Our project involves designing a building a new wheelchair for a 5-year-old boy, made to be multi-purpose and used in both a school and at-home setting. Our main focus is to ensure a safe and effective product that will satisfy his and his family’s every day needs.
Samuel is a 5-year-old boy who suffered a traumatic brain injury and has many needs on a day-to-day basis. He recently started elementary school, and our group was tasked with designing a new wheelchair equipped with several specific features for when he is at school and at home. He isn’t currently ready to use it by himself, relying on family and nurses. He is non-verbal, requiring a special pad called an Eyegaze to communicate with those around him, he has trouble with certain motor skills such as head control and core strength, and their family lives on a farm, which makes it difficult for many standard wheelchairs to maneuver well. Our goal is to incorporate all these needs and improve his overall quality of life to help his future growth and development.
Wheelchair design has many factors that need to be considered. Parameters had already been presented to us for consideration, and that provided plenty of details to consider with research. Mainly we will be covering some of the most important here: Base designs and their advantages, concept of tilt and reclining, wheel types, and comfort padding for wheelchairs
The most important aspect for us to move forward in this project is to understand the importance of wheelchair designs. A multitude of institutions have created parameters and design considerations for people around the world, from the NIH to the WHO. From the research we have obtained, we will be listing the major design points we have to consider and understand.
First of all, since the individual we are designing the chair for is around 5 years of age, we will need to design a pediatric wheelchair. The chair is built for younger individuals with the understanding that the individual will grow in said chair. Support should be provided, while allowing mobility for an interactive lifestyle, and adjustable support for growth and improving posture. Padding and comfort will need to be included, to help protect and support the head and body as the individual grows. While we support the person as they grow, we still have to make the chair both narrow enough to fit through most conventional doorways, but also sturdy enough that the child cannot easily tip over. Proper width and height, as well as wheel choice, will need to be considered in the design.
Next comes the factor of designing based on use. This is mainly focused on terrain and location of use. In a majority of these choices, we have two main forms to choose from, that being rear-wheel drive and front-wheel drive. Rear-wheel drive, where the large wheels are at the back of the seat, is considered the most stable and best for outdoor use, though harder to turn in tight areas and harder to store. Front-wheel drive, the inverse of the rear-wheel drive, has more maneuverability in tight indoor areas with less stability outdoors. Most manual wheelchairs are rear-wheel drive focused, but front-wheel drive versions do exist.
One of the major factors to consider is the use of either reclining or tilting in a wheelchair seat. Both methods are integral to both the comfort and posture of an individual, and is especially important for youth. To determine the best choices, we will need to talk about both methods individually.
A reclining wheelchair is a wheelchair in which the back rest can lean back up to 90 degrees, allowing the user to have a support that can go horizontal. This function can allow a user to go from a sitting position to a lying position at will. These types of chairs are useful for relaxing the back and reducing strain from prolonged sitting, as well as being handy for transportation in compact vehicles. However, many points have to be considered with these, such as elevating leg rests to prevent uncomfortable positions. Just as well, the back support has to be designed to prevent both sliding out of the chair, as well as discomfort from motion along the backrest.
A tiling wheelchair is a wheelchair in which the seat frame completely rotates the chair back, up to 50 degrees. These chairs allow the user to maintain their posture while reducing pressure that would cause sores. These are considered to be the best options for children who are still adapting to posture control. However, with the frame being rotatable, the chair is more static in build, making storage more difficult. Just as well these types of chairs are considered heavier, requiring an aid to assist with mobility and tilting.
Wheelchairs have many details when it comes to both selecting and setting up the wheels they use. For a child, the size of wheel that we would be most interested in would be around 20” in diameter, with sizes ranging up to 24” for adults. The rims can either be spokes or mag, with spokes being more lightweight and providing more comfort, and mags being more durable and requiring less maintenance.
Wheelchair tires can come in a variety of styles and treads for different user lifestyles. Pneumatic tires are the most common used for wheelchairs, with most visibly similar to bike tires. Pneumatic tires help with providing more comfortable rides, and are relatively easy to fix. Most are readily available at a majority of retailers, and are rather inexpensive. However, regular maintenance is required to ensure that the wheels can keep operating, and more outdoor-designed wheels can be much more difficult to use indoors due to the treads. Solid plastic tires are also available, requiring much less maintenance and working especially well indoors. This tradeoff however is at the cost of being more difficult to use outdoors, and has less shock absorption compared to pneumatic tires.
