Frisbee Throwing Device - Rose-Hulman

Frisbee Throwing Device
Final Report
Submitted to
The Faculty of Catapult LXIII
Rose-Hulman Institute of Technology
Terre Haute, Indiana
Group 6
Deanna Miller
Andy Welsh
Courtney Thomerson
Isaac Wafzig
University High School
Heyworth, Illinois
Oldenburg Academy
Batesville, Indiana
Lexington Catholic High School
Versailles, Kentucky
Terre Haute South Vigo High School
Terre Haute, Indiana
July 3, 2008

6-1
Introduction
Frisbee throwing started in Connecticut with Yale students and a baker. William
Frisbie’s pie pan proved easy to throw and light weight, the perfect combination for a Frisbee.
After World War II plastic advancements made it possible to make the Frisbee what it is today
(Lorenz, Ralph D. 2006). In order for a Frisbee to fly it must spin as it is propelled forward. This
spinning motion is what allows the Frisbee to glide through the air and go great distances with
relatively little force. The spin is the characteristic that sets the Frisbee apart from a sphere
shaped ball. The historical problem with a Frisbee, however, is a person cannot play Frisbee
with themselves as they can with a ball. The purpose of this project was to construct a device
that would allow a person to play catch with themself. The goal of this device was to mimic the
distance and speed that an average human throws a Frisbee. This distance was tested by all
members of the group throwing four Frisbees each, and an average distance of 15 meters was
found from this data. This distance became the goal distance for the device. In building the
device it was also a goal to have it work on its own and have no need for human contact between
throws.
Method
In the process of constructing a Frisbee throwing device many prototypes were designed.
The designs were originally complex but became more simplistic as the design process
continued. It was found that more complex and intricate designs proved impractical and unstable.
The number of moving parts required to make the device had to be kept at a minimum to have a
greater chance of success. The transition from complex to simple mainly focused on reducing the
number of moving parts. Three main designs were debated before the final design was approved.
The first design resembled a human arm and was very similar to clay pidgin thrower. It
consisted of an PVC pipe, “arm” with a curved piece of metal “hand” at one end. This assembly
was to be attached to a stationary point at the end opposite the hand. It was then to be spun
around at a high speed and the Frisbee would be thrown from the arm. (Fig-1) The curved hand
would give the Frisbee the desired spin to make it fly. This design was rejected because of the
complexity of the reload system that would be needed in order to have the device reload a new
Frisbee into the hand without human contact.
Side View
Arm Rotation
Plan View
Figure 1-First design of Frisbee throwing device

6-2
The next design was very similar. In addition to a motor, a spring was used to propel the
arm. (Fig.-2) The motor wound a string around the main shaft the arm was attached to. On the
end of the string was a spring with one stationary end. As the string wound the spring was
stretched. When the motor released the string the spring would recoil and cause the arm to swing
and throw the Frisbee. However, the same problem of an overly complex reload system was
found, and this design was also eliminated.
Figure 2-Side of second design
The final design was much like a pitching machine (Fig.-3). It had two wheels spinning
in opposite directions that were spaced the distance of a Frisbee apart. The Frisbee would be fed
between the wheels and be propelled forward. If the speeds of the individual wheels were
different then the Frisbee could spin as well as go forward. A Frisbee holder would be erected
behind the device with a chain and hook to pull one Frisbee down to the machine at a time. This
design became the final design because it had far fewer moving parts and was not very complex.
Top View
Wheel
↓
Front View
Wheel→
Figure 3- Final design of Frisbee throwing device
A Frisbee catching device was also considered to remove any physical contact. This
never got past the planning stages due to time constraints and unforeseen problems. The Frisbee
catcher would have been a simple design involving a net or sheet that was set at a slight angle to
catch the Frisbee and allow it to slide into the Frisbee container.
Construction
Construction began by building a basic model and then making small modifications as problems
were found. The first problem encountered was that the Frisbees were twisting upon making
contact with the wheels. The first attempt to solve this was to install a single rail made from

6-3
Plexiglas. However, this proved to be inconsistent. The rail was widened to a platform (Fig.-4) to
improve stability and an additional platform was installed on top to further control the disk. A
slot was cut in the middle for later installation of a guide system and cuts had to be made to
accommodate the wheels and PVC supports.
Figure 4- Platform (2 ft x 1ft 2 in)
Once these adjustments were made trials became more consistent and reliable. Another problem
encountered that was unintentionally solved by the platforms was getting the Frisbees to make
contact with both wheels at the same time. A third problem that presented itself was propelling
the Frisbee the desired distance. This was solved by the addition of two bungee cords at the rear
of the device to sling shoot the disk with the desired force. Additionally, one fan motor was
upgraded to a weed whacker motor to help with both propulsion and spinning.
The next step in construction was to find motors to spin the wheels. Two simple fan
motors were chosen to power the device. Both motors were 120 volt motors that had three speed
settings. Two 5.5 inch diameter lawn mower wheels were found, each weighing 370.8 grams.
The frame from a box fan was used as the base for the device. A 1’x 3’ piece of plywood was cut
and used as the base for the motors and wheels. Generic 10 inch diameter Frisbees were used to
ensure consistency of the launch. Custom made axle extensions were fabricated to fit the wide
diameter of the wheel axle holes to the narrow fan axles. The extensions were fixed on the
motors with simple set screws. In order for the Frisbee to be propelled forward the wheels had to
spin in opposite directions. This was achieved by simply turning one of the motors upside-down.
The rig holding the upside-down motor was originally a piece of plastic from the original fan that
supported the motor while pieces of plywood elevated the motor. For purposes of stability the
rig was redone with a custom fit piece of wood supporting the motor and PVC piping to provide
elevation. The new rig reduced the vibration of the motor.
The newly designed rig was later changed with the arrival of the new electric line
trimmer motor that was obtained and installed on the opposite side. The change to the rig was to
return the upside down motor to right side up. This was necessary because the new weed
whacker motor spun in a different direction than the fan motor. The new motor also was shaped
differently than the previous one and required modification to the design to accommodate it.
These modifications included drilling a hole in the board that the original motor was attached to.
This was necessary because the new motor was slightly taller than the old motor and had to sit
lower in order to be level with the second motor. The weed whacker motor was also lacking the
screw holes that were conveniently located on the fan motor. This problem was solved by
creating a vice like grip out of two pieces of plywood. Two holes were drilled in both pieces and
bolts were driven through each with the fan motor in between this secured the motor and
prevented it from spinning out of place. The pieces of plywood were then attached to the board
with two angles mounted on one side to allow ease of adjustment of the vice that held the motor.

