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DESIGN & FABRICATION OF A MANUALLY OPERATED CARROT
WASHING MACHINE FOR SMALL SCALE FARMERS
A DISSERTATION SUBMITTED TO THE DEPARTMENT OF
AGRICULTURAL ENGINEERING
SCHOOL OF ENGINEERING SCIENCES
UNIVERSITY OF GHANA, LEGON
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD
OF BACHELOR OF SCIENCE DEGREE IN AGRICULTURAL ENGINEERING
BY
KINGSFORD KORANTENG
(10399395)
AGRICULTURAL ENGINEERING DEPARTMENT
SCHOOL OF ENGINEERING SCIENCES
UNIVERSITY OF GHANA
LEGON
MAY, 2016
i
DESIGN & FABRICATION OF A MANUALLY OPERATED CARROT
WASHING MACHINE FOR SMALL SCALE FARMERS
A DISSERTATION SUBMITTED TO THE DEPARTMENT OF
AGRICULTURAL ENGINEERING
SCHOOL OF ENGINEERING SCIENCES
UNIVERSITY OF GHANA, LEGON
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD
OF BACHELOR OF SCIENCE DEGREE IN AGRICULTURAL ENGINEERING
BY
KINGSFORD KORANTENG
(10399395)
AGRICULTURAL ENGINEERING DEPARTMENT
SCHOOL OF ENGINEERING SCIENCES
UNIVERSITY OF GHANA
LEGON
MAY, 2016
i
DECLARATION
I, hereby declare, that this work submitted to the school of Engineering sciences, UG, legon, with
the exception of references of other researchers which have been duly acknowledged, is the result
of my own research and that this project has never been presented anywhere for a degree.
MR. KINGSFORD KORANTENG ........................... ........................
(STUDENT) SIGNATURE DATE
DR. MALCOLM .N. JOSIAH ……..................... ..........................
(SUPERVISOR) SIGNATURE DATE
DR. S. ABENNEY MICKSON ........................ ........................
(HEAD OF DEPARTMENT) SIGNATURE DATE
ii
DEDICATION
This dissertation is dedicated to my wonderful parents, Nana Yaw Koranteng and Magaret Akoto
Konadu for raising me to be the person I am today and also to my lovely siblings Priscilla
Koranteng and Patrick Koranteng, for support, inspiration and love throughout my education.
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ACKNOWLEDGEMENT
The best of my thanks and appreciation goes to the Almighty God for His grace, strength,
protection and health to witness the end of this work. My heartfelt gratitude goes to my supervisor
Dr. Malcolm N. Josiah, for his untiring assistance, direction, comments, encouragement,
continuous guidance and supportive ideas.
I would like to express my heartfelt gratitude to all the lecturers in the Agricultural Engineering
department for their knowledge imparted to me and also a big thanks to the workshop manager,
Mr. Richard Nudekor for his technical advice and useful suggestions at every stage of the work.
To my entire family, especially my father, Nana Yaw Koranteng and mother, Magaret Akoto
Konadu and lastly to my lovely siblings, Priscilla Koranteng and Patrick Koranteng for their moral,
spiritual and material support. God richly bless you.
iv
ABSTRACT
Carrots after harvesting from the field need to be pre-cleaned of soil and other foreign particles
before processing or transporting to the market. Currently, farmers/traders in Ghana use the
traditional method in which carrots are washed by hand. A carrot washing machine was developed
to give the best solution to this problem. The carrot washing machine consist of wood drum made
of wood planks and two shafts (hollow shaft and solid shaft), and a center pipe made of aluminum
with holes drilled on it for water spraying. The carrot washing machine was designed to use either
the immersion and non-immersion type of wash. The carrot washing machine was put to test
against two labourers in the agricultural field and the machine proved to be time efficient. The
appropriate rotation of the drum was found to be between 12 to 13 rpm. Performance trial on the
machine shown that the average washing efficiency is approximately 94.3%.
Keywords: Immersion, Non-immersion, Carrot etc.
