college of engineering white

Project 7: Improved Tricycle


The goal of this project is to modify a tricycle for a 5-year-old boy with hemiplegia, which is partial paralysis in the left side of his body. This affects his mobility, large and fine motor skills, and his balance. This is a repeat project and as a result multiple therapists had rather long lists of ideas. We quickly recognized that part of our job would be to develop criteria to prioritize the most important thing, or we could get bogged down in endless competing ideas. We prioritized functionality first, with a desire to enable the child to ride the tricycle with minimal assistance. Our secondary considerations are safety, budget, and then some therapeutic modifications to help the child improve his condition. We believe our final design is well-balanced, able to meet the needs of the child and address many of the wants of the therapist.

From left to right: Jordan Chandler, Miguel Fuentes, Mutuku Nthenge, and Brian Hawkins

Problem Statement

The adaptations to be designed for this tricycle are inspired by the limited mobility and motor skills of the left side of the body for the child. This presents issues with the ability to ride, learn, and have fun on the tricycle.

– An adapted handle bar and grip will be installed to help hold the hand on the handle bar while riding

– A pedal with straps will be installed to secure the foot in place while riding

– A new seat with back and side supports with a seatbelt will be installed to improve posture and safety while riding.

Design Specifications

These adaptations to the tricycle will be custom and correspond to his specific needs

Needs to be accounted for: limited mobility for left side of body. specifically the left hand and foot.

The handle bar grip will need to be formed to his finger size so that it will improve his ability to grip the handle. The seat and pedal will also need to be sized according to the rider for safety and comfort.

Background Research

There are other builds of similar tricycles meant for children with disabilities. Those other options were unrealistic because of waitlists for purchasing as well as the price for them versus the prices that would amount to the total of our build. Assessing the models produced by high end companies we were able to piece together a custom unique solution for this tricycle that would be functional and safe yet still affordable.

Concept Design 1

Our goal in this design concept is to achieve the best functionality and comfort

Concept Design 2

Our goal in this design was to solve the problems presented with a very low budget

Concept Design 3

Our goal in this design was to achieve a balance of functionality, comfort, and cost

Selected Concept Design

We chose concept design 3 because it will contain the most adaptable components, and it will be more affordable than concept design 1. The handle bar grip, seat, and pedals will ensure that the child can use this tricycle for years. Also, the techniques used to complete this design will advance our engineering abilities to use for future projects.

Decision Matrix

Overview of Selected Design

Our selected design is the most capable of fulfilling the requirements for the child, therapists, and Dr. Canfield within the time and budget we were given.  We will install a new seat that adds a back support and new pedals that will help keep the child’s feet on the pedals. We will be 3-D scanning and printing a custom handle grip to match the size of his fingers to encourage him to spread his fingers apart and utilize their full potential.

Engineering Analysis 1

As a team we decided to choose the bolt component to create an analysis over. We collectively thought that when it comes to the design of a trike, the bolts holding the seat up-right hold such significant value for the design process. Having an analysis on the bolts, helps evaluate the stress and strain occurring on such component and helps mathematically evaluate the different data collected in our calculations.

Engineering Analysis 2

As a team we decided to choose the bar component to create an analysis that connects the pedals to the front wheel of the trike. The importance of having an analysis on this specific component is to help visualize and gather more information of the distributed forces of the subject’s weight when pedaling. Since, we are studying one side of the trike, the subjects weight(w) would need to be divided by 2, given that weight is distributed evenly throughout the trike ( through both pedals) when seated correctly. The analysis shows what areas of the aluminum alloy bar experience the highest and lowest stresses when the weight of our subject is applied. Through diagrams, we are able to determine our factor of safety of this component, after the findings of maximum weight, reaction force, area of pin, and stress of pin. By using extreme values when trying to find the F.O.S. , we can test the limitations of the trike itself.

Engineering Analysis 3

As a team we decided to choose the vertical bar component on handle to create an analysis over. We collectively thought that when it comes to the design of a trike, this bar component holding the force and momentum of the upper body of the subjects weight holds such significant value for the design process. The mathematical analysis included calculations testing yield strength, torque, and most importantly factor of safety. With the factor of safety we decided to over exaggerate the weight of the subject, so that we could see its’ durability against extreme forces that it will unlikely be held upon.

Bill of Materials

Document Fabrication Process

Doing plenty of research beforehand and measuring parts and where they would go decreased the amount of work required to fabricate our Final project. The pedals only required minimal work to remove the old ones and install the new ones. Use of the shops tools and vice were a must for this installation.

The seat gave us a few issues while putting the components together due to poor manufacturing. With the use of the tolls inside the engineering shop and advice from experienced craftsmen we’re were able to install this without too much difficulty.

To create the unique grip, a model was carved out of flowering foam and fitted to the child’s own fingers. We were then able to 3-D scan this model and then print it in the maker space with a flexible TPU. This will allow for comfort in the grip. The TPU took a very long time to come in.

The electronic components needed some work and wiring management. It was a simple soldering job and then installing back onto the tricycle in a safe position.

Instructions for Safe Use

For safe use the subject needs to be wearing a helmet at all times while using the tricycle. Also, to ride safely, make sure feet are placed firmly into the pedal feet holders.

Project Summary/Reflection

Overall, the goal of this project was to modify a tricycle to the point where our subject can use it with ease and be able to use it as a way of physical therapy for strengthening the muscles. This project was really an improvement based on the previous handlers of the tricycle. As a group we formulated and came up with ideas to improve as much as we can, with the help of funds provided. Our main focus was the stability of the seat, the pedals, and the handles. The stability of the seat was one of the first thins we decided to tackle as a task. We believed by focusing on the seat, it would help every other component fall into place. The seat is the core of the tricycle, it is where every single bit of force is distributed through or from there. After solving the problem with the seat, we moved on to the pedals. The pedals were not too bad of a fix. What we did as a group was research the best supporting bike pedals that could sort of lock one’s foot into place or at least keep it stationary to prevent unwanted sliding. We were able to find many pedals that would help with our desires and all we had to do was deduce it to one of our particular likings, and that is what we did. After the pedals, we focused on the handles, by creating a molded model of handle cover, we were able to 3D print the handles to the exact way we wanted them to be. With all the components finished and assembled, we think that we have improved the tricycle from the day we had it was placed into our possession, and we believe that our goal of improving the use of the tricycle for our subject’s progress in physical therapy is a success.


2022 Spring