HEGH SPEED PRECISION CENTRIFUGAL SEED mum Fhesis far the Degree at Ph. D. MlCHiGAE‘é STAIE UNEVERSITY AMIR U1. KHAN ' 1967 LIBR 41(ng Michigan State Unit-“<5: Sity THESIS. This is to certify that the thesis entitled HIGH SPEED PRECISION CENTRIFUGAL SEED PLANTING presented by Amir U. Khan has been accepted towards fulfillment of the requirements for Ph.D. Agricultural degree in Engineering 7?. 7. 777..%% Major ‘professor/ MW 0-169 ABSTRACT HIGH SPEED PRECISION CENTRIFUGAL SEED PLANTING by Amir U. Khan Horizontal plate planters are widely used for mechanical seed planting. The capacity of such planters to accurately plant at high speeds is limited. The Farm Machinery Industry is keenly interested in new concepts to solve the high speed seed planting problem. This research was conducted to study the feasibility of a new centrifugal concept which was proposed by the author for high speed precision planting. The main principles utilized in the new concept were: 1. The time of seed-cell exposure could be con- trolled by rotating the seeds with the cells at a known differential Speed. 2. The force to move the seeds into the cells could be increased by using centrifugal force. 3. The delivery and placement of seeds could be achieved by high speed ejection of seeds to permit embedding in the furrow. An experimental laboratory machine was developed to meter corn seeds. Tests were conducted to establish seed metering accuracy and the amount of seed damage at metering speeds of 400 to 1100 seeds per minute. Amir U. Khan Results indicated that the centrifugal concept was not only practical up to speeds of llOO cells per minute, but offered potential for further increase in metering speeds. The metering accuracy of this machine increased with high speeds, a performance completely opposite to that of conventional planters. Seed damage in the machine was comparable to con— ventional planters for each metering speed. Impact of ejected seeds on steel plate at ejection velocities of up to 2,750 feet per minute did not exhibit any significant effect on germination. The study proved that a machine utilizing the centrifugal concept was feasible for high speed precision seed planting. 7/777 awn/WW éfiéflw HIGH SPEED PRECISION CENTRIFUGAL SEED PLANTING By }‘ x!‘ Amir U} Khan A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Agricultural Engineering 1967 ACKNOWLEDGMENTS The author wishes to express appreciation to all who contributed directly or indirectly to make this research possible. Particularly, he would like to mention those listed below. Dr. Carl W. Hall, Professor and Chairman, Agricultural Engineering Department, for his interest and administrative assistance for this project. Professor Howard F. McColly, Agricultural Engineering Department, for his encouragement and assistance in guiding the program in his capacity as Chairman of the Guidance Committee. Dr. Howard L. Womochel, Professor, Metallurgy, Mechanics, and Materials Science Department and Professor Ronald T. Hinkle, Mechanical Engineering Department for their guidance as members of the Guidance Committee. Mr. Roy T. Tribble, Manager Forward Study Department, Implement and Industrial Equipment, Ford Tractor and Imple— ment Division, for his personal interest and encouragement which was a source of inspiration. Ford Tractor and Implement Division of the Ford Motor Company for providing the financial support through a special research grant for the project and other assistance provided during the course of this study. ii Professor Ralph L. Vanderslice, Mechanical Engineering Department, for his assistance in high speed photography. Sincere thanks go to Mr. J. B. Cawood, Mr. Glenn Schiffer, Mr. Harold W. Brockbank and other service staff of the Agricultural Engineering Department for their help- ful assistance in building the experimental equipment. iii TABLE OF CONTENTS Page ACKNOWLEDGMENTS O O O O 0 O O O O O O O 0 ii LIST OF TABLES O O O O O O O O O O O O 0 v LIST OF FIGURES . . . . . . . . . . . . . Vi Chapter I. INTRODUCTION . . . . . . . . . . . 1 Basis of the Problem . . . . . . . . 3 General Objectives . . . . . . . . A II. REVIEW OF LITERATURE . . . . . . . . 5 Seed Metering . . . . . . . 6 Seed Delivery and Placement . . . . . 9 III. ANALYSIS OF PLANTING OPERATION . . . . . l2 Seed Metering . . . . . . . . 12 Seed Delivery and Placement . . . . .~ 18 Centrifugal Planting Concept . . . . . 20 IV. SPECIFIC RESEARCH OBJECTIVES . . . . . . 25 V. RESEARCH TECHNIQUES AND EQUIPMENT . . . . 27 Experimental Mechanism . . . . . . . 29 Construction Details . . . . . . . . 36 Operational Details . . . . . . . . A3 Seed Metering Performance . . . . . . 50 Seed Damage Tests . . . . . . . . . 51 VI. RESULTS AND DISCUSSIONS . . . . . . . 53 Metering Accuracy . . . . . . . . . 53 Seed Damage . . . . . . . . . . . 66 VII. APPLICATION OF RESEARCH . . . . . . . 77 VIII. SUMMARY . . . . . . . . . . . . . 80 IX. RECOMMENDATIONS FOR FURTHER STUDY . . . . 83 REFERENCES . . . . . . . . . . . . o . 84 iv 10. 11. LIST OF TABLES Page Plate, cell and seed dimensions . . . . . 39 Effect of relative speed of seed-chamber, cell— ring, and metering—ring on visible seed damage . . . . . . . . . . . 55 Effect of a % inch wide baffle on seed damage . . . . . . . . . . . 57 Seed metering accuracy and seed damage of conventional planter A . . . . . . 58 Seed metering accuracy and seed damage of conventional planter B . . . . . . 59 Seed metering accuracy and seed damage of conventional planter C . . . . . . 61 Effect of cut-off pawl tip weight on seed metering accuracy and visible seed damage . 62 Effect of cut—off pawl tip spring force on metering accuracy and seed damage . . . . 68 Effect of impact surface on seed damage (germination test) . . . . . . . . 72 Effect of impact surface on seed damage (germination test) . . . . . . . . 73 Effect of impact surface on seed damage (germination test) . . . . . . . . 76 Figure 10. ll. l2. 13. IA. l5. 16. LIST OF FIGURES Velocity diagram of seed at during cell fill O o 0 0 O O I O O 0 O 0 Force on an ideal seed in contact with seed plate . . . . . . . . . Centrifugal seed metering machine set up for seed metering test . . . . . . Centrifugal seed metering machine set up for seed damage test . . . . . . . . Schematic laboratory arrangement of the experimental seed metering unit. . . . Centrifugal seed metering machine showing the metering head . . . . . . . . Centrifugal seed metering machine showing drive arrangement . . . . . . . . Seed metering head at impending metering slot and cell alignment . . . . . . Seed metering head at complete metering slot and cell alignment . . . . . . Seed metering head during operation . . . Metering head assembly drawing end view Metering head assembly drawing side section view . . . . . . . . . . Feed control baffle assembly . . . . . Seed pressure relieving baffles . . . . A few of the cut-offs used in the study CUt-Off area 0 o o o o o o o o 0 vi Page 13 15 22 28 30 31 31 32 32 33 3A 35 38 38 Al A2 Figure 17. 18. 19. 20. 21. 22. 23. 24. Page Seed metering sequence . . . . . . . . H6 Comparative metering accuracy conventional vs. experimental machine . . . . . . . 56 Effect of cut-off weight on metering accuracy and visible seed damage . . . . 65 Effect of cut—off spring contact force on metering accuracy and visible seed damage . 67 Effect of impact on seed damage (germination tests) . . . . . . . . 70 Effect of impact on seed damage (germination tests) . . . . . . . . 71 Effect of impact on seed damage (germination tests) . . . . . . . . 75 Suggested seed metering unit for a field planter . . . . . . . . . . 