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Contents page
DECLARATION.......................................................................................................................................... i
DEDICATION............................................................................................................................................. ii
ACKNOWLEDGEMENT ......................................................................................................................... iii
ABSTRACT ................................................................................................................................................ iv
LIST OF FIGURES .................................................................................................................................. vii
LIST OF TABLES ................................................................................................................................... viii
CHAPTER 1 ................................................................................................................................................ 1
1.0 INTRODUCTION ................................................................................................................................. 1
1.1 Washing ........................................................................................................................................... 2
1.2 Problem statement ................................................................................................................................ 3
1.3 Significance of the study ....................................................................................................................... 4
1.4 Aims of the study ................................................................................................................................... 4
1.5 Objectives of the study .......................................................................................................................... 4
CHAPTER 2 ................................................................................................................................................ 5
2.0 LITERATURE REVIEW .................................................................................................................... 5
2.1 Immersion wash system ........................................................................................................................ 5
2.2 Non-immersion system ......................................................................................................................... 6
2.2.1 Commercial Washer ...................................................................................................................... 6
2.2.2 Small Scale Washer ........................................................................................................................ 7
2.2.3 Manually Operated Washer .......................................................................................................... 8
2.2.4 Wooden drum ................................................................................................................................. 9
CHAPTER 3 .............................................................................................................................................. 10
3.0 MATERIALS & METHODOLOGY ................................................................................................ 10
3.1 Materials selection .............................................................................................................................. 10
3.2 Cost Analysis ....................................................................................................................................... 11
3.2.1 Material Cost Estimation ............................................................................................................ 11
3.2.1.1 Material for Fabrication ....................................................................................................... 11
3.2.1.2 Standard Purchased Parts .................................................................................................... 11
3.2.2 Machining Cost Estimation ......................................................................................................... 11
3.2.3 Calculation for Material Cost ..................................................................................................... 11
3.3 Design consideration ........................................................................................................................... 13
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3.4 Carrot ................................................................................................................................................... 13
3.5 Description of the machine ................................................................................................................. 14
3.6 Main components ................................................................................................................................ 16
3.6.1 Washing drum .............................................................................................................................. 16
3.6.2 Main frame ................................................................................................................................... 18
3.6.4 Shaft .............................................................................................................................................. 20
3.7 The Prototype ...................................................................................................................................... 22
3.7.1 Principle of operation of the machine ........................................................................................ 22
3.8 Design calculation & mathematical formulas................................................................................... 23
3.8.1 The shaft design calculations ...................................................................................................... 24
3.9 Design of Bearing ................................................................................................................................ 26
CHAPTER 4 .............................................................................................................................................. 27
4.0 RESULTS & DISCUSIONS ............................................................................................................... 27
4.1 Testing for efficiency ........................................................................................................................... 28
4.2 Effect of Drum speed on Washing Efficiency ................................................................................... 30
5.1 CONCLUSION ................................................................................................................................... 31
5.2 RECOMMENDATIONS .................................................................................................................... 31
REFERENCES .......................................................................................................................................... 32
vii
LIST OF FIGURES
Figure page
Figure 2.1 Traditional method of washing carrots..........................................................................3
Figure 3.1 Small scale carrot washer..............................................................................................8
Figure 6.1 Isometric view of the carrot washing machine............................................................15
Figure 6.2 Orthographic view of the carrot washing machine......................................................16
Figure 6.3 Wash drum.................................................................................................................. 17
Figure 6.3.1 Orthographic view of the washing drum..................................................................17
Figure 6.4 Metal disc................................................................................................................... 17
Figure 6.5 Fabricated frame..........................................................................................................18
Figure 6.5.1 Orthographic view of the frame................................................................................18
Figure 6.6 Water trough............................................................................................................... 19
Figure 6.6.1 orthographic view of the water trough.....................................................................19
Figure 6.7 Hollow shaft................................................................................................................20
Figure 6.7.1 Orthographic view of the hollow shaft.....................................................................20
Figure 6.8 Solid shaft....................................................................................................................20
Figure 6.8.1 Orthographic view of the solid shaft........................................................................21
Figure 6.9 Fabricated carrot washing machine.............................................................................22
Figure 7.1 Dimensions for the shaft design..................................................................................24
Figure 7.2 Free body diagram of a section of the drum and the shaft..........................................24
Figure 9.1 Graph of time against quantity....................................................................................26
Figure 9.2 determination of the initial weight of the carrots…...………….……………………29
viii
LIST OF TABLES
Table Page
Table 3.1 Summary of materials selected.....................................................................................10
Table 3.2 Summary of the cost of components.............................................................................12
Table 3.3 Summary of the physical properties of carrot...............................................................13
Table 4.1 Time taken by labourers and the machine to wash carrots...........................................27
Table 4.2 Summary of washing results.........................................................................................29
Table 4.3 Effect of drum speed on washing efficiency.................................................................30
1
CHAPTER 1
1.0 INTRODUCTION
Processing is very important in transforming raw harvested agricultural products into valuable
products in the market. Processing of agricultural products is done to reduce wastage, raises the
quality of the product, enhance food security etc. According to Onwuala et al. (2006), process of
agricultural product increases the yield from a raw farm product by either causing an increase in
the amount of finish product, the number of finished product or both and to improve the total
economic value of a product. For an agricultural product to be processed, it has to undergo various
unit operations such as cleaning, sorting, grading, size reduction etc. Cleaning of agricultural
product is one of the most important unit operation in processing.
