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1. Load cargo 2. Sell 3. Buy necessities 4. Go home
User Experience Engineering
Designing a Wheelchair Attachment to Transport
Merchandise and Cargo in Less Resourced Settings
ManufacturingLoad performance Terrain adaptability CustomizabilityUsability
Life Quality
Social Life & Dignity
User Interaction Map (UIM)
Final Design; Highlighting Key Decisions
Merchandise / Cargo
Project Origin
Project Introdction
Conclusions and Future Plans
To find more:
Many, many thanks to Cara, Ken, Memuna, and Isabella.
And pay my highest tribute to Freddy, designer of the first generation SafariSeat.
The Accessibility Institute (TAI)
The SafariSeat Wheelchair Project
Co-creation In Covid Situation
SafariSeat Workshop
Figure 1. The SafariSeat.
Figure 3. Location of the bakery.
Figure 4. The disabled lady.
Figure 5. Anthropometric data
of adult man’s hand and body.
Figure 6. The testing platform.
Figure 7. The 3 possibilities.
Figure 9. Initial concept.
Figure 10. Usability & DfMA refine.
Figure 11. Finite element analysis.
Figure 12. Final design with all details.
Figure 15. SafariCart with user interact with the supporting leg.
Figure 14. Top view with
caster scanning areas.
Figure 13. SafariCart with user interact with the supporting leg.
Figure 17. Extreme load test.
Figure 16. Usability test of SafariSeat.
Figure 19. T-bar.
Figure 20. SafariCart in
different terrains.
Figure 22. Modification possibility Figure 23. SafariCart frame.
Figure 21. Self rotation.
Figure 18. Extreme torque test.
Figure 8. Detachable trailer (Back).
Figure 2. The workshop in Kenya.
Food Store
Social media
Fuel Station
Water Station
Retail shop
- GDP per capita -Average Life Expectancy - Disability Rate
Potential Employer
Government officer
Petty loan
Water barrel
Self treatment
Gas tank
Fresh food
INDD341 Individual Design Project
Supervisor: Dr Farnaz Nickpour
Sifan Yan
The Bakery
Division of Industrial Design
School of Engineering
SafariSeat is a low-cost, durable, all-terrain wheelchair
designed and manufactured in Kenya using basic tools
and locally available materials. SafariSeat enables
low-income individuals across Africa to access inde-
pendence, education, employment and a life beyond
the confines of their own home.
The SafariCart project is based on a real charity case and has received support from
the original design team. The client from Sierra Leone hopes to design a detachable
trailer so that users of an all-terrain wheelchair can conduct various trades and mer-
chandise sales. Designers need to design the cart from both user experience and
engineering aspects, and fully consider localized manufacturing and maintenance.
The final design will be tested and mass-produced in Kenya. A successful design will
change the lives of many people.
At this time, the project produced a SafariSeat wheelchair attachment that meets the
client's needs and can theoretically be produced. The design includes a connector, a
customizable underpan, and a bread transport rack on it. The designer reviewed the
key points of the development and design of the project, and designed the product
from both user experience and engineering side.Through finite element analysis,
full-scale testing and other methods, the load-bearing performance and usability of
the design have been theoretically verified, but the project still needs to wait for the
manufacturing and testing of the physical model, and further optimize the production
efficiency and safety before entering Mass production.
This design result has been approved by the funder. In the next few months, the
designer will continue to follow up on the project, optimize the design from the
above-mentioned aspects, and remotely participate in the prototype testing in Kenya.
About half a year later, a batch of SafariSeat & SafariCart sets will be sent to a newly
built bakery in Sierra Leone, and several disabled people will get their first job.
Through this opportunity, they will improve their quality of life, expand their social
...and live with dignity.
This design project was created in collaboration with a
charitable organisation in Sierra Leone who run a
bakery, employing local disabled individuals to make
and sell baked goods. The bakery wanted to find a
way for SafariSeat wheelchair users to distribute and
sell their baked goods across the city streets.
TAI is a non-governmental organisation based in Sweden, who funds the manufacture and distribution of high quality,
affordable and locally manufactured mobility aids across developing regions of the world, such as SafariSeat. TAI
also manages and funds new research and development projects such as this one, which was established through
their partnership with the bakery in Sierra Leone.
Fusion360 was selected
as the main modeling and
finite element analysis
method. It is especially
suitable for the design of
complex assemblies. The
latest CAD model can be
shared online through
links and can be viewed
on multiple platforms.
Formal meetings are con-
ducted on zoom, while most
communication is via email
and WhatsApp.
A Google drive acces-
sible to all members is
created for file sharing.
In different stages, a variety
of methods are used to real-
ize product visualization.
The safariseat workshop is located in Kilifi, Kenya.
This labor-intensive workshop relies on local
materials and supply chains to produce SafariSeat
wheelchairs in batches. Simple cutting, bending,
welding and painting processes are completely
achievable, but there is a lack of heavy machines
to achieve complex processing techniques.
Office series is used for
content recording and
2015 2016 2017 2018 2020
project Kickstarter Realworld
set up
Cutting Welding
Liverpool, UK
Gothenburg, Sweden
Wuhan, China
Freetown, Sierra Leone
Kilifi, Kenya
Injection molding
Die forging
Hammering Assembling
Compared with other design projects from scratch, the user group of SafariCart is
very clear from the beginning. They must first be the users of SafariSeat wheelchairs.