78 vii I. INTRODUCTION During the past two decades, considerable progress has been made in agricultural machines. Increased farm size and labor costs have dictated larger agricultural equipment to operate at higher speeds. Improvement in high speed planters has followed this general trend but with limited success. In addition to higher planting travel speeds, precise seed metering and seed placement have been desired. The term "Precision Planting" has been widely used and means the accurate, even spaced in— row placement of seeds at uniform depths. In corn, however, some authorities (15) feel that the control of per acre plant population is more important than the precise place— ment of seeds. The need of precision planting arose in the interest of larger yields, high speed tractor operations and reduced labor requirements. To a corn grower, precision planting meant higher yields and faster planting opera- tions. To a vegetable and beet grower, precision planting meant lower seed costs and the elimination of labor for thinning operations. The accurate placement of seeds at high plant popula- tion and high planting speeds has been a difficult problem. Barmington (5) wrote: l .. z . w : 2. . . .. - Since we are dealing with a seed that is not uniform in size, shape or density, it is difficult to imagine a mechanical device flexible enough to plant non—uniform particles in a strictly uniform pattern. The common machines used for planting are the cell plate planters. The plates may be mounted horizontal, vertical or inclined at some angle. By far the most pOpu— lar is the horizontal plate planter. The basic elements of a horizontal plate planter were conceived and deve10ped during the nineteenth century (7). The first patent on corn planter was granted in 1799 to Eliakim Spooner in Vermont(6). Two row horse-drawn planter patents were issued in 1839. The principle of operation of the cell planters is basically the same. Seed cells in a plate or a belt move into or by the seed hOpper for a certain period of time. Seeds fill the cells by gravity and pass under a cut-off mechanism. This mechanism restricts all other seeds, except the one in the cell, from passing under. The seed is then discharged by gravity or mechanically into a seed tube placed under the cut—off for delivery to the furrow. Records indicate that research efforts in the past have been mostly directed towards the improvement and modi- fication of existing planters. Less attention has been paid toward develOpment of new methods and concepts. Sub— stantial work has been done in matching the geometry of the seed and the metering elements of a planter and in adapting it for different seeds. Attention in recent years w. has been focused on incorporating devices for ancillary planting operations such as fertilizer and herbicide applicators and deveIOping devices such as rotary valves for zero relative velocity seed placement. The basic seed metering mechanism, however, has remained unchanged. A few new concepts for planters have been tried in recent years but were not able to achieve an appreciable degree of success. Notable among these are, the belt planters (2A, 26), the vacuum planters (8, 10, l3, 18, 21, 27, 28), the tape planters (16, 19) and the vibratory planters (9). Basis of the Problem It has been evident for some years that the conven— tional horizontal plate planters have failed to meet the operational characteristics in terms of planting speeds, seed metering and placement performance. Higher plant population, made possible due to recent advances in fertilizer application and other culturel practices, has further aggravated the problem. Plant population in corn has increased three to four times during the last ten years (17). Research workers are already speaking of future corn pOpulation of 30 to A0,000 plants per acre. It is generally considered that 15 to 20% of seeds are lost due to poor germination. The planter must plant excess seeds to offset this loss. General Objectives In View of the past history of the horizontal plate planter and the numerous attempts which have been under— taken to improve its performance, it was felt that this study should only concentrate on radically new approaches to planting. The initial objective was to analyze the seed metering and seed placement operations of the hori— zontal plate planters and to locate the critical factors which control these operations. Unconventional solutions of the problems associated with these factors were the final objectives of the study. It was felt that conven— tional solutions could only result in marginal improvement and may not meet the desired Operational characteristics. In order to reduce the number of variables in the study, it was decided to use only one kind and variety of seed. Hybrid corn (Medium Flat Chester KV BSA) was selected as it is one of the most popular variety of corn which is mechanically planted in the major corn grow- ing regions of the United States. Medium flat seeds are considered to be among the difficult seeds for precise metering. II. REVIEW OF LITERATURE Literature relating Specifically to corn planting is scarce. In recent years very little work has been done by public research institutions on corn planters. Research in industry has been primarily aimed toward specific improvements of the various makes of planters. This research was of a limited interest and did not result in any important publications. There is, however, enough material relating to plant- ing problems of other crops, which in many ways parallel the corn planting problems. A survey of literature on seed metering indicated the various factors which influence the metering accuracy. Roth and Potterfield (25) list the following twelve factors: Relative size of seed and cell. Relative shape of seed and cell. Orientation of seed to cell. Relative Speed of seed to cell. Distance cell travels when exposed to seed. Time interval during which cell is exposed. Type of cut-off and knockout. Depth of seed above plate. General shape of seed. 10. Variations in seed size and shape. 11. Seed surface characteristics. 12. Density of seed. \OCIDNO‘WJWJZ’UONH Bainer (3) suggested the following additional factor: 13. Cell wall taper. Autry et a1. (2) and Johonson (20) added: 14. Peripheral plate speed. 15. Number of cells in the plate. Seed placement accuracy is dependent not only on the metering accuracy but also on the ejection of the seed from the cell, conveyance of the seed through the tube and the placement in the furrow. Some of the factors which influence the placement accuracy are: Metering accuracy. Knockout pawl operation and its location with respect to the seedtube opening. Cell wall taper. Seed tube section Size and shape. Length of seed tube. Furrow opener shape. Design of covering devices. Speed of planting. NH mfl O\U'l BU.) Seed Metering A detailed study of the literature associated with seed metering indicated that relative seed-cell velocity has a decisive influence on cell fill. It has been established by numerous studies that seed metering per— formance drops when relative seed—cell velocity is increased. Bainer (3) in his study with sugar beet seeds indi- cated that plate speed effects cell fill in both the vertical and the horizontal plate planters. According to his study, a Speed increase of 200% results in only a 141% increase in the seeding rate. Autry and Schroeder (2) stated that slow plate speed (below 30 fpm) results in highest accuracy and a higher .