This project seek to focus on the cleaning operation of harvested carrot. Carrot (Daucus carota) is
a vegetable that belongs to the Umbelliferea (Apiaceae) family (Manosa, 2011). It is cultivated in
many countries throughout the world such as the Americans, Europe, south-west Asia and Africa
(Rubatzky et al., 1999) and this is mainly due to the fact that carrots have high nutritional value
(Al-Harbi et al., 1997; Munro & Small, 1997). The edible roots are nutritious and contain water,
protein, ash, vitamins and mineral (Norman, 1992).Vegetables (carrots) are the major sources of
vitamins and minerals in the human diet (Pamplona, 2008). There is no substitute to the role
vegetables (carrots) play in our meals (Drechel et al., 2010).
Carrots after being harvested from the field may have soil particles and other foreign materials
attached to them hence there is the need to remove these materials before processing. The removal
is accomplished by dry or wet brushes, rinsing or immersion in tap water, hot water or solutions
2
containing one of a number of cleaning or sanitizing agents, using equipment designed for the
commodity (Asamoah, 2014; Fallik, 2004).
1.1 Washing
Washing is a process of cleaning and sanitization of produced by dipping, rinsing, rubbing or
scrabbling. It plays an important role in processing of crop produce by adding value and also
improving on the quality and safety of the produce in post-harvest operation. In order to effectively
weigh, sort, grade harvested carrots there is the need to wash them (Oladip et al., 2006) in clean
water to remove dirt and other debris and surface contaminants (Asamoah, 2013). There are
different principles used in washing of agricultural product which include soaking in still water,
moving water over the product, spraying water on product, using rotary drum cleaner, brush
washing and shuffle or shaker washer (Henderson & Perry, 1980; Diamante, 2007). Different
washing machines have been developed for washing some Agricultural products such as potato,
melon seeds, cassava root and coffee (Oladip et al., 2014). Basically there are two main categories
of washing used by the industries. They are the immersion wash which employs the principles of
dumping, submerging or floating of the produce in water and the non-immersion wash which is
done by spraying or rinsing produced in a basket, wash bed drum or barrel washer (Henderson &
Perry, 1980). The effectiveness of washing is determined by the availability of water as the
cleaning liquid (Oladip et. al., 2014). This project is design to inculcate both type of wash, giving
the user options to switch to which ever method he/she prefers.
Ten (10) carrot farms in Accra were visited and a case study conducted on their harvest wash. The
method used by these farms were labor intensive and time consuming. This project seeks to find a
possible solution by designing a washing machine for carrots to alleviate the stress traders/farmers
go through to have their carrot wash.
3
1.2 Problem statement
In Ghana, carrot is one of the exotic vegetable which has high demand and value in urban centers
and it is a potential export crop (MOFA, 2002). Carrots after harvesting from the field needs to be
cleaned before transporting to the market. The act of cleaning harvested carrot is not normally
done by small scale farmers in Ghana. This is mainly due to the absence of appropriate mechanized
ways of cleaning the harvested root crops.
Most farmers/traders in Ghana normally use a traditional method to clean their harvested carrots
in which the carrots are washed manually using metal sponge, water and some preservative such
as potassium permanganate or salt.
A case study conducted by Asamoah (2014) at the Asante Mampong municipality and he showed
that processing of carrots by traders was either by washing and scrapping or washing only. He
finds out that in all, 84% washed carrots using metal sponge, 14% used brush to scrape whiles 2%
wash with bare hands. This is as a result of the expensive nature of washers. These methods, aside
the fact that they are laborious and time consuming, the process tends to contaminate the carrots
especially use of metal sponge. It is with this reasons we have looked into a mechanized way of
designing a low cost washing machine for carrots.
a) b)
Figure 2.1 Traditional method of washing carrots
4
1.3 Significance of the study
The proposed design will help farmers to:
Reduce the time used to wash harvested carrots.
Reduce the cost of labor employed to wash harvested carrots
Reduce the risk of contaminating harvested carrots with stones, metal sponge etc. during
washing.
1.4 Aims of the study
The design aims at:
• Developing a low cost manually operated carrot washing machine which will effectively
and efficiently wash carrots with reduce time and labor requirement.
