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by jimmy101
Thu Jun 04, 2020 10:29 pm
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Re: Calculations related to pneumatic cannon.

The teacher isn't a "professor", it is a high school teacher so expertise in this area is probably limited. :) Mark.f gave a reasonable answer. Don't need much of a "computer", you can do it an Excel spread sheet. Wont be super accurate but were talking a high school project, not a DARPA project. Ju...
by Moonbogg
Tue Jun 02, 2020 6:28 pm
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Re: Calculations related to pneumatic cannon.

It seems that Bernoulli's equation is typically used with incompressible fluids such as water, or gases where a constant density can be maintained which allows Bernoulli's equation to remain valid and useful. How can Bernoulli's equation be useful for a compressed air system where the potential ener...
by D_Hall
Sun Jul 26, 2020 1:30 am
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Re: Calculations related to pneumatic cannon.

Probably the quickest/easiest hand calcs you can do for potato gun prediction.... EndPressure = StartPressure * ChamberVolume / (ChamberVolume + BarrelVolume) MuzzleEnergy = (StartPressure + EndPressure) / 2 * BarrelLength * PI/4 * BarrelBoreDiameter^2 MuzzleVelocity = sqrt (2 * MuzzleEnergy / Proje...
by kunkmiester
Tue Jul 21, 2020 7:53 am
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Re: Calculations related to pneumatic cannon.

I was a little off. I was looking more at the combined law, as here:
https://en.wikipedia.org/wiki/Ideal_gas_law

My vague memories of chemistry had them the same.
by Doc j
Fri Jul 17, 2020 12:30 am
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Re: Calculations related to pneumatic cannon.

Maybe Just do a vacuum cannon.
Be simplest.
Plunger, Aluminium foil for burst disk.
Use a ping pong ball or tennis ball.
Be more in the "high school" theme.
Safer for demonstration.
Just my two bobs.
by jimmy101
Wed Jul 15, 2020 6:40 pm
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Re: Calculations related to pneumatic cannon.

The ideal gas law is not usable in the situation of a pneumatic spud gun. Three state variables (pressure, volume and temperature)n al change. You need to do more complex stuff, like take in to account the heat capacity of the air. There are very nice tools for both pneumatics and combustion guns de...
by kunkmiester
Tue Jul 14, 2020 12:59 pm
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Re: Calculations related to pneumatic cannon.

The ideal gas law is probably more relevant to this, as it considers changes in pressure, volume, and temperature, all of which happen. You'll probably have to do it the same way I'm looking at when I someday get to more complicated projects--you measure your velocity, calculate your pressures and v...