-2 1" mean cell fill. They also indicated that metering accuracy was affected less by change in number of cells per plate than by speed changes, consequently, rates should be varied whenever possible by plate changes rather than by plate Speed changes. Johonson and Teal (20) indicated that both the inclined and the horizontal plate planters exhibit a detrimental effect on cell fill efficiency when speed is increased. However, there was no significant difference between the inclined and horizontal plate performance. Futral and Allen (12) in their study on peanut planters found that plates in inclined plate planters were rotating so fast that seeds were frequently carried past the drop— out opening and thus affected the metering accuracy. Barmington (A) in his study with sugar beet planters indicated that the per cent of cell fill reduced with increased cell speed and most planters exhibited minimum seed damage at a speed which gave 100% or slightly less than 100% cell fill. Roth and Potterfield (25) stated that beyond a cer- tain speed, an increase in plate speed was accompanied by a decrease in cell fill. They found that for a given time of cell-seed exposure, better cell fill resulted with a short exposure distance and slow cell speed. Andrews (1) concluded that speed of planting and kernel size are the two main factors effecting the meter- ing accuracy of corn planters. .D C G 2.. m a .. . . . I 9 .l. r... a n. In 1960 Gill (14) studied planting rates of corn at different planting travel speeds. His results are given below: Per Cent Metering Accuracy Planter Setting at Planting Travel Speed Plants / Acre 3 mph. 5 mph. 7 mph. 12000 106 102 96 16000 103 98 76 20000 101 90 69 He also studied the per cent seed dropped at dif— ferent plate speeds and found the following results: Plate RPM % Seed Dropped 15.5 106 20.0 103 25.4 101 34.6 98 42.3 90 48.6 76 60.6 69 These results indicate that high plant population and high planting speeds, conditions generally encountered in current agricultural practices, have an inverse effect on metering accuracy. Many research studies have established that 33 revolutions per minute of standard 16 cell plate results in optimum cell fill. This is equivalent to 528 cells per minute or about 62 feet per minute of plate peripheral velocity. Brandt (6) however, places this limit at 45 rpm (720 cells per minute) or about 90 feet per minute of plate peripheral velocity. This discrepancy and a few other opposing claims in research publications raised doubts about the correct cell velocity for optimum cell fill. It was therefore decided to conduct laboratory tests on a few popular makes of horizontal plate planters with 16, 20 and 24 cell plates and to establish the effect of plate Speed and number of cells on metering accuracy. Seed Delivery and Placement Morton and Buchele (23) concluded that bouncing and walking action of the seed during fall was responsible for non—uniform seed placement. They found that when the seed hits the ground it scattered in an area of i4 inches due to bounce. Decreasing the length of the seed drop increased the accuracy of seed spacing. Larsen (22) also mentioned bounce in long seed tube as a factor influencing placement accuracy. Evers (11) in his studies with sugar beet planters indicated that increased planting travel speed has an adverse effect on seed placement. Speed effects seed placement both before and after delivery in the furrow. He stated: This number of seed displacement before delivery shows that with an advance of 0.75 m/s and a drop of 40 mm and in spite of a regular cell sequence, 37% of all seeds have already before delivery suffered a disturbance of their sequence and do not reach the ground at the theoretical interval. mud.— n- ... a .|. VT— x at; .In .... .. . .Im .qu .. J u 10 When the speed is doubled, this figure rises to 50%, so at this speed half the seeds are not hitting the ground at the correct interval. His study with rolling and shoe coulters exhibited a severe rolling and bouncing movement of the seed in the furrow after the delivery of the seed. A wedge coulter exhibited reduced seed roll and bounce. He found the following results on his studies associated with the roll— ing of seed in different type of furrows. Per Cent of Seeds Affected by Rolling at Forward Speed Coulter Type A 0.75m/S 1.00m/s 1.25m/s 1.50m/S Roller 60.9 62.5 67.1 67.3 Shoe 45.7 48.8 57.6 58.1 Wedge 13.5 20.1 21.1 23.2 Thus the speed of travel and the type of furrow openers effect the placement accuracy even after the delivery of the seed to the furrow. Autry and Schroeder (2) studied the dispersion of seed and found that it was a function of longitudinal cell dimension (or cell shape), plate Speed, location of knock— out pawl and ground speed of planter. They also found that the seed tube caused considerable seed scatter and demonstrated with experiments that a tube confirming to the parabolic path of a falling seed showed less dispersion. 11 They concluded that height of fall has little or no effect on seed dispersion unless there is interference in the seed tube. III. ANALYSIS OF PLANTING OPERATION The planting operation consists of two steps, seed metering and seed placement. Seed Metering Seed metering is the process of singling of seeds from a bulk supply. The filling of a seed in a cell and the ejection comprises the process of metering in a planter utilizing the cell concept. A velocity and force analysis of a seed as it starts to enter the cell is essential to understand the cell fill operation. Figure 1 shows a seed as it starts to move into the cell and the velocity vector diagram in a hori- zontal plate planter. The resultant seed velocity Vsr is due to the velocities caused by the acceleration of gravity (VS ), friction between V seed and seed plate (Vsh) and by the impact of the seed on the edge or walls of the cells Vsi’ Vsr = st ++ Vsh ++ VSi ————— (l) The relative seed—cell velocity (V ) is the vector sum S/c of the resultant seed velocity (Vsr) and the cell velocity (v0) 12 ,1. .1 . illll|lill|i.| .i i . .1 13 V . S1 * 1 / > Wfli mm m . \/ sv VC 0 \ VSI’ V V s/c sv Vsh VSi VSV = Vertical Seed Velocity Vsh = Horizontal Seed Velocity . = Seed Velocity imparted due to impact with Si edge of cell Vsr = Resultant Seed Velocity Vc = Cell Velocity (horizontal only) Vs/c = Relative Seed Cell Velocity V v = Vertical Component of V s/c s/c V h = Horizontal Component of Vs/ s/c c Figure l.-—Velocity diagram of seed during cell fill. Vs/c = Vsr ++ Vc _______ (2) The relative seed—cell velocity is composed of the vertical (VS/CV) and horizontal (VS/Ch) components. Vsc = Vs/ch +4 VS/cV ------ (3) Ideal cell fill would occur when the vertical com— ponent of the relative seed—cell velocity (VS/CV) is maximum in magnitude, since it is the velocity along the direction of possible seed movement, with respect to the cell. This condition can be achieved when the horizontal com- ponent of the relative seed—cell velocity (VS/Ch) is zero. In practice, however, a cell must be exposed to a fresh seed after each seed delivery to avoid cell starvation. It is therefore necessary to maintain some horizontal relative seed cell velocity (VS/Ch) for satisfactory seed metering. It seems obvious that to achieve high cell fill, it is essential to maximize the vertical component of the relative seed—cell velocity (V v). It is also necessary s/c to control the horizontal component of the seed—cell relative velocity (Vs/ch) close to a value which is suffi- cient to maintain constant fresh seed exposure but not too large to unduly reduce seed—cell exposure time. These two objectives have been the fundamental basis for the improve— ment of seed metering accuracy in this study. 15 Figure 2 shows a force diagram of an ideal round seed in contact with the horizontal seed plate in between the cells and exactly on top of a cell, in a vertical tangential plane. (a) Between cells (b) On top of cell W w 3 Vs avS (//\\ {/fl \) (/"‘\ /’_\\(/'\\ (/ \\ \ / \ /' \ j \ F / \. / l/ \ / \ (F f ) \\4// \ / h4/ \¥/ I N V0 V0 W = Weight forces due to the seed and the column of seeds on top Ffvz Resultant vertical friction retarding force Fh = Resultant horizontal force Ff = Frictional force between seed and seed plate and between seeds Figure 2.—-Forces on an ideal seed in contact with seed plate. 16 The resultant vertical force F, which helps to propel a seed into the cell, is the sum of the vertical forces on the seed. Very little is known about the resultant vertical retarding force Ffv except that it is affected by the coefficient of friction between seeds, coefficient of friction between seed and internal surfaces of the hopper and by the amount of seed in the hopper. Newton's law of motion states F=— ————————— (5) in which F is the accelerating force in pounds, W is the weight of the mass being accelerated in pounds, a is the acceleration of the mass in feet per second squared and g is the gravitational constant. Substituting equation 5 in 4 we get in which aV is the acceleration of the seed in the vertical direction and m is the mass of the seed. Even if it is assumed that FfV is very small, the resultant maximum vertical acceleration aV available to the seed in a conventional planter will always be less than the gravitational acceleration. 