A STUDY OF THE FHR‘ESHING OF WHEAT EY CENTREFUGAL FQRCE Thesls for “w Degree 05 DE. D. MICHIGM STATE UHWERSETY Benson J. Lamp. Jr. 1959 l FRIEIS C0,; LIBRARY Michigaz' State Umvcrsity This is to certify that the thesis entitled A STUDY OF THE THRESHING OF WHEAT BY CENTRIFUGAL FORCE presented by Benson J. Lamp has been accepted towards fulfillment of the requirements for Ph.D. degree in Agricultural Engineering Date March 18, 1960 . ‘N~_ 4.....__ ,. .A STUDY OF THE THRESHING OF WHEAT BY CBNTRIFUGAL FORCE By Benson J. Lap, Jr. AN ABSTRACT Submitted to the College of Agriculture, College of Engineering end School of Advanced Graduate Studies of Michigan State University of Agriculture end Applied‘Science in partial fulfillment of the requirements for the degree of DOCTOR.OF PHILOSOPHY Depsrnnent of Agricultural Engineering Year 1959 Approved by Benson J. Law. Jr. An Abstract Wheat (five varieties), rye, corn and soybeans were completely threehed by the application of centrifugal force. Wheat wee threehed at ell mature noisture conditions. Only exploratory research was accomplished with the other grains. An experimental batch-type centrifugal threeher which was capable of holding 25 to 50 head samples was designed. This machine developed peri- pherel speeds up to 250 miles per hour which was sufficient for complete threshing. me experimental technique and equipment permitted the deter- nination of the total weight of grain threehed at any selected speed. These data were used to establish threshing forces required to achieve various percentages of threshing. . Centrifugelly threehed grain could be readily cleaned by air, since only chaff reaained with the grain. When threehed without air resistance, the grain did not require cleaning, since the chaff raained attached to the straw. Quality of centrifugally threehed wheat was superior to hand threehed wheat as measured by germination tests. At higher peripheral speeds, high moisture grain required additional rubber matting to prevent kernel damage during the dissipation of kernel kinetic energy at the thresher housing. Performance comarisons were obtained between centri fugel and conven- tional threshing. These comparisons established cylinder adjustments equiva- lent to the centrifugal force required to achieve various percentages of threshing. Conventionally threehed grain had twice as much chaff to be re- moved as centrifugally threehed grain. the last to be threehed kernels, when centrifugally threehed, weighed up to 28 percent less per kernel than the average kernel weight. There were no differences in kernel weights of combined grain separated at any of eight zones under the cylinder and rack or of unthreshed grain. Germination of centrifugally threehed grain was superior to combined grain. theoretical threshing equations were developed for impulsive and non- impulsive acceleration. values of the threshing force for use with the for-Ilse were established. Other factors occurring in the equations need to be determined. Concepts and equations of motion were derived for possible use in the development of continuous-flow centrifugal threshers. A STUDY OF THE THRESHIHG OP WHEAT BY CBNTHI FUGAL FORCE 3? Benson J. Lamp, Jr. A ruesrs Submitted to the College of Agriculture. College of Engineering and School of Advanced Graduate Studies of Hichigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Agricultural Engineering Year 1959 Benson J. Lamp. Jr. candidate for the degree of Doctor of Philosophy Final Examination: October 23. 1959. at 1:30 PM. Agricultural Engineering Conference Room Dissertation: A Study of the flashing of wheat by Centrifugal Force Outline of Studies: Hajor Subject: Agricultural Engineering Minor Subjects: mechanical Engineering Applied Mechanics Biographical It-s: Born: October 7. 1925. cardington, Ohio. Undergraduate Studies: Ohio State University. 1943; continued 1946-1949. Graduate Studies: Ohio State University, 1950-1952: continued 19510-1958; Michigan State University. 1958-1959. Experience: Student Assistant, Ohio State University. 1949; Junior Engineer. Soil Conservation Service, 1949; Instructor, Ohio State Univer- sity. 1949-1952: Assistant Professor. Ohio State University, 1952-1959: Assistant Professor, Ohio Agricultural Experiment Station. 1956-1959: Research Assistant, nichigen State Univer- sity, 1958-1959: Associate Professor, Ohio State University and Ohio Agricultural Experiment Station, 1959: Agricultural Engineer and Consultant. several companies from 1950 to present. Haber of ‘rau Beta Pi. Ga-a Sig-a Delta. Sig-a Xi. American Society of Agricultural Engineers. American Society of Engineering Education. Pro- fessional Engineer. AW Many individuals have assisted in making possible the research work reported herein. The author wishes to express appreciation to all who con- tributed directly and indirectly to make the research and graduate program challenging and rewarding. Particularly he would like to mention those mud below. 1):. A. W. Ferrell, head of the Agricultural Engineering Department. ex- pressed personal interest and concern and made available a research assis- tantship and funds for experimental equipment. Professor E. D. harden, head of the Agricultural Engineering Department at Ohio State University, encouraged the author and made possible a leave of absence to coqlete the program. he also made available research equipment and labor for conducting the field threshing and separation studies. 1):. Wesley P. Euchele of the Agricultural Engineering Department, serving as the author's major adviser. wee a continued source of inspiration and provided guidance readily whenever requested. "Ofessor E. 1'. McCally, as section head of power and machinery and guidance co-aittee muber, took unusual interest in acquainting the author to various problmas and solutions. Dre. Carl W. Hall and Merle L. Esmay of the Agricultta'al Engineering Department, Dr. William Bradley of Applied Mechanics Department, and Dr. L. L. Otto, chairmn of Mechanical Engineering Department, served as guidance co-ittee mnbers. The latter two professors proved to be chal- lenging teachers in several subject utter courses in the author's minor studies. ii its Perm Crop Department's wheat breeder. Dr. Everett Everson, contributed time as a consultant and made available wheat s-ples. The staff of the Agricultural Engineering lesearch Laboratory gave helpful assistance any times during the research. Mr. J-es cawood never ceased to give personal assistance whatever requested and expressed more than normal interest in the research. his uncanny ability to keep tab of equipment uas appreciated. Dr. George line of the Applied Mechanics Department gave assistance in derivation of the motion equations. Dre. Willi- Stout and Fred Iuelew of the Agricultural Engineering Depart- ment contributed photographic assistance. Professor lalph 1.. Vanderslice of the Mechanical Engineering Department supervised the high speed photography. It. I. E. hoekhart of the School of Packaging cooperated in making avail- able seme equipment for physical determinations on straw. Fellow graduate students gave frequent assistance and moral support. Mention should be .de also of the excellent attitude of the author's wife and childrml during times when the author as less than the husband and father he desired to be. IIBLB OF CONTENTS Imwmou . O O O O O O O O O O O O O O ObJ.Ct1v¢seeeesesees mm 0’ ”mum C O O O O C O O O O 0 Evolution of the Threshing Processes Results of Research with Contemporary, mt..h.r. O O O O O O O O O O O O O O O O O O O I O Completeness of threshing Mhintenance of grain quality Cylinder-Concave Effect of threshing upon separation and cleaning . Power requirements for threshing Results of Research with Experimental Threshers . . . . Crap Characteristics Significant to Threshing . . . . . SPECIFIC mamas OF “sum 0 O O O O O O O O O I O O 0 m0“ 0? msmm C O O I O O O O O O O O O O O O O O O 0 ‘Methods for Obtaining the Threshing Force . . . . . . . Mechanical processes . . . . . . . . . . . . . . . Impulsive acceleration . Non-impulsive acceleration Energy Relationships . . . . Impulsive acceleration . lon-hnpulsive energy . RESEARCH EQUIPMENT AND TECHNIQUES Laboratory Research . . . . . Threshing in commercial centrifuge Experimental batch thresher Grain physical characteristics Page 10 12 17 19 21 25 25 26 28 30 30 31 32 32 32 34 60 iv Page Straw physical characteristics . . . . . . . . . . . . . . 41 Field Research . . . . . . . . . . . . . . . . . . . . . .-. . 43 Simultaneous conventional and centrifugal threshing . . . 43 Conventional threshing and zones of separation . . . . . . 45 EESDLTSANDDISCUSSIOEOPEESULTS ....... 49 Laboratoryxesearch......................49 Centrifugalthreshing .................. 49 Effect of moisture upon threshing force . . . . . . . . . 51 Effect of variety upon threshing force . . . . . . . . . . 61 Effect of method of force application . . . . . . . . . . 61 Cheffruoval......................66 Kernelseparationbysize .............. 74 Kernelgermination....................74 Exploratory thrashing of corn . . . . . . . . . . . . . . 78 Physical Characteristics of Grain . . . . . . . . . . . . . . . 78 Kernelweightenalysis..................78 Kernel weight by location in the head . . . . . . . l. . . 82 Kernel moisture variations within a wheat head . . . . . . 82 StrawPhysicalProperties................... 82 Coefficients of friction . . . . . . . . . . . . . . . . . 87 Breaking force and tensile stress . . . . . . . . . . . . 87 FieldResearchEesults.................... 87 Cylinder adjustment and threshing loss . . . . . . . . . . 87 Cylinder adjustment and separation (rack) loss . . . . . . 88 Cylinder adjustment and visual kernel damage, germinationandtestweight . . . . . . . . . . . . . . 88 Cylinder adjustment and grain separation .t th. cy11nd“ O O O O O O O O O I O O O 0 Cylinder adjustment and location of grain separation over the rack Cylinder adjustment and shoe load Peed rate and grain separation at the cylinder Peed rate and shoe load Zone of separation and kernel weight Cowarison of Centrifugal to Conventional Threshing Threshingforces .............. Subsequent operations Threshable moisture conditions . . Variable stage thrashing . . . . . manusornsuscn ... Speeds and Porces Required for Threshing Revolutions per minute required at uniform kernel radius for threshing Revolutions per minute required at variable W1 M“. O O O O O O O O O O O O O O O O O Threshing force developed at variable kernel radius Theoretical Equations of‘lhreshing rlaoarrrcu. ASPECTS OF MMS'M Grumman Concepts Theoretical Motion Analysis for Rotating Cone Symbols, definitions and asmtions Motion equations without directional vanes Motion equations with direction vanes Utility of equations 0 O O O O O O O O O O Page 94 94 98 99 99 99 99 99 103 104 105 106 106 106 106 108 108 111 111 113 113 114 116 118 Winners FOR mar RESEARCH “mums O O O 0 O O O nuances mu 0 O O O O O O O Page . 119 121 123 125 130 LIST OP FIGURES Pigure Page 1 Syst-s for threshing grains which are in use or . have been used experimentally (Segler, 1957) . . . . . . . 11 2 Schaatic of the Wilde Harvester, which wee cosmonly used in England for harvesting of small grains . . . . . . l6 3 Side and edge view of three heads of Genesee wheat . . . . . . 22 4 Schenatic diagram of a head, spikelet and fertile floret ofwhaatshowing thenamesofparts . . . . . . . . . . . . 23 5 Sch-atic diagram of kernel, chaff and attachment, showing direction of force application .-. . . . . . . . . 24 6 Tapered wood plugs and metal test cups used to mount wheat heads in a co-ercial centrifuge . . . . . . . . . . 33 7 Commercial centrifuge used for exploratory centrifugal thr..h1n8 O O O O O O O O O O O O O O O O O O O O O O O O O 33 8 Drive parts of experimental centrifugal thresher . . . . . . . 36 9 Threshing head, showing method of attaching the grain . . . . 36 10 Unthreshed grain mounted in threshing head . . . . . . . . . . 37 ll Straw condition after coqlete threshing . . . . . . . . . . . 37 12 Straw tensile strength wee determined by use of Schopper testing-chine ...................... 42 13 Straw frictional data were obtained with a tilting board device, surfaced with galvanized metal . . . . . . . . . . 42 14 Canvasses were used to collect total discharge from the rack during field combine tests . . . . . . . . . . . . . . 44 15 Straw discharged over the rack was analyzed to determine rack and cylinder losses by use of a rethresher . . . . . . 44 16 Housing which was attached to the combine concave to collect grain, chaff and straw separated by the cylinder at the cmav. O O O O O 0 O O O O O O O O O O O O O O O O 0 I O 0 a7 17 Grain and straw passing through the rack was collected by a wooden tray with five zones inserted under the rack . . . . 47 18 Soho-tic diagram of combine as adapted for determining thelocationofseparation ................ 