Design of an Urban Wheelchair

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DESIGN OF AN URBAN WHEELCHAIR

Thesis Work, Product Design KPP106, 15 credits, C-level

Master Thesis Programme Innovation and Product Design

Pablo Escudero

Report code: IDPOPEX C:07:132 Commissioned by: Own project Tutor (university): Jan Frohm Examiner: Rolf Lövgren,

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DESIGN OF AN URBAN WHEELCHAIR- Master thesis work

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In this report I will develop a wheelchair adapted to the urban reality of our society. It’ll have to compete with the electric wheelchairs on the market today. There is a real necessity on this as the wheelchairs on the streets today have developed little since they were firstly introduced in world war 2.

To achieve a successful product we will study the different wheelchairs and how they adapt to the urban environment. Such study will include several surveys focusing on the user, it’s illnesses and anthropometrical measures as well as his way of usage. Then we will focus on the wheelchair, the types, characteristics, parts, and functions. The result will be an electric wheelchair which improves significatively in

ergonomics, stability and maneuverability over their electric counterparts. Moreover it greatly increases it’s outdoor and indoor capability reducing the architectonical

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I’d like to thank the “Universidad de Zaragoza” and the Mälardalens university to give me the opportunity and support to come to Sweden and be able to do my thesis work on the subject I wanted to.

I’d like to thank my grandfather Vicente for bringing the subject to me, my aunt Ana and Juan Ramón as wheelchair users to give me some insight on the product and it’s uses. To my uncle Santiago to help me with some medical advice. My parents as their support has been invaluable and they sent me all the books I’ve needed to work on my studies.

Last but certainly not least, I have to thank Jan Frohm for his patience, guidance and knowledge about 4 wheelers that has avoided me many problems I’d have got myself into.

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1. Introduction 5 2. Aim of project 6 3. Project directives 7 4. Problem statement 8 5. Project limitations 9

6. Theoretical background & solution methods 10

6.1. General description 11

6.2. Market diagram 13

6.3. Illnesses survey 16

6.4. Users of the different wheelchairs 17

6.5. Figure analysis of wheelchairs 18

6.6. Functional analysis 20 6.7. Use analysis 21 6.8. Ergonomics 21 6.9. Technical data 22 6.10. Environment requirements 22 6.11. Body transfers 23

7. Applied solution procedures 24

7.1. Concept 1 26

7.2. Concept 2 29

7.3. Concept 3 32

7.4. Concept selection 35

7.5. Development of the selected concept 37

8. Results 48

9. Analysis 59

10. Conclusions & recommendations 60

11. References 61

12. Appendix 63

12.I. Foreword 64

12.II. Market 65

12.III. Ilnesses survey 67

12.IV. Users of the different wheelchairs 78

12.V. Figure analysis of wheelchairs 84

12.VI. Functional analysis of wheelchairs 104

12.VII. use analysis of wheelchairs 110

12.VIII. Ergonomics 111

12. IX. Technical data 114

12.X. Environment requirements 121

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During the past decades, new improvements in medicine have increased the life expectancy of the world population. The new medical treatments not only makes life better but also lengthens the period called “third age”. People in their third age tend to get weaker and sicker and they get incapable to perform tasks they were able to do when they were younger. One of their most common disabilities is the atrophia of the lower part of their body. This atrophia reduces their mobility by changing their body posture, by weakening the muscles or by crippling the legs or hips denying their ability to walk altogether. A world map with the live expectancy can be seen on the appendix 12.III at page 66.

To this group we have to add the percentage of the population that is handicapped by some illness and are going to need a wheelchair and the healthy people that are going to get constrained on a wheelchair due to an accident. Therefore we can assume that the need for a wheelchair is far from gone.

The most common wheelchairs found on the streets today are either hand powered or electric powered but they both share the same structure of big wheel on the back and small turning wheel on the front. This layout is very good for sharp turning at low speeds but when it encounters a rough terrain can easily lock the front wheels and dump the seated person. The reason for that is that they are designed to be used in hospitals or in indoors spaces.

There are other kind of wheelchairs that look much like a scooter with four wheels and an office-seat. This wheelchairs, although heavier, they work better outdoors but they are completely unpractical for indoor use. Plus, the effort made to move from one wheelchair to the other and the impossibility to carry both at the same time leaves the user with the dilemma of choosing which wheelchair will suit him best.

Therefore the room both wheelchairs occupy and the economic endeavor of acquiring both wheelchairs reduces the life quality of many of the handicapped people that don’t have the space or money resources needed to get along with both.

Although I’ve never been constrained to a wheelchair myself, in my family I have four relatives on wheelchairs. I have had the opportunity to field test them and get first hand information about the everyday life.

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The aim of this project is the design of a wheelchair capable of street movement as well as indoors movement. It has to be maneuverable enough to move in a room or tight spaces and able to go over the sidewalks. It will also has to be able to lift the person to a standing position. That means that it has to be a hybrid between a regular wheelchair and a outdoors wheelchair.

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To accomplish the aim of the project some research will be needed.

It’s important to understand key aspects of the product in order to learn the strengths and weaknesses of each type of wheelchairs. It’s also important to find whatever mistake has been done and repeated on previous models. Therefore a survey will be carried out analyzing the different wheelchairs characteristics and differences.

If I limit my survey to only the wheelchairs now in sale I’ll have only studied the solutions given to a problem but I wouldn’t study what the problem is. It could be that the wheelchairs face the problem in a more conventional way and the market inertia doesn’t allow them to rethink and give a better solution. That’s the reason why I’ll conduct a survey about the different illnesses and their relation to a wheelchair. I will look for problems that are solved in an incorrect or incomplete manner and also problems not solved yet.

Many people with illnesses suffer different deformations that prevents them from walking. Some can’t seat properly. I’ll have to study the different ergonomics in two different ways: focused on what the people need and how wheelchairs adapt.

The surveys described above will be basic to solve any kind of wheelchair that is going to be designed. As the project is more focused on a indoors-outdoors solution, a study of the environment will be of most importance. As we live in an urban environment on the common basis I think that a basic survey about the urban environment focused on the difficulties a wheelchair user encounters will suffice.

