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February 13, 2019 0 Comment

1.INTRODUCTION
As a mechanical engineer student , one should be able to use the skills and knowledge obtained from the design process .This is achieved by doing research and developing new ideas .We have been given an opportunity to design a manual wheelchair.

2.SITUATION
In South Africa there are so many people who are unable to walk and this situation may have resulted from injuries or diseases . In this case possible solutions were made in the past to better the lives of those who cannot walk by developing a mechanical machine called a manual wheelchair .However , there is still something missing in a wheelchair .People need a wheelchair with effective brakes , one which allow them to brake in a short period of time to avoid any injuries. The design needs to be able to satisfy the needs of everyone who is in need of it.

The design will be based on the strength of the material and the cost of the product is put into consideration so the product has to be affordable . This will give anyone who is in need of it to have quick access and buy without thinking twice.

3.PROBLEM IDENTIFICATION
Disabled people find it very difficult to use the manual wheelchairs that have been designed because of the brakes . The brakes are essential to be part of the wheelchair .They enable the user to move into and from the wheelchair without falling .The brakes that are needed need to be effective at all times irrespective of the environment .It must accommodate inclined planes ,rough surfaces and also smooth surfaces.

4.RESEARCH
The research project was on the locks of the manual wheelchair .Then a couple of types of locks were put into consideration namely :
1.Pull/push lever.

2.Scissor locks.

3.Wheellock extension.

4.Hub locks.

1.PULL/PUSH LOCK
The most commonly used locks in a manual wheelchair is pull/push lock .It is very simple to use it . It works by pulling the lever backwards or by pushing forward the lever until the bar presses the is on the tyres . And it accommodates everyone who is in need of it because it is simple to use and it is not complicated.

2.SCISSOR LOCK
They are called the scissor locks because they are in a form of a scissor and they are designed for people who have been using wheelchair for a long period of time.It does not favour people who have just started wheelchairs now.

3.WHEEL LOCK EXTENTIONS
This type of a lock needs an additional length to lock the lever by so doing it helps the user to reach the lock without struggling . The user can lock and unlock without having to worry about anything .There is a problem with this type of a lock because the way it operates is very fast and can cause injuries to the user of the wheelchair.

4.THE HUB LOCKS
It locks the wheelchair through the wheel hub instead of the tyre.

-The pull/push lock is my best option for my design it is reasonable and everyone will be able to enjoy using the product.

5.MATERIALS
-The large rear wheels are made of aluminum.

-The lightest chairs have fixed arms that allow the user to move into and from the wheelchair if the user is unable to stand for a long period of time.

-The hand rims are mettalic ,having a circular steel tube and are attached to the driving wheels of the wheelchair to allow control without making the hands dirty.

-The rims are coated,this will help users with problems in gripping on a smooth surface.

-The lever ensures that the wheelchair does not roll down when it is in an inclined plane and the user can move into anfd from the wheelchair without slipping.

-The pneumatic tyres are used to provide shock and are more suitable to rough surfaces.

-Caster wheels have a solid rubber and they are durable.

– The seat are flexible and have rigid cushions.

-The pressure is stable and it provide comfort to the user of the wheelchair.

– The heel loops are constructed of by a cloth.

-The foot plates are made of an aluminum underneath and on top is covered by a solid rubber.They are removable and can be adjusted from the wheelchair and also helps in transferring into and out of the wheelchair.


6.SPECIFICATIONS
After doing some research it was found that many people people prefer a wheelchair that has the following:
1.Weight – the wheelchair must be able to carry a weight of 150 KG .2.Height – is 60 inches.

3.Seat width – 32 inches.

4.Seat length – 40 inches
5.Depth – 28 inches.

6.Safety– the product is 100% accurate it will not collapse on the way of using it, it is garantteed.

7.Cost – the product has a reasonable price this ensures that everyone who is in need of a wheelchair will be able to buy it .Plus the wheelchair has a good quality.

8.The size of the locks – it is 7 inches.

9. Diameter of the large rear wheels – 27 inches.

10.Diameter of the hand rims – 23 inches.

7.STRESS ANALYSIS
Inches cm M
Length 40 101.6 1.016
Width 32 81.28 0.813
Mass =150 kg
The force applied on the wheelchair will be equal to the force of gravity. Therefore :F = mg where m = 150kg and g = 9.8 m/s squared
=(150)(9.8)
=1470 N
Area = length * width
=1.016 * 0.813
=0.83 metres squared
Stress = F/A
= 1470/0.83
= 1780 N/m squared
This is a proof that the wheelchair will be able to carry this weight without collapsing.

These specifications and stress analysis are perfect for the design because they meet all the requirements of the design and the requirements were met .Indeed the design has a good quality ,in good condition,and everyone will be able to buy.

8.POSSIBLE SOLUTIONS
– After considering a quite number of types of locks so for the scissor lock it’s actually a good option to use it as the brakes of the wheelchair . But this option becomes handy to those who are not used to using the wheelchair .- For the wheel extensions it is also a great option to use it as a lock and it will also help those who are short because they have short arms to reach the brakes .The additional length of the brakes will definitely help those kinds of people.

But the wheel extensions have a disadvantage and it is not a good idea for disabled people to use it .These types of locks works very fast and it needs a person who is energetic and it is very rare to find people who are using a wheelchair being in a great condition .

Another thing is that since the process works very fast a lot of users have complained about it because it hurts their hands.

-For the push/pull lock , this one is the most common type of a lock and many people prefer it than other locks .It has no disadvantages and that is the reason why it is preferred by a lot of users of the wheelchair .For the reasons mentioned above about pull/pusk locks it is the one that was choosen as the best lock of the wheelchair.

9.CONCLUSION
The final wheelchair design consists of the pull/push locks
10.REFERENCE
1.Clifford E.Brubaker(1989),Wheelchair IV , Report of a conference on the state-of-the-art of powered wheelchair Mobility,December 7-9,1988,KESNA press.MTILENI EVA BASANI
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