ABSTRACT TRACTION ASSIST FOR A TWO WHEELED PADDY TRACTOR By S. Gamunu Ilangantileke Traction problems associated with flooded rice soils have been a major limitation to the adaptation of mechanization in rice producing Asian Countries. Sinkage and loss of traction in agricultural vehicles has been a topic of extensive research in the past and will be in the future. The objective of this study was to develop an effective traction aid which would overcome the difficulty of trafficability in saturated soils. A traction aid, working on the principle of a cable and winch system was developed. The winch system was attached to the front end of the two wheel paddy tractor and was powered by a drive mechanism connected to the PTO shaft of the tractor. A Capstan drum was attached to the winch system. A rope with one of its ends attached to an anchor outside the field, was wrapped around the Capstan. The free end of the rope was passed through a S. Gamunu Ilangantileke shieve arrangement, to help maintain a tension on the rope leaving the Capstan drum. When the Capstan was rotated by means of the drive mechanism connected to the PTO, the tractor pulled itself on the rope and moved forwards. The forward speed of the tractor and speed at which the tractor pulled itself on the rope was matched, to prevent slack on the rope if the rope speed was too slow or dragging of the tractor if the rope speed was too high. Field tests with the winch system revealed positive results. The tractor was able to travel through a saturated rice field at a speed almost equal to that at which the tractor traveled on a concrete floor. Without the winch system the tractor would not move through the same rice field; but had excessive wheel slipage which caused the tractor to sink into the saturated soil. The significant advantage of the winch system is that the traction aid is independant of the soil condition and therefore can be used with any soil type. Approved??Z.% genuuu (Major Professor) @AW Approved” 00.000000000000- (Department Chairman) TRACTION ASSIST FOR A TWO WHEELED PADDY TRACTOR by S. Gemunu Ilangantileke A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Agricultural Engineering 1975 Dedicated to My Late Parents ii ACKNOWLEDGMENTS I gratefully acknowledge the support of many individuals and organizations who contributed to this study and particularly wish to express my appreciation to: Dr. Merle L. Esmay, my major professor, for his expert guidance, unfailing courtesy, helpful suggestions and criticisms throughout the course of this work. Dr. Robert H. Wilkinson, my thesis advisor, for his continuous support, guidance and interest in setting up and conducting the study and preparing the thesis. The Food and Agricultural Organization of the United Nations for their generous financial support for this study as well as my entire training in the USA. The University of Sri Lanka and the United Nations Development Program for making my studies in the USA a possibility. Mr. Cohen Sichinga, a fellow student for his untiring support during field experimentation and the staff of the Agricultural Engineering Machine Shop for their valuable assistance. Finally my wife Nirmali, my gratitude for her patience, perseverence in typing a continually changing manuscript and making life pleasent no matter what the circumstances were. iii TABLE OF CONTENTS Page LIST OF TABLES O O O O O O O O O O O V LIST OF FIGURES O O O O O O O I O O 0 Vi Chapter I. INTRODUCTION . . . . . . . . . 1 1.1 Rice Cultivation in Sri Lanka . . 1 1.2 The PrOblem o o o o o o o o 3 1.3 The Objectives . . . . . . . 3 II. LITERATURE REVIEW . . . . . . . 5 III. METHODOLOGY . . . . . . . . . 16 301 The SeleCted ApprOaCh o o o o 16 3.2 Construction of the Winch’ . . 16 3. 3 Construction of the Rice Paddy . 25 3. [4’ Fleld TeS-tlng o o o o o o o 27 3-. Concrete 0 o o o o o o 28 be Firm SOil o o o o o o o 28 C. Saturated Soil . . . . . 28 d. Saturated Soil with the Winch. 29 IV. RESULTS AND DISCUSSION . . . . . 35 “'01 Presentation Of Data 0 o o o o 35 4.2 Efficiency of Forward Travel . . 48 4.3 Analysis of the Winch System . . 54 4.4 Application of the System . . . 59 v. CONCLUSION . . . . . . . . . 62 VI. RECOMENDATIONS FOR FURTHER STUDY . . 63 REFERENCES 0 O O O O O O O O O O C 64 iv LIST OF TABLES Page Travel Speeds in Relation to Engine and PTO rpm for Different Gears . . . . . . 18 Winch Speed and PTO/Winch Ratio in Rela- tion to Rope Speed and Engine rpm . . . . 19 Mechanical Composition of the Soil. Sandyloam (USDA Classification) . . . . . 36 Average Travel Speeds on Different Surface Conditions for Varying Engine Speeds and Gear Ratios . . . . . . . . 37 Pull Generated by the Winch for Different Travel Speeds in Saturated Soil . . . . . 45 Percent Loss in Travel Speed for the Different Test Conditions . . . . . . . 48 Efficiency of Different Test Conditions in Relation to 100% Efficiency on Concrete 0 o o o o I o o o o o 0 [+9 Figure 3.1 3.2 3-3 3.4 3-5 3.6 LIST OF FIGURES A Sketch of the Winch Drum Constructed in the Shop 0 0 a o o o o o o A View of the Braces and Frames used to Support the Gear Box, Extended PTO Shaft and all other Accessories . . A Closer Look at the Winch Assembly showing the Change in Direction of the Rope by Using the Pulley Arrangement The Rice Paddy Constructed on the Soil Science Research Field at Michigan State univerSity o o o o a o 0 Operating the Tractor on Firm Soil Conditions with the Rotovator . . . The Tractor Bogged Down in the Satura- ted Soil, without any Further Movement The Rope is Attached to the Pickup Serving as a Anchor Located Outside the Field. The Picture Illustrates the Tractor Being Pulled Through the Saturated Soil by the Winch and Rope A Sketch Showing the Method Used to Reverse the Direction of the Rope Leaving the Winch Assembly . . . . Forward Speeds for Different Gears at 950 rpm Engine Speed, Under Varying Surface Conditions . . . . . vi Page 21 24 25 27 29 3O 3O 32 38 Figure 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 The Entire Winch System was Sunk in the Mud when the Winch was not Used to Move the Tractor in Saturated Soil . . . . Forward Speeds for Different Gears at 1200 rpm Engine Speed, Under Varying Surface Conditions . . . . . . . Forward Speeds for Different Gears at 1500 rpm Engine Speed Under Varying Surface Conditions . . . . . . . Pull Generated by the Winch for Diffe- rent Travel Speeds in Saturated Soil . . The Front End of the Tractor was Lifted when the Winch System was Used . . . . Loss in Forward Travel Speed Taking Zero Loss on Concrete. The Tractor is Operated at 950 rpm Engine Speed for Varying Soil ConditiOnS o o o o o c o o o 0 Percentage Loss in Forward Travel Speed Taking Zero Loss on Concrete. The Tractor is Operated at 1200 rpm Engine Speed for Varying Soil Conditions . . . Percentage Loss in Forward Travel Speed Taking Zero Loss on Concrete. The Tractor is Operated at 1500 rpm Engine Speed for Varying Soil Conditions . . . Efficiency in Forward Travel for Varying Forward Speeds. The Speed on Concrete is Taken as 100% Effecient . . . . . . Schematic for the Proposed Application Of the WinCh syStem o o o o o o 0 vii Page 40 41 44 46 47 5O 51 52 53 6O I - INTRODUCTION 1.1 Rice Cultivation in Sri Lanka Rice is the most important food staple in many South East Asian Countries, of which Sri Lanka is one. To-date a major portion of the country's food requirements are imported, causing a heavy drain on its foreign exchange resources. Therefore there is an urgent need to increase production by utilization of all available resources to a maximum. Agricultural production in Sri Lanka can be broadly catagorized into dry-zone agriculture and wet-zone agriculture. The dry-zone agriculture is characterized by large areas of cultivable land. The average annual rainfall is 60 inches and the monthly rainfall distribution follows a distinct bi- modal pattern. About 70% of the total precipitation falls during the North-East monsoonal period (October-January) and the balance during the months of April and May. A short dry spell occurs during February and March, but a long and most pronounced dry