DESEGN AND DEVELOPMEN? OF A
STE? METEESNG QEVE'CE

Thesis for H19 Degree of M. 5.
MiCHIGAN STATE UNIVERSITY

Rey Ji’. .Eimenez
1961

1HtLS!S

0 9w

This is to certify that the
thesis entitled

Design and Development of a
Step Metering Device
presented by

Rey J. Jimenez-Mbntes

has been accepted towards fulfillment
of the requirements for

M.S. degree in Agricultural Engineering

 

 

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DESIGN AND DEVELOPMENT OF A

STEP METERING DEVICE

by

Rey J. Jimenez

AN ABSTRACT

Submitted to the College of Agriculture of

Michigan State University of Agriculture

and Applied Science in partial fulfillment
of the requirements for the Degree of

MASTER OF SCIENCE

Department of Agricultural Engineering

Year 1961

Approved by , 4

2-.

A if? S T RA C T

The design and development of a step metering device is de—
scribed. As the design was completed a plastic model. was constructed
in the Agricultural Engineering Laboratories of Michigan State Univer—

sity. This model was tested to some extent.

Because of the limitations of the plastic model a full scale metal
model was built. This metal model was tested with different size of
seeds, at different velocities and at various dropping distances, fixed
on top of a moving belt. Results were tabulated and the presicion of the
metering device determined by means of the coefficient of variation.

4

Seed size, velocity of travel and dropping height are related in the

tabulated results.

A statistical analysis, discussions of results and a critique of the
metering device are given. An appendix with a kinematic analysis of

the mechanism is also included.

DESIGN AND DEVELOPMENT OF A

STEP METERING DEVICE

b y

Rey J. Jimenez

A THESIS

Submitted to the College of Agriculture of

Michigan State University of Agriculture

and Applied Science in partial fulfillment
of the requirements for the Degree of

MASTER OF SCIENCE

Department of Agricultural Engineering

Year 1961

ACIxZNO\\'I-EDGMEN'I‘S
The author wishes to express his deepest and sincere gratitude
to all, Michigan Agricultural Experimental Station, Michigan State

University and their personnel, who helped in the development of this

work, Specially to those mention below.

Dr. Arthur W. Farrall, Head, Department of Agricultural Engi—
gineering , Michigan State University, for his enthusistic advice in
this work.

Dr. Wesley F. I’»uchele, the author's major professor, who pro-
vided not only valuable technical assistance but inspiration and encour—
agenient.

Dr. Frank Tse, the author's minor professor, Mechanical Engi—
neering Department ,which assisted in this work.

Dr. Roland T. I‘Iinkle, Mechanicanical Engineering Department,
who supervised the design of the mechanism.

Mr. Joseph Molitorisz and Mr. Ilarris Gitlin, Staff Members of
Agricultural Engineering Department of Michigan State University for
their valuable help and assistance.

Mr. James I3. Cawood, Mr. Glenim F. Shiffer and Mr. Harold
Brockbank for their cooperation in the shop and laboratory work.

Finally, my deepest love to my wife, Miriam, without her

this work could had never been completed.

TABLE OF CONTENTS

- INTRODUCTION ..........................................
LITERATURE REVIEW ....................................
History ................................

Lite rature Review ...................

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

IMPORTANCE OF WORK. . ...............................

OBJECTIVES .......................................
METHOD OF PROCEDURE .......... . ......................
CLASSIFICATION. . ..... . ............... . . . . .. .............
PLANTERS ANALYSIS ....... . .............................
EXPERIMENTAL STEP PLANTER. .........................
Principle and Theory .................................
Model Construction ..................................
Plastic Model. . ......................... ' .....

Full Scale Metal Model .....................

Description and analysis of mechanism of the
steel model ..............................

Operation of the Metal Model. . .................. ; . .
Power Train ..................................
Link Action ..............................
Separator and Spacer Action. . . . ............
Step Action.. ....................

Seed Cells, Shape and Size ...................

ll

11

12

12

15

22.

2.2

Z3

Z3

26

26

38

38

39

39

42

44

iii

Side Effects of Operation .......................
Shaking action ...........................
Unbalancing of the mechanism . . . . . . .........
Lateral velocity component of seed ..........
Press wheel slippage . ....................

Laboratory Test of the Step Planter ................ .. .

Equipment and Equipment Layout . ., .............

Procedure ....................................

Tabulated Results .............................
Observations

Discussion of Results .........................
Step Planter Critique .........................
APPENDIX .......................... . ..................
Kinematic Study of the Mechanism .. .................
Tabulated Experimental Data .......................

REFERENCES ..........................................

46

46

46

47

50

51

51

51

53

53

55

58

63

64

65

68

72

Figure

10

ll

12

‘ LIST OF FIGURES

Page
Exploded view of the John Deere Flexiplanter showing
seed plate . t . .. .................................... 16
Complete hopper assembly with seed wheel in place . . . 16
Inclined plate seed metering unit ............ g ...... 16
Experimental belt type planter developed for high speed
drilling ....................................... ... . o 16
Vector analysis of seed resultant and relative velocity
of seed to plate in the seed hopper . ................ 19
Shear action of cut-off on seeds ........ r ............ 19
Free fall in seed conveying tube ................ 21
Seed behaviour when colliding with the soil surface ,. . 21
Front and side view of the plastic model on the moving
belt ................... ..... 24
Back view of the plastic model t0p of the moving
belt................., ........... ....... .3 ..... Z4
Angled top view of the plastic model after depositing
seed on t0p of the moving belt ............... . ....... 25
Seeds planted with the plastic model ..... . .......... 25
Side view of step planter mounted on moving belt table. 27
Close-up of linkage mechanism and separator and
spacer. ........................................... 27
Outer rotating cylinder showing seed cells and end
gear ................. ................... 29

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

Cylindrical rubber brushes mounted on the steel shaft.

Shaft also shows end gear ............. o , . , .. ............ 29

Exposed view of separator and Spacer . . . . 3 ........ V. a . .

Separator and Spacer showing cylinders, gear sets and

rubber brushes in position ..... ............. . .........

Four bar linkage showing the path of the tracing point

(P) at intervals of 30° of the crank (M—l) . . , ...........
Separator and spacer at furrow surface level ....... I . . a .

Pointmovingalongtrajectory.....1,.Hw....;...,,...

Complete separator and spacer showing Spaced seeds

inpOSitionOIOJ OOOOOOOOOOOOO soc-ooooaooaoosnsoc-2.51.:

Back view of separator and Spacer Showing Shields and

SpacedseEdSQ'o-o.wvo~‘t,oOooooIouuoOI-‘a 0000000000 490;;.-0¢I

Comparison of cycloidal motion with the step periodic

motion . a . . ............ . ............................
Seed cell of the step planter ..........................
Seed trajectory when drOpped ....................... -, .

Resultant velocity (Vr) of seed when dropped .......... ..,

Separator and Spacer in two different steps when slipp-

age occurSOOOO ........... OJOEOOIDD OOOOOOOOOOOOOOOOOO

Moving belt power System and how it is transmitted to

the planter' S powered system .........................

Rear top view of the planter set-up on the moving belt
table I O I O I O I C O D C I I O O I J O O H I O 'J O 5 ............... 2 O . 0

Sample of recorded data using seed Size 6-7 at 1/4 "

dropping distance and at a belt velocity of 0. 50 mph. t . . .

Sample of recorded data using seed size 6-7 at 1/2 "

dropping distance and at a belt velocity of l. 00 mph ......

31

35

35

4O

4O

43

43

49

49

49

52

52

54

954

3O

31

33

34

Sample of recorded data using seed size 6—7 at 1"
drOpping distance and at a belt velocity of l. 50mph.

Average % coeficient of variation vs seed dropping
distance ........................................

Kinematic analysis of four bar linkage at dropping
point ............ t ...............................

Kinematic analysis of four bar linkage at 7. 5° past
dropping point ...................................

Kinematic analysis of four bar linkage at 15°past
dropping point ..................................

54

61

65

66

67

LIST OF TABLES

Table Page
1 Tabulated Results ................................ 56
2 Standard deviation of the average distances to the

theoretical distance .............................. 57
3 Seed weight per 100 seeds, and seeds weight per

acre used in planting at 24 inches between rows with

seeds 5 inches apart .............................. 62
4 Tabulated data at 0 inches dropping height for proc -

essed sugar beet seeds of Sizes 6:7, 7-8, 8—9 and

all together at O. 50 , 1.00 , and 1.50 mph .......... 68
5 Tabulated data at 1/4 " dropping height for proc—

essed sugar beet seeds of sizes 6—7 , 7—8 , 8-9 and

all together at O. 50 , 1.00 , and 1. 50 mph .......... 69
6 Tabulated data at 1/2" dropping height for proc-

essed sugar beet seeds of sizes 6—7 , 7—8 , 8-9 and

all together at 0. 50 . 1.00 , and 1. 50 mph ......... 7O
7 Tabulated data at lH drOpping height for processed

Sugar beet seeds of Sizes 6-7 , 7-8 . 8-9 . and
all together at 0.50 , 1.00 , and 1.50 mph ......... 71

INTRODUCTION

The production of most food and fiber crOpS begins with the plant-
ing of seeds in or on the ground. This is accomplished either by hand
or with a machine. Machines are rapidly replacing hands in the agricul-
tural fields . Although crOps are still planted by hand in many countries
throughout the world, the use of highly developed precision planters is
rapidly increasing.

