Design and Development of a Cutting and Lifting Mechanism for a Lemon Grass Harvester
By Low Kok Huan
A PROJECT REPORT SUBMITTED IN PARTIAL FULLFILMENT OF THE REQUIREMENT FOR THE DEGREE OF BACHELOR OF ENGINEERING (AGRICULTURAL AND BIOSYSTEMS)
FACULTY OF ENGINEERING UNVERSITI PUTRA MALAYSIA SERDANG, SELANGOR
MAY 2011
ABSTRACT
The design and development of a cutting and lifting mechanism for a lemon grass harvester are described. The experimental unit of harvester is fully tractor mounted to facilitate its maneuverability. However, there are several important factors affecting its performance. The harvesting operation is automatic because the harvester experimental unit have a pair of lagging cutter bar with horizontal wide V-shape of 150 degrees angle to break the soil layer of 10cm depth of ridge, thus its passive force driven lifting mechanism of lemon grass clump will act to facilitate that inclined movement of lemon grass clump upward with tractor speed to a roller conveyor which its speed is 1.5 times faster than that of tractor.
I
ABSTRAK
Rekabentuk dan pembangunan mekanisme pemotongan dan pengangkatan bagi sebuah penurai serai dijelaskan. Unit eksperimen bagi penurai dipasang sepenuhnya di traktor untuk memudahkan pergerakannya. Namun, ada beberapa faktor penting yang mempengaruhi prestasi. Operasi tuai dijalankan secara automatik kerana unit eksperimen bagi penuarai ini memiliki sepasang pisau pemotong dengan bentuk melintang lebar-V dari sudut 150 darjah untuk memecahkan lapisan tanah kedalaman 10cm ridge, seterusnya mekanisme pengangkatan pasif akan mendorong rumpun serai terangkat untuk memudahkan gerakan cenderung rumpun serai ke atas dengan kelajuan traktor ke conveyor roller yang kelajuan adalah 1.5 kali lebih cepat daripada traktor.
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ACKNOWLEDGEMENTS
I would like to thank my supervisor Dr Rimfiel for his interest and advices as well as En Zainal, En Anwar, and other technicians for their technical support and assistances. I appreciated the courage and actions supported from my precious faculty member, Kimmy Bong, Robin Liew and fellow course mates, KBP 07/08. Thank you.
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TABLE OF CONTENTS
Page ABSTRACT ABSTRAK ACKNOWLEDGEMENTS TABLE OF CONTENT LIST OF TABLES LIST OF FIGURES
I II III IV V VI
CHAPTER 1
INTRODUCTION
1
1.1 Objectives
2
LITERATURE REVIEW
3
2.1 2.2 2.3 2.4 2.5 2.6 2.7
3 4 5 6 6 8
2
2.8 3
4 5
Agronomy of lemon grass Production areas Harvesting Soil requirements Planting spacing Other root crop harvester Conceptual design of lemon grass harvester by Hafiz Cutter bar
9 12
METHODOLOGY 3.1 Introduction 3.2 Design requirements 3.3 Configuration option 3.4 Design concept 3.5 Blade for soil root cutting mechanism 3.6 Component for lifting mechanism 3.7 Conveyor 3.8 Design calculation 3.8.1 Draft force 3.8.2 Supporting leg 3.8.3 Radder bars 3.8.4 Roller conveyor 3.9 Laboratory testing
28 30 36 38 42
RESULTS AND DISCUSSION CONCLUSIONS REFERENCE APPENDICES
43 48 50 53
15 15 16 17 21 22 24 26
IV
LIST OF TABLES
Table 3.1
Page Description of sketches of concept design of lemon grass harvester
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3.2
The sketches show the variety of shape of cutting blade.
23
3.3
Length of radder bars which attached to a soil cutting blade
34
3.4
The related data of sprocket in chain transmission system (Pitch 12.7 mm)
41
V
LIST OF FIGURES Figure
Page
2.1
Planting spacing lemon grass.
7
2.2
Prepared lemon grass ready for marketing.
7
2.3
The width and height of a lemon grass clump.
10
2.4
Heterotypic harvester and mower blades.
13
2.5
Cutter bars.
14
3.0
Sketch of the experimental unit of lemon grass harvester
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3.1
Soil-root cutting blade and its radder bars.
25
3.2
Opening angle of cutting blade
25
3.3
Depth of a supporting leg during operation is carried out.
31
3.4
A supporting leg in cantilever condition.
31
3.5
Shear force and bending moment diagram for cantilever beam of a supporting leg.
32
3.6
Uniform load distribution is applied on the radder bars.
36
3.7
Shear force and bending moment diagram of radder bars system.
37
3.8
Sprocket system configuration.
38
VI
4.1
Front view of experimental unit of lemon grass harvester.
45
4.2
Right-hand side view of experimental unit of lemon grass harvester .
45
4.3
Left-hand side view of experimental unit of lemon grass harvester.
46
4.4
Back view of experimental unit of lemon grass harvester.
46
4.5
Top view of experimental unit of lemon grass harvester.
46
4.6
Connection between the frame and supporting leg.
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4.7
Cutting blades and its radder bars.
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4.8
Chain transmission system.
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VII
CHAPTER 1 INTRODUCTION
The Malaysian agriculture is dominated by cash crop plantation of oil palm trees and its related technologies were advanced mostly compared to that of other crops. However, local organic food industry especially organic herbal industry has grown up gradually in recent years. For instance, lemon grass also known as `Serai’ in its Malay name, it is a fragrant ever-green tropical grass with citrus lemon flavor. Lemon grasses are used in distilling processes for producing essential oil, namely, citronella oil which is a raw material in pharmaceutical purposes besides in domestic use for preparing Malaysian favorite citrus spices either in form of dried and powdered, or used fresh. With having intensive uses in daily life, wise consumers always demanded high quality and value-added agricultural product in large volume. Unfortunately, the most critical obstacle the organic herbal industry facing is mechanical transformation. Currently, there is no mechanization is used in lemon grass plantation either in planting or harvesting operation (Hafiz, 2008) except simple gardening tool. Furthermore, limited manual lemon grass harvesting capacity caused farmers suffered high labor cost per day (Hj Saudi bin Hj Hamid, 2008). Manual harvesting of entire plant clump, for example, chopping and pulling out the clump from ground require a lot great efforts and experiences. Other factor is shortage of labor in agricultural sector due to migration to urban area.