1.5 Objectives of the study
The study was conducted to peruse the following objectives:
To design and fabricate a carrot machine suitable for small scale farmers
To compare the time required by the machine to wash crop effectively as against the
traditional methods.
To determine the efficiency of the washing machine for carrots.
5
CHAPTER 2
2.0 LITERATURE REVIEW
Carrots are very important to mankind due to its high nutritional value. They are consumed fresh
or cooked either alone or with other vegetable (Asamoah, 2012).In some cases, fresh carrots are
grated and use in salads and the tender root are pickled (Sharma et al., 2006). Bunyaphlanan (1973)
worked on the mechanical properties of carrots. In order to process harvested carrots, it is a
necessity to wash them. Most farmers/traders use the traditional method to wash harvested carrots
from the farm.
In other to improve on the traditional methods used by farmers in processing harvested carrots,
various researchers have looked into ways of designing machines which could manually or
automatically wash harvested carrots with minimum constraints. Oladip et al. (2014) worked on a
continuous processing multi-crop washing machine for seeds. The machine is an improvement on
existing batch melon washer developed by the National Centre for Agricultural Mechanization,
NCAM. Kenghe et al. (2015) worked on a mechanical fruit washer. Washing of produce can be
carried out by immersion or non-immersion by spray/showers or by combination of the two
process. (Kenghe et al., 2015)
2.1 Immersion wash system
This system is an effective and simple method of washing root crops (carrots). It involves
immersing the crop directly into water. It is normally preferred for processes requiring extended
soaking time because of the type of contaminate to be removed or the shape of the part. Le–Bohec
(1993) stated that conventional washing methods for carrots, consisting of rotary washing systems
6
in which carrots are not immersed, tend to damage carrots. The root crop (carrot) washing machine
for immersion type of washing consist of a perforated washing drum with perforation or horizontal
hole mounted about a horizontal axis. It has a water trough mounted beneath the washing drum for
partial immersion of the drum. This type of system makes use of no sprayers hence makes it simple
and less expensive.
2.2 Non-immersion system
This system involves spraying of the produce with water. It comprises of a washing drum mounted
about a substantially horizontal axis. The washing drum is of perforated material or of slatted
construction and is usually driven by drive rollers or pinion gears. Water is applied to the produces
in the drum using spray nozzles. The water is sprayed under high pressure onto the produce in the
drum. The shape and arrangement of the nozzles and the spray force have a major influence on the
degree of cleaning that is provided in this system. The efficiency of a spray of water for washing
depends upon the pressure of the water, its volume, and also the distance of the spray nozzle from
the vegetable to be washed (Diamante, 2007). According to Antony (1987) a product that is heavily
contaminated with soil should be thoroughly soaked in water to loosen the soil before passing it
under sprays. Jayashree and Viswanathan (2010) reported that the bruise index of produced
increased with increase in operating drum speed for washing of ginger rhizomes.
2.2.1 Commercial Washer
The most common proposed design by researchers is the non-immersion rotary washing type
system. Mandenshall et al. (1988) discussed several ways in which vegetable can be washed with
7
principles similar to common washing machines such as an automobile washer, household dish
washers etc. Most commercial washers are designed based on the rotary drum system.
Stark et al. (2000) worked on a commercial carrot washer whose cylindrical washer had a length
of 5m (16.4ft) and a diameter of 0.9m (2.95ft). The design had a full length spray bar to supply
water in the drum. The design make use of 4 rollers with 600kg (1320Ib) capacity each and operate
at a speed of 12 to 13 rpm by means of 7.5KW (10HP) electric motor.
This commercial washer, although very useful, is cumbersome and expensive which makes it
difficult for most farmers to purchase and unsuitable for small scale farmers to use due to their
large capacity.
2.2.2 Small Scale Washer
In order to develop a simple and affordable washer, Moss et al. (2012) developed a low mechanical
carrot washer which has a cylindrical barrel made of a high density polyethylene (HDPE) unlike
the design by Ravdeep et al. (2014) and our proposed design which is made of wood planks. The
cylindrical barrel has a length of 0.86m and a diameter of 0.58m. Slots are provided along the side
of the barrel to provide drainage.
The barrel has it outside wrapped with a rubber belt which is 0.46m wide and 1.85m long to provide
friction between the barrel and the drive rollers. Within the barrel is a center pipe for spraying
water unto the sample (Mandenshall et al., 1988). A V–belt transfer’s power from the hydraulic
motor to the pulley on one of the roller and the roller is powered by means of 0.75kw electric
motor (Ravdeep et al., 2014).
