Our group has been tasked with designing and constructing an outdoor swing set for a two-year-old child with strict mobility challenges and developmental delays. Our goal is to create a safe, convenient, and easily accessible play space that allows her to spend time outside with her three siblings. The structure will need to be long-lasting and adaptable to support her growth and future development.
The child is fully supported by a pediatric wheelchair and oftentimes must remain inside. Her mom would like her to have the opportunity to play outside with her three older siblings. This led us to decide to design and build an adaptable swing set. To ensure her safety, we must create a custom-built adaptability swing chair tailored to her individual needs. We also plan to design a sensory board for her to use when she doesn’t feel like swinging but still wishes to play among her siblings. She’s only two years old, so the swing set will need to be long-lasting and big enough to grow with her for 3 to 4 years. The chair must be safe and comfortable for the child, and the swing set and chair setup must be practical and easy for the parents. It must be easy to clean, lock down, and withstand the environment, mainly rain, without issues. All these things are important and will keep the chair useful and safe long-term as the child grows.
For our background research, we focused on key components needed to create a safe, supportive, and developmentally beneficial sensory environment for use outdoors. When considering necessary features for a swing chair, we found that products which feature a reclined position for improved head and back support, along with secure straps to enhance safety, are well-reviewed by buyers and supported by research. We also explored sensory tools that promote focus, motor development, and creativity, such as resistance bands and inflatable seat cushions that provide contraceptive input to improve body awareness and muscle engagement. In addition to this, we are considering chalkboards as a way to encourage creative expression while strengthening grip, dexterity, and hand-eye coordination. These findings guided our decisions in designing a safe, engaging, and skill-building sensory environment.
This design used a child car seat and proprietary mounting system. Since it already has a 5-point harness the only restraint is a neck support which can be attached to the seat via Velcro or another easily removable mounting system. If the swing needs to be locked stationary, there are locking mechanisms on at least two bars. A sensory pad can be included and can easily mount to the car seat arm rests.
This set features a single adaptive swing seat with an attached sensory table for additional stimulation. The swing is designed to cup around the user and includes a supportive harness to keep her secure and properly positioned while she plays. The attached table offers a variety of sensory toys that promote both cognitive and physical engagement. The purpose of this product is to provide a simple, safe, and enjoyable way for her to spend time outdoors with her family while having fun.
We will select Concept Design 2 because it performs well in the categories that matter most for long-term use. This design has the highest scores in design quality, longevity, and upgradability, which means it will be functional and relevant to our family for as long as possible. It also has the highest score in durability and is tied for the highest in safety, giving it a well-rounded profile without any one major weakness or fault. This design may prove to be a challenge since it is the most detailed and will be the hardest to manufacture. However, we believe the complexity reflects a more flavorful structure for the whole family. The added effort in manufacturing is also justified by the long service life and reduced need for future redesigns. Even though it isn’t the cheapest option, we believe its overall performance makes it the most reliable, safe, and hopefully keeps it useful and enjoyable to our family for years to come.
Firstly, for clarification purposes, the selected design is a children’s car seat mounted to a frame and placed on a swing set with other swings. This design centers on creating a stable, adaptable, and long-lasting swing set that meets the functional requirements given by the family now but will also allow for the future growth of the child through simple modification. The core of the system is a repurposed car seat mounted to a custom-designed and built attachment frame. A car seat was chosen because it was built to provide safety and support, it’s also extremely upgradable, as when the child grows out of her current one, another, bigger one can be purchased and remounted. The car seat also comes with integrated restraints and extremely predictable load behavior, as they’ve been highly tested, and we can choose the best and safest option available. We plan to mount the car seat three different ways, which will incorporate several mechanical catches for increased safety. Allowing the removability of the chair will directly support longevity by preventing long-term wear and tear from weather exposure and allowing for upgradability of the car seat rather than the need to redesign the whole swing set.
Additional cushioning will be added to the seat to provide targeted support where it is most needed and improve comfort. The seat will be suspended using four chains, each surrounded by a thin rubber tubing. The tubing will prevent pinch points for the children, prevent wear and tear and environmental damage to the chains, and also provide a very predictable friction interface for us to use. We worried about the chair swaying and damaging components of the swing set on especially windy days, so we will also add a mounting system to the ground and bottom of the chair.
The swing set structure itself will be a standard A-frame configuration. This geometry was selected for its easily understood load paths and the ease of adding multiple swings if time and budget prove available. We are hoping to add a swing for each sibling, and as such, the entire design has been planned to accommodate as much play as possible for the siblings while still meeting the child’s needs.