6-4
With the new position of the motor the device had to be turned around for the Frisbee to be
thrown in the correct direction. This rendered the previously installed hinges useless. The angle
of launch was still adjustable however by wedging scrap wood underneath the front end of the
device.
The new motor was also much more powerful. This caused the lawn mower wheel to spin
much too fast, almost to the point where it would spin the tread off the axel. This was corrected
by securing the rubber to the plastic inner part of the tire with duct tape. The torque produced by
the weed whacker motor also presented a problem. The force of the motor caused the entire
device to shake violently. This shaking was so dramatic that it caused the fan motor to stop
running. The problem was partially resolved by creating a new axle to attach the wheel to the
motor. The wheel was also grinded down to balance the spin.
The weed whacker motor had benefits as well. It produced much more spin on the
Frisbee due to the increased power. This is crucial to prolonged flight and the stability of the
disk. The amount of spin the new motor produced was much greater than the fan motor and
increased the potential output of the device. (See figure 5)
Results
Figure 5 – Final Design
Once the device was completed, testing began. The first test involved keeping the voltage
on the trimmer motor constant while varying the voltage for the fan motor. The graph below
shows the result of this test. The best result, 13.9 ft, was achieved when the motor was at 0 volts.
The test at this voltage was the only one to generate spin on the Frisbee. This spin caused the
Frisbee to be much more stable in flight, thus allowing it to fly further.

Figure 6- Fan motor voltage vs. distance
The second test involved keeping the wheel attached to the fan motor in a fixed position while
varying the trimmer motor voltage. The graph below shows the results of this test. The best
result, 13.8 ft, was achieved when the motor was at 50 volts.
6-5

6-6
Figure 7-Trimmer motor voltage vs. Distance
Through additional tests, the furthest distance thrown was approximately 23.5 feet. Given more
time and more powerful motors a further distance would be well within reach. Overall, the
concept was proven. The only problem was limited resources and time.
Analyses
The results were obtained depended on four main factors, power of motors, difference in
voltage, force propelling the Frisbee forward, and elimination of human error. The more
powerful trimmer motor gave the Frisbee ideal spin to keep it in flight. A large difference
between speeds of the motors also gave the Frisbee ideal spin. This spin caused the test to be
more consistent and reliable. The bungee cord attachments gave substantial amounts of force
that propelled the Frisbee forward. However, the bungee cords also created inconsistency in
testing due to the human error in pulling them back and releasing them to launch. Over all the
results obtained are in direct relation to the force propelling the Frisbee forward and the spin of
the Frisbee once released.
Conclusion
Throughout the course of the project several challenges were encountered that had to be
overcome. The first was coming up with a practical design. In the beginning the design was
much too complex for the experience level present in the group. After much debate a relatively

6-7
simple design was decided upon. Another problem that presented itself was getting enough
power out of the motors to throw the Frisbee to the desired distance. This challenge was met first
with installing bungee cords to the rear of the device to get the Frisbee moving faster. A larger
motor was later installed to increase speed. Also the wheels were trimmed and unnecessary parts
of the inner part of the wheel were removed to lighten it. Another idea that was considered was
increasing the size of the wheels to get a greater speed. However larger wheels would weigh
more and therefore require more power to move possibly reducing the revolutions per minute
(rpms). A third major problem was unfortunately time. The original design involved building the
device such that it would be able to throw multiple Frisbees without human interference. This
was to be achieved through a Frisbee container being mounted on the rear of the device. The
Frisbees were to be stacked on top of on another and be pulled into the wheels with a bike chain
that would have a hook like device attached to it that would snag the lip on the underside of each
disk. The chain was to be powered with the same motor powering one of the wheels, which was
to have a gear system also attached to it. The limited budget was not a problem however.
In order to make the device more efficient, more stable materials could be used to prevent
the motors from wasting energy by vibrating back and forth. Also more powerful motors could
have been used. In the end the goal was not met.
Bibliography
Ralph D. Lorenz (2006). Spinning Flight Dynamics of Frisbees, Boomerangs, Samaras,
and Skipping Stones New York, New York: Springer