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Supersonic crack or what?

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Unread postAuthor: MountainousDew » Tue Apr 28, 2009 4:31 pm

Nerd War!
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Unread postAuthor: Ragnarok » Tue Apr 28, 2009 7:23 pm

Trust me, you don't want to see a nerd war. They're not pretty things, and usually end in at least one moderator having to be sectioned.
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: Technician1002 » Tue Apr 28, 2009 11:37 pm

Ragnarok wrote:
Biopyro wrote:Think of it as, the ammo usually absorbs the energy, but without it, all that goes into sound.

Not really "all of it" - sound is mercifully low amounts of energy.

Bear in mind, although a speaker might be labelled as 10 watts, only around 1% of that actually becomes sound energy. Most is lost to magnetic fields and heating. The sound output of most things is usually similarly low percentages.

However, more energy is available to become sound.

Conversion of electrical energy to sound is often inefficient as dealing with resonance of the mechanical and air masses require a high degree of damping. A tuned resonator can be very efficient. An example is a pizo horn. Very loud, low power and little wasted energy as heat. Bandwidth is very limited. Tuned antennas have the same drawbacks. Broadband, low gain. Narrow resonant band, high gain.

Back to the cannon energy.. A good portion of the energy in a near speed of sound launch is given to the air mass accelerated to near the speed of sound or in the middle of the moving collum, the center of the flow can even exceed the slower moving front as the front expands. This air contains lots of energy and is where much of the energy is expended.

A slower efficient power transfer can transfer most of the energy to the projectile so less is lost in the resulting muzzle blast. I played with that trying to make a silent launcher.

Results have been posted before, but for those who haven't listened to the efficient launch, it is here;

The tank being very small for the barrel contains little energy and the transfer to the tennis ball was very efficient. For the small volume, I got good hang time and a near silent launch.

To show the energy in the mass of air ejected from a typical air cannon, this video also previously posted shows the moving mass energy. This is not all just sound. It is a mass in motion containing kinetic energy.

Nerd War!

Maybe, or possibly a technical discussion. You decide what it means to you. :D Some here just want to blast holes in stuff and others are nerds who look at how to do it with more power. :D The fine details of what impact tweaks contribute to this goal is the nerd war.. And yes guilty as charged. :shock:
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