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Besides that, time consuming manual operation in lemon grass plantation will affect the commodity competence, in particular, in export market. "We will work with two French companies to market the products in France where demand for our oil extracts has grown by leaps and bounds," said by Malacca Biotechnology Corp's Chief Executive Officer Zam Abdul Karim. To satisfy high demands from essential oil processing industry, mechanical harvesting surely helps farmers increase their lemon grass harvesting production in aspect of saving harvesting time. However, there is no suitable lemon grass lifting machine except chop, hoe, and cutter such simple equipment. This project aims to design and develop a cutting and uplifting mechanism of tractor mounted lemon grass harvester with suitable root-cutting and lifting mechanisms for small scale production. 1.1 Objectives: The research objectives of this project were to: 1. Design and fabricate a suitable cutting blade for soil-root cutting mechanism 2. Design and fabricate a component for lifting mechanism 3. Investigate the ability of the completed cutting and lifting mechanism to respond to rotational inputs of the PTO connection.
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CHAPTER 2 LITERATURE REVIEW
2.1 Agronomy of lemon grass
The lemon grasses belong to the family Gramineae. Its scientific name is Cymbopogon marginatus and etc. The genus has about 55 species. Two major types have considerable relevance for commercial use: East Indian lemongrass, Cymbopogon flexuosus, which is also known as Cochin or Malabar grass, and is native to India and Sri Lanka. And West Indian lemongrass Cymbopogon citratus, which is native to southern India, Ceylon, Indonesia, and Malaysia. The lemon grass is a tropical perennial crop typically planted in rows. It requires average rainfall distribution of about 2,000-2,500 mm in a year. It grows well in range of mineral soil to peat soil and in altitude of 600-1,500 m. The ideal climate for growing lemon grass is tropical or subtropical climate. It is grown by propagation. Propagation is achieved by dividing the root clump. The plants grow in dense clumps up to 2 meters in diameter and have leaves up to 1 meter long. Hafiz (2008) presented useful information of plant’s physical dimension, root depth, planting row and hill spacing. This information was crucial in understanding of nature of plant and its planting considerations. Hafiz (2008) also provided the some basic operational cost per acre about lemon grass. Since no mechanical harvesting method is available locally, he described about
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local harvesting procedure of lemon grass while suggesting a conceptual design of lemon grass harvester to help increase farmer’s performance.
2.2 Production areas
Lemon grass is a herb identified for agriculture development and an important source of income with the East Coast Economic Region (ECER) states of Pahang, Terengganu, Kelantan and the district of Mersing, Johor. For example, BIO Daun Sdn Bhd is farming the lemon grass on 121 ha of land in both Kelantan and Pahang. (BIO Daun Plantation Sdn Bhd, 2008) Internationally, lemon grass is grown through Africa, in the Democratic Republic of the Congo (DRC), Angola, Gabon, Chad, Central African Republic, Madagascar and Comoros Islands. Guatemala is known to be the leading exporter with about 250 000 kg per year. China produces 80 000 to 100 000 kg per year. The United States of America (USA) and former Union of Soviet Socialist Republic (USSR) import approximately 70 000 kg per year each, the United Kingdom 65 000 kg, France and Japan 35 000 kg each, and West Germany around 20 000 kg per year. (Department of Agriculture, Forestry and Fisheries, Republic of South Africa, 2009)
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2.3 Harvesting
The harvest can take place from 6 to 9 months after planting the slips. The grass can then be harvested frequently during the active growing season, up to once every month. Frequent cutting stimulates growth. The oil yield will be reduced if the plant is allowed to grow to too large. The grass should be harvested early in the morning, provided it is not raining and allowing heavy dew to evaporate in order to avoid colour loss during a hot day. The plants are harvested mechanically or by hand. Cut the grass 10-15 cm above ground level. Avoid cutting too low as it will delay regrowth. Prevent splitting or cutting edges by using sharp tools and machinery that make clear cut. Oil quantity is optimal in the upper parts of the plant. Should the grass be cut too low, there will be less oil in the leaves. In South Africa, there are up to three harvests can be obtained in the first year and up to 5 to 10 harvests during each of the 3 to 5 succeeding years, depending on soil moisture status, management and weather. This is because the yield of oil is less during the first year of establishment and increase in the second year and reaches a maximum in the third and fourth years, after which it declines. For economical purpose, the plantation is maintained only for 6 years. (Department of Agriculture, Forestry and Fisheries, Republic of South Africa, 2009) In fact, Malaysian farmers adopt other farming and harvesting practices of lemon grass. The lemon grass is usually harvested twice a year (Hafiz, 2008). For this farming practice, farmers should harvest the grass by hand 10-15 cm above ground level when the grass matures. Six months later, a clear cut of the grass include its root should
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be removed by machinery and then be preparing for next planting season of lemon grass. The objectives of this project serve for the final harvesting of the grass mechanically.
2.4 Soil requirements
Lemon grass is widely adapted to a range of soils and performs well on sandy to clay loam soils with a PH range of 5.0 to 8.4 and good drainage. The lower the altitude and more alkaline the soil has, the higher is the citral content of the soil. Usually, the variety of soil with high citrates is in demand. For instance, drier and loamier soil yields higher citral content in lemon grass. (Department of Agriculture, Forestry and Fisheries, Republic of South Africa, 2009)
2.5 Planting spacing
Generally, a row spacing of 20 cm with a row width of 40 cm is used in, that will give a total of 125 000 plants per ha in a high rainfall area or under irrigation. Traditionally, the ridge is not required in plantation of lemon grass. However, a ridge of height of 10 cm should be used for soil-root cutting operation can be carried out easily. Also a range of row spacing of 140-200 cm should be used to accommodate the width of a tractor. These large spacing should be utilized to plant some short term vegetables such as eggplant, cabbage, and lettuce or intercropping with green beans as to provide the crop with nitrogen and assist in weed control before the lemon grass matures.
