Design and Fabrication of Underground Vegetable. Harvester

Transcription

1 Design and Fabrication of Underground Vegetable S.Karthik Subramanian Harvester K.Kaushik S.Karthik S.S.Parthipan Subramanian, Raj parthipanss@gmail.com 2 K Kaushik, 3 S.S.Parthiban Raj, 4 P.Naveen Department of Mechanical Engineering, P.Naveen naveenprabakaran95@gmail.com Easwari Engineering College, Chennai, INDIA ABSTRACT This project aims to harvest underground vegetables such as potatoes, onions and carrots in an efficient manner. This harvester was fabricated to facilitate effective harvesting and to reduce manual efforts of harvesting underground vegetables by farmers in the field. This objective was accomplished by a setup consists of a set of jaws, a conveyor setup and a collection box. These were connected by a set of gears actuated by chain drives. The project was done after conducting studies on various approaches towards vegetable harvesting. Crop parameters and field parameters were considered. The distances between placements of successive crops were considered. The experiment was done to get an insight of both qualitative and quantitative aspects of the field as well as the various reactions to impacts during harvesting. A few areas regarding scope for future improvements were discussed and suggestions were made. Keywords: Harvester, Onions, Shared-lifting, Sprocket Harvesters I. INTRODUCTION Vegetable harvesters have been used to harvest underground vegetables in farms. There are various designs of tools and equipment used for harvesting the crops and threshing it separately. Sickles, hand tools and reapers for grain crops and diggers for tuber crops and rhizomes, operated with different power sources are used. Combine harvesters, both tractor mounted and self-propelled, are being very widely used for different grain crops. Vegetable harvesters are generally categorized based on the method of lifting vegetables. They are of two types - top-lifting and shared-lifting. Top-lifting harvesters consist of pointed jaws that grab the vegetables out of the ground. Shared-lifting harvester consists of blunt jaws that grab soil along with the vegetables. Fig.1 Shared-lifting vegetable harvester A common shared-lifting type of vegetable harvester is shown in Figure 1.1. In this type of harvester an enlarged jaw which is twice the size of the vegetable is used to grab the vegetables completely from the ground along with the soil. The collective produce is transferred to a container where the soil is removed my various methods including pores, vibration or by manual selection. The top-lifting type of vegetable harvester consists of pointed jaws that are exactly designed to hold the vegetables and pick them from under the ground. The vegetables are then placed into baskets for collection [10]. The top-lifting harvesters also cut the external top portion of specific vegetables like carrot, onion etc. This is accomplished by when the belt of the harvester carries the vegetables; there is a cutter that is attached to the end of the belt which cuts the top of the vegetables. II. LITERATURE REVIEW For years environmental changes have affected the harvesting process. Vegetables have been harvested from various concepts and methods. Carrots, 12

2 Radishes, Onions, Potatoes have been developed by mechanical harvesting methods for the last three decades. A site-specific sugar beet yield monitoring system was then developed and tested. Two weightsensing systems (155 mm idler wheels attached to load cells and the replacement of two existing idlers on each side of the harvester outlet conveyor with slide bars) were developed, tested and evaluated on a laboratory test conveyor. Laboratory tests to predict accumulated weight showed a 3% error for the slide bar system and a low percent error for the idler wheel system [9]. A field study was conducted to evaluate three realtime weighing systems to measure sugar beet yield. There was no statistical difference between two of the sensors, but there was for the other one and the system provided unacceptable results. One of the systems provided reasonable accuracy and allowed for use of the on-board storage hopper [3]. The yield measurement equipment, consisting of a weighing frame, load cells, speed sensors and dataacquisition apparatus, was developed and tested both under laboratory and field conditions. The field observations confirmed the high accuracy attainable with the system applied in which the weighing accuracy ranged from 2.5% (too low) to 4.8%, (too high) with an average weighing accuracy of 1.36% [7]. Abd-Rabou concluded that there is a decrease in total damaged roots by decreasing forward speed. It is clear that, increasing forward speed from 0.55 to 1.08 m/s tends to increase the total damaged roots from 4.91 to 5.6%. The highest value of the total damaged roots of 5.6% was obtained at forward of 1.08 m/s therefore the lowest value of the total damaged 4.91%was obtained at forward speed of 0.55 m/s [1]. Determination of Basic Dimensions The basic external dimensions were decided based upon the study of vegetable harvesters. The wheelbase of the vehicle was decided as 1500 mm and the track width was decided to be 640 mm. It was decided to include links inside the frame of 3-4 in number to strengthen the frame. The height of the support was decided to be 420 mm. The angle for the jaw was decided to be around degrees. Suitable motor and gears were decided based on requirement. Parts After the determination of basic dimensions of the harvester, the part design of the various parts of the harvester was done. The part designs of various parts are described below in detail. Frame The design of the frame of the harvester is shown below. It has an overall length of 1720 mm and an overall width of 640mm. It is supported by a pushing frame which has a height of 420 mm and a width of 627 mm. The frame is rigidly supported by three support links of width 640 mm. The frame consists of two vertical supports of 350 mm each to place the conveyor roller bearing. The frame design is shown below. Fig.2: Design of Frame III. DESIGN & ANALYSIS The CAD model of the product was designed to determine the external dimensions of the harvester. The harvester consists of a rectangular frame with links provided inside it to place components. The jaws are closely assisted by a roller setup which takes the vegetables from the jaws to the collecting box. On the way to the box the impurities present with the vegetables are withered out. The jaws are powered by a motor setup. The rollers are moved by actuation from the motion of wheels. Sprocket (Jaw) The sprocket was designed based on the dimensions of the vegetables that were being harvested. The sprocket was decided to be at an inclined angle of 45 and consisting of two parts. The first part is shorter with a length of 60 mm and is meant to be attached to the sprocket bearing. The second part is longer with a length of 100 mm and meant to dig into the ground and harvest vegetables. The width of each jaw is 75 mm. The design of the shaft is shown below. 13

