Design of a manually operated mixing machine for
Shea Butter applications
ENGR 481 - Senior Design
Final Report
Sponsors:
Shea Yeleen International Inc.
Mr. Larry Matthews
Faculty Advisor:
Dr. Camille George
Team Members:
Amber Beck
Nick Dalbec
James Zoss
School of Engineering
University of St. Thomas
May 2005
Abstract
The women in Mali, North Africa lack the efficient tools and education to develop a
better means of processing Shea butter products. The current processes are physically
exhausting and time demanding, taking several hours to complete. Women consume
their products as well as sell them at the local markets. Shea butter is becoming
internationally known as a skin care product used for moisturizing. In order to help
African women establish fair-trade Shea Yeleen International, a non-profit organization,
was founded. This project seeks to develop a better means of mixing using a manually
operated machine. After thoroughly researching, designing and experimenting, a final
machine was developed optimizing the mixing process. The mixing time was
successfully reduced form several hours to thirty minutes. All other engineering and
customer design requirements were met. Through the success of our design, Shea Yeleen
International will be able to disseminate the machine and hopefully help fight poverty in
Africa.
Table of Contents
I.
Team Member Assignments…………………………………………………1
II.
Background of Shea Yeleen International………………………………….2
III.
Project Background………………………………………………………….3
IV.
Mission Statement……………………………………………………………4
V.
Customer and Engineering Requirements…………………………………5
VI.
Project Management………………………………………………………...8
VII.
Product Cost Analysis………………………………………………….…..10
VIII. Engineering Budget……………………………………………………...…12
IX.
Concept Generation………………………………………………………...14
X.
Prototype Progression……………………………………………………...17
XI.
Manufacturability…………………………………………………………..22
XII.
Testing Results……………………………………………………………...22
XIII. Temperature and Water Dependence……………………………………..26
XIV. Final Design Evaluation....………...……………………………………….28
XV.
Conclusions………………………………………………………………….29
XVI. References…………………………………………………………………...30
XVII. Appendices
Appendix A: Gantt Chart
Appendix B: Blade Concept Analysis
Appendix C: Scale Reduction Testing
Appendix D: Power Source Concept Analysis
Appendix E: Procedure/Assembly
Appendix F: CAD Drawings
I. Team Member Assignments
Amber Beck: Team Leader
Midterm Presentation, Project Management, Gantt chart, Testing procedures, Final Paper
Nick Dalbec
Manufacturing Prototype, Bill of Materials, Project Budget, Cost Analysis, Testing
Procedures
James Zoss
Computer Animated Design (CAD), Testing Procedures, Manufacturing, Prototype
Evaluation
1
II. Background of Shea Yeleen International
Shea Yeleen International (SYI) is a nonprofit organization that was founded in
March 2003 by Rahama Wright1 . The organization hopes to encourage community
development and the possibility for fair trade of shea butter products. In Africa, Miss
Wright engaged a small group of educated Malians to explore the possibilities of
marketing shea butter. Local women cooperatives have been developed with a mission to
create a sustainable business. The central focus of SYI is to assist West African women
with obtaining the necessary tools and education to produce shea products. These
products can then be sold internationally and help the women fight against poverty.
2
III. Project Background
Malian women use shea butter for many daily applications as well as a source of
income. Their current production method is physically demanding and lacks in quality
and efficiency. Without standard steps to follow or guidelines for procedure, the current
process is difficult to replicate. After collecting nuts the women must clean and de-shell
them. The nuts are then roasted, ground into a paste, and kneaded. The oils separate out
through kneading, and the paste is then filtered. The oil portion is left out to cool over
night resulting in the final product. The focus of this project is to improve the current
Malian kneading process. On average, kneading by hand takes hours to complete2.
From a social perspective, the Malian communities are very poor. The average
Malian makes less than two dollars a day, and this income must cover the cost of
medicine, food, and clothing for an entire family. Women work very hard in these
communities to maintain the health of their families. Culturally, the Shea nuts belong to
the women, thus making Shea butter an area where women can gain more economic
freedom3.
3
IV. Mission Statement
Our goal is to design a Shea butter mixer that will benefit the Mali community by
reducing the Shea butter mixing time and increasing production of Shea butter for fairtrade.
4
V. Customer and Engineering Requirements
1 Materials obtainable in Mali
2 Non-corrosive materials
3 Safe to use
4 Easy to operate and clean
5 Simple to manufacture and maintain
6 Cost effective
7 Produce quality product
Table 1: Customer Requirements
1
Cost less than $100
2
Fabrication reasonable for local craftsmen
3
Open container for easy access
4
Material of blade/container must be non-corrosive
5
Material of power source parts must be plastic, steel, or wood
6
No complex transmission or gear setup
7
Easy to clean parts
8
No sharp edges or rotating parts exposed
Table 2: Engineering Requirements
5
The final product is going to Mali, North Africa and may also be used in other
African countries. With this in consideration, the final product has a target cost of $100
US or less.
The mixer design will be affordable and parts will be available from local
markets. There are basic hardware stores and machine shops in Mali, but prices vary
because of shop owner and customer bartering. The mixer will be manufactured from
commonly available materials and should not use a custom manufactured container.
Fabrication should be reasonably simple, using methods of cutting and welding that a
local Malian machine shop can perform.
There are few tools for everyday use, so assembly and maintenance must be
reasonable for a typical Malian in the local community. The machine will have minimal
moving parts. The simplicity of the design will allow for quick and simple repairs.
Machine drawings and instructions will be provided for Shea Yeleen International
contacts in Mali to enable local fabrication.
The container must be open so water can be easily added to the paste. The design
must use stainless steel or plastic to provide protection from corrosion. In order to
prevent contamination of product and mold growth, the machine will be easy to clean.
The mixer should not be damaged by environmental conditions, insects or other pests.
There will not be any toxic materials associated with the mixer, so it will not pose any
environmental threat to the people. The design will be safe for the user, with no sharp
edges exposed.
The mixer will be manually powered with the possibility of alternative forms of
power. The motion of the manual power source will be less physically exhausting then
6
the current processing. Current mixing processes take several hours to complete; the new
machine will reduce this time as much as possible.
Groups of Malian women will form cooperatives where they can have access to
the mixing machine. The machine shall produce enough Shea butter products for
personal consumption and to sell in local and international markets, thus providing an
opportunity to earn a regular source of income.
The mixer will improve oil extraction and increase the product inventory for the
local Malian women. This project should have a positive impact economically and
financially on the people of Mali. There will be culturally appropriate training materials
in French and Malian languages supplied along with the final design. Illustrations will
accompany the training materials to show operation techniques. The final design will be
sent to local Shea Yeleen International contacts to continue implementation of the
machine. Table 3 shows how the engineering requirements relate to the customer
requirements.
