the flat shape of the corn which could result in more contact

area and more friction force. The artificial seed and the bean seed are similar in round








74

shape as shown in figure 5.5, which means that there are more rolling motion than sliding

motion in the corn seed. However, in delivery motion into soil hole, both bean and corn

seeds show satisfactory results as shown in figure 5.8 and 5.9. As understood in equation

(4-5), the delivery motion into soil hole is not related with the shape of a seed.


























eL)



~II II




lED~


~ a
4L


T



A nI


a oo







i
'--^ f7P























































Figure 5.6 Bean seed motion on the seed path groove at the planting speed of
8.0 km/hr.























































Figure 5.6 Bean seed motion on the seed path groove at the planting speed of
8.0 km/hr (continued).























































Figure 5.6 Bean seed motion on the seed path groove at the planting speed of
8.0 km/hr (continued).
























































Figure 5.7 Corn seed motion on the seed path groove at the planting speed of
8.0 km/hr.






















































Figure 5.7 Corn seed motion on the seed path groove at the planting speed of
8.0 km/hr (continued).























































Figure 5.7 Corn seed motion on the seed path groove at the planting speed of
8.0 km/hr (continued).









[fRELEASE # 1
'RELEASE #1


S----------------RELEASE # 2
I1 RELEASE # 2


Figure 5.8 Bean seed delivery motion inside the spade after being released from the end
of the stationary ring at the planting speed of 8.0 km/hr.







83

RELEASE # 3



















RELEASE # 4















Figure 5.8 Bean seed delivery motion inside the spade after being released from the end
of the stationary ring at the planting speed of 8.0 km/hr (continued).








84

I RELEASE # 1






















r --- -------
I RELEASE # 2



















Figure 5.9 Corn seed delivery motion inside the spade after being released from the end
of the stationary ring at the planting speed of 8.0 km/hr.








85

!RELEASE # 3
I





















i RELEASE # 4


















Figure 5.9 Corn seed delivery motion inside the spade after being released from the end
of the stationary ring at the planting speed of 8.0 km/hr (continued).














CHAPTER 6
CONCLUSIONS


A seed transport and delivery mechanism was designed with the concept of free fall

in gravity and evaluated to show the feasibility of the design concept with the model test.

The most important feature of the design concept was whether it worked at high planting

speed of 8.0 km/hr (5 mph). Seed damage was not evaluated but it appears that this

design should handle seed gently. The design concept was theoretically evaluated on a

few feasible theoretical cases and a typical case was chosen and evaluated. This design

and model was compared to the current design of the revolving spade planter which has

been equipped with a relatively complicated seed transport and delivery mechanism.

As predicted theoretically, the mechanism was compatible with the original revolving

spade planter design and can operate at higher speed. Thus the mechanism could work

under any variation of traveling speeds. Based on the results and discussions, the

following conclusions were drawn:

1) The seed transport and delivery mechanism can be adopted to the current revolving

spade planter to achieve a high speed precision planting machine.

2) The seed path in the mechanism could be designed to the maximum speed limit which

might be desired in a planting operation.

3) The maximum mean difference from the theoretical position in seed motion in terms of








87

the displacement was 3.5 mm, which is equivalent to time difference of 0.004 sec. This

difference can be acceptable, considering the overall accuracy of machining the groove

and operating speed because the actual planting will always be operated a little lower that

the design speed, the highest speed.

4) Small seeds in physical dimension might be used in the form of pellet to be planted

with this mechanism.














CHAPTER 7
RECOMMENDATIONS FOR FUTURE STUDIES


This research project to develop a seed transport and delivery mechanism for a

revolving spade planter might be continued to bring the machine to an operational field

version. To accomplish this, the following might be recommended for future studies on

the revolving spade planter with the seed transport and delivery mechanism:

1) A variable traveling speed control system might be valuable to study the functionality

of the mechanism to study the simulation of the virtual situation of the field operation.

2) To perform all of the development process in laboratory, a soil bin for planting might

be prepared to evaluated the field adaptability of the whole system of the revolving spade

planter.

3) Physical properties such as friction coefficient of seeds might be evaluated with the

materials which would be used for the seed groove.

4) For the case of planting a pellet seed, the study of the pellet material must be followed

with selection of the design material for the seed path groove.

5) The formation of the soil hole must be analyzed in terms of compaction, related with

the shape of the spade.

6) The shape of the spade must be optimized in terms of the resistance in traveling

motion and the seed delivery motion inside the spade.








89

7) Finally, the soil covering tool might be studied to provide the best condition for

germination and emergence of seeds. The firming pressure might be varied according to

the soil condition which might be measured mechanically or electrically.