After studying several aspects of the functionality of the product I have to focus on the form of it. I will have to take a survey on the shapes of current

wheelchairs, how and why are like that. It will be interesting so I can decide how the designed wheelchair be understood as a wheelchair but at the same time will stand out from the rest of them.

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The problem to solve in this project is:

Is it possible to develop a wheelchair that works well indoors and outdoors and that can lift the person to a standing position?

The problem can be solved if the following points are answered: • Requirements for a wheelchair to be indoor capable.

• Requirements for a wheelchair to be outdoor capable.

• Transition of a handicapped person from sitting to upright position. • Is it possible to find a point in between?

To find the solution more specific questions will be needed in order to find a simple and organized way of solving the project.

• What kind of wheelchairs there are? – Wheelchair market diagram

• What kind of illnesses that involves a wheelchair there are? – Illnesses survey

• How does the wheelchair and the illnesses relates? – Uses of the different wheelchairs

• What do I need to know in order to successfully design a wheelchair? – Figure analysis

– Functional analysis – Use analysis – Ergonomic studies – Technical data

• Which problems does a wheelchair user encounter in an urban environment?

– Environment requirements – Body Transfers

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1. The time limitation for this project is 10 weeks full time.

2. The project will be to find an innovative solution for handicap people in urban environment. It will be centered on the wheelchair.

3. It will be presented in 3D-CAD model and physical model 4. There is not any kind of material limitations

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To successfully accomplish the goals of the project a methodical approach must be used. In this case I'll use the method suggested by Bruno Munari in book reference 4, where the writer suggests an approach to problem solving divided into the following steps:

1. Problem. Here the need is stated. In this report it can be found in the “aim of the project”.

2. Problem definition. Here a more detailed definition of the problem is taken place. In this case it is stated in the project directives, problem statement and project limitations.

3. Problem elements. The problem is divided into smaller problems that can be easily solved individually in such a way that those answers can be gathered to become the solution.

4. Collect data. All needed data to solve the problem elements is gathered. 5. Analyze data. All data collected is analyzed.

Points number 3 to 5 will be answered later in this section and completed in the appendix. 6. Creativity. All analyzed data is gathered and used to solve the problem elements and present viable solutions in a creative way.

7. Materials and technology. A compilation of materials and technology available to solve the problem is presented.

8. Experiment. The elements in point 7 are studied to find the ones that gives the best answer.

9. Models. Study models are created to check if the solutions presented in the creative process are viable.

10. Verify. The models will be checked to see their validity.

11. Constructive drawings. Technical drawings will be made to build the solution.

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12. Solution

Due to the project limitations steps 7 through 11 will not be implemented in this report but may be subject to be carried out in the future.

Next I will develop as many surveys as needed in order to be able to generate valid and feasible solutions to the aim of this project. The information gathered for this surveys come mainly from two books (marked as reference books number 1 and 2). The first book, “Problems of wheelchair users in Spain”, is a big research survey centered on interviews on the users: their illnesses, limitations and wheelchairs

preferences. This book covers a big part of my research. The second book, “wheelchair user manual”, is a quick guide of tricks and maneuvers a handicap person has to do in order to move around in a wheelchair.

All this information is backed up by a market research through the Internet analyzing most existing models. I interviewed my family too as they have all the different types of wheelchairs in the market and provided useful information on the daily life of the wheelchair user.

First of all I’ll introduce the subject. It will be done by a series of definitions, a market diagram, and a survey about the different illnesses. From there we will analyze the wheelchair to further understand it. There will be a relationship between the different illnesses and the different types of wheelchairs followed by several surveys analyzing every aspect of the product. This section will finish with a study of the urban environment from the point of view of the wheelchair user.

Before starting the survey it will be interesting to go through some definitions. This will give the basic vocabulary needed to properly understand and develop information within this industrial sector.

• (Definition) Wheelchair: A wheelchair is a wheeled mobility device in which the user sits. The device is propelled either manually (by pushing the wheels with the hands) or via various automated systems. Wheelchairs are used by people for whom walking is difficult or impossible due to illness, injury, or disability. ...

en.wikipedia.org/wiki/Wheelchair

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The concepts behind this definition can be seen on the following table where it shows the overview idea of the ICF (International Classification of Functioning, Disability and Health ), created by the World Health Organization.

• (Definition) Disability: A disability is a condition or function judged to be significantly impaired relative to the usual standard of an individual of their group. The term is often used to refer to individual functioning, including physical impairment, sensory

impairment, cognitive impairment, intellectual impairment, mental illness, and various types of chronic disease. This usage is associated with a medical model of disability. The human rights or social model focuses on functioning as an interaction between a person and their environment, highlighting the role of a society in labelling, causing or maintaining disability within that society, including through attitudes or accessibility favoring the majority. Disabilities may come to people during their life or people may be born disabled.

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This is a very important table as it easily shows some areas that the

wheelchair can improve and areas to take into consideration when working with them. In the first column is shown the physical limitations of the wheelchair user that will need to be taken into account to adapt the design to it’s necessities. On the second column there are the activities that the wheelchair user performs. It’s important to design the wheelchair in order to ease the realization of those activities. The third column are the surroundings factors. Those are the indoors and outdoors structures that allows or refrains the wheelchair from moving around. The forth column centers itself on the personal level. Although it’s as important as the other columns in order to help the handicapped person to have an independent life, it’s so personal that the design of the wheelchair will do little to help and therefore is not a field of investigation in the report.

To get a perspective of new possibilities in the design of a wheelchair it’s important to know what is being produced. Handicap people have many products available to help them gain the mobility they lack. As there are many products that improve the mobility for handicapped people, each in different extend and ability, it’s important to find a way to show them all together. With the use of a diagram it’s possible to outline the different type of products and the solutions given to specific problems.

The Market diagram is meant to show, at a quick glance, the market structure of the wheelchair. It’s divided into to parts: A more broad view where the wheelchair is located between the different alternatives and another one focused only on the different types of wheelchairs.

6.2. Market diagram

This table gathers up all the basic aspects of the disability. The columns are divided into two parts: the first part defines the functioning and disability. This part is also divided into two parts differentiating between body functions and activities. The second group of columns deals with the contextual factors. This one is also divided into two parts separating the factors depending if they come from the environment or from the handicapped person.