7
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Engineering Requirements
Local Materials
Non-Corrosive
Safe
Customer
Easy to Use
Requirements
Simple Design
Cost Effective
Quality Control
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Table 3: Customer Requirements vs. Engineering Specifications Matrix (QFD)
VI. Project Management
Tasks for the project were divided equally among the three team members.
Manufacturing was completed by Nick and James, while Amber managed the tasks and
deadlines of the project. Many of the experiments were conducted with at least two
members present and each team member was responsible for taking observations and
developing design ideas. Regular team meetings were held to discuss shortcomings and
progress of the project. A Gantt chart can be found in Appendix A displaying the
individual task assignments and deadlines. This chart was used to guide the team and
assure timely completion of the project. Each experiment provided insight for the project
and so Gantt chart was updated regularly with new tasks to accomplish.
8
Preliminary
Research
Experimenting
& Design
Blade Concept
Testing
Project Selection
Shea Nuts
Meet Team
Members
Current Production Miniature Scale
Methods
Model Testing
Prototype
Testing in
Mali
Horizontal Hand
Crank
List of Supplies
Hand Bicycle
Design
Travel to Mali
Final Design
Address Design
Issues
Other Methods of
Meet with Advisor Oil Extraction
Container Testing
Hand Drill Power
Source
Modify
Send out
Observed Current Procedures to
Processes
liaisons
Set-Up Schedule
Containers
Phase Test
On-Site Design
Testing in Village
Contact Liaisons
Blade Designs
Temperature
Analysis
Final Design
Adjust Machine
Power Source &
Transmission
Purchase New
Parts
Shea Butter
Journal
Testing in Village
Nigerian Thesis
User Survey
Substitute Product
Table 4: Work Breakdown Structure
9
VII. Product Cost Analysis
Bill of Materials in United States
Material
4"x 4" x 10' Pine Post
2"x 12" x 10' Pine Board
1/4" Threaded Rod
5/8" Washers
1/4" Wing Nuts
2.75" Screws
1/20" Stainless Steel Sheet Metal
5/8" Round Stock Stainless Steel
3/8" Round Stock Mild Steel
5/8" Bronze Oil Impregnated Bushing
3/8" Bronze Oil Impregnated Bushing
3/8" Pulley (3 39/32" pitch)
5/8" Pulley (1 29/32" pitch)
60" V-Belt 3L
1/2" PVC Pipe (Handle)
Container
Quantity
1 pc
1 pc
7 ft
15 pcs
13 pcs
20 pcs
2 lbs
1 lbs
1 lbs
2 pcs
2 pcs
1 pc
1 pc
1 pc
1 pc
1 pc
Price/Unit
$9.19 ea.
$13.95 ea.
$0.23 /ft
$0.06 ea.
$0.13 ea.
$0.05 ea.
$2.00 /lb
$2.00 /lb
$0.40 /lb
$1.56 ea.
$0.47 ea.
$6.52 ea.
$3.62 ea.
$6.58 ea.
$0.15 ea.
$10.00 ea.
Total Material Cost Per Unit ($)
Total Price of Material ($)
$9.19
$13.95
$1.61
$0.90
$1.69
$1.00
$4.00
$2.00
$0.40
$3.12
$0.94
$6.52
$3.62
$6.58
$0.15
$10.00
$65.67
Table 5: Bill of Materials (US)
The overall cost per unit is under $70 US, which meets the design requirement of
$100 US.
10
The cost in Mali is under $50, but will vary depending on the village and
availability of parts.
Bill of Materials in Mali, Africa
Material
8cm x 8cm x 1m
8cm x 30cm x1m
1/4" Threaded Rod
5/8" Washers
1/4" Wing Nuts
2.75" Screws
1/20" Stainless Steel Sheet Metal
5/8" Round Stock Stainless Steel
3/8" Round Stock Mild Steel
5/8" Bronze Oil Impregnated Bushing
3/8" Bronze Oil Impregnated Bushing
3/8" Pulley (3 39/32" pitch)
5/8" Pulley (1 29/32" pitch)
60" V-Belt 3L
1/2" PVC Pipe (Handle)
Container
Quantity
3 pcs
3 pcs
2m
15 pcs
13 pcs
20 pcs
2 lbs
1 lbs
1 lbs
2 pcs
2 pcs
1 pc
1 pc
1 pc
1 pc
1 pc
Price/Unit
$1.70 ea.
$3.20 ea.
$1.80 /m
$0.04 ea.
$0.15 ea.
$0.07 ea.
$3.00 /lb
$3.00 /lb
$0.40 /lb
$1.00 ea.
$0.50 ea.
$2.10 ea.
$2.10 ea.
$5.00 ea.
$0.40 ea.
$3.00 ea.
Total Price of Material ($)
$5.10
$9.60
$3.60
$0.60
$1.95
$1.40
$6.00
$3.00
$0.40
$2.00
$1.00
$2.10
$2.10
$5.00
$0.40
$3.00
Total Material Cost Per Unit ($)
Labor
Fabrication of Blades
Welding Blades
Fabrication of Handle
Hrs
0.35
0.25
0.15
$47.25
$US/hr
$3.00
$3.00
$3.00
Total
$1.05
$0.75
$0.45
Total Labor Cost per Unit ($)
$2.25
TOTAL COST PER COMPLETE UNIT ($)
$49.50
Table 6: Bill of Materials (Mali)
On-site we were able to redesign and develop the machine using the tools and
materials locally available. Through purchasing items locally we were able to get an
accurate cost analysis of the machine and it was evident that our new design could be
manufactured in Mali.
While purchasing materials in Mali, it was apparent that items like wood, steel,
pulleys and belts were easily obtainable. These items were common and cost efficient.
11
Stainless steel was more difficult to find and more expensive to purchase, however
Professor Ouane at the Ecole Nationale d’Ingenieurs assured us that stainless steel can be
obtained at an affordable price. He also helped establish prices for non-regular items (i.e.
bushings, pulleys, belts, stainless steel). The design requirements of cost, non-corrosive
materials and safety were all met using the items discussed above.
The fabrication shop rates varied depending on if you were in the village or in the
city. The local craftsman determined his own price depending on the complexity and
demand for his labor. In the village, a local craftsman charged only 500CFA (about
$1.00) for welding, grinding, and re-work required of the blades and shaft for 20 minutes
of his time. Therefore, an average shop rate of $3/hr in Mali, Africa was calculated.
