Our ENGN 234: Dynamics class at UPEI's School of Sustainable Design Engineering has been tasked with creating a snowball launching device. Over the past month, my partner and I have been designing, building, and testing our device. We decided to make a simple slingshot design as making something that works was an important part of this project. This project was done to learn about dynamics and using the engineering design process. We named our creation the Snowball Slingshot.

## Step 1: Materials and Tools

Basic materials and tools are necessary and are as followed:

Materials

• 2" x 2" wood (at least 60 cm)
• Screws (2" and 1/2")
• Wood glue
• Bungee cord (120 cm - this can vary)
• Plastic cup (roughly 8 cm x 15 cm - this can also vary)
• Rigid thin plastic
• Duct tape

Tools

• Drill and drill bits (screw bit and ~.95 cm diameter drill bit)
• Jigsaw (table saw can also be used)
• Measuring tape
• Scissors

## Step 2: Slingshot Frame

With the 2" x 2" wood, measure and cut a 20 cm and a 40 cm piece.

On each of these pieces, a .95 cm diameter hole is drilled near the end of each piece using the power drill. The holes are located 2.5 cm from the end of the wood and should be in the middle of the run of the wood.

Once this is completed, it is time to secure the two pieces together.

The 20 cm piece is attached to the center of the length of the 40 cm piece. Before attaching, make sure the holes that were drilled are on the same "face" (when you hold them up, you will see both holes.) The pieces of wood can be secured using a 2" screw that goes through the middle of the 20 cm piece. It is a good idea to drill a small hole first to prevent potential cracking of the wood. Before the pieces are screwed together, put wood glue on both pieces where they connect to provide added strength. Let the glue dry for about 30 minutes. The two pieces of wood should form roughly a 90 degree angle between the two.

If desired, a thumb protector can be added to prevent the case of the sling shot hitting your thumb while in action. The thumb protector can be made out of anything flexible and rigid. We used flexible and rigid plastic from a cheap garbage can. We cut a piece a 4 cm x 12 cm piece from the garbage can. The protector should be placed over the small V origin of the frame on the side with the drilled holes. It is secured on both sides using 1/2" screws; we left a clearance of 3.5 cm for the thumb to slide through. This can be modified in size to fit any user; this is not necessary for the functionality of the device, but can prevent the need of duct tape band aids on your thumb.

## Step 3: Snowball Chamber

The snowball chamber can be a variety of shapes; our chamber is a rigid plastic cup. It is a normal cup with an exaggerated cone shape at the opening of it. Having something similar to this works well because it is easy to hold at the end, but snowballs fit well in the cone shape at the top. A plastic cup like this could be found at a dollar store or in a plastic dish wear section at a kitchen store. My partner had this gem laying around his house.

The cup is 15 cm in height; the diameter on the bottom is 5.75 cm and 9.5 cm on the top.

.95 cm holes must be drilled into two sides of the cup. It is important to have them exactly across from each other and level so the cup stays symmetrical when in use. After drilling a hole on one side, it is a good idea to poke a pen through and make a mark on the other side to ensure accuracy.

The stronger the plastic is the better; after using the device for sometime, we began to get some cracking in the plastic. We were able to use duct tape to prevent further cracking. Having a couple layers of duct tape on the top and the bottom as seen in the photos above is a good idea. The duct tape acts as a protective layer for the cup and is very good at preventing cracking.

## Step 4: Bungee Cord Connection

The bungee cord used was 120 cm in length and roughly 3/4 cm in diameter. It came with hooks on both sides; but these should be removed by cutting them off with scissors. Different bungee cords can be used to get further launching distances, but this is what we had available.

Once the bungee cord is ready, it is time to connect it with the frame and the cup.

Take one end of the bungee cord and slide it through either hole on the frame. The bungee cord is secured through the hole by tying a knot. A double knot or figure 8 knot works well.

With one end of the bungee secured, take the other end and slide it through the two holes of the cup. After the cup is on the cord, the bungee cord is secured through the other hole using again a knot. The bungee cord running through the cup is what keeps the snowball in position when placed in it

Apply glue to both knots and through the hole to keep the connection fixed. Make sure there is no slack in the bungee cord so the knots are pressed up against the hole/wood.

Once the glue is dried, put duct tape over the connection like seen in photos above for added strength of the connection.

Once this is done, the snowball launcher is complete and is ready for use.

## Step 5: Final Product

With following these steps, the final product should look something like the photo above.

## Step 6: Operation

Operation of the Snowball Slingshot is very straight-forward and is similar to a normal slingshot.

Start by making a nice firm snowball (roughly 7 cm in diameter), then place it in the snowball chamber.

Hold the snowball chamber by the end of the cup behind the bungee cord with your right hand. Hold the frame of the slingshot with your left hand and put your thumb under the thumb protector (or whatever is most comfortable).

Raise the slingshot to about shoulder height; pull the snowball chamber straight back to a comfortable position. When ready, FIRE!!

With our device, we were able to fire a snowball roughly 45 feet on a good launch.

Launch videos:

## Step 7: Reflection and Recommendations

The Snowball Slingshot was fun to design, build, and test. It is a fairly simple device and isn't very difficult to build. It worked just as well or better as our initial expectations. Our device performed fairly well compared to others in the snowball war.

If we were to do it again there are a couple things I would add/change.

• Have some type of magnetic system that could be used to keep the snowball chamber attached to the frame of the slingshot while not in use(suggested by Andrew Trivett).
• Try different bungee cords that are more elastic to see how the launch distance and accuracy change.
• Use duct tape on the cup before coming to the point where it begins to crack.

The Snowball Slingshot requires little materials and resources. The device can be built in roughly an hour for the average handyman.

<p>Nice. I need to make one of these before the next time that it snows.</p>