Recent studies (Morton and Buchele, 1959, and Berrett and Reeve,
1959), concerning the percent stand of seeds have shown that when pre—
cise methods of metering seeds are used, higher profits results. Preci-
sion planting eliminates hand thinning labor and the profit losing skips
in the row.

The objectives of this research is to invent, design, and construct
a precision metering device. In order to obtain satisfactory results in
this thesis, a solution to a problem crop, with national importance ,
Should be found. This is why sugar beets seeds were chosen as the test
seed. It is a challenge to ingenuity, it is a challenge to all who wants to
help our farmers, just as it was a challenge to those who had tried in
vane and failed leaving their experiences behind for uS to use.

Barmington (19 56) wrote,

"Precision planting of sugar beet is a goal

that research men in this industry have had
for a long time. If the seed could be made

large, smooth, and dense, the problem of
precision planting would be greatly reduced
......... Since we are dealing with seed

that is not uniform in size, Shape, or den-
sity, it is difficult to imagine a niechani-

cal device flexible enough to plant non-uni-
form particles in a strictly uniform pattern. "

Before attempting a solution to this problem, existing commer—
cial and experimental planters were studied in detail. The Study showed
that all of the planters were dependent on the physical characteristic of
the seeds for good performance. If a prompt solution is desired it will
be easier to produce a good new planter capable of working with any
seed, than to breed a new type of seed. Good results had been obtain by
breeders in the production of a monogerm seed, and still, the problem
exists. Records Shows that nearly all of the past machinery research

effort was derected toward a modification of the existing planters and

very little was expended on new ideas or new approaches.

After studying the existing planters, it was decided to expend all
our efforts on a new idea, where special attention was paid to separa-
tion, spacing and placement of seeds on the ground with interest in the

Speed and simplicity of the process,

These factors were considered to be the most important of all.
Separation of the seeds without harming them and their proper spacing,
when placed on the ground, are two of the major economical factors.

~

Morton and Buchele (1959) stated that,

"The emergence of the stand of plants is
directly proportional to the uniform ope-
ration of the planting unit. "
If the emergence is proportional to the uniform operation of the
unit, the farmers income will be also proportional to it. Berrett and
Reeve (1959) showed that increasing the seed Spacing from two to three

inches resulted in a thinning cost reduction ranging from $3. 50 to $4. 75

per acre.

It is interesting to note that a small difference of one inch in the
seed Spacing can effect a cost reduction in spring labor. If thinning was
not necessary, due to precision planters, profits will still be higher

than that estimated by Berrett and Reeves.

With the above points in mind and a desire to increase the speed
of planting a step planter was invented, designed and constructed. The
new planter was tested and compared with existing commercial planters.
A kinematic approach for analysis was made of all types of planters,
according to the classification used, in order to point out some of the
actual problems that have not been solved and presumably were neg-

lected by others investigators.

LITERATURE REVIEW

History

The Indians used to say, "When the woman plant maize the stalks
will produce two or three ears, because women know how to produce
children. They only know how to plant corn to ensure its germinating.

Then let them plant it. They know more than we do. "*

Thru the ages, clearing the land by hand was men's work while
planting , sowing, tending and collecting were women's work. Even
today this still holds true in many parts of the world. Amore interes-
ting fact is that the same planting principles are used today with little
variation from those used 2, 000 years B. C. At that time the fore—
runners of the grain drills were used in China and MeSOpotamia. These
drills placed the seeds at a controlled depth and in accurate amounts.
Encyclopaedia Britannica (a) describes this machine as consisting of a
plow of that era equipped with a seed hopper and a tube to convey the
seed to the groove made by the plow point. The method of metering is
not known. Thirty six centuries later, in the 16th century, some changes
were incorporated to this planter. In the 16th and 17th century, systems
to ensure accuracy of rate were used. Almost all of them consisted of
a wheel equipped with Spoons. The spoons dipped into the hopper and

collected a quantity of seed. The seed was transferred to the seed tube

 

* Payne, History of the New World, ii 7, Encyclopaedia Britannica

which guided it to the furrows made by the plows points or Special ope-

ners.

This method of metering is still used today (1960) in many Euro-

pean drills.

This brief history shows that few changes were made on planters
and that the most important of these changes were made during the twen-

tieth C entury.

Literature Review

 

A review of literature published during the past 30 years will pro-
vide us with information concerning planting methods and systems, and

their development.

Mervine and MC Berney (1936) stated that the usual practice of
growing sugar beets was to drill the seed in a continuous row at a rate
of 18 to 201b of seed per acre. After the seedlings were up and well
established, they were thinned to single plants usually at about 10 or 12
inches intervals. In average stands, the thinning operation reduced the
number of seedlings in a hundred inches of row from one and two hun -
dred to about eight or ten. They also suggested hill planting because of
a saving in work and seed per acre. Hill planting will reduce the seed
from 18 -20 lbs to 7—8 lbs per acre. Referring to hill planters, Mervine

and Mc Berney (1936) reported that one-row models were designed and

built using a seed plate in a vertical plane. Seed cells in the circumfer-
ence of the plate accumulated seed as they passed through a seed hop —
per, carried the seed downward, and discharged it near the bottom of
the opened furrow. The peripheral speed of the seed plate was approx-
imately equal to the forward travel velocity of the planter, and rotated
in the same direction as the press wheel. Thus seeds in the cells were
practically stationary with respect to the ground and since they dropped

less than two inches, there was little seed scattering.

Three years later Mervine and Mc Berney (1939) reported, other
investigations with planters, and stated that none seemed to have a uni-
formity of seed drop which approached what was desired. Other types
of seed—metering mechanism were investigated to discover one which
would drop single seed balls and which, in-addition could be used with
any sized commercial seed. The pick-up cup or cell type of mecha-
nism seemed to Show the most promise. It utilized an endless chain of
small seed cups passing up through a seed hopper where one ball was
picked up in each cup. The cups emerged from the surface of the seed
and allowed all surplus balls to fall away. They then entered a tube
which confined the balls between the cups and passed over the driving
sprocket and down to the bottom of the opened furrow where the seed
balls, still equally Spaced, were dropped. The seed Spacing was varied
by changing the travel of seed chain relative to the forward travel of

the planter.

Mc Berney (1946) after the death of E. M. Mervine, pointed out
that the sugar beet seedling stand accepted as desirable in 1933-36 were
not well suited to present mechanization. The seedlings were not uni-
formly distributed in the rows and were too thick so that blocks left by
machine thinning contained several seedlings and would not produce a
satisfactory crop of marketable Size beets without further hand thinning.
Careful hand planting convinced them that much of the solution of mecha-
nical thinning laid on improved planting. Success in the development of
an improved Singlerseed planting equipment made it evident that seeding
rates could be reduced without causing large gaps and thus produce seed-
ling stands which could be thinned by hand much faster, or machine-
thinned without leaving so many multiple beet blocks. Seedling rates of
20 lbs per acre in 1936 were reduced to 3 lb per acre.

By this period Brooks and Baker (1946) had developed a statistical
method of evaluating and comparing planters by the use of a dispersion
coefficient.

Roy Bainer (1947) published results of five different planters com-
pared to hand planting. This showed that the dispersion coefficient of
the planters ranged from O. 95 to 2. 87 compared to 0. 79 by hand. These
results are from field trials. Using the grease board test (see appendix),
Bainer (1947), at a board Speed of 2 l/2 mph, obtained dispersion coe-

fficient of 0. 009 to O. 48 on the same planters.

Guelle (1947) reported that beet planters Operating at current trac-

tor Speeds distributed seeds at rates averaging about 35 seeds per sec-
ond. Because seed particles distributed at this tremendous rate varied
widely as to shape and as much as 20 percent in size, it was necessary
to drill and counter.-sink the cells in the seed plates and machine finish

these plates and other parts to close tolerances.

Partridge (1947) in discussing some of the problems with planters
wrote that no matter how mechanically perfect the metering device of a
drill was, a satisfactory distribution of the seed is impossible without

seeds of fairly uniform size.

