Project Report

Projectile Intercepting System—

Successfully Build A Ping Pong LauncherA Pong Pong Interceptor

And a Interception Simulator

Information Technology High School

Physics Term Project

Group Name SG2J

Group Members

Stanley Switalski, Shane Arguello,Grace Nam, George Valasquez

And Joesph

Date

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Problem Definition

1 Introduction

Ping Pong Ball launchers integrate many aspects of physics. You need to be able to calculate the initial and final velocities, the highest point of the projectile and where the projectile will land. On top of this, all of these calculations need to comply with air resistance. Although this whole project may seem like a daunting task, this type of interception system is used everyday to protect our country and the military forces. In the military, ships and aircrafts are loaded with anti-missile systems. A camera grabs a visual on the object, and based on that/those images, deploys another missile to intercept it. So, although it has been done by a government agency with a huge budget, we are going to try to replicate this system with our basic knowledge and little budget.

2 Functional Requirements

We must be able to build a Ping Pong ball launcher and interceptor. The Launcher must be able to launch at least five Ping Pong balls

automatically, without reloading, with consistent speed reaching the same altitude and distance each time.

The Launcher must be adjustable. It must be able to adjust the launching angle, the base angle and the initial velocity.

The Interceptor must meet the same requirements as the launcher but it must be able to track the Ping Pong ball and from that automatically shoot a Ping Pong ball to intercept.

3 Performance Requirements

Both the Ping Pong ball launcher and interceptor must launch at least five Ping Pong balls an overall distance of 2 meters.

Both the Ping Pong ball launcher and interceptor must be able to reach angles ranging from 15 to 75.

We must be able to control the RPM of both the Ping Pong ball launcher and interceptor.

A system must be setup so that the propulsion of the Ping Pong balls in both the Ping Pong ball launcher and interceptor is simultaneous.

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Background Study

1 State of Arts

The Ping Pong ball launcher and interceptor were actually designed as we went along. The prototypes on the other hand were derived from two other propulsion designs. The first prototype that involved a CO2 tank and PVC pipe came from the idea of a Paintball Gun. The Paintball gun uses CO2 and a special type of butterfly switch in order to launch a Ping Pong sized projectile at extremely high velocities. The second prototype was actually based off of an Amusement Park ride. A single motor placed underneath a pendulum had enough power to propel people perpendicular to the ground. If we scaled it down so that it would launch Ping Pong balls, we had thought that we would have had enough power to propel the Ping Pong balls.Ping Pong Ball launcher V 1.1 was actually created by mistake. We had initially tried to build our prototype design out of legos but it failed miserably. I had gotten bored and tried to make a car out of the Programming Brick. To no surprise the “car” broke and placed the motors on their side revealing enough space for a Ping Pong ball to fit through. All we had to do now was to build a base.Ping Pong Ball launcher V 1.2 was just an upgraded and heavy-duty version of the v 1.1 launcher. We recognized that the legos would not be powerful enough, nor would they be strong enough. So by using Wood, two 6V motors and foam wheels, we produced a great Ping Pong ball launcher.Ping Pong Ball launcher V 2.0 was pretty much thought of on the spot. we knew that we would need to control the angle of the base and the angle of the platform but we did not know how to control it or what to use. Luckily the owner of Big Apple Hobbies assisted us in getting the materials I needed. We used two servos and a dual servo controller in order to control both angles. As for building the structure, we thought of that on the spot as well. Our initial plan was to build two bases, one would support the servo and the other would support the launcher. However, when it came to building this, we realized that we could cut out the platform for the launcher and significantly increase the strength of the launcher.

2 Research Resource

Although it may be hard to believe, The Ping Pong Ball launcher and interceptor were all of our ideas. We knew that we needed to have an adjustable platform so that we could adjust the launching angle and we knew it needed to be structurally integral. Therefore we decided that the best structure would be to have two motors on the side that would

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propel the ball outwards. Using light wood would help us make sure that the launcher and interceptor were capable of moving without difficulty, and by using small foam wheels we were able to achieve a high RPM with enough friction to achieve our 2 meter requirement. Courtesy of Mr. Lin, we had added a switch that would increase the functionality and ascetics of the launcher.