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Figure 2.1: Planting spacing lemon grass
Figure 2.2: Prepared lemon grass ready for marketing (Department of Agriculture, Forestry and Fisheries, Republic of South Africa, 2009)
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2.6 Other root crop harvester
Basically soil-breaking and uprooting mechanism were simultaneously applied by almost root crop harvesters. Although agronomy of lemon grass is quite different from other root crop, for instance, groundnut, onion, potato and other root crop types, but these two mechanisms were needed for harvesting of lemon grass. With modification and adaptation of each advantages of other root crop harvester over the countries, this lemon grass harvester prototype gain benefits during its design phase. From the literature review done by Hafiz (2008), there were many models of peanut harvester available over many countries besides potato harvester and onion harvester. The details about machine component and harvesting mechanisms of each harvester have been provided in his research paper, Conceptual Development of a Lemon Grass Harvester, 2008 p.18-25. An improved model of groundnut harvester (1988) developed by Univesiti Putra Malaysia (UPM) and its harvesting concept are referred intensively by this project. The design of this model is rather machinability in nature and its functionality in harvesting is quite good and high in efficiency.
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2.7 Conceptual design of lemon grass harvester by Hafiz (2008)
Conceptual model of development of lemon grass harvester suggested by Hafiz (2008) is mainly consists of leaves cutter, subsurface rotary finger reel, conveyor, and other components. Hafiz explained in his paper that a leaves cutting operation is carried out first before lifting process of lemon grass. The reason for cutting the leaves is facilitate the operation later. Most importantly, the principle of his lifting process of subsurface rotary finger reel is as follows: the teeth of subsurface rotary finger reel will break up the soil structure which it is in turn automatically push clumps of lemon grass from the bottom to the lifting system. Hafiz also claimed that there are several important points for his system will push and convey the clumps rather than using the root cutting method while the whole subsurface rotary finger reel is submerged below the ground. The size (diameter, width, and type) of subsurface rotary finger reel must be as small as possible for minimizing the contact area between soil and subsurface rotary finger reel, thus it will reduce power requirement. Besides that, nearly zero drawbar power requirement is needed because the rotor tends to move the machine forward as it works.
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With reference to his research data of parameter of a clump of lemon grass: Parameter of lemon grass(Hafiz, 2008)
Figure 2.3: The width and height of a lemon grass clump Average root depth = 7.2 cm Weight = 9kg The crop is an aromatic plant whose roots are fibrous shallow and spread into the soil, has long leaves. The essential parts of the lemon grass are stalks and leaves. The essential oil is extracted from fresh plant material by means of steam distillation. There are several technical problems arisen from his design. As stated in his paper, the coverage of maximum depth below the ground, which is 12 cm, by his subsurface rotary finger reel since the reel is working below ground. The design depth exceeds the average root depth of 7.2cm so that the root system of plant will be removed. Although the teeth may be sufficiently capable to break up the soil surface, but he did not describe the way subsurface rotary finger reel will get into the depth of 12 cm below ground especially the soil is initially firm. The case will be different if there is either a ridge there or high moisture content of soil. 10
Secondly, the length of shaft of subsurface rotary finger reel is too long, which is 82 cm compared to that of the required dimension that is average clump diameter of 60 cm. The reel may face more soil resistance below the ground with its excess length of the reel is about 22 cm. The suggested tolerance range of length should less than 5cm. Furthermore, the design torque is also too small which is 577 Nm with 375 rpm and safety factor of 1.2 to carry out the clump pushing work. As a result, the shaft of reel which its dimension of 4 cm may either face reduction of revolution or varying deflection of subsurface rotary finger reel below the ground due to imbalance loading of clump and soil clods during the soil breaking and clump lifting processes. Further modification is required to secure the change of deflection of shaft. The working conditions under the soil surface will also affect the performance of transmission system of chain for subsurface rotary finger reel. Although Hafiz suggested a modification which is add-on of sharp metal on chain thus will help break up the soil structure while the system of reel is rotating below the ground. But the transmission system especially the sprocket may become either rusted or defected in a shorter period compared to that of normal use under lubrication condition. The problem of falling apart of clump may exist after lifting process. In his design, the subsurface rotary finger reel has four part surface and each surface has twenty teeth. This feature may help griping the clump as well as breaking up the soil structure. But the base structure of clump may become loosen due to partial support of reel of 13 cm width, thus it is falling apart during the stage from subsurface rotary finger reel to conveyor. In addition to that, the gap between reel and belt conveyor remained undefined. If the conveyor is too close to the surface of ground, the scattered 11
soil particles may affect the efficiency of power transmission of conveyor. Also, the ambiguous part is unclear dimensions of sprocket. Other problems rose, which have been stated in his paper, when using a hydraulic motor to run the reel. Besides that, there are insufficient skills and tool to fulfill the requirements of complex construction of curved shape of subsurface rotary finger reel holder except special machining is ordered. As a result, a lemon grass harvester of simpler machinability should be designed as to save cost and material.
2.8 Cutter bar
Harvest loss consists of agricultural produce that is produced but not successfully removed from the field. There are several major categories of loss: preharvest loss, gathering unit loss, and machine loss. In the agricultural sector, the harvest loss of grain, for example soybean, is severe. Poor field conditions and a poorly adjusted combine may contribute to harvest loss of 6-8 bushels of soybeans per acre. Harvesting losses cannot be completely eliminated, but they can be reduced to only 1-2 bushels per acre if the performance of the combine is maintained regularly. (Cooperative Extension Service, Lowa State University, 1984). The cutter bar is the major cause of field harvesting loss, accounting for about 80% of combine header harvesting loss of soybean ( Quick, 1973; Dunn et al., 1973). Research results by Dunn et al.(1973) on soybean asserted that harvesting loss were caused by the cutter bar and about 61% of the field loss was due to shatter. Nave and Hoag(1975) investigated 12
different cutter bar and knife configurations mainly sickle and knife frequencies in a laboratory test stand. Their results showed that knife section and guard spacing of less than the conventional 76.2 mm would reduce plant stem acceleration and result in shatter loss. Although physiology of lemon grass is different from that of soybean, farmers will suffer the harvest loss in a way of crop damage and finally abandon the crop if the cutter bar is not designed specially. Traditionally, the available literature review are focused on vertical blade on the soil tillage or cutter bar cutting plant stem but there a few review about horizontal cutter bar cutting soil structure and root system especially closely related to harvesting of herb. Despite that, modified reasoning of machine design has been applied on the harvesting of lemon grass, which may help improve the harvesting efficiency of lemon grass. And a future research work on efficiency of different cutter bar configuration on harvesting lemon grass is suggested to determine the optimum performance. The figures below display different kind of harvester cutter bar in terms of shape and application. These cutter bars are mainly used for grain harvesting, for example, soybean, maize, and other besides grass mowing.
