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UNIVERSITI PUTRA MALAYSIA
MD. AKHIR BIN HAMID
FK 2010 70
DESIGN AND DEVELOPMENT OF A DIGGING DEVICE FOR HARVESTING SWEET POTATO
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DESIGN AND DEVELOPMENT OF A DIGGING DEVICE
FOR HARVESTING SWEET POTATO
By
MD. AKHIR BIN HAMID
Thesis Submitted to the School of Graduate Studies, Universiti Putra
Malaysia, in Fulfilment of the Requirements for the
Degree of Doctor of Philosophy
October 2010
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DESIGN AND DEVELOPMENT OF A DIGGING DEVICE
FOR HARVESTING SWEET POTATO
By
MD. AKHIR BIN HAMID
October 2010
Chairman: Professor Desa Ahmad, PhD, P. Eng.
Faculty: Engineering
This thesis describes a study on the design, fabrication and testing of a prototype
sweet potato digging device for harvesting sweet potato tubers in bris soil. Design of
the digging device was based on a soil bin study having bris soil with mean moisture
content of 9.16% wet basis. The soil texture was sandy soil (fine sand 94.53%), and
the mean bulk density of soil was 1.44 g-cm-3
. Three types of soil digging tools were
designed and fabricated to determine the optimum draft force. These were plane, V-
shaped and Hoe type blades. Plane and V-shaped blades were 30 cm long, and 13 cm
wide, while the Hoe type had three rods, 25 mm diameter, 30 cm long and 6.5 cm
wide with sharp cutting edge. The digging tools were tested in a soil bin filled with
bris soil to determine the optimum draft force. The experiments were conducted at
three depths and rake angles. All experiments were replicated three times at a constant
speed of 0.06 m.s-1
. The results from this study were analysed and the best type was
selected, fabricated and used as the prototype harvesting device.
Analysis of variance (ANOVA) for all blade types and rake angle show that, there
were no significant differences between blade type and rake angle on draft force,
vertical force, moment and area of soil disturbance. Comparison between all blade
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types and blade depths to measured draft force and area of soil disturbance showed
that the highest draft of 0.54 kN was caused by plane blade at the optimum depth of
20 cm with 0.180 m2 of soil disturbance area. The V- shaped blade had the mean draft
of 0.51 kN at the optimum depth of 20 cm. The area of soil disturbance was 0.185
m2.
The
best choice was V-shaped blade with rake angle of 30
o at depth of 20 cm.
The hoe-type tool had a mean draft of 0.34 kN and soil disturbance area of 0.184 m2.
The hoe-type was not selected because of excessive damage to tubers.
Based on the above information a double row sweet potato harvesting device was
designed and developed. The machine was designed and developed at the
Mechanization and Automation Centre, Malaysian Agricultural and Development
Research Institute (MARDI) workshop. The machine consists of digger blades,
double disc coulter for cutting vines, digger blade guide, and adjustable drum for
blade digger depth control during operation, conveyor lifter, conveyor separator and
bucket collector. Digging blade depth is adjustable with common hand tools. The
harvester was designed to be pulled by Standard Four–wheel tractor of 70 HP or
larger. The tractor power requirement was estimated by Algorithm analysis and tool
draft force predicted by Hettiaratchi and Reece’s model. Under normal operation, the
machine requires three persons; one tractor driver and labourers on the harvester
platform to collect the sweet potato tubers. The machine was tested on bris soil at
Mardi Station, Telong, Kelantan. The digger blade was set at 35 cm depth since the
average tuber zone depth was 30 cm, tractor engine speed between 1700 – 2000 rpm
and PTO speed setting at 540 rpm during operation. The mean effective work of the
machine in bris soil was 93.64 and 90.49% for Telong and VitAto varieties
respectively. The average ground speed and turning time during operation was 0.56
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km-hr-1
and 102.7 s and 0.99 km-hr-1
and 81.22 s for plots A and B respectively. The
different results in tractor speed and turning for both plots were due to the different
drivers operating the prototype machines. Other factors include the difference of plot
size. Plot A had 50 m long seedbed while Plot B, 70 m. The harvesting efficiencies
for both plots were above 90% and show no significant difference. The total
productive time (harvesting time) and unproductive time (turning time) in plot A, with
tractor speed 0.56 km-hr-1
, was 14.8 hours for harvesting a hectare of sweet potato (
0.068 ha-hr-1
). In plot B, the total time for harvesting a hectare of sweet potato was
8.35 hours (0.12 ha-hr-1
) with tractor speed of 0.99 km-hr-1
. The average harvesting
time for both plots was 11.47 hr- ha-1
. The average field work rate was 0.087 ha-hr-1
or 34 man-hr-ha-1
compared to manual harvesting of 150 man hr-ha-1
.