The files are divided into three main blocks. The first part displays the different parts that are affected. This includes which domain and their component within they affect to. The second block is formed by the constructs files and manages all the functions that are altered by the parts listed on the first group. The third set of files manages the positive and negative outcomes from the functions of the second block.

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Handicap people with walking / standing problems

Solutions Walking stick Prosthesis Walkers Crutch Wheelchair

In this diagram it’s shown all the different products that helps the handicap person to walk and stand. Although the project is centered on the wheelchair, having a broader point of view can help to find innovative and new ways of transport that can either be adapted to a wheelchair or be completely new, making a brand new segment in this market.

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Once centered in the market segment of wheelchairs a more detailed information can be shown. There could be many ways to classify them but I believe the most effective way of doing so is based on the way they are powered. This way we get two very different groups: the ones man-powered and the electric-powered.

Wheelchair Man powered Wheelchair Electric powered Wheelchair ASSISTANT WHEELCHAIR STANDARD WHEELCHAIR SPORT WHEELCHAIR VERTICAL POSITION WHEELCHAIR ELECTRIC SCOOTER WHEELCHAIR ELECTRIC POWERED WHEELCHAIR

More information about the different kind of wheelchairs can be found on the appendix (section 12.II at page 64)

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There are different illnesses that hinders the control over the body and forces the person to use a wheelchair. These illnesses will define the problems and

limitations the wheelchair users have and how much their abilities deviate from a healthy person. The design of the wheelchair will have to take into consideration those facts to properly adapt to it’s target user.

To get that kind of information and for it to be relevant a large scale survey is needed. In this case I used the research done in the book “Problemática de los usuarios de sillas de ruedas en España” (Book reference 1) and the e-book “iiplandeaccinparalaspersonascondiscapacidad200320” (e-book reference 2)

There are a some key information to highlight from this survey. A more detailed information can be found on the appendix 12.III at page 66. The different illnesses can be classified into three different groups depending on how limited the person is: they can be limited, severely limited and totally dependent.

The limited people are able to perform most of daily tasks on their own, they have almost normal control over their body and they show very small deformations. The severely limited group can perform many of daily tasks on their own or with the help of another product, they have some control over their body and present

deformation on some part of their body. The totally dependent class needs someone else to perform the task for them, have little to none control over their body and have mayor deformations.

The target group to focus the design will be the severely limited as the freedom the product is intended to give will make a difference on that group and if it can help the severely limited it will have no problems to help the ones within the limited class. The project will not be intended for the totally dependent as they will require an assistant to go with them anyway.

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Once the different type of wheelchairs and the more relevant illnesses for our project have been stated it will be interesting to see how they both relate in today’s market. This will provide an interesting perspective in two ways:

A – How does the wheelchair adapt to the illnesses’ needs. B – What needs are yet to be satisfied.

The point A will give keys to improve the design while the point B will show untouched market opportunities and more innovative solutions.

As the needs in each group of illnesses is different so are the wheelchair requirements. Useful information can be found by looking at the charts where it shows how a specific wheelchair model adapts to the different illnesses (see appendix 12.IV at page 77). Once all that information has been gathered into a single and more general table where the different types of wheelchairs match the different groups of illnesses, the market picture grows clearer. Most of the wheelchairs on the market today have been designed mainly to satisfy two different groups: the limited and the totally dependent.

The people from the limited group needs a wheelchair with few special requirements therefore they are the easiest group to meet the requirements. Most of the wheelchairs dedicated to them are standard. Being the easiest to build and

manufacture, they are able to reach most of the market with little customizations. The wheelchairs adapt very well to their needs.

On the other hand, the people from the totally dependent group have many specific requirements. Those requirements also differs from one illness to another, they requite specialized wheelchairs to fulfill their demands. This groups has severe problems to do normal chores, not only the ones involving movement. This is the reason why they are usually found in the company of someone else that assists them. In this market group the assistant is another important user that needs to be taken into consideration. The wheelchairs in this sector adapt reasonably well.This is shown as most of the wheelchairs in the market are either electric or assistant wheelchairs. This specialized wheelchairs creates a very focused market where only a small amount of units can be sold. Once the product is been placed onto the market there is little outside competence creating a good benefits margin opportunity.

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With most of the products fitting both groups described above, there is little left for the very limited people. This group has to adapt to a wheelchair designed for the limited group, with lower requirements than they need, or the totally dependent, much more expensive and prepared for someone else’s need.

In conclusion, there is a real market opportunity targeting the very limited handicap group. There is a liable technical background to rely on although it will have to be analyzed to find all the aspects that prevents them from getting a perfect fit for the users.

Having studied the user and their needs, the wheelchair market and how both relates has given a good introduction point on the project subject. The next step is to learn about the product itself. Getting to know the wheelchair from different

perspectives will provide a good detailed picture of the product and cues that will help the success of a design.

Here it will be analyzed the wheelchair from the figurative point of view: How it looks like, which parts is it made of and what does that shape transmits.

The figure analysis provides useful information on what can be perceive from the wheelchair through pure observation. It’s not centered exclusively on

aesthetics but also on how it communicates its functionality and how that is perceived by the user. In order to do that, each wheelchair is seen through three different

perspectives: the Syntactic (How does the object looks), the Pragmatic (what it does) and the Semantic (how it tells it’s actions).

After going carefully through all aspects of the wheelchair on the analysis (found on the appendix 12.V at page 83) it is important to note the following information.

From this analysis point of view, standard and lightweight wheelchairs are impossible do differentiate. Both share the shape of a wheelchair recognizable by everyone. The assistant wheelchair differs from the previous two on the back wheel, being smaller on the assistant as there is no need for the person sitting to propel it.

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All elements of the wheelchair are shaped use oriented. There are no

concessions to aesthetics apart than the paint on the metal tubes. As the structure and moving parts are all shown and the wheelchair does perform simple actions, is easy to understand how it operates. All regulations on the wheelchair are made through holes on the support structure and then some screws to hold both pieces at the required length. This simple method is useful when constant changes are needed and the regulation method has to be done often. As most user only need to regulate the wheelchair the first time the use it, it could be interesting to change this rather unaesthetic solution for another one.