Figure 2.4: Heterotypic harvester, sickle guard, and mower blades. 13
Figure 2.5: Cutter bars Material:High quality 65Mn spring steel Thickness: 2.00mm; 2.80mm Surface Treatment: Only with anti-rust oil after quenching; varnish stoving; paint oil stoving; galvanized; blueing; chromeplate, etc. Main Application: Harvester blade (knife sections & ledger blade) are used in harvesting machines like combine harvesters (New Holland, John Deere, Swaraj etc.), straw reapers, mowers and hreshing machines, etc.
[Source: 1. WINDSOR agricultural implements and spare parts 2. www.grandeermachine.com 3. www.topmachinebiz.com ]
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CHAPTER 3 METHODOLOGY
3.1 Introduction
After the initial research steps were taken, the actual mechanism design development of each component of the harvester took place. The machine is designed to assist farmer without consuming much time and human power during lemon grass harvesting operation. The process began with brainstorming process of various concepts that had potential to form the functional requirement of each component. However, there are a lot of constraints in designing such a machine. The machine was designed basically based on various parameter and constraints i)
Basic parameter of a lemon grass clump(height, width, and weight)
ii)
Root depth
iii)
Row and hill spacing
and other important considerations.
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3.2 Design requirements
The machine will be designed so that farmers able to afford to buy it at reasonable price and help farmers increase their harvesting efficiency during harvesting operation. The desired features were displayed in list below: •
Tractor mounted
•
Able to break up soil layer and cut off lemon grass root
•
Lifting the lemon grass clump to conveyor
•
Reduce physical damages to lemongrass bunches
•
Feasibility in manufacturing process and material selection
•
One row harvesting
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3.3 Configuration option
The preliminary design of cutting blade, lifting tool, and conveyor is selected from various sources include reference from technical book, the agricultural product catalog available in market, and brainstorming processes. However, the design of the machine is evolving through the real construction practices as to achieve feasibility in manufacturing process. There are three option of initial model of the implement that have its own characteristic and disadvantages. Option A will use big vertical and triangular blade to cut the root and slide the clump by its body.
The principle of the operation may be sound good, but its
supporting leg may not able to support the weight of blade of solid mass and pull force from tractor while penetrating through the soil. Second, the cost factor is a very important consideration in designing the machine. Since this type of blade may require special machining, thus causing unexpectedly high cost to the project budget although the machining of blade may able to cast various shape of cutting edge efficiently. Option B will use a horizontal square blade to cut the root and slide the clump afterward through its finger extensions. This configuration may be able to contribute a lighter weight compared to that of option A since the blade is responsible for cutting function solely. The blade must have sharp and smaller cutting area to cut the root efficiently. The assistance of its finger may also help reduce the weight but this structure may not able to last long with its inclined angle. 17
Option C will use a long inclined V shape blade. The structure may be rigid enough as to lift the clump and can be designed lighter so that the several supporting leg able to support the long blade. However, the blade may convey a lot of soil mass together with lemon grass clump during the tractor is moving. Table 3.1: Description of sketches of concept design of lemon grass harvester Concept A
A big vertical and triangular blade, which its width are about 600 mm and thickness of more than 100mm , will be used to cut the root of lemon grass underground and simultaneously slide the clump up onto the conveyor while the tractor is moving forward.
Concept B
A horizontal square blade, which its dimensions of 600 x 30 x 10mm , will be used to cut the root underground , then the clump will slide onto the finger which attached to the blade , thus drop onto the conveyor while the tractor is moving forward.
Concept C
A long inclined V shape blade, which its sub ground cutting edge will cut the root. After that, the clump will slide onto its body and then onto the conveyor.
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From the sketches above, the component of blade is the determining factor in these configuration options because the blade design is affected by its shape, opening angle, and other dimensions which are interdependent, thus affecting the lifting mechanism. So the selection of suitable blade design should be carefully chosen as to contribute to easy machinability in next step. The machine is desired as to cut off the root system of the grass and then should be able to lift the clump onto a conveyor. Since the blade will operate beneath 10cm depth the ridge, the blade is subjected to the threat of being blunt after operating. A convenience of replaceability of the blade should be included in the machine feature so that the efficiency of cutting has been maintained during the operation. Also, the support leg of the blade faces the threat of distortion during the operation. As a result, these two components should be designed properly at low cost and have a feature of replaceability. Besides that, an lifting mechanism should be designed so that a clump will be lifted just after the cutting mechanism. In short, a good machine should be properly included these features. There are three options of combining the root cutting mechanism and lifting mechanism together. First, an option of triangular blade of 60 cm x 30 cm x 10 cm (length x width x thickness) which requires a special machining as to able to cut off the root and able to slide passively the clump of lemon grass through its body. This big structure may require slightly high cost of material and machining as well as cause soil loss during operation. Also, the fabrication of a long inclined V-shape blade also faces the same problems besides a special connection between support leg and the blade need to be designed so that the V-shape inclined blade is hung up as to lift the clump. The triangular blade and incline V-shape blade expose their body to the soil as to slide the
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clump onto the conveyor meanwhile they also cause soil resistance between the body and the clump. The larger the exposed surface area of blade beneath the soil, the higher the resistance the blade will face. As a result, these two option of blade should avoided as to reduce cost, machinabilty, material usage, and soil resistance. In relation to these reasons, the option of horizontal square blade can be arranged in a way such that it has a V-shape opening as to minimize the soil resistance meanwhile it will cause lesser soil loss when its radder bars slide passively the clump up. This is because the gaps between the radder bars allow the excessive loose soil particles drop down to ground as well as to minimize the contact area between the circular radder bars and clump. Although the radder bars may be easily broken but a stronger strength of material can be selected to support the mass of above 9 kg. This option is a material saver compared to that of other two options because it need mild steel of dimension of 60 cm x 8 cm x 2 cm ( length x width x thickness) and about 10 pieces of iron bars of length 40 cm. The choices of the conveyor can be varied according the requirements of farm conditions. A roller conveyor will be preferred because its motion is synchronous and running without slack. In sum, the feasible concept is concept B.