17 The seed must fall through a distance of approximately half its diameter before it can be securely lodged in a cell. The seed cell exposure time required for a seed to drOp this distance into a cell, is dependent on the resultant vertical acceleration (av) which in a conventional planter is always less than 32 ft/secg. Therefore in a gravity dependent cell type seed metering machine, there is always a minimum theoretical time of seed—cell exposure below which no cell fill can occur. Significant improvement in cell fill can be achieved. if the seed could be subjected to higher than gravitational acceleration along the direction of the seed movement into the cell. Compressed air, impact and centrifugal force are some of the possible means to achieve high acceleration. A careful study indicates that the use of centrifugal force would be most practical. Centrifugal force increases in proportion to the square of the angular velocity and can provide increasing force at the higher planting speeds. The mechanism used in this study utilized centrifugal force for cell fill. Very little is known about the horizontal relative seed—cell velocity (Vs/ch) which also plays a Significant part in the cell—fill operation. Experimental studies indicate that a 62 fpm cell velocity results in an optimum cell fill in horizontal plate planters. The horizontal seed velocity (Vsh) of seeds in contact with or in the immediate vicinity of the plate, is not well known. High l8 planting speeds result in high cell Speed (V0) and reduced seed—cell exposure time. This is one of the major causes for the poor seed metering performance associated with conventional planters at high planting travel speeds. It seems logical that the seed-cell exposure time could be successfully controlled by rotating both the seed in the hOpper and the cell plate in the same direction at a desired speed differential. While such a control is not possible with existing planter designs, it is conceivable that conventional planters could be redesigned to incor- porate this feature. The speed differential can maintain the relative seed—cell velocity at a level which would provide sufficient seed—cell exposure time for optimum cell fill at any seed metering speeds. Rotating the hopper is one possibility but it would consume considerable power. It may also create problems due to the presence of a stationary cut—off inside a rotating hopper full of seeds. The mechanism used in this study achieved a controlled relative seed-cell velocity by rotating only a small quantity of seeds with the cells without rotating the hopper. Seed Delivery and Placement The operation of cell emptying, in a conventional horizontal plate planter, has been photographed and studied in slow motion. It is observed that, when the knock out pawl is properly located in relation to the a—v."“_. I . .l v... Ir. . _ .. 19 seed delivery tube, the seeds fall by gravity and do not require assistance from the knock out pawl. Only seeds with an interferance fit in the cells are ejected with the help of an impact from the knock out pawl. If the force available for seed ejection is high, the knock out pawl can be eliminated. High ejection force can be developed by subjecting the seed in the cell to an acceleration greater than that of gravity. The experimental machine utilizes this means for seed ejection. Due to the varying contact surfaces between the knock out pawl and each seed, the direction of ejection is not uniform in a conventional planter. It is presumed that the seed ejected with the help of the knock out pawl strikes the inside walls of the seed delivery tube and descends the tube with a motion involving richochet and whirring. The seeds which fall on their own, by gravity, are also thrown against the seed tube walls because of the horizontal seed and cell velocity. The interference from the tube, results in a non—uniform transfer of seed to the ground and causes uneven in—row spacing. It is not possible to develop a seed tube which would conform to free fall trajectories of all the different kinds of seeds at different planting speeds. One approach to eliminate the tube interference problem is to eject seeds from the cell at high initial velocity to almost instantaneously transfer the seed to the ground along a straight path. 2O Disregarding air resistance, the time required for a seed to fall from a cell to the ground under free fall conditions can be calculated by the equation: S = 1/2 gt2 + vot _________ (7) S = distance of vertical seed fall t = time in seconds g = gravitational acceleration VO = initial vertical seed velocity In a horizontal plate planter, the initial vertical seed velocity is zero. If the seed is ejected with high initial velocity, the time required for seed delivery can be substantially reduced. The high velocity seed delivery would eliminate the need for a seed tube and the problems associated with it. It would also permit the embedding of a seed in the furrow and eliminate the seed bounce and roll problems encountered with conventional planters. Centrifugal Planting Concept From the analysis presented earlier in this chapter, it seems evident that a centrifugally dependent seed metering and placement mechanism would solve most of the problems encountered with conventional planters. Such a mechanism would utilize the following three principles: 1. Control of the seed—cell exposure time can be achieved by rotating both the seed and cell at a desired velocity differential. --m‘~— 21 2. Improved cell fill at high planting speeds can be achieved by subjecting the seeds to higher than gravitational acceleration along the direction of Seed movement into the cell. 3. Almost instantaneous seed delivery and placement in the furrow by high velocity ejection can improve seed placement accuracy. Based on the above three principles, the author was able to develop a laboratory seed metering machine (Figures 3 and 4). It takes in,an unmetered flow of seeds from a hopper, spins, meters and ejects the seeds in the desired direction with the help of centrifugal force. It consists of a circular seed chamber rotating in a vertical plane with a cell-ring and metering—ring around its periphery. Unmetered seeds enter the rotating chamber through an axial Opening and start to rotate with the chamber. Centrifugal force distributes the seeds in the chamber and aids the seeds to fill the cells in the cell- ring which forms the peripheral wall of the seed chamber. The cell-ring can be set to rotate at any desired velocity differential with the seed-chamber. The metering-ring has a single metering slot and rotates concentric to the cell- ring. The metering-ring and cell-ring drive ratio permits the alignment of the metering slot with a subsequent cell on each revolution of the metering—ring. The seed in the cell transfers to the metering slot during alignment. A stationary shield holds the seed in the metering Slot until Figure 3.—-Centrifugal seed metering maching set up for seed metering test. 23 the ejection point is reached. The seed is thus ejected in the desired direction at a velocity which is equal to the peripheral velocity of the metering Slot. The seeds rotating in the seed-chamber are subjected to a non—rectilinear acceleration (a) which is: in which V is the absolute speed of the accelerated mass in feet per second and r is the radius of rotation in feet. Substituting this value for the acceleration into Newton's Motion equation, equation 5, the equation for centrifugal force is obtained in which w is the angular velocity of. the seed—chamber and W is the weight of the seed. F = (-) rw ————————— (9) Since the seed-chamber rotates in a vertical plane the seeds are also subjected to a gravitational accelera— tion (g Sin 9) where e is the angle the cell makes with the positive horizontal axis. The force available for cell fill (Fr) is: F = (4m;2 - w Sin 6 ...... (10) r' s As the Speed of the machine increases, the gravita— tional contribution to the force Fr becomes less and less significant. The centrifugal contribution to the force Fr increases at a faster pace than the Speed of the machine. This offers the possibility of improved cell fill due to higher cell fill force at increased planting speeds. 