3 Analysis The various components of the harvester were analysed based on stress and moment reactions. Static Structural Analysis of Frame Assembled setup of Jaw Fig.3: Design of Jaw The assembled setup of jaw is shown below. A single set of jaw assembly consists of three sprockets which are attached at an angle of 120 degrees apart from each other. These jaws are bolted in the jaw bearing and fixed on the bearing disc. This jaw is then mounted on the jaw shaft. The frame design of the harvester was analysed using static structural analysis. The rear end of the frame was fixed using fixed support. The front end of the frame was given a load of 700N. Based on the overall result of this analysis, we can conclude that the frame design is safe. Fig.6: Static Analysis of Frame Modal Analysis Fig.4: Design of Assembled Setup of Jaw Assembled View of Harvester The assembly of harvester is represented below. This contains all the parts including the fixtures used. The various views of the harvester are shown below. Modal analysis is done on a component to determine its frequency under no load condition during a transient period of working. The frequencies of the frame analysed is depicted below in the modal graph. The frequency obtained is x 10-3 Hz. Fig.7: Modal Analysis Graph of Frame Fig.5: Isometric View of Harvester Torsional Analysis 14

4 Torsional analysis is done to determine the torsional effect on the component due to load at the boundaries of the component. Torsional Analysis was done on the shaft of the sprocket. The results of the torsional analysis is shown below KW Speed of Motor 85 rpm Torque (Motor) 60 (P/2πN) ( )/ (2π 85) ( )/ Nm. Torque Reduction Ratio T s /T m (25)/ (25.142) Fig.8: Torsional analysis of Shaft Fatigue Analysis of Shaft Fatigue analysis is done to determine the reaction of a component under constant load. This analysis is done to determine the life expectancy of a component. The fatigue analysis displays the life, fatigue sensitivity. The result of fatigue analysis is shown below. The shaft Speed of Jaws 85/ rpm. Speed of Conveyor Rollers: Torque required to carry vegetables (T c ) Force Distance FOS Force 3kg N approx. T c T m ( )/ (2π 85) Fig.9: Safety factor of Shaft Torque Reduction Ratio T c /T m 38.76/ Speed of Conveyor Rollers 85/1.54 IV.DESIGN CALCULATION: Calculation of Speed of Jaws: Torque required to penetrate sand Force Distance FOS T s 250N T s 25N Power of Motor 0.3HP rpm Time elapsed for vegetable to travel: V πdn/60 (π 80 55)/ m/s Length of travel 350 mm 0.35 Time, t L/v 15