Bjerkan (1947) pointed out that an increase in plate "Speed was
always accompanied with a decrease in percent of filled cells and cons-

equently the planting rate.‘ If seeds were large in relation to the seed
cells, greater variation in the planting rates resulted from changes in

speed.

One of the most Significant studies conducted in the 1940 decade
was that of Barmington (1948). Here he related the seed, cell size, and
Speed to the performance of the planter. In his studies, Barmington
Showed that the percent cell fill was dependent upon seed plate. The
higher the cell speed the lower the percent fill. of the cells. During this
decade, interest developed not only in the perfection at the planters,
but also in the obtaining of seed with better physical and physiological

characteristics. Great interest and effort was shown not only by the gov-

-9-
ernment but also by the private enterprise.

Futral and Allen (1951) reported that there were three main rea—
son for the drop in planting efficiency at higher. Speed:

1. Angular velocity of plates was so fast that the seed
was frequently carried past the drop -out Opening.

2. The inertia of the spring loaded kick-out mechanism
was too high to function prOperly and damage result-
ed to the seed when Spring tension was increased.

3. With tractor-mounted hoppers, seed frequently set
up a spiralling motion in the round flexible seed
spouts thereby delaying the drop and causing bunch-

ing.

Barmington (1956) compared the performance of various foreign
and domestic planters. He developed a numerical system for compari-
ring the planters. A perfect planter would have a score of 100 and all
planters were penalized for planting seeds too close together, or too
far apart. The planters that place half of the seeds in the theoretical
position would have a zero rating, and would not be considered a precise
machine. Negatives values would be obtained when less than half of the
seeds were placed in the desired position. The results obtained varied
from -42 to l 54. 89. This showed that the more precise mechanism was

not exactly what Should be called a precise planter. In his test he found

-10-
that 13% of the seeds were damaged.

Two years later Barmington (1958) wrote that there was a need

for a new planter for the new monogerm seeds, which would not damage
the seed but would convey the seed to the bottom of the furrow in a uni-
form pattern. Describing the metering process he said that the distribu-
tion usually begins with some kind of seed cell in either metal plates or
rubber belts. It would seem that at that point seed Spacing should be
accurate except for empty cells or multiple seeds in a Single cell. After
the seed left the seed cells, everything seemed to go wrong from a dis-

tribution standpoint.

Michigan State University had been conducting research in the
last three years in an effort to improve the performance of actual plant-

ers and their metering device (Morton, Stout and Buchele 1958-59).

This literature review Shows that better methods of metering
seeds is needed. The thinning problem could in all probability be solved
by accurate planting which would in turn decrease the seeding rate and
save seed. Thinning of the plants to a stand, seed cost and Speed of plant-
ing are economics factors that have to be under control in order to ob-

tain highe r profits.

Based on these facts, a method of separating seeds at low Speeds

and depositing them was used as a way of solving those problems in -

-11-

stead of conveying the seeds or drOpping them as by present means.

IMPORTANCE OF WORK

Our National income is greatly dependent on agricultural prod-
ucts. The farmers income is related to the stand of their crops. Fail-

ure to emerge a crop stand is therefore costly to the Nation.

Poor planter performance forces farmers to over-plant and makes
hand or machine thinning necessary. Hand labor cost has steadily in -
creased through the years and is becoming scarcer every season.

Mechanization is thus a must in all crops, eSpecially in sugar beets.

Less pre—harvesting work is desired, and a good solution is the

accurate metering of the seeds when planting.

OBJ ECTIV ES

Three main objectives were chosen for this work:
1.. To invent, design, and construct'an accurate and
dependable seed metering device.
2. To study the performance of existing metering de-
vices and compare them to the experimental seed
metering device develOped in this thesis.

3. If necessary and possible improve the performance

of existing metering devices.

-12-
METHOD OF PROCEDURE

The method of procedure was:

1. Conduct a bibliographic study of planter development.

2. Classify and conduct a functional analysis of existing
planters.

3. Invent, design and construct an experimental planter.

4. Conduct planter test and compare results with others

already tested.

CLASSIFICATION

Planters have been classified according to the metering system
and to the type of furrow opener (Bainer, Kepner, Barger—l955). A dif-
ferent classification system was used to divide the planters according to
the metering principle.

Two main groups were adopted: seed separation principle, contin-
uous or intermittent ; and seed conveying or depositing principle, contin-
uous or intermittent. Sub- divismns such as mechanical, vertical, hori-
zontal, step, and others were used to provide a means of general de-
scription. Examples using this classification system are:

1. John Deere Flexiplanter - Continuous seed separation
and conveying horizontal plate planter.

2. Milton Planter - Continuous seed separation and convey-

ing vertical plate planter.

-13..

This system not only describes the type of mechanism but also
their working principle. A better idea will be given to the reader by
describing some important or characteristic feature of the mechanism,
such as, belt or chain driven, positive or pneumatic ejecting, fixed or

variable seed Spacing, etc.

An example is the description of the experimental metering device
designed for this work:
Precision Step Plater- Ground driven, continuous seed sep-

aration, step seed depositing with horizontal rotating cylinder planter .

The above planter description Shows that this classification group—

ed nearly all planters in a main body.

Commercial planters could be classified in a general group of
ground driven continuous seed separation and conveying plate planters.
The operational description of any of these planters could be applied
to the rest when compared in working principles. The step planter was -'
different from those in the group by not being a continuous conveying
planter. Instead, this planter will deposit in steps the seed separated
and metered by the mechanism.

A classification list was made of a number of commercial and
experimental planters and is as follows:

A— Ground driven, continuous separation and conveying

plate planters.

-14-

1. Horizontal Plate with positive cut -off and
kick out.

a) John Deer Flexiplanters
b) International Harvester 185

2. Vertical Plate
a) Milton Planter ( with positive cut.- off

and kick out).

b) Taxigraine Planter
c) Ventura Planter

3. Inclined Plate
a) Case Planter

B. Ground driven, continuous separation and convey-
ing belt p1anters..

1. Horizontal Belt with rotating cut-off
a) Stanhey Planter

2. Inclined Belt
a) Semora Planter
b) Experimental Planter (Futral and

Allen)
C. Ground driven, continuous separation, step depos-
iting planter.
1. Horizontal rotating cylinder

a) Experimental Step Planter

-15-

PLANTER ANALYSIS

A functional analysis of the metering units will illustrate some of
the principal factors affecting their performance.
Three following basic principles were established:

1. To prevent damage to the seed and secure better
separation, low separating Speeds must be used,
even at high tractor Speeds.

2. Fixed cut offs cannot be used for removing the
excess seeds from the seed cells.

3. The seeds must be ejected as close as possible
to the ground surface and with a zero relative

velocity with respect to the ground.

These basic principles mUSt be carefully studied and a solution
to each must be found if good performance is expected from any planter
unit- According to our calssification, continuous separation and convey -
ing with horizontal or vertical plates are the most common of all sys-

tems.

Two commercial planters, John Deere Flexi-Planter 70 and the
Milton Precision Planter will be analized. Another very interesting
system, but not so common, is the experimental belt type, high speed
planter (Futral and Allen, 1951) classified as continuous separation and

conveying inclined belt planter. A variation of this system is the inclined

1b

 

 

 

Fig. 1a - Exploded View of the
John Deer Flexiplanter show-
ing seed plate (John Deer Co. )

 

Fig. lb - Complete hopper as-
sembly with seed wheel in place
on the Milton planter (Harbison
Paine, Inc.)

 

 

Fig. 1c - Inclined plate seed
metering unit. (J. I. Case Co)

 

 

 

Fig. 1d - Experimental belt
type planter developed for high
Speed drilling (J. G. Futral and
R. L. Allen, Agr.‘ Eng. April
1951. )

 

 

-17-
plate planter ( Figs. la, 1b, 1c and 1d.)

All these planters, although they have differences in construction,
have the same operating principles. Mainly they Constst of a seed cell in
or on a plate or belt that moves into or by the seed hopper for a certain
period of time. Seeds fill the cells and pass through a restricted passage
where a cut—off eliminates the excess seeds from the cell, discharging the
seed or seeds by gravity or mechanically into a tube that conveys the

seed or seeds close to the bottom of the furrow.

These seeds separating systems are dependent on two factors,
peripheral velocity of the seed plate and the resultant velocity of the
seeds. A vector analysis of the seed movement is shown in Fig.2.

The resultant velocity (Vsr) is due to velocity caused by the acceleration

of gravity (VSV), friction of seed to plate (VS ) and by the impact of the

h

seed on the edge or walls 'of the cell (VS ). Vector analysis (Fig, 2a) Shows

P
that the percent fill of cell will be affected by the vertical velocity and

the impact velocity, but mainly by the plate velocity (Vp).