Therefore, the designer is not satisfied with pure functionality in the advancement of
the project, but refines user needs in a deeper level. While pushing the product to the
convenient level in the User Experience Hierarchy*, the designer discusses the
impact of the product on the user at social level.
The creation of Persona and scenario is based on a
disabled lady photographed in Sierra Leone. She
owns a hand-cranked tricycle, but cannot find a job
through it and can only beg along the street.
According to PDS, URS, and further literature collection, a user interaction map (UIM) was created to clearly outline the three
levels facilitated by this product, as well as the corresponding stakeholders, services, and people. First of all, users need to
get a job through this product, and interactions within this range should be fully considered. Secondly, users need to improve
their quality of life through this product, and extreme situations such as oversized and heavy loads need to be considered
within this range. Finally, this product will bring users a new social life and enhance their sense of dignity. At this level, new
possibilities need to be paid attention to, such as other potential employers. The practical significance of this project will
depend on whether the various interactive scenarios, load, and interest relationships in this map can be fully considered.
A Product Design Specifi-
cation (PDS) is created.
The basic attributes of the
trailer should be adapted to
the wheelchair and suits
the scenario and UIM.
Based on literature and actual photo
& video from Sierra Leone. A user
requirement statement (URS) is
summarized to clarify the user’s
physical and psychological pleasure
points and pain points.
The anthropometric data consistent with the
original design was applied to the design of
the basic dimensions of the trailer. Such as
the size of handles, doors, partitions etc.
The connector is fixed to the
two beams of the SafariSeat
to achieve minimal changes
to the original design.
Top handles ensures that the
wheelchair can be moved by
the bakery worker when it is
To avoid collision between the wheelchair
casters and the trailer when turning, the
underpan of SafariCart is designed as a 45°
rotated square.
This structure
limits the open
angle to 90°.
The locking mechanism
also serves as a door
Steel door
(2mm thick)
The Aluminium chequered
plates can be drawn out to
put in larger-sized items.
The anti-collision casters
consistent with the original
design ensure good terrain
It can also rotate relative to
the wheelchair with the verti-
cal line of T (second stroke)
as the axis.
The workshop manager con-
firmed that all components
can be produced in the
Kenya workshop or obtained
through local supply chain.
The net cost of all parts and
consumables is within 150
The underpan and the connec-
tor are designed to have redun-
dant load capacity.
For potential employers and
other scenarios, the upper
structure of the trailer can be
modified or redesigned.
It can take the horizontal line
of T (the first stroke) as the
axis, and pitching to adapt
different terrains.
The theoretical maximum load capacity of
the final design far exceeds the 30-50kg in
the PDS, which provides sufficient possibili-
ties for other scenarios.
The user can independently complete
all the interactive actions included in
the scenario. Support leg, door lock
and other key positions have been
simulated in full scale, and the physi-
cal model will be field tested in Kenya
in 2-3 months to collect more usability
The T-bar design at the con-
nection provides sufficient
terrain adaptability.
Bicycle reflectors improve
safety in urban environments.
Sliced Loaf:
Miniloaf Pack:
Supporting leg
Pin guide
(4mm thick)
(4mm thick)
After going through the 4 stages discirbed
above, the key design decisions have been
highlighted below and explained in detail.
(figure 13 - 15)
All components and features have gone
through at least four iterations. It is impracti-
cal to show all the iterations in this poster, so
the connector is selected as an example of
concept development.
First, after sketch deduction, a simple con-
ceptual model is constructed. It shows the
basic functions and fixing methods of the
components. (Figure 9)
After communicating with the CTO and the
workshop manager, the design was modified
at the level of usability and manufacturing
feasibility (DfMA).(Figure 10)
When most of the design features were final-
ized, several rounds of finite element analy-
sis were performed on the model to test and
improve its structural strength. (Figure 11)
Finally, after further cooperation with the
CTO and the workshop manager, a produc-
ible component with good user experience
and high structural strength was presented.
(Figure 12)
Since the design of the trailer also involves
turning, bending, holding backhand, and other
complex movements that are not included in
the basic anthropometrics context, actual
testing becomes necessary. The designer
built a full-scale test platform at home using a
cheap wheelchair with the same height, width
of the seat, and similar handle features in the
back, air purifiers at the height of the trailer
connection, and a tennis trainer. Because it
simulates the use of SafariSeat quite well, this
platform played a key role in subsequent test
iterations, helping designer determine the
positions and dimensions of many key parts.
The SafariSeat uses a unique rotating suspension system to adapt the wheelchair to
the rugged terrain in rural areas. But the excellent original performance also brought
great challenges for subsequent modification. The engineering difficulty of this project
is mainly on three points: how to achieve a firm connection between the trailer and the
wheelchair, how to maintain the terrain adaptability of the original design, and to
achieve a reasonable connect and disconnect operation.
Persona and scenario
Brainstorming Concept Selection
Concept Development
Anthropometric & Usability Test
Some data about Sierra Leone:
User Requirement Statement
get a job
transport daily necessities
comfortable operation
confidence and dignity
broaden social circle
better social image
Product Design Specification
load: 30-50 kg
service life: 5-7 years
transport & display
Good terrain adaptability
made in Kenya SafariSeat workshop
relatively cheap & easy to maintain
maximum load:
maximum torque
on connector:

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