Da Cardboard TA Killa
Engineering Fundamentals 151
Spring 2006 Final Project
26 April 2006
John Paul Rose
Josh Murphy
Adam Dillard
Sharon King
Overview
Our Rube-Goldberg device was designed to go through a series of energy conversions, beginning by dropping a marble down a funnel which proceeds to roll down two counter angled ramps then falling into a small basket. The small basket falls down pulling up a gate, in turn releasing a billiard ball which was at rest on a ramp atop of the smaller box. The billiard ball rolls off and falls into a weighted cup which pulls the string over a pulley, pulling the trigger and resulting in a toy dart being fired at a desired target TA.
Designing
We started by storming up a bunch of ideas and finally narrowed down to a few simple steps that combined to perform one final task. We began by deciding what we wanted our device to do, then worked our way backwards. At first we were going to open a bottle by attaching the bottle opener to a string which ran over the pulley, then applying a large force on the other side; however, we were unable to create quite enough force to effectively open the bottle. We tried several different methods but none proved sufficient, and even modified it by adding more weight and lowering the cup to give the billiard ball a little more distance to gain momentum. Eventually we dropped the idea and used the same method of force to pull the trigger of a toy dart gun. This idea worked more consistently because the trigger of the dart gun required less force than the top of the bottle.
Process & Energy Conversions
§ Drawings not to scale
§ Friction, air resistance, and other negligible forces ignored
Step 1: A marble weighing .006lb is dropped down a funnel then proceeds to roll down a ramp with an angle of 31°.
PE = KE
mghi = ½mvf2
(32.2 ft/s2)(1.083 ft) = ½vf2
vf = 8.35 ft/sec
vf x comp=4.3 ft/sec
vf y comp= 7.16 ft/sec
Since we are neglecting air resistance and friction, the efficiency of converting potential energy to kinetic energy is 100%.
Step 2: the marble rolls off the ramp onto another ramp coming to a complete stop. Then the marble starts going down in the opposite direction at an angle of 52°
PE = KE
mghi = ½mvf2
vf= 5.24 ft/sec
vf x comp=3.23 vf y comp=4.13 ft/sec
Efficiency= Eout/Ein
Efficiency = 5.24/8.35 = 63%
Step 3: the marble rolls off the ramp and falls into a make-shift basket which causes a gate to be lifted by the strings looped over a pulley; in turn, the gate releases a billiard ball.
W=F*d
W = (.0066 lb) (.17 ft)
W = .00112 J
Efficiency = Wout/Win
Efficiency = 100%
Step 4: the billiard ball weighing .33 lbs falls into a weighted cup, applying a force over 6 in. by a string over another pulley system
mghi = ½mvf2
(.33 lb)(32.2 ft/s2)(.5 ft) = ½(.33 lb)vf2
vf = 5.67 ft/s
W = F*d
W = (.33 lb)(.25 ft)
W = .0825 J
Efficiency = Eout/Ein = .0825/5.313 = 1.6%
Step 5: the string, acted upon by the force of the billiard ball’s fall, pulls down on a trigger that releases the spring, shooting the dart.
Spring force= ½ k x
Spring force = ½ 1.75 lb/ft (.17 ft)
Spring force = .146 lb
Efficiency= 100%
Bill of Materials
ü Funnel $0.88
ü Toy Gun $0.88
ü Marbles $0.88
ü Cardboard free
ü Cups free
ü Wood free
ü String free
ü Boxes free
ü Paper free
ü Billiard ball free
ü Glue & tape free
Total costs: $2.64
Conclusions
Overall, this project went well. We have to say that we have learned more about the way things work in this class than we learned in our four years of high school. Our team worked very well together and came up with a lot of ideas to begin with and just combined them to perform one final task. Initially we were going to have our device open a bottle, but we were unable to produce enough force to pop it off. Eventually we came up with the idea to shoot a toy gun. We finally overcame any complications we had and got the project done and working at about a 98% rate of efficiency. This project allowed us the opportunity to learn about conservation of energy and efficiency, along with teaching us a lot about each other as people and how well we work together, especially since there are three different types of engineering majors between the four of us. This project also taught us that as engineers, if something goes wrong, then we have to think about why it is wrong, and solve the problem using the knowledge that we gained this semester. If we were to change anything, we would use higher quality materials such as wood as opposed to cardboard to make it sturdier. We would also. But overall, it was fun experience.
References
§ The only references we used throughout this project were our notes throughout this semester from Engineering Fundamentals 151 and Google, which we used to find the weights of the billiard ball and the marble.