period is observed from June to September. At this time of the year the temperature is high, winds are highand the relative humidity low. This results in a high rate of surface evaporation and extremely dry conditions. This region of the Island is therefore appropriately termed the dry-zone. Approximately 60% of the paddy lands in the 1 2 country with average acreages of 5-10 acres or larger are to be found in these areas. The dry-zone cultivation to-date is mainly rain fed with limited supplementary irrigation facilities. The field sizes are fairly large which enable medium sized tractors to operate. The soil and water condi- tions of these lands permit the use of tillage machinery with- out excessive sinkage and traction problems. The wet-zone on the other hand is characterized by a continuous rain fall pattern. And the land sizes are consi- derably smaller than those found in the dry-zone. The wet- zone could be divided into the wet highland zone, humid up- land zone and the South Western coastal regions of the Island. The coastal belt has problems of water logging due to a high water table. The cultivation is essentially rainfed, and in certain portions, the rate of precipitation is extre- amly high, averaging well over 100 inches annually (Arumugam, 1969). Most paddy fields in the highland regions are terraced and therefore the average size of such fields are smaller, in comparison with those of the dry-zone. Small two wheel walking tractors are frequently used on wet-zone fields, since the use of larger, heavy tractors is limited or practically impossible. The power tillers varying from 4—12 hp. are widely used in Asia for wet soils. Smaller two wheel tractors and equipment are becoming popu— lar due to their success in smaller paddies (Reynaldo M. Lantin & Roberto C. Bantista). The size and inaccessibility of the rice fields as well as their very soft soil nature, limits the use of larger four wheel tractors. About 30% 3 of the total area of rice cultivated in Sri Lanka belongs to the wet—zone cultivation. 1.2 The Problem The main problem in mechanizing paddy cultivation is the development of a suitable traction device for operation in saturated soils (Ratnatunga, 1969). A very low, soft- soil (especially wet-zone) trafficability in the flooded rice fields, has resulted in excessive bogging (sinkage) of till- age machinery. A considerably amount of labor, time and energy is lost in attempting to cultivate in soft soils, as well as the extra time necessary to remove sunken machinery from these fields. Timeliness of tillage operations is a most important consideration in the mechanization of rice in these high precipitation areas. Timeliness and quality land preperation can greatly influence the growth of rice. Poor and untimely land preperation is conducive to serious weed problems and plant exposure to harmful chemical substances (Ponnamperuma, 1967). A loss of a day or two in tillage operations may cause postponment of sowing and other cultivation operations for a week or two. The drudgery involved, as well as the inefficient use of tillage machinery in soft boggy fields have led farmers to either under utilize or completely abandon the land. 1.3 The Objectives The objectives of this project was to find a suita- ble traction device, that would provide efficient movement u of tillage machinery in highly saturated rice soils. This would permit tillage operations to be performed at the optimum time with greater efficiency while at the same time utilizing labor, time and energy inputs to a maximum. By improving the efficiency of tillage operations in these flooded soils, a considerable increase in production as well as utilization of abandoned paddy lands, could bring about a considerable increase in the rice output of the country. Specific objectives of the project were: 1. To design and construct a suitable traction aid, for a two wheeled tractor. 2. To test the principle of the traction aid with regards to its efficiency and trafficability in the flooded rice field, as against the tractor without such a device. 3. To analyze the findings and provide recommendate ions, for its implementation and introduction. II - LITERATURE REVIEW Traction problems associated with flooded rice soils have been a major limitation to the adaptation of Mechaniza- tion in rice producing Asian countries. Sinkage of agricul- tural machinery has been a topic of intensive research in the past as well as in the present. The objective is to develop an effective traction aid which will overcome the difficulty of trafficability in saturated soils. Allen and Hayes (1953) while investigating the mech- anical cultivation of wet paddy in Malaya showed that manoeuvrability of implements is extremely difficult when cultivating heavy land overlaid with perhaps two or three inches of water. Grist (1965) indicated that in many rice producing countries most of the best land suitable for rice cultivation and future development, may depend almost entirely on the reclamation of swamps, silts, silty soils and peat lands which have little support for wheel or track equipment. Despite the realization that development of "bottomless" land must make use of floatation methods, little progress has been made in devising a suitable means. "Sight of a tractor bogged down in a flooded field is spectacular. This problem must be overcome if tractors 5 6 are to be practical and widely used in flooded fields" Stout (1966). He indicated that the ability of a tractor to pull an implement under adverse conditions existing in wet paddies, is a subject of prime importance. Johnson (1971) showed that the importance of mobili- ty in rice fields, especially in land preperation, harves- ting and hauling of harvested grain, is because, these operations require most of the power needed in rice production. In published reports on the conference of Rice Research and Training in the 1970's (IRRI 1969), it was recognized that in the next decade, the engineers of the Institute should concentrate their research on developing complete designs for simple power operated equipment for rice mechanization. The problem to be faced pertained to designs for both, large and medium sized tractors for high traction in wet fields and mobility under wet low-land conditions. Gee-Clough and Chancellor (1974) showed that, extre- mely unfavorable conditions prevailed for vehicle traction and mobility in saturated land preperation. The problems prevalent in different Asian Countries have effected the scale and type of technology development. "It is therefore necessary to device new or adopt existing machines to suit the conditions of each type of soil". Grist (1965). Numerous traction aides have been developed since mechanical rice cultivation was started. Many contributions have been made by the International Rice Research Institute in the Phillipines. Half-track machines have been developed and operated successfully in some wet soil conditions (1955, Annual Rep— ort of the Gambian Rice Farm). Track layers with wide plates or swamp blocks have been successful on bottomless mineral soils, Allen and Hayes (1953). Although mobility is increa- sed, the cost is high. Track laying combines in California, USA have a high initial cost and their maintainance costs are above those for wheel vehicles, particularly in wet, abrasive soils. Track laying machines usually have a very low clearence and are more difficult to extricate when bogged. They are also limited in so far as the mounting and contro- lling of implements. Therefore track layers cannot be satis— factorily adapted for wet paddy cultivation (Stout 1966). Mayne (1956) observed that cage extentions beyond the standard pneumatic tires increased stability and floa- tation. The extentions were about 12 inches wide and sligh- tly less in diameter than the tires, so that road travelling was not affected. Standard tractors with cage wheels exert soil pressures of 3 to 4psi. They worked well on soils with a cone index above 40psi at 12 inch depth; but on soils with a cone index below 30psi at 15 inches, the tractor front end elevated and the rotovator became buried, thus causing bogg- ing (IRRI 1963). Tires with cage wheel extentions have good traction in most rice soils. The cage wheel increased the area of soil subject to shear and served as a puddling tool (Stout 1966). In tests conducted at CRRI in India (1969) cage wheels were used for improving traction. 