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3.4 Design concept The experimental unit of lemon grass harvester has five crucial parts inclusive roller conveyor, a pair of V-shape cutting blade with radder bars, frame, wheel, and power transmission system. Frame functions as overall physical machine supporter; most interesting part is that the existing support structure of gearbox and the three point hitch linkage are incorporated inside frame structure as back bone. After the tractor, a pair of submerged lagging cutting blade with horizontal wide V-shape of 150 degrees angle will break up the soil layer about depth of 10 cm beneath soil surface, thus separating the root system and soil apart. As the motion of tractor and its lemon grass harvester are running, the combined structure of cutting blade and its radder bars is pulled actively by tractor. The exposed root system will slide passively onto the surface of radder bars after the soilroot cutting process. In sequences, the lemon grass clump will be lifted up by angle of 30 degrees but the gravity force acts on the clump so that the clump thus drops onto roller conveyor nearby. However, irregular sharp metal strip are welded on the surface of roller conveyor as to help lifting the clump onto conveyor. A sketch of the experimental unit of the lemon grass harvester is as shown in Appendices, page 53.
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3.5 Blade for soil root cutting mechanism
There are four sketches of different type of cutting blade have been produced after considering the current machine requirement and agronomy of lemon grass. The blades have been visualized and compared their advantages and disadvantages as below according to design criteria especially its machinability. These four types of blade connected with its radder bars which are desired to lift the clump onto conveyor after cutting off the root of the grass. To facilitate the feasibility of blade design, its advantages and disadvantages from each blade design should be compared as to produce a desired cutting performance. The triangular blade is usually used in grain harvesting because it cut the stem effectively in air by its concentrated cutting force in centre. However, its knife head will be blunt in a shorter time compared to that of operating in air since the blade is expected to operating in soil. The second option is the horizontal blade which requires simple machinability , but it faces high soil resistance when it is operating in soil. As a result, a modification should be applied on horizontal blade as to reduce the soil resistance, thus introducing two different opening angles of V- shape blade of 45o and 75o which will face reduced soil resistance when they are operating in the soil. However, the V- shape blade of angle 75o will be selected since this design will save the material usage by its larger length coverage as compared to that of V- shape blade of angle 45o. In sum, a proper selection of blade should stick to the project objective and design requirements. The feasible design of blade is design D. 22
Table 3.2: The sketches show the variety of shape of cutting blade. Advantage Design A: Horizontal triangular blade
-Concentrated cutting force in centre
Disadvantage -Easy blunt knife head. -Not suitable in cutting soil.
Design B: long and horizontal square - Simple machinability blade
-High soil resistance
Design C: V-shape blade with angle of -Reduced soil resistance 45o (Hassan bin Osman, 1988).
-Increased machinability
Design D: V-shape blade with angle of -Reduced soil resistance 75o -Material saver(larger length coverage)
-Increased machinability
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3.6 Component for lifting mechanism
The radder bar functions to lift the lemon grass clump passively while the clump slide onto it.( Hassan bin Osman,1988) There are several considerations should be taken care of when designing the dimension of radder bars as to maximize the performance of lifting mechanism. The shape of radder bars should be cylindrical as to minimize the contact friction between clump and surface of radder bars. Although there is a gap between each radder bar, the clump may occupy the gap down. But, clump may not easily fall apart since it is come in clustered mass with its fibrous root system. Second, the speed of tractor is operating above 2km/h and the length of radder bar is designed to be less than 400mm.
Velocity =
Time =
Displacement Time
0 .4 0.5556
= 0.72 sec
The short reaction time is required that lemon grass slides onto conveyor after the cutting of its root. Thus, the clump should be transferred to conveyor before sufficient time is allowed for the clump to become fallen apart. The angle of inclination, Ө of radder bars should equal or less to 45o as to avoid incapability of sliding up of clump which will create a clump blockage on the radder bars and affect the lifting mechanism of next lemon grass clump. Meanwhile its angle of inclination should create an elevated height of more than 13 cm because this elevated 24
height will not only lift the clump but will also avoid the conveyor from suffering the damage during the machine is working close to the ground. The strength of radder bars is crucial in determining the ability resisting the maximum weight of lemon grass of 9 kg as stated in Hafiz‘s report besides unknown conveyed soil mass. Since the project aims to build a component of a cutting and lifting mechanism of the lemon grass harvester, the mild steel should serve its purpose during the experiment as to save project cost.
Figure 3.1: Soil-root cutting blade and its radder bars
Figure 3.2: Opening angle of cutting blade. 25
3.7 Conveyor
The machine is working close to soil surface thus may cause the machine subject to threat of damage during its working operation. Careful dealing with various constraints is required to fulfill the project objectives. Since the elevated height of fingers is around 13-16 cm and the consideration of thickness of frame, there are several options for selecting suitable conveyors: belt conveyor, chain conveyor, and roller conveyor for conveying operation Although belt conveyor is commonly used in industry, its slippage in transmission may not suitable in this case for conveying the lemon grass clump during the operation is running. This is because next clump will be cut in next minute after previous cutting of lemon grass root. If there are blockage occurs in conveyor due to decreased conveying efficiency, it will affect the next clump conveying and slow down the operation. Chain conveyor may be suitable for this experiment. Chain conveyor have the advantage of lighter weight, low vibration effect, and synchronized motion as to ensure smooth conveying operation, but large diameter of sprockets are required to transmit power to support weight of clump. Besides that it may not be suitable to support the weight of lemon grass clump especially in inclined direction while its sprockets close to soil surface. It may require high cost of industrial chain for transporting the clump of maximum 9 kg.
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The application of roller conveyor has its advantages similar to that of chain conveyor, but it has at least three separate rollers with smaller size of sprocket. It is also costly and high maintenance as compared to that of belt type. Although the roller conveyor also faces the threat of damage while working close to soil surface, it can be replaceable either by parts or by whole small system. It is suggested that a small roller conveyor can used after the lemon grass uplifting process by fingers, thus the clump will be passed to other larger conveyor system either of roller conveyor or chain conveyor for future research work. By comparison, the roller conveyor is selected for serving the project objectives. By combining the selected component, the functional requirement of cutting, uplifting, and primary conveying mechanism of lemon grass will be fulfilled by using Concept B with Design D: a pair of V-shape blade with angle of 75o each and roller conveyor system.