24 Since the seed is ejected at the peripheral velocity of the metering slot, the kinetic energy (KB) of the ejected seed is: KE II l-' \ [U E? <: I | I I I I I I H |—' This is an expression for the kinetic energy which must be dissipated before the seed becomes static. When the seed strikes an object or the ground, the energy of rebound (T) becomes: in which Eg is the coefficient of restitution of the seed and the work (Q) by the seed becomes: Ideally, it would be desirable to have the ground or the impacted surface such that would make Eg zero and absorb all the seeds' kinetic energy. This would be ideal from the standpoint of seed damage. It is, however, possible that the seed may strike a stone or any other hard object which may damage the seed. It was, therefore, nec— essary to study seed damage by impacting the seeds on a steel surface at different ejection velocities. IV. SPECIFIC RESEARCH OBJECTIVES The Specific objectives of the research were: 1. To establish seed metering performance of con- ventional 16, 20, 26 cell edge drop horizontal plate planters as a yardstick to compare with experimental planter performance. 2. To design and develop a laboratory seed metering and placement mechanism utilizing the centrifugal concept and incorporating the three principles stated in Chapter III. 3. To conduct seed metering accuracy tests at meter— ing speeds of 400 to 1100 cells per minute. The 1100 c.p.m. metering speed provides a planting travel speed of 7 mph when planting in 40 inch rows for a population of 22,400 seeds per acre. 4. To conduct germination tests on seeds ejected from the experimental machine at velocities of up to 3500 feet per minute and collected in cloth chutes to avoid any impact. These tests were to provide information on the extent of seed damage within the machine. 5. To conduct germination tests on seeds ejected from the experimental machine at velocities of up to 3500 feet per minute and impacted on a steel surface placed at a distance of 18 inches from the point of seed ejection. 25 26 These tests were to provide information on the extent of maximum possible seed damage that could occur during seed placement in the furrow. 6. To evaluate comparative performance of the experimental machine with conventional planters. 7. To suggest guide lines for further research and for the adaptation of the centrifugal concept to a field machine. V. RESEARCH EQUIPMENT AND TECHNIQUES Only one kind of corn, medium flat (Chester KV 35A) was used in the entire study to reduce the number of variables. Performance tests on conventional planters were. conducted on test stands at the Engineering Laboratories of The Ford Tractor Division, Birmingham, Michigan, during the author's employment with the Company. The first part of the study at Michigan State University was concerned with the design and development of an experimental machine utilizing the centrifugal con- cept (Figures 3 and 4). Considerable time was spent on this phase because of the numerous problems encountered before satisfactory operation was achieved. Transparent plexiglass materials were widely used in making the metering unit of the experimental machine to permit photographing of seeds inside the mechanism during operation. Strobe lights and high Speed movies, photo— graphed at 5,000 frames per second, were used to study the machine operation. These techniques were useful in study— ing the cut—off performance, the distribution and movement of seed in the chamber, the transfer of seed from the cell to the metering slot and the ejection path of the seed. This information was instrumental in improving the per— formance of the machine. 27 28 Figure 4.——Centrifugal seed metering machine set up for seed damage test. 29 Tests with the experimental machine were primarily conducted tO establish the metering accuracy and seed damage at various seed metering speeds and impact conditions. Experimental Mechanism Figure 5 shows the schematic arrangement Of the experimental seed metering machine. The seed metering head with the drive arrangement is illustrated in Figures 6, 7, 8, and 9. There were three separate driven members in the seed metering head, seed chamber, cell—ring and metering- ring. The drive to the three members was taken from a stub Shaft which was driven by a 1/4 HP electric motor through an infinitely variable hydraulic transmission. The speed Of the metering unit could be varied between 0 to 1600 revolutions per minute. The seed—chamber was driven from a stub shaft through a variable speed V belt drive which permitted differential drive between the cell—ring and the seed-chamber. Figure 10 shows a close up Of the seed metering unit in Operation with the seed hopper and seed passage removed. Figures 11 and 12 are the end and side view assembly draw— ings Of the seed metering head. The construction and Operational details Of the seed metering head are described as follows with reference to the assembly drawings (Figures 11 and 12). 30 .35 9:33: comm BEoEteaxm of. *0 .5633th 329.33 23628 1|.m onfiwfim 25.8 =8. 38%. :8. .5 .2560 .H .2560 oEozoofi 2:282”... A m3; 2 wk”: 032:; one: 16:01 .8on .3630 comm J ta: 91.5 .3qu 2:30:31. . . 2.. oc 9.2202 .3on 95¢ :00 III Snot; ,i . . _w 2396»: 1.: IN 33 . 3:2; v.33”. 3on 9:1 9:33: I 31 Figure 6.-—Centrifugal seed metering machine Showing the metering head. Figure 7.—-Centrifugal seed metering machine showing dr1ve arrangement. Figure 8.——Seed metering head at impending metering slot and cell alignment Figure 9.——Seed metering head at complete metering Slot and cell alignment. 33 Figure lO.——Seed metering head during Operation. 34 ASOH> one wcflzmpmv j 3w>02w¢ «unto: owwwv >4m§mmm< omu4m m4x< m>_mo mmm2_mo cwmfixo ommm ozE 4.50 02E ozEmhws. QJmfm zozbwuw ommm 35 02.x oziwhmz 92.1 :3 mo Illi/ 8.6 02.552/ Jon owwwi/ ozEem .1350 ll) .26 "ESSA d3: Sum 02:45.6 mpmwu.._m w4x< mama mmmZ_mo .\ \\ F mmm2mu.._m m>_mo 023 JJNU 02.220 mmmidio ommm >mzoo .>o:.zoo .. om w e o e o \ 3.50 w. m ._<»zuz_mmaxm _ / o . e . mm m \ mime m. .__zoo o o o . v m o 360 ¢~ o E . o o lo, 00. U I . A“ M o _ o 9.0.. _ e 1 no. x T _ t o: m _ m E D. _ .. m. _ b ON. 57 TABLE 3.--Effect Of a 2" wide baffle on seed damage. Test No. 1 Corn: Chesters Hybrid KV 35A (Medium Flat). Seed-Chamber Rotation: 1:1 with metering—ring and cut-off. Speed in Weight of Weight of Per cent cells/min. sample, gms damaged seed damaged gms seed (a) with baffle 1260 215 40 18.6 (b) without baffle 1250 256 21 8.2 Remarks: The % inch Sheet metal baffle was mounted just above and slightly ahead Of the cut-Off pawl tip to relieve the excessive centrifugally induced seed pressures from the cut-Off pawl. The results indicate an increased seed damage with the baffle. It seems that the baffle restricts the seed—chamber causing additional seed accumu- lation near the cut-off pawl. Observations under strobe lights confirm this. . calculating the number of cells required in a horizontal plate to maintain the same accuracy at other seed metering speeds. Comparative tests between conventional and experi- mental machines indicates that the conventional machines exhibit a decreased seed metering accuracy with increased metering speeds. The experimental machine, however, exhibits an increased metering accuracy with increased metering speeds within the desired seed metering Speeds of 400 to 1100 cells per minute. The experimental machine 58 TABLE 4.