8 Pneumatic tires with special modifications to their threads were found to be successful in limited cases by Allen and Haynes (1953). A special type of pneumatic tire has been manufactured for working in wet conditions. It was called the "rice special tire" and had high lugs, which tended to be self cleaning (Stout, 1966). Where there is a hard pan near the surface, stand- ard wheels with strakes have shown improvement in traction over standard wheels without strakes (Allen and Haynes, 1953). A simple strake wheel with five or six 10 x 10 cm. wooden strakes mounted radially on a metal frame has proved to be of some success in Malaysia. The strakes can be ext— ended and locked in position to provide the desired degree of penetration. There were however, many drawbacks. The strakes were not wide enough for adequate traction and they caused a rocking motion to the tractor (IRRI, 1971). They were difficult to adjust, as the wood swelled in water. Large "foot print" depressions were left behind the tractor. The extendable lug wheels developed in Japan and Great Britain have not been too popular in the tropics due to their high cost (IRRI, 1971). These wheels were made of steel with lugs that could be extended. The lugs were moun- ted on the edge of the wheel frame and could be locked into position when necessary. Lug wheels provided better floa- tation and traction, than the cage wheel. Special metal lugs with rubber tips were mounted, both on the inside and out- side of the tire, and extended the full tire diameter for best traction (IRRI, 1965). Tires with cage wheels and 9 extendable lugs were also tested in Burma. Trials were made with lugs which could be extended from a wide steel frame similar to a cage wheel. The lugs were extended only under difficult soils. This feature had considerable merit in clay soils where tires and cage wheels have not proven succ- essful (Stout, 1966). An extendable six-lug traction wheel, with blade settings of -5.08, +2.54, -6.35 and +10.6cm. from the tire perifery, was found to be most desirable (IRRI, 1971). Non-traction dependent tillage devices such as roto- tillers have shown considerable promise under saturated soil conditions. Performance of tractors in wet soils were imp- roved by the added rotary traction which tended to push the tractor IRRI (1963). Conventional rotary tiller blades were however designed primarily for tillage and do not effectively propell the tractor during tillage. A 3000m rotary tiller using Japanese rotary tillers, spirally mounted along a shaft with a distance of 3.5cm between blades was tested. Tillers for dryland condition had blades mounted on hubs spaced 15 to 25cms apart. The cutting pattern of the Japanese blades resulted in long narrow slices as compared to the wide and short pattern left by the conventional tiller. The differ- ence was significant in wet soils as the force resulting from the slice provided floatation and traction (IRRI, 1965). The following advantages were listed in favor of the wide tiller. 1. Less power was consumed in wheel slippage and rolling resistance. 10 2. The soil surface was left in a more even condi- tion. 3. The wide rotor provided more push to the tractor to assist in overcoming rolling resistence. Special rotors, square and triangular, were designed and fitted to a 400cm tiller frame. The square box rotor gave more floatation on soft soils, while the triangular rotor gave more penetration on moderately firm soils. Both sets of rotors required less power than those with standard till- er blades and provided push which enabled the tractor to move at a higher speed (IRRI, 1967). A special push-type tiller was designed at IRRI, with a large diameter tiller rotor and was compared with the conventional type. The push-type, wet-land rotory till- er gave increased ground support and forward push, with alternating cutting and supporting blades. Under similar ground conditions, the push-type IRRI rotary tiller had considerably less rear wheel slippage than the conventional rotary tiller. It was also found that the rotor pushing force was influenced by the peripheral blade velocity and the tiller blade velocity. A slower tiller blade peripheral velocity or higher tractor travel speed decreased the rear wheel slippage, under both soft and hard soil conditions (IRRI, 1968). A new rotory tiller with eight adjustable blade angles was tried out to find the influence of the blade angle in forward motion. In the tests conducted with angles of 12.5’, 32.5“, 52.5'and 72.5’, the 12.5‘blade developed 11 the maximum push. The highest power consumption was at a 32.5oblade angle, although it provided less pushing force than the 12.5' blade (IRRI, 1969). There is an increased use of small power tillers in Asian Countries ranging from 4-12hp, to provide better tra- fficability on rice soils than the large 4 wheel tractors. These tillers have special wheels similar to cage wheels for use in flooded soils. With a cone index of 30psi at 9 inches, these tillers moved efficiently but at cone indexes below 20psi at 9 inches, they bogged down. Small tillers with large wheels have ground pressure of 0.5 to 0.7psi and there- fore work better than those with smaller wheels on soft saturated soils (IRRI 1963). However, Reynaldo and Bantista have indicated that power tillers with streering clutches and variable speed gear boxes are generally easy to handle but are not very adaptable to soft and deep mud. Westgate (1960) reported that Chinese engineers were developing special tractors for use on paddy fields. Of these, two were selected for production; one a 3.5hp machine and the other a 27hp type. Both had bladed wheels and were light in weight and had good traction, adequate power and manoeuvra- bility. Hawkings (1958) stated that on dry land most small garden tractors suffer from the lack of wheel grip for heavy operations, and modifications to aid traction in wet fields have been unable to overcome this. He added that it may be possible that two-wheeled rotary cultivators may prove satisfactory if the engine power is mainly used for driving 12 the rotor and not for wheel traction. Special auger wheels for a 5hp tractive type tiller have also been developed (IRRI, 1964). Tandem tractors have been made by connecting two tractors with front wheels removed. Tandem tractors have four wheel drive, power steering, a center pivot action and weight balance to prevent elevation of the front end. The tandem tractor performed well under certain wet conditions where a single tractor would not (IRRI, 1963). A four-wheel drive tandem unit made by joining two 8.5hp standard tractors helped eliminate bogging and kept the operator from walking in the mud. It was found however, that the unit was under powered and weighed too much in the rear (IRRI, 1964). A light weight four-wheel riding tractor with inde- pendently driven front and rear cage wheels was tested. Land preperation was achieved by inducing a speed differen- tial between the front and rear wheels. For maximum mobility however, the front and rear wheels were driven at the same speed (IRRI, 1969). Two light weight 6hp tractors were hitched together at IRRI in 1970. Several wheels were des- igned for them, to determine which would best combine traction and tillage. A drum-wheel with tilling blades was most satisfactory in soft soils. Tilling was accomplished when the front wheels operated at 55 to 60rpm and rear at 30 to 35rpm. The machine however bogged down in soft clay soils when the sinkage was equal to the wheel diameter. A major drawback in the differential slip cage-wheel tractor 13 was the difficulty in maintaining a constant speed diffe— rential between the front and rear cage wheels which were independently powered. In 1971 at the IRRI, this was over- come by equiping a standard 7hp tiller with an extra pair of cage-wheels which were driven from the tractor wheels through two independent chain transmissions. This tiller had excellent mobility and tillage action in soft paddy fields. They concluded that the concept of a differential slip tiller can provide improved mobility and achieve till- age without additional tillage implements in soft soils IRRI.