Barmington (1948) Showed that the percent fill is proportional to
the peripheral velocity of the plate. As the relative velocity (seed to
plate) reaches a minimum the percent fill will increase (Fig. 2b). As the
horizontal velocity (Vsh) of the seed increases the impact velocity will
decrease and the resultant velocity will be downward (Fig. 2c). In the

case the impact velocity is in a downward direction the resultant velocity

~18-
will be downward and the relative velocity will be downward thus increas-
ing the percent fill. In the event that the cell is moving in an inclined
plane, the component of the vertical velocity that will force the seed

'into the cell will decrease, therefore decreasing the percent fill.

Fixed cut-off devices are mainly used in commercial planters.

By "fixed" is meant rigid and strong, not flexible. This device is main—
1y responsible for all of the sheared seeds. Figures No.. 3 shows a Skem-
atic diagram of a cut-off. The vector analysis shows why the Shearing

takes place so frequently.

AS the velocity of the plate increases, the collision of seeds to
seeds increases and a torque is developed in seeds due to the distance
between the points where the forces are applied to the seed. This tor-
que will tend to roll the seed backward and thus offering more area to
the cut-off to shear it. If no shear occures, the jamming of two seeds or

more might occure in the seed cell and the possibilities are that dam -

age to the seed will be done.

The conveying of the seed from the cell to the bottom of furrow
is accomplished mostly by a free fall thru a tube (Fig.4). The word
"free" is used because there is no control on the seed after it leaves
the cell, either by gravitational or forced ejection. When the seed
leaves the cell the velocity of plate throws the seed against the walls

of the tube, bouncing it erratically. The place of landing will be deter-

-19-

 

 

 

 

 

(a) vsp V
(I sr
.1; sh
., - V st VS
g\\ . \\ p p
V
(b) Sh V v
VSV /\SR
V
VI) - plate velocity p

st vertical seed veloc1ty

V

sh horizontal seed veloc1ty st

seed-plate impact re sult-

V
SP .
ant veloc1ty

(C)

V
sr
VSh VSp
VP
Vsr seed resultant velocity
Vsr SR
VSR seed to plate relative

velocity

 

Fig. 2 - Vector analysis of seed resultant and relative velocity of seed
to plate in the seed hopper.

 

CUT- OFF

1
F
I. ’ ‘ V SS

(21) (b)

 

 

 

 

F - seed to seed impact force
ss

Fsh - horizontal force due to plate velocity

Fig. 3 — Shear action of cut-off on seeds

 

 

 

-20-

mined by the velocity and direction of the seed when leaving the tube.
The resultant velocity of the seed will be different at all times,
therefore the relative velocity of the seed to the ground could not be
determined, thus no accuracy can be expected ofIthis system. There
is only one condition that will produce the desired result, this is when
the relative grou nd-seed velocity is equal to zero. The inaccuracy of
the system is aggravated when a Spiral motion is introduced by ribbon
tubing. The smoothness and vibration of the tube will greatly affect

the uniform fall of the seeds.

Nothing has being said concerning the collision of the seed with
the soil. The soil is not uniform in nature, especially when it had been
mechanically sheared. The soil texture is formed by clods including
some larger in size than the seeds being planted. If the seed hits the
surface in such way that it is held between clods there will be no further
movement, but if the seed hits a large clod, the direction of the move-

ment of the seed can not be pre- determined. (Fig. 5).

These factors are all working against the planters precision.
Buchele, Stout and Morton (1959) studied different ways of controlling the
seed scattering by restricting the seed outlet in different ways. In a
plain tube perpendicular to the soil surface they got scattering distances
up to four and five inches. By reducing the seed free fall they obtained

a reduction in the coefficient of variation of 21%.

-21-

 

 

Ejector

%\\\N\\¥§§\\~vp

\
\

 

 

 

 

 

 

Vg - ground velocity

VS —relative velocity of seed to
ground

 

Fig. 4- Free fall in seed conveying tube

 

q 9
f \ ‘.
,- f‘ .
.l ' ‘\ \
:I , /
' I I ‘ l l N -
v _ v I, \ / V

\ \

Soil Surface

Fig. 5- Seed behaviour when colliding with the soil surface.

 

 

 

-22-
These tests Showed that as the ejection distance from the soil was
reduced the scattering of seed decreased. When the relative velocity

(seed to ground) was reduced, the coefficient of variation was decreased.
EXPERIMENTAL STEP PLANTER

Principle 3 and Theory

 

The design of the Step Planter is based in three basic observations
obtained by the analysis of the existing planters. It has already been
Shown that lower velocities are needed for better seed separation, fixed
cut-offs destroys seeds, and seeds should be deposited on the ground at

zero relative velocity with respect to ground.

Slow velocities in the separating system are only obtained in the
commercial planters by lowering the tractor velocities and or by increas-
ing the seed Spacing. But if higher tractor velocities are needed, the
only way that lower separating Speeds can be obtained is by increasing
the space between seeds and plant more than one seed at a time. Plant-
ing and Spacing ten seeds at a time will cut the separating velocities by
ten. A device which will separate more than one seed at a time was de -

Signed.

No fixed cut-off is permitted. The seed must be handled in the gen -
tlest possible way. The shape of the seeds used, sugar beets, is approx—

imately Spherical. Even though it is not a Sphere, when a tangential

-33-

force is exerted on its periphery it will act as a sphere and will roll.
The higher the Speed the smoother it will roll. To create this rolling
action a brush could be used, in the form Of a roller rotating at higher
peripheral speed than the cells and in opposite direction. The rolling

action will not damage the seed.

Barmington (1958) wrote, "E very thing went wrong as soon as the
seed leave the cell". This statement points out the possibility of keep-
ing the seed in the cell and moving the cell to the soil surface and depos-
iting the seed from the cell directly to the soil. It might seem that this
is a complicate problem, but using a four link mechanism the cell can
be moved at the desired instant and at the desired velocity with respect
to the ground. Using this method the seed can be maintained under con-
trol throughout the complete cycle, and whats more important, the seed
can be deposited instead of dropped in a free fall, thus preventing scat-

tering.

Model Construction

 

Plastic Model

To verify the principle and theory of the experimental step plant—
ter a plastic model (one third scale) was built. The complete model was
made of " pexiglass". This permitted observation of actual Operation

of all systems.

24

a

tags."

 

Fig. 6 - Front and side view of the plastic model on the moving belt.
Seeds were placed over a greased sheet metal strip.

 

We
9..

\ 2. .1 I'gly’m-r
\ . ‘-. " '~.
"I K14“

O»

Fig. 7 - Back view of the plastic model in tap of the moving belt.

Seeds were placed over a greased sheet metal strip.

 

 

 

 

Fig. 8 - Angled top view of the plastic model after depositing seed on
top of the moving belt.

 

Fig. 9 - Seeds planted with the plastic model. Scale provides a
comparison means to show its accuracy.

--26_

Even when the model proved the principles and theory it could not
stand prolonged testing under severe conditions. The spacing and seed
separation was excellent. Photographic records were made of the plastic

model and its seed distribution and Spacing (Fig. 6', 7, 8, 9).

Because of the limitations of the plastic model, further testing

required a full scale metal model.

Full Scale Metal Model

A complete set of drawings were required to build a full scale steel
and aluminum model. It was necessary to redesign some parts and change
gear ratios. The model was built in the Agricultural Engineering Research
Laboratory at Michigan State University. ( All the following discussion

refers to the full scale metal model).

Description and analysis of mechanisms of the Steel Model

 

Two main sections compose the metering device:
a) the body or frame (Fig. 10)
b) the seed separator and spacer (Fig.11)
To the frame are attached the metering wheel (A), two four bar linkage
mechanisms (M), and three sealed boxes (F, D, E), linked by a Shaft (C)
which contains the necessary gear sets to supply the proper velocity ra-
tios at every point of the planter.

The seed separator and Spacer is held by the two four bar linkage

Z7

 

Fig. 11 - Close-up of linkage mechanism and separator and spacer.

28

mechanism (M), and is powered by a flexible shaft (H) from the front
gear box (G). This separator consist of two concentric cylinders (the
inner being stationary) (K-2), and rubber brushes (L) of a cylindrical
shape mounted on a steel Shaft. The outside cylinder (K-l) or tube
has twelve lines of five holes each, in its periphery, that serve as seed
cells (N). Individual seed hOppers (O) are mounted on top of the outer
cylinder exposing the seeds to the cells before reaching the dr0pping
point. Two sets of gears supply the necessary angular velocity to both
brush and seed cylinder. The inside cylinder provides a rolling surface

to the seed cylinder.

The seed separation process is accomplished by the outer rotat-
ing cylinder (Fig. 12) . The cylinder rotates at a low angular velocity.
Seeds are in direct contact with this cylinder. The cells are Shaped in

the periphery of it in lines of five cells each at 30° intervals.