We also plan to integrate a sensory table into the design as an auxiliary feature. It will mount to the side of the A-frame, and the middle can be detached and connected directly to the main chair. We plan to have a storage system for toys in the middle in order to hopefully allow for everyone to remain involved and have fun even when the swings are not in use. This upgrade will not add any risk to our design structurally but will greatly increase the range and functionality available on our swing set.
Child Seat and Mounting System Safety:
The central component of the design is the child’s seat, which uses a repurposed automotive car seat due to its high level of built-in safety and support. Car seats are highly engineered to protect children during dynamic motion and include integrated harness restraints that securely hold the child in position in the event of swinging. We will also be providing additional cushioning targeted at comfort and improved support during extended use and swinging. The seat is attached to a custom mounting frame that incorporates multiple mechanical locking catches, ensuring the seat remains securely connected during operation. This mounting system also allows the seat to be safely removed when necessary, reducing weather exposure and allowing future seat upgrades as the child grows. The seat is suspended using a four-chain system, which improves balance and prevents unwanted rotation compared to a traditional two-chain swing. Each chain is enclosed in rubber tubing to eliminate pinch points, reduce wear from environmental exposure, and provide an additional layer of safety for the child.
Based on seats we have researched our child’s height and weight. Our seat will be somewhere within these ranges, and our mounting system will be adjusted to fit these dimensions perfectly.
Car Seat Dimensions
| Dimension | Typical Seat Size |
|---|---|
| Height | 24–28 in (61–71 cm) |
| Width | 18–21 in (46–53 cm) |
| Depth (front to back) | 20–24 in (51–61 cm) |
| Seat height from base | ~10–12 in |
Swing Set Structure and Multi-Child Safety:
The swing set structure follows a conventional A frame configuration, as it is known to offer great stability and clear load paths that direct forces safely into the ground. This design enables the frame to support three swings so that multiple children can use the system simultaneously. The frame materials are chosen for strength and outdoor durability, so the swing set can survive rain, sunlight and temperature swings. Heavy-duty swing hangers and high-strength chains are used to support the dynamic loads created during swinging. Similar to the main seat suspension, the swing chains are covered with rubber tubing to prevent pinch points, reduce wear, and improve overall safety.
Based on three swing sets we have researched. Our swing set dimensions are going to look like these. The actual swings will be set: left swing 2.5 ft gap, Center car-seat swing 2.5 ft gap, Right swing.
Swing Set Structural Dimensions
| Component | Researched Dimension |
|---|---|
| Top Beam Length | ~10–12 ft (3.0–3.7 m) |
| Swing Spacing (center to center) | ~24–30 in (61–76 cm) |
| Frame Height | ~7–8 ft (2.1–2.4 m) |
| Frame Width (leg spread) | ~6–8 ft (1.8–2.4 m) |
| Ground Footprint Length | ~8–10 ft |
Sensory Table Feature:
To incorporate play opportunities beyond the swings, a sensory play table is also integrated onto the side of the A-frame structure. The in-line design means it’s mounted firmly to the frame not affecting structural stability of your swing set. The surface also serves as a safe space for toys and activities, so children can stay engaged even when the swings aren’t in use. A storage for toys is also included in the table to enable communal play while ensuring a safe and organized enviorment.
FEA and Stress Validation of Mounting System
A mandatory analysis that must be done to any engineered structure is FEA and stress validation.
The strength criteria includes:
FEA Setup:
Results:
Static Structural Analysis of Swing Frame
In order to verify the structural integrity of the swing set frame, a static analysis was performed on the top beam of the A-frame structure. The top beam was modeled as a simply supported beam between the two frame supports, with loads applied at the swing mounting locations.
Each swing attachment point was designed to withstand a maximum load of 800 lbf, which accounts for the weight of the child, dynamic forces generated during swinging, and an additional safety margin. The loads were applied vertically downward at the mounting locations along the top beam.
Since the structure contains four swing attachment points, the total applied load on the beam is:
Ftotal=4(800)=3200 lbf
Using equilibrium equations, the reaction forces at the two supports can be determined (RA, RB and RC= reaction forces at the supports)
∑Fy=0
RA+RB+RC = 0
Because the loading is symmetric along the beam:
RA=RB=RC=1067 lbf
The beam experiences bending due to the applied loads. According to beam theory, the maximum bending moment occurs near the midpoint of the beam span, which corresponds to the region of highest stress observed in the simulation results.
The bending stress in the beam can be estimated using the flexure formula:
σ= Mc/I
where M is the bending moment, c is the distance from the neutral axis to the outer surface of the beam, and I is the moment of inertia of the beam cross-section. The calculated stress remains significantly below the yield strength of the selected structural steel material.