8
The design, construction and operation of the mechanical washer by Moss et al. (2012) pose
inherent hazards of entanglement of bodily parts, slippage, electrical shocks etc. For instance, the
design of the linkage between the barrel and the roller pose risk of slippage and, also, there is the
possibility of the barrel creeping off the roller as a result of no guide provided to support the barrel.
2.2.3 Manually Operated Washer
In order to ensure simplicity of design and to provide convenience in using the mechanical washer
at places where there is no electricity, Ambrose & Annamalai (2013) designed a manually operated
washer for carrots.
The washer is made of a stainless steel washing drum of length 470mm and a diameter of 390mm,
a detopper and a center shaft with fine holes for spraying water. The drum has a chute of 20 mm
length and a slope of 84° for feeding the vegetables. The washing drum was provided with different
matting namely 5 mm thickness rubber, 1.5 and 3.5 mm thickness plastic, respectively for effective
cleaning of the vegetables. Le–Bohec (1993) tested designs involving carpeting as a way to reduce
carrot breakage and improve the storage characteristics of carrots.
Figure 3.1
Figure 3.1 small scale carrot washer by Moss et al. (2012)
9
The design by Ambrose & Annamalai (2013) could only accommodate samples up to 10kg and
also the material (stainless steel) selected for the washing drum will increase the cost if larger
capacity is to be constructed, which will make most small scale farmers unable to purchase
2.2.4 Wooden drum
The design using wooden drum as the washing system is seen as the appropriate design used by
indigenous farmers due to the fact that wood is a locally available material and it is less expensive.
The wooden washer drums are made of wooden planks with even horizontal spacing between them
for the passage of contaminated water all along its circumference. A hollow shaft or pipe runs
along the center of the drum. This shaft/pipe has holes on it for sprinkling pressurized water inside
the drum (Ravdeep et al., 2014). The shaft is mounted on bearings on both sides and rotates with
the drum. The drum is rotated by hand or means of a high torque hydraulic motor. A V–belt
transfers power from hydraulic motor to a pulley on a roller (Moss et al., 2012). Water is pump
into the hollow shaft through a pipe or by gravity.
10
CHAPTER 3
3.0 MATERIALS & METHODOLOGY
3.1 Materials selection
The cost, availability, properties and weight of the materials were some of the major factors
considered for the selection of material for each of the machine component. Table 3.1 shows the
summary of the material selected for each machine component.
Table 3.1 summary of the materials selected
MACHINE COMPONENT
MATERIAL USED SIZE/TYPE QUANTITY
REASONS FOR SELECTING THE MATERIAL
Wash drum Wood plank (red wood) 6500mm×50mm×25mm
25 Readily available Low cost
Steel metal sheet 5mm thickness
1 Readily available
Counter sunk screw & nut
6mm 50 Low cost
washer NA 50 Readily available Frame mild steel square pipe 1¼ inch 2ft. Good tensile
properties Water trough Galvanized steel sheet 1.5mm
thickness 1 Excellent corrosion
resistance Spraying
system Aluminium pipe Ø 10mm 1 Excellent corrosion
resistance Garden hose Rubber 1 ft. 1 Low cost Pipe to hose
connector Aluminium 80 mm 1 Low cost
Bearing NA UCP 203 2 Resist corrosive environment
Paddle Steel 200mm 1 Readily available
11
3.2 Cost Analysis
3.2.1 Material Cost Estimation
It is the overall amount needed to acquire the raw material which has to be processed or fabricated
to desire size and functioning of the components. These materials can be divided into two
categories.
3.2.1.1 Material for Fabrication
Here, the material in obtained in raw condition and is manufactured or processed to finished size
for proper functioning of the component.
3.2.1.2 Standard Purchased Parts
These are the materials that are readily available in the market and do not need to be fabricated.
Examples are the pillow ball bearing, bolts & nuts
3.2.2 Machining Cost Estimation
This cost estimation is an attempt to careful forecast the total expenses that may include
manufacturing, labor, materials etc.
3.2.3 Calculation for Material Cost
The general procedure for calculation of material cost estimation is: After designing a project a
bill of material is prepared which is divided into two categories.
I. Fabricated components.
II. Standard purchased components.
12
The cost of the items used in the fabrication of the design is based on 2016 Ghana price.
Components generally available from local hardware or retailers. Table 2. Shows a summary of
the cost of the component parts of the machine.
