1 Engineering Fundamentals final project: Jerry Built 25 April 2009 Ashley Gleaves Korey Hamilton Joel Sausman Jack Smodic The following team members have read and approved of this report: Ashley Gleaves, Korey Hamilton Joel Sausman, Jack Smodic
ii Abstract Our project is a compilation of some of the concepts that we covered in EF 151. We used projectile motion, conservation of momentum and energy, center of mass, and rotational energy concepts as a basis for our design. Our design consists of a main platform with a see-saw like device. In addition, there is a tower with a weight attached to it which is positioned above the see saw. In front of the see-saw there is a funnel sunk into the platform. This funnel is the target for the see saw projectile. The funnel has a tube attached to it so the marble falls below to the second platform. The marble then triggers a spring which shoots an additional marble through a short PVC pipe. Opposite the pipe is a thin pole that rests on a platform and extends to the top platform. This pole holds a golf ball, positioned on a ramp in place. Upon the shooting of the marble, the pole drops, causing the golf ball to roll down the ramp, and off the platform turning on a light. This was a great capstone project because it not only encompassed all of the concepts that were discussed in class, but it also provided for experience in design, teamwork and versatility.
Page 1 Introduction Our main objective in this project was to design a series of energy transfers to complete one simple task. Another objective we had was to have at least five energy transfers. We referenced many concepts covered in EF 151 as the basis for our design. We used concepts such projectile motion, collision, center of mass, conservation of angular motion, and conservation of energy. Our design starts with stored energy and goes through a series of events to release the energy to accomplish our simple task. We successfully combined these two goals and developed a device capable of turning on a lamp. Design Process The design of our device changed over the course of the project. We decided what to do based on what was feasible and what worked the best. Initially, we had some ideas that while they looked good on paper, didn t pan out well in real life. For example, we had wanted to launch multiple balls and send them down different tracks. However, this proved to be too difficult to do and we abandoned the idea. We decided as a group what we wanted to do when a problem arose. This challenged us to change our design and remain flexible. Moreover, this inevitably led us to change our design to meet the constraints and at the same time solve the problem. Most of our criteria for what we did was centered around the constraints that we had to follow. One thing that was designed on paper, and then changed to work in real life was our projectile mechanism. The design process for this project was more or less, draw part on paper, attempt to construct in real life, and then implement on the project. Out of all the parts, only two were successfully transferred from the paper drawings to the actual project. Those were the spring, and the projectile mechanism, however, the mechanism took some time to perfect. Another design issue we ran into was the electronic device that we wanted to use. Initially we wanted to use an alarm clock, but the golf ball was unable to push the snooze button. We then
Page 2 decided to attempt to find a Staples easy button, but were unsuccessful in locating one. We then thought of a device that had easy access to a switch from above that would turn on and off without difficulty. We settled on a lamp with a switch easily depressible from the top. Device Description Our device is built around one large, central platform standing about half a meter off the ground on four legs. A tower supporting a bolt extends from the top. This tower holds the bolt above a popsicle stick see-saw balanced across a small beam. The popsicle stick is balanced with the bottom disc of a can on one side and the weight of a small steel ball on the other. A short distance away from the see-saw, a funnel is placed in a hole in the platform. This funnel is surrounded by a curtain of paper to prevent misfired steel balls from getting lost. On the other side of the paper curtain is a golf ball. The golf ball is held at the top of a popsicle stick ramp by a narrow stick going through a small hole in the platform. Hanging from the bottom of the main platform is a second, smaller platform. The funnel from the top platform has a tube leading down to the second platform. The hook of a gate latch is attached to a short post on one end of the platform and the loop is placed on the other. A spring stretches from the loop to the hook and is held in place until a force directed by the tubing pushes the hook off the spring. Another steel ball sits in groove, barely touching the loop. Set up slightly under the hanging platform is a third platform. Resting on this platform is a short section of PVC pipe lined up with the steel ball on the second platform. The PVC pipe leads to the base of the stick that supports the golf ball. This stick sits on top of a water balloon
Page 3 to keep it from slipping. Sitting separately from the device is the lamp which is operated by the device, placed in front of the golf ball ramp. The total cost to team members was around fifteen dollars. We purchased an assorted box of springs, a hook gate latch, a box of nails, two bolts, two funnels, a screw, and three steel balls. Of these, we only used two steel balls, the gate latch, one spring, one bolt, and one funnel. In addition to these, we used wood, tubing, and PVC pipes from Estabrook s supplies. We got string and a water balloon from other teams and golf balls were provided by Zach Inman and Joel Riddle. Our initial electronic device, an alarm clock, and the lamp were provided by Joel Sausman. Testing Results 1. The stage of the lug nut suspended from the PVC pipe and dropping onto the stick: 2. The center of mass of the stick: = Center of Mass [Eq. 3] CM =.09 m from the left of stick. 3. The stage of the steel ball being projected from the catapult to the funnel: ) ( [Eq.4] = v [ Eq. 5]
Page 4 Table 1: Values of theta and the corresponding values of velocity Theta Velocity of ball in x direction ( 50.781 55.852 60.935 65 1.04 70 1.17 75 1.36 80 1.68 4. The stage of the ball triggering the spring as it is released from the hook: [Eq. 6] = v [Eq. 7] v = 1.53 = v 5. The stage of the spring transferring energy to the steel ball. [Eq.8] [Eq.9] 6. [Eq.10] 7. [Eq. 11] 8. The stage of the gulf ball rolling down an incline plane : [Eq. 12]
Page 5 9. The stage of the gulf ball falling from the edge of the project to the switch on the light: mgh = [Eq.13] => The results we received were what we expected based on our design and what we anticipated would happen. When we used equations to determine what some of the actual values were, we found that they made a lot of sense and would expect to receive a similar result given only the equations to work with. Here are some of our results: according to equation 1 and 2 we found that the weight dropped at about 1.87 m/sec. Moreover, according to equation 3, we found the center of mass to be at.09 m from the left of the stick. After the weight hits, the ball is catapulted into the funnel approximately.1 m away. We were unable to find the exact value of theta, however, using equations 4 and 5 we found values for both theta and the velocity. These values are represented in table 1. As the ball goes down the funnel, it is understood that some energy change occurs, but we are unable to determine this as of yet. Next, we found out the latch s velocity, using equations 6 and 7, to be 1.53 m/sec. After that, we found the energy transfer of the ball to spring ball with equations 7 and 8, giving us a value of 2.30 m/sec for the latch. Next, we found the speed of the ball after the spring hit it to be 3.54 m/sec using equations 9 and 10. Then, we found the speed of the golf ball as it rolls down the incline to be.108 m/sec from equation 11. Finally, we found the speed of the ball as it hit the lamp switch to be 1.72 m/sec from equation 12.
Page 6 Conclusions This project taught us a lot about physics. Up until this point we have dealt solely with theoretical calculations and demonstrations. Once we started working on this project, we realized very quickly how difficult it is for calculations to match up with actual occurrences. Slight variations in placement of our see-saw and location of bolt impact especially showed us how drastically small variations affect physical outcomes. We also learned valuable problem solving and brain storming skills when something does not go according to plan. We learned patience with experimentation and with team members. Not to mention we learned how to physically apply concepts we have been studying all semester. Overall, this project was very beneficial to solidifying class material in our minds, and in getting realistic team engineering design and development experience.