48 Figure 19 20 21 22 24 25 26 27 28 29 30 31 32 33 34 35 viii Grain centrifugally threehed at 44.8 percent kernel moisture showing some chaff attached . . . . . . . . . Samples of grain centrifugally threehed . . . . . . . . . Relationship of threshing force to percent of threshing for 6300.09 "hat 0 O O I O O O O O O O O O O O O I O 0 Relationship of peripheral cylinder velocity to percent of threshing for Genesee wheat . . . . . . . . . . . . Relationship of threshing force to percent threshing for 8”.“ "but 0 O O O O O O O O O O O O O C O O l. 0 Relationship of cylinder peripheral velocity to percent threshing for Seneca wheat . . . . . . . . . . . . . . Relationship of threshing force to percent threshing_for B “cm“ "but 0 O O O O O O O O O O O O O O O O O O 0 Relationship of threshing force to percent threshing for three conditions of surface moisture (Genesee wheat) . Relationship of kernel moisture to threshing force required for 98 percent threshing (Seneca wheat) . . . Relationship of straw moisture to threshing force required for 98 percent threshing (Seneca wheat) . . . . . . . . Variations existing in the relationship of threshing force to percent threshing (Seneca wheat) . . . . . . . . . . Effect of grain and variety upon the relationship of threshing force to percent of threshing . . . . . . . . Relative quantities of a bearded wheat threehed at various speeds of rotation (rpm) . . . . . . . . . . . . . . . Effect of method of holding upon the relationship of threshing force to percent of threshing for high moisture Genesee wheat . . . . . . . . . . . . . . . . Effect of method of holding upon the relationship of threshing force to percent of threshing for dry Senecawheat .... Effect of air resistance upon the relationship of threshing fbrce to percent of threshing . . . . . . . . . . . . . Resultant straw and grain condition after threshing without air resistance . . . . . . . . . . . . . . . . Page 50 50 52 53 54 55 56 57 58 59 60 62 63 64 65 67 68 in Figure Page 36 The two threehed heads at the bottom appear similar to the unthreshed heads at the top when threehed without air ru1.t‘nce O O O O O O O O O O O O O O O O O O O O O O O O 68 37 Total and clean grain threehed at various speeds of rotation(rpm)Geneseewheat . . . . . . . . . . . . . . . 70 38 Relationship of speed to quantity of chaff and grain rsmovedfordrystraw ................... 71 39 Relationship of speed to quantity of chaff and grain rmaovedfordew-ladenstraw . ..... . ... . . . . . . 72 40 Relationship of speed to quantity of chaff and grain ruovedforwetstraw................... 73 41 Coqarative forces required to thrash high moisture wheat andcorncmitrifugelly .................. 79 42 Rernel weight-frequency histograms for five wheat "r1.t1“ “d r’. 0 O O O O O O O O O O O O O O O O 0 0 0 O 80 43 Relationship of kernel position on the head to kernel weightforCeneseewhaat ................. 84 44 Relationship of cylinder adjustment to threshing loss for a reap bar cylinder in dry Seneca wheat . . . . . . . . 89 45 Relationship betwemt cylinder adjustment and separation (rack) lossfordrySenecawheat ................. 91 46 Relationship of cylinder adjustment to visual kernel m“. for dry sen.“ what 0 O O O O 0 O O O I O I O O O O 93 47 Effect of cylinder adjustment upon amount of grain separationatthecylinder . . . . . . . . . . . . . . . . 96 48 Influence of cylinder adjustment upon location of separationwithinacombine . . . . . . . . . . . . . . . . 97 49 Effect of straw and chaff feed rate upon location of grain separation withina combine . . . . . . . . . . . . . 101 50 Speeds of rotation required for various degrees of threshing and threshing forces (radius of rotation, one foot) . . . . 107 51 Relationship of kernel weight by position within the head to speeds of rotation required for threshing Genesee wheat . 109 52 Relationship between kernel position and relative kernel weight to threshing force applied (constant speed of tonum) O O O O O O O O O O O O O O 0 O O O O O O O I O O 110 53 Sch-atic die am of r osed centrifu 1 thrasher and syst- of assumetftaxas fgrozhaoretical ca culatione . . . . . . 112 LIST OF TABLES - Table Page 1 Relationship between cylinder speed and average weight of kernels removed when threehed by experimental thresherendcentrifuge .................. 75 2 Germination of Seneca wheat when thrashed by different methods and at various kernel moistures . . . . . . . . . . 76 3 Comparative germination of Seneca wheat when threehed by combine, centrifugal thrasher and hand . . . . . . . . . . . 77 4 Weight frequency statistics for random sample of we... W‘t O O O O O O O O O O O O O O O O O O O O O O O 81 5 Weight-frequency distribution by spikelet location on headforGenesaewhsat ................... 83 6 Relationship of kernel position within spikelet to average andextr-eweightsofceneseewheat . . . . . . . .- . . . . 83 7 Kernel moisture by spikelet location for three heads of 8”.“ “at O O O I O O O O O O O O O O O O O O O C O O O O 85 8 Physical characteristics of Genesee wheat straw under veriousconditions ..................... 86 9 Effect of cylinder adjustment upon threshing and separation lodses . . . . . . . . . . . . . . . . . . . . . 90 10 Average effects of cylinder adjustment upon threshing endseparationlosses ................... 90 11 Effect of cylinder adjustment upon kernel damage, germinationandtestweight ................ 92 12 Amount of grain separation at the cylinder at various cylinderadjustments .................... 95 13 Average percentages of grain separated at zones 1 and 2 for all cylinder velocities and clearances . . . . . . . . . 95 14 Shoe load as influenced by cylinder adjustment . . . . . . . . 98 15 Amount of grain separation at the cylinder by zones atvariousfeedrates ................... 100 '16 Shoeloadatvariousfeedrates 100 17 Cooperative threshing forces and cylinder adjustment for 96, 98 and 99 percent thrashing of dry, mature wheat . . . . . . 102 xi Table Page 18 Porces required to thresh 100, 98, 95, 90 and 80 percent of total grain at various moisture contents . . . . . . . . 131 19 Combinethreshingdata .................... 136 20 Combine separation data -- cylinder adjustment, straw to grain relationships and losses . . . . . . . . -. . . . . . . 138 21 Combine separation data -- separation of grain, chaff and .tr.‘ by m.‘ 0 O O O O I O O O O O O O O O I O O O I O O O 139 22 m1,‘1' Of "rt‘nc‘ O O O O O O O O C O O O C“ 0 O O O O O O 0 1‘1 Threshing, the process of freeing the seed. from its attachsnt and covering (husk), is a necessary process in harvesting of practically all seed, feed and food crops. This process has been called the most inortant of all grain harvesting processes because it influences the functioning of the subsequut separating and cleaning processes. The history of threshing dates back to the beginning of grain crops. Inerous referncas to grain and threshing are found in the Bible. It would be natural to expect, therefore, a rather coqleta understanding of the basic nature of threshing. Such is not the case, however, although the present state of the art of threshing and threshing design has been developed to the point where it is generally conceded to be satisfactory. Existing machines, however, are sensitive to many crop and operational variables. They are large and bulky, often causing traction and storage ‘probl-s. With their principles of operation, they are not adaptable to hillside operation. Particularly the present state of design is questioned what one realises the harvesting -chine weighs 300 to 400 times the eqle being threehed at any time. As research directed toward increasing basic knowledge about the threshing process unfolds, new threshing methods may evolve with design, operational and functional advantages that coqletely obsolete conventional threshing techniques. active The objective of this research was to contribute to the fundamental knowledge of the basic nature and requir-mnts of the threshing process, with special qhasis upon the developmmtt of new concepts of thrashing. REVIEW OF LITERATURE Evolution of the Threshing Processes Conjecture would lead one to state that man first threehed grain rubbing his hands together on individual heads. This method, while very efficient and damage free, was very slow and laborious. Means to increase the rate of threshing and reduce the labor requirement were obviously sought (Church 1939, 1947). One means for increasing the threshing output per unit of labor was by bunching the grain and striking the bunch (or bundle) on a stationary object numerous times. Another approach was to lay the unthreshed material on a solid, stationary object over which animals trod until the beating and rub- bing of the animal hooves threehed the grain. One of these methods was used by Gideon of Biblical account. Indeed in certain relatively non-mechanized countries of the world the latter method is still in use today (Reg 1957). The previous methods did not separate the straw or clean the chaff from the grain. The processes of separating and cleaning required time equal to that required for threshing. Man next wondered how these processes could be made easier. The concept of unthreshed grain moving into a stationary threshing device and the threehed nmterial passing on into elements achieving separation and cleaning was efficiently developed in the historical stationary separator-thresher so col-on in America the first third of the 20th century. But still much time and effort was required for gathering the unthreshed grain and moving it to the stationary thrasher. Reduction of time and effort was made possible by the conventional and contemporary combine-harvesters. This brief history is given only to emphasize the evolutionary nature of threshing development. Prom it, however, one conceives that the basic principles of threshing the grain have not changed during the evolution to date (Church, 1939). The evolution essentially has seen only a change in the method of handling the unthreshed and threehed materialsufrom I sta- tionary batch during the early stages of development to a continuous flow during later development. The threshing eleaents- have been commune moving object forcing the material to be thrashed against a stationary object. The means of achieving the relative motion between the two threshing mmabers has been obviously different. Changes in power source, configuration and meter- isle of construction of the threshing members and operating speeds have been but a few of the evolutionary developments. history shows that the vacutm engine development arrested the develop- ment of the internal combustion engine (Lichty, 1939). Perhaps the contu- porary moving-stationary threshing method has likewise slowed, hindered or perhaps even prevented the development of improved threshing processes. Results of Research with Cont-porary, Cylinder-Concave Threshers Many research results are to be found in the literature relative to the perforunce of the contqorary threshing method. Little is available, how- ever, concerning design variables. To sunarise these research findings, it appears desirable to suggest criteria for good threshing and than to report findings in light of these criteria. The following criteria are suggested for acceptable threshing: (l) Coqlate threshing (2) hintenance of grain quality (3) Enhancmaent of the subsequent processes of separation and cleaning (4) Minimum power requith with ample capacity (5) Fractional under a wide variety of field and crop conditions Eleteness of thrashing McCuen (1943) in a study of 58 farmer-operated machines stated "practi- cally all operators were very careful about getting all the kernels out of the heads." The cylinder losses averaged 10 to 14 percent of total machine losses. All machines analysed were operating in wheat or cats. Johnson (1959) and Mitchell (1955) have shown that completeness of threshing is possible at moistures wall above 20 percent kernel moisture in wheat. Arnold (1958 and 1959) did similar work in barley and oats with the s-a result. Likewise corn and soybeans have been comletaly thrashed at moistures above 40 and 20 percent respectively (Law, 1956, 1957). Small legume and grass seeds, however, are mach more difficult to thresh. Evml though the cylinder be adjusted to give maximum aggressiveness, thrashing losses my be 20 to 45 percent (Bainer, 1955). Booker (1952) had losses up to 50 percent in clover. Reports have been received of farmers who run the clover straw through the combine the second time, apparently obtaining suf- ficient seed to make the operation profitable. It is particularly inortant to have low seed moistures when harvesting the small seeds, if completeness of threshing is to be achieved. Beiner (1955) states "Under certain conditions the type of cylinder may have some effect, although there is no conclusive evidence that any one type is consistently superior to the others." Johnson (1953) found that for the same cylinder speed and concave clearance, the reap cylinder had somewhat higher threshing loss than a flail cylinder. his work was with four wheat varieties. Prom the