The cylinder has a velocity ratio of 6 to 1 with respect to the me-
tering wheel. For every revolution of the metering wheel the cylinder
will rotate 60°” , 1/6 of a revolution. This greatly reduces separating
velocity. The velocity reduction was accomplished by separating and
metering five seeds at the same time. The cells are spaced 5" apart
along the cylinder. This Spacing is the exact distance at which planting
is intended. Cell size and Shape will be discussed later.

The cut-Off or brushing action is accomplished by the use of five

Z9

 

Fig. 12 - Outer rotating cylinder showing seed cells and end gear.

 

Fig. 13 - Cylindrical rubber brushes mounted on the steel shaft.
Shaft also shows end gear.

_30-

cylindrical shaped rubber sections mounted on a steel Shaft (Fig. 13).
This brush is mounted with its axis parallel to the rotating cylinder and
practically in contact with it. Figure 14 shows the mounting position.
The velocity ratio of press wheel to brush is 1 to 2. That is, for every
revolution of the press wheel the brush will make two revolutions. The
peripheral velocity (Vb) of the 1" diameter brush islTninches per minu-
te.

Where, Vb: 'lTDn( inches per minute)

n : revolution per minute (rpm)

D :: diameter( inches)

The 2. 5"(outside diameter ) rotating cylinder peripheral velocity is
2. 51Tn. Substituting the velocity ratio of brush and seed cylinder with
respect to the press wheel for n, the velocity ratios of both surfaces
will be obtained. Therefore, the brush to cylinder peripheral velocity
ratio is 4. 8 to 1, that is, the brush is 4. 8 faster than the cylinder. This
provides the prOper brushing action of the seeds on tOp of the filled cells,

making them roll fast.

Both brush and cylinder are operated by a set of gears mounted on
the front end of the seed separator and Spacer (Fig. 15), The power to
this gear set is provided by a flexibsle shaft that transmits the power

from the front gear box of the frame.

The moving of the separator and spacer mechanism from and to

31

 

Fig. 14 - Exposed view of separator and spacer.

 

 

 

Fig. 15 - Separator and spacer showing cylinders, gear sets and
rubber brushes in position.

-33-

the ground level is accomplished by two identical four-bar linkage me-
chanism. (M). Both are driven simultaneously at the same velocity ratio
maintaining the separator and Spacer always parallel to the ground sur-
face. The two four bar linkage consist of a tracing link (M-Z), a follow-
er (M-3), a stationary arm (M-4), and a driving crank (M-l). Their di-
mensional ratios are 3. 5, 3. 5, and 3 respectively, compared to the
driving crank (unit), see Fig. 16. The stationary arm is the distance
between the two pivoting points of the crank and the follower links (line
of centers) and is part of the frame or body. The crank, the unit length
member, is actuated by tun power gear boxes with a velocity ratio Of 2
to 1 (crank to metering wheel). This is the only link that rotates 360?

A complete planting cycle is obtained by every revolution of the crank.
The follower oscillates 41? AS the name indicates, this link follows the
inputs of the driving crank. The tracing link, which connects the crank
and the follower, oscillates with a rocking action. This link contains

the tracing point to which a desired motion is given, and to which the

separator and spacer is attached (Fig. 11).

R. T. Hinkle (1958) stated that" the motion of a point or link in a
kinematic chain relative to some other point or link in the same chain is
a property of the chain and not of the mechanism". This statement shows
that the movement obtained by this link at the tracing point is a property
of the hole chain (above ratios) and not of any other four linkage mecha -

nism.

-33-

 

 

 

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-34-

Hrones and Nelson (1951) classified this four bar linkage as a
class A (crank and rocker link) and described it as follows:

"Determinate linkage motion results when the number

of independent input angular motions is two less

than the nui'nber of links. All links are assumed to be

rigid members and are pin-connected to one another.

Freedom of relative angular motion exist between

any two members at the pin joint. The minimum

number of links which will permit relative motion

between links is four. . In the majority of applications

one of the links (the line of the centers) is stationary

(stationary arm) while a second link ( the driving crank )

is driven from an outside motion source. The motion of

the remaining two links (the follower and the tracing

links) is a function of the geometry of the linkage and

the motion of the driving crank and line of centers. "

A study of the path of the tracing point shows that the linkage (M-2)
when at point P (Fig. 16), reaches a velocity equal and opposite in di-
rection to the tractor velocity. At this point both desired conditions,
zero relative velocity with respect to ground and zero dropping distance ,
are achieved by the linkage system. The planting is accomplished by

depositing the seeds, five at the same time, separated and spaced at the

desired distance, at this instant.

The velocity of the tracing point at any time is compated by means
of a graphicaland analytical method. Considering the trajectory in Fig.
18, the point moving along the trajectory covers a distance ab measured
along the path in an interval required for the drive crank to move through
5°.. If the drive crank is rotating at a uniform angular velocity, the aver-

age velocity of the point during this travel is the lenght a-l; divided by

-35-

 

seed hOpper
test seed \ rubber brush mounted
\ on shaft

outside cylinder seed in seed cell

 

sinte red oil-
filled bronze

 

 

  

shield
inside cylinder

furrow surface

/\‘

empty c ell S

seeds on furrow—

Fig. 17 .- Separator and spacer at furrow surface level (dropping point)

 

 

Fig. 18- Point moving alongtrajectory.

 

 

-36-

by the time the drive crank is require to move 5°.

(67:16.)

vab z 5

 

Where, Vab : average velocity of the point moving from point

b( inches per second)

ab 2 length be tween a and b measured along the traject—

ory (inches)
(A) :angular velocity of drive crank (degrees per sec.)

The acceleration of point moving in the space is defined by,

v: use) = ——

t-vo

- av __ (AV)
«cg— (it _1lm TE 1ch

 

(AV _ \lbe‘Vab Ea) w-(OTBMJ “3 _ (g; " 0;) U32
at P- t. 5 5 _ 2.5

To compute the velocity of the tracing point at the depositing in-

stant (point P in Fig. 16) a direct measurement of the point path is tak-
en following the trajectory for an angle of rotation not less than 5°of
drive crank. Using the above velocity relation, and substituting for the

peripheral speed of the me tering wheel and the tracing point velocity,

the following relation is obtained;

_37-

 

 

Vt? _ (@)wcaawx _ (CED) 2

_ 5 _ S
Van": (Xlwwnsu _ (Xli

 

 

5 “ 2.5
if, \49: vmw

then, (L 2

Where, x : distance covered by the metering wheel during
the same time interval that the crank rotated 5°.
ab : distance measured along the trajectory of the
tracing .point traversed during the time interval
that the crank rotated 5°..
V - ' velocity of tracing point

V = peripheral velocity of metering wheel

This points out that when the distances measured are equal, the
velocities of the periphery of the metering wheel and the tracing point
in this period of time are equal and Opposite in direction. The metering
wheel circumference is 50 inches. The angle rotated in the time interval
was 2. 5", therefore the distance travel by the wheel was 0. 347 inches.
The distance measured along the path was 0.. 35 inches. If there is no
slip Of the metering wheel on the rolling surface, the velocity Of the sur-
face will be equal and in the same direction as the velocity of the trac-

ing point path during that time interval. Therefore the relative velocity

-38-

of seed to ground is zero. A complete study of the tracing point path
Showed that the velocity was maintained almost constant for a drive
crank angle of about 18° in the region on both sides of the ejection point .
This eliminates the necessity of absolute timing of the dropping point.
Even when the seed are not deposited at the same instant they will be
metered accurately because the linkage System will keep the separator
and Spacer stationary over the surface during a relatively long time in-
terval. In other words the acceleration is reduced practically to zero

at this time interval. A kinematic analysis of velocity and acceleration

is included in the appendix.

Operation of the Metal Model

 

When studying a complete mechanism the interaction between the
parts must be considered. The two principal mechanisms Of the step
planter are:

l. the seed separator and spacer
_2. two sets of four—linkage
With these mechanisms working together in the proper sequence, the

desired effects and results are produced.
Power Train

The operation of the step planter begins with the press and meter-

ing wheel (A) (Fig.1l). This wheel has a circumference Of 50 inches. Wheel (A)

-39_

transmits power through gear box (B) to gear boxes (D) and (E) through
shaft (C). The velocity ratio of the bevel gears in box (B) is 2.:1 (CzA).
In box (D) and gear set (F) of box (E), miter gears provide a 1:1 ratio at
90° to shaft (C). These gears power the link mechanism. The spur gear
set (G) in box (E), powers a flexible cable (H) leading to the separator
and spacer mechanism in a 1:3 ratio (H:C) . This flexible shaft (H) pow-
ers two spur gear sets in the forward part of the separator and spacer

mechanism. Gear set(l) (Fig.15) Operates the seed cylinder (K-l) at a ve~
.

locity ratio of 1:4 (I-lzK-l); gear set (J) operates the brush cut-Off (L) (Fig.