(1971). The use of cable operated equipment where cable traction is provided from the bunds for paddy cultivation was introduced in Bologna Italy (Grist, 1965). Powered winches were positioned on the field boundaries with cables as sources of motive power for traversing the implements across the field. A steam-winch operated cable tackle, originally manufactured in England by Fowlers, was thought to be an ideal mechanism for soft-soil land preperation. In this arrangement no parts of the machine were exposed to the mud and therefore no slip occured under any conditions regardless of how adverse (Ratnatunga, 1966). Cable trac- tion devices were tried in Brunei (Grist, 1965), to culti- vate their extensive areas of muck soils. Although cable traction in the past was used only for plowing, in Brunei, it was applied to all field implements. The soil was too soft for wheels and tracks, so the implements were carried 14 on sledges. Two tractors on either side of the field were used for the power driven wire rope winches. They concluded that cable operated equipment carried on sledges enabled "bottomless" soils to be cultivated mechanically for rice production. In an unpublished project proposal made by Chen, he suggested that a stationary engine fixed at a corner of the field could be used to drive a cable with an implement in a field. The speed of the engine was reduced by a gear box for driving two rotating spools. The cable was wraped onto the two spools and the tillage implements were attached to the cable causing it to move up and down the field by reversing the direction of the spool movement. The advan- tages of such a system were sumarized as: 1) there was no powered machinery in the field and more nearly all engine power can be converted into traction force; 2) different implements can be attached for field operations; 3) it was inexpensive to maintain and own; 4) easy to be manufactured with minimum industrial background and; 5) more comforta- ble and less noisy during operation. Crossley and Kilgour, (1973) at the National Institute of Agriculture Engineers in England developed what was termed the "Snail", a low cost primary cultivation implement. This was designed to provide additional power for a walking tractor to plow very hard soils in Malawi, Africa. The implement is attached to a cable which is pulled by a winch operated by the power take off of the 15 tractor. Two men operate this mechanism, one man controls the plow or implement and the other operates the winch and tractor. The tractor moves ahead of the implement to the full cable length and is anchored into the soil. The cable with the implement hooked at one end is then pulled by the winch. When the implement reaches the tractor the winch mechanism is disengaged and the tractor is moved to the full extention of the cable once again. This mechanism was supposed to provide a very efficient pull so as to move the implement through very hard soil, without which the imple- ment would not move. III - METHODOLOGY 3.1 The Selected Approach An anchored cable and winch principle was chosen to be used as a traction aid for the tractor. The winch in this approach was to be attached to the tractor and the tractor to pull itself through the mud on the cable anchored outside the field. The advantage of this method is that the tractor can pull itself by its own engine power as well as enable various implements to be attached to it. The cable on which the tractor pulls itself is attached outside the field and moved at intervals till the end of the field is reached. Details and suggestions for such a movement will be discussed in a later chapter (Figure 4.11). 3.2 Construction of the Winch A 5hp Kuboto walking tractor similar to those used in Sri Lanka was purchased from Leckler's Garden Center in La Salle, Michigan on a grant given by the FAO, Rome. Work on the construction of the winch began in the Summer term of 1974. The basic principle of the mechanism was to transfer the driving force for the winch from the PTO shaft of the tractor, and reduce the speed of the PTO shaft to operate the winch so that the cable is moved on the winch, at a 16 17 speed equal to the ground wheel speed of the tractor. This is necessary for proper working of the winch as well as to have a required tension on the cable. A half-inch Manila rope with breaking strength 1200 lbs was used instead of a steel cable. The rope provided more friction between the surface of the winch and the rope and was also considerably cheaper than the cable. Hereafter it will be refered to as the rope. The speed of the rope moving into the winch has to be equal to the wheel travel speed of the tractor at all times. If the rope take-up is too fast the tractor would be dragged through the mud without allowing for any wheel ass- istance. If the rope runs too slowly, too much rope slack causes unwanted wrapping of the rope on the winch surface and a loss of pull results. To achieve proper wrapping of the rope, the following observations and calculations had to be made. The tractor was driven at three different engine speeds (950, 1200 and 1500rpm) on a concrete floor. The time taken to travel a distance of 24 feet was taken for each engine speed as well as for both 1St and 2nd, low and high gears. The 3rd low and high gears were not used as the speed was too excessive for comfortable operation of the tractor. The third gear is used essentially for transport and haulage of trailers on paved or dirt roads. The PTO rpm was noted for every engine speed, as well as gears used. Time of travel for certain distances provided travel speeds for different gears, as shown in Table 1. 18 Table 1. --Travel Speeds in Relation to Engine and PTO rmp for Different Gears. Time to Engine Travel 24ft. Travel Speed rpm Gear PTO rpm in sec. ft/min. 950 1 low 45 63 22 2 low 160 15 96 1 high 71 4O 36 2 high 259 10 144 1200 1 low 55 5O 28 2 low 205 12 120 1 high 85 3O 48 2 high 330 8 180 1500 1 low 70 40 30 2 low -— -- -- 1 high 110 25 57 2 high -- -- -- The travel speeds obtained from the above table, were used as the rope speeds for the different gears used. Taking these rope speeds, the revolutions per minute of the winch were calculated from formula (1), normally used to calculate the velocity of belt speeds on a pulley. v = 25!; N (1) 12 where V = Velocity of the belt, ft/min- D = Diameter of the pulley, in inches N = rpm of pulley The diameter of the winch was taken as 4.75 inches. The winch used for this construction, was a Capstan winch 19 Table 2.--Winch Speed and PTO/Winch Ratio in Relation to Rope Speed and Engine rpm. Rope Engine Travel Speed Winch PTO/winch rpm Gear ft/min rpm PTO rpm rpm ratio 950 1 low 22 18 43 2.24 2 low 96 77 170 2-33 1 high 36 28 70 2.42 1200 1 low 28 22 55 2.40 2 low 120 96 205 2.12 1 high 48 38 85 2.20 2 high 180 140 330 2.28 1500 1 low 36 28 71 2.41 2 low -- -- -- -- 1 high 57 46 100 2.59 Mean Ratio 2.31 manufactured by Parker Thompson Associates, Fenton, Missouri. The diameter of the winch in the manufacturers specifica- tions was 4.25 inches but when considered with the rope, the diameter for calculations was taken as 4.75 inches. 