Potato cannon bait launcher for fishing the beach

[MathGeek]

Originally Posted by swt70611

I've looked at few of those on YouTube but haven't seem what they are using as a trigger/release. What's your idea on that?

Also saw a homemade one made of PVC pipe. Not sure I like that idea.

The simplest release is a ball valve. We hope to use a 2" ball valve for simplicity, durability, and prevention of premature launches. I've seen designs with sprinkler valves and others also that provide faster initiation of air flow, but there are bait launchers getting 1000 ft with ball valves, which is more than we're hoping for.

You can get PVC rated for 300 PSI. Combined with only filling a pneumatic design to a max of 100 PSI, there should not be a problem. We've used PVC in several combustion designs with a sharp pressure rise and we've never had a failure. We've also used metal. Metal tubes have a lot more friction in the barrel and less uniformity which increases gas blow-by. IMHO, better to use properly rated PVC and keep pressures < 100 PSI.

[Fishbum]

Easily convert one of these into a potato cannon. Just build a barrel out of pvc sized to fit your needs. Beware, will almost shoot a spud into orbit. Will need a good supply of compressed air.

[swt70611]

The ball valve makes sense. Was curious if it opened fast enough. Sprinkler solenoid valves would work but have to deal with powering them.

Be careful not to let the PVC get dropped or beat up. We had a shop with PVC airlines. It was over 100psi by a little. Nevertheless had a fitting blow out. Scared the **** out of us.

I had aluminum tube in mind. Inside walls could be machined smooth and polished. Not cost effective as PVC though.

[MathGeek]

Originally Posted by swt70611

The ball valve makes sense. Was curious if it opened fast enough. Sprinkler solenoid valves would work but have to deal with powering them.

Be careful not to let the PVC get dropped or beat up. We had a shop with PVC airlines. It was over 100psi by a little. Nevertheless had a fitting blow out. Scared the **** out of us.

I had aluminum tube in mind. Inside walls could be machined smooth and polished. Not cost effective as PVC though.

Machined aluminum would be cool and likely function very well. I had not thought of it because it is expensive to make a 4-6 ft long machined hole. I was thinking more of hardware store steel pipe.

[swt70611]

Originally Posted by MathGeek

Machined aluminum would be cool and likely function very well. I had not thought of it because it is expensive to make a 4-6 ft long machined hole. I was thinking more of hardware store steel pipe.

I have access to tubing. Interior walls are better than pipe and could be smoothed with a hone. What's the magic length?

[MathGeek]

Originally Posted by swt70611

I have access to tubing. Interior walls are better than pipe and could be smoothed with a hone. What's the magic length?

I wish I knew more about optimal lengths. We like 4 ft for our combustion designs, but this is our first pneumatic. Most pneumatic designs have 4-6 ft barrels with reservoir volumes ~2 times the volume of the barrel.

If your reservoir volume is the same as your barrel volume, you only have half the original pressure pushing the projectile at the end of the barrel. If your reservoir volume is twice your barrel volume, you have 67% of the original pressure pushing the projectile at the end of the barrel, assuming the ideal gas law applies. Barrel dwell time is 1/20 to 1/10 of a second, so you need to get the valve open and have enough gas move through quickly to maintain that kind of pressure behind the projectile.

[Goooh]

Originally Posted by MathGeek

I wish I knew more about optimal lengths. We like 4 ft for our combustion designs, but this is our first pneumatic. Most pneumatic designs have 4-6 ft barrels with reservoir volumes ~2 times the volume of the barrel.



If your reservoir volume is the same as your barrel volume, you only have half the original pressure pushing the projectile at the end of the barrel. If your reservoir volume is twice your barrel volume, you have 67% of the original pressure pushing the projectile at the end of the barrel, assuming the ideal gas law applies. Barrel dwell time is 1/20 to 1/10 of a second, so you need to get the valve open and have enough gas move through quickly to maintain that kind of pressure behind the projectile.

Could you scale performance paintball guns?

[AceArcher]

came across these while stumbling around the internet today... perhaps they can offer idea's / thoughts on your project.

powerline launch Montrose 4_10_2012 - YouTube

powerline launch Montrose 4_10_2012 - YouTube

http://powerlining.com/

it seems like that fire extinguisher setup the first guy is using is pretty simple.... but have no idea how he is doing it..

[pricecb]

This is good stuff.
Warden ever see you doing this? I bet ole boy scratch his head when you explain what you are doing launching frozen shaped cut mullet 600' with a potato gun.
Next you will need a special license, training course, back ground check and at least 2 good references.