Team: Rahul Ramnath, Zachory Cannon, Jeremy Gates, Alex Hagedorn, Kyle Schumann

Customer: St. Elizabeth's School

Professor: Dr. Jamie Gurganus

Summary

The goal was to create a toy that kids with disabilities could easily and confidently play with to allow them to do the same activities as other children without disabilities. The CADapult toy was created for children born with disabilities related to poor motor skills such as cerebral palsy and muscular dystrophy and was designed specifically for children at St. Elizabeth’s School. Important design specifications to take into consideration for this toy include: distance the projectile can launch, force to press down the buttons, and dimensions of the geometry of the toy. Other factors that were important to note were the budget of $50 per team member ($250 team budget), and the requirements of two 3D printed parts and at least one mechanism being attached to the toy.

Children attending St. Elizabeth’s School range from ages 6-21 years old. Our toy focuses on an audience on the younger side (6-12 years). The toy is designed to be primarily used by children with cerebral palsy, although any child will have the ability to play with it. Depending on the limitations of a child's specific disability, they may need to be supervised when using the product. The most prevalent reason would be to return the projectiles to the children, but also to monitor safe use of the toy. Our primary customer would be the school itself, as they have children born with relevant disabilities enrolled in their program, and the funds to purchase the product.

To make the toy as safe as possible for children we referenced the US Toy Standard ASTM F963-17 to figure out influential factors of the design. General safety precautions were always kept in mind and Some parts of the toy required covering up to prevent children from accessing them. This decreases the chance of children getting into potentially dangerous situations. A box was placed over our spool and moving parts of our drill to eliminate any temptation to reach near a rotating shaft and motor.

Our toy was constructed in the school workshop during accessible hours. We used relatively inexpensive materials that were reliable and fit our design well. Pine wood was the main material used during construction. The base of the CADapult, the arm, and the base for the target were all made out of sanded and weatherproof painted pine wood. We also utilized plywood in areas that needed a thin base or supporting frame. The remaining materials used include: steel all thread rods, PVC pipe, polyethylene foam, and ABS plastic (3D printed) parts.

The cost of our CADapult was $124.00. The most significant portion of our spending was used to purchase the LED strip lights ($17.99), 18 volt Cordless power drill ($16.36), and the Arduino Uno ($17.60). As our initial budget was $250, we only needed to use 50% of the funding to accomplish our objectives.

From our research on the symptoms of cerebral palsy and muscular dystrophy, the most prevalent traits are the lack of fine motor control and variations in muscle tone. In order to compensate for those disabilities, we redesigned the manual crank system found in traditional catapults to include a motorized mechanism. This feature removed the need for physical strength to operate the catapult. In addition, our design incorporated a pressure sensitive button that activates the device for further ease of use. Our teams catapult design is based on the Mangonel style catapult, as it is the best suited for use as toy.

Jeremy was responsible for the initial research behind our design process and a lot of the planning and developing of design specifications. Kyle, Rahul, and Zach focused on the actual construction and assembly of the CADapult. Alex focused on the construction of the target and the coding for the light activated LED strip. Rahul, Jeremy, Zach and Alex all contributed in making CAD files, drawing files, assembly files, and FEM’s of the CADapult and individual parts of the CADapult.

Design Process

We sent out a survey to potential customers to help gain an understanding of what they are looking for in a toy. Survey results showed that people were interested in our design but it had to meet their provided feedback in order to make them serious about purchasing the toy. The survey results showed that kids strongly prefer to launch a projectile at a higher distance, while adults prefer that the product is durable and reasonably sized for storage purposes.

We examined the customer requirements and design specifications that Assistive Cornhole, a competitor to our product, had developed from their own quantitative analysis. Their product struggled significantly in fundamental aspects of their design, so we made sure our House of Quality had significant weights for these areas of needed improvement. Some of these areas include being able to launch the projectile at the promised distance, and being able to function smoothly without having any operation errors that require manual human assistance. We also took note of the successful features that Assistive Cornhole had in their design because we discovered ideas that already met some of the customer’s requirements like projectiles that follow toy safety standards.