0.25 inches were added on either side of the winch drum for the half inch Manilla rope. By using formula (1) the winch rpm was calculated for different travel speeds obtained from Table 1. After the winch rpms were obtained for the different gears and travel speeds of the rope, the ratio between the PTO rpm and winch rpm was calculated and tabulated as seen in Table 2. The information in Table 2, reveals that on an 20 average,the reduction between the PTO shaft and the winch should be 2.31:1. It was not possible to reduce this to the exact value unless gear wheels were designed for such a reduction. The sprocket wheels for reduction were obtained from available parts in the Agricultural Engineering Depar- tment and the closest sprocket wheel necessary for the reduction was chosen. Formula (2) was used to calculate the diameter of the driving pulley. ___ = ___ (2) where d2 = The diameter of the driven pulley d1 = The diameter of the driving pulley n1 = Rpm of driving pulley n2 = Rpm of driven pulley The diameter for the driving pulley was calculated keeping the diameter of the driven pulley at a maximum of 8 inches, for ease of construction. From the calculation a driving pulley of 3.46 inches was needed. The closest size available was 3.5 inches. Prior to using the winch supplied by Parker Thompson Associates, a winch drum was constructed in the shop. Figure (3.1) shows the sketch of the winch drum constructed. There were several drawbacks and limitations in this construction. The drum was too heavy for the trac- tor and caused the tractor to tilt downwards. Therefore 21 zofl> mUHm xom meow AN 3mH> choapoom :mm J‘ 5.. seem secs; 11:1 1. ELLE r xom ammo mo pmeem pSQPSO .HsmmwoooSmGD on op Uo>onm same one .mozm one CH empescpcho sewn seen; esp co nepegm < :mmh H.n enemas 22 operation of the tractor from behind was extremely difficult. Addition of weight to the rotovator case, did not help correct this situation. The drum was made of a six inch diameter galvanized pipe and therefore did not provide an adequate friction surface for the rope to pull the tractor forwards. Continuous slip of the rope on the drum surface resulted. Addition of a rubber lining on the drum caused excessive wrapping of the rope. Excessive wrapping was due to the high friction surface created by the rubber lining. Crowding of the rope resulted. The rubber layer did not provide the necessary slip when excessive loads, were experienced by the drum. When the rubber was used as a friction surface the rope got jammed so badly that it ele- vated the back of the tractor and made operation from behind impossible. Many tests were performed with this winch without much success. The drum was therefore discarded and a new method sought. The Capstan drum had been designed and used in a wide variety of pulling and lifting operations in the construction industry. A Capstan drum was tested instead of the winch drum constructed in the shop. The only availa— ble Capstan drum in the time period available for testing was at Parker Thompson Associates in Fenton, Missouri and therefore a 500 series Capstan drum was ordered. The increasing contour diameter of the Capstan drum has a pro- gressively longer circumference, which makes the rope wind 23 on the Capstan. The combined axial and circumferential creeping tendency created, increased the frictional quality of the hard anodized Capstan surface and permited a free running take up without rope crowding. The hard coat, heat treated aluminium drum, reduced the weight on the front end of the tractor considerably, compared with the previous drum and thus made operation of the machine easy. On test- ing, the Capstan drum proved successful and provided efficient pulling of the tractor with the rope. To effect transmission of the drive from the PTO to the winch a 90° drive gear box was obtained from availa- ble parts. The ratio between the horizontal and verticle gear arrangement was 1:1 and therefore the only reduction in gear speed was between the PTO and the input shaft of the gear box. The reduction in gear speed was brought about using the 3.5 inch sprocket attached to a 1-inch shaft which was subsequently attached to the PTO shaft of the tractor. The 1-inch shaft was machined in the Mechanical Engineering shop with a precision 2 inch long bore of 17mm and an inter- nal % inch keyway. The keyway was used to effect the joining of the shaft to the PTO. The keyway prevented damage to the PTO shaft and its bearing at times of a heavy load. A 1- inch pillow block bearing was used to support the shaft. An 8 inch sprocket was attached to the input shaft of the gear box so that there would be an effective reduc- tion from the PTO to the winch. (A pulley system was used 24 —_—.—.— 7, 1 7 ~ 1 ,,,,1 ——r~—i— ,__ Figure 3.2 A view of the braces and frames used to support the gear box, extended PTO shaft and all other accessor1es. at first, but due to the force generated, the belts slipped. Therefore a positive drive was needed). A 1-inch pillow block bearing was attached to support the shaft. A key was used to fasten the sprocket to the shaft. Braces and frames to support the gear box and the extended PTO shaft were constructed with 1/8 inch angle iron. Heavy gage metal was used for areas where high force was expected, so that the gear box had enough support for the pull generated by the winch (Figure 3.2). To attach the winch on to the gear box, a shaft with a one-inch bore to fit into the output shaft of the gear box had to be machined. A threaded end was made to hold the winch in place. To keep the rope coming off the winch tight, a 25 Figure 3.3 A closer look at the winch assembly showing the change in direction of the rope by using the pulley arrangement. mechanism was designed to make use of the drive provided by the input shaft of the gear box. A 5-inch pulley was attached to the shaft. The direction of the rope was rever- sed by making use of a pulley arrangement shown in Figure 3.3. An idler roller was used to keep the rope tight on to the pulley and this made the shieve pull the rope at the same rate at which it came into the winch. The rope was then laid down on the ground without much tension. 3.3 Construction of the Rice Paddy The appropriate method to test the mechanism constructed was to run the machine in a saturated field, similar to those in which rice is grown in most lowland rice producing areas. To achieve this objective, it was 26 decided that a rice paddy resembling those found in Sri Lanka would be built in the Soil Science research field at Michigan State University. Several areas with a high level of water retention were selected. Out of these areas, a plot from a field previously used to grow sweet corn was selected as the most suited, considering the distance from the water source as well as the existing condition of the field. Since most paddies in the wet-zone of Sri Lanka are very small and bro— ken up into small plots (Liyadda's), a suitable field size 100 feet long and 40 feet wide was chosen. This area was Lfi plowed and later harrowed to bury the corn stubble left 7 from the previous crop. A dyke was built around the peri- meter, so that water could be impounded when ever necessary. Water was supplied to the field by a series of pipes connected to a water pump supplying the research field. After the dyke was built, water was sent into the field to test the holding capacity of the soil. Water was kept at a 3-inch standing level for about 1-2 hours and then receeded until the water drained out completely, about four hours later. This enabled traction tests to be performed at a water level of 3-inches or more and there- fore was very satisfactory. The paddy is illustrated in Figure 3.4. Soil samples were taken at random, to determine the soil texture of the working area. 27 ___—*1 Figure 3.4 The rice paddy constructed on the Soil Science research field at Michigan State University. 3.4 Egeld Testigg Field testing was done towards the latter half of October after the winch was constructed and perfected in the shop. Numerous tests were performed on the compound of the Agricultural Engineering Department, to ensure proper work- ing of the winch system before field tests were actually carried out. The main test criteria was to determine the travel speed of the tractor in the saturated soil, with the winch, as well as without it. To show the differences in travel speeds between different soil conditions, the following tests were performed. Travel speeds were determined for the two forward gears both on low and high for three different rpms of the 28 engine - (950, 1200 and 1500), on concrete, firm soil, saturated soil and saturated soil with the winch system. Rpms were measured by a tachometer placed at the engine output shaft. a. Concrete.