college of engineering white

Project 2: Adjustable Chair


Our goal is to design an adjustable chair for a young boy so that he has back and head support in his classroom. It needs to be able to ‘grow’ with him, so that he can use it in various classrooms over the next few years.

Caleb Harman, Ian Sweetin, Jacob Cotten, Peyton Pope

Problem Statement

The issue we are looking at is that this boy needs a chair that can adapt to suit his needs. He firstly needs the chair to be able to adjust to various heights, so that as he grows and moves into a bigger classroom, he is able to have the chair adjusted to the correct height for his needs. Second, he needs back and head support, ideally in the form of straps, as suggested by his teacher. Finally, the chair needs to be mobile. It should be able to move around the classroom as needed in order to help get him into the chair, and should be able to lock as desired, so that he doesn’t slide around the room while in the seat.

Design Specifications

  • Needs to be able to support his head and back
  • Boy weighs 26 lbs. and is 31.5 inches tall
  • Chair have wheels, but be able to lock
  • Be able to adjust the height of the chair as he grows (10-16 in seat clearance capability)
  • Back of chair needs a slight tilt backwards for when he eats

Background Research

For the design of the seat itself, we initially looked at modifying a car seat, as it seemingly hit two birds with one stone: the seat and the straps. The seats normally had a slightly backwards tilt, and the straps were built in order for a child to be comfortably secured in the seat. However, the rest of the car seat posed an issue, as it usually doesn’t sit level, and there would be a significant amount of difficulty in cutting away most of the outer frame of the seat, as well as securing it to an adjustable base within the desired seat height specifications, so our current idea is to design a seat to suit our needs, and to upholster it so that it is both safe and comfortable for the child.

As was already somewhat discussed, our original idea for the straps was to simply use the ones from a car seat, which would likely be one of the most comfortable options. However, the boy will need a specific type of strap in order to achieve our support goal, that being shoulder straps. A standard diagonal strap would allow to much freedom of movement while he is secured in the chair, and a waist-only strap would fail to provide the needed support.

The base of the chair is what will not only need to connect the seat and the wheels, but also to function as the primary mechanism in order to adjust the height of the chair. While the chair will not be needed to be adjusted often, we decided it would be best to keep it simplistic, so as to allow anyone that needs to adjust his chair to be able to do so. Our group initially looked at using a hydraulic base, such as one found in an office chair, but found that the height of the mechanism in combination with the other parts would normally be too tall to meet the minimum seat height requirements. It needs to be able to adjust to specific desired heights, roughly every 2 inches or so, leading us to decide on using sliding legs with a pin in each chair leg in order to secure the height of the chair.

The wheels were a fairly uncomplicated issue; the boy needs to be able to take his chair both around his classroom and to another when he needs it, and the easiest solution for mobility on a chair design is to use wheels. For the locking mechanism, however, we decided that using cheap wheels and locks would either lead to a brake failure or would lead to the wheels themselves failing. Therefore, two potential solutions arose: we could either find better wheels that come with a braking system, or we can focus on the wheels and try to add some mechanical braking system after the fact.

Concept Design 1

Our preliminary design utilizes our ideas on the locking wheels, an adjustable base with pins to lock out the legs of the chair, car seat straps, and a seat specifically designed to suit our design specifications.

The wheels and locks will allow for simplistic mobility  of the chair, as well as rigidity when desired. The pin-locking system for the base of the chair gives us both functionality and safety, as they are easy to use and quite sturdy. The straps will allow us to give the child the support he needs while also keeping him comfortable, and the seat will be designed to tilt back slightly and be tall enough for him to sit comfortably.


2023 Fall