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This project involves designing a lightweight, adjustable, custom walker, similar to a gait trainer, for a 2-year old girl with Cerebral Palsy. The walker must be easy for her to move around.
The problem our team will be solving for this project will be designing and building a small walker to help a 2-year old girl with Cerebral Palsy walk around. She has tried other walkers before, but the main problems that she runs into when using these walkers is 1. She is unable to move the walker around, and 2. She uses her arms to hold herself up on the walker so that she is not using her legs to move around. Because of these problems, our team is tasked to design a small walker that is lightweight and easy for her to move around in, and has better arm support so that she does not feel inclined to try and hold herself up as much when moving around. Also, the walker needs to be able to allow her to easily hold herself upright without requiring her to grip onto things because she has a hard time gripping onto things.
Because of her condition, there are many specific design specifications and safety considerations that must be applied to this project to insure a safe and easily usable experience.
Design Specifications:
Cerebral Palsy is a congenital disorder due to abnormal brain development before birth. The main symptoms of this disorder include exaggerated reflexes, floppy or rigid limbs, and involuntary motions. Because of these symptoms, young children with Cerebral Palsy often have a hard time walking without a walker, and traditional walkers usually do not provide enough support or features for them to take advantage of. Here are a couple of walker designs meant specifically for children with Cerebral Palsy that our team has taken some inspiration from. The main features from these walkers that we want to implement in our walker are the harness system that helps to secure the child to the walker, and the adjustable height that can be seen in the second picture with the hand screw.
This design is a multi-functional device designed to be a walker and standing device. The child is not strong enough to walk or support her full weight, and this is designed to help incrementally load her full weight onto her legs. The seat of the chair can be angled to allow her to rest some of her weight on the chair while allowing her legs to support her as well. the frame would be made out of aluminum allowing for it to be very lightweight and mobile. The tray, seat of the chair, and armrests would all be able to be removed and replaced with ease allowing for plenty of room for the child to grow and the walker to adapt.
This concept is based on the design of a traditional walker but implements some specific design elements to support and grow with her properly. This includes adjustable legs and locking wheels to change as she grows and allow it to be stationary if needed. It also includes a removable tray, seat, arm braces, and back brace. These provide her with an area to use if needed, a seat to rest or to support her, the arm braces ensure that she does not have to grip the walker, due to weaker grip strength and the back brace keeps her from falling and allows partial support if needed while walking. This will also be made of aluminum and other lightweight materials to ensure she can move the implement.
This design primarily takes structural integrity and safety into mind. The two circular rings used to connect the four legs provide ample structural support for the walker and the child in the seat, and they also prevent the child from possibly falling over. The legs are also spread out in order to minimize the risk of the walker falling over while the child moves the walker around.
Based on our decision matrix, our selected concept design to move forward with is Concept 2.
Note: Our final design ended up being something completely separate from any of these designs, after further discussion in our team.
Our selected design was chosen based on four main factors: weight, safety, adjustability, and cost. Here is how we believe our design meets or exceeds our requirements for each category:
Looking at the vertical supports, we found a stress ratio greater than ten leading us to use a long column analysis for buckling and critical load, the critical load for the material and geometry is vastly larger than and force that might be exerted by the weight.
For the walker to be adjusted , we use screws put into the vertical supports slots that will be subjected to stress, for our selected material of screw, shear strength 1590lb, no load subjected by the child will cause them to fail.
Looking at forces exerted on the extreme ends of the top of the walker, we calculated possible moment that could cause walker to fall forward or backward (rotate about the child), to be sure that the child could not fall by irregularly pushing around her bodyweight. We concluded that no reasonable force exerted by her will cause this to happen.
Fabrication Process:
In testing, the seat of the walker was able to hold 165 Lbs without a problem at all, and I would guess that it would be able to take much more weight as well. The walker rolled smoothly and the caster wheels worked well for turning. Overall, the walker works very well.
This project helped us learn a lot about the engineering design and fabrication process. We feel very grateful and lucky to be a part of this project, and we hope that we were able to create a safe and useful walker for Josie for many years to come.
