Fall 2025 Project 01: Adaptive High Chair

Caleb Knight, Skye Hamblen, Caleb Salyer, Gavin Giffey, John Goins

This chair was a wonderful and very intense project! The team had fun and was very excited to hear the final product. Throughout the project, multiple different things needed to be researched. For making the seat, that was learning how to properly glue wood together for a strong bond. For the metal and tray, that was learning how to cut and drill it properly. Many adaptations had to be made for our original design. There was a lot of learning how tolerances could affect how parts fit together. How machines could or couldn’t cut or modify certain parts. All of this was researched to make a strong and stellar looking final product. Our team enjoyed working on our first big design project and hope that the family can make great use of the chair!

Problem Statement

The chair needs to assist the child for at least three to five years during her development as a growing child. The chair must be a safe and inviting for the child, as well as practical for the family. It must be easy to use, clean, and move. Making it portable so the family could take it to public places like restaurants was also requested. All these things are important, as it will help the family use the chair while the child still needs it.

Design Specifications

While the chair needs its practical components, there are also some stimulus things we must focus on retaining for the child, as we are building an environment to help her feel comfortable while she eats. One of the simpler, yet equally important requests was a cupholder. We must focus on designing a seat and backing that are both sturdy and ergonomic for maximum support during use. For portability, we are still assessing ways we could make the chair fold into a smaller shape. With our time, we are looking for a practical working solution. Our current ideal goal is to make sure that the chair operates smoothly, but the structural integrity of the chair is our first priority.

Background Research

For our research, we referenced the current highchair the family was using to see what the child may desire in a chair. This gave us a rough idea of what the child would enjoy in her highchair. We also referenced other folding chairs, to see how we could design a mechanism to help the chair fold for portability. Images in order: 1. The current chair the family is using. 2. Some current market designs look similar to this. 3. Folding chair we looked at for mechanism inspiration. 4. Foam seat inspiration.

Concept Designs

Design One

For our first Concept Design, we brainstormed on the idea of the chair having adjustable height, arm width, and adjustable tray position. This would allow for the chair to be adjusted to any height, as well as give the seat any size that would be needed. The height latching mechanism for chair designs 1 and 2 are the same. (click image to see full image)

Design Two

Concept Design 2 builds off of Concept Design 1. The sides are eliminated in favor of only having the chair backing. This simplifies our design in favor of making the seat more comfortable to sit in. The tray is attached to one arm and has a leg divider that can be removed as needed. The tray could be slid towards or away from the chair backing, as well as left or right on the bar it sits on. Since adjustable height was not needed, we opted to remove it in favor of a portable design. A sliding mechanism was designed so the chair could be folded into a compact form, ideal for sitting in the back of a car. The gif animation provided is how we imagine the sliding mechanism would function. (click images to see full images and gif animation)

Design Three

Concept Design 3 takes our second concept design and simplifies the design a lot more. Getting rid of weight and making it easier to adjust. The chair has a simpler mechanism to support it, simply being two legs that are free to move as needed. The tray will have a selection of slide positions to choose from. The frame holding the seat and latching mechanism will be made of aluminum, while the frame of the highchair will be made of a strong wood like poplar. The wood will be sanded and stained accordingly.

Selected Design & Decision Matrix

Our selected design will be concept design number 3. This design is the most simple and reliable. This will ensure longevity for the family as the child grows. It is also the most compact design we have discussed thus far. None of the designs were particularly more difficult to clean than the others. This removed it as a component we needed to worry about for our final design. This design will also be the most cost effective for the support it can provide. With our limited time frame, this design is the best choice. Not only can we make it functional, but smooth and user friendly. This is a huge priority for the family, and the cushioned seat and specially designed tray should help make the child feel at home.

Design Overview

No Overview provided

Design Details

The chair will be made of a strong wood (like poplar or oak). This will provide something that is not only strong, but lightweight for transportation. The seat frame will be made from aluminum, allowing us to make it small and able to withstand the weight it may face reliably. There will be plastic/rubber feet at the bottom of the chair. These will probably be 3D printed with a plastic like TPU. These will prevent the chair legs from scuffing whatever floor it may be on, as well as adding extra grip so the chair doesn’t slide. The legs will be made to stand in a triangle formation, giving us a strong truss-like support to hold the weight of the user. The aluminum was chosen to withstand any stresses that the user will put on the seat. This also will allow for a smooth slide when mounting the seat in the highchair frame. A weather resistant fabric was chosen to make the seat comfortable and easy to clean. The wood will also be sanded and stained, to ensure that it is nice to the touch and stain resistant. All of this should allow for the chair to be stain resistant for any possible spills that could happen. The tray will also be made of a food safe plastic.

Engineering Analysis

Analysis One

The latch housing is expected to experience significant loading, so it must be designed to withstand that force. We chose aluminum alloy 6061 for its excellent strength-to-weight ratio and durability. In our analysis, the sides and bottom surfaces that are connected to the chair leg were defined as fixed supports, while a 250 lb (1112 N) load was applied to the surface attached to the seat. The resulting maximum stress was 17.52 MPa, which is well below the yield strength of 6061 aluminum (310 MPa). The maximum displacement at the farthest point was only 0.00234 mm, an extremely small value. Overall, the latch housing is more than capable of safely supporting a 250 lb (1112 N) person applying their full weight directly on it.

Analysis two

Stress on whole chair, account for yield strength

Analysis three

CAD Design

Document Fabrication Process

The fabrication process was straightforward, but quite intricate. The team had to learn a lot about how to manufacture certain parts to get them made. There were three major materials we had to work with. The materials being wood, metal, and plastic. Woodworking was done for the majority of the frame. This gave us a solid material that wasn’t too heavy for the chair, as well as a nice finish when the main parts of the chair were fabricated. All of the wood was cut to specification, then sanded to look nice and feel better to the touch. The seat backing and bottom were glued together. The seat was reinforced with a thin sheet of metal to give it extra strength. Finally, the wood was stained to protect the wood and give it a nice look. Metal was used for areas where we needed more strength and stress resistance. Most of our mechanisms on the chair were designed using aluminum. This is what we also used to support the tray and its locking mechanism. The metal parts were much harder to make, due to the need of precise measurements. The plastic parts, except the tray, were all 3D printed. Since the lock for the tray would not be bearing a lot of load, we decided to 3D print it using PETG. While the seat bolt covers and feet covers were 3D printed with TPU. The main part of the tray was cut from a sheet of polypropylene using a waterjet and CNC mill. Polypropylene is a commonly used food safe plastic for cutting boards. Once all of our parts were made, assembly was fairly simple. Some of our holes were a little too small initially, but widening them ever so slightly made all the parts fit seamlessly together. Photos of fabrication: 1-6: chair legs 7-9: seat and backing glue-up 10-13: staining and initial assembly 14-17: Finished links and checking work (feat. John and Skye) 18-20: Tray bracket frame and lock 21-26: Fabrication of seat latches (feat. Gavin) 27: Tray cutout sitting in CNC machine 28-29: Modified wood bracket for tray (photos can be right clicked to open viewing options)

Completed Design & Instructions

Ensure that the seat is latched correctly before sitting in the chair.

Ensure that the tray is secured before placing food on the surface.

Tray is not dishwasher safe, handwash only.

Chair can be transported with the tray and seat in place. It is recommended to remove them for easier transport.

TECH ENGINEERING

FOR KIDS