literature and farmer experience one would conclude that the presmlt designs for threshing are able to achieve coqlete threshing when properly adjusted for most crops. The small seeded legumes offer the greatest threshing challenge. Maintenance of gain quality Losses in grain quality resulting from the threshing process have been measured by test weight, percent visible damage, percent loss in germination, parent loss in germination energy, and percent loss in dry matter by dif- ferant investigators. The relative iqortanca of these measures depends upon the use of the grain. Germination tests are inortant when the ultimate use is as seed, while percent loss in dry matter is the most imrunt measure of feed grain. All of the measures frequently have inortance' for market grain. . The extent of quality loss depends upon the grain physical characteris- tics, the kernel moisture content at threshing and the severity of the threshing effort. Since most operators adjust the threshing effort to levels resulting in complete threshing and the grain physical characteristics are . fixed for any crop and variety, the kernel moisture content becomes the only independent variable influencing grain quality losses. Berg (1949) investigated damages from threshing in winter and spring wheat, rye, barley and oats at moistures up to 38 percent. Damaged kernels were found in all i-adiately threehed sanles with kernel moisture above 20 percent. The damage was found to be independent of whether the moisture was from unripenass or rainy weather. Grain cut at moisture above 20 percent and permitted to dry prior to thrashing showed no decrease in germinative and shooting ability. The decrease in germinative and shooting ability appeared to depend upon kernel daaga resulting from thrashing. Johnson (1959) reported losses in test weight of soft winter wheat caused by both delay in harvest and harvesting at high kernel moistures. The test weight reduction was 0.23 pound per bushel per day after the grain had ripened to 27 percent. Germination reduction ranges and visual kernel dange were reported at various moistures. Atteqts were nde to minimize damages by selecting favorable combinations of cylinder and concave coverings. Rubber angle bar cylinders, steel concave bars, and grated and solid concaves were evaluated. lo combination significantly reduced kernel damage. Re con- cludes "it would appear from the standpoint of resulting grain condition, wheat threshing met be limited to grain moistures below 20 percent." belong (1942) conducted field studies in barley. Re varied the threshing effort of spike toothed, rasp, and angled bar cylinders. The grain moisture varied in the 12 to 15 percent range. The rasp and angle bar cylinders gave greater visual dange than the spike tooth design, with the rasp having slightly greater damage than the angle bar. British research showing the effect of threshing effort and crop mois- ture contents upon the germination ability of oats, barley and wheat was reported by Arnold (1958, 1959) and Mitchell (1955). They concluded that a rapid deterioration of germination occurred when kernel moisture was above 19 percent and that the overall effect of the drum speed was greater than the concave setting. Large seeds, particularly those of dicotyledonous plants, are extr-ely susceptible to damage as reported by Rainer (1955). Ilia work suggests that complete threshing will cause excessive damage with spike tooth cylinders (16.4 percent moisture). The amount of damage for a given threshing effort increases rapidly as the moisture content of the beans is reduced. Ea indi- cates that special bean threshers have been built with two spike-tooth cylinders in series in order to reduce damage. The first cylinder was oper- ated at a lower speed than the second. The Russian. Eolganov (1958), attqted to reduce grain da-ges and has reported the research results of a two cylinder machine threshing wheat. The first stage cylinder had a peripheral speed of 7 to 20 'meters per second (1400 to 4000 feet per minute) while the second stage cylinder ran at 30 meters per second (6000 feet per minute). The kernel weight obtained from the first stage was greater than that of the second in all tests. Also, mechanical damage was 2-1/2 times less in the first stage. "Research institites should pay the most serious attention to the ques- tion of mechanical da-ge to seed and its effect on germination", wrote another Russian, Usenko (1952). The germination on the collective farms was as follows: 16 percent of the total quantity had germination from 95-100 percent: 34.1 percent, 90-94 percent: 36.5 percent, 85-89 percent: and 13.4 percent, less than 85 percent. The principal cause for the decreased viabi- lity was mechanical damage during harvesting and threshing. The growth vigor of undamaged seed was mach better than of mechanically damaged seed. Russian data show the yield from mechanically damaged seed is appreciably reduced. Grass and small hard seeds like crimson clover and the lespederas were generally not seriously damaged by the necessary aggressive threshing effort required, reported Park (1956). He found that while hand threehed clover had often 100 percent hard seed, the percent was seldom over 25 percent for combined threehed seed. Bainer reported 10 to 20 percent germination damage when harvesting alfalfa seed with e 5.2 to 6.8 percent moisture. Park did not indicate seed moistures in his report, although it surely was much greater than that of Bainer's work. The r-oving of kernels of corn from the cob (a process co-only called shelling but which can properly be called threshing) frequently results in damage as reported by Burroughs (1953). Pickett! (1955). Morrison (1955). Berkstrom (1955), and Law (1957). Visual damage increased with cylinder speed particularly over 2500 feet per minute. Damage was relatively indepen- dent of concave clearance. The extent to which the visual damage results in a dry utter loss has not been adequately researched. although some prelimi- nary work suggests 5 to 10 percent loss (Miles, 1956 and Law, 1958). Eeitshu (1928) reported the germination of soybeans collected from farmer operated combines varied from 56 to 98 percent. In an effort to re- duce harvesting losses, Law (1956) combined soybeans at 18 percent moisture. Although visual damage was minor, germination damage was very- severe. he concluded that for oil use, the germination loss would not be inortant. In si-ary, careful attention mast be given during threshing to prevent grain huge. The moisture limit same to be 19 percent for mny of the crops. The practical limit of threshing for feed corn depends upon the extent to which kernel da-ge is a dry utter loss. Effect of threshing 2232 smration and cleaning Ideal threshing would integrally achieve separation of the grain from the straw and chaff. Threshing that does not perform partial separation places severe d‘nds upon the rack. Likewise, threshing that breaks the straw badly and strips all the glues from the head is undesirable because it increases the cleaning load. Men (1932) recorded 60 to 70 percent separation at the cylinder in stationary threshing separators. This percentage range was obtained for several different concave arrang-ents. Johnson (1953) conducted extensive laboratory tests with four wheat varieties and two cylinder types, determining the amount of separation at the cylinder. Holding constant cylinder speeds, the percent of separation did not change significantly as the concave clear- ance was decreased, although the weight of chaff and short straw increased as the clearance was reduced. He found average percentages of separation for the rasp cylinder of 69, 66, 62 and 68 for Vigo, Thorne, Butler and Trumbull varieties respectively. similar respective data for the flail cylinder were 56, 56, 46 and 51. Moisture ranges were in the range fro. 12 to 15 percent, and the feeding rate was 35 pounds per foot of cylinder width. Under alifornia conditions, Goes (1958) found that the percent separa- tion of barley at the cylinder was 85, 71 and 57 for feed rates of 80, 120 and 160 pounds per minute respectively. These data are an average of concave clearance and cylinder speed of 5700. The combine was equipped with a 30-inch in length rasp bar cylinder and the barley moisture was 7 to 9 percent. At a feed rate of 80 pounds per minute, separation was 92, 86 and 78 percent at clearances of 1M, 1/2 and 3/4 inches respectively. The shoe chaff-load de- creased from 20 to 5 percent of total feed rate in going from 1/4 to 3/4 inch clearances. Goes also shows the effect of cylinder speed upon separation. With a clearance of 1M inch and feed rate of 120 pounds per minute, 80, 75 and 59 percent of the grain was separated at 5700, 6800 and 3800 feet per minute cylinder speed. The overall range of separation was 40 to 92 percent. Men (1963) showed that increasing the threshing effort by increasing cylinder speeds increased total combining losses. core (1958) suggests thet increasing the threshing effort reduces total losses, since greater separation is obtaining during the threshing function. Further, Johnson's work (1953) does not agree with that of' Goss relative to the effect of cylinder clearance upon. separation at the cylinder. Perhaps the crop, machine and operating variables accent for the differ-ice. . Under the most favorable condition, Goes (1958) achieved 92 percent separation. 12 this could be increased another 6 er 7 percent, perhaps the separate separating mechanism of conventional combines could be eliminated. This possibility has challenged hussian and German designers to place 2, 3 and lo cylinders in series (Segler 1957). See Figure 1. Performance results of these threshing mechanisms are not available. Power requiraents for threshig Men (1932) determined the effect of rate of feeding upon power re- quit-ante of separator cylinders. lie found nearly straight line relation- ships between feed rate and power requirnente. The concave arranguent had a noticeable effect upon power. A typical relationship can be expressed by equation 1: P . eosc . tea (1) in which P : horsepower feed rate in pounds per minute. c lurroughe (1956) gave power requir-ents of 1.0, 1.8, 2.2 and 3.8 horse- power at feed rates of 32, M, 52 and 68 pounds per minute respectively. His work was with a 5-foot rasp bar cylinder. -11.. Figure 1. Systems for threshing grains which are in use or have been ._ ' used experimentally (Segler 1957) -12- higsby (1959) found that solid ate-ed wheat required more power for threshing than hollow st-ed. The power equations were P (horsepower) = 1.59 + .0639 c (2) for solid st-aad wheat and p : 1.35 + .0368 c (3) for hollow et-ed wheat. The units for the feed rate c were reported as bushels per hour of grain. Straw-grain ratios approached 1, so that the grain feed rate is approximately equal to the straw feed rate. Dolling (1955) determined that over a 5-second period the power varied from a minus 2 to 9 horsepower. lie reported also a power balance for an qty achine wherein 2.6 horsepower or 20 percent of total power was re- quired for the threshing mechanism. Results of Research. with Experimental Threshers The Germans have researched considerably with the chop-threshing method. A forage or field harvester chops the straw and grain and blows it into a wagon. The wagon carries the chopped material to a stationary separator. Barrie (1956) reviewed the nethod, citing certain advantages and disad- vantages. Prom this review and research reports by Segler (1952 and 1955) and Volski (1954) an indication of the perforlasnce efficiency was determined. with cutting lengths of 110, 56 and 22 millimeters (4.3, 2.2, and 0.9 inches respectively) and a peripheral speed of 28.2 meters per second (5600 feet per minute) 80-96, 71-83 and 51-68 percent of rye, oats and wheat were thrashed out respectively. This method did not increase the amount of mechanical damage. When the length of cut was over 60 millimeters (1.6 inches), the damage was lower than that of the conventional thrasher. The -13- mini.- 1ength of cut for cereals was about 22 millimeters (0.9 inches); beans, 55 millimeters (2.2 inches). Host damage was due to cutting. The germination capacity of chop-threehed wheat was 3.5 percent higher than that harvested by conventional methods. Direct harvesting losses were re- ported somewhat lower than direct combining. ‘Segler (1953) indicates that the chop-thresh method is limited because straw moisture is too high for i-ediate storage. Air blowing over the heads. at 60 percent relative huidity would have 70-80 percent relative hi-idity near the grass level. The grain and the straw at the top would have 15 percent moisture, whereas the lower straw might have 35 percent and any green uterial would have 75 percent moisture. The chop-threshing method has been used some in the prinarily dairy state of Wisconsin. lo perforaance data are available. Clingernn (1956) and new (1956) have used a field harvester at different cutter speeds and knife arrang-ente to thresh corn, soybeans and wheat. Satisfactory thresh- ing of corn was achieved, although damage was high. Complete threshing of soybeans was achieved, but the mini.