Rube-Goldberg Door Bell Ringer
EF 151 C1 Fall
December 05, 2006
Team Members:
Gregory Bandy
Joshua Carrigan
Paul Donnelly
James Huff
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Summary
The objective of our project was to create a device that uses conservation of energy to complete the task of ringing an electric door bell. The device utilizes four different phases of conservation of energy to complete the process.This task had to be able to operate in a safe and non-destructive manner. Our team had to complete our project outside of class time and we were not allowed to exceed a twenty dollar limit for supplies.
Design Process
The design process is much harder than it appears. We first got together as a group and began brainstorming. Our ideas came out verbally and in sketches. With many ideas we all decided that we did not need a very complex project to stress us all out. Our design came from a motto, “short, sweet, and simple,” in that we did not need a complex project to distinctly describe a few energy conversions. When we actually started to construct our project things had to change as testing failed or did not appeal. Our first idea was a ball would go down a ramp onto a pipe level to the ground. It would then hit three balls attached to an arch by string, like a Newton’s Cradle. The momentum would carry over and hit a fourth ball that would go along the pipe until it hit a spring and came back. We did not use that idea because we agreed it was too complex. We noticed that if we took the cradle out, there would still be enough energy conversions. This did not work out because there was no task being completed in the project. To put a task into our project, we decided to ring a bell. Our first idea was to have a ball go down a ramp to a pipe level to the ground. It would then hit a post that was across the pipe. The post would have two bells, hanging by string from an arch on top of it that fell into the pipe when the post was hit. The ball would then go down the pipe hit a spring and come back to hit and ring the bells. The result of this device was not very efficient or appealing. We then decided to go a little more complex and appealing. Our next test was for a ball to go down a ramp into a pipe level to the ground until it hit a spring. The ball would hit the spring with enough force the compress the spring and push a button in the middle of the spring. Hitting the button would complete a circuit to ring a doorbell. Unfortunately the ball never hit with enough force to push the button, but we liked the idea of the doorbell and had to stay with it.
Final Product
Our final product is much like our initial products. It consisted of the ramp to a pipe level to the ground, spring, and doorbell. The final product allows a ball to roll down the ramp to a pipe that is level to ground. In the pipe is a hanging switch that when activated completes the circuit to ring the doorbell. The ball then goes on to hit the spring and bounce back.
Description and Illustration of Energy Conversions
Energy Conversion 1
The ball starts from rest and is dropped from an initial height of 58.42cm
Energy Conversion 2
As the ball falls, 0.751 Joules of gravitational potential energy
is converted to 0.751 Joules of kinetic energy. Just before the ball reaches the end of the its free fall, it reaches a velocity of 3.386 m/s.
Energy Conversion 3
This kinetic energy is transferred to the electrical lever switch as the ball collides with a metal post connected to the switch. A small spring inside the switch is compressed with an energy equal to the kinetic energy of the ball. This action completes and closes the electrical serial circuit between the bell and battery.
While the circuit is closed, negative ions travel from the negative terminal of the battery through the switch and bell and back to the positive terminal of the battery. As the electrons move through the bell they oscillate a circuit which moves the bell armature back and forth thereby ringing the bell.
As the contact force of the lever is insufficient to stop the ball it continues pass the switch towards a spring at the end of the run.
Energy Conversion 4
As the ball travels down the endof the run, it collides with a spring and is bounced in the opposite direction back towards the ramp. The spring is compressed 34.5mm.
Bill of Materials
All Figures in U.S. dollars
1. All Wood Material0.50
2. PVC Piping0.75
3. Door Bell6.00
4. 6 Volt Battery0
5. Ball Bearing4.00
6. Lever Switch5.00
7. Spring0.25
8. Screws0
9. Nails0
10. Glue0____
Total Cost: 16.50
Conclusion
Our team was successful in accomplishing our task of ringing the electric door bell by using conservation of energy. It made us work as a team and utilize our time to create a device to fit the criteria. The project was also field tested by personswho were not affiliated with our team (Hooters Girls) and the testing proved to be successful as well. Our team initially had some design problems, but we were able to work together to redesign the device. One thing we learned was that there is a distinct line between what you can design and what you can actually build. We came up with many ideas that would have been amazing, but with the time and resources allowed we could only build a few of the ideas. We also observed that although we say that the energy was conserved everywhere, there were more external forces acting on the ball than we calculated. Lastly we understood that great engineers must build things for good technicians. An engineer can think of something great and build it, but it needs to be able to be used by the technicians. Our main problem was finding a task that we liked. The task went from Newton’s Cradle to ringing bells to switching on a doorbell. The doorbell appealed to us, so we used the idea even though the first test with the button in the spring did not work.
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 research how various electrical switches worked.
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