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3.8 Design calculation 3.8.1 Draft force
To pull an implement at a given speed in the field, the total amount of draft, which is the draft force required to pull a complete implement in the field , must be known. The unit draft is the draft force required to pull some unit of the tool. Total draft is therefore the sum of the unit draft. Total draft consists of draft force of cutting blade, draft force required to pull the rest of component of lemon grass harvester (gearbox, frame, and roller conveyor). To calculate the draft force of soil cutting blade, the following factor must be considered: a. Width of the tool b. Depth of cutting c. Ground speed d. Soil resistance Soil resistance is based on texture, but may vary widely within a textural class depending on characteristic such as looseness (i.e. density), moisture content, and subtle changes in particle size distribution. Generally, a moist sandy loam soil would have about 6.4 pounds of resistance per square inch or 44 kPa(Technical note 21.Soil, draft, and traction; Dirt Hog’s companion). However, shear stress of sandy loam available in Taman Pertanian 28
Universiti(TPU) is 1.22 pounds of resistance per square inch or 8.42 kPa at a soil moisture content of 20.74 %( Boon, 2005). A dry sandy loam would have a much greater draft, and therefore require more power to cut through the soil, than a moist sandy soil loam. However, there is high humidity in soil of Malaysia due to its tropical climate with shinny and rainy day contributes to different moisture content of soil throughout the year. Consider a 45 cm cutting blade penetrate 10 cm deep of a ridge has a 450 square centimeter cross section area (width of tool x depth) operating at a speed of 3.2 km/hrs. A moist sandy loam soil would have about 6.4 pounds of resistance per square inch or 44 kPa will be taken as reference in this calculation. Data: Width, w=45 cm= 1.47 ft Depth, h= 10cm = 0.328 ft Area, A= 450 cm2 = 0.482 ft2 Speed = 3.2 km/hrs = 1.988 mph Shear strength of moist sandy loam soil, б = 6.4 pounds of resistance per square inch Unit draft = w x h x б
(Dirt Hog’s Companion. Technical Note 21)
Unit draft of two cutting blade = 6.4 x 0.482 x2 = 6.17 lb of resistance Draft force required to pull the rest of component of lemon grass harvester (gearbox, frame, and roller conveyor) is estimated about 30kg or 66.138 pound and 29
maximum mass of 2 lemon grass clump of 18 kg or 39.68 pound on the harvester during the operation. Total draft = 6.17 + 66.138 + 39.68 = 111.98 pound
3.8.2 Supporting leg
The figure below illustrates a supporting leg of length 70cm which is connected to a V shape blade and the frame by screw. Although the height of a lemon grass plant may reach up to 120 cm( Hafiz, 2008), but the length of supporting leg has been reduced to 70cm due to the constraint of PTO height of tractor.
However, this
constraint will not damage the quality of lemon grass as its stalk contains high yield of oil content than that of its leaves and the useless leaves will be discarded. Also, this supporting leg is subject to high resistance and moment during operation when its length is too long, thus this supporting leg should be designed as to resist the opposing resistance. As a result, the supporting leg can be replaceable easily if there is any failure occurs and the effective length of supporting leg has been reduced to 61cm where measurement starts from position of screw to the blade.
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Figure 3.3: Depth of a supporting leg during operation is carried out
Figure 3.4: A supporting leg in cantilever condition.
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Figure 3.5: Shear force and bending moment diagram for cantilever beam of a supporting leg
The joint is assumed to be fixed as to able to resist moment. The pattern of resistance is estimated as triangular which influence of resistance increases with the increasing length beneath the soil. The value of parameters is given as below: Diameter, D = 1 in = 2.54 cm Working length, L = 61 cm h/3 = 10/3 cm L-h/3 = 57.67 cm Unit draft = w x h x б = 1986 N 32
Moment, M = unit draft x (L-h/3) = 114.554 kNm Rx= 0 Ry= 1986 N
Second moment of area of supporting leg, I =
πr 4 4
; r = radius
= 2.04 x10-8 m4
Center distance = D/2 = 0.0127 m
Bending stress, б = ±
= ±
Mc I
(Marshek, K. M., 1987)
114.554 x 0.0127 2.04 x10 −8
= ± 71.32 M Pa Circular area, Ac = πr2 = 5.067 x 10-4 m2 Shear stress, τmax =
=
4V 3 Ac
(Budynas, R. G, 2008)
4 x1986 3 x5.067 x10 − 4
= 5.225 MPa
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Take factor of safety =2 Yield strength, sy = 2б =142.64 MPa
Material selection: 1018 mild steel Ultimate tensile strength =63,800 psi = 439MPa Yield strength
=53,700psi= 370MPa
Elongation
=15%
Rockwell hardness
=B71
Modulus of Elasticity
= 200 GPa
Deflection at the unsupported end =
=
(Eagle national steel, 2009) PL3 3EI 1986 x(61x10 −2 ) 3 3 x(200 x10 9 ) x(2.04 x10 −8 )
= 0.0368 m Although the calculated yield value of 142.64 MPa of the supporting leg is lower than that of 1018 mild steel, which is 370 MPa. But the supporting leg is stretched under force without failure by the value of theoretical deflection which is 3.68 cm when it is assumed operating under the soil. The longer the length the cantilever
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beam, the larger the deflection it is. Since the length of supporting leg is constrained by the height of lemon grass and position of power takeoff of tractor, the length of 61 cm is the minimum requirement. From the calculations, the length of supporting leg which is 61 cm is going to be distorted and need to be replaced after operations. To reduce the deflection, a stronger material of higher modulus of elasticity and larger diameter should be used as the supporting leg by assumed its length and the load distribution is as indicated as above.
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3.8.3
Radder bars
Consider a cutting blade having 6 radder bars of diameter, D of 1cm each and its distance from centre to centre of the radder bars is 5cm. The inclined angle of 30o of radder bars was taken as to lift the grass up. As a result, there are a total number of radder bars of 12 for a pair of cutting blade and the maximum estimated height of radder bar from soil surface, h is 25.45 cm which is the lifted elevation for the position of roller conveyor installation. The design of radder bar help lifting the grass up from the ground and avoid the roller conveyor suffering the damage during the operation where is closer to the ground. The table below showing the lengths of radder bar which installed on the other edge of the cutting blade opposite to that of sharp cutting blade. Table 3.3: Length of radder bars which attached to a soil cutting blade Radder bars A B C D E F
Length (cm) 36 37 39 40 41 43
Figure 3.6: Uniform load distribution is applied on the radder bars.