- crackage was slightly less than 5 percent. In 16.1 percent moisture wheat, 1.9-2.5 and 7.1-8.2 percent losses occurred with 0 and 3 knives respectively. In 13 percent moisture wheat, threshing losses varied in the range 1.7-2.9 percent and was independent of cutter speed. Separation was difficult. An endless belt threshing mechanism was built and tested by Ramblin (1952). Although built as a cereal plot harvester because of its easy-to- clean design, the author concluded merous advantages over the conventional cylinder thrasher nechanism. Along these were as follows: -11.- (1) leither concave adjustment nor speed was at all critical. (2) Will not wrap under conditions causing this trouble in conven- tional cylinder. (3) The operator can choose the state in which to leave the straw - . either beat up or nearly whole. (4) The high speed parts run at only 60-65 percent of the speed of conventional cylinders. (5) Tractor mounted combine feasible. The latter advantage se-ed possible because the conventional rack was com- pletely eliminated and cleaning was done by a separate machine. Pour acres of wheat, barley, oats, mustard and. linseed were harvested at moisture ranges from 17 to 21 percent. Machine losses varied from 1.8 to 6 parent. Booker (1952) reported an experimental endless belt thrasher for clover harvesting. Two endless belts rotating in opposite direction gave fair feeding and excellent threshing. When the upper belt turned 300 feet per minute back- ward and the lower belt 500 feet per minute forward, 95 percent of the seed was threehed. The machine tended to roll the straw and clog when higher moisture seed was threehed. )elt life was too short also. Buchele (1953) developed an experimental thrasher for small, hard to thresh seeds. This nchine achieved threshing action similar to the belt machines by continuously rubbing the seed against a perforated screen formed into a cone. lelt strips rotating on a shaft held the material against the screen and gave motion to the material. All of this action took place in the perforated rotating cone where the seed was separated as it was threehed fro. the straw. The cones and the rubber blade ineller although rotating in tin ' I -15- same direction, had different peripheral speeds. A device somewhat similar to this was used for separation in Germany also (Segler, 1957). The Wild nodal 50 harvest Thresher (1950) was of siqlified design and sold in angland for some time. See figure 2. The principal unique feature was the method of threshing. The straw was not cut but rather a threshing rotor best the grain from the head. The rotor consisted of a series of discs mounted on a shaft, each disc carrying radial vanes staggered on ad- jacent discs. It was claimed that the staggering of the vanes causes the grain to be beaten rapidly from side to side. The rotor also acts as a fan, blowing the grain and chaff into a swirl chamber. The chamber was designed to permit the chaff to be blown out, leaving clean grain and unthreshed heads. Another rotor with blades was located at the button of the swirl chamber. This rotor passed through a fixed comb finalising threshing. The success of this harvester is not known and performance data are not available. link (1958) gave a progress report on the development of "new prin- ciples in conbining". Threshing was accomplished by feeding the material into a fan. Subsequently, the threehed grain was separatedin a rotating cone device similar in concept to that described previously. One of the claims for the machine was its unusual capacity, up to 600 bushels of wheat per hour. Also it was clained that the new principles could work on the hillside. lone have been sold co-arcially to date (1959). hirli (1956) placed individual heads of wheat into a co-ercial cen- trifuge and found that coqlete threshing was possible. The limited work suggested the need for exploration of this method of threshing. -15- wawunonficn new vcoawnu 5" non: hang-coo ooh £0.33 .uouno>unm 2233 can we canon—850m 35on :35 mo .N onowa 80h: grant-ah “#3...” 02.8: memos-o 8203 32(’ (£00 ¢Oh0¢ else rose 5.8... 50 E30 25.. nonunion «8156 .....s... 23.. glam -17- Crop Characteristics Significant to Threshing Germans to threshing is the time of maturity of the crop. There is usually no. reason to harvest the grain crops prior to the maxi-um dry matter yield. Scott (1957) determined that wheat yields increased regularly until the kernel moisture ranged from 38 to 46 percent. The moisture decreased quite regularly until it reached a point slightly less than 40 percent, after which it decreased very rapidly. After a a to 6 day desiccation period, the moisture fluctuated under the influence of the environment. Scott's work was in agreement with that of other researchers. Miles (1959) found that corn harvested as shelled corn at 28 percent kernel moisture gave the highest dry matter yield. His work reports a lower value than most researchers, but he felt this was partly caused by the small samples used by other investigators. The Russian Kolganov (1958) reports that the work of separating the kernel from the stem was 60 centimeter grams (0.052 foot pounds) for heavy grains and 120 centimeter grans (0.106 foot pounds) for light grains. Seventy- five percent of large heavy grains were ruptured at an impact speed of 36 meters per second (7100 feet per ninute). The cylinder peripheral speed for threshing was determined by equation 4: V 3 1 Ah . (a) (1+!) Goa-I. u m V : peripheral speed of cylinder, centimeters per second Ag 2 work of separation in centimeter grams d : angle between the direction of peg mow-sot and the axis of the grain ' B -'-' coefficient of recovery on impact of the grain on the cylinder peg m : grain mass in grans per second squared per centimeter Values of m were from 20 to 60 x 10-6 grams per second squared per centimeter for wheat. B was taken as 0.2 for 15 percent wheat moisture and 0.1 for 10-12 percent wheat moisture. An average value of Coed was 0.64. Zoerb (1959) determined the impact energy for rupture of wheat. In the moisture range from 13 to 20 percent, 15 to 25 inch pounds of energy were re- quired. lie reported the modulus of elasticity of the wheat kernel to vary from 63,000 pounds per square inch at 13 percent to 210,000 pounds per square inch at 20 percent. -19- SPECIFIC OIJICTIVBS 0! RESEARCH The literature review presents some challenging possibilities for func- tional performance of threshing mechanisms. Can a threshing method be de- veloped that integrates the threshing and separation functions and minimises the cleaning requirements? Can a threshing mechani- be developed that will remove grain without damage as soon as the grain is physically mature? now can the thrasher mechanism take advantage of the physical seed variation, psrbps giving seed sising integrally with threshing? Can the threshing, separation and cleaning functions be independent of the earth's gravity, thereby eliminating the need for special hillside combines? Achievuent of any of these possibilities in an economically feasible .nner would offer excellent potential benefits to agriculture. The experimmltsl work in which centrifugal force was used for threshing is the only coqletely new concept reviewed. Further, if achievable, it could meet several of the challenges stated in the previous paragraph. It would , appear worthy of exhaustive research to determine its capabilities. The review indicated that the literature was practically void of the- ories concerning threshing. Threshing theories could serve an inortant function in challenging future researchers and should be developed. finally more should be known about conventional threshing, with any new approaches correlated to the conventional methods. Therefore, the specific objectives of this research were: (1) Develop theories of threshing (2) ripinre the concept of centrifugal threshing (3) Correlate the conventional threshing methods with results of -20. centrifugal threshing. The research was confined principally to wheat harvesting, in order that the research could be intensified. - 21 - manor “338“ Definition and Force Required The process of detaching and freeing the seed from its natural binder is defined as threshing. This process requires the breaking of the seed attach- ment and overcoming the resistance of adjacent coverings until the seed is free. Figure 3 shows side and edge views of three heads of Genesee variety wheat. Figure It presents the names of the various parts of a wheat head. Threshing in the case of wheat is breaking the rachilla and freeing the kernel of glue and l- frictional resistance. If either the pedicel or the rachis breaks with chaff-like material attached to the kernel, threshing is not coqlete. The force required to break the rachilla and overcome the glume and 1-a friction is defined as the threshing force F and can be expressed in equation form as follows: r 8 c A d" (5) in which F is threshing force in pounds c is a constant relating to method of applying the force A is the cross sectional area of the rachilla and d' is the stress required to break the rachilla in pounds per square inch. The constant C considers also the direction of applying the threshing force as shown in Figure 5. Figure 5-A shows the threshing force exerted so that the rachilla is in direct tension. There is no separation of the glass with this loading until the kernel begins motion relative to the pedicel. The threshing force will be maximum with this nnner of loading. - 22 - Side View / Edge View Figure 3. Side and edge view of three heads of Genesee wheat -23.. 3an we mean: one wagon? Juana mo no.3: 33.3w one uoaoxwmn one... n no Seemed—u oaugnum .e 0.3me humour. wn__._.m_mu .5495“ 04m... mo mem E30 30:0: 9:20 .230 2:53.. .868 _ l/l.\x 028 (I _0C..0¥ oEEm... Silly mEoom , 323:5 * . 3.33m 60:? -214- A A TENSILE > 8 BENDING C COMPRESSION Y SENDING 8 SHEAR Figure 5. Schematic diagram of kernel, chaff and attachment, showing direction of force application -25- The force bands the kernel about the point of attacuent when applied in the direction shown in Figure 5-3. It separates the glues and causes the rachilla to be stressed through bending. The condition of loading shown in Figure 5-0 would shear the rachilla and should require the minimi- threshing force. C values for the loading of Figure 5-A shall arbitrarily be assigned a nuerical value of 1. Values for the other positions will need to be deter- mined experimentally. . 8 Determining finite values for the area of the rachilla would be a time consuing and difficult task. It would vary with seed physical character- istics, not only among varieties but also within a given variety. lven within a given head of wheat, considerable variation would exist. The unit stress for breaking the rachilla would appear principally de- penth upon its moisture content. The stress would depend also upon the time interval between maturity and harvesting. From the standpoint of using equation 5, the product of the area and the unit stress would be usable and much easier to obtain. This product is defined as the breaking force f. lqustion 5 then takes the form: F:Cf (6) Methods for Obtaining the Threshing Force Meal processes The mechanical processes of rubbing, stripping and coqression either singularly or in couination cause relative motion between kernels and their attacusnts, resulting in threshing. lo effort will be ude to develop theories of threshing for these processes, since the physical concepts are relatively eluutary. -25- aulsive acceleration Wewton's rule states the relative velocity after collision is equal and opposite to the coefficient of restitution (or iQsct) times the relative velocities before the collision (Becker, 1954). In symbols this expression becomes for a conventional threshing mechanisa: - 8. (Vci - Vgi) - ch - V3: (7) ' 3s (Vci ' 'ei) = Vct ' Vet (3) The syflols have the uanings indicated below. I; is the coefficient of restitution of the grain. 8. is the coefficient of restitution of the straw. 'ci is the velocity of the cylinder initially or before impact, feet per second (fps). 9‘1 is the initial grain velocity (fps). V“ is the final cylinder velocity (fps). V‘f is the final or after impact velocity of grain (fps). v.1 is the initial straw velocity (fps). V“ is the straw velocity after impact (fps). 