-—The travel time for a measured dis- tance of 20 feet was taken for the different engine speeds and gears, measured on the concrete floor outside the Agri- cultural Engineering building. Ten travel times were measured for each gear and each engine speed. From these measurements the travel speeds were calculated. b. Firm Soil.--The tractor was tranSported to the Soil Science field where the paddy was constructed. Field testing began on the 22nd of October 1974. The soil was relatively dry at the start of the tests. Ten soil samples were taken to determine the moisture content of the soil at the time of testing. Similar tests were performed as those for concrete, for the different engine speeds as well as gear speeds, although in this case, the machine was run without the rotovator, as well as with the rotovator (Figure 3.5). Ten travel times were recorded for each set of engine and gear speeds, for a travel distance of 20 feet. Foward travel speed was calculated from these readings. The engine stalled at all rpms in the 2 high gear, when the rotovator was used and therefore readings were not taken for this gear. 0. Saturated Soil.-—The water was let into the field about one hour before the tests were started and the 29 Figure 3.5. Operating the tractor on firm soil conditions with the rotovator. tractor was put into the field when there was approximately 3-inches of water in the field. This represented a typical wet lowland rice field, where the soil was muddy and pro- vided little support for machinary. The tractor would not move at the engine speed of 950rpm. The engine stalled as soon as the machine entered the field. The tractor did not move at other engine speeds, although at 1500 revolutions it moved about ten feet into the field and then got bogged, (Figure 3.6). Under the saturated conditions, no forward travel speeds were recorded since the tractor did not move. d. Saturated Soil with thetflinch.--The winch system was tested on the field extensively before actual readings were taken. The field was saturated at all times and the rope was located outside of the field (Figure 3.7). 3O Figure 3.6. The tractor bogged down in the saturated soil without any further movement. Figure 3.7. The rope is attached to the pickup serving as a anchor located outside the field. The pic- ture illustrates the tractor being pulled through the saturated soil by the winch and rope. 31 The braces on the pulley that reversed the direction of the rope were weak and kept bending and therefore had to be modified. Continuous testing of the tractor and the functioning of the winch system resulted in the addition of a further set of braces to prevent an upward bending force on the winch braces. After much testing, it was decided that the winch system was ready for field observation. Ten soil samples were taken to establish the soil moisture content for the tests. Free water in the soil samples was drained out of the containers, leaving very wet soil in the cans. Testing the tractor began by tying one end of the Manilla rope to be used on the winch, to the tow- bar of the pickup used to transport the tractor to the field. The pickup was then reversed, so that the rope was attached approximately at the end of the field. The free end of the rope was then brought to the opposite end of the field and attached to the winch as follows. The rope was wrapped three times around the winch. The rope was then taken through a guide to the pulley that reversed the direction of the rope (Figure 3.8). The arrow points at the direction at which the rope is anchored. The rope is then guided on to the take-up pulley where it is held in place by increasing the pressure exerted to it by the idler pulley. This is done by tightening the idler pulley on to the rope by using the adjusting nut. This makes the rope turn in the direction of motion of the pulley. The rope coming out of the winch is therefore kept tight and 32 ADIRECTION OF ANCHOR :33? i: NPUT SHAFT I; i '1‘ ) j: M f: ~——-—~’-z, PULLING WINCH y; SHIEVE L. . 1: \ l— ‘-:- DJUSTING GEAR 8" SPROCKET I: BOLT BOX I: CHAIN Figure.-- 3.8 A Sketch Showing the Method used to Reverse the Direction of the Rope Leaving the Winch Assembly. 33 ensures proper wrapping of the winch. A rubber coated pulley in future designs would provide better friction between the rope and the pulley and therefore would not need high pressure from the idler. The system was so con- structed that the attachment of the rope to the winch and pulleys, was easy and fast. Once the rope was attached to the system the engine revolutions were adjusted as before. On the 151; low gear at 950 rpm, the engine stalled as soon as the tractor entered the field. Similar results occured on the high gear too. Therefore at this low engine rpm the tractor would not move even with the help of the winch. The engine speed was then increased to 1200 rpm where the tractor began pulling itself on the rope by means of the winching system, in both the high and low ratios of the ist gear. Ten readings of travel time for a distance of 20 feet were taken. The 2nd gear caused the engine to stall and therefore no readings were taken. Similar readings were taken at an engine speed of 1500 rpm. Ten readings for travel time both for high and low ratios of the first gear, were recorded. The second gear was not used due to the uncontrolable nature of the machine at this high engine rpm. The pull exerted on the rope by the winch was recorded in lbs of pull. This was done by means of a spring dynamometer attached to the pickup tow bar and the free end of the rope. The dynamometer was previously calibrated in 34 the shop using a 100lb dead weight. Recordings of lbs pull were taken for every 20ft run observed. The rotovator was used in the saturated condition, for all observations made. Due to bad weather which prevailed during and after the experimenting period further field testing of the machine and system was not possible. IV - RESULTS AND DISCUSSION 4.1 Presentation of Data Traction characteristics of Agricultural vehicles are largely governed by the dynamic properties of the soil surface in which they are working. In wet rice soils, mobility of vehicles is restricted by numerous factors, characteristic of the prevailing soil conditions. Tractive effort in soil is developed when the soil is subjected to shearing action. The shearing action in the soil is influ- enced by the cohesive forces and internal frictional forces occuring between soil particles. In wet rice soils, fail- ure or yielding of the soil can be evidenced as a plastic flow without shatering and development of shear failures. Increased moisture contents experienced by saturated soils, cause the soil to develop into a lubricative phase where there is a loss in internal friction and a loss in soil cohesion between soil particles (Johnson, 1965). This influences the soil strength and therefore the inability of the soil to support machinery. Five soil samples from the rice paddy constructed on the Soil Science research field, were analysed in the Soil Science laboratory at MSU. The results of the mecha- nical analysis using the pipette method are shown in Table 3. 35 36 Table 3.--Mechanical Composition of the Soil. Sandyloam (USDA Classification). Average % for five Samples Sand 64.8 Silt 22.3 Clay 11.9 Bates, (1957) indicated that there are three types of wet paddy lands. 1) The clays, with a firm pan or bottom a few inches below the surface: 2) the silt and sandy silts which are hard baked in the dry season and completely water logged in the wet season and do not have a hard pan layer, within the reach of the surface: 3) the peats. The mecha- nical analysis of the soil samples collected from the field show that the soil in which the tests were conducted belong to the category of sandy loams, as shown by the USDA soil classification. Analysis of the soil moisture content on the dry weight basis for both the saturated soil as well as the firm soil gave the following results. An average of ten samples for the firm soil condition gave a moisture percentage of 18.9%. The indicated moisture percentage was due to the flooding of the entire field done fourdays earlier, to test the water retention of the field. Several "wet spots", especially where the water pipe was fixed, were noticed. 