The seat is an important part of the wheelchair as the user has to remain on it for long periods of time. As there is some compromise between comfortability and easiness to fold the solutions given are solved on that focus. The seat can be greatly improved by getting a better shape that will allow the user to rest more comfortable while is still able to fold easily.

The footrests, as important as they are they need to be redesigned in such a way that can be stored within the wheelchair easily in case of not use and avoid leaving any protuberances in case of removal.

The aesthetics on the front wheels are very important as they define the “character” of the wheelchair (fast and nimble or slow and cumbersome). On the other hand the focus on the back wheels is centered around the outer ring that may come slippery if wet. The aesthetics on the armrests is important too as it’s designed only with the functionality in mind. It can get some more comfort if it could be adjustable.

Focusing now on the electric wheelchairs we find two different types: the electric-powered wheelchair and the electric scooter wheelchair. The first one is identical to the regular wheelchair with some differences due to the change of propulsion system but the conclusions for this type are the same as the standard. Therefore the following conclusions will be about the electric scooter wheelchair.

As the chair loses it’s need to fold down, the seat can be made rigid with more foam to increase comfort and it can also gain adjustment in some variables. This is highly regarded among the users and helps them avoid atrophy.

The seat in this kind of wheelchairs has to be comfortable over any other function. As the chair gets more rigid the armrest has to be able to fold away. It will also have to hold the controls.

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As the footrest can stay on the chair, they will have to look more integrated to the main body. This structure will have to protect the electric system and

connections as well as to give the user the ability to open it and perform maintenance on it.

The rims from the wheels along with the plastic cover of the structure will give the most of the aesthetic value to the wheelchair. The electric powered wheels and the turning ones can be placed either front or back. The turning wheels on the back will be harder to learn how to displace and on the front will have to avoid hitting the footrest. The turning wheels can turn car-like or freely with carter forks. The first make a more controlled turn than the second but with a longer radius.

On the functional analysis the uses of each part of the wheelchair is studied. This will allow to know which job is expected of each part and which ones are crucial for any purpose given. With that information some problems can be found like: unnecessary or redundant pieces, functions done by two different parts and therefore likely to be able to merge into one single piece… Moreover, combined with the figure analysis, it is possible to identify if the usability message that a part of the wheelchair transmits has any relation with the function it performs. The detailed functions can be found on the appendix 12.VI at page 103.

There is little more to be said from the standard wheelchairs as the figure analysis gave the same conclusions as all parts are shown and therefore rapidly understandable.

As the electric wheelchair share the same way of configuration as the standard one, most of the pieces share the same functions, with some exceptions: the wheels loses the outer ring and gains an engine, the seat and armrests gain more functions as they loose the capacity to fold and gain in adjustability. Probably the one that has a bigger overall change is the structure as it has to support the weight, give integrity to the product and hold and protect all the electric essentials.

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Ergonomics can be defined as “the science of obtaining a correct match between the human body, work-related tasks, and work tools.”

(www.uchospitals.edu/online-library/content=P01158 ) So we can say that, in this case, ergonomics are a series of parameters that dictates the correct distance between the different parts of the human body and the wheelchair.

The ergonomics study is important not so much for the concept generation process but for the proper design of the wheelchair when sizes will be taken into account. Those sizes, lengths and angles are summarized on a table in the appendix 12.VIII at page 110.

6.8. Ergonomics

The use analysis displays the life cycle of the wheelchair with it’s

interactions with all the users. This will help to focus in other areas of usage of the wheelchair, not only on the one related to the user that sits on it. Any improvements in any other area (production, transportation, maintenance,…) will become an advantage over the competition. To see the life cycle of the survey it can be located on the appendix 12.VII at page 109

Looking at the production of the wheelchair, the standard ones are very easy to manufacture, even with low technology equipment. The complex shapes they make and the amount of pieces bent, welded and screwed makes it a slow to manufacture. It could be interesting to study new geometries that speeds up the production system.

During the transportation from the factory to the selling point the most important factor is the ability to stock the biggest number of wheelchairs on the transportations system (usually a truck). As the standard wheelchairs can fold down and has a reduced weight it eases the work to fold an pile. The electric wheelchairs on the other hand is heavier and bigger and can’t fold down, making it more difficult to load and transport.

Use and maintenance on a Standard wheelchair is very simple and a user can find how to do it very quickly and easily. The electric wheelchair on the other hand has more problems than the standard as it has a bigger weight and size, forces the user to work on the garage or outside the house. As all elements are closer to te ground the person doing the maintenance has to lower himself to move the loads (changing batteries or light bulbs for example), getting harder if it’s done by a handicapped person.

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With this section concludes the study on the wheelchair. Therefore it has to cover all the relevant information needed to study and understand a wheelchair that does not fit all the previous analysis. This is then a compilation of facts and numbers. Those wheelchair measures are the ones that are meant to fit with the ergonomic requirements. They are all listed on the appendix 12.IX at page 113.

6.9. Technical data

Once the user and the wheelchair are analyzed it is time to focus our studies on the environment. As the project is named urban wheelchair it is comprehensible that a study of the surroundings and the mobility problems they create is crucial in order to succeed on the design.

It is interesting to look at the table extracted from the book “Problemática de los usuarios de sillas de ruedas en España” (Book reference 1) found on the page 100, where there is a graph showing where each kind of wheelchair is being used most, It can be used only indoors, only outdoors or used in both indoors and outdoors. The results are that at least a 60% of the wheelchair users uses their wheelchair in both cases reaching the 80% on the electric wheelchairs. This is for some reasons: the people that need electric wheelchairs are very likely to be unable to move in any other type of wheelchair due to their illness. The price of the wheelchair is such that a medium income handicap user will only be able to afford one. As the electric

wheelchair bar comprises all types of electric powered wheelchairs it’s interesting to see there are some wheelchairs only used outdoors and those must be the scooter electric wheelchairs. The number of electric wheelchairs only used indoors are marginal.