'c is the cylinder velocity (fps). For a powered cylinder with even feed, '3‘ a v.1 and V“ e ch s Vc. Also Va is very small compared to vc and can be neglected. Equations 7 and 8'siqlify, after these substitutions, to: Vs: : Vc (1 +3“) (9) V“ : V¢(1‘|'8.) (10) The grain and straw velocities can also be obtained from the laws of acceleration and are equal to: vgf : Vu‘l-(‘Qg (11) -27- v.3 : Vu-l- (at). (12) The products of the acceleration and time for grain and straw are represented by (at)‘ and (at). respectively. Equating equations 9 and 10 with 11 and 12 respectively and neglecting the small term '31, the equations of the acceleration can be obtained. ‘e : vc (1;+-s.) (13) 8 _ .. s "c (1+3s) (14) to Newton's law of motion states We P r G (15) 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. If the straw and the grain had different rates of acceleration, a threshing force would evolve as: "s it. [2241.122ch <1 - m] G ‘s ‘s P : G (a8 - a.) : (16) To visualise equation 16, consider that the straw is fixed in space. If there is relative acceleration between the straw and the grain, the mass being accelerated becomes that of the kernel Egg. The accelerating kernel in turn pulls on the rachilla with a fofce F until the attacl-ent is broken. If the time of acceleration for both the grain and straw is t (seconds), equation 16 reduces to: W V P : .315. (I8 - E.) (17) -23- Clearly, the time can be expressed as occurring in a finite distance of cylinder travel, x feet. Thus: t = ,c ' (18) Substituting equation 18 into equation 17 and eliminating the time gives after rearranging and solving for the cylinder velocity r xv * rx Vc= vw(rG-r)=5"7'uw(x -z) ‘19) 8 8 I g g s Fquation 19 gives the cylinder velocity required for threshing in terms of the kernel weight, grain and straw coefficients of restitution, and the threshing force-all of which are experimentally determinable physical charac- teristics of the crop and x-a factor largely dependent upon machine design and adjustment. The equation aseues that the grain enters into contact with the cylinder at the tangent and that the contact is coqlete. lon-fllsive acceleration Suppose that a at. with head attached were suddenly accelerated. All parts would be accelerated simultaneously, provided that breakage did not occur someplace. low consider each individual rachilla which met exert the force to accelerate its kernel. This force would be: : EL": - v1) (20) c t Let two mating cylinders, turning on each other at the same speed Vc. be the mechanism that accelerates the stu. Using equation 18 and neglecting V1, equation 20 reduces to: vc : “-3-"?!- : Luv-5‘5- (21) -29- Coqaring this equation to equation 19, it is readily seen that the coefficient of restitution does not enter. Since the nuerical value of the quantity (I8 - R.) is always greater than sero but less than 1, a mechanism following equation 21 would require only m as much cylinder speed as the conventional cylinder (assuing the value of x in equation 19 and 21). The last equation, however, still has the quantity 1:, the distance through which acceleration occurs. This can be eliminated by accelerating the mass nou-rectilinssrly. For such acceleration, the acceleration is: . : —- <22) In this for-11a 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 lewton's motion equation, equation 15, the equa- tion for centrifugal force is obtained. Rearranging and solving for the velocity, the following is obtained: ’3 v, = v15? . 5.57 "a: (24) Since R is a definite quantity and W8 and vc are easily measured, the force required for threshing can be obtained. Equation 25 perhaps is more convenient to use, since 11¢ is the threshing head speed in rps. 1' he : 0.903 VW‘3 (25) - 30 - Energy Relationships ulsive acceleration The energy absorbed by a kernel can influence germination. It is there- fore iqortant to have nergy relationships for threshing processes. In addition the relationships can be used to establish power required for threshing. The kinetic energy for the grain mixture i-ediately after iqact from the cylinder is: 2 82:: v‘:2 (1 +11.) :Zwvlz c (1+3!) (26) c For most wheat varieties, the mixture ratio of grain to straw approaches 1. Using this fact and calling the total mixture weight W, equation 26 becomes: V “=2 2 2 r c Té" [(1+r,) + 04-33).] (27) It should be noted that W refers to total quantity of mixture accelerated per second and W8 refers to the total quantity of grain. horsepower can be obtained entering time into equation 27. Upon striking a concave bar, the grain and straw rebound velocities become: - v35 ; [v6 (1 +119] : vc (r‘i- a") (28) - v“, : s, [vc (1 Hip] : vc (11,-: 3.2) (29) The rebound kinetic miergy becomes: r .2673 (r, 1- 1:32)}??? [vcz (t 4- s 2):] (30) issue that W3), and W‘ are equal as are W“, and W.. Further assue that W‘ equals W. and their su is W. The rebound energy equation then becomes: ‘ w_v__;z 22 Th : [(s8 +522) +(r,+ 11.)] (31) The work done on the straw and grain becomes: 2 I. Aseuisg that I“ and I. are much usller than one, the third and fourth powers can be neglected and the work is approxi-tely: m,"z Q'zo (1 1» 3,-1.5) (:3) Unfortunately, the division of this work done on the grain and straw needs to be experimentally determined. ‘ ll -mleive energy The energy for non-inulsive acceleration is again more siqu stated, since the kernel will be leaving the straw at the velocity existing at thrashing. This velocity previously was referred to as Fe. Thus, the kinetic energy becomes: w v 2 s ..L‘- (34) 2 G This is an expression for the energy of- threshing and the energy which mist be dissipated before the kernel becomes static. When a stationary kernel arrester is installed, the energy of rebound becomes: W r : ...L g‘2 '3 (35) 2 G and the work by the kernel becomes: - wg ch Q'zc (1 - 832) (36) Ideally, it would be desirable to have an arrester that would make 83 sero and that absorbs all the kernel kinetic energy. This is true from the standpoint of kernel damage. - 32 - Rum W AID TICIIIQUFS laboratory Research Theoretical analyses indicated thet the threshing force'could best be determined by applying centrifugal force until the desired level of threshing had occurred. The threshing force would then be equal to the value of the applied centrifugal force. To determine this force, measure- mut of (l) rotational speed, (2) radius of rotation of the kernel use, and (3) the kernel weight was necessary. Threshig in couercial centrifuge uploratory threshing was accoulished in a couercial centrifuge. Individual heads of wheat were held in standard l-l/2 by 6-inch test cups by two piece, tapered wood plugs. See Figures 6 and 7. As the centrifugal force increased, the plugs wedged tighter into the cup, securely holding the straw and head at a fixed radius. Wood plugs were selected because they could be easily ruoved. After the samples were prepared and placed in the trunnions, the centri- fuge us accelerated to the lowest rpm of the sequence. The power to the centrifuge was then turned off, the cap opened, and free or threehed kernels raved. The plugs holding the straw and head were next carefully replaced 'and the cutrifuge accelerated to the next higher speed. This technique was continued for five or six speeds, after which the straw residue was searched for unthreshed grain. . The kernels threehed at each spud were counted and weighed on analytical balances with four place deciul gram accuracy. The grain and “straw were later dried at 200° F. for 68 hours in order to obtain moisture contents. -33- Figure 6. Tapered wood plugs and metal test cups used to mount wheat heads in a commercial centrifuge Figure 7. Commercial centrifuge used for exploratory centrifugal threshing -34- This equipment and procedure was not couletely satisfactory for the following reasons : (1) (2) (3) (4) The force obtained was marginal. usny times couplets threshing could not be achieved. This was true even after the input voltage to the centrifuge was increased by means of a variable voltage transformer to 140 volts. This voltage gave a maxi-ea speed of 3200 revolutions per minute. Only two or four heads could be threehed at a time, one in each cup. A test sequence required considerable time, since the centrifuge had to be stopped after each speed incruent to ruove threehed grain. The protective cup eliminated all air resistance, a condition which would be practically impossible to achieve in any con- ceivable application. merimutal batch threeher It was decided to design and construct a centrifugal threeher with the following functional rsquiruents: (1) (2) (3) (’0) Speeds variable from 1000 to 5000 revolutions per minute at. radii greater than 6 inches. capable of handling large saules, 50 to 100 heads or more at one time. Continuous collection of threehed grain. Threshing head flexible for holding the grain so that the effect of direction of force application relative to the kernel could be determined. -35- (5) Permit subjecting heads to combined effects of centrifugal force and air resistance. A circular mounting clu was positioned horizontally at the and of a vertical shaft which was held firmly in position by two flange-type bearings. The shaft was powered by an electric motor driving through a variable-speed urcury clutch and a v-belt-driven counter shaft. The direction of the power was turned 90° by twisting the v-beit between the mercury clutch and the counterehaft. The counterehaft was parallel to the uin threshing shaft (Figure 8). The mounting clan consisted of a flat 1/4 inch steel base plate, 12 inches in diameter and a flat steel top ring with outside diameter 12 inches and inside diameter of 9 inches. A hub was welded to the base plate, which permitted attaching the mounting clau to the drive shaft (Figure 9). The ring was bolted to the base plate with four 1/4 inch stove bolts. The mounting cleu was carefully balanced statically. The clau was couletely enclosed by a housing which de-accelsrated the threehed kernels and delivered them to a sloping metal drain. The discharged grain was collected and delivered by means of spouts on either side of the threshing frame to paper containers. The areas on the housing which made contact with the threehed kernels were lined with a 114 inch rubber pad in order to reduce grain dauge. See Figure 10. The housing top was made of plexiglass to permit strobotrac observations. The saule to be threehed was hand arranged between the base plate and the ring (Figures 10 and 11). The straw was usually inserted with the heads pointing radially outward. Bach head was adjusted to a fixed radius. Generally 24 head sales were used, 12 heads on each side. The clam was -36- 7! ‘ "v ——‘~ m :53“! I "7 “ . .533“- ""‘I llIl I " “ib‘. I ._ i ear“ - paw“ * n. . " .7 :W Figure 8. Drive parts of experimental centrifugal threeher Figure 9. Threshing head, showing method of attaching the grain -37- Figure 10. Unthreshed grain mounted in threshing head. The author housing was lined with a rubber pad to protect the threehed grain from damage. Figure 11. Straw condition after complete threshing tightened securely after final positioning of the heads. The base plate and ring were each coated with asbestos gasket uterial to prevent cutting of the straw. The orientation of the heads could be varied to achieve three types of loading. Host of the tests were conducted with the apical spikelet at the greatest radius as described in the previous paragraph. This mounting was previously stated to be the condition giving the moet'difficult threshing and was referred to as regular holding. Some tests were conducted by V clqing the stu portion exposed by removing the apical and adjacent spike- lets. This‘xholding wee called reversed holding. , Intermediate holding wee obtained by placing, the heads in hollow cylinders made of perforated galva- nised sheet utal. These cylinders were bolted to the base plate. The method of holding corn was considerably differut. One-fourth inch steel rods were formed with a hook on one and and were threaded on the other. These rods were keyed to the base plate. Specimens were prepared by cutting an ear of corn into 1-1/ 2 inch transverse sections. These were drilled through the cob center with a 1/4 inch bit. The specimens were inserted on the steel rod, ushered flush with the cob, and then locked in position. It was found that a test sequence of the following speeds would guerally include the coulete range of threshing: 1000, 1500, 2000, 2500, 3000, 3500 and 4000 revolutions per minute. A strobotrac was used to cali- brate the speed. The radius of the tip kernel us kept at 11 inches when regular holding us used. The test technique involved increasing the threshing speed from the lowest to the maxi-1m speed in succession. After the uchine had stabilised at (each speed, the containers were ruoved and new ones inserted on the collection spouts. The straw was ruoved and -39- analysed for unthreshed kernels after the last speed was attained. The discharge obtained at each speed incruent was processed according to the following procedure: (1) let weight of grain, chaff and straw determined. (2) Souls blown to ruove chaff. Straw, if any, us picked out by hand. (3) let weight of kernels was determined. (4) let weight of straw, if any, was determined. (5) Kernels were counted, noting visual kernel dauge. if any. (6) Grain and straw sulas were desiccated in an oven at 200° F. for 48 hours. The weighings were ude in grus with accuracy to two deciul places. Several grain smules were saved for germination tests. Grain for the original experimentation