37 Table 4.--Average Travel Speeds on Different Surface Conditions for Varying Engine Speeds and Gear Ratios. Travel on Firm Soil Travel on Travel on without Firm Soil Saturated Saturated Engine Concrete Rotovator with Roto. Soil with- Soil with Speed Gears ft/min. ft/min. ft/min. out Winch Winch 950 1 low 24 22** 21* no movement stalled eng. 1 high 37 36** 34* no movement stalled eng. 2 low 98 95** 84* no movement stalled eng. 2 high 148 -- -- no movement stalled eng. 1200 1 low 29 28** 27* no movement , 29*** 1 high 48 47 45* no movement 4?*** 2 low 123 105** 96* no movement stalled eng. 2 high 177 -- -- -- -- 1500 1 low 36 35** 33* no movement 35*** 1 high 58 56** 54* no movement 56 2 low Speeds Too Fast 2 high Speeds Too Fast * Significant difference between speed with rotovator and without rotovator: DC = 0.05 ** Significant difference between speed without roto- vator and speed on concrete: cc: 0.05 *** No significant difference in speeds between speed on concrete and speed with winch. In the saturated soils the average moisture percentage in the rice paddy was 31.7%. Tests with the tractor were performed on both these moisture conditions as mentioned in the Chapter III. Travel speeds obtained for the concrete surface as well as the four soil conditions and the average speeds for different gears and engine speeds are shown in Table 4. Figure 4.1 represents the speeds calculated at 950 rpm, 38 Forward speeds for different gears at 950 rpm engine speed,under varying surface conditions. Figure 4.1 »~v mu deem .mww.mwnmmwm. o... .0 .0. oo- o o o... 0.0.0. o o c 00 o 0 no. cocoo.ooo.oooouoooo.ooo.o ANS---Leeee>oe oe-ee~aeee eeaweo-eeeas and: -AHOm eme o 5 80b 0 ‘5 'u .93. 7G. a. Q U U) o. g -H on c . o 5' I .C U c "-4 4 3 o f. .c H U V 3 A. '5 H w-l .--I 3 m H 2 8 '8 Q ' A. A m f C: :1. -c 0 ,, 8 10 E '2 u a U '8 38 3 a U ° 'a_fl :a a l j_ _. lst gear 2nd gear 2nd gear LOW HIGH LOW -Firm soil(182 moisture)without rotovator. -Firm soil(18% moisture)with rotovator. -Saturated soil without the-winch. ’ 3 -Saturated soil with the winch. 52 Fig. 4.9: ‘7. Loss in forward travel speed taking zero loss on concrete. The tractor is operated at 1500 rpm.engine speed for varying soil conditions. 100 90 U! 0‘ \l on O O O 0 Z LOSS IN FORWARD SPEED a~ O 30 20 10 l..- lst gear lst gear 2nd gear LOW HIGH LOW ~-Firm soil(18Zmoisture)no rotovator. I -Firm soil(181moisture)with rotovator. -Saturated soil with-out winch. i -Saturated soil with winch. Z EFFICIENCY IN FORWARD TRAVEL 53 20 30 40 50 6O 70 80 90 100 110 1 O 100% v 1 1 y v f £1 ‘ --Satlrated soil with winch. 1 ¢ 9 \ 5 Firm soil without ___4y—r”'ck rotovator-4-- 908:4 J ‘\\ .5 l l I I 80a; Firm 8011 with rotovator-44- \ 75 I 5 Saturatdd soil with t winch U—t 30 40 5‘0 60 70 so 90 100 110 120 TRAVEL SPEED ON CONCRETE ft/min. Figure.-- 4.10.Efficiency in forward travel forward speeds. The speed on CODC taken as 100% effecient. for varying rete is 54 the test conditions on firm soils as well as tests in saturated soils without the winch, the winch system showed a marked improvement, for traction efficiency. Thus mobility is maximized by the use of the winch. 4.3 Analysis of the Winch System Sinkage of the tractor as seen in the tests with- out the winch is typical of that experienced in the satu- rated paddy soils in Sri Lanka. The lower soil strength of saturated soils is unable to bear the weight of the tractor. The prolonged slipping of the wheels reduces soil shear strength further and makes the tractor sink deeper into the soil. Adhesion of the mud filling inbetween the lugs of the wheels cause a smooth surface to develop. This makes the lugs on the wheels ineffective. Traction is therefore limited and the wheels do not provide the necessary power transmittal to the soil to bring about forward pro- pulsion. The wheel diameter and width of the test tractor is small compared with the conventional large diameter paddle wheel and therefore hindered the forward movement of the tractor. Domier (1967) showed that larger diameter wheels increased traction efficiency on various agricultural soils. In typical saturated rice soils of most Asian countries, large paddle wheels replace the pneumatic tires to aid in traction. The floatation effect provided by the paddles helps in keeping the tractor from sinking by aiding power transmittal but still does not completely eliminate 55 slipage of the wheels. A test with this type of wheel would help in gaining better forward movement in the saturated test condition, compared to the zero movement observed. The fact that the paddy field was plowed and harrowed before actual field tests were done, caused the strength of the soil to be reduced when saturated compared with a field with stubble left from a previous crop. The soft soil in this test is quite an exageration of the conditions normally experienced, where crop residues are present during initial land preperation. The stubble of crops, increases the soil strength and trafficability of the tractor in the soil. Further studies of the winch system would be desirable to determine its efficiency where actual crop residures exist on the land during the tests. The use of the roto-tiller did not help in forward movement under these test conditions. In tests conducted on large four wheel tractors in the International Rice Research Institute, it was found that an adjustable 155cm wide x 900m diameter, 8 blade rotary tiller at a blade angle of 32.5° gave a push of 300 to 900kg at a tilling depth of 100m (Kahn, 1968). The test performed with the two-wheel tractor in this study showed no assis- tance from the rototiller for forward movement. The reason is that Without the winch action the added weight of the winch mechanism caused the front-end of the tractor to tip downwards into the soil, lifting the back, causing little contact between the soil and the blades for forward 56 propulsion. This combined with the fact that since there was little help given for forward movement by the spinning mud coated wheels, the tractor could not provide the necessary traction to move forward. The attachement of the winch to the tractor as a traction aid provided a positive improvement in traffica- bility. The winch enabled the tractor to pull itself on the rope through the field. Without the winch, it was impossible. The most significant advantage seen from using the winch system is that the traction aid is entirely independant of the soil condition as compared to the con- ventional traction aids. The earlier developed innumerable traction aids such as the cage wheels, 'extendable lugs, hollow steel wheels with steel lugs, crawlers half-tracts etc: all depends on the surface textura,soil shear strength and condition of the soil for its performance. Stout, (1966) indicated that different methods are needed for supporting machinery and tractors for different soil types. Penetration by means of special lugs and extentions on the wheels are made for clay soils so that they could reach the "bottom". Floatation devices are sought for the peats, to keep the equipment on the surface of the soil by using wide and large diameter wheels or long tracts. These wheels distribute the weight over a larger area as possible. The winch system however does not depend on the soil, and there- fore is applicable in any soil type. 57 The winching system is directly connected to the PTO drive of the tractor by a positive chain drive. There- fore it pulls the rope at a forward speed approximately equal to that found on concrete (Table 4). Slip of the rope on the winch surface causes the loss in speed observed. On the 1'5t low gear at an engine speed of 1200, the loss in forward speed is 0.7%, showing that there is an efficiency of 99.3% in moving the tractor forwards, compared to the- 100% mark on concrete. A better value of 99.6% is seen on the higher gear indicating a forward propulsion provided by the wheels and the rotovator. A higher loss was experienced in the 1st low and high gear 1.0% and 2.8% respectively, at an engine rpm of 1500. A higher loss could be attributed to the slip of the rope at this speed. The rope at this stage of testing was extremely wet, and could have resulted in slipping due to the lubricative effect of the water: but in comparison to the 100% loss in forward speed experienced in saturated soils without the winch, this was indeed a tremendous improvement. Figure 4.6 shows that the tire lugs are no longer packed with mud when being pulled forwards with the winch system. The winching action and resulting motion seem to cause a "cleaning" effect of the tires, thereby exposing the lugs. Traction by the tire is thus improved. From the pounds pull observed at the different engine speeds, Table 5, the average horsepower developed by the winch in pulling the tractor was found to be .69 58 for 1200 rpm and .64 at 1500 rpm. A significant difference between the hp at 1200 rpm and hp at 1500 rpm for the ten observations was shown at NC = 0.05. A significant diff- erence in hp was also observed between the low and high gears at the respective engine rpms. at: 06‘. 