——Seed metering accuracy and seed damage of conven- tional planter A. ._‘ Test No. 14: Corn Used: Chester Hybrid KV 35A Medium Flat Number of Cells in Plate: 16 Cell Dimensions: 43/64" — 15/64" - 19/64" Floor Plate Groove Depth and Position: .051” or > 3/64" facing towards cell Amount of Corn in Hopper: 3 lbs. % Time in Number Seed Damaged % Average No. Seconds of Seeds Rate/ Seeds Average Seed DrOpped Min. Cell Fill Damaged I Speed Setting (Cell Rate 377.5 Cells/Minute) 1 60 381 381 1 2 60 373 373 5 3 60 395 395 6 4 60 391 391 6 5 60 386 386 3 100.00 0.99 6 60 382 382 1 7 60 386 386 2 8 60 373 373 5 9 60 383 383 4 10 60 378 328 5 666' 3828 3828 38 11 Speed Setting (Cell Rate 563 Cells/Minute) l 45 393 524 5 2 45 398 531 2 3 45 414 552 2 4 us 396 528 7 5 45 413 550 4 95.60 1.04 6 45 414 552 4 7 45 409 546 2 8 45 398 531 5 9 45 394 526 4 10 45 410 547 7 H50 4039 5387 E? 111 Speed Setting (Cell Rate 752 Cells/Minute) 1 30 334 668 5 2 30 338 676 3 3 30 328 656 4 4 30 337 676 4 5 30 350 700 5 90.60 1.20 6 30 353 706 3 7 30 344 688 5 8 30 343 686 4 9 3O 336 672 5 10 “39 345 690 3 300 3E08 6816 HI :2. 1a. P... ..\ 59 TABLE 5.-—Seed metering accuracy and seed damage of conven— tional planter B. Test No. 15: Corn Used: Chester Hybrid KV 35A Medium Flat Number of Cells in Plate: 20 Cell Dimensions: 39/64' — 16/64" — 21/64" Floor Plate Groove Depth and Direction: .0735" or <5/64" away from cells Amount of Corn in Hopper: 3 lbs. Time Plate Seed Seed Avg. %Avg. % Avg. NO. (Sec.) Rev. Dropped Damaged cells/ cell Seed min. fill Damage I (Speed Setting (2" Pully) 1 60.00 15 309 — 2 60.30 15 305 — 3 60.00 15 321 — 4 60.20 15 312 — 5 60.00 15 308 — 300 103.50 0.00 6 60.10 15 307 — 7 60.10 15 313 - 8 60.30 15 313 — 9 60.30 15 310 — 10 60.00 15 308 - 601.30 I50 3106 ‘ 11 Speed Setting (3" Pully) 1 54.40 20 400 — 2 54.30 20 406 1 3 54.40 20 406 — 4 54.10 20 399 — 5 40.70 15 301 — 422 101.20 0.09 6 40.70 15 309 1 7 40.70 15 303 - 8 40.80 15 309 — 9 40.70 15 302 1 10 40.80 15 310 — —.—-—— ——_ _ 461.60 170 3445 3 be. ........u n; .. . . . .. . l .. t . ..:..... . .. i. p _ P... vii. his... _\ .J 60 TABLE 5.——(Continued) Time Plate Seed Seed Avg. %Avg. % Avg. NO} Secs. Rev. Dropped Damaged cells/ Cell Seed min. Fill Damage III Speed Setting (4" Pully) 1 30.60 15 300 — 2 30.60 15 296 — 3 30.50 15 290 1 4 30.60 15 296 - 5 30.60 15 296 — 589 97.90 0.102 6 30 50 15 295 1 7 30.50 15 290 1 8 30.50 15 289 — 9 30.60 15 294 — 10 30.69_ .12 291 : 305-60 15 2937 3 IV Speed Setting (4%" Pully) 1 26.20 15 283 1 2 26.40 15 285 — 3 26.30 15 282 — 4 26.35 15 298 — ’ 5 26.15 15 285 — 684 96.10 0.141 6 26.30 15 283 1 7 26.40 15 288 l 8 26.35 15 298 — 9 26.35 15 291 — 10 26 40 _12 290 1 263.20 15 2883 4 V Speed Setting (6” Fully) 1 19.90 15 273 — 2 19.90 15 277 — 3 19.90 15 266 2 4 18.65 14 234 1 5 19.80 15 272 — 905 87.40 0.20 6 26.70 20 358 — 7 26.40 20 332 — 8 26.40 20 347 1 9 26.50 20 350 1 10 26.60 20 333 1 230.75 I74 3042 6 a l.n.. Fruit. 5.0. . .. . 4 t4 ,6 61 TABLE 6.——Seed metering accuracy and seed damage of conven— tional planter C. Test No. 16: Corn Used: Chester Hybrid KV 35A Medium Flat Number of Cells in Plate: 24 Cell Dimensions: 43/64" — 14/64" - 19/64" Floor Plate Groove Depth and Direction: .059" or < 4/64" groove toward cells. Amount of Corn in Hopper: 3 lbs. Plate Time Seeds Seeds Avg. % Avg. % Avg. NO. Rev. Secs. Dropped Damaged cells/ Cell Seed min. Fill Damage I Speed Setting 1 24 60.80 572 4 2 14 35.60 341 — 3 14 35.40 325 2 4 14 35.50 331 2 5 14 35.60 341 3 568 100.00 .50 6 14 35.40 346 l 7 1Ll 35.50 334 2 8 20 50.70 474 3 9 14 35.50 335 l 10 14 35.50 347 _1 I66 395T50 3746 19 II Speed Setting 1 16 27.10 370 2 2 16 27.30 382 2 3 16 27.10 372 4 4 16 27.10 369 4 5 16 27.10 363 4 850 95.60 .80 6 16 27.10 365 6 7 16 27.10 362 2 8 16 27.10 359 1 9 16 27.00 363 l 10 16 27.10 363 __3_ 166 271.10 3668 29 III Speed Setting 1 16 20.30 354 2 2 16 20.20 336 3 3 16 20.20 338 2 4 16 20.20 351 2 5 16 20.40 342 2 1136 91.00 .84 6 16 20.30 341 4 7 16 20.20 337 3 8 16 20.40 397 4 9 16 20.30 361 4 10 16 20.30 335 3 I66 202:80 3492 29 .__ ml _ 72.51..-. F14... I ..l. l r . l ... u . 62 TABLE 7.-—Effect of cut-off pawl tip weight on metering accuracy and visible seed damage. Corn: Chester Hybrid KV 35A Med. Flat 9.26% (W.B.) Moisture Level. Freshly Received from Seed Company Cut—off: Open top single leaf Spring Seed—Chamber Rotation: 1:1 with cell—ring. Speed Total no. TGSt samflie Gfiog 3:39 NO. cells/ cells Total Broken Damaged e er min. passed wt., gms. wt., gms. % no. % Test No. 9. Cut—off Pawl Tip Weight 28.8 gms. 1 400 1104 364.00 0.30 — 1072 97.1 2 609 1831 646.00 1.30 0.20 1843 101.1 3 810 537 201.70 1.50 0.75 561 104.2 4 1020 526 202.70 7.20 3.55 554 105.2 5 1250 893 334.50 11.00 3.28 927 103.7 6 1425 1278 471.20 30.50 6.46 1250 98.0 7 1550 727 272.50 22.30 8.18 700 96.5 Test No Cut—off Pawl Tip Weight 16.2 gms. 1 400 602 221.50 0.30 0.15 628 104.3 2 600 603 219.00 0.30 0.16 621 103.0 3 805 603 225.00 0.60 0.28 637 105.6 4 1010 605 229.50 3.25 1.41 650 107.0 5 1200 1212 473.50 11.50 2.33 1347 111.0 6 1420 612 230.00 11.00 4.75 659 107.5 7 1570 615 219.00 12.30 5.60 630 102.5 Test No Cut—off Pawl Tip Weight 6.8 gms.* 1 416 496 173.00 1.0 0.58 496 100.0 2 610 517 204.50 0.5 0.25 589 114.0 3 860 583 248.70 0.7 0.28 715 123.0 4 1040 525 222.30 1.3 0.59 634 121.0 5 1260 525 216.90 1.9 0.88 629 120.0 6 1335 567 270.30 5.3 2.00 759 134.0 *Note: The cut—off spring folded and machine stOpped functioning at 1400 cells per minute. - - 2. 6w 63 continued to meter seeds at speeds up to 1550 cells per minute. This unconventional behavior is of considerable importance, since the detrimental effect of speed on meter— ing accuracy has been a major problem with conventional planters. The controlled seed—cell exposure and the increased centrifugal force at higher speeds are responsible for increased accuracy at higher speeds. The seed damage increased at higher speeds in both the conventional and experimental machines (Tables 4, 5, 6 and 7) but compared favorably for the experimental machine. Higher seed damage in conventional planters moved the metering curves further below the 100 per cent meter— ing level whereas in the experimental machines additional damage tended to bring the curve closer to the 100 per cent level. If we consider a 100 i 5% seed metering accuracy as our only goal, the following maximum seed metering speeds were permissible among the four machines. Planter Max. Metering Speed Make A- 16 Cell Conventional 570 Cells/Min. Make B- 20 Cell Conventional 720 Cells/Min Make 0- 24 Cell Conventional 930 Cells/Min. Experimental 16 Cell 1550 Cells/Min. These tests clearly exhibited the superior performance of the experimental machine over a wider range of metering Speeds. The relatively flatter performance curve of the 1... m“ 64 experimental machine indicated that increased speed had less effect on its performance. The force exerted by the cut—off pawl tip on the cell seemed to have an important bearing on metering accuracy and seed damage. Observations under strobe lights indi- cated that a heavier cut-off pawl tip reduced the number of extra seeds passing under the cut-Off pawl. Tests were conducted using three different tip weights of 28.8 grams, 16.2 grams, and 6.8 grams, and a constant spring force of 170 grams (Table 7). The three different tip weights induced different centrifugal force on the cell and affected the performance of the machine. Figure 19 has two sets of curves, one exhibiting seed damage and the other seed metering accuracy, for three different cut-Off pawl tip weights. The heavier cut—off tip lowered the metering accuracy and brought the curve closer to the 100 per cent line. It also increased the seed damage. The 6.8 gram tip stopped functioning at 1,250 cells per minute due to the backward folding of the Spring. There seems to be a definite inverse relationship between seed damage and the number of excess seeds moving under the cut-off. Since it is desireable to reduce both the seed damage and the excess seeds, the selection of the cut-off tip weight would depend on a compromise. In a commercial machine, seed damage can be easily noticed by the farmer. The pawl weight would have to be based on 65 .Z w o. .m .moz kmwh ox. mu .m Map—.902 zmoo wo<2oh_oo._m> 203.096 owwm coon w...:z.2 mun. flqwo comm ooo. OOON 000. 000. -x.mH ossmnm 0 ¢ T (D 'e \ a) H o - 666 N6. 