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SOKOINE UNIVERSITY OF AGRICULTURE
COLLEGE OF AGRICULTURE
DEPARTMENT OF ENGINEERING SCIENCE AND TECHNOLOGY
B.Sc. BIO-PROCESS AND POST-HARVEST ENGINEERING
SPECIAL PROJECT REPORT
By
AMIR,martnine J.
Supervisor(s): Prof V.C.K. Silayo
Title: Design and fabrication of low cost Irish potatoes processing line: Potato peeler
A SPECIAL PROJECT PRESENTED TO THE DEPARTMENT OF ENGINEERING
SCIENCE AND TECHNOLOGY OF SOKOINE UNIVERSITY OF AGRICULTURE IN
PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF BIO-
PROCESS AND POST-HARVEST ENGINEERING
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ABSTRACT
For the processing of potatoes, removal of the peel is an important unit operation. Hence, a pedal
operated potato peeler was designed and developed. The main parts of the integrated machine
were peeling drum, water spraying unit. The peeling drum, with brushes on the inside surface,
rotated and detached the peel from the potatoes by abrasion. The water spraying unit washed the
potatoes and, simultaneously, the peel was removed from the drum through the peripheral
clearance of the drum along with the flow of water. The water pipe, shafts and chain drives were
significant parts of the machine. The machine worked at 102.75 rpm with a 43.2 kg/hr capacity
at average time of 1.25 minutes and flesh loss of 1%.
Potato peeling machine was fabricated and efficiency of 62.5% and with time of 1.25 minutes
was attained.
It is recommended that by designing a new system within the unit of peeling drum which will
increase the efficiency of peeling potatoes by placing brushes with protruding wires which are in
form of zig-zag and placing adjustable speed to determine the suitable speed of rotating the drum
during peeling process for improvement of the machine
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ACKNOWLEDGEMENTS
First and foremost I would like to thank my project supervisor Prof. V.C.K. silayo for his
guidance and support in this project, which enables the project to run smoothly. His teaching and
his encouragement had broadened my perspective towards the engineering world.
Besides that, I would also like to express gratitude to University of sokoine,
all lecturers from Department of Engineering, supporting staffs and to all my friends who
had also helped me either directly or indirectly in gathering information and opinion
provision.
Lastly, my "endless" thanks to my family for their love that have kept me going
and never giving up hope in me.
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TABLE OF CONTENTS
ABSTRACT.............................................................................................................................. ii
ACKNOWLEDGEMENTS .................................................................................................... iii
TABLE OF CONTENTS ........................................................................................................ iv
CHAPTER ONE .......................................................................................................................1
1.0 INTRODUCTION .............................................................................................................1
1.1 BACKGROUND...................................................................................................................1
1.2 Problem statement and justification .......................................................................................2
1.3 Objectives .............................................................................................................................2
1.3.1 Overall objective ................................................................................................................2
1.3.2 Specific objectives ..............................................................................................................2
CHAPTER TWO ......................................................................................................................3
2.0 LITERATURE REVIEW ...................................................................................................3
CHAPTER THREE ..................................................................................................................5
3.0 METHODOLOGY ..............................................................................................................5
3.1 Machine Design ....................................................................................................................5
3.1.1 Machine Components and Specifications. ...........................................................................5
3.2 Material Selection .................................................................................................................5
3.2.1 Wood .................................................................................................................................5
3.2.2 Mild Steel ...........................................................................................................................6
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3.3 CALCULATIONS BASED ON WORKING MECHANISM OF THE PEELING
MACHINE..................................................................................................................................7
3.3.1 Design calculations .............................................................................................................7
3.3.2 Number of brushes required to be fitted into the calculated number of wood pieces, ...........8
3.4. Wheel specifications .............................................................................................................8
3.4.1 Roller Chain Design for power transmission .......................................................................9
3.4.2Machine Capacity and Efficiency ...................................................................................... 11
3.4.2.1Machine Capacity ........................................................................................................... 11