6.10. Environment requirements

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Moving around with the wheelchair is an important factor to study, but it is not the only one related to mobility. It is also important to be able to move to and from the wheelchair as the handicap person will have to use the toilet, shower, bed… All those actions must be taken also into consideration to make a good user friendly model.

There are several ways of approaching the transfer, most of them require to be at the same level or at a higher level to ease the process. This works both ways as it’s easy to go from a wheelchair to a chair from a higher point, it’s also difficult if the transition from chair to wheelchair is from a lower position. This means that if the wheelchair is able to change it’s height will help on body transfers.

There are also different directions to approach the transfer. Sometimes it’s better to be side by side or looking towards it. There are pictures that displays the process that is being used today with standard wheelchairs on the appendix 12.XI at page 122.

6.11. Body transfers

This section will be separated into two parts differentiating indoors and outdoors as each present different kinds of problems. The wheelchair user finds many problems when moving around an urban environment, either outdoors or indoors. When indoors the wheelchair user have small area to maneuver either by human traffic or because of excess of furniture.

Whenever outdoors, the terrain gets more complicated. Starting by the surface the surface can be flat and hard as on a sidewalk but may have some small debris that can make the front wheels lock and cause an accident. The ground can also be soft as wet earth on a park or garden making possible for the bike to get stuck. It can also find slopes on the transversal direction he’s heading or uneven terrain making the wheelchair tilt and fall to the ground. Another major problem to encounter while going on the outdoors in an urban environment is when trying to change sidewalks or getting into a building which has a small step in the entrance. Most wheelchairs are not able to solve that obstacle or do it fast.

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In chapter 7 we will develop 3 different alternatives that will try to solve the problem to move a handicap person indoors, outdoors and to be able to lift them to an upright position. Each one of the alternatives will have their own unique strengths and weaknesses. At the end of the chapter we will chose the one that fit’s best with the requirements given, the information discovered on chapter 6 and the one more creative.

First semester was a trial, no creative thoughts were coming through, I was stuck thinking on four wheels and a chair on top of it. I was designing a rather complex multi-functional go-kart than a proper vehicle for handicap vehicle. At the very beginning of the second semester, my computer crashed down, losing all my project information and forcing me to start from scratch. This new start helped me to view the info with new eyes and get a new perspective. The following concepts are based exclusively on my second semester work.

For this second semester I forced myself to work from a different angle, trying to get the imagination flow going. The name of the project, urban wheelchair, is very strict as it has the name wheel and the name chair that tied me down on the first semester. To

maximize creativity I decided to go general again, thinking why a chair, why wheels, what’s the purpose of it all. In easy words: what function does those parts play on the wheelchair? The answer is easy, to hold and move the user around. With that in mind I tried to explore different ways of holding and moving people around, trying to get them as close to

“walking” as possible without creating an exoskeleton robot-like thing.

Lock to avoid falling forward or backwards

Hold to prevent falling

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Some doubts were flowing while thinking, in this case, the stress on muscles for this locking feet system (innovative as it’s not being used by wheelchair today). I consulted my uncle Santiago who is a thraumatologist surgeon specialized on the knees and he assured me the only problem is the need to move as to avoid “Decubitus ulcers“ (more info at http://www.emedicine.com/med/topic2709.htm)

Along with the drawings there will be some important ideas that needs to be taken into consideration and are highlighted with a yellow star .In some parts they are summarized and listed so I typed them down and used the following sign

.

To ensure easiness in moving indoors and outdoors I thought that great axle distance will improve stability outdoors but small axle distance will increase

maneuverability, making it fitter for indoors. So it would be neat to be able to shift from long axle distance to short and vice versa. Notice how I tried to remove the chair on top of a rigid structure idea.

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26 7.1. Concept 1: Body geometry change

This concept is an electric wheelchair where the axle distance varies. More over, this distance varies with the chair position, lowering the center of gravity as the axle distance grows when going faster to avoid to turn over the wheelchair. It also raised the feet from the ground, making it able to encounter taller obstacles. In a similar way the wheelchair collapses and the person gets raised to a more standing position that allows them to walk around and talk to people from an eye level position instead that from a low sitting position.

To get that, the footrest will have a knee holder that guides the legs and avoids getting them injured. So I studied the movements the chair and the foot rest had to do with each other (section 12.VI) in order to see the viability of the idea as well as to find out if there is a way of doing both movements on a simplified way.

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Some important ideas to take into consideration at this stage (related to the work in section 12.VIII) :

the moving bar that repositions the chair has to be as long as the height difference Front wheel has to be forward than front feet at position 3 (upright position) Footrest has a different movement ratio

Footrest has to be adjustable in both lengths: Hips to knee

Knee to feet.

In order to be able to move the chair up and down it will also move forwards and backwards to change the body position to ensure optimal interaction with the

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It’s interesting the footrest movement design changes it’s geometry depending on the weight you place on the knee pads, making it engine free and ergonomical with any size and weight of the user.

Raising the seat increases the weight of the legs on the footrests, making them rotate around the knee rest.

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29 7.2. Concept 2: Upside / down

This concept is an electric or manual wheelchair where the axle distance varies. This concept is more “classic” as it has a seat and a rigid structure for it’s wheels. But that’s where similarities end. In here I tried to defy the reason why all the pieces of the wheelchair were placed in such a fashion and if there is any posibility to put them elsewhere improving usage and building costs.

One of the main thing you notice on a wheelchair (section 12.V and 12.VII) is that footrests and front wheels, even when they are so close together they use separate

structures with their own folded and welded set of tubes. It could all be part of the same piece.

The way to change the axle distance will be by changing the front wheel distance up to a point it could be used for easy storage. This concept had studied the motorbike-like aesthetics, the position transition and the way the front wheels turn around

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One of the key aspects of this wheelchair is that the front suspension system is the one that acts as the lock that changes the axle distance.

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32 7.3. Concept 3: wheelchair pull

This concept is different from the previous ones as it sees the problem from another perspective. This concept is an add-on to a standard wheelchair that powers it an moves it around. It had some issues on it that needed some serious attention as it had to work on a platform already existing with it’s limitations. It’s also cheaper than a whole new

wheelchair, making a new type of market opportunity (section 12.II). The information about caster forks have been obtained from “groundwork: casters” (e-book reference 4)

You can’t pass footrests as they are placed now because they leave no room. You could if you add the footrests to the new system.