Key Ideas/Methodologies

1 Key Ideas

One key idea was the idea of using two motors spinning in opposite directions in order to propel a Ping Pong ball.Another key idea was the idea of using two foam airplane wheels so that there would be enough friction to propel the Ping Pong ball without decreasing the speed.Another key idea was the use of bendable metal to securely mount the motors on the side of the platform.Another key idea was the use of double-sided foam tape to space and insulate the motors.Another Key idea was the use of metal railings to ensure that the Ping Pong balls stay loaded.Another key idea was the use of a protractor to determine what angle the Ping Pong balls were being shot at.Another key idea was the use of servos and a dual servo controller to “automatically” adjust the angle of both the launcher and the platform.

2 Methodologies

By using battery holsters, we could easily organize our wiring and ensure absolute safety.By using a carbon fiber rod in the V 2.0 launcher, we were able to cut down on the weight of the overall interceptor.By using four pieces of wood, we were able to stabilize the V 2.0 launcher’s base around a single point of rotation.By using a sinker, we were able to counter act the weight of the motors in the V 2.0 launcher.By using a switch on the V 1.2 launcher, we were able to easily supply or cut off power to the motors.By using battery holsters, we were able to reduce our fire hazard and improve the aesthetics of our launcher as well.

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Design/Implementation/Solutions

1 High-Level Block Diagram/System Specification

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Ping Pong BallTravels up Ramp

via Lego Mindstorm Track

Ping Pong Ball Propulsion System

The Ball meets two Foam wheels

Two 6 Volt motors power two wheels

Three or Five D batteries each power one motor

Friction captures the Ping Pong Ball

Friction combined with a High RPM creates an initial V

Out comes a consistent Ping Pong Ball with a constant initial V

Angles are first adjusted. In launcher v 1.2 it must be manually configured. In launcher v 2.0 two servos control the angles

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2 Detail Design

Our first design took the same concept as a paintball gun. CO2 should provide plenty of thrust on the account that it a paintball gun is able to bruise human flesh.

Our second design took the same concept as an amusement park ride. The single motor underneath the platform should be fast enough to propel the ping-pong ball.

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QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

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The Ping Pong Ball Launcher V 1.1 Used a Lego Mindstorms kit in order to operate. We needed to use their programming language which none of us knew. This only hindered the abilities of the robot. We tried to get the distance between the wheels in the v 1.1, 1.2 and 2.0 launcers to be 1.5 inches (the diameter of a Ping Pong ball).

Ping Pong Ball Launcher 1.2 was based off of the Lego design but used much stronger wood in place of plastic pieces.

Ping Pong Ball Launcher 2.0 was essentially an automatically controlled v 1.2 launcher. It used two servos and a dual servo controller in order for it to move without direct human interaction.

3 Implementation

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We didn’t really have a set budget for this project. As Stanley was in charge of building these launchers, and because he understood that he needed to do anything in his power to build a professional piece of machinery, he did not mind spending the money needed to produce the launchers.

Item PriceLego Mindstorms System On LoanLightweight Pine Wood FreeFour 6Volt Motors $2.99 EachSix Foam Wheels (Two Broke) $2.49 EachSwitch Courtesy of Mr. Lin16 D Sized Battery Holsters $0.99 EachSix rails $0.99 EachTwo Servos $14.99 EachDual Servo Controller $24.99 Each6Volt 300 mA Power Adapter $12.99 EachCarbon Fiber Rod $2.49 Each

Total Cost $119.13 Without Sales tax

If need be, we have videos located at the following URL:http://geocities.com/jimisfender1973/science.html

Testing

1 Test Setting

For testing our launchers, we had recorded launcher V1.2 from the side. Not only did we do this but we also recorded how fast and far the ping-pong balls traveled at certain angles. For launcher V 2.0, we only recorded how fast the Ping Pong balls traveled due to time constraints.

2 Test Results

Launcher V1.2 had launched Ping Pong balls at an average velocity of .0108857 m/sLauncher V 2.0 had launched Ping Pong ball at an average velocity of .00847 m/s* Note: Launcher V 2.0 had two less batteries supplying each motor.

Distance that Launcher v1.2 had shot at certain angles15o 5 Feet or 1.524 Meters30o 8 Feet or 2.4384 Meters45o 11 Feet or 3.3528 Meters

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60o 7.5 Feet or 2.286 Meters* Note: These tests were done when each motor received 4.5 Volts each. We later

upgraded the amount of batteries to include 7.5 Volts each.

