Ping Pong Ball Launcher

Mechanical Design

Wentworth Institute of Technology

Boston, MA

Group 1

Engineers:

Marc Driscoll

Peter L’heureux

Skylur Jameson

Robert Wong

February 25, 2009

Professor Ali Moazed

Wentworth Institute of Technology

Boston, MA 02115-5998

Dear Professor Moazed

We are submitting to you the report that you assigned due on the date of February 26th, 2009. We were assigned as group number one and our team consisted of me, Marc Driscoll, Peter L’heureux, Skylur Jameson, and Robert Wong. The project was labeled as a minor project and focused on us creating a ping pong ball launcher. There were certain restrictions that we had to follow and our goal was to have the launcher launch five ping pong balls into a designated bucket. The contents of the project mainly focused on us following the design process and completing an accurate technical report. If there are any further questions feel free to contact any of the four engineers involved in the project.

Sincerely,

Marc Driscoll

SIGNATURE PAGE-

Marc Driscoll25%

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Skylur Jameson25%

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Robert Wong25%

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Peter L’Heureux25%

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Contents

ABSTRACT-

INTRODUCTION-

BACKROUND INFORMATION-

METHODOLOGY-

ALTERNATIVE SOLUTIONS-

FINAL DESIGN SOLUTION-...... 15

CAD DRAWING-

CONCLUSION-...... 18

RECOMMENDATIONS-...... 18

MATERIALS USED-

CONSTRUCTION PROCEDURE-

RECORDS OF TESTING –...... 21

BIBLIOGRAPHY-...... 22

MICROSOFT PROJECT GANT CHART-...... 23

SAMPLE EMAILS AND NOTES-

ABSTRACT-

Thegoalfor our group is to design a ping pong ball launcher. The launcherneeds to be designedto launch one single ping pong ball one at a time over a setobstacleand into abucket of a desired diameter.The goal isfor the launcher to have the capability to launch five ping pong balls one at a timeinto thebucket within one minute,havingnon of the ping pong balls bounce out or miss the bucket. The launcher can be made out of any material desired and canlaunch the ping pong ball in any desired way, except by explosion.

Our groupdebated on which methodwe thought would create the most accurate and predictable launcher.We pondered upon a catapult type launch but instead designed a launcher thatused the capability of hitting the ping pong ball into the air rather than flinging it. We designed a base for the whole launcher with a ramp and aslot forthe "carriage”. The carriage was used toslide down a desired slot, then let go of thus sliding back down the slothitting the ping pong ball off a ramp and overthe obstacle into the bucket.

INTRODUCTION-

This semester my group members and I, all being mechanical engineer majors, are taking a mechanical design class to understand the design process. This process is used in today’s industry to develop new products and re-engineer existing products. We as a group, and class, are learning to understand how the design process works and the history behind it; which helped to develop the process into its current form. Together, with lectures and homework, we were given our first of two projects to complete this semester. This project is designed to give us “hands on” experience with the design process.

The project our group members were given to complete was to design, construct and give a demonstration of a ping pong ball launcher. This launcher must be capable of shooting a ping pong ball one meter to an obstacle, that stood one meter high, go over the obstacle and continue another meter and land in a bucket. The bucket dimensions are 0.3 meters in diameter and 0.15 meters in height. The launcher must be able to shoot at a rate of five ping pong balls a minute. However, it is prohibited to launch multiple balls at once. Also, the launcher, being self contained, must not be greater than a meter high and no explosives or any other “risky” means of firing may be used.

Working within these requirements our group set out to develop our design. The following report is a depiction of our group’s thought process and the means by which we developed and constructed the ping pong ball launcher.

BACKROUND INFORMATION-

The ping pong launcher project's purpose is to allow students to design, build, and showcase a specific designed launcher that will shoot one ping pong ball at least two meters in distance into a 0.3 meter wide pail with a height of 0.15 meters. The launched ping pong ball must also clear a one meter high obstacle before it lands inside the plastic pail. Furthermore, the design requirements detail that the launcher must be able to launch five ping pong balls per minute, noting that only one ball can be loaded into the launcher at any one time. The project constraints list that the launcher itself must not exceed the height of a single meter while also being a "self-contained" piece of equipment. There may not be any chemical mixtures, explosive charges, or firearms or hair dryers attached or included into the ping pong launcher's design. Lastly, each group must place their one submitted launcher either on a table or the ground and will be given five minutes to setup their project and display to the class that the launcher will be able to shot five ping pong balls within one minute into the plastic pail. Each group will be awarded four percentage points for each ball that rests in the bail at the end of their minute while two percentage points will be awarded for each ball that bounces out of the pail and zero percentage points for a ball that misses the pail entirely.