TOTAL: GH¢ 470.10
ITEMS QUANTITY COST PER-UNIT (GH¢) TOTAL COST
Pillow ball bearing
2 30.00 60.00
Bolts & nuts (12mm)
4 1.50 6.00
Bolt & nut (6 mm)
4 0.80 3.20
Paddle
1 15.00 15.00
Shaft
2 20.00 40.00
Mild steel square
pipe 1¼ inch 2 feet 30.00 60.00
Screws with nut
50 0.30 5.10
Pipe to hose
connector
1 5.00 5.00
Door handle
Ι 2.00 2.00
Galvanized steel
1
2sheet
90 45.00
Garden hose
1 10.00 10.00
Clips
2 1.00 2.00
Transportation
50.00
Paint
2 10.00 20.00
Workmanship
1 100.00 100.00
Wood planks
25 1.80 45.00
hinge 2 0.90 1.80
Table 3.2 Summary of the cost of component parts
13
3.3 Design consideration
A variety of factors were considered in the design process of the carrot washing machine, some of
which are:
1. The relevant physical and mechanical properties of carrots were determined and obtained
from literature.
2. The machine was design to be relatively cheap and be within the buying capacity of small
scale farmers.
3. The material used for the fabrication are readily available materials and are locally sourced.
4. The wood selected for the construction of the drum is of a variety which can withstand
water
5. The maintenance and repair of the machine can be carried out with ease.
6. The dimensions, speed, capacity and efficiency of the machine were considered
3.4 Carrot
The physical and mechanical properties of carrots were obtained from literature. Table 3.3 shows
the physical properties of carrot. (Ambrose & Annamalai, 2013).
Table 3.3 summary of the physical properties of carrot
14
3.5 Description of the machine
The component parts of the carrot washing machine are the drum, water trough, frame, bearing,
spraying system (pipe with holes), paddle, shaft, bolts & nuts, screws and circular metal disc with
a flange. One unique feature about this design is that it provides the user an option to choose
whether to use immersion or non-immersion wash or both process.
The wash drum is made of wood planks of dimensions 650mm x 50mm x 25mm with an even
horizontal spacing of about 4mm to 8mm between them for the passage of contaminated water
and, also, running through the center of the drum is the water spraying system which provides
pressurized water onto the produced in the drum. The water trough is located beneath the drum for
partial immersion of the drum. In the case of the non-immersion, the pipe is used to sprinkle
pressurize water onto the produced. The pipe has small holes, running along it length, having
diameters ranging from 2mm to 3mm drilled on it for spraying. The holes are used in place of
nozzle to minimize the cost of design. For the immersion wash, the water trough which is beneath
the drum is used for the partial immersion of produced.
The system is design such that in both cases, excess water can be collected and re-used for other
purposes such as irrigation. The drum rotates freely on a shaft by means of a pillow block ball
bearings. Rotation of the drum is done, manually, by driving a stirring/paddle provided on one end
of the drum. The whole system is supported by the frame which is made of mild steel square pipes.
15
Figure 6.1 isometric view of the carrot washing machine
16
ORTHOGRAPHIC VIEW OF THE CARROT WASHING MACHINE
3.6 Main components
The carrot washing machine consist of four main components as follows: wash drum, main-
frame, water trough and shaft
3.6.1 Washing drum
The washing drum is made up of wood planks each having a dimension of 650mm x 50mm x
25mm. The wood planks are fastened onto a circular disc having a flange by means of a
countersunk screw. The rotation of the drum causes the carrots to move to and fro within the drum.
Figure 6.2
17
This further causes the carrots to rub against each other and also against the wood planks resulting
in effective washing.
Figure 6.3 wash drum
ORTHOGRAPHIC VIEW OF THE WASHING DRUM
Figure. 6.4 Metal disc
Figure 6.3 Figure 6.4
Figure 6.3.1
18
3.6.2 Main frame
The main frame is the skeletal structure of the carrot washing machine on which all other
components are mounted. In this work, two factors were considered in the determination of the
material required for the frame, they are the weight and strength .A mild steel square pipe was
used to construct the frame. The frame is of trapezoidal shape.
ORTHGRAPHIC VIEW OF THE FRAME
Figure 6.5
Figure 6.5.1
Figure 6.5 fabricated frame
19
3.6.3 Water trough
The water trough is in the form of a semi-cylinder made of galvanized sheet of 1.5mm having a
diameter of 470mm and a length of 720mm. It serves the purpose of holding water for washing the
carrots in the drum and also serves as a channel through which contaminated water passes to the
outlet in the case of non-immersion wash. It is situated beneath the washing drum and it is fastened
onto the frame by means of bolts and nuts.