Based on the quantitative analysis of our design, and found on our house of quality, the top priorities for our toy is that it is durable, safe, and easy to activate. We also wanted to make a toy that could launch its projectile at a significant distance. This is important because it gives the children a chance to easily participate with a toy that excites them. Our toy is able to launch at variable distances reliably with a maximum distance of roughly 25 feet. Since the physical therapists and parents are more concerned with the safety of the toy, we covered potentially hazardous areas, smoothed sharp edges, and limited the spring force by limiting the distance the spring can be stretched.

To make the toy as safe as possible for children we referenced the US Toy Standard ASTM F963-17 to figure out influential factors such as viable projectiles and safe materials to use for manufacturing. General safety precautions include making sharp corners and edges rounded, covering exposed threading, and concealing all wires from sight. Some parts of the toy required covering up to prevent children from accessing them. This decreases the chance of children getting into potentially dangerous situations. A box was placed over our spool and moving parts of our drill to eliminate any temptation to reach near a rotating shaft and motor.

We knew that we wanted to use a spring to hold the force that launches the projectile from the beginning. When we met with Assistive Cornhole, we noticed that they used rubber bands to hold a tension force. The rubber bands looked very messy and ultimately failed to hold enough tension to launch their projectile a significant distance. So our main mechanism was going to be a spring attached to our arm that had to be stretched by something. A motorized system is the idea we chose on for the CADapult because this way pushing a few buttons are the only inputs needed to use our toy. We opted for an 18 volt drill to stretch our spring. Our secondary mechanism was our latch system. When the drill turned in reverse after a launch, the tension was lowered and the arm would automatically lower into a gate latch and lock into place. We had a solenoid attached underneath the latch which would push the latch up and release the arm if there was enough tension built up in the spring. The drill was controlled with two buttons on a controller box, one would rotate the drill clockwise, the other would rotate it in the reverse direction. We had a third button on the controller box which would activate the solenoid and act as the “launch” button.

Our toy consists of a base made entirely out of pine wood held together by deck screws that was sanded and covered with weatherproof spray paint. The base was 3 feet long and 2 feet wide. The arm (2.5 feet long) is also made out of pinewood (treated the same as the base), and rotates on a rod of steel all thread secured on both sidewalls of the base. A 3D printed cup (ABS plastic), that is designed to contain a tennis ball, fits over the end of the arm and is secured in place with small nails. A 3D printed pulley (ABS plastic) also rotates on a rod of steel all thread located and secured under the rod for the arm. The ends of the all thread are covered with silicone putty and the exposed threading is covered with thick tape so children cannot puncture themselves on sharp edges sticking out. The drill we used as the source for creating tension was securely fastened to the base with wire ties and covered with a plastic box. We secured a shaft inside the drill with necessary bearings so we could have paracord wrap around a section of the shaft and stretch a spring to a defined maximum distance. One end of the paracord was securely tied around the shaft and the other end was tied around an end of the spring. The other end of the spring was hooked on an eye bolt that was screwed into the end of our arm.

Conclusion

The results of our FEA show that our toy is more than capable of withstanding an average sized 12 year old from falling on the structure. Very minimal deflections will occur, none will be noticeable. From our static analysis it was clear that the gate latch did not experience as much of a load as we initially thought. The chosen latch was strong enough to hold the arm in place when maximum tension was applied.

It was clear from our demonstration day that our toy excited younger children. Every younger child that came to play with our toy was excited and had fun launching the tennis ball into our target and watching it light up. One younger boy played with our toy for 30 minutes straight without getting bored and was consistently impressed. Our toy proved its reliability after working the way it should consistently four two hours. One parent to a little girl that came up to play with our toy appeared to be nervous of our toy based off her body language and facial expressions. We will take note of this kind of reaction and work on making the toy appear safer.

Some changes we would make to the CADapult include covering more of the mechanisms, adding softer materials around the base, adding sound proofing material inside the box that covers the drill, and add an automatic ball return to our toy. Covering the solenoid better and concealing the spring inside some kind of container would help make our toy appear to look safer to customers. By adding padding around the base of the CADapult could help make the toy look softer and more kid-friendly. By implementing some foam or some other sound proofing material inside the box containing the drill would help reduce the noise produced by our toy. We also realized from the demonstration day that kids born with poor motor skills would have a difficult time reaching in our basket and retrieving the tennis ball by themselves, so we want to fix this problem by creating a ramp at the bottom of the basket angled back towards the CADapult. The idea here is to have the tennis ball roll slowly back towards the child so they can pick the ball up off the ground rather than deep inside of a basket.