When it comes to the seat, cushion support is a major thing to consider. For a pediatric wheelchair we have to heavily consider the support for the head, legs, and seat to both support posture and reduce strain. With these in mind, the majority of cushions usually fall into foam, air, and gel cushions.
Foam cushions are beneficial in providing structure and stability, helping to boost posture based on the foam used. Foam is very lightweight as an option, and are both readily available and inexpensive. When choosing foam, one does have to be careful as foam can lose shape over long periods, and commonly deforms when under load. Replacement is common with foam, both due to crumbling and moisture retention, as well as being more difficult to clean compared to other choices.
Air cushions are filled with cells that can be inflated to provide support. These cushions are beneficial in dispersing weight, allowing for prolonged use in a wheelchair. The air also helps in absorbing shock from motion, allowing a smoother ride. These cushions do require more maintenance than foam however, with air needing to be resupplied more often. Air cushions are also not recommended for people still adapting to postural correction, and thus are more intended for older users.
Gel cushions are cushions filled with gel pockets that are surrounded by foam. These help to provide comfort and relieve pressure like air cushions, but with more stability thanks to the foam. These are great for more active users and helps to reduce shear forces that can cause damage to skin. However, these are more expensive supports than foam, and are heavier than most other cushion types.
The first design concept focuses on providing Samuel with a reclining backrest to improve comfort and adjustability while maintaining simplicity. By allowing the user to lean back at varying angles, this design emphasizes ease of use and long-term durability, since the reduced number of moving parts lowers the likelihood of mechanical failure. Unlike later tilt or tilt-and-recline concepts, this version prioritizes straightforward functionality and a robust, reliable structure.
To implement this concept, our team is exploring the purchase of a base wheelchair that already includes a reclining mechanism and can be folded for portability. One candidate is the Ziggo Pro Pediatric Reclining Manual Wheelchair, which offers both reclining capability and a foldable frame. Starting from this base would allow us to focus our efforts on custom modifications specific to Samuel’s needs rather than designing the entire system from scratch.
The proposed modifications include:
All of these design modifications will be considered across every design proposal and incorporated into the final wheelchair build, regardless of which concept is selected.
A key design concern is ensuring the wheels can withstand the higher stresses imposed on a wheelchair compared to bicycles. Poor-quality rims or hubs may fail under load, so we plan to carefully evaluate weight ratings and structural integrity before purchase.
In summary, this concept provides a balanced mix of comfort, portability, and customizability. It begins with a proven commercial base and incorporates modifications tailored to Samuel’s specific developmental and daily needs. This design is less complex than tilt-based systems, but it offers immediate usability and a strong foundation for further adaptation.
The second concept for our wheelchair design focuses solely on providing a tilting function, where the entire seat shifts backward as a unit. We also looked into the use of a front-wheel based system, since it was versatile in both outdoor and indoor settings. The best wheelchair system we could find for this design was the Trekinetic K2, as pictured. The design is lightweight and collapsible, features tilt-in-place functionality, and is able to be used for youth with leg supports. The Trekinetic however is a more expensive wheelchair to obtain, and proper head support will have to be considered in the design. Considering Samuel’s needs and the design of the Trekinetic, we will be utilizing Design 1’s modifications except for the Wheel Upgrade.
Using The Karman VIP2 Tilt-in-Space & Reclining Transport Wheelchair for our model design, the third concept for our wheelchair design is made to be a hybrid of concepts 1 and 2, made to both include a reclining back and tilting chair to meet those needs. Along with this, it would be including the arm extension to hold the Eyegaze, durable all-terrain wheels for both an in-school and at-home setting, cushioning to provide comfort and safety to appendages, and the necessary apparatus to hold the activity trays. This design would be the most complex of the three, however it is adaptable to any situation to provide comfort to Samuel when he is at home or in the classroom. With more moving parts than the other designs, its durability might suffer compared to the others, as well as it would take longer to acquire all the parts, as well as modify for Samuel’s needs. It may also become harder to fold and transport with more modifications. (Same modifications from concepts 1 and 2 are used here as well)
For our selected design, we decided to choose design concept 3. Concept 3 has the highest adaptability, which was very important in our opinion. The more adaptable design allows for more flexibility and comfort than the other 2 concepts by a large margin. Also, our selected design includes the features listed above in design specifications including an adjustable eye gaze mount, off-road wheels, supportive padding, and an attachment mechanism for an activity tray. These features will all be added to a wheelchair that both tilts and reclines to create our overall concept design.