3.5 Machine Efficiency ............................................................................................................. 11
3.6 TESTING OF THE MACHINE .......................................................................................... 11
CHAPTER FOUR ................................................................................................................... 14
4.0 RESULTS AND DISCUSSION ........................................................................................ 14
CHAPTER FIVE..................................................................................................................... 15
5.0 CONCLUSION AND RECOMMENDATIONS .............................................................. 15
5.1CONCLUSION .................................................................................................................... 15
5.2 RECOMMENDATION ....................................................................................................... 15
REFERENCES ......................................................................................................................... 17
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LIST OF TABLES
Table 1: Showing Peeling Efficiency of machine (P.E) (%) ....................................................... 11
Table 2: Showing peeling efficiency (P.E %) under constant number of potatoes ...................... 12
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CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND
In Tanzania, potatoes (Solanum tuberosum) are sometimes called "Irish potatoes" or "European
potatoes" (Viazi Ulaya in Swahili). Irish potato is one of mankind’s most valuable food crops in
the world with annual production volume of 347 metric million tones, produced in an estimated
area of 18.9 million hectares (FAOSTAT, 2004). It ranks fourth in the world as food crop after
maize, rice, and wheat (FAOSTAT, 2004). Among root crops Irish potato ranks first in terms of
volume produced and consumed followed by cassava, sweet potato and yams, and provides
roughly half of the world’s annual output of all roots and tubers, making it the largest non cereal
food and cash crop worldwide (FAOSTAT, 2004). It contributes energy and substantial amounts
of high quality protein and essential vitamins, minerals and trace elements to the diet (Horton,
1987). A single medium-sized Irish potato contains about half the daily adult requirement of
vitamin C, very low in fat (about 5 percent of the fat content of wheat), more protein, and twice
calcium than maize (Horton, 1987; Dean, 1994; McGlynn, 2007). The health benefits of potatoes
have been widely acknowledged and research is continuously finding new health benefits of
potatoes, such as a flavonoid called quercetin (Suszkiw, 2007).
Ludaladio et al (2010). project that in the future, world potato production is expected to grow at
a rate of 2.5% per year, thereby presenting opportunities for expanded utilisation and opening up
new market segments. To realise the full potential of this crop, developing countries must
address both supply and demand side constraints. (Lutaladio et al. 2009, 11.) Potatoes are a
traditional food crop, which refers to widely used diversification between a food crop and an
export/cash crop. The FAO (2006) publication states that while potato output has declined in
Europe, growth is so strong in developing countries that global production has nearly doubled
over the last 20 years.
Irish potato was introduced in Tanzania during 1920s by German mission in the Southern
Highlands (SH) of Tanzania where local farmers began its cultivation in small scale gardens
(Jakobsen and Mallya, 1976; Macha et al., 1982), it is becoming an important cash and food crop
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(Kelly, 2006). Since its introduction, production trends have been increasing positively
(FAOSTAT, 2007).
Potatoes will have growing demand in the future. The reasons for expected growth in demand are
a lack of substitute crops, an increasing population, urbanization, an improving road network,
and changing eating habits. Demand for processed products like French fries and crisps are
expected to grow. This lead to the demand of good harvesting, handling, and processing
practices
1.2 Problem statement and justification
In East Africa, Tanzania in particular, there are many constraints on the spread and adoption of
potatoes processing line, including availability of affordable processing kits and technologies. In
developing countries, street Venders use mostly women and children to peel, slice and clean
potatoes. Low cost potatoes processing line can fill an important technology gap for the street
vender who makes French fries. Street venders are able to benefit from this processing line
because they can be adapted to small and medium production. Low-cost processing line retains
the benefits of conventional processing line while removing the factors that prevent their uptake
by small venders. Using this processing line will save time and the overall workload of women
and children will also significantly be reduced. There will also be a notable improvement in
income generation from use of low-cost processing line by small venders.
1.3 Objectives
1.3.1 Overall objective
The overall objective is to design and fabricate pedal driven potatoes processing line for small
vendors.
1.3.2 Specific objectives
The specific objectives include:
(i) To design and fabricate paddle potatoes peeling machine.
(ii) Peeling a potato
(iii) Design a suitable peeler machine for vendors.
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CHAPTER TWO
2.0 LITERATURE REVIEW
Potatoes have been processed in the U.S. since 1831 when the first starch plant was established.
Potato chips are also reported to have been first prepared during the mid-19th century, but
remained on a small commercial scale until World War II when improved peeling and frying
techniques were developed. The freezing industry was also launched in the 1940’s.