ORTHOGRAPHIC VIEW OF THE WATER TROUGH
Water trough
Figure 6.6
Figure 6.6.1
20
3.6.4 Shaft
The design consists of two shafts (i.e. a hollow shaft and a solid shaft) which are welded to the
center of the metal disc on each end of the drum and are supported by bearing onto a frame. A
paddle is mounted onto the solid shaft and a pipe is passed through the hollow shaft to run through
the center of the drum.
ORTHGRAPHIC VIEW OF THE HOLLOW SHAFT
Figure 6.7 hollow shaft
Figure. 6.7.1
Figure 6.8 solid shaft
21
ORTHGRAPHIC VIEW OF THE SOLID SHAFT
Figure 6.8.1
22
3.7 The Prototype
The prototype was built and tested at the agricultural engineering workshop at University of
Ghana.
3.7.1 Principle of operation of the machine
The muddy samples are dumped gently into the wash drum through a door provided on the
circumference. A tap which is provided to regulate the spray of the water is opened to allow water
to be sprayed onto the carrot. In the case of the immersion type of wash, the trough provided
beneath the drum is filled with water to a reasonable quantity such that when samples are placed
in the drum they come into contact with the water in the trough. In both method, the drum is set to
rotate by manually rotating a paddle provided. The rotation of the drum which causes produce to
move to and fro within the drum and the water supply clean the carrots from soil and other foreign
materials
(A) (B)
Figure 6.9 fabricated carrot washing machine
23
3.8 Design calculation & mathematical formulas
Volume of the wash drum =πr2l …………………………………….eqn. (1)
The volume of the drum was calculated using eqn.1
=π× (0.40m) 2× (0.65m)
=0.326m3
Where l = length of the drum
r=radius of the drum
Volume of the trough = 𝟏
𝟐πr2l…………………………………………eqn. (2)
The capacity of the water trough is computed using eqn. 2
=1
2π× (0.25m) 2×0.75m
= 0.0736m3
Washing efficiency
Efficiency=𝑤𝑒𝑖𝑔ℎ𝑡 𝑏𝑒𝑓𝑜𝑟𝑒 𝑤𝑎𝑠ℎ𝑖𝑛𝑔
𝑤𝑒𝑖𝑔ℎ𝑡 𝑎𝑓𝑡𝑒𝑟 𝑤𝑎𝑠ℎ𝑖𝑛𝑔 × 100.......................................eqn. (3)
The washing efficiency of the machine is computed using equation 3.
24
3.8.1 The shaft design calculations
Assuming the wooden drum and the two metal disc has a load of (Wd) =100N and loaded with
carrots (Wc) of 120N. Hence the safe load acting on the shafts is W=P=Wd+Wc =220N .The shafts
are supported by two pillow ball bearing. Since the load will be shared equally by the drum, half
the section of the drum is considered for the calculation of the moment. The Figure 7.1 below
shows the shaft and its dimensions.
Figure. 7.2 (a) shows half the section of the drum and (b) shows the free body diagram and the
forces acting on it
Figure 7.1 dimensions for the shaft design
(A)
(B)
Figure 7.2 Free body diagram of the drum and the shaft
25
Assumptions are made for W1, W2, W3 and W4.
At B-E
• Moment = -P×BE+ [-W1× (CE+0.5BC) +-W2× (DE+0.5CD) +-W3×DE× (centroid of load
from E)]…………………………………………………………….eqn. (4)
AT F-G
• Moment = -W4 × (RF+0.5FG)………………………………….….eqn. (5)
The shaft which is made of mild steel is assumed to rotate at 12 rpm. The shaft here is subjected
to both bending moment and torsional stresses. The ultimate shear stress of a mild steel shaft
from design data is 265Mpa. The safe load is 220N (22Kg) but will be carried equally by both
shaft. The shaft of length 110mm (0.11m) is subjected to bending moment and torsion stresses.
The maximum torque (Mt) can be calculated using the following equation:
Torque = W × R, Khurmi and Gupta (1984)……………………………..eqn. (6)
Where W= force needed to cause drum to rotation (N)
R = radius of the paddle (m)
= 220N ×0.2m
= 44N-m
By compensation, then the maximum torque equal to 50N-m
Using maximum shear stress theory
D3= (16
𝑛𝜋𝑠𝑠√(𝐾𝑏𝑀𝑏)2 + (𝐾𝑡𝑀𝑡)2 Khurmi and Gupta (1984)………….eqn. (7)
D = Shaft diameter,
Ss = Allowable shear stress for steel= 40×106N/m
26
Kb= combine shock and fatigue factor applied to bending = 3
Kt = combine shock and fatigue factor applied to torsional = 3
Mb = Maximum bending moment (N-m),
Mt= Maximum torque (N-m). There are no forces acting on the shaft except the weight of the drum
and produced.
