SpudFiles

Is it possible to achieve mach+ from a pneumatic? If so what is the min chamber size and min barrel length/dia?

Thanks for any help or leads.

You need to worry about high pressure and fast valve.

This was my stab at it: http://www.spudfiles.com/forums/high-ve ... 10446.html

Velocity3x has reached supersonic velocities with a golf ball.

Here is one of my videos;

In the begin of the clip I shoot a pingpong-ball. I don't have any velocity figures, but due to the very loud bang I suspect it might have been supersonic. The movie doesn't show how loud it was, the ears of me and my classmates were ringing for a minute.

[youtube][/youtube]

You can purchase supersonic, pneumatic pellet rifles so yes, it can be done. I'm not saying its easy...

Labtecpower
Both the ping pong and steel projectile were impressive shots!

@Temple
There is no specific chamber/ barrel size to reach mach speed. First you have to decide what projectile you'll be using (weight and diameter) and design the cannon around it. After you settle on a projectile, GGDT will help you design the gun.

[youtube][/youtube]
There is one shot in this video, where the sound was WAY louder, you can see my camera jump, from about 15ft away.

I dont know if this was supersonic, (kinda doubt it) but it was at least a plausibility.

This was done with 500+psi and a VERY fast ball valve. (spring loaded obviously.) To give you an idea, the handle on the 1/2'' ball valve ended up snapping in 2 from the opening force shortly after that video.

same cannon:
[youtube][/youtube]

The guy I worked with in building the competition T shirt launcher was already building competition marshmallow launchers and would chronograph his results. With a light projectile, large fast valve, and lightweight projectile, marshmallows do go transonic to supersonic. Pressure needs to be above ~90 PSI with a good valve to do it. Higher pressure is required for higher mass projectiles. One of my HS videos when viewed frame by frame is showing some supersonic particles from a broken apple launch that traveled almost 1.5 feet in 1ms. The bulk of the apple was about 2/3 that speed.

Moonbogg, supersonic air rifles use adibatic heating to allow such velocities. Generally the outrageous claims for springer velocities are made by Gamo, to prove a point they killed a rather large pig with one of their products.

They use a light pellet to achive pointlessly high speeds too, it's lighter, but they don't say that.

Helium fills do well, but I don't have any numbers for that.

[/rant about Gamo and their stupidity]

Zeus wrote:Moonbogg, supersonic air rifles use adibatic heating to allow such velocities. Generally the outrageous claims for springer velocities are made by Gamo, to prove a point they killed a rather large pig with one of their products.

They use a light pellet to achive pointlessly high speeds too, it's lighter, but they don't say that.

True, but there are a number of commercially available pneumatics that can edge over the speed of sound using high pressure and oversized or efficient inline valves.

I've suspected a few marshmallows were launched in that range, but I have not had a chance to clock it yet. The other projectiles I need to clock is the sabot loaded AA battery and empty pop cans. The impact damage is the same as in the video above.

When I'm not too busy, Knowing the speeds I get with apples, I suspect the lighter projectiles have higher speeds.

So High Pressure + Fast Valve + Light Projectile = Mach (maybe)

Temple wrote:So High Pressure + Fast Valve + Light Projectile = Mach (maybe)

Long barrel + High Pressure + Chamber big enough to avoid significant pressure drop until projectile leaves muzzle + Fast Valve + Light Projectile = Mach (probably)

Are you just interested in going supersonic for the heck of it or do you want to make a launcher that is portable/easily reloadable/ergonomic/compact/accurate?

The first is much easier to do, and can be done using off-the-shelf parts with silly dimensions.

I have a couple of launchers already. one is a rifle style launcher that shoots wood stakes, for when the vampires come. The other has a 4"X12" chamber with different barrels of various lengths for launching different projectiles. I mostly use 1" sprinkler valves because they are easy to find and cheap.

I'm just asking about super sonic to see if I can do it with what I already have on hand, as of right now it looks like my limiting factor is the valve, I don't think it will dump enough air fast enough to get a projo up to speed.

I do know my current launcher will sling a golf ball like crazy!

By sandwiching some frangible material in a PVC union you can easily make a burst disk valve, which is about as fast a valve as it gets.



Using this combined with a large chamber and long barrel, and perhaps a projectile in a lightweight sabot (say an airsoft BB in a 1/2" barrel), high pressure becomes less important.

I do know my current launcher will sling a golf ball like crazy!

This forum does have a showcase section