00 TI 6:5 mdu FIG—m; a: qulhDo 1 6253 Oh. women. ozEam “2.20350 1 00 _; 02km owmmm 02:... Aquolmwmigio owmm Ob 3T PERCENT SEED METERING ACCURACY UPPER THREE CURVES \ 1 ON. 66 the amount of seed damage that could be safely tolerated without adverse customer response. The movement of a few excess seeds under the cut-Off is not so detrimental from the operational point of View in corn planting. Based on the above remarks, perhaps the 16.2 gram cut-off pawl may be desireable. An additional factor which contributes to the pawl force is the force due to the Spring. Performance tests with a 6.8 gram pawl and 270 grams and 1,000 grams spring force were conducted (Table 8). Figure 20 illustrates the test results. Time did not permit the testing of additional Spring forces. The weaker spring exhibited a steadily increasing accuracy whereas the stronger spring exhibited a dip in the performance curve at the middle of the speed range. The seed damage was higher with the stronger spring. It seems that spring force is more effective at Slow metering speeds and weight induced force is more effective at higher speeds. This leads to the conclusion that a prOper combination of spring force and weight force will maintain close to a 100 per cent metering accuracy over the total range of metering speeds and within desireable seed damage limits. Seed Damage Tests were conducted to establish seed damage on corn, prior to an impact and after an impact on a steel 67 PERCENT VISIBLE SEED DAMAGE LOWER TWO CURVES .m. 0 N. .moz hmwh .oxom 522.202 zmoo 504240 omww 024 >o 20:05.5 055m 83 SS 88 88 con. ooo _ “.52.: 5a 3.8 8... com. 89 com com 09. 0 A . _ q mutt ‘2‘; 3 00 ll \ N 00 W.» .. o\\ 0 olllmz._._00..5> 20:05.5 owwm coon 8o» 88 82.. con. 89 ~55: «ma mime ooe. o8. coo. com com oov A a _ A _ . q _ A 0 1 . v~ nompzoo V o - m w \ \< .353 2.. I e \ \ .85... 5458 02.56 9.5-50 .mzéo Nu 52”.; a: to..5o 235 2 Swan anoSOémngo 8mm 1 0 «III .__>z< .55 ell ~55 15.6 I o .8458 52:. t c. PERCENT TOTAL SEED DAMAGE 71 w G n .moz 2.me .mm:...m.02 o\oN_ ._.< 2100 20 mkmmh zo_hCooqw> zo_howaw omww --.mm mpsmflm coon coon 83 38 o8. 08. “.52.: mun. 3.3 8: com . ooo. com com 8.. 4 u A d _ — q — o _ E 6 III. .II- IIII III m Jomhzoo o .9. o. n c. G\ «:45 2.. L memo“. 5528 2,..QO toéao ¢ m «.245 ~.~ a.» ”€0-50 23»: m .u. ouuam to.»:o-¢umzz< 435 m _ 9 526 :56 P _ magma 52:. m G h 72 TABLE 9.—-Effect of impact surface on seed damage (germination test). Corn: Chester Hybrid KV 35A Medium Flat. 10% Moisture Level (W.B.), Stored for One and a Half Years. Cut—off: Open Top Single Leaf Spring with Nylon Pawl Tip (2.2 gms weight). Seed—Chamber Rotation: 1:1 with metering-ring and cut—off. Cells/ Velocity Sample Visibly Damaged No. min. ft./ min. Size Damaged Germination Seed Seed Poor None no. % Test No. 3. Impact Surface: Cloth Chute (No Impact). 1 400 1000 M24 — l 7 8 1.87 2 600 1500 577 ~ 7 11 1.91 3 800 2000 577 2 3 13 18 3.12 N 1000 2500 409 2 6 5 13 3.18 5 1200 3000 “80 U 7 8 19 3.95 6 1360 3400 660 7 14 21 42 6.36 7 Control —— 1200 — 6 2O 26 2.17 Test No. 4. Impact Surface: Steel Plate 18” from Ejection Center 1 400 1000 48” - 8 3 11 2.27 2 600 1500 438 — 3 8 1.83 3 800 2000 565 2 6 9 17 3.01 4 1000 2500 456 5 7 5 17 3.72 5 1200 3000 367 u 7 3 14 3.81 6 1320 3300 454 5 6 16 27 5.95 7 Control -- I200 - 6 2O 26 2.17 73 TABLE lO.—-Effect of impact surface on seed damage (germination test). Corn: Chester Hybrid KV 35A Medium Flat. 12% (W.B.) Moisture Level. Stored for One and a Half Years. Cut—off: Open Top Single Leaf Spring with Nylon Pawl Tip (2.2 gms. weight). Seed—Chamber Rotation: 1:1 with metering-ring and cut—off. Cells/ Velocity Sample Visibly Germination Damaged No. min. ft./min. Size Damaged Poor None Seed Seeds no. % Test No. Impact Surface: Cloth Chute (No Impact). 1 400 1000 572 1 2 8 11 1.93 2 600 1500 639 1 1 11 13 2.04 3 800 2000 611 4 4 7 15 2.46 1000 2500 623 6 4 11 21 3.37 5 1200 3000 522 — 4 12 16 3.07 6 1300 3250 493 3 11 21 35 7.00 7 Control —— 568 4 l 8 13 2.29 Test No. Impact Surface: Steel Plate 18" From Ejection Center 1 400 1000 521 — 6 3 9 1.76 2 600 1500 586 — 5 7 12 2.05 3 800 2000 520 1 5 4 10 1.93 4 1000 2500 583 4 4 6 14 2.40 5 1200 3000 605 4 5 12 21 3.47 6 1250 3110 451 10 9 12 31 6.90 7 Control -— 568 4 1 8 13 2.29 74 21 and 22 indicate a rapidly increasing seed damage within the machine at metering speeds of over 1,200 seeds per minute. Figure 23 illustrates seed damage tests (Table 11) on corn at 10.5% W.B. moisture level. A slightly heavier cut-off pawl (15.5 grams) was used for this test. The corn used for tests in Figures 21 and 22 was stored for about one and a half years. The tests of Figure 23 were carried out with fresh corn received from the seed company. This was done to assure that the results would be comparable to actual planting conditions. The results exhibited the same general pattern. At 1,100 seeds per minute the seed damage within the machine was 1.4% and the impact on steel surface resulted in an additional damage of 0.9%. There seems to be some error around the 1,000 seed per minute speed. From Tables 7 and 8 we find that at 1,000 seeds per minute the actual seed damage within the machine is only .13%, whereas the impact damage is 3.05%. At 1,200 seeds per minute, both the seed damages are about equal (3.14% and 3.49%), which is contrary to general expectation. 75 .m G h .moz hmmh .mmahmaz oxo 0.0— ._.< 2100 20 hmm... zo_.—.._._oo._w> 203.096 owwm oooc coon 000m 003 88 con. ooo. “.52.: 5.. «.33 com. ooc. o8. ooo. com com ooc _ _ . _ . _ A _ _ _ _ O I ~ .ompzoo v o m \ \ .25 2.. demo“. 5328 ozfiam “.3150 1 2.8.9 2.5-50 .25.: 44:24.. :85; :28: 1 o. .H. omwam umolhaolmmmzdxo owmm 1 «III ..:>z< 4mm; .. N olll mezzo 50.6 .wodu a :m #045,: w I-.mm mpsmflm PERCENT TOTAL SEED DAMAGE 1V— 76 TABLE 11.——Effect of impact on seed damage (germination test). Corn: Chester Hybrid KV 35A Medium Flat. 10.5% (W.B.) Moisture Level. Freshly Received from Seed Company. Cut—off: Open TOp Single Leaf Spring with Nylon Pawl Tip (2.2 gm. weight). Seed—Chamber Rotation: 1:1 with metering—ring and cut—off. Cells/ Velocity Sample Visibly Germination Damaged No. min. ft./min. Size Damaged Poor None Seed Seed no. % Test No. 7. Impact Surface: Cloth Chute (No Impact). 1 400 1000 476 — 4 14 18 3.78 2 600 1500 581 l 3 18 22 3.79 3 800 2000 499 1 6 16 23 4.60 4 1000 2500 511 — 4 15 19 3.73 5 1200 3000 579 7 6 26 39 6.74 6 1550 3875 680 13 18 59 90 13.20 7 Control —— 500 — 3 15 18 3.60 Test No. Impact Surface: Steel Plate 18" from Ejection Center. 1 400 1000 501 — 7 13 20 4.00 2 600 1500 516 — 9 14 23 4.45 3 800 2000 535 4 9 11 24 4.48 4 1020 2550 495 5 10 18 33 6.65 5 1200 3000 602 9 6 24 39 6.49 6 1450 3625 400 19 6 27 52 13.00 7 Control —- 500 — 3 15 18 3.60 VII. APPLICATION OF RESEARCH This study was conducted to establish the feasibility of the new concept of planting. The experimental machine and the test results have proved that the concept is practical and meets the desired operational planting requirements. The farm machinery industry has been faced with the high speed planter problem for many years and is very receptive to practical solutions. While this study has been financed by a grant from the Ford Tractor Division and the patents originating from this study would be under control by the company, it is hOped that this new concept will generate original thinking among engineers engaged with planter development. At this stage it is only possible to suggest broad recommendations about a field machine. Additional informa— tion will be required about the performance of this machine with other seeds and planting rates before spe- cific recommendations could be made. Information will also be required about the ejection velocities to imbed different seeds in different soil conditions. Based on the available information, a field seed metering unit with only two rotating members has been pro- posed in Figure 24. The unit has its own set of gears to provide the speed differential between the cell-ring and 77 78 I SEED HOPPER —‘ Ill // fl ‘ ”‘1 - METERING—0W7 F3 DRIVE SHAFT / /‘ / / / / / I / x / / ..._.. / é ; .m. _ I _ \ / .. _ (L \ MAIN DRIVE SHAFT/ ,. O r C _ \ j = <\\\\\\\\\\:\‘ MACHINE BASE FRAME Figure 24.