3 Interpretation of the Results

Overall we were quite please with our launchers. They had a very good accuracy rate, as proved when we aimed at a single hanging Ping Pong ball, traveled further than our expectations and were more fun than we could stand. However, we felt as though our launchers were lacking in their ability to shoot consistent ping-pong balls. On our 60o

test, the Ping Pong balls all reached a different height. This might be due to the fact that there was not enough time for the motors to spin up to the same RPM as the previous ball shot at.

Conclusion

1 Lesson Learned

Overall, we learned many things about propulsion. The first would be that there are a lot of variables in a propulsion system. You have the angle of the base, the angle of the platform, the speed of the motors in correlation with the amount of voltage they receive and the air resistance just to name a few. Another thing we learned about was that mass is vital to the overall distance of the object. Because we were using an object so light and hollow, it was harder to propel farther. But if we were to propel a more massive object, it might have been easier to propel a large distance (in some aspects).As for our design, there were plenty of ideas that failed. The first would be that CO2 propulsion was not the best prototype in the world. It would be hard to control the feeder and release of CO2 and the amount of CO2 lost is so significant that our results would never be consistent. The second idea that failed was the idea to use one single motor to propel a Ping Pong ball. We should have known that two wheels were the minimum in order to propel a ball. The third idea that failed was the use of Legos in our Ping Pong Ball launcher. They simply were not strong enough to support the propulsion of a Ping Pong Ball. Once we got all of these bad ideas out of the way, everything was pretty much smooth sailing afterwards.

2 Observations/Discoveries/New Problems

As far as our launchers go, there weren’t many observations. I mean everything operated as though it came out of a textbook. The Ping Pong Balls traveled straight, a 45o firing angle resulted in the longest

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distance, 30o and 60o firing angles had resulted in the same distance and the tests were pretty reassuring that our launchers fulfilled a lot of the requirements.As far as discoveries go, we really didn’t make any significant discoveries. The one discovery we did make was that sports themed Ping Pong balls are smaller than regulation Ping Pong Balls.The fact that the sports Ping Pong balls were smaller actually turned into a new problem for us. At the time of building the V 1.2 launcher, we had used the sports Ping Pong balls to space out the motors. Now when the regulation sized Ping Pong balls tried to fit through the wheels, it was a tight fit.Another problem that we discovered was that wood breaks very easily in the cold. The reason the V 2.0 launcher is so fragile is because whenever we went to secure the servo, which is the base, around wood, the wood would always crack. In the end we just wrapped it up with electrical tape and hoped for the best.Another problem was the Ping Pong ball feeder. Unfortunately we could not come up with an effective design that would simultaneously feed Ping Pong balls into the wheels. We tried to remedy this situation by using Lego Mindstorms tracks and motors to bring the Ping Pong Balls closer to the motors; it didn’t work all too well in the V 2.0 launcher. Otherwise, there were no new problems with our original plans.

3 Conclusions/Remarks

In the end, we were quite happy with our results. We had built three prototypes (one not shown due to its miserable failure), three launchers (one failed due to structural integrity) and we able to meet most of the requirements. So far, there were only two requirements that we failed to meet. The first was that our Ping Pong ball feeder was automatic and the second was that the motor’s RPM was adjustable. Although we did try to remedy this problem, as I stated, it didn’t work.While we were building these launchers, we found it hard to believe that no one manufactures these (sort of) hand held Ping Pong ball launchers. This is how much fun we had with this project. Although it did run on the expensive side once we started getting into automation, I wouldn’t mind spending money on one of these toys.

4 Future Outlook/Open Questions

In the future we hope to build two V 2.0 launchers except we hope that the second one is much less fragile. We also hope to use a program that would be able to control the servos. This way we could set up some cameras and have the whole interception system automated. The last and final challenge for us would be to create two mobile units

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that would be able to have a war. By war I mean they should be able to dodge Ping Pong Balls and try to shoot down the other Launcher. However, the questions are can we control the servos, can we build a system that would control the speed of the motors, can we build a mobile platform, will we be able to use the interception logic and apply it to a real setting, will we be able to use cameras to automate the interception logic and will we be able to get this all done without breaking our minds and banks? This is a question only time will tell.

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