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Project 13: Adapted Tricycle


The purpose of our project is to modify a tricycle for a six-year-old boy who has varying control on his left side. Due to this varying control, we will need to focus on supporting his left side so that he can ride his trike without falling and hurting himself.
Dominic Alfini, Mikael Delelegn, Caden Holmes, Erik Jones, Roy Netlandsnes

Problem Statement

The main problem we face is that our child has varying motor control on the left side of his body and is unable to safely ride his trike without risk of falling off and being injured or being unable to control it on bad days. He also is unable to reach the pedals and handlebars easily due to the position of the seat being too far back. On bad days he also has difficulty turning or even holding onto the handlebars.

Design Specifications


  • A seat that can move forward and backward
  • Back support that can move forward and backward
  • Sides that can swing out and lock to allow entry/support while riding
  • Left-arm support to keep his arm close horizontal
  • Potential steering assistance

Technical Requirements

  • A sliding mechanism with a pop-out pin can allow 1 direction of movement
  • A bucket seat or spring locking mechanism can give side support
  • A motor or leveraging mechanism can give steering support

Background Research

The following is a company that specializes in modifications like these:

Discovery Series

Some of their designs have been looked at and considered for our designs. These include:

  • Pedal levelers
  • A secondary steering
  • Pin-held pedals to allow movement without pedaling if the pin is pulled.
  • Tilted seat with adjustment
  • Body-centered pedals

Concept Design 1

This design includes the following modifications:


The handles are curved fully. A vertical post could be used as hand support if the therapist thinks it’ll work well. A wrist and arm strap are located on the left side.


The seat has a push-out pin that can lock. This will allow the seat to move forward and backward as well as up and down. The back support is attached to the seat and can also move forward and back.


A single side support comes out of the seat to the left. It can be moved left and right as well as up and down.


A right-side flap support can swing and lock in place to give right-side support. This mechanism would have a spring force pulling it open. Once rotated all the way in, it would lock in place. Pushing back in would unlock it and allow it to open again. This is similar to the design of a retractable pen.


The left pedal will have foot straps to lock the boy’s feet in place while riding. If the therapist recommends, a string could be attached to the tip of both pedals. This will tilt one pedal up as the other tilts down.


Concept Design 2


The Handles of the previous design did not hold the Child’s hand in place comfortably. This design includes a glove that can be worn by the Child with a Velcro texture to attach to the handle. This allows for an adjustable grip position and added comfort


The Seat is attached to the frame via a slot and two bolts. one bolt is for stability while the second can be hand tightened using a knob to pinch the frame and hold it in place.

The seat also has a bucket-seat shape that keeps the Child from slipping out. The backrest can also be adjusted by the therapist as the Child’s needs change.


A armrest style support is used that folds up vertically and is attached at the back of the seat. The position of the hinge and armrest can be adjusted using a Allen key for quick modifications.


The current front wheel will be replaced with a lighter thinner wheel more suitable for indoor terrain. This reduces the effort needed to turn the handlebars and makes navigation smoother.


Concept Design 3


The design for the handles would be focused on full accessibility because on bad days our child is unable to open/close his hand well at all. It would consist of a rigid case for the hand that can open and clamp itself shut for easy hand insertion. There would also be an attached strap/handcuff style wrist constraint so that he can push and pull his arm and still turn the trike without having to hold the actual handle.


The seat would be a bucket style seat to support the sides of the child and assist in preventing him from falling off the trike. It would also have an adjustable pin in the style of modern weightlifting equipment with the handle on a rod to hold the seat into place.


The side support would act in the same way as the desk on auditorium seats (The seats in room 215). and would be easy to deploy as well as having the added benefit of being optional for days when the child does not need it.


The Pedals would be modified in such a way that it would be easier for a child’s foot to fit inside and would also lock to the ankle so that the bottom of the foot would not be needed to pedal.


Selected Concept Design

We decided to go for a design incorporating elements from each design. This allows for the final product to have the best features.

Decision Matrix

Overview of Selected Design

The selected design features handles with Velcro straps. The frame of the bike is modified so the seat can move further forward. The armrest is a soft material that can be adjusted in height. The pedals have smaller straps that fit the child better.

Describe Design Details

The pedals aren’t shown because they were ordered online. They are smaller than the original ones and fit the child better. The armrest is made of neoprene and can be adjusted in height easily with a pin. It can also be completely removed if the child is having an easier time with muscle control. The seat is a bucket seat, which provides more stability than a traditional bike seat. It can also be adjusted forward and backward with pins. The handles have velcro straps which help the child hold onto the handles easier.

Engineering Analysis 1

Here is a graph of the force on the pedal vs. Torque output. The equation is: T(x) = x/3   (per pedal)

Document Fabrication Process

We made a few modifications during fabrication to the original design. The modifications allowed an even easier fabrication process while achieving the same results.

We found that the current frame position could work if the seat could move forward more, so more holes were drilled into the seat bar to allow the seat to adjust further forward.

We also kept the original seat frame because it had the ability to rotate. This now allows forward position and rotational positioning.

Testing Results

The first stage of changes was put to the test when Grayson was able to ride the trike for the first time. The major objective of this test was to find out if the trike is comfortable for him to ride and operate, and to ensure that his arm is held securely in a neutral resting position. The key here is to help him build muscles that promote a healthy arm position, this is something that a standard trike does not do.

After analyzing footage of Grayson riding the trike and getting himself seated and position it was clear that some changes could be made:

The armrest seemed to be too far out from his body and his arms didn’t reach out as far as we had expected. It was also noted that after riding the trike around for a short period of time his left arm would pull out of the strap on the handlebars and would contract to his chest. To combat this a additional support would be needed to help keep his arm from moving outward and upward, away from the resting position. The final design shows this modification. The other systems on the trike such as the bucket seat and the pedals with straps proved to work well. The seat was able to be positioned to where he could reach the pedals and handlebars comfortably. With assistance getting strapped in, the pedal straps also made propelling the bike easy.

The changes are shown in the last 2 images on the right: a PVC pipe was cut lengthwise down the middle to function as a comfortable slot for this wrist to rest in. The intent of this addition is to ensure his arm stays in a resting position and to reduce the chances of him pulling his hand out of the handlebar strap when turning. Since the changes were made after Grayson’s first ride we are still waiting to hear back about how these additions performed.

Instructions for Safe Use

As this is just a trike, safe use would follow safe use for any trike. It shouldn’t be used on public roads. With the child’s condition, he shouldn’t use it without supervision either.

Project Summary/Reflection

This project was very enjoyable and unique to most projects. This one had a real-life effect on someone’s life. Our team really appreciated the ability to help Grayson with something he usually wouldn’t be able to do.


2023 Spring