VIII. Engineering Budget
1st Semester
Labor
Associate Engineering Hours
Consulting Engineering Hours
Materials
Testing Medium
Laboratory Equipment Use
Steel
Fabrication
First Semester Total
Hours
Cost
440
35
$11,000.00
$1,750.00
$15.00
$100.00
$10.00
$25.00
$12,900.00
12
2nd Semester and J-term (excludes trip)
Labor
Associate Engineering Hours
Consulting Engineering Hours
Hours
Cost
390
25
$9,750.00
$1,250.00
Materials
Pulleys, Belts, Bushings
Screws, threaded rod, nuts washers
Lumber
Stainless Steel, Mild Steel
Container
$15.00
$5.00
$63.00
$97.00
$10.00
Second Semester Total
$11,190.00
Trip Costs
Labor
Associate Engineering Hours (in Africa)
Consulting Engineering Hours (in Africa)
Trip Planning Assoicate hours
Trip Planning Consulting hours
Plane Tickets, Hotels, Meals, transportation
Out of Pocket expense
Total Trip Expenses
Accumulated Project Total:
Hours
Cost
252
80
60
25
$6,300.00
$4,000.00
$1,500.00
$1,250.00
$10,000.00
$1,500.00
$24,550.00
$48,640.00
Table 7: Budget
The first semester budget is broken down into two major parts: labor and
materials. The team consisted of four associated engineers, putting in ten hours a week
for eleven weeks. The salary was calculated at $25 per hour based on a $50,000 entrylevel engineer. Consulting hours consisted of Dr. George, Harry Gebbens, and contacts
from Shea Yeleen International. Their salary was estimated at $100,000 per year at $50
per hour.
13
The materials purchased first semester consisted of parts for fabrication and shop
tools used. All other parts and components used for experimenting were accounted for.
The total cost for first semester was: $12,900.
The second semester and J-term budget consisted of everything except the March
trip to Africa. Three associate engineers remained on the team after first semester.
During J-term only two associates were able to work on prototype development and
testing. Associate hours for J-term and second semester totaled 252 hours. The total cost
for second semester and J-term was: $11,190.
The trip to Mali contributed to almost half of our budget. Three engineers and
one consulting engineer (Dr. George) were considered as part of the trip cost (tickets,
hotels, food) at $2,500 per person. Other expenditures were accounted for such as: travel
agencies, booking fees, materials, translators and preparations for departure. A $500
travel fee paid by each of the three associated engineers was also included in the budget
report. The total cost for the trip to Mali was: $24,550. The project total throughout the
entire year totaled to $48,640.
IX. Concept Generation
The method of mixing used by women in Mali is to mix by hand. Most often the
container holding the paste is placed on the ground, and women stand over the bucket and
bend at the waste. Not only is mixing by hand tiresome and time consuming, but the
bending can cause strain on the back, making the process only suitable for younger
women. In order to ensure an efficient development of all aspects of the project the
14
mixer was separated into three main components: blades, container, and power
source/transmission.
Blade Concept Designs
Proof of Concept Testing
The first step in selecting a blade design was proof of concept testing. For this,
five different blade designs were constructed and tested by a visual inspection of mixing
food coloring into a mixture of flour and water. From this testing, the helical blade
inspired by an auger and the hollow blade inspired by kitchen mixers were found to be
inadequate. More information about blade selection can be found in Appendix B.
Scale Reduction Testing
During the months of January and February, more testing was performed. Scale
models of the three best performing blade designs from the proof of concept testing were
produced. This was done so that they could be tested with the limited supply of actual
shea paste that was available. After testing, it was found that the asymmetrical blades
were able to extract oil most efficiently. More information on scale reduction testing can
be found in Appendix C.
Power Source Concepts
There were two main power source concepts tested. A discussion of other power
source possibilities can be found in Appendix D.
15
Hand Crank
The hand crank consists of an offset vertical shaft directly connected to the blade
via a horizontal link. It is a simple and effective way of rotating the shaft. One problem
is that it can be quite difficult to rotate the shaft.
Hand Bicycle
This idea was originally derived from a standard bicycle drive system. The
concept was adapted to a hand powered style to accommodate for the preferred range of
motion for the Malian women. The hand bicycle concept is composed of two handles on
opposite sides that rotate horizontally around a fixed point. A gear or pulley is placed
between these handles for the accompanying transmission of power. A gear ratio can
easily be applied to reduce the amount of energy required to turn the crank. This power
source can be manufactured simply through then bending of round bar. A person could
use one or both handles for manual power, or two people could use the opposing handle
to combine their efforts.
Transmission Concepts
The first concept was to use a set of bevel gears to transfer rotation of two shafts.
This concept can be seen in many mechanical systems. This idea was mainly thought of
by the examination of differentials in automobiles. Bevel gears are a very effective way
of transferring power however, they can also be costly. This concept was discarded.
The next transmission idea was that of a twisted belt around two perpendicular
shafts. This was an idea seen by the examination of vacuum cleaner transmission. Since
16
this concept is an effective way to transfer motion while still being cost effective, it was
selected to be used as a transmission.
Container Concepts
The concepts for a container came down to two different options; a plastic bucket
or a hand made bucket. One successful shea butter processing method in Ghana uses a
hexagonal container for shea butter mixing. Our contact claims that it is the hexagonal
shape of the container that is vital for the oil extraction4. The container is custom-made
out of stainless steel in order remain non-corrosive. Stainless steel is expensive and to
manufacture a hand made container would not be as simple as buying a plastic one.
Therefore, after results of testing revealed that that oil could in fact be extracted without
the hexagonal design, we selected the plastic container. This is explained more
thoroughly in the Testing section and in Appendix C.
X. Prototype Progression
From the different experiments and proof of concept studies performed, the
plastic bucket, angled asymmetrical blades, and a horizontal bicycle style hand crank
with a twisted belt transmission were the options chosen for our machine prototype.
Materials selected for the initial prototype were based upon the implied availability and
manufacturing capabilities in Africa. The machine developed on-site in Mali used
materials and manufacturing techniques found in local markets.
Failure with our second prototype during the initial testing phase in Mali proved
to be greatly beneficial for our product development.
17
Prototype Progression:
1st Prototype
Qualities:
•
Proof of concept machine.
•
Hand crank on 5 gallon bucket.
•
Steel and wood frame.
Problems:
•
Difficult to turn.
•
No access to paste inside bucket.
2nd Prototype
Qualities:
•
Wood beam on top of 5 gallon
bucket.
•
Slotted wood crank frame.
•
Two sided bicycle style hand
crank.
•
Twisted belt.
•
Bucket and crank frame separate from each other.
18
Problems:
•
Very unstable.
•
Difficult to keep belt in tension.
•
Difficult to access contents of bucket.
•
Crank tended to come out of slots.
•
Wood beam was not anchored to bucket.
3rd Prototype
Qualities:
•
One piece frame design.
•
Wider plastic bucket.
•
Threaded bar through wood plank to
anchor bucket.