METHODOLOGY-

The goal of this project was to be able to construct a ping pong ball launcher and get it into a receptacle. Groups were assigned to design and build a launcher on their own first by creating sketches and then transferring them to AutoCAD, and finally constructing the launcher with materials they decided upon. Groups had to come up with alternative solutions to the design they finally picked and had to argue for and against each design.

With our group we picked a design that launched a ball by hitting it and shooting up a ramp, which would in theory keep it a fixed straight line every time. By pulling back the lever attached to an elastic band at the same distance every time, we could accurately shoot a ping pong ball the same distance and angle every shot.

After building the design, we tested our design on different instances. The ball was not shooting straight every shot like we predicted when choosing our design. We modified the ramp by adding a support on the bottom to help corral this problem. It helped, but on occasion the ball would shoot off to one side. We decided that this problem was caused by the lever hitting the ball at a different angle and point at each time. To fix this problem, we held the launcher down tighter and also turned around the lever so it would hit the ball on a flat surface. During our last test, we added new borders on the ramp to keep the ball shooting straight. As noted from our previous tests, on occasion the ball would sail off to one side. We hypothesized that this was caused by spin being put on the ball and to fix this we added the sides to cut down on the balls spinning motion.

ALTERNATIVE SOLUTIONS-

Design 1:

This design is most closely related to the typical catapult. Two triangular supports rise from the base to create both a stop for the launching arm and a place from which the tension is originated. A shaft spans the distance between the two supports and a rubber band (used to create tension) is draped over and attached to the launching arm. The launching arm is hinged and secured to the base creating an upward directional path for the opposite end. With the rubber band attached to the launching arm press the end down stretching the rubber band. Place the ping pong ball on the end of the launching arm and release. The rubber band quickly compresses to its original state and the shaft causes the launching to abruptly stop. The ping pong ball, not affected by the shaft, continues on its trajectory and is launched into the air.

This being one of the most basic and simple designs to create projectile was one of our first design ideas. However, we did not decide to incorporate this design because we decided it would be difficult to predict the ping pong balls direction and distance once it was launched. There were many variables to take into consideration to get the design to work well.

Design 2:

This design works on the same principal as a baseball bat with a few alterations. The design starts with a base on which a ramp is attached to give the ping pong ball trajectory. Next a rod is attached in a manner that it is hinged at one end to the base. The rod is allowed to swing freely like that of a base ball bat. Again, a rubber band or spring would be used to create tension for the rod to react to. Next two screws would be strategically attached to the base to create a stop for the rod and a holding point for the ping pong ball. The ping pong ball would fit loosely and by pass the two screws enough for the rod to hit it as the swinging action takes place. The ping pong ball would then be launched off up and off the ramp becoming a projectile.

This design had much potential; however we decided not to go forth with the design because of a lack of consistency. We believed to ping pong ball would have multiple possible paths to take after it has been launched off the base. So due to unpredictability we looked for another design.

Design 3:

This design would have worked similar to that of a cannon minus the explosive pressure need to create the projectile. We start off with a base from which everything would be attached. Next a piece of PVC (or other type of piping material) would be mounted to the base at an upward angle. The inside diameter would be greater than the diameter of the ping pong ball. The pipe would also have to be close to the size of the ping pong ball and not too big. Next a lever hinged and attached to the base would be placed by the lower opening of the pipe so as to hit the opening of the pipe where the ping pong ball would be seated. Again the lever would be spring loaded or attached to a rubber band to create tension. The ping pong ball would stay in the pipe and not roll out by the use of a piece of plastic loosely fastened to the lower end. The ping pong ball would then be placed in the upper end of the pipe and allowed roll down to the end. The lever would be pulled back and released hitting the ping pong ball and launching it out of the pipe.