If the structure is to low and long it won’t go over bumps. It has to be small enough to fit UNDER the wheelchair.

If that is so then is NO MORE URBAN CAPABLE than a standard wheelchair.

The bigger the CARTER wheel the less stable it is.

The carter wheel can be placed on the FRONT or on the BACK. If there is NO carter wheel then a wheel will have to be able to TURN.

It can be big enough to fit INSIDE the wheelchair (or on top). If that is so then it will have to turn for the wheelchair.

It should be able to REDUCE it’s size for storage. Place’s to lock on a wheelchair:

Back wheelchair axle. Front wheelchair arm.

Front wheelchair tire / wheel. Anti-tip bars.

Folding cross bars. Arm rests

Foot rests structure (substitute)

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Concept – lateral view with basic structure distribution. To fit the wheelchair ON TOP

Concept on 3D with the connections and armrest control.

Place to hold onto the anti-tip bars.

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35 7.4. Concept selection

Although the three concepts explained above suit the requirements of the project, each one will fulfill it to a different extent. Therefore the concept that adapts best will be chosen for further development. To find out we will point their concept strengths and weaknesses and their overall rate of project fulfillment. The results will be presented in a table. Each wheelchair will be tested in a series of aspects. Those aspects will be valued on a scale from 0 to 5 being 0 the lowest value and 5 the highest. The rating will be given by me according to how the aspect is fulfilled by an existing rival wheelchair. In addition to that, each aspect will be added a weight importance as some aspects will be more crucial than the others. The concept with the highest overall value will be elected.

The characteristics valued in the concepts are: outdoor capability, indoor capability, adaptability, raise / lower user, wheel turning, foot rests, electric / hand powered, wheelchair storage. The outdoor capability measures how well it can perform on the outdoors and able to overcome the problems presented on section 6.10. The indoor capability

measures how well it can perform on the outdoors and able to overcome the problems

presented on section 6.10. Adaptability refers in how well the indoor and outdoor capabilities are complemented. The raise / lower user aspect will determine how efficiently can it raise and lower the user. Wheel turning refers to the turning capacity of the wheelchair, how sharp and precise it’s turning is. Electric / hand powered can only have two different values: 2 points if it can be powered either electrically or manually and 5 points if it can do both. Foot rests considers the holding capacity of the legs and feet, an important factor when raising the user. The last aspect to consider is the storage space it needs when not in use. As the project goal is to get a wheelchair that performs well indoors, outdoors and is also able to lift the person sited, the result on those aspects will be the valued higher.

As some aspects are more important to others, they are related to a weight value. The sum to all the values equals 100. This makes it easier to relate each aspect to a percentage value. As the target wheelchair has to be able to perform indoors and outdoors, the capacity to do so is vital. It’s not sufficient for the concept to perform well on just one. That is why the value of this two aspects is worth 60% of the concept, being 30% each as they are equally important. The adaptability and the capacity of raising or lowering a user are also important as they are related to the main goal of the project. Therefore they deserve to have the same value and having only 40% left to distribute they get a 10% each. With only 20% left to distribute into 4 aspects and thinking that a value under 5% is rating it below it’s true importance, I decided to give the same 5% value to the remaining aspects. Some of this last aspects may seem to deserve more than the value given, like the one that rates the powering method. Indeed the election of making a hand or electric powered wheelchair is very important in terms of manufacturing and the price tag given but what measures is the possibility for an electric wheelchair to be powered manually.

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Once all concepts have been evaluated, it’s time to look at the results and make a selections. Concept 1 and 2 are very similar in terms of their outdoor capability and how it adapts to their indoors maneuverability but the first concept does it slightly better. The first concept also is better for indoors the other two. None of the concepts manage to give a good solution at the possibility to raise or lower the user, but concept 1 manages to give a decent one. The concept 3 is a small electric plug in to an existing wheelchair, this leaves to the existing wheelchair do most of the aspects valued, getting a low score for that. On the other hand is the easiest to store due to it’s small size. The next concept easier to store is the concept 2 as it’s capable of folding down. The concept one is too big to be able to get stored easily. The concept 1 is the one that turns best compared to the other two. Although a wheelchair with concept 3 attached will be also able to turn just as good, it doesn’t enhance this ability that’s why he gets such a low score. The concept 2 needs a big turning radius more similar of a bike than a wheelchair, lowering the score. Concept 1 and 2 has an innovative footrest system. Being the first one more innovative than the second, it gets a higher value.

Overall the concept 3 gets a low score as it’s not capable of significantly enhancing the capacity of a regular wheelchair. Both concept 1 and 2 are valid choices but the concept 1 has an edge as its solutions are more refined. Concept 1 has the highest score but what makes it the best choice is that it is the one that performs best indoors and outdoors and gives a feasible solution for raising the user. Therefore I select

CONCEPT 1

for further development to make it the solution for this project.

5 3 0 5 wheelchair storage 1,40 2,25 3,40 100 Overall 2 5 2 5

electric / hand powered

0 3 5 5 foot rests 1 2 5 5 wheel turning 0 1 3 10

raise / lower user

1 3 4 10 adaptability 2 1 3 30 indoor capability 1 3 4 30 outdoor capability Conc ept 3: wheelchair pull Conc ept 2: Up side / d o wn Conc ept 1 : B ody geometry chan ge Im port an ce val u e %

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37 7.5. Development of the selected concept:

At this point we got into more detail. The first and foremost characteristic for this concept to work out is to find out the movement of the chair and see if it’s viable. If we can’t find a feasible solution for this we should go for the next concept discarding this one. We made a more defined drawing of the seat and the footrest. We also cut our own version of a scaled figure in order to articulate it and check if the drawings were satisfactory.

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Once we got tested out that the product was able to perform as expected we continued with the design of the footrest and the knee pad. I also studied different ways the swing arm could push the kneepad to make them position themselves with the same

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Once we got tested out that the product was able to perform as expected we continued with the design of the footrest and the knee pad. We also studied different ways the swing arm could push the kneepad to make them position themselves with the same mechanical movement

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With the chair and footrest solved it was time to place it on our “chassis” and see how we should place the swing arm in order to get the best ergonomic position for the user to perform and where the footrest wouldn’t interfere with the wheels layout.