•
Two pieces of metal on either side of
threaded bar.
•
One-handed crank.
•
Longer, wider blades.
•
Crank positioned by a hole in a vertical post.
Problems:
•
Belt slipped after time.
•
Somewhat difficult to turn.
•
Two piece metal tension plates difficult to get into place.
19
•
More suited for a left handed person.
•
Bare metal crank uncomfortable on hand.
4th Prototype
Qualities:
•
Addition of tensioning thread bar and block.
Problems:
•
Somewhat difficult to turn.
•
Two piece tension plates difficult to get
into place.
•
More suited for left handed person.
•
Bare metal crank uncomfortable on hand.
•
Tension bar and block requires a vice grip
to fully tension.
5th Prototype
Qualities:
•
Larger pulley on crank.
•
Brass bushings placed in crank post.
•
Plastic handle added to crank.
•
Crank moved to opposite side.
•
Tension thread bar incorporated into shaft beam.
20
•
Single piece of metal with slot used for vertical tension bars.
•
Drilled a hole in the post for tensioning bar and added a wing nut and washer
eliminating the need for a vice grip.
Problems:
•
To produce the slot in the single piece of metal used to clamp down the container
may be difficult.
21
XI. Manufacturability
With limited availability of shop tools in the village, the final design of the
mixing machine requires minimal tools necessary for assembly. Wing-nuts are used to
reduce the need for special tools in assembling the machine. All other parts are either
hand-drilled or hand-tightened further eliminating the need for expensive tools. Screws
are used to secure wood fixtures and a screw-driver set was left in the village to ensure
the local Malians would have adequate tools for manufacturing the machine. Cutting
wood, drilling holes and alignment of parts were all done effortlessly by the local
Malians.
Welding will be completed by the local craftsmen. Working with the craftsman in
Mali, it was evident that his capabilities and skills were exceptional for the work required
to manufacture the blade assembly. Any failures or problems resulting from daily use of
the machine will be easily maintained and fixed in Mali.
XII. Testing Results
The objective of traveling to Mali was to test the mixer under real applications
and use. It was also critical to obtain user feedback to make adjustments and
improvements based on their comments. The first testing result was beneficial for the
group, providing us with crucial feedback from the local Malians. Our second and third
tests proved successful.
22
Design 1
1st Prototype
Africa
Test
Location
Environment
Conditions (in shade)
94.8 degrees F
Quantity of Shea
Paste (approx.)
10 pounds of paste
Time
(min.) Paste Temp
Paste Appearance
0
Oily, no foam present
90.6
5
92
Removed container/blades
from the base. Instability
was laborious. Attached
hand crank directly to
92.1
blades and continued the
experiment. Took
observations of container
and blade design.
10
20
89.5
25
Notice Oil in water
30
35
45
50
Stop and let mixture sit
60
70
User Comments
Not as much foam as the
woman get by hand
White foam was extracted
88
Difficult to use, base not stable, more than one
woman still required for processing, they wanted
to try a wider bucket with wider blades, the size of
their hands. Requested a machine they could sit
at.
Table 8: Observations of our first test in Mali.
The first prototype test was unstable and frustrating. We removed the pulley
transmission and attached a hand drill to the shaft of the blades to continue testing the
blade. Although the machine lacked significant stability control and was tiring for the
woman, it proved the blade configuration was successful for extracting oil.
23
The machine design for the second test was significantly improved. The design
was simple, the range of motion was comfortable and the features of a hand crank were
more desirable. Successful results were obtained after just 58 minutes of mixing the
paste.
D esign 2
B am ako Prototype
Africa
Test
Location
Environment
Conditions (in shade)
Quantity of Shea
Paste (approx.)
96 degrees F
D id not take tem p. readings of paste,
previous testing showed little to no
significant changes in paste tem p.
T ested with 10 lbs. of paste
T im e
0
5
10
20
25
30
35
45
50
55
58
User Comments
Paste Appearance
O ily and m ore viscous
com pared to test one
Added lots of water,
approxim ately 2:1 water to paste
ratio. Belt kept slipping, added
a support board to keep belt in
tension. Paste felt sticky, like
gum .
C an hear a thunking sound as
paste hits wall of container.
Paste started to feel oily and
slide against the container.
W ater drop test
Foam present, lighter in color
Added water to create better
separation
W hite foam was
extracted!
Lots of oil and water splashed onto wood,
could result in bacteria. M achine seem s
m uch faster than working by hand.
R equested the handle be placed on the
right side of post.
Table 9: Observations of the re-designed mixer in Mali.
24
The third test was conducted back at St. Thomas with our final redesigned
machine based off comments made by the local woman. After simulating the Malian
environment in a room at 85 degrees Fahrenheit, successful oil extraction was obtained
after just 30minutes of mixing.
Design 3
Final Design
United States
Test
Location
Environment
Conditions (in shade)
Quantity of Shea
Paste (approx.)
85 degrees F
5 pounds of nuts were crushed and
resulted in close to 3 pounds of paste
Time
0
5
10
20
25
30
User Comments
Paste Appearance
Warm water was added to the
paste approximately 1:1 ratio
paste to water. From Nigerian
studies and experience in
Africa we knew to add warm
water (94 degrees) Results of
Nigerian studies showed 3
parts water, but after adding
one part to our paste we
decided it would be best not to
begin with that much. There
was not a lot of paste to start
with. After 10 minutes paste
temp. was 84.6
African water drip test, WE
COULD SEE OIL!!!
Added more water
Successful white
foam extraction!
We predict they will like the more
comfortable handle height, position on
post and handle material. By using a
larger pulley less force is required for
use.
Table 3: Observations of the final design testing in the United States
25
XIII. Temperature and Water Dependence
The viscosity of shea paste is highly dependant on the surrounding ambient
temperature. A variety of tests were conducted to determine what temperature was
optimal for working with shea paste. We attempted to regulate temperature using a water
bath and space heaters; however it was difficult to maintain consistency throughout the
experiment. In order to determine the temperature the paste would experience a change
in state, a phase experiment was conducted. Results showed that the paste was
completely solid around 60 degrees Fahrenheit and did not change to be completely
liquid until around 120 degrees Fahrenheit. The conclusion was then that shea paste has
a large range where it is not completely a solid or liquid.
Shea Paste Phase Chart
130
120
110
Temperature (F)
100
90
80
70
60
50
0
200
400
600
800
1000
1200
1400
1600
1800
Time (Seconds)
Chart 1: A phase diagram of shea paste.
