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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



(Internal Examiner)

Mohd Sapuan b Salit @ Sinon, PhD

Professor



(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


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



(Chairman)

Azmi Yahya, PhD, P.Eng

Associate Professor



(Member)

Shamsuddin Sulaiman, PhD, P. Eng

Professor



(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


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

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