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Figure 3.7: Shear force and bending moment diagram of radder bars system.
Assume the length of longest radder bar is 43 cm Rx = 0 N Ry = 63.3 N Moment, M is 13.6095 Nm at the end of support Since the maximum moment will be shared by at least 10 radder bars if in case of smaller diameter of clump. The moment is increasing as the length of radder bar is increasing. By considering the longest length of radder bar, average moment of each radder bar is 1.36 Nm at the end of support. Despite of that, the whole radder bar system should be able to resist this bending moment in a short reaction time of 0.72 second when the clump is sliding on the surface of radder bars. 37
3.8.4 Roller conveyor
Figure 3.8: Sprocket system configuration
The sprocket system configuration above illustrates the position of roller conveyor and its related components. The system is a part of lifting mechanism of lemon grass with its power source from power take-off (PTO) of tractor. First, the PTO shaft of a tractor will transmit the power to gearbox, and then the speed reducer gearbox will reduce the rotational speed. However, the sprocket system is designed to increase 38
the rotational speed thereby increase the forward speed of roller conveyor. As a results, the following steps was carried out to determine the suitable dimension of the sprocket A, B, and C as to increase the forward speed of roller which is 1.5 times faster than that of the tractor of assumed operating forward speed 3.2 km/h. This forward speed of roller conveyor is required to transfer the clump of the grass faster to the next stage of conveying mechanism before any blockage occur during the lifting mechanism. From the data available: Power take-off (PTO) speed = 540 rpm with engine at 2199 rpm. Speed ratio of reducer gearbox = 2:1
N PTO Speed ratio = Ng
Speed of shaft after reducer gearbox, Ng=
540 = 270 rpm 2
Since sprocket C is on the same shaft as above, >>speed of sprocket C, NC = 270 rpm The sprockets are keyed on the shaft to transmit the power except sprocket C is splined on the shaft to receive 270 rpm from reducer gearbox. Tractor is assumed operating optimum on the speed of 3.2 km/h = 8/9 ms-1 when the harvesting operation of lemon grass is running. Given that diameter of roller, D= 2 inch = 5.08cm
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The factor 1.5x was taken into account as shown in the following calculations. Conveyor speed = 1.5 x (8/9) ms-1 = 4/3 ms-1 For simplicity, assume the entire sprocket A system is of the same dimension on the shaft of roller conveyor. Since the sprocket A system is located closer to edge of conveyor, so smaller size of sprocket of 57.07 mm pitch diameter is selected as to minimize the contact between lemon grass clump and sprocket A. V= r Ѡ 2πN = r ( 60 )
4/3= (
5.08 x10 −2 2πN )( ) 2 60
>> Speed of sprocket A system, NA = 501.28 rpm Speed of sprocket B is similar to that sprocket 1 since they are on the same shaft. NB = 501.28 rpm Because there constraint of longer shaft which sprocket C is splined onto, one of the shaft of system sprocket is designed to be 125 cm long where sprocket B is keyed as to match sprocket B and sprocket C in line to power transmission. Diameter sprocket C of 137.64mm is selected.
Nc D = B NB DC
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DB 270 = 501.28 137.64 DB= 74.13 mm As a result, a sprocket of closer diameter of 73.14 mm is selected. N C DB = NB DC
270 73.14 = NB 137.64 NB= 508.1 rpm The steps above are recalculated as get a new speed of sprocket B which is 508.1 rpm. V= r Ѡ 2πN =r( ) 60
V= (
5.08 x10 −2 2π (508.1) )( ) = 1.35 m/s 2 60
Then, the forward speed of conveyor, V is 1.35 m/s After detailed calculations, the table below summaries all the related dimension of sprockets will be used in the roller conveyor system. Table 3.4: The related data of sprocket in chain transmission system (Pitch 12.7 mm) Sprocket 1 2 3
Pitch diameter, D( mm) 57.07 73.14 137.64
Number of teeth Revolution(rpm) 14 18 34
508.1 508.1 270 41
3.9 Laboratory testing
The machine was tested in the laboratory to identify its weakness and find any improvement to correct its problems after its fabrication of machine. The aim of laboratory testing is ensure the machine achieves the project objectives. However, there is no field test was carried out due to technical problems. The laboratory testing includes testing on chain transmission, visual inspections of machine and position of blade after installation as well as measurement of mismatched gaps due to construction errors. As a result, a field testing should be carried out after the problems have been tackled first in next project.
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CHAPTER 4
RESULTS AND DISCUSSION
The experimental unit of lemon grass harvester have been inspected after it assembly. Since there are limited time constraint, initial laboratory testing can be done up to this stage.
Result of laboratory inspection/testing as below: 1. The blades are screwed well in position after modification. However, there are some alignments of supporting leg when it was screwed onto frame due to clearance inside the cylinder. Although like this, the supporting leg able pulls the blade beneath the ridge when mounted to tractor but also support the gearbox when the harvester detached from three points hitch linkage. One point to be emphasized here is there in no lemon grass planted in laboratory ridge and the ridge is artificially soft. 2. The length of radder bar has been underestimated due to a gap distance of 5cm because construction error in forming the angle of radder bars and extra height of wheel. Some bridging metal of 2 x 2 cm have been welded on surface of roller conveyors as to griping the root of clump from the end of radder bars. Although there are about 3 cm of uncovered gap between radder bars and roller conveyor, the bottom of cross section of clump is 60cm, which is larger than the gap, should be pass onto conveyor with assistance of bridging metals. The
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bridging metal of 2 x 2cm is a very thin metal of about thickness of 0.4cm and its material is mild steel of 200GPa. 3. The slack of chain tension affects efficiency of the chain drive transmission during the conveying mechanism, thus the forward speed of roller conveyed have been reduced. A suggestion of installation of tensioner should be adopted as to avoid the reduction of forward speed of conveyor. The proper adjustment of the speed of tractor and the rods of all conveyors beyond the cutting blade and its fingers are covered with rubber or plastic to reduce damage of crop and efficiency of transmission system in the primary conveying operation. ( Kepner,R.A.,1972) 4. The third shaft of roller conveyor is too long where there is a one unsupportedend cantilever of 25cm from bearing and a sprocket of pitch diameter 73.14mm in its end. This design of third shaft of roller conveyor is unavoidable because there is no modification being allowed on the length of transmission shaft of gear box. The deflection of third shaft of the conveyor is visible. 5. The roller wheel is improperly selected to be installed in this experimental unit
of lemon grass harvester. The main reason for this error is insufficient experience in selecting suitable wheel for agricultural uses. A agricultural tire of proper size should be selected as to support the weight of machine and to reduce pressure on surface of ground during operation especially in a soft or muddy farm land. 6. Wrong selection of hollow square mild steel as part of frame which cause the screwed area are dented by pressure of screw.