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MEREKABENTUK DAN MEMBINA SEBUAH PERANTI PENGGALI
UNTUK PENUAIAN KELEDEK
Oleh
MD. AKHIR BIN HAMID
October 2010
Pengerusi : Professor Desa Ahmad, PhD, P. Eng.
Fakulti : Kejuruteraan
Tesis ini menghuraikan kajian rekabentuk, pembangunan dan mengujiguna keatas
peranti penggali, mesin penuaian ubi keledek ditanah bris. Tiga jenis peranti penggali
diuji didalam kotak berisi tanah bris yang mempunyai kelembapan purata 9.16%
pengkalan basah. Tekstur tanah adalah berpasir (pasir halus 94.53%), dan
berketumpatan purata 1.44 g-cm-3
, Tiga jenis peranti penggali digunakan dalam
kajian adalah; jenis kepingan, jenis berbentuk V dan jenis hoe. Lebar mata pengorek
bagi jenis kepingan rata dan berbentuk V adalah 13 cm dan panjangnya adalah 30 cm.
Peranti jenis hoe mempunyai tiga batang besi 30 cm panjang dan bergaris pusat 25
mm dengan bahagian hujung pemotong yang tajam. Jarak diantara batang adalah 6.5
cm dan dipatrikan berbentuk cangkol bermata tiga. Ketiga-tiga jenis peranti penggali
ini diuji dalam kotak tanah berisi tanah bris bagi menentukan daya tarikan yang
optimum. Percubaan dilakukan pada tiga tahap kedalaman dan sudut tusukan. Semua
ujikaji diulang sebanyak tiga kali pada kelajuan malar 0.06 ms-1
. Keputusan jenis
penggali yang terbaik dipilih untuk digunakan dalam rekabentuk prototaip mesin
penuai keledek.
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Analisis varians (ANOVA) untuk semua jenis peranti penggali dan sudut tusukan
menunjukkan bahawa, tidak ada perbezaan yang signifikan antara jenis peranti
penggali dan sudut tusukan peranti penggali keatas daya tarikan, daya menegak,
momen dan luas kawasan gangguan tanah. Perbandingan antara semua jenis peranti
pengorek dan kedalamanya menunjukkan peranti pengorek jenis kepingan
menghasilkan daya draft tertinggi 0.54 kN pada kedalaman 20 cm dan keluasan tanah
terganggu adalah 0.180 m2. Peranti pengorek berbentuk V menghasilkan min daya
tarikan sebanyak 0.51 kN pada ke dalaman 20 cm dengan keluasan tanah terganggu
0.185 m2. Peranti bentuk V dengan sudut 30
o dipilih dalam rekabentuk mesin penuai
ubi keledek. Peranti berbentuk cangkol bermata tiga (hoe) mempunyai purata draft
0.34 kN dan 0.184 m2 keluasan tanah terganggu
. Walaupun peranti jenis ini
mempunyai mean daya tarikan terendah, tetapi ianya tidak dipilih kerana bentuk
pecahan tanah yang mendorong kerosakan yang tinggi pada ubi ketika beroperasi.
Berdasarkan maklumat di atas sebuah mesin penuai ubi keledek telah di bangunkan.
