The Paper Pulverizer
Zachary Hayden, Justin Maney, Caleb Anthony
EF151 Section C1
Overview
The goal of this project was to create a Rube-Goldberg device that would stamp a piece
of paper. We used parts from around the house, as well as recycled materials and store-bought
objects to construct our device. To activate the device, you release a marble, which initiates a
series of conservation of energy, conservation of momentum, and projectile motion steps to
stamp a sheet of paper. The total cost of the project was about $15.00, and the reliability of the
device is determined by the precise alignment of the marbles. The project was somewhat
successful, as it will complete the task but it is not consistent due to the complexity.
Design Process
The design process began with a group brain-storming session, where we shared ideas
about how to build a stamping device. We watched the You Tube examples listed on the website,
as well as the Honda ad, to get ideas and to understand how Rube-Goldberg machines work. We
followed the requirements listed on the EF151 website during our design process, so that we
wouldn’t have to alter our plans later to get the device to fit into the requirements. We then made
several preliminary design sketches that incorporated our best ideas. The construction of the
device began after collecting useful objects, and modifying them to perform the required tasks. It
took several hours of trial and error to get the device to function properly. We were able to
follow our design sketches fairly closely, but some of the objects we purchased did not work
how we wanted them to, namely the plastic funnel. We also could not modify it to work, so we
just used a plastic water bottle instead, which we were able to modify. The mouse trap and the rat
trap were both too powerful, as the mouse trap over shot the bottle and the rat trap was so
powerful it broke the first time we used it. So, we reduced the number of coils in the traps to get
them to work as intended. We were also able to rebuild the broken rat trap, so we didn’t have to
buy another one.
Device Description
Our Rube-Goldberg stamper project was built on a 0.3m by 0.5m piece of plywood. A
small, glass marble is inserted into a narrow, vertical box made of scrap wood and cardboard,
containing a series of ramps, 10° from the horizontal, made out of wooden interior door trim.
The marble strikes a second glass marble resting at the end, which due to Conservation of
Momentum, rolls down a track made out of quarter inch dowels and through a PVC pipe with a
90° bend, where it activates a small household mouse trap. Attached to the mouse trap is a
wooden spoon, which launches a glass pebble by projectile motion, into an upside-down plastic
water bottle that has been cut in half horizontally. The glass pebble falls through the mouth of the
plastic water bottle and strikes another marble, which rolls down a ramp made of scrap plywood
and activates a large household rat trap. Attached to the rat trap is a wooden crab mallet with a
pre made rubber stamp fixed to the head. When the rat trap is activated, the wooden mallet
swings 180° and violently strikes the sheet of paper, hence the name, Paper Pulverizer, leaving a
dark, heavy stamp that reads “Good Job.”
Analysis of Stored Energy
•
Step 1: Gravitational Potential to Kinetic Energy
mgh = 1/2mv2
32.2*(9/12) = 0.5v2
v = 3.47 ft/sec
•
Step 2: Gravitational Potential to Kinetic Energy
Assuming negligible energy loss and friction,
mava + mbvb = mava’ + mbvb’
(.125lb/32.2)*3.47ft/s + 0 = 0 + (.125lb/32.2)*vb’
vb’= 3.47ft/s
mgh + 1/2mv2 = 1/2mv2
32.2*(2/12) + .5*3.472 = .5*v2
v = 4.77ft/s
•
Step 3: Projectile Motion
y-y0 = (x-x0)tanߠ-(g/2v02)(1+tan2ߠ)(x-x0)2
12in-0in = (13in-0in)tan65-(32.2/2v02)(1+tan265)(13in-0in)2
v0 = 19.5ft/s
•
Step 4: Gravitational Potential to Kinetic Energy
mgh = 1/2mv2
32.2*(1) = 1/2v2
v = 4.01ft/s
•
Step 5: Gravitational Kinetic to Spring Potential Energy
There rat trap packs a ton of force, leaving one hell of stamp!
Bill of Materials
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Dowel - $2.00
•
Mouse Trap - $2.00
•
Large bag of Marbles - $5.00
•
Rat Trap - $3.00
•
Plastic Funnel (not used) - $2.00
•
Scrap plywood, scrap wooden door frames, cardboard, plastic bottle - free
•
Total cost - under $15.00
Conclusions
The project was somewhat successful, as the device did accomplish what it was supposed to do,
but due to its complexity, the device was not as consistent as it could have been. The
construction of the project was tedious and time consuming, and took lots of testing due to the
amount of moving parts. The problems experienced were the trajectory of the mouse trap and
getting everything to fall in place. It took a lot of trial and error experimentation to get the
marbles to actually hit each other, and to get the pebble to land in the plastic water bottle. We
marked the best placement areas for the marbles, so we could get the best reliability possible. We
learned that there are practical uses for all of the lessons we learned in EF151, and we now have
a better understanding of potential energy, kinetic energy, projectile motion, and spring potential
energy. If we could do something differently, we would have built the device with more solid
construction, and also spend more time refining the device to get it to function with more
accuracy. All in all, the project was a success, as we worked well as a team and were able to
complete the project on time, with relatively equal participation.