The results of this analytical calculation are consistent with the finite element simulation, which showed the highest stress occurring near the center of the beam while remaining well below the material yield strength. This confirms that the swing frame is capable of safely supporting the expected loading conditions.
The analysis confirms that the swing frame can safely support the applied loads at the swing mounting points. Both analytical calculations and FEA demonstrate that stresses remain below the yield strength of the material. Therefore, the swing structure satisfies the required safety and structural performance criteria.
Comparison of Alternative Materials for Mount System
In this analysis, we researched several steel materials to determine their suitability for structural use in a table design format. The materials considered include 1010, 1018, 1020, A36, 1215, 1045, 4130, 4140, 4340, and 304 Stainless Steel. The evaluation criteria include machinability, yield strength, and material cost, which are summarized in the corresponding table and labeled 1-5 with 5 being the best suited (lowest cost, highest yield strength, highest machineability percent). More weight is given to cost and yield strength as those seemed more important for this project.
Results
As seen in the table, lower-carbon steels such as 1010 and 1018 both provide moderate strength with good machinability for a relatively low cost. Medium and alloy steels such as 4130, 4140, and 4340 offer higher strength but come with increased cost and reduced machinability. A material like stainless steel (304) offers corrosion resistance but has a lower machinability and higher cost compared to the other materials. Taking all this into account, it makes sense for us to choose either 1045 or 1215 steel when aiming for the best balance between yield strength, cost, and machinability. With that being said, 1010 and 1018 low carbon steels are readily available for use while still providing good values.
The fabrication of our project was mainly focused on building a custom metal mounting frame for the adaptive car seat our child uses. We began by cutting all our steel tubing into the correct lengths and angles, we printed off a life size dimension drawing ensuring the frame would be large enough and strong enough to support the child for the next ten years. After cutting, we ground every edge smoothly to remove burs and prepare the surfaces for welding. We then cut and bent the sheet-metal panels that form the actual base and back rest supports. Once all components were prepared, we welded the entire frame together and finished it with a durable purple powder-coat to protect it from weather and long-term outdoor use.
The sensory table was built from wood, starting with cutting each plank and sheet to its required dimensions. We then sanded all edges and surfaces smoothly, to ensure it was as child safe as possible, finally we assembled the full table structure. After assembly, we sanded one more time, before adding weatherproof chalk paint to the tabletop and weather resistant outdoor paint to the remaining table.
To ensure a strong and reliable connection between the mounting frame and the swing set, we used 500‑lb rated carabiners and 700‑lb rated chains.
We purchased the swing‑set frame itself, and our fabrication work focused entirely on constructing the custom metal mount and the wooden sensory table to complete the final design.
Once the frame was assembled, several team members sat on the swings and hung on the bar to ensure it was secure. The set itself performed well and was safe and ready for normal play. During installation and testing, we decided that the system connecting the frame to the ground, although adequate, could be improved. This led us to bring concrete during our next visit, which the family decided to wait on and have at their disposal. That being said, we are confident that it will meet the family’s needs for years to come.
For the mount itself, the welds were inspected and met the requirements we had designed it for. It held the car seat securely and held together with no problems when lifted by its chains.
In summary, our final project ended up deviating significantly from our original concept build, but those changes ultimately made the design stronger, safer, and more long-lasting for the family. The biggest shift came from Dr. Canfield’s recommendation to use one of the child’s existing seats and have it be detachable rather than fabricating a fully custom adaptive chair. This change allowed us to design a removable mounting system that prevents long‑term weather damage and allows the setup to adapt much further than we initially thought possible as the child grows and transitions into larger seats over the next ten years. Another major deviation came from material constraints: our initially selected metal (steel 1215) was far too heavy and expensive. Although it was very safe with our design being able to hold up to one thousand pounds, we felt it was a little much due to the cost and weight, and opted for something better suited. So we redesigned the mounting frame around more realistic materials like low-carbon steels 1010 and 1018, but this change didn’t compromise strength or safety, as our frame could still hold eight hundred pounds, but at a much more reasonable cost and a weight of only forty pounds. We also removed the padded inserts from our design because the family’s car seat already provided all necessary support, and we eliminated the ground‑anchoring concrete system after the family informed us they may be moving soon and did not want anything permanently fixed into the yard. Despite these changes, our team learned valuable lessons about adapting a design to real-world constraints, communicating with a client and meeting their needs, and solving problems as they arise in a time crunch. The result is an extremely durable, weather-resistant mounting system and sensory table that will meet the family’s needs for years to come.
Disclosure:
Our family is moving and very busy. To make things simpler for them, we were asked not to fully assemble the project. Instead, we completed and delivered all three pieces individually so they can put it together later. Once things settle down, they will send us pictures, and we will update the website. For now, the three delivered parts are pictured below.