Mesin ini adalah ubahsuaian mesin pengorek kentang. Ianya dibangunkan di Pusat
Mekanisasi dan Automasi, Institut Penyelidikana dan Pembangunan Pertanian
Malaysia (MARDI) Workshop. Mesin terdiri dari peranti penggali bentuk V, dua
piring Coulter untuk memotong lebihan jalaran tanaman, serta mengawal arah
pergerakkan peranti penggali, drum kawalan kedalaman peranti penggali selama
operasi, konveyor pengangkat, konveyor pemisah dan bakul pemungut ubi. Peranti
penggali boleh disuaikan pada kedalaman tertentu. Mesin penuai ubi keledek ini
direka untuk ditarik oleh traktor empat roda 70 HP atau lebih besar. Keperluan kuasa
traktor dianggarkan melalui Algorithm analisis dan daya tarikan model Hettiaratchi
dan Reece. Dalam operasi biasa, mesin memerlukan tiga orang, satu pemandu traktor
dan lainnya pekerja berdiri pada platform mesin sambil memungut dan mengumpul
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ubi. Mesin diuji di tanah bris di Mardi Station, Telong, Kelantan. Peranti penggali
ditetapkan pada 35cm kedalaman, purata zon kedalaman ubi ialah 30 cm, kelajuan
engine traktor pada kedudukan antara 1700-2000 rpm dimana PTO di setkan pada
540 rpm semasa operasi. Keputusan dari ujian mesin menunjukan purata
keberkesanan kerja mesin di tanah bris adalah 93.64 dan 90.49% untuk keledek variti
Telong dan VitAto. Purata kelajuan panduan trektor dan masa pusingan semasa
pertukaran batas adalah 0.56 km jam -1
dan 102.7 s dan 0.99 km-jam-1
dan 81.22 s
untuk plot A dan B setiap satu. Kelajuan pemanduan traktor berbeza bagi setiap plot
kerana pemandu yang berbeza mengendalikan prototaip mesin penuai keledek.
Faktor-faktor lain termasuklah perbezaan saiz plot. Plot A 50 m panjang sementara
Plot B, 70 m. Kecekapan penuaian untuk kedua plot melebihi 90% dan tidak
menunjukkan perbezaan yang signifikan. Jumlah masa produktif dan tidak produktif
di plot A dengan traktor kelajuan 0.56 km-jam-1,
adalah 14.8 jam untuk menuai satu
hektar ubi keledek (0.068 ha-jam-1
) manakala plot B, jumlah masa untuk menuai satu
hektar ubi keledek adalah 8.35 jam (0.12 ha-jam-1
) dengan kelajuan traktor 0.99 km-
jam-1
. Purata masa penuaian untuk kedua-dua plot adalah 11.47 jam-ha-1
. Purata kadar
kerja diladang adalah 0.087 ha-jam-1
bersamaan 34 orang-jam-ha-1
berbanding dengan
penuaian secara manual 150 jam-ha-1
.
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ACKNOWLEDGEMENTS
At the outset, I bow to the grace and mercy of the Almighty Allah for the patience and
strength bestowed upon me to complete this thesis. I would like to express my
sincere gratitude to my respected supervisor Prof. Ir. Dr. Desa Ahmad, Head
Department of Biological and Agricultural Engineering, Faculty of Engineering,
Universiti Putra Malaysia, for his untiring inspiration, encouragement and invaluable
guidance towards the write up of this thesis. Without his scholastic criticisms, whole-
hearted assistance, unfailing interest, constructive criticism, continuous supervision
and valuable suggestions throughout the period of this research, I would not have
completed this thesis.
I would also like to express my deepest gratitude and indebtedness for the kind
cooperation of my supervisory committee members Associate Prof. Ir. Dr. Azmi
Yahya, Prof. Dr. Ir. Shamsuddin Sulaiman, Deputy Dean of Graduate School; and Dr.
Ir. Ibni Hajar Rukunuddin, Director of Mechanization and Automation Research
Center-MARDI in the successful completion of this study. Their contribution and
suggestions helped to overcome many errors and showed me the right direction
during the course of this work.
I would also like to express my gratitude to the Malaysian Agricultural Research and
Development Institute (MARDI) for the financial support during this study at
Universiti Putra Malaysia.
There are many other people whom I would like to thank for their help and support
during this study at Universiti Putra Malaysia especially Mr. Wan Fariz Wan Azman,
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Mr. Saleh Bardos, Mr Salleh Rusdi, Mr. Aris Abdullah and Mr. Rusdi who helped me
a lot to complete my study, Mr Mohd. Anaur Mat of Innovasi Anggerik SDN. BHD.
and Mr. Tajeri Hashim of Tasco SDN. BHD. for their assistance in the fabrication of
the machine.