After meeting with the beneficiary’s family and discussing their daily needs, our team selected a tilt-in-space wheelchair design as the final concept. This configuration preserves the user’s seated posture while allowing the entire seating system to rotate backward in a single motion. The tilt function enables the child to rest comfortably and helps distribute pressure across the trunk, reducing fatigue and improving posture support throughout the day.
The chair will be equipped with large, off-road-capable rear wheels to allow the family to navigate outdoor environments such as their farm without difficulty. To ensure both comfort and safety, the seating system will include custom-fit padding to match the child’s dimensions and provide continuous body support. Additional head and upper-body supports will maintain proper alignment and prevent fatigue, while a five-point harness will ensure secure positioning during use.
An activity tray will be installed and designed to fold out of the way when not in use, providing flexibility for different activities and ease of transfer. The wheelchair will also include an EyeGaze device mount attached directly to the frame, ensuring stable positioning and compatibility with the family’s existing mounting system.
The modified wheelchair integrates five main design elements: a custom activity tray, an EyeGaze mount arm, enhanced head and lateral supports, and upgraded wheels for off-road use.
Activity Tray:
The activity tray is a custom-built surface that spans across both armrests, providing a stable platform for daily use, play, or communication devices. The tray is designed to fold out of the way when not in use, allowing for easy transfers and storage. It mounts directly to the armrests with lightweight hardware for easy removal and adjustment.
EyeGaze Mount Arm:
The EyeGaze device will be supported using an adjustable mounting arm, similar to the model shown below. Per the family’s request, the existing EyeGaze mount and clamp will be reused, securing directly to the wheelchair’s frame. If necessary, a custom clamp will be fabricated to ensure a firm and vibration-free connection while allowing quick repositioning of the device.
Head Support:
To improve neck stability and reduce fatigue, a modified car-style headrest will be installed onto the existing headrest bracket. This design offers wrap-around lateral support, helping maintain an upright position and preventing the head from falling to either side. The setup will also be compatible with the family’s existing head strap if additional restraint is required.
Lateral Padding:
Cushioned lateral supports will slide over the existing armrests and secure with straps, ensuring snug, comfortable positioning for the child’s trunk. These supports prevent sideways leaning and help maintain a neutral seated posture. Alternate versions extending higher along the seat sides are being considered if greater upper body support becomes necessary.
Larger Wheels and Adjustments:
The wheelchair will be fitted with larger, quick-release rear wheels designed for off-road and farm terrain, giving the family more freedom to move outdoors. Despite the increased wheel size, the overall chair width will remain within ADA compliance, staying under 3 feet wide. The push rails will be removed since they are not needed by the user and contribute unnecessary width. The existing adjustable push handles—requested by the father—will remain in place for ergonomic handling and maneuverability.
Additional Safety and Comfort Features:
To maximize comfort and security, the design includes a five-point harness for upper-body stabilization and additional leg straps for lower-body support. Extra padding will be installed for a proper fit, and all removable cushions can be taken off to allow the wheelchair to fold for transport when needed.
For this analysis, we explored the load of the wheelchair, and how much shear stress that load puts onto the wheel hub. We estimated the weight of the wheelchair, and its user would total 80 lbs. Under this load it was determined that each wheel hub would have to support 40 lbf, and be under a constant shear stress of 50.6 lbf/in^2. The hub of our selected wheel is made from steel which is more than capable of handling this estimated load and will not deform.
For this analysis, we examined the maximum shear stress and bending moment along the activity tray. This tray would be used to support different items for the user to interact with. It was estimated that the maximum load distributed along the activity tray would be 9 lbs. After the analysis it was determined that the part under the most stressful and bending moment would be the base of the tray where it was attached to the rotating joint.
The main things we’re considering when going about this cost analysis is choosing our specific base wheelchair we’re going to be using, as well as working out what we need to order versus what would be easier to see if they had some usable parts from the machine shop. For our wheelchair, we found a couple of websites that gave us good options on ordering the wheelchair we’ll be needing, as we didn’t have much success looking locally for one. There were many different options we could’ve chosen, but ultimately some of the choices didn’t meet our measurement requirements for Samuel, and some of those that did had too long of a shipping time to be feasible for our project. We ultimately settled on one of the higher-priced ones we found that should be of good quality and that should only take about a week to ship. As far as items that we shouldn’t have to order directly, one of those will be the Eye-Gaze unit that our therapist already has, as well as the mounting arm for that. Along with this, our hope is to work with the shop technicians if we need things like bolts or other pieces we may need when assembling our product.