The diameter of shaft taken is 20 mm which is safe.
𝑃𝑜𝑤𝑒𝑟(𝑃) =2𝜋𝑁𝑇
60………………………………………………………eqn. (8)
P= power required (kW)
N=number revolution of the drum per seconds
T = Torque transmitted in N-m,
Power is calculated using equation 6.
𝑃𝑜𝑤𝑒𝑟(𝑃) =2×𝜋×(12)×44
60
= 0.060kw
3.9 Design of Bearing
Depending upon the nature of contact UCP 203 pillow ball bearing has been chosen.
27
CHAPTER 4
4.0 RESULTS & DISCUSIONS
Tests were conducted on the machine to ascertain its performance. The manually operated carrot
washing machine was put to test against two labourers in the agricultural fields at Weija. Both the
carrot washing machine and laborers were given some quantity of harvested carrots and the time
taken by each of them were recorded corresponding to the quantity of carrot washed by hand
(sponge and water) and for the machine The results were recorded and a graph of time as against
quantity is plotted as shown in figure 9.1
Table 4.1 Time taken by labourers and the machine to wash carrots
Number of
carrots
Time (seconds) taken to
wash samples by labourers
Average time
(seconds) taken by
the labourers
Time taken to wash
carrots by the
machine T1 T2
10 60 75 67.5 39
20 140 170 155 56
30 149 180 164.5 59
40 223 260 241.5 60
50 271 310 290.5 66
60 310 365 337.5 69
70 351 408 379.5 NA
80 384 440 412 NA
28
Figure 9.1 graph of time as against carrot quantity.
4.1 Testing for efficiency
The initial weight of the carrots were first determine before placed into the carrot washing machine
to be washed. This was done at the university of Ghana physic laboratory using an electronic
balance. The weight were again determine after washing with the prototype and the corresponding
efficiencies are tabulated as shown in table 4.2.
67.5
155 164.5
241.5
290.5
337.5
379.5
412
39
5659 60
6669
0
10
20
30
40
50
60
70
80
0
50
100
150
200
250
300
350
400
450
0 10 20 30 40 50 60 70 80 90
Tim
e ta
ken
to w
ash
sa
mp
les
by
th
e
mach
ine
(seco
nd
s
Tim
e ta
ken
to
wash
sam
ple
s b
y h
an
d
(seco
nd
s)
quantity of carrots
Graph of time vrs quantityTime taken by hand
Time taken by the machine
Figure 9.1
29
Number of carrots Weight before
washing(g)
Weight after
washing (g)
Washing efficiency
10 152 135 0.89
20 244 224 0.92
30 358 338 0.94
40 473 452 0.96
50 610 589 0.97
60 750 736 0.98
(A) (B)
Figure 9.2 determination of the initial weight of the carrots
Table 4.2 summary of weighing results
Samples of unwashed carrots Weighing samples using an
electronic balance
30
4.2 Effect of Drum speed on Washing Efficiency
The washing efficiency of the carrot washing machine were recorded by varying the drum speed
for 10rpm, 11rpm, 12rpm, 13rpm and 14rpm. It was observed that higher (97.4 %) efficiency was
recorded for 13 rpm and Lower efficiency (89.1%) was recorded for 10 rpm. It was also observed
that drum speed at 14rpm there were some bruises.
Revolution per minute (rpm) Efficiency (%)
10 89.1
11 96.8
12 97.4
13 98.4
Table 4.3 Effect of the drum speed on washing efficiency
31
CHAPTER 5
5.0 CONCLUSION AND RECOMMENDATIONS
5.1 CONCLUSION
From the graph in figure 9.1 the machine proved to be more time efficient as compared to the
traditional method of washing. The average efficiency of the machine was found to be 94.3%.
Increasing the speed of the drum beyond 13rpm resulted in an increase in bruises. An efficient
wash with minimal bruise index was achieved when the revolution per minute of the drum was
between 12 to 13rpm.
5.2 RECOMMENDATIONS
Despite the appreciable performance of the carrot washing machine in terms of machine efficiency
and time, I will recommend that:
1. The carrot washing machine should be motorized so that farmers who cannot rotate the
drum manually can use it.
2. The inside of the drum should be mated with an appropriate material to improve the
washing efficiency.
3. Farmers should use both the immersion and non-immersion during washing to conserve
water and also for effective wash.
32
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