APPENDIX A
COORDINATE TRANSFORMATION






S unit base vector:
/ I, J : for XY coordinate system
"- / i, j : for xy coordinate system
o/ ~I x X

/ I X



i .... 5


Y (XMY)
y,
,y )(


Figure A.1 Rotation about coordinate axis

The coordinate system xyz results from the rotation ofZ axis about the coordinate

system XYZ with the directional angle 0 as shown in figure A. 1. The position vector r in

figure A. 1 can be represented using unit base vectors of both coordinate systems as

r = XI + YJ = xi + yj (A-l)

Using the relationships of the unit base vectors as

I = cos0i sinOj (A-2)
J = sin0i + cos0j ,

the position vector is expressed as

r = XI + YJ = (Xcos0 + Ysin0)i + (-Xsin0 + Ycos0)j (A-3)

Comparing the relationships (A-l) and (A-3), coordinate transformation between XYZ








91

and xyz is obtained as

x cos sin 0 X
y -sin cos 0
z 0 0 1 Z
or (A-4)
X cos0 -sin9 0 x
Y = sin cos 0 jy
Z 0 0 1 z








APPENDIX B
SOLUTION FOR THE DESIGN CASE II


The design problem is formulated as the following optimization problem:

x2 V1+Y2
minimize J= R )dX (B-1)


where the prime denotes differentiation with respect to X. Since the necessary condition

for the existence for a minimum value of the functional (B-1) is the vanishing of the first

variation(Weinstock, 1974), i.e. 6J = 0, the variation process for Y gives the Euler-

Lagrange equation as

9F d( dF
Y- d (B-2)
dY dX \Y)

where the function F(X;Y,Y') is the integrand in the function (B-2) as


F = (B-3)
V2g(Y- Rh)

The Euler-Lagrange equation (B-2) becomes

2(Y- Rh)Y" + ,2 + 1 = 0 (B-4)

Multiplying Y' on the both side of equation (B-4), equation (B-4) becomes equivalent to

the following:

[(Y- Rh Y')]0 (B-5)

Integration of equation (B-5) with using integration constant 2c results into the following:










S 2c- (Y- Rh)
Y- R,
F Y Rh(B-6)
dX Y- R,
dY 2c- (Y- Rh)

From equation (B-6), the coordinate X of the path is obtained using X(t=0) = 0 as


X = 2c -(Y-Rh dY (B-7)


To evaluate the integration (B-7), a new parameter P (Weinstock, 1974) is applied to

change Y as

Y= Rh+ 2csin (B-8)

where c3 is a constant to be determined using the known coordinate of both end points.

Substitution of equation (B-8) into the integration (B-8) gives a solution as

X = c(f sin/l) (B-9)

Thus, the path observed on XY coordinate frame is expressed with the relationships

(B-8) and (B-9). Therefore, the seed path groove is obtained by the coordinate

transformation as

x(t) = c(f sinfl)cos0 + [Rh + c3(1- cosf)] sin0
(B-10)
y(t) = -c(l sin/)sin0 + [Rh + c3(1- cos/)] cos0

where 0 = cot









APPENDIX C
SOLUTION FOR THE COORDINATE (x2, Y2)



e,: tangential unit vector
S e,: normal unit vector
,-" w, : distance between (x,, y,) and (x2, y2)
e.

I ', e, ~
Ss /
i\ I


S(/ Y2)

// ", (x,yz y, e, ,
S(X2, Y/ dy
;.- a2


i' dy
dx When tana, < 0
I e,
SWhen tana, 0



+y


Figure C. 1 Coordinate relationship between (x, y) and (x2, Y2)

The position coordinate (x2, Y2) of the surface on the other side is apart from the seed

path coordinate (x, y) with a distance w, which is a width of the seed path groove. When

tan a2 is greater or equal to zero, the following relationship is obtained;

dx
tan a2 (C-l)
dy
The coordinate (x2, Y2) is obtained as


(C-2)
y2 = w sina2










And also using the following relationships as

1
COSO2 /1 + tan2 a2
n a2 (C-3)
sin a2
V1+ tan2 2

Substitution the relationship (C-3) into (C-2) gives the coordinate (x2, Y2) as

1
X2 = x+ W, T a
)' W +tan2a2

Y2 =y-ws l 2
1+tan2 2

where tan a2 20.

When tan a2 is less than zero, the following relationship is obtained as

dx
tan= -
dy (C-5)
tan/f = tan(r -a2)

where tan 13 20.

From figure C.1, the coordinate (x2, Y2) is obtained as

x2 = x w, cos/
(C-6)
y2 = ws sin/

The relationship (C-6) can be given as