26
2000
Attempts to determine the optimal testing temperature were unsuccessful. Using
information from www.weather.com, we found that average temperatures in Mali were
around 90 degrees Fahrenheit and decided to test in the temperature range from 85 – 95
degrees5. While in Mali, temperature was recorded regularly and it was then determined
that the temperature of the paste does not change much during processing. The average
temperature determined on-site in the shade was 98 degrees Fahrenheit and the average
temperature of well water added to the paste was 86 degrees.
Through experimenting at the Institue d’Economie (IER) observations of
processing was noted. The addition of refrigerated water was added to the paste in small
quantities. The experiment was not successful and while cleaning out the machine it was
observed that the paste had begun solidifying on the container, shaft and blades.
Therefore, when working with shea paste, cold water (below 70 degrees Fahrenheit)
should not be added. The temperature of the water being added affects the chemical
reaction taking place in the mixing process.
Upon returning to the United States a Nigerian Thesis on shea butter had arrived.
This proved useful in determining the optimal amount of water to add when extracting oil
from shea paste. The results of experiments discussed stated that three parts water to one
part paste is most advantageous6. After the oil begins to separate, more water can be
added without concern. Our experiments with the final design of the mixing machine
supported these results.
27
XIV. Final Design Evaluation
•
The cost of the mixer meets the requirement at approximately $50.00 (in Mali).
•
All parts in contact with shea paste are made of stainless steel or plastic.
•
Disassembly is easy because it requires no tools.
o Wing nuts can be unscrewed allowing clamps to be removed easily.
o Shaft and shaft post are removed in one piece separating easily from
bucket. This allows for the easy cleaning of the mixer.
•
The mixer can accommodate many different sized containers. The use of a wide
container allows for easy access to the paste.
•
Rotating the crank at approximately 60 rpm causes oil extraction at approximately
30 minutes.
•
Oil extraction ratio of 3:1 was maintained using the mixer.
•
Operation of the mixer can be done by one woman.
o There is an option of sitting or standing while using the machine.
•
Tensioning the belt only requires the turning of a wing nut.
Benefits/Features
The final design was intended to be flexible and easy to use. The most complex piece
of the design is the blades, which consists of three different lengths of stainless steel, all
8mm wide. They are welded onto the shaft at a 45 degree angle. Fabrication of the blade
design is within the production capabilities of villages. Other parts for the machine are
available in local markets. The design is adjustable so that different container sizes can
be used. Since the setup/disassembly of the mixer requires no tools, it is easy to use and
28
clean. Mixing time is greatly reduced and the larger bucket allows for greater batch sizes
of shea butter to be produced.
XV. Conclusions
Through research and experimentation the Mali Mixer team was able to develop a
successful prototype. Using feedback from the Malian women was vital for the final
design. User comfort was kept in mind for ease of use, range of motion, and the location
of the power source. The manually powered machine met all customer and engineering
design requirements. Using the mixer, the women in Mali were able to produce twice as
much shea butter with little to no physical strain. The final design was able to extract oil
in 30 minutes, greatly reducing the average mixing time. With reduced mixing time,
reduced physical strain and an increase in batch size, production of shea butter products
will increase.
The Mali Mixer team is optimistic for the future of this project. Shea Yeleen
International (SYI) will be able to disseminate the machine and educate the local village
women in how to form cooperatives and establish fair-trade. Using the assembly
instructions and drawings provided, SYI contacts will be able to teach people how to
build, maintain, and optimize production from the machine. With the increase of shea
butter production in the villages, women will be able to sell their products and create
more income for themselves. As SYI begins working with more and more women in
Mali, the establishment of fair-trade and the fight against poverty will be set in motion.
29
XVI. References
1. Wright, Rahama; Shea Yeleen International. 280 Madison Avenue,
Suite 912, New York, NY 10016. rahamatuwright@yahoo.com
(2004).
2. http://sheabutter.web.aplus.net/id10.html (Oct. 2004).
3. http://www.un.org/ecosocdev/geninfo/afrec/vol15no4/154shea.htm
(Oct. 2004).
4. Akuete, Eugenia; motherakuete@hotmail.com (Dec. 2004).
5. http://www.weather.com (Jan. 2005).
6. Olaoye, Joshua. “Oil Recovery Process From Shea Butter Seed
Through Modified Clarification.” Thesis: April 1994.
7. Olaoye, J.O. and Babatunde O.O.; “Development and Testing of a
Milled Shea Nut Mixer.” Journal Food Science Technology, Vol. 38
N. 5 pp. 471-475, 2001.
30
XVII. Appendices
Appendix A: Gantt Chart
Located on the next 4 pages.
i
ii
iii
iv
v
Appendix B: Blade Concept Analysis
Six blade concepts were considered and compared based on given design
requirements. Five of the six blades were constructed and tested. The sixth design was
the hollow blade with inserts; it was evaluated based on extrapolated assumptions.
In addition to design requirements given by the client, engineering requirements
were added to evaluate overall performance. Each requirement was weighted according
to its contribution to the blade design. Mixing efficiency was weighted at 22.5% and was
the main focus of determination followed by cost, safety, and manufacturability.
Each blade was scored in all the design requirement categories, with a score of
five considered the best option. The data was then compiled to make the blade selection.
Two of the blade designs were close in ranking. The solid asymmetrical and solid
symmetrical were rated at 4.88 and 4.775 respectively. Based on this analysis, the design
of the solid asymmetrical and symmetrical blades will be the main focus for future
ri c
et
al
ic
el
H
H
ol
lo
lo
w
w
A
w
sy
/ In
m
se
m
rt
s
al
la
B
d
ol
H
ng
le
A
id
de
s
r ic
et
et
m
m
Sy
m
m
sy
A
So
l
lid
So
W
ei
gh
t
Pe
r
ce
nt
ri c
al
al
prototype designs.
Manufacturing Ability
17
5
5
3
2
3
1
Cost
18.5
5
5
4
5
5
4
Torque Required
12
4
5
4
2
2
4
Mixing Efficiency
22.5
5
4
3
3
2
5
Maintenance Required
12.5
5
5
4
4
4
3
Safety
17.5
Total:
Weighted Total:
100
5
5
4
5
29
29
22
21
4.88 4.775 3.605 3.555
Description
Scale
Measure by time
and tools necessary
to manufacture
5 Easy -> 1 Difficult
Material Cost and
Labor involved
5 Cheap -> 1 Costly
Measure the time it
takes to mix
5 Easy (less torque) ->
efficeintly
1 Hard more torque)
How long it took to 5 Thoroughly -> 1 Not
mix thoroughly
Thorough
5 Little to none
maintenance- > 1
How easy is it to
High Maintenance
clean parts?
How dangerous are
the parts involved?
5
3
21
20
3.5 3.415
5 good -> 1 no good
(sharp edges)
Table 1: Blade Design Results
vi
The blades have the most influence in fulfilling the requirements of efficiency and
product quality in our design. During the mixing process, the blades are in direct contact
with the Shea paste. As the blades mix water into the paste, they induce the separation of
oil.
