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Mobile Stander


Tatum is a little girl who is just over two years old. She suffers from seizures and has muscular dystrophy. She can barely stand on her own, and she cannot walk at all.

Since she will be entering the school system soon, she will need something to help her navigate the building, as well as challenger her to develop her leg muscles so that she may be able to walk as she grows older. The mother would also like to have a desk as part of this system so that Tatum has an area to play on and do school work.

Nicholas Wallace, Brandon Stubbs, Brandon Hines, Tyler Coulter, Bryan Dimino, Nickaleus Ridner

Problem Statement

Our client has a combination of muscular dystrophy and cerebral palsy, she is currently two and a half years old and is needing an adaptive mobility chair/gait trainer to navigate at school and at home. She has significant medical constraints, such as an inability to stand up on her own, walk, and even occasionally opening her hands from a clinched position. Currently, the family has Tatum using a stander in order to encourage muscle development in the hopes that she can walk in the future. She is also attending PT regularly. The mom would love to have something similar to their previous stander, but bigger in size and adaptability. Our goal is to create a device to fulfill Tatum’s needs as she continues to grow and serve as a gait trainer towards her mobility in the future.

Design Specifications

Our final design must be transportable to and from school, allow Tatum’s legs to move freely in a walking motion, and be adjustable to accommodate her changes in height and weight as she gets older.

Below is what Tatum has been using, but she has since outgrown this and is need of something more versatile.

Background Research

The market is flooded with several different training devices for children that have disabilities such as cerebral palsy, muscular dystrophy, and spina bifida. These devices range in price from $500- 5000+ depending on the functionality, weight/material, accessories, and practical lifespan of the device. It is important to note that the vast majority of these devices are built to be replaced when the child moves to their next growth spurt; this is impractical and expensive in the long run. A standing gait trainer is favored over a wheelchair for the following reasons: promotes lower extremity use, allows eye-level interactions, improved bowel and bladder function, and allows muscle and bone development. Several variations of these standing devices exist such as a cane, two-wheeled walker for operators that have some coordination, four-wheeled walker for operators with little to no coordination, or a gait trainer. So with all this in mind, we will design a hybrid that will allow a few years of practical use, allow Tatum to move more freely, provide assisted movement from the wheels, add accessories to promote upper body activities, and include a harness that will support all her weight while sitting and can provide support while walking.

Concept Design 1

Description: For this design, we analyzed how Tatum’s current stander is structured. The idea is to give her a new stander that will allow her more room to grow. It is adjustable in height and will accommodate her maximum weight. Essentially we would form fit the seat on her current stander on to a new frame.

Concept Design 2

This design incorporates a desk for Tatum to be able to play with toys, draw, and exhibit the use of her arms. The concept is similar to design 1 where it would act as a gait trainer. We would form fit her seat to this frame so she has the ability to move freely. The desk is adjustable so it can change according to her needs as she gets older. This design has the advantage of a desk which is easily adjustable, as well as collapsible for storage or traveling.

Concept Design 3

Our final design attempts to bring to life something the mother mentioned, which is joining a walker with a high chair. While the computer model is somewhat hard to visualize, this design features adjustable height and an adjustable support pad to accommodate her growth. The frame will also include 4 free-spinning wheels to allow three degrees of freedom. The design will also feature a suspended seat inspired by the pictures shown in the background research. There is also room for future discussion of a removable table that will attach to the front of the device to allow an activity area while the product is in use.

Selected Concept Design

We are leaning toward design concept one because it is closest to the gait trainer she currently has. we were informed that the best thing for her would be a larger version of what she currently has, and we feel that design one is the best design to pursue.

Overview of Selected Design

We ended up going with design 1. There is a lot of polishing that has to be done with the design to make it look good for the family. It will be the same concept as design 1 but will include a tubular frame and incorporate the seat from the current gait trainer.

Engineering Analysis 1

Assuming a maximum load on the gait trainer of 100 lbs which is evenly distributed between the left and right side of the frame, we found that the maximum stress on the lower weld has a magnitude of roughly 20 MPa. After referencing “Fatigue Design Curves For 6061-T6 Aluminum” by G.T. Yahr from the Engineering Technology Division of the Oak Ridge National Laboratory, we found that welded aluminum under repeated loading with a stress amplitude of 20 MPa will be able to sustain a minimum of 200,000 loading cycles.

This finding translates to 137 loading cycles every day for the next four years, which should be more than enough for this application.

Engineering Analysis 2

Round and rectangular aluminum tubing will be machined to construct the gait trainer. This analysis is done using an independent beam (with wheel supports) and a central loading on the beam to find the stress on the aluminum with a load. The aluminum can withstand stresses up to 35,000Psi before deformation. In the analysis the largest psi calculated was 8150 psi.

Engineering Analysis 3

This is our tipping analysis for the mobile stander. This analysis is based on the maximum allowed wheel chair ramp being a 1.5″ rise per 12″ run which gives us a 7.16 degree incline. The analysis is also contingent on the person’s center of gravity being in the middle of the gait trainer and total weight of 100 lbs. With the given data, our calculations indicated that the force required to tip it over would be at a minimum of 42 lbs.

CAD Drawings

Bill of Materials

Document Fabrication Process

Testing Results

We have delivered the gait trainer to our family already. The height adjust up and down with pin holes through the side of the adjustable steel bars, as well as the seat adjust up and down via straps and gives it even more height adaptability. Testing wise we asserted a unnecessary amount of force downward onto the trainer to ensure the welds and supports will hold. Overall this trainer exceeds the necessary amount weight that it can support.

Completed Design Photos

Instructions for Safe Use

This product does not have many instructions for safe use, due to the fact that the child can only be in the trainer when put in by an adult. As the only instruction for the adult to ensure is that the child is safely secured into the seat. When your child has outgrown the particular designated height then, while the child is not seated, remove both pins from each side and adjust to the desired height. Lastly, ensure that the child is able to reach the ground for mobility.

Project Summary/Reflection

This project, for many of us, has been our first hands on experience with designing and manufacturing our own product. As we had the chance to meet a family and do our best to improve their lives by building their daughter a gait trainer. This gave us the opportunity to learn various different tools in the machine shop and also powder coating for the finishing color. Working in a team of six can be difficult when trying to schedule times to discuss/work on the project. Despite having different individual schedules, as a team we were able to complete the project on time and with a quality product. Giving this to the little girl in the end has made all of the hard work worth it and just to be able to help there entire family gave us a tremendous amount of satisfaction.


2019 Fall