--— Suggested Seed Metering Unit for a Field Planter. 79 meteringaring. It incorporates the baffle type feed-in arrangement to maintain a constant amount of seed in the chamber during Operation. It provides means for easy changing of cell—rings for different kinds of seeds, by unscrewing a molded cap. This cap has a feed intake hole in the center and it also serves as a seed passage wall. The metering unit is driven from a single shaft to simplify power input. The metering unit is mounted on the machine frame by a bracket which permits the tilting of the hopper. The machine could be either ground driven or tractor P.T.O. driven. The metering unit need not be mounted very close to the ground since the distance will hardly effect the placement accuracy. The suggested sketch for a field planter is one of the many possible approaches for a field machine, each offering some advantages. Further work on the experimental machine with other seeds may help to evaluate the different possible designs. VIII. SUMMARY The use of centrifugal force for seed metering, ejection, and placement is feasible. The experimental laboratory machine was successfully tested up to a metering speed of 1,100 cells per minute. In terms of planting travel speed, 1,100 cells per minute is equivalent to planting 22,400 plants per acre in 40 inch rows at 7.02 miles per hour. It is considered that a maximum planting travel speed of 7 m.p.h. would be desireable for current farming practices. The study has proved that planting requirements are well within the scope of the new concept and that it offers a potential for further increase in planting Speeds. The effect of high planting speed on metering accuracy in the experimental machine is contrary to that of conventional planters within the speed range of 400 to 1,100 cells per minute. The metering accuracy increases with an increase in metering speed in the centrifugally dependent concept. Ejected corn seeds with 2,750 feet per minute initial velocity (1,100 seeds per minute metering speed) did not exhibit a significant reduction in germination after impact on a steel plate at a distance of 18 inches from the ejection point. It can be concluded that impact of corn 80 81 seeds with stones during planting will not effect germina- tion up to ejected velocities of 2,750 feet per minute. Seed damage, within the machine, increased with an increase in metering speed. It compared favorably with seed damage in conventional planters at each level of metering speed. Seed damage increased rapidly above the 1,200 cells per minute metering speed. Seed damage at 800 cells per minute averaged about one half per cent and it increased to an average of 1.5% at speeds of 1,200 cells per minute. Seed damage within the machine is affected by the cut—off pawl force. This force can be best pro- vided by a combination of spring and weight induced forces. Seed damage and excess seeds passing under the cut-off pawl have an inverse relationship. Amount and distribution of seed in the seed chamber have an effect on seed damage. Excess seeds in one corner of the chamber can induce very high centrifugal force and unbalance in the machine. The seeds are sub- jected to about 175g acceleration at 1,100 cells per minute metering speed. Uniform seed distribution can be achieved in the seed-chamber by rotating the seed- chamber with the cell-plate and not with the metering—ring. Such an arrangement will also result in a simpler mechanism with only two independently rotating members. The amount of seed in the chamber during operation can be successfully controlled by a pressure equalizing baffle as described earlier in Chapter V. IX. RECOMMENDATIONS FOR FURTHER STUDY 1. The centrifugal concept of seed metering needs to be tried in the laboratory on all the other kinds of seeds which are planted with conventional planters. This concept offers the possibility of planting cotton without delinting the seed and this should be studied. 2. Additional work is necessary to study the com— bined effect of spring and weight induced cut—off pawl pressures on metering accuracy and seed damage. 3. The required ejection velocities to imbed dif- ferent kinds of seeds in soils, representative of actual field conditions, has to be established. 4. A field machine is required to study the field performance and to experimentally determine the point of seed impact with respect to the furrow openers. 82 REFERENCES 83 10. REFERENCES Andrews, H. C. (1959) "The Effect of Kernel Dimensional Characteristics and Planter Plate Speed on the Accuracy of Hybrid Seed Corn,” M.S. Thesis. Miss. State College. Autry, J. W. and Schroeder, E. W. (1953) "Design Factor for Kill Drop Planters," Agri. Eng. Vol. 34, No. 8, Aug. 1953. Bainer, R. (1960) "Precision Planting Equipment," Agri. Eng. Vol. 28, No. 2, Nov. 1960. Barmington, R. D. (1948) "The Relation of Seed, Cell Size, and Speed to Beet Planter Performance," Agri. Eng. Vol. 29, No. 12, Dec. 1948. Barmington, R. D. (1956) "Metering Devices and Test Results of Some Foreign and Domestic Sugar Beet Planters," Journal of American Society of Sugar Beet Technologists, V01. IX, No. 1, April 1956. Brandt, R. G. (1963) ”Development of a High Speed Precision Planter," ASAE Paper No. 63—134. Church, Lillian (1935) "History of Corn Planters,” Bureau of Agri.: Engineering Information Series No. 69. Washington D. C., U. S. Dept. of Agri., 1935. Copp. L. G. L. ”A Precision Seeder Operated by Suction," N. Z. Jour. of Agri., Res. 1961, 4(3u4) 441-447. Dhuicq, M. A. (1958) ”Development of the Grain Drill, British, American, and Continental," a paper presented to the Institution of British Agricultural Engineers, Feb. 18, 1958. Dhuicq, M. A. (1958) ”Do We Need Precision Drilling?” Farm Mechaniza- tion, Vol. 10, March 1958. 84 }-- 11. 12. 13. 14. 15. 16. 17. 85 Evers, P. N. (N0 date) "Investigation of Longitudinal Spacing of Beet Seed in the Row in Precision Drilling" NIAE translation. Futral, J. G. and Allen, R. L. (1951) "Development of a High Speed Planter," Agri. Eng. Vol. 32, No. 4, April 1951. Giannini, G. R., Chancellor, W. J., and Garret, R. E. (1967) "A Precision Planter Using Vacuum Seed Pickup," ASAE Paper No. 67—126. Gill, W. E. (1960) "Corn Population and Tillage Treatment," ASAE Paper No. 60—124. Guelle, C. E. (1967) "Precisior Planting of Beets and Corn," Agri. Eng. Vol. 28, No. 2, Feb. 1967. Gunkel, W. W., and Hubbard, G. R. (1967) "Analysis and Design of a Precision Seed Tape Planter," ASAE Paper No. 67—127. Hansen, H. V. (1966) ”Planter Trends and Predictions for 1975," ASAE Paper No. 66—163. Harmond, J. E. (1965) "Precision Vacuum Type Planter Head," U.S.D.A. Agri. Res. Service Publication 42—115, Oct. 1965. Hubbard, G. R. (1963) "A Method for Precision Planting Vegetable Seeds," M.S. Thesis, Cornell University, 1963. Johanson, W. W. and Teale, R. E. (No Date) "Engineering Aspect of Corn Rows," AE Dept. Series No. 6, Ohio Agri. Expt. Station, Wooster, Ohio. Kohler, H. J. (1957) ”Possibilities of Precision Drilling by Suction in Drills," Land Tech. Forch, Munich. 1957. 7(5)1l7. Larsen, W. E. (1962) "Precision Planting of Coated Seeds," Crops and Soils, March 1962. 23. 24. 25. 26. 27. 28. 86 Morton, C. T. and Buchele, W. F. (1959) "Development of Commercial Beet Planters," American Society of Sugar Beet Technologists. Proceedings of the Tenth Regional Meeting, Chatam, Canada. Richey, C. B., Jacobson, P., and Hall, 0. W. (1961) Agricultural Engineers Handbook. McGraw Hill Book Co. Roth, L. 0., and Poterfield, J. G. (1960) ”Some Basic Performance Characteristics of a Horizontal Plate Seed Metering Device," Transactions of the ASAE, Vol: 3, No. 2. Author Unknown (1961) ”Stanhay Seed Spacing Drill," Farm Mechaniza— tion, April 1961. Sweetman, I. C. (1957) "A Suction Operated Precision Seeder," N. Z. Jour. Sci. and Technol., Sec. A. 38 Weller, K. (1958) ”Completely Pneumatic Evenly Spaced Drilling of Single Seed," Land Tech. Forch. Munich. 1958 8(1).