The first step in developing blade proof of concepts was to research different
types of blades from existing technology. One project liaison is a Peace Corps volunteer
named Rahama Wright. Rahama lived in Mali for over three years and while there she
produced a video of the traditional production of Shea Butter. The information obtained
from Rahama provided a foundation for research and helped aid in defining the customer
requirements.
The video of the Malian women processing the shea paste provided a blueprint for
the mechanical mixer. In the current process, the women sit hunched over mixing in a
manner similar to kneading bread dough. Their hands are immersed in the viscous Shea
paste. Occasionally water gets added to the paste, interrupting the mixing process.
Figure 1 depicts the traditional kneading process in Mali.
Figure 1: Malian women kneading the Shea
vii
With the motion of the Malian women’s hand movement in mind, other mixing
methods were looked into for similarities. The proven mixing systems that were
researched were an ice cream mixer and a butter churn. Ice cream mixers gently mix to
keep the fluid content homogenized. This motion prevents large ice crystals from
forming while gradually extracting heat and freezing the cream. The project liaison
suggested an old-fashioned butter churn because the Malians are familiar with the motion
required for churning. Through research it was found that butter churns are simple in
design and provide agitation to dairy fluids. One butter churn was found online that had
a solid paddle blade mounted on a vertical shaft with a hand crank. This blade design
was also observed in a few of the ice cream makers and seemed simple to recreate.
Industrial mixer manufacturers were also researched. One industrial mixer for
viscous fluids employed an auger blade that rotated axially. It was diagonally mounted
on an arm that rotated the auger along side of the container. All industrial mixers were
extremely expensive and complex, most with multi-axial blades. Even though the
complexity of these mixers was out of production capabilities the auger idea seemed like
a plausible concept. It not only provided transaxial fluid movement but also axial.
Another group of industrial mixers had a propeller design with blades mounted
diagonally onto their rotating shafts. As with the helical blade, this design induced an
axial flow of fluid like an airplane propeller.
Kitchen mixers were also researched. Most electrical kitchen mixers
manufactured by companies such as KitchenAid, CuisineArt, and Bosch came with three
different blades: a whisk, a dough hook, and a heart shaped hollow blade. Whisks are
designed for non-viscous fluids such as eggs. However, Shea paste is too thick and
viii
viscous to mix with a whisk. The dough hook was considered but it did not fit the
appropriate application. Shea Butter mixing must accomplish a range of viscosity that
starts as a thick paste and ends as a fluid. The final fluid is similar to the consistency of a
milk shake. The heart shaped hollow blade, which was made for medium viscosity
ranges like pancake dough, seemed applicable to the project. This blade looked like an
outline of a leaf made out of bent extruded bar stock.
With further research, the ideas from different types of mixers were put together
and modified to the project. As a result, five proof of concept blades were fabricated:
helical, solid symmetrical, solid asymmetrical, angled, and the hollow asymmetrical
blade.
All proof of concept blades were made out of welded steel because it proved
quick to assemble and made a durable product. All blades have a solid 16mm diameter
shaft that fits into the mounting apparatus in the same manner.
Helical Blade
This blade proof of concept was created to simulate an auger. The helical blade
(Figure 2-A) has 15 individual whisk blades, each 117mm long and 6.4mm diameter.
They were then welded onto the main shaft in a helical formation with approximately an
inch of separation.
Figure 2-A: Helical Blade
ix
Solid Symmetrical and Asymmetrical Blades
These blade proof of concepts were created to simulate the solid paddle design of
a butter churn. The solid symmetrical blade (Figure 2-B) and asymmetrical blade (Figure
2-C) both have four individual 123mm x 76mm x 2.75 thick steel sheet metal blades
which are welded axially onto the main shaft.
Figure 2-B:
Symmetrical Blade
Figure 2-C:
Asymmetrical Blade
Angled Blade
This blade proof of concept was created to model the industrial mixer propeller
design. The angled blade (Figure 2-D) used three individual blades that measured
102mm x 76mm x 2.75mm thick steel sheet metal first welded onto rebar 101mm in
length by 13.6mm diameter. They were then welded onto the main shaft.
Figure 2-D: Angled Blade
x
Hollow Blade
This blade proof of concept was created to model blade designs of kitchen mixers.
The hollow blade (Figure 2-E) was fabricated with welded sections of rebar resulting in a
U-shape design 123mm on length and 115mm in height. Four of these U-shaped rebar
were then welded asymmetrically onto the main shaft.
Figure 2-E: Hollow Blade
Testing Procedures
Shea paste is necessary for testing the mixing process of our machine. This Nut is
only found in West Africa and is very difficult to get overseas. In order to begin proof of
concept testing, a substitute product was required.
Through research it was determined that peanut butter would be the best substitute
for Shea paste. The process of making peanut butter is very similar to making Shea
Butter. The main difference is that when making peanut butter the process stops at the
grinding stages. The goal is to keep the oils in peanut butter, not extract them. One of
the project contacts who had worked with Shea Butter also said that the viscosity of
peanut butter felt the most like that of Shea paste. The problem with peanut butter is that
it is very expensive.
xi
In order to keep the cost down, it was decided to use a mixture of flour and water
for the proof of concept testing. The testing looked for differences in the mixing based
on blade design. While it was understood that viscosity would play a factor in the final
product, the group chose to simply examine the differences in mixing with the current
procedure in order to get a better understanding of mixing processes in general.
The testing of the blades was first done by creating a mixture of flour and water.
The mixture used was a ratio of 4.52 kg of flour with 7.25 L of water. The flour and
water was then mixed by kneading until a uniform consistency was achieved. This
mixture had a similar consistency to that of pancake batter. A consistency resembling
that of peanut butter (viscosity of 1290 kg/m3) was originally desired to simulate the Shea
paste. Density figures were unavailable for Shea paste. Because flour has an ability to
compact, an accurate density was difficult to obtain. The final mixture ratio of flour and
water was determined by inspection.
xii
Appendix C: Scale Reduction Testing
During the months of January and February, scaled down versions of blade
designs were created and tested using actual shea paste. It was decided that the scale
should be reduced because of the limited supply of shea paste in our possession. In order
to eliminate a number of variables, an electric mixer set at 60 rpm was used as a power
source. The container containing the shea paste was set in a water bath so that the
temperature could be raised to the proper level and be consistent for each test. A
hexagonal container was constructed and tested along with a circular container. The
hexagonal container was manufactured to determine if the container shape was vital to oil
extraction as stated by a contact in Ghana4. Both circular and hexagonal containers were
used to determine if the shape was a key factor for oil extraction. A space heater was
also set up near the mixer to increase the ambient air temperature around the test.