14)at a velocity ratio of 3:1 (LzH).
Link Action

The separator and spacer is moved through the prescribed path
of the tracing point (P), following the rocking motion Of link (M-2)as
actuated by link (M-l). The link action is Synchronized with the sepa-
tor and Spacer action so that when the tracing point (P) reaches the drOp-
ping point the separator and Spacer drops the seeds Simultaneously

(Fig. 16).
Separator and Spacer Action

Fig. 17 Shows a cross section of the separator and Spacer at the
ejection point. At this point the seed separator and spacer is at ground

level. The relative velocity of the separator and-spacer to ground is

40

 

Fig. 19 - Complete separator and spacer showing spaced seeds in
position.

 

Fig. 20 - Back view of separator and spacer showing shields and
ma “Ode

-41-

iS zero. The seed cylinder (K—l) is rotating at angular velocity ratio Of

1:6 (KzA) with respect to the wheel (A), while the brush rotates at an
angular velocity ratio of 2:1 (LzA) with respect to the wheel (A). The pey-
ripheral velocity ratio of brush (L) to seed cylinder (K~l) is 1:4. 8. (L:K—l),
This means that for every half revolution of wheel (A) the seed cylinder ro —
tates 1/12 of a revolution (30°) and the brush makes two revolutions. There
are always four lines Of seeds cells (N) exposed to the seed in hOpperS (O),
from point 1 to 2 , (Fig. 17 ). The angle of exposure is 120° . The seeds
begin filling the cells as soon as the cells are exposed to them (as they
pass point 1). The cylinder angular velocity is constant. Therefore,

the separating velocity is low and constant with respect to the tractor

velocity.

The seed cylinder continues rotation and when the cells in a row
(perpendicular to the drawing plane) reaches the rubber brush (L) the
excess seed is rolled out ( swept) by the higher peripheral velocity of the
brush (point 2). The seeds in the cells are now separated from the
rest and Spaced at an exact spacing Of 5 inches between seeds. Beyond
the brush, the seed cylinder is shieled by a shield made of plastic shaped
and fitted to cover the path of all the seeds from point (2) to point (3).
The shield (S) keeps the seeds from leaving the cells before reaching the
ejection point (planting point). When the cell reaches the ejection point

(point 3), all cells are exposed at the same time. The seeds drop by the

gravitational force and by a centrifugal force due to the angular veloc-

-42-

ity of the cylinder (very. small). A vector anlysis of the velocities and
forces acting at this instant On the seeds will be presented later. The
exposure of the cells is caused by a discontinuity in the shield (Q) at ..
point (3) . This opening continues for 5° of the cylinder rotation. i In the
case a seed is not dropped instantly, the dropping could occur during
the next 15° of the crank (M-l) where still the relative velocity of seed
cylinder to ground is approximately zero. This 15° are equivalent to

1. 5° of cylinder rotation. All seeds dropped will have a free fall from'
zero to about 1/4 inch. They are all released from the cells metered
accurately to 5 inches. With a small distance of free fall (can be ad-
just) and with no mOvement with reSpe ct to ground the seed will remain

at rest in the place where they were released.
Step Action

The step action, from which the planter was named, is the effect
and result of two simultaneous motions. The study of the path traced by
a point on the circumference of a circle rolling at a constant velocity,
without slippage, is shown in Fig. 21 (a). This motion is called
cycloidal motion.. This point is in contact with the surface every 360°.
The distance between contact points (X1) is constant. Comparing the be -
havior of this point with a walking action of a man, it could be called a
step.

The four bar linkage mechanism used in the machine produces

43

 

 

 

  

 

/
/
/
/
5311 2.17
(a) Cycloidal motion traced by a point on a circle
.H____ 3TBP(X;.)————4
I
/ ------ *‘"‘ ““ I
l - ,-
V l /
I
’/

 

 

o 1y. w age 21:
(b) Periodic motion traced by the four bar linkage tracing point

Fig. 21 - Comparison Of cycloidal motion with the step periodic
motion.

 

 

main body

 

cleaning trough

 
    
 

small seed
large seed
(a) Cross section of seed cell , (b) Seed in seed cells

Fig. 22 - Seed cell of the step planter

 

 

_44-

a similar effect when combined with the linear velocity (V) of the tractor.
Fig. 21 (b) shows how it behaves when traced in a vertical plane by the
combined action of linkage and the forward tractor movement. The-dis-
tance (X2) between points (depositing points) is held constant, regardless
of any change in the tractor velocity. The distance (X2) is prOportional
to the metering wheel (A) circumference. The distance (X2) for the step
planter is 25 inches. The number of seeds separated and metered are
also proportional to the wheel revolutions. Five seeds. Spaced 5 inches

apart (25 inches ) is half of the circumference of the wheel (A).

Summarizing, for every half revolution of the wheel (A) (50.3 in.

of circumference) the tracing point describes a periodiccycle.
Seed Cells, Shape and Size

To determine the Shape and size of the seed cells, tests were con-
ducted by shaping cells in a plastic model in Six different cavity Shapes
with Six different diameters. The cells were made small and enlarged

Slowly until the most efficient Size and shape was found.

The seed cells are shown in Fig. 22 . The characteristics of the
cells are as follows:
1. Prevents the planting of double seeds.
2. Anticlogging

3. Excellent brush action

-45-

The cell is composed of two sections: Fig. 22 (b)
1. main body

2. cleaning trough

The main body is semiSpherical in shape and the diameter is pro-
portional to the seed diameter. The diameter of the main body was made
to accept commercial processed sugar beet seeds. The most common
sizes are from 6/64 to 10/64 of an inch in diameter. A cell of12/64
inches was used without fear of seeds (of the above range) clogging in
the cell. The depth of the main body of the cell is 7/64 Of an inch.

The cleaning trough is a projection of the main body. Its tapered
shape facilitates the removal of excess seeds from the one separated
in the main body of the cell. In Fig. 22 (a), a seed is shown in the cell
with other seed laying on top of the separated seed. Note that the seed
in the left main body of the cell completely fills the cell while the others
are on the seed tube or in the cleaning trough. When the cell passes un--
der the brush, the excess seeds were rolled (sweeped) out of the tapered
surface of the trough. By this means the seeds were not damage by any
Sha rp edges. In the left main body, the seed is smaller and do not fill
the cells completely. Even in this case, the seeds on top have enough
surface exposed to the brush to be sweeped out without disturbing the

seed in the main body.

_46-

Side Effects of Operation

Four major side effects were expected from the Operation of the

mechanism.

1. shaking action

2. unbalance Operation

3. lateral velocity component of seed
4. slippage of press wheel

Shaking action

The shaking action is due to the inertia of the seeds. The crank
and rocker action of the linkage system accelerates and decelerates the
seeds somewhat violently and proportional to the tractor velocity. To elim-
inate this side effects small hOpper were designed. The seed are re -

stricted in the hopper to 1/2 inch of free Space. The friction of seed to

seed eliminates the Shaking action almost completely.

Unbalancing of the mechanism

Any rotating member is subject to a centrifugal force, (F)

Where, m = mass
w = angular velocity

r = radius

When the member is symmetrical and homogeneous it is said to

47

be balanced. This means that all forces have an equal and Opposite force
acting at the center of rotation which will cancel their effects. In the
case where all forces are not cancelled, the condition is said to be un—

balanced.

The driving crank (M-l) is a rotating member, and besides its own
unbalanced weight, a load is applied at a distance of 4 inches from its
center of rotation. This load is due to the weight of the separtor and
spacer assembly and the seeds. The faster the angular velocity of the
crank, the greater the unbalanced forces acting in the member. It should
be noted that the seed weight is variable and an average weight has to be
assumed for any calculations and, when balancing is done.

The balancing of the step planter was done by Slowly increasing
a restricted pivoting vibration absorbers counter weight (R) until a rea-
sonable smooth Operation was obtained. Lead weights were used as vi-
bration absorbers. Besides a Spring (S) Opposing the movement of the
linkage system at the forward stroke of the separator and spacer was
used to obtain a better balancing at the unbalancing peak Of the cycle

(Fig.11 ).
Lateral velocity component of seed

When seeds are dropped from the cells at the dropping point, a

lateral (Sidewise) velocity component exists which tends to cause them

to be unstable. This velocity component is at right angle to the path of

48

the machine.

The seed cylinder (Fig.1? ) is rotating in a clockwise direction at
a constant angular velocity. The seeds are carried in semispherically
shaped cells (Fig.22 ). Any mass moving in a circular path has a linear
velocity component equal to the product of the angular velocity (m) and

the instantaneous radius of rotation (r).