5 0.35/ sec V. FABRICATION The fabrication of the underground vegetable harvester begins with the fabrication of the base frame of the harvester. The frame is made of L-shaped rods with an overall length of 1720 mm and an overall width of 640 mm. The various links are joined together using welded and bolted joints. Fabrication of Jaws The fabrication of one set of jaws was carried out as follows. The jaw was fabricated from square shaped rods. The square shaped rods were taken and one side of the rods were removed. After this process the rods were reduced to a dimension of 160 mm. After this they are marked as two parts with lengths 60 and 100 mm respectively. Fabrication of Rollers The fabrication of frame is followed by the fabrication of the rollers required for the conveyor setup. Two rollers are required for the actuation of conveyor. The processes that are involved in this are: Turning Chamfering Facing Drilling Grinding Boring After the fabrication of rollers the bearing that go with the rollers were fabricated. The fabrication of bearing was made according to the inner diameter of the rollers. The ends of the bearing are machined to a lower diameter to facilitate the actuation by pulleys. The bearing is fitted inside the pulley. Fig.11: Fabrication and Assembly of Jaws These two parts were heated at the junction using gas cutting equipment and the interjunction was gas-cut at 45 degrees and then bent to 35 degrees. The ends of the jaw was chamfered and then machined using grinding equipment. Three jaws constitute one set of jaws on a shaft. A rod of diameter 55 mm and length 105 mm is machined using lathe equipment. On this three jaws were place at an angle of 120 degrees from each other. The jaws were fixed to the base by means of bolted joints.two sets of jaws were attached to the shaft present at the frontal region of the harvester. The jaws are shown in Fig 4.2. Assembling the Harvester The assembly of the harvester was completed as follows. The frame is mounted on the wheels and made rigid. One roller-bearing assembly is place at the higher link in the centre of the frame while the other link is connected at the front portion of the frame. The conveyor belt is fixed between the rollers and clamped together. The collection box is fixed behind the conveyor. Fig.10: Fabrication of Rollers 16

6 Firstly, the width of the jaw can be enlarged to accommodate a larger crop yield. This can be done by increasing the number of jaws that are placed on the shaft. Larger frontal regions tend to have larger torques and hence power requirements are higher. This also increases the overall weight of the machine. Secondly, the mechanism of harvesting could be modified as per individual vegetable type. This mechanism involves either using front and rear movement of the jaws or alternating angle for harvesting. This requires the incorporation of a RC circuit to actuate the jaws. Also, the jaws needs to be designed for variable sizes. Fig.12: Assembly of the Harvester The jaws and the shaft are placed at the front portion of the frame. The motor is placed below the conveyor on the frame and it is connected with the rollers and the jaw shaft through a set of gears connected by chain. Thirdly, the length of the harvester could be reduced and the conveyor setup could be optimized. This could reduce the overall weight of the harvester and help increase the efficiency of the harvester. Finally, the power required to operate the harvester could be actuated by the motion of gears which are connected to the wheels of the harvester. REFERENCES VI. RESULTS AND DISCUSSION Results When the motor setup is started, the gear setup starts to rotate along with it. This gear setup actuates the rotation of the jaw shaft and the rotation of the rollers. This motor is setup to run at a controlled speed as per soil requirements. From the jaw shaft another set of gears transfer the motion to the roller setup. The jaws dig into the ground due to the rotation of the shaft. The assembled setup of jaw carries the harvest and throw it on to the conveyor. The conveyor is equipped with strips to hold the harvest. The harvest is carried by the conveyor and is deposited in the collection box. Under the collection box a vibrator setup is present. It vibrates the collection box and removes soil from the harvest. Thus the harvester effectively harvests the vegetables from under the ground. There is initial force required to dig into the soil and there is an initial time delay. After this the harvester harvests the vegetables from the ground. Scope for Future and Improvements [1] Abd-Rabou, A.F. (2004). Manufacturing a small machine to suit harvesting sugar beet under Egyptian conditions. PhD Thesis Agric. Mech. Dept. Fac. of Agric. Kafr El Sheikh. Tanta Univ. [2] El Sherief, R.R.A. (1996). A study on harvesting mechanization of sugar beet. PhD Thesis Agric. Mech. Dept. Fac. of Agric. Kafr El Sheikh. Tanta Univ. [3] Hall, T. L., Backer, L. F. and Hofman, V. L Sugar Beet Yield Monitoring for Site specific Farming Part II-Field Testing. Springer Science and Business Media B.V., 4 (4): [4] Mady, M. A. (2001). Mechanization of some operations for sugar beet Production. Misr. J. Agric. Eng., 18 (2): [5] Ozarslan, C; D. Erdogan and Y. Zeren (1990). Mechanization Possibilities on carrot harvesting, I. Cong. Mee. And Energy in Engr. Proc. of cont. held in Adana, Turky, The future improvements that are possible in the harvester are: 17

7 [6] PSG Design Data Book for Engineers, PSG College of Technology, Coimbatore. ISBN [7] Van Canneyt, T. and Verschoore, R Yield Measurements on a Potato Harvester. (00-PA-020) Agri. Eng., Warwick [8] Walter, J. D. and Backer, L. F Sugar Beet Yield Monitoring for Site-specific Farm-ing Part I. Laboratory Tests and Preliminary Field Tests. Springer Science and Business Media B. V.,4(4): [9] Walter, J. D., Backer, L. F., Hofman, V. L. and Scherer, T. F Sugar Beet Yield Monitoring for Site Specific Farming. ASAE Paper No , ASAE, St. Joseph, MI. [10] Wikipedia- Carrot Harvesters-Simon- Welcome 2012 en.wikipedia.org. 18