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After this study we decided to go against the swing arm, the signature of the concept, for several reasons:

•It had to be over designed to withstand so much weight. •Very expensive to build the racks and pinions necessary for it. •No easy maintenance.

•Could be dangerous if someone places their hand on the wrong place.

•Difficulty to make a strong position, good swing that will allow to get the chair on the desired place without interfering with the wheels.

So we got back to the starting point again for the chassis (keeping all the work done for the chair and the footrest) and came up with two different ideas:

A

3 wheeler

were the chair, front half and rear half of the chassis are connected through a pneumatic pump. That means that every time the piston goes up the axle distance contracts and every time it goes down it expands. The back wheels had carter forks and long trail.

A 4 wheeled wheelchair with all 4 wheels able to turn. It reduces it’s axle distance by FOLDING the center of the body with an electric engine rotating along it axle.

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Being both options equally viable we decided to go for the one with the folding center as it can work with only an engine and makes a more compact and safe system and it gives a better aesthetics.

Working on the concept we decided to lock the footrest to the chair but instead of doing it at knee height as in the standard wheelchair it’s bolted at feet height. It’s also able to rotate around the foot freely, depending on the pressure given on the knee rest.

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After having the basic idea laid out we centered ourselves on reaching the indoors outdoors capability so we studied the differences between having a big or small axle distance as well as the different ways of steering.

Can roll over at a bump Can get stuck at a bump

YOU CAN GET BOTH ON THE SAME WHEELCHAIR Good for outdoors

Good for indoors Good for turning Good for stability

SMALL AXLE DISTANCE BIG AXLE DISTANCE

Big wheels makes shaky steering Precise steering

Cannot be powered No shaking

360º turn on a dime Big cornering radius

Small wheel for high speeds can’t get over bumps Good at high speeds

CARTER STEERING CAR STEERING

Options:

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Front car steering

Back carter steering

Not so stable if carter wheels are close together

Not so good at turning if the carter wheels are separated

About CARTER wheels: • axle MUST be vertical •Lighter wheels

•Big trail •Big wheels

•Pneumatic wheels require maintenance Less turn

I decided to have front car steering and back carter steering, I started to draw a more defined product. I soon realized how fragile it looked. Being an object were the user has to use it because of his handicap it has to inspire confidence on him. Therefore I shifted the movement to a mounting type where the engine, instead of folding both ends of the structure, turns a lever around. The lever has one end attached to the front end allowing it to rest on the strong lever and giving a more strong position than the folding type.

Center mounting type Center folding type

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Looks of the front part.

Front side looked from a back view

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Once all the factors and ideas from the concept development are weighted and added to the wheelchair, the project is defined. The main structure is divided into two well differentiated parts to allow the variation of wheel axle distance to help it

perform indoors and outdoors. The front wheels are electric powered and are also capable of turning just like a normal car. The back wheels have carter steering and are free to turn.

The seat is supported by an pneumatic pump capable of withstanding great weight and to move upwards and downwards. The knees rest on a kneepad that is used to regulate the tilt angle of the footrest. All this aspects can be easily see on the following image.

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As the result on the survey (section 6.5) demonstrated the main visual message is concentrated on the structure and on the wheels. As the message wanted for this wheelchair was speed and strength the message is sent in different ways:

• The wheels have big rims to give the sensation of a sports car alluding the speed a sport car can get.

• The front part of the structure is shaped resembling the contour of a male strong torso meaning the strength it has within. When the

wheelchair folds to reduce it’s size the same message is transmitted as the front body is always on top.

The rear body is shaped in such a way that if it collides with an object it will tend to go over it instead of getting stuck. It also gives a good stable structure to work on and it’s rectangular base helps improve the battery storage capacity.

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The main characteristic of this wheelchair is the ability to lower and raise the chair and the ability to modify it’s length to fit through narrow spaces. The following two pictures shows how the swing arm moves the front body of the wheelchair onto the rear body making a shorter base. It also displays the positions the chair and footrests take for optimized outdoor travel and maximum height at low speeds respectively .

Both bodies are united by a swing arm electrically powered. This arm will force the front body go over the rear body. This swing arm is very sturdy and can withstand a lot of pressure. The engine is a small version of the ones used on the electric beds.

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The wheels are the second part of the wheelchair with important visual content. In this wheelchair the front wheels have the looks of a sport cars to give sense of speed. The back wheels have the same style but in a smaller size to reinforce the message sent by the front wheels. The reason why the front wheels are the biggest is also to make easier for the wheelchair to overcome any pothole or curb.

The front wheels are the ones electrically powered so they are not able to move freely. They are able to turn just like a regular car would do to make it easier for the user to learn how the wheelchair turns and also to reduce the turning circle.

The back wheels instead they have a carter fork allowing them to turn 360º. This further increases the turning capacity of the wheelchair. This carter fork has a longer trail than normal to make it more stable when turning. It also has a locking system that gradually reduces it’s ability to turn as the speed increases making the wheelchair more stable and predictable at higher speeds.

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The footrest is integrated into the front body of the structure. They are able to lean back and forth. The way it regulates itself is through the weight given by the user as it rests the weight of the legs on the knee rest creating an angular momentum compensated by the force of a spring.

The way it works is as follows. The footrest system is locked at O allowing only the rotation. There is a spring at O making an angular momentum Ms, that increases as the angle A grows smaller. The leg of the user makes a downward force at W due to the weight. This weight creates an angular momentum Mw at O. Mw depends of W and of the distance between W and O called d. The weight varies depending on the reclination of the seat but for a given position of the seat we can assume that W will be constant.

At any given d there will be a specific A, and therefore a specific Ms. At that same position of d there will be

W

d

O

Ms

Mw

a specific Mw. If Mw is greater than Ms then the kneepad will recline making A smaller, increasing Ms until it reaches Mw’s value. Reaching a stable situation. This case is caused when the person lowers the seat increasing the weight of the legs on the kneepad.