The growth in potato processing has been phenomenal. Prior to 1960, reports on potato
utilization did not differentiate between snack foods (chips and shoestrings) and fresh
consumption. By 1970, U.S. processed utilization was nearly equal to that of fresh. Major
processing uses of potatoes now are chips, dehydration, and freezing. By the late 1980s, these
three uses accounted for about 98 percent of all processing in the U.S.
The chipping industry is more evenly spread. Chipping plants can be found in every region. The
fragility of potato chips and the high cost of shipping low-density products make long distance
shipping undesirable. As a result, chipping plants tend to be located near heavily populated areas.
The market for processing potatoes exhibits some characteristics that are quite different from the
fresh market. Since French fry processors are concerned about finished product quality,
processing contracts place emphasis on those raw product characteristics that influence finished
product quality. Specific gravity is of particular concern and processors pay premiums for high
specific gravity and penalize for low specific gravity. Other characteristics, such as tuber size
and grade, have also generated premiums. Contract provisions have changed over time in
response to changes in processing technology, production practices and the appearance of new
quality factors in individual growing areas. The processing industry is a major and expanding
market for potatoes which benefited both the producer and the consumer. (Joe Guenthner, 18)
Most potatoes in Tanzania are consumed as food at household level and through food service
outlets such as restaurant and street food vendors. It has been established that significant
volumes of ware potato in major urban centre’s are consumed as French fries (chips) through
food service outlet and mainly street food vendors (SAGCOT, 50).
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The processing of potatoes in Tanzania is still very small-scale and undeveloped; currently it is a
common scene to find unsorted and poor packaged potatoes in the market and groups of women
at the market place peeling potatoes for street vendors and restaurants that make French fries.
This indicates that people who make French fries are ready to pay a little bit more for peeled
potatoes.
In the research made by Mwakasendo et al. (2007), found that the only company in Tanzania
with a cold store chain was the French fries Company Bright Choice Company Ltd. The firm
imports frozen French fries and does not use local (fresh) products because of the low quality
and infrequent inconstant supply. (Mwakasendo et al. 2007, 43.). However, demand for French
fries in hotels and restaurants is constantly increasing, forecasting growth for the whole potato
industry.
Low cost potatoes processing line (pedal driven potatoes washer, peeler, sorter and slicer
machines) technology is appropriate for small venders who cannot afford conventional
processing line because of high initial investment costs, this will help them to copy with the
increase in demand of snacks food that keep on growing due urbanization and changes in life
style.
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CHAPTER THREE
3.0 METHODOLOGY
The objective of this project is to design paddle driven peeling machine for small vendors. The
concept is developed based on the cost, ergonomics and easy handling of the equipment. The
following steps are designing the machine, material selection, machine fabrication, performance
analysis.
3.1 Machine Design
3.1.1 Machine Components and Specifications.
Singh(1995) describes the a power-operated batch type potato peeler that includes a peeling
drum (670 mm in length and 450 mm in diameter) And water- spraying units. The following are
main components of the paddle driven peeling machines.
1. Feeding - this is feed party in which the potatoes feeder into the drum. The feeder part
was designed in such a way that allows a person to open during feeding and removing
potatoes after being peeled.
2. Bearings and its shaft- are used to rotate the drum during peeling process.
3. The peeling drum- the peeling drum fitted with brushes (40mm) on the inside surface
removes the skin from potatoes by means of abrasions as drum rotates. The drum was
constructed by using wooden slats of 80mm length and 60mm in which the brushes was
fitted on it using screws.
4. Bicycle paddle – is one of the component used for rotating the drum unit.
3.2 Material Selection
Material selections is most important criteria during processing and handling of the food crops as
some of the materials are causing corrosion to the food and also in terms of cost some of them
are very expensive. Proper selection of material also can reduce product failure or increase
product life time. Working environment are also important issues and is taken into consideration
during material selection. The following are materials used for the design of paddle driven peeler
machine.
3.2.1 Wood
Wood materials were used in the construction of the peeling drum.
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The wood material was used in the design of machine due to the following factors:
1. Availability of wood is cheap and at low cost compared to steel and aluminum sheet.
2. Suitable for handling as materials does not undergo rusting and corrosion.
3. Wood manufacturing processes are not expensive compared to other materials like steel
and aluminum sheet.