This design seemed to be a plausible solution to our problem at first. However, as we investigated more into the idea we realized the idea would not work as planned. We believed the ping pong ball would hit the inner wall of the pipe and spiral on its way out loosing velocity to the point where it not go very far; if it left the pipe at all. We had based our idea on a cannon. However a cannon requires a tight fit between the projectile and the inner wall of the barrel. We would not be able to have this tight fit, low tolerance clearance with our design unless we adapted some type of pressure release, like compressed air. This would have just made things more complicated so we decided to not use this design either.

Design 4:

The fourth ping pong launcher design that our group created involved the concept of using a pendulum to hit the ping pong ball. The idea behind the pendulum launcher was that two columns, parallel to one another, would be attached to a small piece of wood, by either glue or the preferred choice of screws, to serve as the base for the weighted pendulum. In order to attach the two columns of wood together, we decided to use a thin metal or wooden cylinder and place it securely between the columns, allowing for our pendulum to move freely in all directions. Once the base of the structure was designed, we choose to attach a solid piece of wood to the cylinder with a heavy mallet head at the end of the solid piece of material. Aplastic ramp would be glued to the small, square piece of wood at its very edge. Extending from the ramp to the point of impact would be a pathway that would either be lined with thin cardboard or rather cut out half an inch to ensure that once the ping pong ball was hit, it would have a track to follow before arriving at the ramp.

Overall, the concept and design of the pendulum launcher had much upside however we discovered that it also possessed many variables. Trying to get the pendulum to swing straight and hit the ping pong ball head on seemed to be too inconsistent to deem usable without further reconstruction. Also, because the pendulum could only generate a certain amount of velocity, if we increased the speed of the pendulum there might be a small variation at where the impact point was made on the ping pong ball thus resulting in a path that did that follow along the desired path of projection.

FINAL DESIGN SOLUTION-

We decided to settle and construct this design because it seemed to have the characteristics we were looking for with the reliably we required. The design started with a base slightly elevated off the ground. The base was then cut in half in order to create a slot. Next, a carriage was designed to rest in the slot so it was not able to more drastically on any of the three axes. The carriage would not be able to tilt left or right, rotate left or right and pitch forward or backward. However, at the same time the carriage would fit loose enough in the slot to slide easily front to back. At the front of the base a set of ramps were attached from which the ping pong ball would gets its trajectory. The carriage would be attached to a rubber band which was also attached the front of the base beneath the ramps. The ping pong ball is then placed at the base of the ramps and not allowed to roll in the slot. The carriage would then be pulled back creating tension. The carriage would then be released and travel down the slot hitting the ping pong ball pushing it up the ramps. The carriage would pass between the ramps and hit the front of the base causing it to stop. The ball would continue on it path up the ramps and become a projectile on its course to the bucket.

We decided upon this design because we believed it would have the best and most reliable accuracy of our design ideas. The trajectory would always be the same in theory. The ball would not fly off to the right or left because it would be caught in between the ramps as it was launched. The forced the ball was hit with by the carriage could easily be altered. Lastly, we believed it would have the most constant results. So as a group we designed and built the launcher and will be conducting tests in the near future to collect data.

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CAD DRAWING-

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CONCLUSION-

In conclusion, our final design satisfied the project parameters that were issued to the class at the start of the project. The requirements instructed the group to build a launching device that could shoot a ping pong ball close to 2 meters in length, over a 1 meter high obstacle into a small 0.3 meter wide by 0.15 meter tall pail. After successful test completions and adjustments to the launcher, it is safe to say that our final design could be implemented and reproduced at a later time to meet another assignment that shared the parameters of this project. We can confidently stand by our design because the recorded data displays that as our group spent more time working on the design, the more accurate the ping pong launcher became, resulting in more ping pong balls landing within the small pail. However, though our final design is reliable, our group concluded that it comes with a small percent of unpredictability. The risks and impossible obstacles we encountered settling with our final design were that it could randomly become inaccurate. We determined that this inaccuracy was inevitable because the design required human contact to hold the device down and pull the carriage back, imposing small changes in velocity and reference angles onto the ping pong ball. Furthermore, the course of projection the ping pong ball followed could also be significantly changed if the cardboard lining the ramp was moved or involuntarily hit because the tape holding the walls down could lose adhesiveness and become less of a support system. In the end, though the design process was difficult, frustrating, and included numerous deliberations, our final design successfully met and hopefully surpassed the issued requirements.