Testing Procedure
Required Equipment
1. Container ( circular or hexagonal)
2. 250g of Shea Paste
3. Water bath basin
4. 2 stands
5. General Signal Lightnin mixer
6. Poly Science water heater
7. blade shaft
8. 800 ml beaker
xiii
9. 1 tablespoon measuring spoon
10. Thermometer or thermal couple
11. Space heater
Procedure
1. Place Poly Science water heater into water bath filled with water.
2. Set water heater to heat to 35° C.
3. Place Shea paste into container, and place container into water bath.
4. Attach blade shaft to mixer and place shaft into container so that the end of
the shaft is centered and not touching the bottom of the container, then fasten
mixer to stand.
5. Place space heater about 2 feet away from water bath set-up and turn on to
800 watts setting and a medium temperature.
6. Allow paste to heat to 27° C
7. Set mixer to mix at 60 rpm
8. Add 4 tablespoons of water to paste, and begin mixing; record paste
temperature, air temp, and wattage being used by the mixer.
9. Add 1 tablespoon of water to paste every minute for 3 minutes.
10. At t = 10 minutes, add 2 tablespoons of water, record data.
11. At t = 15 minutes, add 1 tablespoon of water, record data.
12. At t = 20 minutes, add 2 tablespoons of water, record data.
13. Monitor paste and add 1 to 2 tablespoons of water as needed. Record data
every 5 minutes.
xiv
14. Remove oil from top as needed and place into separate container.
From this testing, we were able to see that oil separation was able to occur in
circular containers, and that the asymmetric angled bladed extracted this oil in the
shortest amount of time.
Figure 1: Experiment setup
Figure 2: Circular container showing oil extraction
xv
Figure 3: Hexagonal container used
xvi
Appendix D: Power Source Concept Analysis
Treadle
The idea of a treadle came from the examination of how certain older sewing
machines and spinning wheels operate. A vertical motion of a foot pedal rotates a
flywheel that in turns rotates a shaft. This rotation would have to be transferred through
the use of bevel gears. The most appealing aspect of this power system is the flywheel.
This rotating mass creates a larger moment of inertia. This would allow the shaft to
rotate longer with less effort because more energy is stored. Since this requires a large
mass to act as a flywheel that could become expensive and cumbersome, this idea was
eliminated.
Electric and Combustion Engine
The electric motor and combustion engine are obviously the power sources that
require the least amount of effort to be applied by the user. However, these options were
eliminated from consideration early in the design phase. One design requirement is that
the final product cost less than $100 US. These motors are often expensive, and would
end up consuming a very large portion of the construction budget.
There are also environmental concerns associated with both of these options.
Combustion engines require the use of petroleum products that are much too costly for
the average village woman. Gasoline is priced roughly around four dollars a gallon,
which is twice the daily income of the average village woman. This also requires that
women continue to incur costs even after the machine has been built. Electric motors
require a source of electricity. Most electricity in Mali comes from diesel generators,
which as has been stated, can be expensive to operate over time. Automotive batteries
xvii
are prevalent, however there is no method for recycling them, and their disposal often
leads to the contamination of ground water.
A concept hand crank was made using steel tubing, wood, copper bushings and a
length of galvanized pipe. A handle made of flat steel plate and a round steel bar was
connected to the galvanized pipe. The galvanized pipe was bored out to allow it to fit
over the blade shaft. A hole was drilled into the pipe as well as each shaft and the shaft
and pipe were attached using a pin. This allowed for the rotation of the handle to be
transmitted to the blade shaft. This concept hand crank can be seen in Figure 1.
Figure 1: Hand Crank Design
Once a uniform consistency was achieved, a measurement of the required force to
turn each blade design was found through the use of spring force scales. Multiplying this
figure by the distance of the center of the handle to the center of the blade shaft gave the
amount of torque required to turn the shaft. Each blade was tested in the flour mixture
for a total time of 15 minutes. During the first minute of mixing, a bottle of food coloring
was added to the mixture. Observations regarding the mixture’s color, texture, and
consistency were made after every minute of mixing. When the color and texture had
become uniform, the mixture was considered to be evenly mixed. Force measurements
were also made at several points throughout mixing to confirm that the amount of torque
xviii
required to turn the blade was consistent. Five blade designs were tested using this
method.
Test Results
Based off of test procedures and methods used, calculations were made to
determine the best results of the power source alternatives. Four power sources were
considered and compared based on given design requirements. The hand crank was the
only power source constructed due to time constraints and current manufacturability.
The power source alternatives were evaluated using the design requirements given
by the client. In addition, engineering requirements were added to evaluate overall
performance. Each one was weighted according to its contribution as a power source.
Torque required was our main focus, weighted at 22.5%, followed by cost, reliability,
manufacturability and maintenance required.
Each power source was scored based on its performance in each of design
requirement fields. A score of five was the best option available for the given category.
The data was compiled and the power source design rankings were compared. Three
designs stood out as plausible options. The hand crank, hand bicycle, and treadle
receiving 3.47, 3.395, and 3.36 respectively were top choices. The treadle design was
ruled out due to inconsistent information from several primary sources as to availability
of materials. The two other designs will be pursued in future prototypes.
The primary concern when choosing a power source is the transmission required
to rotate a shaft for the blades. A 90-degree rotational shift from one plane to another
could prove prohibitively expensive. A beveled gear could make the transformation but
xix
would also add to the cost of the design. Further investigation for a twisted v-belt to
B
ic
yc
Tr
le
ea
dl
e
B
at
te
ry
/C
om
bu
st
an
d
H
an
d
H
W
ei
gh
tP
er
ce
nt
C
ra
nk
io
n
make a similar transformation is being explored. This can be seen in Figure 2.
Manufacturing Ability
13.5
4
3
3
Cost
16.5
4
4
3
Torque Required
22.5
2
3
4
Maintenance Required
13.5
4
3
3
Safety
Reliability
Functionality
9.5
4
4
3
13.5
5
4
4
11
100
2
25
3
24
3
23
Total:
Weighted Total:
Description
Scale
Measure by time and tools
5 Easy -> 1 Difficult
5 necessary to manufacture
Material Cost and Labor
involved
1
5 Cheap -> 1 Costly
Measure the time it takes to
5 Easy (less torque) -> 1 Hard
mix efficiently
more torque)
5
5 Little to none maintenance- > 1
High Maintenance
2 How easy is it to clean parts?
How dangerous are the parts
5 good -> 1 no good (moving
parts)
1 involved?
