Football Launcher

Football Launcher (Field Goal Challenge)

Alex Kim David Kim John Ngo Charles Yoo McKinley High School

An improved version of the mangonel, the onager catapult enabled medieval armies to launch projectiles at their enemies from long distances, striking fear and wreaking havoc on the battlefield. This siege weapon works by storing tension in twisted ropes in the same way an archery boy does, except it is on a much larger scale. As for the construction of the onager, it is relatively quite simple. All one basically needs to construct one is two beams of wood, twisted rope, and an arm. As to how to operate the catapult, all one really needs to do is to pull the arm back (usually through the use of a sort of crank and gears) and release it. This will cause the catapult to “catapult” its projectiles (loaded on the catapult) in an arc, the distance and height of the project depending on the design of the catapult. Ideally, launching projectiles at a forty-five degree angle from the catapult would result in the launched projectile reaching its maximum distance, but factors such as starting trajectory and air resistance need to be factored in. Launching the projectile at a degree greater than forty-five would most likely result in a higher vertical distance traveled but a lower horizontal distance traveled (for the projectile). However, a launch angle smaller than that of forty-five degrees will cause the projectile to travel greater distances horizontally, but will not remain in the air for long. This means that the optimum angle of launch for the catapult has to be slightly less than fortyfive degrees (factoring in variables such as air resistance) to maximize the horizontal distance the projectile can potentially travel. The design theory that we used for our field goal was to make a catapult, with a launching pad, a base, and a type of crank to wind up the launching stick. The problems that we encountered for our field goal were thinking of an idea for launching of the football, using what kind of wood to make our field goal, and thinking of how to make our launching stick on the base. Our first thought was to use a kind of crank that would gradually wind the launch stick back. However, this required a use of gears, or cogs, in order for the field goal to have a

triggering connection between both the stick and the crank. Rarely do people sell gear parts because we only need about two; one for the crank and one for the launcher. Instead, some hardware stores have gears that come in quite a big package, and that would cost a lot. Another idea we had was to use a spring below the stick, so that it would bounce up and launch the football. The spring needed to be strong and fast so that it would immediately propel the stick upwards and launch our football. We did not know what kind of spring to use because strings were not really made strong to make a large piece of wood fly up quickly. We had a bit of thinking on what kind of wood we wanted to make the catapult out of. We first thought about using regular, unbendable wood because they usually proved the most strongest and durable. However, when the launching pad is triggered, the force of the swing could possibly snap the launching stick, resulting in an automatic failure or disqualification from the event. At first we didn’t really know where to put the launching stick or how long we had to make it. We wanted to have a base that was double times of the length of the stick, but that would require a lot of money. We had to think of a way to reduce the size of the stick and the base. What if we made the width of the stick and the base the same? If the whole thing snaps, the thing would probably tip over or smash because there isn’t any landing space except the ground. The methods that we used to solve these problems were using a level crank and pliable wood. The lever crank is attached to a hole on the side of the base, where you wind it up. We decided to use pliable wood because they are bendable wood and very hard to break apart. It would require a lot of force to bend the wood so much that it would snap. This is much better than regular wood because you need more force to bend at a smaller angle. Our idea for the launching pad was to make its width the same as the base. Now we place a door hinge in the middle of the wood so that it would only bend back half of the part instead of the entire thing. We should also place sponges on the non-propelling side so that

when the other half lands, it lands softly and doesn’t whack against the wood. We don’t want our field goal to have half of it smashed off while the other half is neat. Conclusion Catapults are still used even in today’s modern society, although they do not really serve the same purpose as they used to in the past. One example of such a modern day application is the catapult system that is used on aircraft carriers to launch planes off of the sea vessel (the design may be different but it uses the same principles to launch a projectile – the planes). When you look at the launcher altogether, you could say it is built just like a catapult. To summarize how we made our launcher, it consisted of two parts which was the base and the launcher itself. For the base we started out with three pieces of wood and drilled them together forming something like a stool. For the launcher, it is powered by tension from surgical tubing. We first grabbed a piece of pliable wood, and then took one end of the wood and made two holes. After we made the holes we stuck the two ends of the surgical tubing into the two holes. With the two ends in the holes, you can tie a slip knot and use the slipknot to attach it to our crank. After you have both parts or the base and launcher, we connected the two parts with hinges and drilled them in. So when we crank up the launcher there’s tension in the string and a lot of resistance from the wood, resulting in a strong launch. The highlighting points of this project was the fact that there were many different types of catapults that we could have chosen to do and that the one we chose actually worked especially for us to do this project with no prior knowledge about catapults. The catapult that we made though will always be subject to change if there are any more tests done to it and errors found, could cause us to have to change anything that goes wrong with the catapult that we have now. Appendix Supplies

Wood

Pipe Wrap

Surgical Tubing

Basket

Cost

$17.94

Total

$35.14

$5.24

$10.00

$0.99

Other materials such as pcp pipes and string were found in our own homes and used in this project. Also tools were borrowed from family members and neighbors to conduct this project. After buying all our supplies from Home Depot and also acquiring some supplies from students who had left over supplies from previous such projects we managed not to spend all of our funds. We are left with $14.86 which we will be using to be extra wood and other such supplies in case any of our wood currently being used in the catapult breaks. Our team has all contributed to the buying of the supplies and our splitting the cost between us. Test Data 1st Field goal

2nd Field goal

3rd Field goal

4th Field goal

Trial 1

Hit

Hit

Miss

Miss

Trial 2

Hit

Hit

Hit

Miss

Trial 3

Hit

Miss

Hit

Miss

Trial 4

Hit

Hit

Miss

Hit

Trial 5

Miss

Hit

Miss

Miss

According to our test data our catapult is more than capable of hitting the first Field goal and also the second field goal consistently but as we shot towards the third and fourth field goal it steadily got harder. According to our test data we hit the third field goal forty percent of the time and the fourth field goal only twenty percent of the time. Thus we are being forced to review our designs in the hope of improving our ability to make the last two field goals especially since these two field goals are worth more. We are exploring the possibility of a different placement of the surgical tubing since the placement also determines how well balanced the pliable wood will be. Also ideas have been brought up about the possibility of doubling the amount of surgical tubing used on the catapult to increase the tension and to launch the football farther.