0.05. An average of .67 hp is used up by the winch in pulling the tractor out of the muddy conditions, at the working engine rpms. The independant nature of the winch in regard to the soil conditions, is the reason for the very low hp rate observed. Since no slip or rolling resistence is experi- enced by this traction aid, the only work it has to perform is to pull the tractor forwards, aided by the propulsion of the rotovator blades and the wheels. Further research should determine the actual hp distributions between the winch, rotovator and the wheels in the saturated condition, so as to determine the energy consumption of such a system as against that of the tractor with out the winch, in saturated soils. This would give a better understanding of the power efficiency of the winch system as a whole. Winter weather and freezing soil prevented these additional tests. Use of steel paddle wheels with the winch system, or increased diameter wheels in further tests may also provide significant results as to the efficiency of the system in the given saturated conditions. 59 4.4 Application of the System Field sizes for rice cultivation in saturated soil are small. A one acre rice field would normally be divided into quarter acre blocks or smaller. Therefore anchoring of the rope to a point outside the field could easily be done by the operator. In most Asian countries labor is abundant. It is very common to see numerous people watching a tractor working in the field. Making use of labor to attach a rope to an anchor point would not be a problem, especially in family farms where family help is available. Figure 4.11 represents a proposed method of application for the designed winching system, on a land area 40ft wide and 100ft long, using a tractor having a working width of 3 feet. This system would make use of the operator to anchor the rope on to the edge of the field. The stakes are represented by a * on the field in Figure 4.11. These would be the anchor points. They could be either temporary fixtures or be permanent, in which case they may be used for all cultivation seasons there-on. The latter is preffered. This prevents excess use of time for driving the stakes into the ground. The proposed plan is for permanant stakes. The stakes could be either made of strong wood with a ring attached to it, or made of steel. The construction of the stake would depend on the maximum pull exerted by the winch. A hook attached to either end of the rope would help in hooking the rope to the ring on the stake, saving time on the tying operation. 60 .Eoummm songs ecu mo cofiumoEHddm comedowd ecu pom causaosum .HH.¢ ::.ow:wam [II |‘ ‘ m cram 61 The tractor in this design could start on either side of the field, puddling the soil progressively to the right of the field or progressively puddling the soil to the left of the field. The rope coming out of the take-up pulley is slack and therefore does not need any tension. Figure 4.11 shows the tractor unit attached for its first movement to the side B of the field. The rope from the take up is attached to Al on side A of the field. When the operator has moved to B by pulling on stake B1, he removes the rope from B1 and then from the winch, by unwrapping it from the bottom of the winch and pulling it out from the take-up pulleys. The tractor is then turned and ready to move towards A by pulling on the rope attached to A1 at the begining of the operation. The rope removed from B1 is wrapped around the winch system, and sent through a rope guide (G) on the tractor and fixed onto the anchor B2. The guide prevents the rope getting entangled with the tractor and the rotovator at any time during the operation. There will be plenty of slack on the rope going through the guide to B2, as no tension is required for the rope leaving the take-up pulleys. When the operator moves to A1, he removes the rope on A1 and unwinds the rope on the winch system. The tractor is then turned to face B. The operator winds the rope around the winch system and attaches the end to A2. The tractor is then moved across the field by pulling on anchor B2. This process is repeated till the end of the field is reached. V - CONCLUSION The following conclusions were arrived at, based on the evidence of the tests performed. 1. 3. The Capstan winch drum attached to the tractor assembly provided a steady pulling motion through the rope without rope wrapping or excessive slip. Reduction in travel speeds were observed on firm and saturated soil, as compared with the speed on concrete. No forward movement of the tractor was possi- ble without the winch in the saturated test soils, due to unlimited wheel slip and sinkage. The rotovator did not provide the traction assistance in the winchless condition, to help move the tractor in saturated soil. The winch provided a positive pulling force to move the tractor through the saturated soil. The winch system showed positive results as a traction aid to increase mobility in rice fields, the objective of the project was justified. 62 1. VI - RECOMENDATIONS FOR FURTHER STUDY Determine the efficiency of the system as regards to its power distribution and energy consumption between the winch, rotovator and wheels, compared with the energy lost in working the tractor without the system. Repeat tests performed, by attaching a con- ventional traction aid in place of the pneumatic wheels, and compare its efficiency with that of the winch. Repeat tests without the rotovator to determine the pushing effect of the rotovator when the winch is attached. Perform similar tests, varying the soil con- ditions in relation to the presence and absence of crop residues and determine the respective efficiencies of the system. Design and construct an anchor point to withstand the pull exerted by the winch. Evaluate the entire system as to its effi- ciency in relation to, energy use, time study effective use of abandon land, and its economics. 63 REFERENCES REFERENCES Allen, E. F. and Haynes, D. W. M. 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Progress in the Mechanization of Farming in the Colonial Territories II. 32, Tropical Agri- culturist. 1956. Ponnamperuma, F. N. Chemical Changes in Flooded Soils and the Growth of Rice. IRRI. Seminars March 18-April 15’ Po 1+1. 1967. Ratnatunga, D. M. Mechanization Possibilities in Rice Production. Paper Presented to the Symposium on Research and Production of Rice in Ceylon. Ceylon Association for the Advancement of Science. Colombo: Sri Lanka, April. 1969. Reynaldo, M. Lantin and Bantista, Roberto C. Land Preperation Equipment and Tillage Practices for Rice Production. Rice Production Mannual. College of Agriculture, University of Philippines, Pp. 365-366. 1970. Stout, B. A. Equipment for Rice Production. Rome, FAO. FAO Agricultural Development Paper, No. 84. Pp. 41-45. 19660 Westgate, R. Agricultural Mechanization in China, World Crops, 12 (6), 228-30. 1960. "Illllllll'lllllllI