was cut by binder during the 1958 growing season and stored. Greenhouse wheat of Genesee variety was used for pre-seaeon threshing. Seneca wheat sales were obtained directly from the field during the Ohio testing (June 28 through July 13). lioistures varied from 40 to 10 percent. as hundred head sqles of several wheat varieties were collected every other day and freeser stored in plastic bags during the early pre-combining period in liichigan. The threshing unit was returned to liichigan July 15, after which ssules were collected directly from the field during the norul couining period. The freeser stored saules were later thrashed. It was considered desirable to photograph the threshing action. The eriginal approach was to construct a rotating mirror arranguent which would project the iuges of the grain sqles to cuter mirrors. A high speed camera was to be located over the center mirrors, taking 4000 to 5000 frames per second. Four silvered mirrors were placed in a rotating housing so that the line of sight of the camera was split and moved horisontally outward four inches on each side. The device was bolted to the mounting clan and rotated with it. Two factors forced abandouent of this approach. First, the unit could not be satisfactorily balanced. Second, the fan action of the assembly increased the power requiruants necessary for complete threshing beyond that available with the electric motor and transmission. A set of high speed breaker points were installed on the uin drive shaft and set to open once each revolution of the mounting clau. The points triggered a strobotrac-strobolue arranguent that flashed once each revo- lution. This combination gave satisfactory light for motion pictures at 16 frames per second. Three hundred feet of movie film recorded the threshing action. This photographic technique at best was a couromise arrangement. First, the range of view was only 4 inches of a total threshing range of 23 inches, so that the probability of photographing discharging kernels iuediately becomes only 17 percent. This probability was further reduced if the movie camera shutter was closed at the time of the flash. This occurred at certain speeds. The technique permitted visual determinations of head condition at various speeds and therefore was useful. grain physical characteristics Accurate centrifugal force calculations depended upon kernel weight and kernel radius, in addition to the speed of rotation. It was therefore necessary to determine kernel weights by location within the wheat head. -41- lndividual heads had spikelets removed in order from the apical spikelet. The kernels in each spikelet were individually weighed in grams to four deci- mal place accuracy. The position of the kernel within the spikelet was also recorded. The distance between adjacent spikelets was obtained by dividing the total head length by the number of spikelets. The above determinations were made on both iusture and mature heads to establish differences in kernel moistures within a head. §traw phzsical characteristics The method of obtaining the threshing force depended upon the culm and stu not breaking before the kernels were removed. This fact prompted estab- lishment of straw breaking forces at different stages of uturity and moisture. A Schopper tensile testing uchine, couonly used in the packaging industry, was available for these determinations. Straw specimens six inches in length were prepared from the culm iuediately under the head. These specimens were clamped into the machine and stressed, using the slow speed loading drive. (See Figure 12). Breaking forces were recorded for at least eight specimens at each moisture condition. After fracture, the broken pieces were flattened by using a straight edge and the area of the fractured point obtained with measurements made with micrometer. Static and dynamic coefficients of straw friction were determined prior to the tensile tests. A tilting board arranguent as seen in Figure 13 was available for these tests. The surface material was galvanised metal. The static coefficient of friction was considered to be the angle the surface made with the base when the straw would start to slide from rest. The dy- namic coefficient of friction was recorded as the angle the surface made to -m- Figure 12. Straw tensile strength was determined by use of Schopper testing machine. Figure 13. Straw frictional data were obtained with a tilting board device, surfaced with galvanized metal. - 43 - the base when the straw would continue to slide after being initially accelerated. Straw, chaff and grain proportions of heads were established by threshing and separating by hand heads with seven inches of straw attached. These pro- portions were used to establish percentage of chaff removed during threshing. Field Research Sisailtaneous conventional and centri fuel threshing Seneca wheat was threehed with a conventional rasp bar cylinder and grated concave and with the centrifugal threeher simultaneously two after- noons. A John Deere model 30 codine powered by a Farull 460 diesel tractor was used for the field studies. The combine was conventionally equipped for these tests. Strew feeding rates were maintained practically constant by using first gear speed and a constant depth of cut. A strip of (uniform wheat 62.2 feet long and 300 feet wide was established. ‘When driving with full width of cut, one-hundredth acre test plots were harvested. At the beginning of each test, the combine was cleared. It likewise was cleared at the end of each test plot. The total discharge from.the rack was collected in canvasses (Figure 14). Grain threehed and separated was gathered at the tank. These collections were weighed, samples for moisture taken, and then stored for subsequent evaluations. Twenty tests were conducted at five cylinder speeds and four concave clearances the first afternoon in grain of 14 to 15 percent moisture. Fifteen - uh - Figure 14. Canvasses were used to collect total discharge from the rack during field combine tests. Figure 15. Straw discharged over the rack was analyzed to determine rack and cylinder losses by use of a rethresher. tests with five cylinder speeds and three (concave clearances were conducted in grain 12 to 13 percent moisture the second afternoon. During the time of the field tests, at least six samples of 24 heads uch were centrifugally threehed each day. moisture of combined grain was determined by use of an ‘ electric Steinlite lioisture Teeter.) The straw saules were analysed in a- specially constructed rethresher built by Roman (1943) for his research (Figure 15). The straw passed over a rack designed to ruove any threehed but unseparated grain. Grain thus collected was referred to as rack loss. The straw next entered a double cylinder of spike tooth design which finalised threshing. The grain renewed by this mechanism was called cylinder (or threshing) loss. The collected grain saules were first reeleaned in a Clipper seed cleaner. Test weight determinations were made. Next 100 gram samples were divided several times on a Cuthbert sampler until two lots of approxiutely 150 kernels ruained. Visual kernel damage was determined after which duplicate germination analyses were ude. Dormancy was broken by refriger- ating the samples. After seven days in the germinator, the number of dead and weak sprouts were counted. Baud threehed grain samples were germinated as checks . Conventional threshing and sense of separation The combine was altered by removing the shoe assubly, the fan assubly and the slat conveyor which returned grain separated by the rack to the front of the shoe. A collector housing with two couartments was rigidly attached to the concave (Figure 16). Grain sacks attached to this housing collected ‘ all grain, chaff and short straws separated at the eoncave‘during the threshing -46- process. A wood pan with five compartments (zones) was inserted under the rack and moved forward until it mated the rear cylinder compartment. The pen was removed after each test (Figure 17). This arranguent gave seven separating sones, two at the cylinder, one for the cylinder after beater, and four on the rack. The eighth sone (or the grain going over the rack) was collected in a canvas and analysed as pre- viously indicated. See Figure 18. Twelve tests of 1/100 acre each were conducted with threshing effort the only variable. Five cylinder speeds and three concave clearances were used in 12 percent moisture grain. Seven tests were run with feed rate the only variable. The material collected at the different zones was carefully sacked, marked and stored for subsequent analysis. The stages of the analyses were: (1) Total'weight of collected material was deterudned. (2) The material was subjected to the blower of a Clipper cleaner which removed chaff and light straws. Net weight was again determined. (3) The remaining material was separated by the Clipper cleaner in the conventional manner, removing all foreign materials. (4) One hundred kernel weights were taken to establish sise differences by sones. -m- Figure 16. Housing which was attached to the combine concave to collect grain, chaff and straw separated by the cylinder at the concave Figure 17. Grain and straw passing through the rack was collected by a wooden tray with five zones inserted under the rack. -143- coHuonueom mo coHueooH can wcmcwanouon ecu penance no defiance wo snowmen omunaunom .mH onswmm zo_._. m-—<>-————w /. so if/ so ,1 l .0 1 THRESHING - °/c — — 33.| °/n / KERNEL MOISTURE O 20 ”.3 /c O0 0.|0 0.20 0.30 0.40 0.50 THRESHING FORCE - Lbs. Figure 23. Relationship of threshing force to percent of threshing for Seneca wheat -55- Ioo / so , S I so 2 I <33 I uJ 9:E 40 / I- ] KERNEL MOISTURE / o———-o l|.3°/c / o———-o 33.I°/. 20 i ‘ I o 0 . 50 I00 I50 200 250 CYLINDER PERIPHERAL VELOCITY- Mph Figure 24. Relationship of cylinder peripheral velocity to percent of threshing for Seneca wheat 0.50 Ioo _ / / ’3’ s I so / // ’ / .\° so I ' . I I / (D g I , I! KERNEL MOISTURE-Va $ I I or u 40.2 a: 40 ,l l . 0—'—-0 28.2 I .__.... I ’ 0 0 0.IO 0.20 0.30 0.40 THRESHING FORCE-Lbs. Figure 25. Relationship of threshing force to percent of threshing for Blackhawh wheat I00 80 ..\° 60 (ID I / MOISTURE CONDITIONS — °/. Z I : C Dew (I) ¥ Groin l|.6, Straw 22.2 'i’ 40 I Light rain -—o . E I II 9— Grom l0.8, Straw ll.7 ' _ Heavy rain I 0‘ ‘O Groin l6.|, Straw 37.3 20 1 I 0 0 O.l0 0.20 0.30 0.40 0.50 THRESHING FORCE - Lbs. Figure 26. Relationship of threshing force to percent threshing for three conditions of survace moisture (Genesee wheat) -53- Auuunz coocomv wounmounu ucoouon mm ROM nouasvou oonow mcfinuuunu ou announce Hucnux mo nanncowuuaum .mm unuwwm oxo I 95.5.0.2 ...mzmmx NN ON m. m. o. N. O. m 00.0 Ans-ens .285 «mood + 21.0 ... use“. m... .nv memWI mwfinv IL 0 O n 00 0 RV _ o o o o- mmwo I m m8 0 de 010 -59- Auuoma noncomv manganese uncouon mm Ham mongoose uonom wummnounu cu announce scene we nanncoHuuHum .wN shaman c\c I mmDPQOE 36.um v. N_ O. m m V N O 0 mod 3.535.: 39:9 mNOOd + mm_.o woo-cu KII - S o o < 0 m6 m o o o 0% o o o oo _ O O O O D E o o o oo . z . A... n I. 0.: Ixyllglrmv vmo 0 O O O F 00 o «no 0 owd / Average of 8 tests 0 0 so ° ..\° I 60 G o z 3‘: MOISTURE g Kernel 9-l2 °/. I 40* . Straw 4 % I— O O 20 O o 8 0 0 0.08 0. I6 0.24 0. 32 0.40 THRESHING FORCE - Lbs. Figure 29. Variations existing in the relationship of threshing force to percent threshing (Seneca wheat) -51- Sffect of varietp uppp threshing force It is generally accepted that certain wheat varieties thresh easier than others. At least, certain varieties are subject to more pre-harvest losses through shattering than others. Figure 30 shows a threshing couari- son among five wheat varieties and rye. The CI-l3l70 variety is considered to be an easy threeher because of excessive field shattering tendencies. It show: low forces for initial threshing but relative to the others, it was the most difficult of all to thresh. Blackhawk, a bearded variety of wheat, was not particularly diffi- cult to thresh. Rye, also bearded, was an easy threeher. The threshing differences presentedcould have been caused by the slight moisture varia- tions. Awns did not cause any problem in threshing; with the awns attached, however, the chaff was more difficult to separate from the grain. See Figure 31. Effect of method of force application Regular mounting (heads extuding on radial lines from center and con- strained by holding the straw) required approxiutely twice the force of that with reversed mounting as presented in Figure 32 for high moisture grain. This difference was not as great for low moistures (see Figure 33). With the reversed holding the kernels bent back, opening the glues during the process, and sheared the attachment. This holding would be the best method for minimum threshing force. Tests, conducted with intermediate holding, did not achieve more than 50 percent threshing. Retaining cylinders with 3/8 and 1/2" holes were used - 62 ' I()C) ’ a 3' gv-"o ‘i \ 80 LEGEND Rye I3 °/e H Genesee II °/c 0— —-0 C. I. l3l70 I22 7.. H Blockhowk II.7 % F—0 F“ Thorns l0.3 °/e °—'° Seneca I0.8 °/e @——<9 0) CD 45 C3 THRESHING - °/o 20 0 0.I0 0.20 0.30 0.40 0.50 THRESHING FORCE - Lbs. Figure 30. Effect of grain and variety upon the relationship of threshing force to percent of threshing -53- As threehed After cleaning Figure 31. Relative quantities of a bearded wheat threehed at various speeds of rotation (rpm) -5),- REVERSED Moisture: 5|.3 °/e kernel 43.3 % straw J '00 \ F/fl ///o / so . \’ / / . I (T 50 I \_ . o I REGULAR Z Moisture: 44.8 °/c kernel 3:, I 40.7 °/. straw “J I a: 40 . UK +— I 20 I 0 0.08 0.l6 0.24 0.32 0.40 THRESHING FORCE - Lbs Figure 32. Effect of method of holding upon the relationship of threshing force to percent of threshing for high moisture Genesee wheat .