V=uor

Therefore, even at low velocities of the seed cylinder, the seeds in the
c ells will have a linear velocity equal to the angular velocity of the cyl- *
inder multiplied by the instantaneous radius (distance from center of
rotation of the cylinder to the center of gravity of the seed). This veloc-
ity component is very small, and at low angular velocities can be negli-

gible.

A graphical representation of the velocity components acting on
the seed at this instant is given in Fig. 23. The seed, when ejected, is
subject to the linear velocity (Vc) and the acceleration due to gravity.
The velocity due to gravitational acceleration varies according to the
seed mass. At the instant when the seed is released, the velocity due to
gravity is zero, assuming negligible Centrifugal force acting on the seed.
Immediately, the gravitational force acts on the seed, accelerating its

mass. The velocity of a free falling object in a vacuum at any instant is

49

 

Vc” Linear velocity of the seed
due to the cylinder angular
velocity (to ).

Vg= Velocity due to the accelera-
tion of gravity

 

Fig. 23 - Seed trajectory when dropped

 

 

 

v

V Z 2
g V1311 vc + v8
1

 

(a) Vector summation (b) Annalitical summation

Fig. 24 - Resultant velocity (V1,) of seed when dropped

 

 

metered distance V Slippage

 

 

 

 

 

 

 

 

:" ““““ l

1 LL ------ -'

O a O 2 O 3 2 e a
PHI“ H\rdt8

Fig. 25 - Separator and spacer in two different steps when
slippage occurs

 

 

50

given by,

V=\/.,t3JL

Where, V: velocity at any instant
VO-ainitial velocity
g = acceleration Of gravity

t: time of travel from initial conditon

The fall of the seed can be approximated in this ideal condition

and the velocity due to gravity (V ) at any instant can be computed. The

8
resultant velocity of the seed at any instant in its trajectory is found by
adding vectorially or amilytically the two velocity components (VC) and

(V Fig. 24).

g><

Pres 3 wheel slippage

Although not wanted, Slippage occurs in any traction powered me-
chanism. In press—wheel— powered planters, slippage is one of the

causes of irregular Spacing and scattering of the seeds.

The step planter, because Of its step action and its pre—determin-
ed Spacing, behaves in a different manner. Scattering occurs only be -
tween steps. When slippage occurs the step is delayed according to the
duration of the slip. When the planting takes place, the rear end seed

(the one closest to the preceding step) is separated from the front seed

51

of the preceding step. The distance is equal to the regular spacing plus
the slippage distance. The rest of the seed will be exactly Spaced in re—
lation to the others in the same step. Figure 25 shows a sketch of the

separator and Spacer in two differents steps when slippage occurs.

Laboratory Test of the Step Planter

 

Object

The object of this test was to determine the coefficient Of variation
of the step planter at different velocities and heights of planting with

seed size variation.

Equipment and Equipment Layout

The equipment used consisted of a 16 feet movable rubber table
belt powered by a 3 HP, 440 volts, 3 phase, electric motor, with a con-
tinuous variable velocity transmission, through a velocity reduction gear
set (Fig.26 ). The belt width is 2 feet. The step planter was attached to
this table (as illustrated), therefore receiving the power directly from

the rubber belt through the press wheel (Fig.27).

Normally the press wheel is positioned right behind the seed sep-
arator and Spacer. Fig27 shows how the press wheel was moved to a
side so that the seeds were not disturbed after being deposited on top of the
moving belt. The rubber belt was dressed with a band of cheesecloth

and secured to it with masking tape on both Sides. The cheesecloth

52

  
  
 
  
 

Fig. 26 - Moving belt
power system and how
it is transmitted to
the planter's powered
system.

hr

  

Fig. 27 - Rear top
view of the planter
set-up on the moving
belt table. Notice
displacement of
wheel from the sep-
arator and spacer
line of action.

53

provided a rougher surface than the rubber belt to prevent further move—
ment of the seed due to vebration of the moving belt. Besides, the cheese- .

cloth texture resembles more the soil texture than that of the rubber

belt.
P rocedu re

The seed hoppers were half filled with test seed. The separator
and spacer was adjusted to the desired ejection height. The electric
motor was regulated to the desired velocity. The motor was Started and
run for about one minute and then stOpped. The last two steps (50 inches)

were studied and measurements were done on them.

To obtain the correct position of the seeds and compare to their
actual position, the planter was slowly moved to the next step. The cor-
rect position was determined from the last seed of this step. This is the
seed nearest to the preceding step. The seed's position were determined
with respect to each seed's correct position. The positions were record-

ed on graph paper. This procedure was repeated five times for each case.
Tabulated Results

Typical data recorded are Shown in Fig. 28, 29 and 30 . With this
system the actual position of the seed with respect to the theoretical p0.-

Sition is known and any analysis can be made.

54

l.— 5 '6 "—.Tu-sy‘l—or—s "-—+— 5" 5“ —>(e- s"—+— 52-14 4731-55132:
1 0 I

i ‘ I - e o e e - e - —
. I I I .
T l l I v.“
I l l l .‘ls"
: l I l .

l
k—(f—a-l :e—H—vl Desired seed position

I

\ Theoretical distance (X) between seeds

Actual distance between seeds

Fig. - 28 - Sample of recorded data using seed size 6-7 at
1/4” drOpping distance and at a belt velocity of

0. 50 mph.
, -4a’/8||
)4 5v3‘+4,4+__5%_1-+-4,8+4%+_ 5v.“ —+ s"—~IJ+—,—47,j
l l I I ! . l P! l l
i _ g _-.._.\.-._-- \l . .. .. _--_-.7--. -.'-l;' - . l
I . 1
V4“ II I
I/
Fig. - 29 — Sample of recorded data using seed size 6—7 at
1/2” dropping distance and at a belt velocity of
1.00. mph.

lu u ‘ t1 . ‘ ' . u l w l lfl‘ “
"143+qu 5%.. ”(Why/“l. 5%6—1‘4E‘Vt4r 4%.. l ' .S’fifi/FU“
l :1 l i ' I . l | ! I ' l ; l 4
e 1/ ~* ‘ #9.. l, 0}" . 05.; l/.;/ . _/__ __£7(

£1 ‘

ly4' : i
i

I w-

Fig. -30 — Sample of recorded data using seed size 6-7 at
l“ dropping distance and at a belt velocity Of
l. 50 mph.

55

Tabulated results are presented in Table 1. These are represent-
ative samples of the five measurements made in each case. Besides the
mean distance, standard deviation and coefficient of variation. it shows
the average coefficient of variation of each group. Table 2 shows the
standard deviation Of the average distances to the theoretical distance
of all representative samples and the maximum standard deviation ob-

tained in each group.

Table 3 gives the weights per hundred (100) seeds, grams per acre
and pounds of seed per acre necessary to plant sugar beets at 24 inches

between rows for the test seeds.

Obse rvations

The following observations were made during the test:

Favo rabl e

 

1. No double seeds were obtained.

2. No broken or damaged seed were noted.

Unfavorable

 

l. Unbalance of the machine became a problem at velocities
greater than 1 1/2 miles per hour.

2. Electrostatic charging of the plastic shield prevented
good ejection in some cases. Seeds were retained in the

orifice of the shield due to attraction of the plastic to

 

56

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BELT VEL. SEED DROPPING DISTANCE 0.. 1/4" 1/2" 1"
M,P,H, SEED SIZE* 6-7 7-8 8-9 A11 6—7 7~8 8—9 All 6-7 7-8 8-9 All 6-7 7-8 8-9 A11
MEAN DISTANCE (xi) 5.0 5.0 5.0 5.0 5.02 5.04 4.99 5.00 4.96 5.03 4.98 4.91 5.01 4.80 5.05 5.01
0. 50 STANDARD DEVIATION (Si) 0. 0 0. 0 0. 0 0. 0 0.0 0.182 0. 259 0.106 0. 548 0. 332 0.380 0. 298 0. 825 0. 817 0. 596 o. 596
% COEFFICIENT OF VARIATION 0.0 0.0 0. 0 0. 0 0.0 3. 61 5.19 2.12 11.04 6. 60 7. 63 6.07 16.47 17.0 11.8 11.9 .
MEAN DISTANCE (xi) 5. 00 5. 00 5. 00 5. 00 4. 98 5. 02 5. 00 5.00 4. 94 4. 99 5. 03 5. 02 5. 03 5.17 4. 93 4. 97
1.00 STANDARD DEVIATION (Si) 0.0 0.0 0.0 0.0 0.106 0.0 0.149 0.106 0.408 0.538 0.350 0.577 0.675 0.527 0.723 0.236
% COEFFICIENT OF VARIATION 0.0 0. 0 0. 0 0. 0 2.13 0. 0 2. 98 2.12 8. 25 10. 78 6.44 11.49 13.4 10.4 14.65 4. 75
MEAN DISTANCE (35,) 5. 00 5-00 5. 00 5. 00 5. 00 5. 00 4. 96 5. 00 4. 96 4.99 5. 03 4. 83 4. 88 5.13 5.10 4. 99
1.50 STANDARD DEVIATION (Si) 0. 0 0. 0 0. 0 0. 0 0.0 0.106 0.248 0.248 0.298 0. 278 0. 394 0. 365 0. 364 0. 737 0.453 0. 746
% COEFFICIENT OF VARIATION 0. 0 0. 0 0. 0 0 0 0.0 2. 12 5. 00 4. 96 6. 01 5. 57 7. 82 7. 56 7. 45 14.4 8. 90 14. 95
AVE. % COEFFICIENT OF VARIATION 0% 2. 52% 7. 93% 1 2, 1 5%

 

 

 

 

 

 

*Measured in 64th of an inch.