Thanks also go to Dr. Aimrun, Dr. Darius El Pebrian, Mr. Anuar Abdullah, Mr.
Ahmad Ngalim, Mr. Badril Hisham and Mr. Hossein with whom I shared ideas for the
completed study. Last but not least, I owe my greatest debt to my mother and my
father and to my wife Zulaini bt. Ismail, my daughters Nur Izzah, Nur Hashimah,
Nur A’Fifah, Nur Hani, Nur Jannah, Nur Hikmah Solehah and my only son
Muhammad Sulaiman who have given me love and support throughout my study.
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I certify that a Thesis Examination Committee has met on 14th
October 2010 to
conduct the final examination of Md. Akhir bin Hamid on his thesis entitled “Design
and Development of A Sweet potato Digging Device” in accordance with Universities
and University Colleges Act 1971 and the Constitution of the Universiti Putra
Malaysia [P.U.(A) 106] 15 March 1998. The committee recommends that the student
be awarded the Doctor of Philosophy.
Members of the Thesis Examination Committee were as follows:
Muhammad Salih b Hj. Ja’afar, Ir
Professor
Faculty of Engineering
Universiti Putra Malaysia
(Chairman)
Wan Ishak b Wan Ismail, PhD
Professor
Faculty of Engineering
Universiti Putra Malaysia
(Internal Examiner)
Mohd Sapuan b Salit @ Sinon, PhD
Professor
Faculty of Engineering
Universiti Putra Malaysia
(Internal Examiner)
Scott A. Shearer, PhD Professor
University Of Kentucky
United State
(External Examiner)
----------------------------------------------
SHAMSUDDIN SULAIMAN, PhD
Professor and Deputy Dean
School of Graduate Studies
Universiti Putra Malaysia
Date: 18 January 2011
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This thesis was submitted to the Senate of Universiti Putra Malaysia and has been
accepted as fulfilment of the requirements for the degree of Doctor of Philosophy.
The Members of the Supervisory Committee were as follows:
Desa Ahmad, PhD, P.Eng
Professor
Faculty of Engineering
Universiti Putra Malaysia
(Chairman)
Azmi Yahya, PhD, P.Eng
Associate Professor
Faculty of Engineering
Universiti Putra Malaysia
(Member)
Shamsuddin Sulaiman, PhD, P. Eng
Professor
Faculty of Engineering
Universiti Putra Malaysia
(Member)
IbniHajar Rukunnudin, PhD, P.Eng
Mechanization and Automation Research Center
Malaysian Agriculture Research and Development Institute (MARDI)
Serdang Selangor
(External Member)
__________________________________
HASANAH MOHD GHAZALI, PhD
Professor and Dean
School of Graduate Studies
Universiti Putra Malaysia
Date:
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DECLARATION
I declare that the thesis is based on my original work except for quotations and
citations that have been duly acknowledged. I also declare that it has not been
previously, and not concurrently, submitted for any other degree at Universiti Putra
Malaysia or any other institution.