-s- Reversed F f/C—Requlor 80 I I / . ,’/ o\ ‘g’ f $ I “J I g 40 . ._ MOISTURE Grain "’ | L7 0/0 I SNOW ' 3.0 ‘70 20 * ' I I I c) ; O 0.08 O.l6 0.24 0.32 - 0.40 THRESHING FORCE - Lbs Figure 33. Effect of method of holding upon the relationship of threshing force to percent of threshing for dry Seneca wheat -55- with the straw stationary relative to the cylinders. For complete threshing relative motion between the straw and the cylinder must be obtained. It was also observed that visual kernel damage would be a problem if the perforated holes had sharp edges. Figure 34 presents the difference when centrifugal force was applied with and without air resistance. The data shown were obtained simultaneously from the same crop sample. Each datum point on the centrifugal curve represents one head whereas each point on the other curve is the average of 24 heads. The heads which were completely enclosed in a centrifuge cup had to be sub- jected to higher forces for threshing to occur. The air resistance helps to Open the chaff and lessen the threshing forces required. Chaff run“ The amount of chaff rcoved during threshing varied according to crop maturity, moisture of chaff and straw, variety and method of holding. Quan- titative measurmsents of cowarative amounts of chaff r-oved under the various conditions were not obtained, although chaff-grain ratios were cal- culated on the wet basis. This ratio was not satisfactory for cowarative use because chaff moistures were not obtained. Grain threehed in the centrifugal cup was cowletely clean of chaff. See Figure 35. Head appearance after threshing was identical to unthreshed heads under this air resistance-free condition (Figure 36). Results of this nature would coqletely eliminate subsequent separation and cleaning operations. its other “tr-e, where the st-s were coqletely stripped of chaff, was frequently obtained when threshing in the experimental thresher.with a dry, mature crop. The stas on the leading side of clawed group were always -67- K Experimental thresher IOO j, a \ / ° o/ o O 6 30 r’ o ,/ Centrifuge 1 (without air resistance) 3 / I 50 f ‘1' ‘9 o E I l . 3 g 40 .L t— ] ~ MOISTURE: kernel - ll % O 0.08 O.l6 0.24 0.32 0.40 THRESHING FORCE - Lbs Figure 34. Effect of air resistance upon the relationship of threshing force to percent of threshing - 68 - Figure 35. Resultant straw and grain condition after threshing without air resistance Figure 36. The two threehed heads at the bottom appear similar to the unthreshed heads at the top when threehed without air resistance. -59- more free of chaff than those on the trailing side. (Leading side refers to that which would first contact air or other resistance.) Two samples were hand stripped to obtain chaff-grain ratios under com- plete threshing conditions. A eaaple of Genesee taken from the greenhouse and perldtted to air dry to a kernel moisture of 13.4 percent had a chaff- grain ratio of 0.182. A field sample obtained immediately after a rain gave ratios of 0.138 and 0.132 for the'wet and oven dry conditions respec- tively. the grain, chaff and straw moisture contents under the wet condi- tion were 15.5. 35.0 and 21.3 respectively. The chaff-grain ratio varied during threshing with the experimental thrasher from 0.088 to 0.185. In general, a high percentage of chaff remained on the stem when the chaff was high in moisture, regardless of the source. The bearded wheat and rye during threshing lost a smaller percent of the chaff than the other varieties. Reversed holding resulted in more chaff being removed from the stem. Figures 31 and 37 give an indication of the quantities of chaff re- moved at the various speeds. The effect of surface moisture upon the speed at which the chaff was separated is shown in Figures 38, 39 and 40 for dry, dew-laden and wet-by- rain samples of Genesee wheat. All curves are based upon total chaff re- moved and do not indicate coQarative amount of chaff removed under the three conditions. The relative amount of grain threshing in percent is also shown for each condition. ‘ Hoisture. it is noted, reduced thepeak percentages of chaff removed and shifted chaff removal to higher speeds. .Accepting speeds necessary to r-ove 98 percent of the grain would. reduce the chaff loads by substantial percentages. (Note also that the speed at which the greatest amount of grain -70- 3000 3500 4000‘ Before cleaning to remove chaff /000 /5 00 2000 2500 C900 3000 3500 4000‘ After cleaning Figure 37. Total and clean grain threehed at various speeds of rotation (rpm). Genesee wheat Bauum mun Baum no>oamu awaum van «mono mo hufiuamov cu noomm mo mannaoHuaHam .mm shaman Sam I owmam 20.._.<._.Om 000m 000m comm OOON 009 000. 7LT- . \ / \ _ / r \ ON :26 \\ zwill \ m / \ m / \ f. / o z ow % 31.0 2:: £96 rtoco . nu 3E5 Ea 58¢ w . .0 oo m Du Cu Cr A H” Om C 00. -72- 3nuum cooaarzon now oo>oaou afiouw nan «menu «a huaucosv on woman «a nanmco«uuaom .mm cam .. ommam 20:32. ooov com... 000m 008 080 is n7; / . om recoilx/ / \ ,ix 0. 21.0 0:2 53.55 345m 283-50 cm £80 8 00. aunmam CHAFF REMOVED - °/o of total -73- 393m nos oum coerce-o... anon—w nan amaze mo .3353; 3 woman no 3:23.333“ .00 93me eamrommam zoEPom 08¢ 89.. 000m 008 88 com. 08. o e/ x / /M.\ a / \\ 8 .m o... .x. . _ med 0:9 52335 E 2,qu his 520 \x W . M om W. F F A H C 8 oo. -74- was threehed was increased by the moisture. main- speed for coqlete threshing, howaver, was not nterially influenced by the dew.) gerael amuse by size table 1 shows the average kernel weights of grain threehed and tuned at the various speeds of rotation in the experimental thrasher and the com- mercial centrifuge. the last to be thrashed kernels were 21 to 28 percent lighter than these r-oved in the middle speed ranges. “there was- probably little signi- ficance in weight between those rnoved at the lower speeds and those r-oved at the middle speeds. send germination the percent germination of Seneca wheat thrashed centrifugally. and by hand under various moisture conditions is shown in Table 2. The hand threehed sales were air dried in the head until threehed. At kernel moisture above 36 percent, there was definite evidence of kernel deformation, since the hand thrashed samples were mach higher in germination. The highest percent of germination was obtained for the hand thrashed grain at these moistures, ranging 93 to 98 percent. The germina- tion for the centrifugally threehed samples varied from 2 to 86 percent with most eagles under 50 percent. A softer coating on the outer housing of the centrifugal threeher would be required at these moistures. The germination of the centrifugally threehed grain removed at the lower speeds was consistmtly higher than the check-hand threehed sample. It was frequently lower at the higher speeds, however, indicating that internal kernel daaage can readily occur. I The drier grain did not experience - 75 - Table 1. Relationship between cylinder speed and average weight of kernels rnoved when threehed by «perimental thrasher and centrifuge Experimental thrasher Speed of rotation Winter stored Hazin- Field picked Kari-am up to Genesee Weight Genesee Weight rpml grama z. graaa 2 1000 .048 96 .041 98 1500 .050 100 .042 100 2000 .049 98 .041 98 2500 .049 98 .041 98 3000 .045 90 .037 88 3500 .030 72 4000 .038 76 unthreshed none none kernels Co-ercial centrifuge Speed of rotation Winter stored m.- up to Genesee Weight rpm grams 2 1650 .049 93 2000 .053 100 2400 .053 100 2850 .048 90 unthreshed .042 79 kernels - 75 - Table 2. Garaination of Seneca wheat when thrashed by different methods and at various kernel moistures Centrifugally thrashed Kernel Rand rpm of threshing Moisture Ihreshed 1500 2000 2500 3000 3500 Percent Percent Percent 39.4 93 2 54 39.0 96 _ 47 49 38.6 98 21 44 38.1 96 65 32 36.4 95 86 2 33.1 77 63 61 23.0 76 92 82 20.2 83 7 88 19.4 68 73 60 19.0 70 96 87 17.3 71 85 92 17.2 78 83 80 16.7 89 99 94 15.5 63 96 82 14.8 62‘ 94 90 14.6 90 96 71 14.6 73 94 62 14.5 96 71 14.4 93 87 13.8 71 . 93 43 13.7 85 99 82 13.4 89 100 91 13.2 76 97 60 12.2 87 98 85 12.2 76 93 88 12.1 89 100 84 12.1 76 94 86 11.8 83 90 59 11.8 98 93 11.6 88 100 89 11.4 100 99 11.3 90 99 84 11.2 98 68 11.1 69 ' 90 70 11.0 60 69 87 11.0 89 93 96 10.9 74 88 60 10.8 96 98 90 10.7 93 99 82 10.5 73 82 11.4 87 89 82 10.2 ’ 82 98 71 9.6 95 97 82 a severe germination loss, however. The superior germination of the centrifugally threehed grain at the lower speeds over the hand threehed samples could be caused by kernel selec- tion in harvesting. The healthier, better kernels (as measured by the germination criterion) were perhaps rnoved first. The extent to which kernel selection affected germination cannot be pinpointed from this study, although the fact that the check germination generally falls between the higher and lowar values of the centrifugally threehed wheat strongly suggests kernel selection. Grain thrashed centrifugally had better germination than combine har- vested grain as indicated in Table 3. The maxi-Ia germination obtained from cutrifugal threshing was 98 percent coQared to 91 percent for the combine. Table 3. Generative germination of Seneca wheat when thrashed by cedine, centrifugal thrasher and hand Centri fugally threehed Kernel Band combine rpm of threshing moisture thrashed thrashed 1000 1500 2000 2500 Percent Percent Percent Percent 11.3 96 11.3 80 98 97 10.0 91 98 98 9.2 96 96 11.4 87 70 89 , 82 10.2 82 to 98 71 9.6 95 85 97 82 -73- gloratory threshing of corn Figure 41 presents the forces required to thresh high moisture wheat and 17 percent corn. The corn was placed so that the kernels had to bend through an angle of 90°. The kernels broke clean, apparently using the cob as a partial fulcrum. Although the force required for corn threshing was mch greater than that required for wheat, the drum speeds required were similar. This can be explained by the fact that individual corn kernels weigh approximately four times as much as wheat kernels. There was evidence of corn kernel damage at the higher speeds, indi- cating that a thicker padding would be required on the housing. Occasionally the cob would shear from the restraining bolt before shelling was complete. Physical Characteristics of Grain Kernel weight analysis Kernel weight-frequency histograms for five wheat varieties and rye are presented in Figure 42. Rye approaches a normal distribution curve. All the wheat varieties are skewed heavily to the larger kernel side of the histogram. A complete grouping by weight for a 250 kernel random sample of Genesee wheat is presented in Table 4. The percent of total weight is also shown in this table. The range in kernel weight (0.039 grams) exceeds the average kernel weight . -79- QN bawmow «Macao auoo nan 33:3 0.25308 swan snows”. cu confines.» among a>3unonfioo .Hq 0.3me an... .... women. ozfmmmr... Wm QN 0.. N._ md ad 0 A goo o\o 0N. 38%. oxo m.m. 9.3306 3me oxo t 2230:. 8on o\o mm 2100 EMIBN 0 ON on 0m 0m 00. THRESHING — °/. 30 20 IO 30 20 IO NUMBER OF KERNELS - PERCENT OF TOTAL C) -80- Rye —. 