4. The strength of wood materials is very hard and durable(high strength to weight ratio)
5. water resistant
3.2.2 Mild Steel
The machine frame is made up of mild steal materials. Uncoated mild steel can easily form
corrosion. Therefore, all surfaces for the frame have been coated with oil paint. The components
made up of mild steel are body frame, stand, rotating shaft, bearings and the gearing system.
Machine frame
This is the main skeleton of the machine as it supports all parts of the peeler. The frame is
rectangular in shape made of squire pipes. Squire pipes are held by welding joints to support the
drum and for stability of the machine.
Table no.1 showing materials used in design and fabrication of the machine
components Materials
standard
Reasons Manufacturing process
Peeling drum Wood
(80*60*30mm)
Available,
cheap
Sawing,cutting,fitting,drilling,finishing
Bicycle chain Mild steel Available,
cheap
-
sprocket Mild steel available -
Quarter pins aluminum available -
Bicycle pedal Mild steel available -
Squire pipes Mild steel
(40*40*3mm)
Available,
cheap
Welding and cutting
Shaft Mild steel Easy to
manufacture
Cutting into size
Bearings Mild steel available -
Bolts & nuts M8*8,M10*4 Available,
cheap
-
screws Mild steel available -
freewheel Mild steel available -
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Selection of Manufacturing Process
Many techniques were employed in order to manufacture the machine parts and components
during designing and fabrication of this machine. These include; machining, joining and
finishing, Mechanical fastening and finishing includes coating and painting.
Fabrication
The peeling drum fitted with brushes was fabricated according to design specifications.
Joining Processes
Are quite important in the design and fabrication, these include; welding, jointing, fitting
Painting/Coating
Painting process is only applied on mild steel surface that tends to suffer from oxidation.
Because of its decorative and functional properties such as environmental protection, low cost,
relative ease of application and the range of available colors, paint is chosen to use as a surface
coating.
3.3 CALCULATIONS BASED ON WORKING MECHANISM OF THE PEELING
MACHINE.
3.3.1 Design calculations
Calculations of the peeling drum design;
Diameter of the drum (D) = 400 mm
Calculate total circumference = 3.142*D
=1256.64 mm
From the design, given the length of piece of wood 800mm and 60mm,
Calculating the number of wood required to round the drum / circle and spaces between the
wood pieces.
Number of wood = 16
From
Total space occupied by wood pieces = 16*60 width
= 960mm
Total space between the wood piece =1256-960
= 296mm
Number spacing =16 mm
Calculating average spaces between wood piece and another is;
= 296/16
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=18.5 mm
= 1.85cm
3.3.2 Number of brushes required to be fitted into the calculated number of wood pieces,
From;
Number of wood pieces = 16
One brush cover = 250mm
In one piece of wood contain = 3 brushes
Total brushes in the drum = 3*16 = 48 brushes
3.4. Wheel specifications
Sprocket/free, wheel Diameter
D=
Or P= ΠD/N
Where; D = Sprocket diameter (mm), P= Chain pitch (mm) and N=Number of teeth in the
sprocket/freewheel.
In preliminary calculation the following measures are given from different sources for reliability
purpose P=13mm, so using N= 47 for sprocket and N=16 for freewheel, and crank length (L
Crank) =170mm, D can be calculated as;
D sprocket =13/sin (180/47) = 194.63mm
D freewheel =13/sin (180/16) =66.64 mm
Chain Length
L chain = 2C+ (D sprocket + D freewheel)/2
L chain = 2C + (194.6+66.64)/2
L chain = (2C+130.62) mm, for C = 600mm
L chain=1330.62
Chain links
L=
Where; L=Chain length in links
P=Pitch (mm)
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C= Centre distance (mm)
N1= Number of teeth of free wheel
N2=Number of teeth of sprocket
L =
Chain links =124
Chain Velocity (V)
Assuming it provide a constant velocity ratio as result of neither slippage no creep. Has ability of
driving single drive
V=
Where; D= diameter (194.63mm) and assuming pedaling produce speed (N) of (60-80rpm)
V=
V = 45.86
Velocity Ratio
VR=
VR = 47/16 = 2.97
3.4.1 Roller Chain Design for power transmission
Power, force and torque delivered by chain
Assumptions
Pitches are evenly distributed
Centre distance doesn’t vary
There is no slippage and creep
To calculate force and torque
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Force exerted on crank (W)
Assuming the average force a man can exert is equal to 1/10 of his / her own weight. Assuming
average man having weight of 65kg.