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Figure 4.1: Front view of experimental unit of lemon grass harvester
Figure 4.2: Right-hand side view of experimental unit of lemon grass harvester
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Figure 4.3: Left-hand side view of experimental unit of lemon grass harvester
Figure 4.4: Back view of experimental unit of lemon grass harvester
Figure 4.5 Top view of experimental unit of lemon grass harvester
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Figure 4.6: Connection between the frame and supporting leg
Figure 4.7: Cutting blades and its radder bars
Figure 4.8: Chain transmission system
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CHAPTER 5 CONCLUSIONS
This report includes two main phases: the planning of machine design and hardware fabrication. The first phase, the planning of machine design involves defining project scope and brainstorming for preparing a new machine design of components of cutting and lifting mechanism of a lemon grass harvester which its purpose serves for small scale production. There are demonstrations of many basic mechanical principle and ideas in designing the functionality of the machine which consists of three main parts: lifting mechanism, root cutting mechanism, and chain power transmission. These three parts are all written into a header file, so that the related theoretical calculations able to display the logical technical information about the machine. The design of lifting mechanism is most interesting, since there are many obstacles such as simultaneous motion of soil breaking up and lifting mechanism as well as meeting the set up and hold times. The interaction of several simple mechanical parts which are a pair of wide V shape cutting blades, radder bars, and roller conveyor are making up the critical part of the machine. The wide V-shape cutting blades break up the soil and accommodate the lemon grass clump instantly while reducing the soil friction resistance. Since all the components of the machine are in continuous motion, the clump will immediately be conveyed to roller conveyor by inclined radder bars as a gap bridging.
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The second phase, hardware fabrication involves implementing and revising the plan. The project requires proper considerations of material cost and physical construction of the work packages of the machine besides good coordination in arranging the material, machines, tools, time, and manual labor. The processes, in general, include geometry matching and joining of multiple parts to make an assembled machine. The work packages are carried out as a sequence of operation, which are accomplished by a combination of machines, tools, power, and manual labor. In sum, the project objectives were completed and the weaknesses of this experimental unit of lemon grass were identified as in chapter 4.
There are a number of future extensions that may be done on this project. They are as follow: A. Design of chain conveyor extension and its storage bin B. Design a cover for chain drive transmission C. Redesign a new stronger frame and suitable chain drive transmission system for supporting roller conveyor and chain conveyor. D. Select suitable agricultural tires and design its power transmission system. E. Suggesting a new planting spacing of lemon grass for a better harvesting performance.
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REFERENCE
1. BIO Daun Plantation Sdn Bhd, (7 october 2008) http://www.mfa.org.my/?franchise-news:bio-daun-offers-lemongrassfranchise-opportunities:20K098F515,
2. Boon N.E.; Yahya A.; Kheiralla A.F.; Wee B.S.; Gew S.K. ( 2005) A Tractor–mounted, Automated Soil Penetrometer-shearometer Unit for Mapping Soil Mechanics Properties. Universiti Putra Malaysia. 3. Budynas, R. G.; Nisbett, J. K., (2008) Shigley’s Mechanical Engineering Design , Eigth Edition, McGraw-Hill. 4. Dirt Hog’s Companion. Technical Note 21.Soil, Draft, and Traction. (5/3/2011) www.soil.ncsu.edu/upen_furrow/Documents/DHK/soi,%20Draft,%20and%20Tr action.pdf
5. Dunn, W.R., Nave, W.R and Butler,B.J. (1973) Combine header component losses in soybean. Trans ASAE16(6): 1032-1035 6. Essential oil crops: production guidelines for lemon grass http://www.daff.gov.za/docs/Brochures/EssOilsLemongrass.pdf
Department of Agriculture, Forestry and Fisheries, Republic of South Africa, 2009 7. Hafiz bin Hazir(2008). Conceptual Development of A Lemon Grass Harvester, final year student project, Universiti Putra Malaysia.
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8. Hassan bin Osman(1988). Pembangunan Jentuai Kacang Tanah, final year student project, Universiti Putra Malaysia 9. Hj Sauadi bin Hj Hamid (30/10/10; 22:29) http://jasabumiagrofarm.blogspot.com/2008_10_01_archive.html
10. Eagle national steel(2009) http://www.eaglesteel.com/download/techdocs/Carbon_Steel_Grades.pdf
11. http://www.grandeermachine.com/search.html?g=398449 (3/3/2011) 12. http://www.topmachinebiz.com/product/484405/Harvester-Blade.htm (3/3/2011) 13. Kepner, R.A.; Bainer R.; Barger E.L. (1972), Principles of Farm Machinery, Second Edition, The Avi Publishing Company,Inc. 14. Marshek, K. M., (1987) ,Design of Machine and Structural Parts, John Wiley& Sons, New York,. 15. Nave,W.R. and Hoag, D.L. 1975. Relationship of sickle guard spacing and sickle frequency to soybean shatter loss. Trans ASAE 18(4): 630-632,637 16. Profitable soybean harvesting, 1984 http://extension.agron.iastate.edu/soybean/documents/PM573.pdf
Cooperative extension service, Lowa State Univesity. ( 14/5/11)
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17. Quick,G.R. (1973). Laboratory Analysis of the combine header. Trans ASAE 16(1): 5-12 18. Shigley, J. E.; Mischke, C. R., (2001) Mechanical Engineering Design, Sixth Edition, McGraw-Hill. 19. WINDSOR agricultural implements and spare parts. (3/3/2011) http://www.discplough.com/blades.html
24. Zam Abdul Karim , Malacca Biotechnology Corp (19 Aug 2010) http://www.daganghalal.com/HalalNews/HalalNewsDtl.aspx?id=1554
(31/10/10; 2:11)
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APPENDICES
Figure A.1: Sketch of the experimental unit of lemon grass harvester.
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