________________________
MD. AKHIR BIN HAMID
Date: 14 October 2010
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TABLE OF CONTENTS
Page
ABSTRACT ii
ABSTRAK v
ACKNOWLEDGEMENTS viii
DECLARATION xii
LIST OF TABLES xvi
LIST OF FIGURES xviii
LIST OF PLATES xx
LIST OF APPENDICES xxii
LIST OF SYMBOLS xxiv
CHAPTER
1 INTRODUCTION 1.1 Current Industry 2
1.2 Potential for Sweet potato Commercial Cultivation 4
1.3 Problem Statement 5
1.4 Objectives of Study 6
2 LITERATURE REVIEW
2.1 Root and Tuber crops 8
2.2 World Scenario for Sweet potato Production 8
2.3 Agronomic aspect of Sweet potato 10
2.3.1 Bukit Naga 11
2.3.2 Kuala Bikam 11
2.3.3 Gendut 11
2.3.4 Jalomas and Telong 12
2.3.5 Vitato 12
2.4 Production areas 12
2.5 Land preparation 13
2.6 Characteristics of Bris and Sand-tailing Soils 14
2.7 Planting Practice and Spacing 15
2.8 Tillage requirement 17
2.9 Tillage practices 18
2.9.1 Research on tillage practices 19
2.9.2 Effect of tillage on sweet potato yield 20
2.10 Agronomic practices 21
2.10.1 Time of planting. 21
2.10.2 Density of planting 22
2.10.3 Harvesting method 23
2.11 Harvesting Practices 24
2.11.1 Mechanised Digging Operations 25
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2.12 Design concept of harvesting tools 30
2.12.1 Soil physical properties 32
2.12.2 Soil dynamic properties 34
2.12.3 Direct Shear Test 40
2.12.4 Tool Parameter 41
2.12.5 Mechanic of Tools 41
2.13 Analytical models 42
2.13.1 Payne’s Model 43
2.13.2 O’ Callaghan-Farrely’s Model 43
2.13.3 Hettiaratchi-Reece’s Model 44
2.13.4 Godwin – Spoor’s Model 45
2.13.5 McKyes – Ali’s Model 46
2.14 Draft and Power Requirements of Digger Implements 47
2.14.1 Effect of Tool Parameters on Draft Requirement 48
2.14.2 Draft – Depth Relationship 49
2.14.3 Soil- Tool Interaction 51
2.14.4 Digger Tools 51
2.15 Summary of Review 57
3 MATERIALS AND METHODS
3.1 Soil and Crop Characteristics 58
3.1.1 Field data Collection 59
3.1.2 Determination of Tuber Zone 61
3.1.3 Bris Soil Properties 63
3.2. Digging Equipment Design 69
3.2.1 Experimental procedure 70
3.2.2 Extended Octagonal Ring Dynamometer (EORD) 74
3.2.3 Soil description and Soil bed preparation 83
3.2.4 Experimental Procedure with Model Tools 84
3.3 Design of a Sweet potato Harvesting Machine 86
3.3.1 Design Features 87
3.3.2 Design of Main Working Components of a
Sweet potato Harvesting machine 88
3.3.3 Digger blade design and arrangement 88
3.3.4 Drum Depth controller 90
3.3.5 The Coulter Disc 92
3.3.6 Lifter Elevator 93
3.3.7 Separator Conveyor 96
3.3.8 Hopper and Guard 97
3.3.9 Sweet Potato Harvester Assembly 98
3.4 Machine fabrication 100
3.5 Field Observation and Performance Evaluation 105
3.5.1 Tractor Power Estimation 105
3.5.2 Experimental site 112
3.5.3 Field plot preparation 112
3.5.4 Experimental procedure 113
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4 RESULTS AND DISCUSSION
4.1 Properties of Bris soil 115
4.1.1 Soil Texture 115
4.1.2 Moisture Content and Bulk Density 116
4.1.3 Soil Penetration in field 117
4.1.4 Tuber Zone 118
4.1.5 Cohesiveness, Internal frict ion angle,
and Soil -Tool friction 119
4.2 Instrumentation Design 122
4.3 Measured Draft force in Model Soil Bin 122
4.3.1 Soil characteristic in soil bin 122
4.3.2 Draft force of model tool in soil bin 123
4.3.3 Effect of inclined angles on
digger blade draft requirement 124
4.3.4 Soil disturbance effect of Various Digging Tools 126
4.3.5 Statistical Analysis of Draft Force
Determination in a Soil Bin 130
4.3.6 Draft Force Prediction 135
4.3.7 Comparison with Other Methods 136
4.3.8 Summary Results and Discussion 141
4.4 Performance of the Prototype Designed
Sweet potato Harvester 143
4.4.1 Manoeuvrability 143
4.4.2 Tuber digging Tool 143
4.4.3 Depth Control Drum 144
4.4.4 Other Harvester Components 144
4.4.5 Tuber Damage 145
4.4.6 Field performance 145
5 CONCLUSIONS 148
6 SUGGESTIONS FOR FURTHER STUDY 153
REFERENCES 155
APPENDIX-A 164
APPENDIX-B 183
APPENDIX-C 187
APPENDIX-D BIODATA OF STUDENT 206