W= mg where m=mass, g=acceleration due to gravity and W= weight/force
=65kg*9.81m/s2
=637.65N*0.1
Force exerted on the crank is about 63.765N
Torque produced by crank.
T = Force* Perpendicular distance
T crank=W*Lcrank
T crank=63.765*0.17=10.84Nm
Angular speed of sprocket ( )
The most powerful muscles in body in the most suitable motion (a smooth rotary motion) at the
most convenient speed 60-80rpm (Makungu 1995).
Making average of 70rpm
Let 1=70rpm
From the relation,
N sprocket sprocket = N freewheel freewheel
Freewheel =47*70/16 =205.625rpm
Then, angular speed can be calculated by;
W = (2Π )/60
W1 = (2Π sprocket)/60
= (2Π*70)/60=7.33 rad/sec
W2 = (2Π* freewheel)/60
= (2Π*205.625)/60=21.53rad/sec
Power
It is calculated by the following formula;
P=TV =F* L crank V=
Where P= Power
T=Torque
V=Velocity
D=Diameter
= *0.19463*10.84*70RPM*/1000
Power = 0.464 W approximately
= 0.5 W
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3.4.2Machine Capacity and Efficiency
3.4.2.1Machine Capacity
It is usually given as mass per unit time, can be either be measured as the through put capacity,
which is equal to the total weight of the material handled per hour or as material capacity which
is equal to the weight of material cleaned per time. Calculations involve measuring weight and
time.
Through put capacity=Total material handled by machine (kg)/ (Total time taken)
3.5 Machine Efficiency
Machine efficiency= (no. of peeled potatoes)/ (total number of potatoes)
3.6 TESTING OF THE MACHINE
During testing of machine the following data are determined;
1. Efficiency of the machine (%)
2. The output capacity (kg/h)
3. Peeling losses (kg/h)
SAMPLING PROCEDURES AND SELECTION PROCESS
Testing procedures
1. Arranging samples into different groups or numbers as shown in the table 1 and 2
2. Testing time arrangement
3. Testing the samples according to time shown
4. Data collection after testing (peeled and unpeeled potatoes)
5. Calculating the efficiency of machine (%)
6. Calculating its capacity (kg/hr)
7.
TABLE OF RESULTS
Table 1: Showing Peeling Efficiency of machine (P.E) (%)
Speed of
rotation (rpm)
Duration of
peeling (min)
N0 N1 N2 (P.E %)
75 1 6 4 2 67
80 1 10 8 2 80
74 1 15 7 8 46
59 1 20 11 9 55
Mean speed of
rotation = 72
mean 62
Where
N0 = total number potato before peeling
N1 = number of peeled potato
N2 = number of unpeeled potato
From table 1
Peeling efficiency = (no. of peeled potatoes)/ (total number of potatoes)
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Sample 6
P.E % = 4/6×100%
= 67%
Sample 10
P.E % = 8/10×100%
= 80%
Sample 15
P.E % = 7/15×100%
= 46%
Sample 20
P.E % = 11/20×100%
= 55%
Table 2: Showing peeling efficiency (P.E %) under constant number of potatoes
Speed of
rotation (rpm)
Duration of
peeling (min)
N0 Weight of
samples(g)
N1 N2 (P.E
%)
48 0.5 10 900 2 8 20
65 1 10 6 4 60
139 1.5 10 9 1 90
162 2 10 8 2 80
Average
speed= 102.75
Average time=
1.25
mean 62.5
Where
N0 = total number potato before peeling
N1 = number of peeled potato
N2 = number of unpeeled potato
From table 2
Peeling efficiency = (no. of peeled potatoes)/ (total number of potatoes)
Sample 10 at time 0.5min
P.E % = 2/10×100%
= 20%
Sample 10 at time 1min
P.E % = 6/10×100%
= 60%
Sample 10 at time 1.5min
P.E % = 9/10×100%
= 90%
Sample 10 at time 2 min
P.E % = 8/10×100%
= 80%
From the sample analyzed, 10 number of samples = 900g
Machine capacity = mass (kg)/time taken
= 0.9 (kg)/1.25 min
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=0.72 (kg)/min×60min/hr
= 43.2 (kg)/hr
Graph of peeling efficiency against time of peeling used
PEELING LOSSES EFFICIENCY
The efficiency of peeling losses was determine by measuring the weight of potatoes before
peeling and after peeling the potatoes but the results was showing the same as before, this might
have been caused by a machine which removes the skin of potatoes only, the flesh loss can be
approximately 1% when you compare to manual peeling, the machine saves more than ten times
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CHAPTER FOUR
4.0 RESULTS AND DISCUSSION
Results obtained from table 1 indicates the peeling efficiency of the machine under constant time
of one minute but with variation of number of potatoes, the data shows that as the number of
potatoes increases the efficiency of machine decreases i.e. number of unpeeled potatoes was
increasing, an overall efficiency of 62 percent results with time of one minutes, during
collection of data as number of peeled increased to beyond 25, the machine was not able to
function properly, so the maximum of 20 potatoes should be suitable for this peeler machine.
