What are the best energy sources for building a high pressure cannon?

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Discussion Overview

The discussion revolves around the construction of a small cannon intended for recreational or educational use, specifically focusing on the energy sources suitable for achieving high projectile velocities. Participants explore various aspects including the necessary pressure (PSI), potential energy sources, and construction techniques.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant inquires about the PSI required to achieve projectile speeds of approximately 100 m/s with a 7-gram projectile, suggesting CO2 as a potential pressurized gas.
  • Another participant shares an unrelated anecdote about a vinegar and baking powder reaction, indicating a personal experience with pressure release but not directly addressing the original question.
  • A participant calculates that 100 psi would exert about 50 pounds of force on a half square-inch area, leading to an initial acceleration of 32,000 m/s² for the projectile, and discusses the importance of choosing an appropriate energy source.
  • There is mention of using hairspray as a combustion source for potato cannons, along with a suggestion to experiment with combustion chamber size based on the expansion of burning hairspray.
  • The original poster asks for examples of energy sources for experimentation and expresses curiosity about how to build air pressure in a tank, questioning the effectiveness of practical compressors.
  • Questions are raised about the PSI exerted by paintball guns and the speeds and mass of paintballs, indicating interest in comparative energy sources.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the best energy sources or methods for building the cannon, with multiple viewpoints and questions remaining unresolved.

Contextual Notes

Participants express uncertainty regarding the effectiveness of various energy sources and the specifics of construction techniques, such as the capabilities of compressors and the design of combustion chambers.

Who May Find This Useful

Individuals interested in DIY projects, physics enthusiasts, and those exploring the mechanics of pressure and projectile motion may find this discussion relevant.

dekoi
For recreational/educational purposes, i am looking into building a small cannon which would shoot projectiles of about 1.0 cm in diameter. I would like to gather some information regarding the PSI needed to reach high velocities (roughly 100 m/s) with a projectile of mass around 7 grams. Should CO2 be used as the pressurized gas? Would anyone provide a rough outline on how i would go about building high pressure, welding the barrel, etc. ?

Thanks. :smile:
 
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on a somewhat unrelated note i noticed that you could fill a wine bottle with vinegar and baking powder, quickly stuff the cork in and when the cork flew out it went maybe 30-40 feet if i did it fast enough.

lol i know this isn't really answering your question, and truthfully i don't really know how to make your cannon-ish thing but i thought it migt at least tell you what to expect. and its a terrible mess if you want to try doing it, do it outside where you don't have to clean up too much.
 
T@P said:
on a somewhat unrelated note i noticed that you could fill a wine bottle with vinegar and baking powder, quickly stuff the cork in and when the cork flew out it went maybe 30-40 feet if i did it fast enough.

lol i know this isn't really answering your question, and truthfully i don't really know how to make your cannon-ish thing but i thought it migt at least tell you what to expect. and its a terrible mess if you want to try doing it, do it outside where you don't have to clean up too much.
Hmm. Well thanks for trying. :smile:
 
No physics majors able to help?
 
Well, 100 psi (for example) would apply about 50 pounds of force to an object that's about a half square-inch in size. 50 pounds of force is about 200 Newtons. Solving f=ma, an object of 7 grams mass would experience an initial acceleration of about 32,000 m/s^2. If you could sustain that pressure for about three milliseconds, you'd get your projectile up to 100 m/s.

You'll have to choose your energy source wisely. Most potato cannons just use hairspray and a simple piezo-electric igniter like those used on gas grills. You might have to do an experiment to see exactly how much the burning hairspray expands, and therefore how big the combustion chamber would have to be, etc.

Keep in mind that 100 m/s is a pretty good fraction of the speed that most bullets have when leaving the barrel of a gun -- be careful with this device, no matter how you choose to build it.

- Warren
 
chroot said:
Well, 100 psi (for example) would apply about 50 pounds of force to an object that's about a half square-inch in size. 50 pounds of force is about 200 Newtons. Solving f=ma, an object of 7 grams mass would experience an initial acceleration of about 32,000 m/s^2. If you could sustain that pressure for about three milliseconds, you'd get your projectile up to 100 m/s.

You'll have to choose your energy source wisely. Most potato cannons just use hairspray and a simple piezo-electric igniter like those used on gas grills. You might have to do an experiment to see exactly how much the burning hairspray expands, and therefore how big the combustion chamber would have to be, etc.

Keep in mind that 100 m/s is a pretty good fraction of the speed that most bullets have when leaving the barrel of a gun -- be careful with this device, no matter how you choose to build it.

- Warren
Thank you chroot. Helpful like always.

Regarding the energy source, would you mind giving me some examples of energy sources which i could experiment/research on? From what i have found, the general energy sources used for these potatoe cannons (even though i don't plan on shooting big projectiles such as potatoes) are compressed air and combustion (like you mentioned). Question: how would i go about building air pressure in a tank? I understand i must use a compressor, although i would assume practical compressors are too weak.
Also a question: what PSI do paintball guns exert on the shots? What speeds do these paintballs reach and approximately of what mass are they?
 
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