0* 0:43:70 \ \ l l IA l Win. l l Thorne MA / I *1 Blackhawk fl \ \ A ‘0 U) 30 20 Seneca ) \ l0 / o J so I l l 20 l '0 Genesee \P O' l J 8 0 to O In 8 In 0 IO ,_ 1D 52 C? QJ ”3 N) . ‘r U) “D 07 S 9 - .o -'- «a 4 do i g N N r0 r0 V a- In KERNEL WEIGHT CLASS-Thousandths of a gram Figure 42. Kernel weight-frequency histOgrams for five wheat varieties and rye - 31 - Table 4. Weight frequency statistics for random eagle of Genesee wheat Frequency Weight of Total weight (ti-native Class Occurrence in class total grams Percent Percent .053 1 .56 .56 .050 2 1.07 1.63 .049 2 1.04 2.68 .048 4 2.05 4.72 .047 2 1.00 5.72 .046 16 7.85 13.6 .045 10 4.80 18.4 .044 13 6.10 24.5 .043 11 5.04 29.5 .042 19 8.51 38.0 .041 18 7.87 45.9 .040 15 6.40 52.3 .039 13 5.40 '57.7 .038 13 5.27 62.9 .037 10 3.94 66.9 .036 15 5.76 72.7 .035 12 4.48 77.1 .034 15 5.44 82.6 .033 9 3.17 85.6 .032 6 2.05 87.8 .031 10 3.30 91.1 .030 3 .96 92.0 .029 3 .93 93.0 .028 4 1.19 94.2 .027 3 .86 95.0 .026 5 1.39 96.4 .025 3 .80 97.2 .024 4 1.02 98.2 .022 l .23 98.5 .021 1 .22 98.7 .020 1 .21 98.9 .019 2 .41 99.3 .018 l .19 99.5 .015 2 .32 ~ 99.8 .014 l .15 100.0 Total 250 100.0 Average kernel weight 0.0375 grams Median‘kernel weight 0.036 grams .32. Kernel weight by location in the head Ten Genesee wheat heads with 347 total kernels were analysed by weighing each kernel and recording its position from the apical kernel. The kernel position within the spikelet was also recorded. Results are presented in Tables 5 and 6 and Figure 43. The minimum number of spikelets on any head analysed was 13. Reads having more spikelets had the additional spikelets averaged in rows 5 through 9. The center spikelets of a wheat head contained the heaviest kernels. Within any spikelet where more than 2 kernels had grown, the outside kernels were heavier than the inside kernels. Earnel moisture variations within a wheat head A kernel moisture by spikelet-position analysis was made for 3 heads of i-ature Seneca wheat. These results are shown in Table 7. Except for the apical kernels which were driest, relatively minor moisture variations existed within any head. Straw Physical Properties The probl- of maintaining constant straw moistures comlicated straw physical properties determinations. Straw moisture changes were very rapid when extr-e moisture gradients existed. It would appear that straw deter- minations should be nde in controlled atmosphere rooms. The results re- ported here, therefore, mat be considered as exploratory in nature. The results presented in Table 8 show values obtained under generally changing straw moisture conditions. These conditions are probably descrip- tive of the ranges a th’resher would experience under field operation. . g3 - Table 5. Weight-frequency distribution by spikelet location on head for Genesee wheat Spikelst fnma apical Under .016- .021- .026- .031- .036- .041- .046- .051- Over spikelet .015 .020 .025 .030 .035 .040 .045 .050 .055 .056 Halber of kernels of each weight class 1 2 2 3 1 2 1 1 4 7 2 1 3 1 3 7 6 1 4 7 8' 4 5 1 5 12 12 4 6 1 2 2 2 7 10 9 2 7 3 1 4 6 10 5 1 8 1 1 4 3 ll 10 6 l 9 1 2 3 9 l9 9 8 2 10 2 3 2 l3 6 2 11 1 3 5 6 8 3 2 12 l 1 1 2 l 14 4 2 13 1 l 3 4 5 2 Table 6. Relationship of kernel position within spikelet to average and extreme weights of Genesee wheat Spikelet . Average from Kernel position within spikelet of all Extremes apical within Maximum Minimum spikelet Left Middle Right spikelet weight weight average weight - grams grams grams grams 1 - .0317 .0317 .0430 .0181 2 .0380 none .0346 .0363 .0482 .0245 3 .0385 " .0374 .0379 .0456 .0196 4 .0414 " .0404 .0410 .0494 .0352 5 .0439 .0240 .0456 .0441 .0524 .0350 6 .0476 .0316 .0481 .0446 .0560 .0244 7 .0466 .0326 .0462 .0432 .0565 .0216 8 .0454 .0339 .0480 .0428 .0553 .0105 9 .0445 .0370 .0483 .0433 .0577 .0216 10 .0427 .0366 .0443 .0419 .0542 .0273 11 .0438 .0329 .0386 .0386 .0521 .0236 12 .0375 .0298 .0387 .0359 .0475 .0146 13 .0358 .0284 .0368 .0333 .0435 .0147 Commits Average .0409 grams - 8h - amass somaaou ham unwwus Haauox no one; one no coauauon Hoauax mo manchHuaaom .ma unawam ...mquiw 1.4054 201“. ...w..wx.am m. __ m N m m _ ON 22.9. .622 o w o \ mm av «3on 3.330.. _ mm. AVERAGE KERNEL WEIGHT-Thousandths of a gram - g5 - Table 7. Kernel moisture by spikelet location for three heads of Seneca wheat Spikelet from apical spikelet Read 1 Read 2 Read 3 1 21.2 34.3 40.2 2 28.9 34.1 3 28.2 38.1 42.2 4 18.6 45.4 39.0 5 30.5 43.7 40.9 6 34.1 43.0 43.9 7 33.6 42.4 46.3 8 36.2 46.5 43.8 9 34.5 43.9 43.2 10 34.7 43.0 41.9 11 36.4 43.6 43.0 12 35.7 43.7 13 37.7 43.1 14 36.6 45.2 15 43.5 16 43.7 17 44.7 -86- Table 8. Physical characteristics of Genesee wheat straw under various conditions Coefficient Average of friction Sqle description Straw breaking Tensile moisture force stress Dynamic Static parent pounds pounds] sq. in. high moisture grain, straw air dried for 12 hours 11.9 13. 5.704 .32 .54 high moisture grain, freeser stored 13.8 12.3 10,650 .34 .56 suture grain, light rain 14.1 20.1 16,200 .34 .57 llature grain ova dried, straw picked up moisture from high huidity 10.1 13.2 9,170 .34 .54 Presser stored, stru very dry because of hole in each 3.5 17.1 14,630 .39 .65 Field collected eagle during heavy rain 38.0 11.0 7,890 .44 .77 Field seqle - dry 9.7 23.0 16,800 - - - - a“ - but. 41.0 90‘ 2.610 - " - - -87.- ggefficients of friction Table 8 is arranged in order of increasing dye-ic coefficients. The dynamic coefficient rang“ {to- 0.20 to 0.33 less than the static coefficient. The coefficients increase generally with decreasing straw moisture, although surface moisture reverses the relationship. The total range in dynamic coefficients for straw free of surface moisture was 0.07. Breaking force and tensile stress Righ moisture, i-ature grain straw was much more easily broken than dry straw. Excessive surface moisture also reduced the breaking force. The tensile stress followed the same relationship. If the kernel attachment follows the same relationship as straw, there would be reason to assume that threshing might be easier under certain higher straw moisture conditions. Field Research Results The si-arised data from the combine threshing tests are presented in Tables 19, 20 and 21 (Appendix). Thirty-five combine tests were run con- current with centrifugal threshing. tighteen additional tests were con- ducted to establish the quantity of grain separated at the cylinder. gylinder adjustment and threshing loss The percentages of unthreshed grain were plotted corresponding to the conditions of cylinder adjustment. Lines of constant threshing loss (called threshing loss contours) were then drawn (Figure 44). The threshing loss contours indicated reduced threshing losses as cylinder aggressiveness was increased either by greater cylinder speed or through reduced clearance. .33. The effects of cylinder adjustment upon the percent of unthreshed grain and the percent of separation (rack) loss are presented in Tables 9 and 10. An analysis of variance of the data indicated that neither cylinder speed nor clearance gave significant results at the 95 percent level (Table 22, Appendix). The F values for significance were 3.88 and 3.48 for cylinder clearance and speed respectively whereas the calculated values were 3.75 and 3.19. glinder adjustment and smration (rack) loss The results suggested a relationship existed between cylinder adjust- ment and separation (rack) losses (Table 9). A scatter diagram of separa- tion losses plotted against cylinder peripheral velocity is presented in Figure 45. From the practical standpoint, all separation losses were less than 40 pounds per acre, an amount generally considered acceptable. The maxi-1m loss occurred at the lowest and highest cylinder velocities (3200 and 6300 fpm respectively). The loss at the velocity extrnes was nearly twice that occurring at 4700 fpm. The rack loss varied only slightly as cylinder clearance was varied from 3/16 to 7/16 inches. Apparently, the lower cylinder velocities do not completely free the kernels from the straw, although the kernels can be shaken free. At the higher velocities, greater straw breakage decreases separation efficiency. gylinder adjustment and visual kernel damageI germination and test weight The effect of cylinder adjustment upon kernel dange, germination and test weight is presmited in Table 11. The analysis of variance is presented in Table 22 of the Appendix. ~89- GD 3 4 5 6 7 8 CYLINDER CLEARANCE- I6ths of an inch \ \§\\ 7 THRESHING LOSS-°/c C g I/2 I 2 3 ~>= / “6 {’5 / / 6 ,5, / / / 4 :3 O .C ’— ; / / t: 0 5 3 7 / L; .1 5 4 / .5 / / I / O. E / m a a: m o z '3 >- o Figure 44. Relationship of cylinder adjustment to threshing loss for a rasp bar cylinder in dry Seneca wheat -9b- Table 9. Rffect of cylinder adjustment upon threshing and separation losses Clearance Cylinder speed Threshing loss Separation loss inches fpm percent percent 3/16 3100 3.49 .94 3900 1.79 .81 4700 .54 .59 5500 .42 .70 6300 .13 1.02 5/16 3100 4.98 1.10 3900 3.34 .95 4700 2.40 .55 5500 .93 .93 6300 .69 1.30 7/16 3100 8.59 1.47 3900 4.63 .95 4700 3.00 .42 5500 3.36 1.43 6300 3.00 .73 Table 10. Average effects of cylinder adjustment upon threshing and separation losses Mean threshing Mean separation Clearance loss loss inches percent percent 3/16 1.27 .81 5/16 2.47 .97 7/16 4.52 1.00 Speed fpm 3100 5.69 1.17 3900 3.29 .90 4700 1.98 .52 5500 1.57 1.02 6300 1.27 1.02 CYLINDER CLEARANCE- I6ths of an inch 0 0 O O O 3 4 5'6'7 50 T is C) ./ no (3 SEPARATION LOSS - Lbs/acre 5 . . age a .:°O.@@ 0 O 3000 4000 5000 6000 7000 CYLINDER PERIPHERAL VELOCITY - Ft/min Figure 45. Relationship between cylinder adjustment and separation (rack) loss for dry Seneca wheat -92- Table 11. Iffect of cylinder adjustment upon kernel damage, germination and test weight Cylinder Cylinder peripheral Garni- Kernel clearance velocity nation Test weight damage inches fpm percent pounds/bushel percent 3/16 3100 -- 61.0 1.3 3900 77 61.2 .6 4700 73 60.8 3.1 5500 80 61.1 4.8 6300 70 60.5 3.1 5/16 ‘ 3100 78 60.9 .6 3900 75 61.0 1.8 4700 -- 60.5 2.0 5500 75 60.5 2.3 6300 75 60.1 4.3 7/16 3100 85 60.7 0 3900 85 60.9 1.3 4700 78 60.8 1.4 5500 85 60.6 1.3 6300 78 60.8 4.1 Figure 46 was prepared by’plotting visual kernel damage versus cylinder adjustment and then connecting points of equal danags. The contours and the statistical analysis suggested that kernel damage is principally dependent upon cylinder speed. ‘ This result has been reported for corn by Pickard (1955). The statistical analysis suggested, howaver, that cylinder elearanee had a significant effect upon germination at the 95 percent level whereas cylin- der speed was not significant. The germination was consistently low for all cylinder speeds and clearances, a fact which my have asked true effects. Increased visual damage with higher cylinder speeds is an anticipated result, since kinetic energy imparted to the kernels is proportional to the square of the cylinder speed. Likewise, the kinetic energy is not directly related, if at all, to cylinder clearance. The germination results, however. -93- CYLINDER PERIPHERAL VELOCITY - Ft/min 7000 I 1 VISUAL KERNEL DAM/3:5 ——4ee eooo . 334 5000 ‘- 4000 x 2 7°" 3000 3 .4 5 e '7 s CYLINDER CLEARANCE - l6ths of an inch Figure 46. Relationship of cylinder adjustment to visual kernel damage for dry Seneca wheat -94- would not be anticipated. since a correlation would be anticipated between kernel visual damage and reduction in germination, and those factors causing kernel da-ge would be expected to cause germination d-age. Test weights of grain thrashed at the various conditions of cylinder adjustment varied a little over 1 pound per bushel. The reduction appeared to be independent of cylinder adjustment. gylinder adjustment and gr_a_in smgtion gt the sylinder The amount of grain separated at the cylinder in percent of total grain is nuerically presented in Table 12. Average effects of cylinder velocity and clearance is presented in Table 13. Figure 47 presents the same date graphically. The total grain separated at the cylinder increased with more aggressive cylinder adjustment. increasing the cylinder velocity proved to increase the quantity separated at the cylinder with statistical significance at the 99 percent level (Table 22 in Appendix). Concave adjustments proved to give inconsistent results, although at cylinder velocities above 4800 fpm, the smaller clearance gave better sqaration. This result is in agre-ent with work by Johnson (1953). The range of grain separation at the cylinder was 60 to 80 percmit. From 30 to 45 percent of this was separated in the first part of the cylinder (sons 1). This fact suggests that a substantial part of the threshing occurs during initial acceleration. gylinder adjustment and location of gain aggration over the rack The effect of cylinder adjustment upon the separation pattern at the rack is shown in Figure 48 for four different cylinder adjustments. The adjustments shown permit coqarisons caused by the extra» in cylinder - 95 - Table 12. Amount of grain separation at the cylinder at various cylinder adjust-ants - Grain separatien Cylinder Total Total Cylinder peripheral concave Zone 1 Zone 1 velocity clearance Zone 1 Zone 2 Zone 3 and 2 2 and 3 than inches percent percent percent percent percent 3100 7/16 30.0 20.6 15.3 50.6 65.9 5/16 30.6 26.3 6.3 56.9 63.2 3/16 31.4 22.1 5.3 53.5 58.8 3900 7/16 31.4 29.3 7.7 60.7 68.4 5/16 39.7 35. 3.0 75.3 78.3 3/16 40.0 28 6.2 68.6 74.8 4700 5/16 40.3 28 4.2 68.9 73.1 3/16 43.9 27 2.8 71.2 74.0 5500 5/16 41.1 29 3.4 70.3 73.7 3/16 46.3 30 2.2 76.4 78.6 6300 5/16 44.7 30 5 2.7 75.2 77.9 3/16 47.3 32 4 1.5 79.7 81.2 Table 13. Avarags percentages of grain separated at zones 1 and 2 for all cylinder velocities and clearances 6300 Cylinder to Cylinder Average concave peripheral separation clearance velocity at cylinder inches fpmi percent 7/16 ' 55.6 5/16 69.3 3/16 69.9 3100 55.2 3900 72.0 4700 70.0 5500 73.3 77.4 TZONE 3 I ZONE 2 I I I CYLINDER CLEARANCE - l6ths of an inch 3 3 5 E — V/UV.ll/Ol/Ul/U/Jl/U//fl/Ufl/ 7 /U////0/yfi/. )l/fl/U/Jfi/r _ 3 m rMO/../jf/U//U/JV/U//U/j//y JMU/xf/U/yn/VI/f/U//U/y/ 5 § 3 E //////// /////// i :JNNM, jh/vn/JOK/U//U/Mm//U/ A/U/Vn/Ja/y/le/o//U/lr vC//U//U//Ofl/70/yh//U/ 7 EM LV// /////// 5 glr/I/l/I/I/l/ 7 V5 IOO nu 00 Av nu AU AU Ru Aw 0c o\c l mw023>o ._.< ZO_._.