Table 2 presents the results for peeling efficiency of machine with constant number of potatoes
while varying the time of peeling, from these results the efficiency increases as time of peeling is
increased, from the table overall peeling efficient of 62.5 percent was obtained with capacity of
43.2 kg/hr. This is probably due to the fact that an increase in the speed of rotation increases the
rate of contact of the abrasive surfaces rubbing against the potato such that, sides of the potato
was peeled over and over until the prescribed time elapsed, but maximum time should not be
more than two minutes because it causes more severity on the surface of the potatoes and
damages
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CHAPTER FIVE
5.0 CONCLUSION AND RECOMMENDATIONS
5.1CONCLUSION
The fabricated potato peeling machine at the speed of 72 revolutions per minute had an average
peeling efficiency of 62 percent .However, when the speed was raised to 102.75 revolutions per
minutes there was an average peeling efficiency of 62.5 percent. Hence, high speed of rotation
of the peeling machine will increase the peeling efficiency and an average time of 1.25 minutes
and the peeling process is easier to control.
5.2 RECOMMENDATION
1. Design of new system within the unit of peeling drum which will increase the efficiency
of peeling potatoes by placing brushes with protruding wires which are in form of zig-zag
2. Due to heavy weight of the machine, the weight may be reduced by designing a machine
using stainless steel material especially on the peeling drum
3. Placing adjustable speed to determine the suitable speed of rotating the drum during
peeling action
4. The wood used to fasten the brushes should be fitted inside the round drum to increase
its strength because if the machine subjected under high load, the wood fastened using
screws might separated apart
5. Construction of a frame cover to protect the spread of water and designing of suitable
discharge of water during operation of the machine
6. The feeding and discharging chute should be designed in such a way it doesn’t create an
increase in weight on one side of the peeling drum (maintaining equal balance of the
drum )
7. Design of stainless steel material in a unit fastened to limit the potato from moving
together with peeling drum
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Figure 1: showing the data collection analysis
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REFERENCES
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chains. Technical and policy options for developing countries. Rome: FAO.
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Treasure: The Potato. Retrieved jolly 1, 2015 from
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FAOSTAT (2004). Agricultural Data. Provisional 2003 Production and indices data Crop
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Horton, D. (1987). Potatoes production, marketing and programs for developing countries.
[http://www.cipotato.org] site visited on 2/7/2015.
Jakobsen, H. (1976). Potato Production in Tanzania. In: Regional Workshop on Potato Seed
Production and Marketing, Nairobi, October, 1976. 4pp
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McGlynn, A. (2007). Re- Inventing the potato. A marketing approach for 21st century In:
National potato conference and Trade show. Glen Royal Hotel. 14TH Feb. 2007;May
Rooth, Co. Kildare. 44 pp.
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Mwakasendo, J.A., Mussei A. N., Kabungo C.D., Mende D. H. and Gondwe B. J. (2007). Market
for Fresh and Frozen Potato Chips in the ASARECA Region and the potential for
Regional Trade: The Case of Tanzania Mbeya, Tanzania. 46pp.
SAGCOT. Value Chain and Market Analysis. Retrieved July 1, 2015 from
http://www.sagcot.com/pdf
Suszkiw, Jan. 2007. Phytochemical Profilers Investigate Potato Benefits. Agricultural Research
Magazine. 55 (8): 20–21.