I'm going to build an air cannon tomorrow. ;)

I want to build a 1 1/2" version using the same design specified in the web pages at the link below. I just thought I'd pass this on to those of you that have fun putting a few natural laws together for a useless but joyful experience. One inherent problem with changing the design of this cannon very much is that the solenoid valve used is limited in its flow capacity. I thought about using two valves on a "T" fitting to double the available flow. You guys think that would be wise? BTW, at 50psi these things can launch a small potato 300 meters.

http://members.aol.com/sph911/spud/electronic.html

This potato launcher rocks, and it is infinitely safer than fuel driven rigs. I can pump it up to about 80 psi with a bicycle pump, and it'll launch a spud into orbit. Very worth the 40 bucks it cost to build.

What was the range..?

Urban warfare at its best:cool:


Your range should be enhanced by using the largest selenoid available to reduce throttling losses and decrease the pressure rise time in the projection tube.

300 meter distance, no problem. Pressure range is 50 to 90 psi. (the valve sets the limit, if you're being careful not to break things) I launched a few strait up, the hang time is ridiculous. I haven't timed it, but it is in excess of 12 seconds at ~70psi. The trick is getting fairly uniform spud slugs. I made a corer that cuts a slug to fit the barrel very neatly. The longer the spud, the less accurate. Slightly over square is very good.

Using a bigger valve might seem ideal, but the period of compression is more reliant upon the weight of the slug than the size of the valve, if the valve is adequate. If the valve can open fast enough to (very nearly) equalize the pressure in the compression chamber to the pressure in the barrel the valve is adequate. Using accelerants produces inconsistent results, inherent danger of explosion, and the risk of fire, because the fuel/air ratio is hard to balance in a static chamber. These pnuematic cannons produce very consistent results, and the performance is better than the scattered range of combustion models. You have to get lucky with a fuel based cannon to match the average performance of a well designed air compression cannon. The reason is because the solenoid valve opens almost instantaneously, and the combustion of most aerosol based fuels is gradual.

After firing the cannon at 70 psi, there is only about 5psi left in the compression chamber. This is a near perfect result. Going to a 1.5" valve would only enhance the performance a few percentage points, if and only if that valve opens as quickly as the .75" valve. Fun stuff.

Anyone have resouces or information on how to rifle a potato gun barrel?

What I was going to do, was take a very heavy grit sandpaper, wrap it around a stick with some insulative foam on it, and only make one half turn going into the barrel, and one half turn coming out the opposite direction. I was only going to groove about the last 18" of my barrel. After the course sandpaper, I would take some fine stuff to polish the hair off. You're only looking for a slight spin. This should do it.

Made a mortar once for the use of fire extinglisher cartridges. Had a cheap source for them at the time. The cartridges contain pressure stored at around 3000#. Good for about a mile and a half. Being as they are metal in construction, it is not exactly something you would want to aim at anything.

What kind of velocites do you get with the air cannon?

The Abrams uses a fin stabilized, discarding sabot(anyone know if the "T" is silent?)round for armor piercing work. A long dart is used, about two feet long and three inches wide. the sabot is a lightweight material used to fill out the round to the barrel diameter(120mm, about 4 1/2 or five inches). The gun will make about 3000 ft/s with this ammunition.
Using accelerants produces inconsistent results, inherent danger of explosion, and the risk of fire, because the fuel/air ratio is hard to balance in a static chamber. No one builds them right. I was thinking of taking a scientific approach to them, but this air cannon idea sounds better for the spud guns on the sides. The watermelon gun on top I'm not sure about.

You can by an air powered mortar from Tippman designed for launching paint grenades, they run off a 12 oz. co2 bottle.

hehe...3000ft/sec is outside the range of pvc altogether. I'm probably aproaching 400ft/sec with a PVC spudgun, but I'm limited to 90 psi or so.

Now, something I'm surprised we haven't seen yet is a sniper rifle that is air-powered. If you have, let me know. I'm talking about a military grade rifle that operates at about 500 psi. With sufficient volume/displacement capabilities, 3000ft sec is not an obstacle. Using a stabilized platinum uridium round, well, armor be damned. The other advantage to an air-powered sniper rifle, is that you can't see the report at night, and it is MUCH quieter. I want to make a prototype out of high grade steel, with a 6 foot long 1" dia. barrel. It should go through 6 inches of concrete using aluminum rounds. I'm designing a hand pump that should make 300 psi easily. But, high grade aluminum pipe and a very good pilot valve are necessary at these pressures.

I've seen some very impressive results from pressures as low as 120 psi. The speed of the valve is critical for good acceleration.

I'm designing a hand pump that should make 300 psi easily. But, high grade aluminum pipe and a very good pilot valve are necessary at these pressures. Get an air compresor if yoru serious about the stuff. If you look on painball sites, I'm sure you can find the ones used to fill the air tanks, which can get up to 4,000 psi, although th egun operates at much lower pressures.

My pump actually is part of the spud gun. It's piston design that uses and eccentric cam to drive it. I'll attach a wheel to the cam, and click-clickity-click, I'll have airpressure enough without batteries or other external stuff. I'm also going to modify the solenoid valve to operate pnuematically, so there's no need for electricity at all.

Originally posted by Gifted

The Abrams uses a fin stabilized, discarding sabot(anyone know if the "T" is silent?)round for armor piercing work. A long dart is used, about two feet long and three inches wide. the sabot is a lightweight material used to fill out the round to the barrel diameter(120mm, about 4 1/2 or five inches). The gun will make about 3000 ft/s with this ammunition.


I do believe he is speaking about the M1 Abrams Tank. The US's main battle tank that kicks major ass.

My pump actually is part of the spud gun. It's piston design that uses and eccentric cam to drive it. I'll attach a wheel to the cam, and click-clickity-click, I'll have airpressure enough without batteries or other external stuff. Those tanks would most likely supply enough air for several dozen firings on one charge. You might find the regulators and other equipment used for paintball useful.

No one has a comment on my watermelon gun?

I don't see a post about your watermelon gun. The Abrams?

No one builds them right. I was thinking of taking a scientific approach to them, but this air cannon idea sounds better for the spud guns on the sides. The watermelon gun on top I'm not sure about. It wasn't an seperate post.

Orbie has it right, although the British Challenger has the same size gun.

A short video clip of the spud cannon shooting a soft tater at a 2-liter bottle of water is available for the asking. I'll PM you a link if you want. There's a few Newtons of energy there.

(I've done nothing to enhance the solenoid valve yet.)