Table l - Tabulated Results

Mean distance, standard deviation and % coefficient of variation at

various velocities and drOpping heights with different sizes ofseeds.
( All measurements in inches).

 

 

57

 

 

 

 

 

 

 

 

 

x s: 2:32:23;
0" 5. 00 0. 0 0. 0 O. 0 0. 0
1/4” 5. 00 0. 021 0.042 0.063 0 259
1/2" 5. 00 0. 066 0.132 0.198 0.377
1" 5. 00 0.330 0.660 0.990 0.825
Table 2- Standard deviation of the average distances

to the theoretical distance.

 

58

the seed. Sometimes the drOpping of the seeds were
delayed for an instant due to the attraction of the shield
surface.

. Width of the plastic hOppe rs were near the average width
of three seeds. This prevented in some cases, where
misses were observed, the filling of the cells.

Smaller Size seeds missed less than the larger ones.
This proved that the preceding Observation was valid.
When seeds were mixed the planter worked satisfactorily.
Seeds were observed to be held inside the cell due to the
cuticule which stuck to the irregularity of the seed cell.
Misses of the planter were not counted against the plant-
er’s precision because of the uncontrolled factors af-
fecting them.

Vibration of the moving table belt provoked some dis-

persion of the seed when drOpped.

Discussion of Results

It is interesting that the percent coefficient of variation at zero

dropping distance was zero for all velocities and for all sizes of seeds .

This group of samples showed that when seeds are deposited at zero rel—

ative velocity with respect to ground there is no appreciable dispersion.

Seeds are planted exactly at the desired distance.

59

Comparing the results of the rest of the samples with the zero
distance group, a tendency is Observed. Computing the averagecoef-
ficient of variation of each group they Show a tendency to increase lin-
early as the height Of seed drOp increases. The average coefficient of
variation (0, 2.52%, 7. 93% and 12.15%) Show that the height at which

the seed is dropped will be the determining factor, even though the plant -

er is Still dropping seeds at zero relative velocity with respect to ground.

It is also significant that the coefficient of variation in each group
do not follow a pattern or tendency even when the seed size and the sep-

arator and spacer velocity are changed.

The standard deviation of the means (Xi) with respect to the theo-
retical distance (X), is used to determine the radius around the theore-
tical distance which describes the area where practically all seeds will
fall. The means are distributed normally around the theoretical points
as follows:

a) 68. 26% of the observations deviate 1 Si
b) 95. 46% of the observations deviate 2 Si

c) 99. 74% of the observetions deviate 3 Si

The theoretical distance represented the point where the seeds
were expected to fall. If we take this point as the center of a ,circle of
3 Si radius it will draw a circle inside which 99. 74% of the seeds should

fall. This is true even when dispersion in the direction of travel only

60

was measured.

In the group at, zero height the radius is zero and all seeds will
fall exactly on the theoretical distance. The groups at 1/4” , 1/2“, and

1" height had radii of 1/16”, 3/8" , and 1" respectively.

Tests were conducted to determine whether the seed hit the belt
surface at the theoretical point. For this test a strip of sheet metal with.
a layer of grease was used. This grease layer held the seed at the impact

point. An analysis of the test results proved that the seed were Spaced on
the grease strip at the theoretical points. This showed that the seeds

scattered after impact on the belt.

Double seeds and damaged seeds were not observed throughout
the test. Seeds were reused several times and still no apparent damage
was done to them. The seed cell design was very satisfactory. The

change in seed Size did not affect the performance of the cell nor the

other mechanisms of the planter.

From the above obsevations and Obtaining the average weight of
100 seeds, of the test seed, the quantity of seeds to be planted per acre was
found, (Table 3). Assuming a row width of 24 inches, for average I‘OW
Spacing and planting at 5 inches between seeds, 1. 37 to 1. 86 pounds
.Of seed per acre will be used, depending on the seed size. In normal

operation, assuming some handling losses, 1. 50 to 2. 00 pounds Of seed

docs-m6 mc-aQOsp poem m> con-mi: GO 263C300 as omeno>< - ~m .m-m

sonar-hon» wo EofioGooU at» smegma-x

.més 0‘ mi. 0 W.“ O

 

61

 

4. - O

(Saqaut) aoueistq ButddOJq peas

 

 

 

.3

62

 

 

Seed size :erliggts(eger:: gm/acre #/acre
6 - 7 0.713 625 1.37

' 7 - 8 0.801 702 1.54
8 - 9 O. 963 845 1.86

 

 

 

 

 

 

Table - 3 — Seed weight per 100 seeds, and seed weight
per ac re used in planting at 24 inches be -
tween rows with seeds 5 inches appart.

63

per acre are needed. This compared to U. S. D. A. recommendations for
the North Central States, (Farmer's Bulletin No. 2060) 4 to 6 pounds

per acre, there is a reduction in seed consumption of 2 1/2 to 4 pounds

per acre.

Step Plante r C ritique

Results showed that the planter proved to work satisfactorily under
the conditions it was designed for. The unfavorable observations listed

should be studied carefully and a solution to each one should be found.

The planter should be redesigned to prevent excessive vibration
due to unbalanced mechanisms. lts weight should be reduced to a min -

imum , especially the separator and spacer. This will enable the plant-

er tO be tested at higher speeds.

APPENDIX

65

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REFERENCES

Bainer, R. (19433. New developments in sugar beet production. Agri-
cultural Engineering. 24: 8- 255—58

Bainer, R. (1942). Seed segmenting devices. Journal of the Ameri-
can Society of Sugar Beet Technology Proceedings. 216-219 pp.

Bainer, R. (1947). Precision planting equipment. Agricultural Engi-
neering. 28: 49-54

Bainer, R; Kepner, R. A. and Barger, E. L. (1955). Principles _o_f_
farm machinery. John Wiley and Sons, Inc. New York. 221-256 pp.

 

Barmington, R. D. (1948). The relation of seed, cell size, and speed
to beet planter performance. Agricultural Engineering 29 : 530

Barmington, R. D. (1956‘. Metering devices and test results of some
foreign and domestic sugar beet technologists, Journal of the Ameri-
can Society of Sugar Beets Technologists. 9 : l - 44

Barmington, R. D. (1958}. Planting equipment for monogerm seed.
Journal of the American Society of Sugar Beet Technologists. 10 : 1

48-50

Berrett. M. R. and Reeve, H. B. (1959). The effect of seed spacing
upon labor cost, yield and sugar content. Journal of the American
Society of Sugar Beet Technologists, Proceedings. of the Tenth Regional
Meeting. Ontario , Canada. 69-72 pp

Bjerkan, A.J. (1947). Precision planting. Agricultural Engineering.
27 : 54

Britannica Encyclopaedia. Primitive Agriculture. Vol. 17, 1010B pp

Britannica Encyclopaedia. V01. 1, 430A pp

Brooks, F. A. and Baker, G. A. (1946). Methods of describing regu-
larity of seed seedling spacing. Journal of the American Society of
Sugar Beet Technologists Proceedings.

Futral, J. G. .and Allen, R. L. (1951). Development of a high speed
planter. Agricultural Engineering. 32 : 215

73

Garner. F. H. and Sanders, H. G. (1939?. Spacing of sugar beet, Jour-
nal of Agronomy of Minnesota. 1198—1201 pp

Guelle, C. E. (1947). Precision planting of beets and corn. Agricul—
tural Engineering. 27 : 56

Hentschel, H. E. (1945). A study of the principles affecting the per-
formance of mechanical sugar beet seed planter. Thesis for the de-
gree of M. S. Michigan State University. East Lansing, Michigan.

Higgins, F. H. (1945). Vacuum planter newest development for con-
trolled sugar beet seeding. Implement record. (Sept.) 25—64 pp

Hinkle, R. T. (1958). Kinematics of Machines. Prentice Hall, Inc.
New Jersey. 231 pp

 

 

.Hrons, J. A. and Nelson, G. L. (1951). Analysis of the four bar link-
age. The Technology Press of the Massachusetts Institute of Tech-
nology.

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