2 Life expectancy of unit?
5 Usefulness/fatigue
21
5 Very Reliable -> 1 Replace
5 Practical -> 1 Impractical
3.47 3.395 3.36 3.15
Figure 2: Power Source Results
xx
Appendix E: Procedure/Assembly
MATERIALS
Wood/Lumber
*Length of wood is important but other dimensions are approximate
5cm x 30cm
8cm x 8cm
1 – 5cm x 30cm x 100cm (length)
1 - 5cm x 30cm x 200cm (length)
4 – 8cm x 8cm x 30cm (length)
1 - 8cm x 8cm x 60cm (length)
2 - 8cm x 8cm x 100cm (length)
Nuts/Washers/Screws/Threaded Rod
xxi
Threaded rod
*The Diameter of Rod Determines Wing-Nut size, washer size, holes to drill
4 - 0.635cm diameter threaded rod 50cm (length)
1 – 0.635cm diameter threaded rod 30cm (length)
Wing Nuts
*Must thread on threaded rod
14 – Wing nuts
Washers
*Needs to slide over the threaded rod
14 – Washers outside Diameter 3cm
xxii
Screws
*Must be long enough secure pieces of wood together
20 – Screws 7cm (length)
Metal
*Diameter of Shaft DETERMINES bushings and pulleys to purchase!
Stainless steel
1 – Sheet approximately 35cm x 30cm square approximately 0.15cm thick
1 – Shaft approximately 1.5cm Diameter x 70cm (length)
Steel
1 – Shaft approximately 1cm Diameter x 50cm (length)
2 – Anchoring plates 8cm (length) by 12cm width and approximately .15cm thick
xxiii
Pulleys/Belt/Bushings
Pulleys
*Must be able to find belt to fit pulleys. Also, shafts from above section must fit through
hole in pulley and must be able to lock to shafts
1 – Pulley approximately 10cm in Diameter with 1cm shaft able to slide through it
1 – Pulley approximately 5cm in Diameter (half the size of other pulley) with 1.5cm
shaft able to slide through it
Belt
*Must fit on pulleys
1 – Rubber Belt (Black in color) approximately 72cm (length)
xxiv
Bushings or Bearing
*Shaft Diameter is important to match. Outside Diameter is not crucial but will need Drill
Bit to match size
2 – Bushings with Shaft Diameter of 1.5cm
2 – Bushing with Shaft Diameter of 1cm
TOOLS
1 – Dill
1 – Screw driver
1 – Hammer
1 – Welder
Various Drill bit Sizes
xxv
STEPS
*Container purchased will minimally affect design. Slight modifications will need to be
made with container obtained.
Blades
3 blades will need to be cut from the stainless steel sheet metal.
1) Measure container to determine radius at the bottom, middle, and top of container.
These will determine how long your blades will be.
2) First blade will be 2cm shorter than radius at bottom of container by 8cm wide. (It
will be 2cm shorter due to width of shaft attaching it to and human error)
3) Second blade will be again 2cm shorter than middle radius of the container by
8cm wide.
4) Third blade will be 2cm shorter than top radius of container by 8cm wide.
xxvi
Next weld blades on shaft.
1) Take the shaft approximately 1.5cm Diameter x 70cm (length) and mark 6cm
from one end, 12cm from same end, and 18cm from same end.
2) Weld first blade to shaft at 6cm mark on shaft on a 45degree angle.
3) Weld second blade to shaft at 12cm mark in opposite direction on 45degree angle.
4) Weld third blade to shaft at 18cm same direction as first at 45degree angle
Handle
1) Take shaft approximately 1cm Diameter x 50cm (length) and make marks at
15cm and 35cm. Bend shaft at 15cm mark 90degrees then 90degrees opposite
direction at 35cm so it looks like:
xxvii
Post Handle
1) Take 8cm x 8cm x 100cm (length) and measure 25cm from one end and 4cm in
from side to find center of hole to drill
2) Drill a hole at mark using drill bit that is the same size as the outside diameter of
the Bushing with Shaft Diameter of 1cm
3) Press the 2 Bushing with Shaft Diameter of 1cm into the wood.
4) Slide handle through
xxviii
Top Table
1) Take the 5cm x 30cm x 100cm (length) draw a line down center of the board
2) Measure 4cm from each side of line and draw a line whole length of the board.
Again measure from the centerline 4cm PLUS the diameter of the threaded rod to
both sides of center line.
3) Find center of board and measure out the top radius of the container from the
center. Measure 2cm in from this distance and 8cm out from this distance,
creating an approximately 1cm x 10cm(length) slot. These will be your slots to
make it adjustable to containers needs.
xxix
Container Post
1) Take the 8cm x 8cm x 100(length) and place it on top of your container. Cut it to
size but allowing 15cm over hang on one end and about 20cm on other. Find
center of container on 8cm x 8cm post and mark it.
2) Drill a hole at mark using drill bit that is the same size as the outside diameter of
the Bushing with Shaft Diameter of 1.5cm
3) Press the 2 Bushing with Shaft Diameter of 1.5cm into the wood.
4) Slide blade shaft through bushings.
5) Cut out a section of the post 2cm deep by 25cm long from the end that over hangs
the bucket by 20cm.
6) Next drill a hole 30cm deep (or as deep as you can) and the same diameter as the
threaded rod in the end of 8cm x 8cm post on the end that over hangs on the
bucket 20cm. This act as a belt tensioner later.
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Anchoring Plate
1) Cut/grind slots 0.635cm wide (size of threaded rod) in anchoring plates as
follows.
Assembly
1) Take the 5cm x 30cm x 100cm (length) board and attach with screws the four
8cm x 8cm x 30cm (length) posts to the corners.
2) Attach with screws the 5cm x 30cm x 200cm (length) board to step one as such.
3) Attach Handle post off center in front of top table with screws
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4) Attach the other 8cm x 8cm x 100cm (length) with screws and cut to appropriate
length and cut ends on angle accordingly.
5) Place container on top table centering it.
6) Take the 0.635cm diameter threaded rod 30cm (length) and put it in the hole of
the container post drilled earlier. Slide washer over end and tighten with wing nut.
(Note the tensioner will push against Handle Post. A steel plate made be needed
so threaded rod does not push too far into handle post wood.) Slide blade shaft
through bushings in post and put on top of container. Slide pulley approximately
5cm in Diameter on blade shaft and lock in place. (See CAD drawing).
7) Slide the four-threaded rods through slots on top table and around container post.
Slide anchoring plates across top of container post and through threaded rod to
secure container in place. Use washers as seen in drawing. Secure with wing nuts
to set in place. (See CAD drawing).
8) Slide pulley approximately 10cm in Diameter on 1cm handle shaft and attach belt.
(See CAD drawing)
9) Use “tensioner” to tighten belt and tighten down wing nuts on top container post
Slide plastic pipe over handle for added comfort. (See CAD drawing).
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Appendix F: CAD Drawings
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