I want to calculate the velocity in m/s of all these spud gun projects i see on the internet.?

Question

can someone suggest a formula? where the variables are
v= velocity in m/s (what we want to know)
D=internal diamter of pressure vessel (mms)
L = length of pressure vessel
d= internal diameter of barrell (also i.d of valve leading to pressure vessel)
l = length of barrell
M = mass of projectile in grammes
P = pressure of pressure vessel in psi (which i will covert to bar....anyway know how to convert bar to pascals?)
T = time valve is open in seconds
the spud gun will consist of a pressure vessel storing compressed air, with a valve in front of it leading to the barrel. when the valve is opened air will be released pushing a projectile out the barrell
couls soem one build me an equation to calculate the velocity of the projectile using these variables? i see all these spud gun sites on the net and id love to know how fast they go...
also whats the speed of sound?

Answer 1

Here's the best site I have found for calculating the velocity of the spud:
http://ffden-2.phys.uaf.edu/211.fall2000.web.projects/J.%20Jones%20and%20T.%20Kenny/Projectile.htm

This is for a combustible firing chamber. The pneumatic guns are more predictable and reliable since the pressure can be set prior to firing. Where the combustible require calculating the air to fuel mixture based on the size of the firing chamber. This is explained on another part of the site referenced above.

The best choice for this type of gun seems to the the solenoid valves that are common on sprinkler systems.

They also recommend that the barrel resistance be measured using a simple fish scale to find the force of resistance of the spud against the barrel.

I also looked at a rifled barrel that provides better accuracy.

Most spud gunners use parametric measurements to find the range of their cannon. This is done using inclimeters for altitude and pressure gages to measure the max pressure in the firing chamber, while increasing the amount of fuel or air pressure and taking a series of measurements to find the characteristics of the cannon.

enjoy

j

Answer 2

Hah. i recognize those. Now people make potato cannons and use hairspray as a propellant! regrettably, some places I have considered make those interesting instruments unlawful because they could be "risky" ...anybody who can pull off a monetary employer heist with a potato gun/cannon benefits all the money they could carry lol.