The 4 P’s:
Propane
Powered
Projectile
Pusher
By: Ryan Jackson
TABLE OF CONTENTS
Abstract- pg.3
Question/Hypothesis- pg.3
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Background Research- pg. 4
Procedure- pg. 5
Materials- pg. 6
Data/Results- pg. 7
Analysis/Conclusion- pg. 8
Bibliography- pg. 8
Acknowledgements- pg. 9
Appendix- pg. 9
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ABSTRACT
Potato guns... When I hear those two words, it brings up
memories of childhood fun. But one question has been haunting
me... Which projectile goes the farthest? This year, I decided to put
that question to the test. It’s pretty simple to build a potato gun.
All you need is a barrel, a propellant, and an ignition system. My
projectiles were a brown potato, a white potato, a green pear, an
Ecuador mango, a small Idaho potato, and an average bouncy ball.
I hypothesized that the ball would go the farthest. I was incorrect.
It turned out that the good ole brown potato went the farthest. I
guess that’s why they call it a potato gun.
QUESTION /
HYPOTHESIS
Question: Which projectile will be launched the farthest out of a
spud gun?
Hypothesis: If weight and friction affect the velocity of a
projectile, then I believe the ball will be projected farther.
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BACKGROUND
RESEARCH
Potato guns have become more and more popular over the
ages. They are not toys!! Many people are hurt by them every year.
Potato guns don’t just shoot out just potatoes, though. These
weapons can also shoot out different fruits and vegetables such as:
tangerines, onions, lemons, oranges, peaches, under-ripe tomatoes,
squash, pineapple, and pears.
Projectile motion is a very important part of potato guns.
Horizontal and vertical motion combine to make the path of a
projectile. No acceleration occurs in a horizontal direction.
Acceleration and velocity play a big role in potato gun
science. Different objects combined with different masses creates
different downward acceleration times. If velocity is changing,
then, by definition, there is an acceleration. Acceleration is an
increase in speed. To see how velocity (rapidity of motion or
operation) increases, we can use displacement values to compute
average velocity at different points.
Materials... well, you can’t make a potato gun without
materials. Some of the materials include PVC pipe, batteries, wire,
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a barbecue igniter switch, and a few squirts of propane.These are
the most common materials, but it is possible to build a potato gun
with different types.
Potato guns have an interesting history. They are very
dangerous unless you take the correct safety precautions. Plans for
them are available on various websites. Potato guns are made
requiring a precise ratio of fuel and oxygen for ignition. Too much
or not enough gas and nothing happens.
Potato guns are very “near and dear” to my heart. Every year
at the 4th of July, we go to a family friends’ house to shoot them.
To wrap it all up, I want to remind you... Potato guns are NOT
TOYS!!!
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PROCEDURE
Create Material List
Acquire Materials
Assemble Spud Gun
Test Fire Spud Gun
Mark off Test Site(ft)
Size Various Projectiles
Begin Testing
- Load Projectile
- Fill with Propellant
- Ignite Propellant
- Measure and Record Distance of Launched Projectile
- Repeat Testing
- Find Average Distance for each Projectile
Clean up Test Site
Finish Paperwork
Mock-Up Display
Final Display
Independent Variable: Projectile
Dependent Variable: Distance the projectile is Launched
Controlled Variable: Spud Gun, Angle of Fire, and the Amount of
Propellant
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MATERIALS
PVC pipe
Glue
Tape Measure
Saw
Lumber
Screws
Propellant
Projectiles
Bar-B-Que Igniter
Scale
½ BRS Stop/ Waste Valve
½ Black Street Elbow
1x ½ BLK Red Coupling
¼x Close Black Nipple
1x 1x ¾ B/R Tee
2 1x8 Galv. Nipple
Brass Pres. Gauge
½x ¼ Galv. Hex Bushing
1 BLK Cap
10Pk 8.5x 6 ALU Drip Pan
2 4” SCH 40 Coupling
¼x 2 Black Nipple
¼x Close Black Nipple
¼” BRS THRD Ball Valve
¼ Black Tee
2 in Fem Adapter
2 2in Male Adapter
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4 oz Cement Weld Kit
4x 2 Reducing Bush
4” SCH 40 PVC DWV Pipe
1- ½ x 10 SCH 40 PVC Pipe
2x 10 PVC SCH 40 Pipe 280 PSI
3 Brown Potatoes
3 White Potatoes
3 Green Pears
3 Ecuador Mangoes
3 Small Idaho Potatoes
1 Bouncy Ball
DATA / RESULTS
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ANALYSIS / CONCLUSION
My hypothesis that the ball would launch farther than any of
the fruits and vegetables was incorrect. The ball we had was
slightly too large for the barrel. Some possible errors were the
wind changing the flight patterns and that every projectile had a
different shape and size. There is also the possibility that the
ground from where we launched was uneven. If I were to re-test
this question, to improve it I would shape every projectile to the
same size and perform the experiment indoors.
BIBLIOGRAPHY
Griffith, Thomas. The Physics of Everyday Phenomena: A
Conceptual Introduction to Physics. Dubuque, IA: Wm. C. Brown
Publishers, 1992
“Things To Shoot” http://www.aaroncake.net/spuds/things/asp.
2 Oct. 2011
“Stoichiometry”6 Oct. 2002.
http://www.shodor.org/unchem/basic/stoic/. 2 Oct. 2011.
Kirby, Robert, “ Kirby: Insights from a backyard potato
cannoneer.” The Salt Lake Tribune. Sep. 2011:
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http://www.sltrib.com/sltrib/lifestyle/52631052-80/potato-gunkirby-sonny.html.csp?page=1. 2 Oct. 2011
Kirby, Robert. Personal Interview. 10 Dec. 2011
ACKNOWLEDGEMENTS
Thank you Mom and Dad for guiding me through another year of
Science Fair. I’d also like to thank my science teacher, Mr. Engstrom, for
giving advice on how to make my project the best it could be. My brother, Ben,
and my sister, Mikeeta, also deserve thanks, for supporting me. Thank you all
so much!
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APPENDIX
1 ½” Barrel
Angle of Fire: 30 degrees
Before Testing
Time: 3:55 PM
Temp.: Approx. 50 degrees F.
Wind: Light NE
Launching: N
After Testing
Time: 4:54 PM
Temp.: Approx. 43 degrees F.
Wind: Very Light E
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