On the other hand if the user wants to raise itself and get more vertical on it’s seating position then the weight W will be reduced, getting Ms bigger than Mw and pushing it until it balances out.

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The footrest are a cavity where the user can rest it’s feet. It’s shape helps keep the heel in it’s place making it hard to move it away involuntarily. The shape reminds the pedals of a car, further increasing the visual message given by the structure.

As the wheelchair is designed to be able to overcome some obstacles, the chair has to be adapted to prevent the user from falling out of it. It’s shape reminds of a cross between an office wheelchair and a car racing seat combining the adaptability of the first with the safety of the second. It has back slightly curved to hold the shoulders of the user a little bit. The seat has high sides to help prevent the user from sliding out of the seat.

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The seat itself is mounted on a three spoked metal base. Each radius is separated 120º from it’s counterparts with one of them pointing at the back of the seat. The center is moved to match with the center of gravity of the user. The pneumatic piston head locks onto the chair at the center of this metal base.

The seat has some regulations that are posible. The back can be lowered or raised depending on the height of the user through the button placed on the back (I). The seat can turn around itself (II) to ease the movement in and out of the wheelchair. This movement is only allowed when the armrest structure is lowered (III), making the task easier. When the armrest bar is lowered (III) the armrest folds itself in such a way that always stays horizontal (IV). The system of locking the armrest is similar to the ones found on bus transports. Movements II, III and IV are meant to help the user transfer itself from to the wheelchair (section 6.XI).

I

IV

III

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A physical model was made to represent and ease the comprehension of the product during the presentation.

The physical model was a 1/3 scale from aa 3D model with real measures. A more technical view can be seen on the following pages were it will be possible to see .the wheelchair in three different views with some general measurements and a

percentile table extracted from the technical data section were it compares actual datum with the measurements of this wheelchair.

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57 Electric wheelchairs percentile table.

S1: Full height S2: Full length

S3: Full width S4: Seat width

S5: Height from the front tip of the seat to the floor S6: Seat angle

S7: Seat depth S8: Armrest maximum height

S8*: Armrest width S9: Back angle

S10: Back height S11: Back width

S12: Footrest minimum height S13: assistant’s handle height

S14: Back wheel diameter S15 Front wheel diameter

S16: Distance between both axes

S17: Horizontal Length between the seat’s back and the controller S18: Height between control and the seat

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35.5 56.6 60.0 25.0 34.0 100.0 22.0 45.5 106.0 110 10.0 79.5 47.0 17.5 60.0 46.0 64.0 118.5 124.0 p-95 101.6 - 60 47.0 44.0 Distance between both axes (cm)

S16

45.0 43.0

31.0 Horizontal Length between the back and the

controller (cm) S17

75.0 73.0

68.0 Armrest maximum height (cm)

S8

30.0 27.0

16.0 Height between control and the seat (cm)

S18

31.0 19.0

10.5 Front wheel diameter (cm)

S15

15.0 32.0

21.5 Back wheel diameter (cm)

S14

X 93.0

83.1 assistant’s handle height (cm)

S13

16.4 14.0

8.5 Footrest minimum height (cm)

S12 45.0 39.0 31.0 Back width (cm) S11 112 89.0 72.0 Back height (cm) S10 100 103 94 Back angle (º) S9 10.0 8.0 5.3 Armrest width (cm) S8* 38.5 42.0 38.0 Seat depth (cm) S7 15 6.2 -0.7 Seat angle (º) S6 52 54.0 48.0 Height from the front tip of the seat to the floor (cm)

S5 46.0 41.5 37.0 Seat width (cm) S4 80.0 58.5 53.1 Full width (cm) S3 152.3 – 100.5 106.0 77.0 Full length (cm) S2 112.9 95.0 90.5 Full height (cm) S1 Urban wheelchair p-50 p-5

Notice how the measurements from the front and back wheel diameter are changed as this table considered the back wheel to be the one to be electrically powered. Normal wheelchairs have a range of wheel sizes depending on the user characteristics. The wheelchair designed has a front and back wheel big enough to go over curbs and give stability when at high speeds. It wouldn’t perform better with a smaller wheel and a bigger wheel will only make the wheelchair more expensive.

The seat is just one measure, it could be produced in different sizes to meet all the spectrum of users (as the rest of the companies does).

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Once we finished the development of the concept we now look back to see how well the final product fits into the project requirements. As the aim, the directives, the problem statement and the project limitations are defined, a plan of action is laid and solved through the theorical background and the solution methods.

• The different kinds of wheelchairs on the market are seen on the wheelchair market diagram.

• The kind of illnesses that involves a wheelchair are studied in the illnesses survey.

• The relationship between the users with their illnesses and the different kind of wheelchairs can be seen on the chapter: uses of the different wheelchairs.

• To be able to successfully design a wheelchair I conducted a series of analysis and surveys:

– Figure analysis, to understand it’s looks and the visual message – Functional analysis, to learn how it works

– Use analysis, to comprehend how it’s used – Ergonomic studies, to analyze how it fits the user

– Technical data, to gather useful data for the design process • To understand more the problems that the urban environment presents

to the wheelchair user I analyzed the environment requirements. • To further the study of the use of the wheelchair within the

environment I studied the body transfers as an specific and yet important part of the problem.

The results allowed me to design a wheelchair that adapts best to my problem, to be able to effectively move indoors and outdoors. All the strong points on the desired design have had that goal in mind:

• The Change in axle distance to improve indoors and outdoors movement.

• The height changes to make the wheelchair more stable at higher speeds and to raise the seat to allow the user a better access to the indoor environment.

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• Placing the big drive wheels in front to place the better wheel to face the irregularities of the terrain.

• With carter wheels on the back the turning radius is decreased and performs better indoors.

To be a good wheelchair it also has to perform well in other aspects highly valued by the users as it’s comfort and aesthetics.

• The aesthetics are new in the market, giving it a fresh air but at the same time keeping the positive graphic language from the other electric models to reassure the buyer/user.

• The comfort point of view has been thought through as the wheelchair tilts into comfortable positions and the footrest varies it’s position to adapt to the weight issued, allowing a perfect fit to any user.

Design of an Urban Wheelchair