SpudFiles

This project is long overdue, but better late than never. This is my first potato gun so I'm going to need lots of input from you guys.

I need to play with barrel length, chamber size, various pressures, etc to get as much range out of this thing since I want to develop a cannon to launch a shark bait around 250 - 300 yards into the ocean...

I went shopping this morning and I nearly have everything I need (I just need a section of 90mm pipe to complete the chamber).

The plan is to start with a 40" chamber which will fit perfectly with a 47" off-cut piece I already have for the barrel. All components are rated higher than 150psi so from a safety point it seems alright to operate at aound 100psi, right? From there I will start changing it up and spreadsheet everything as I go...

The above config is more compact, but I just realized I'm creating some dead space around the elbows after the valve.

The following config will deal with that, but make the entire gun 8 inches longer...

ok so I managed to get some pipe for the tank, but they were out of stock on 90mm pipe so I upgraded to a 110mm tank.

I looked around for good quality tire valves, but couldn't find bolt in ones anywhere. I guess I'm just going to make a cheapy work...

This is what I came up with, don't know if it's gonna hold :/

Looks good so far. If your tire valve feels a little loose or anything, don't worry. Under pressure they generally seal up well because the air in the chamber tries to push the valve out of the pipe.

Looking good, with a chamber that size it's going to have one heck of a "whoomph" but it will take a bit of time to fill.

Yup, BIG tank!

Doing the PVC glue tonight, pressure test tomorrow

This makes me think is shoud build one to! Looks graet if you can post a video with a test shot! Would love to know allso what is the DB that this thing makes! If you dont have a db meeter use a android system and download a DB reader

Assembly complete. Pressure testing tomorrow night. Hopefully fire my first slug out of my first gun this weekend...

Here's a closeup of the valve and some of the hardware. I forgot to unscrew the constrictive tip from the blower nozzle before taking the photo, but you get the idea. I just hope that valve still works, I gave it quite a bit of hard loving!

B.T.W. Will those screw threads seal tight enough or do I have to glue them as well...?

Here's a closeup of the valve cover mod.

I sealed the little tube that the solenoid used to seal on using 2 part epoxy (but it wasn't worth a pic).

I did the pressure tests tonight and I realized how scared I am of this thing!

At first the gun didn't want to hold more than 45psi due the the leaky screw threads. This was enough pressure to test the modified valve and once I confirmed that it worked I mixed some epoxy and glued the screw threads on.

Decided to set up a barrier for the full pressure test. Gun on the one side, gauge and myself on the other. pumped it to 90psi and waited 5 minutes... perfectly tight, no leaks. Mustered up some courage to reach in behind the board and pull the trigger... Loud PSHHHH! and the gun recoils a bit and slides about 5 inches on the concrete while I'm holding on to it.

Charged it again to 100psi, no damage. Fire again, this time knowing what to expect. Pumped it again to around 40psi just to make sure there's no damage and to do a fire from the hip. I felt a bit like Arnold in Terminator when that icy cloud fired out the front!

Need to do the final touches tomorrow and then it's ready for a live ammo over the weekend!

Well, where's the photos of fridges full of holes?

Bit of target practice this afternoon with my new toy...

Very nice looking! Quite solid too
Assuming you have Sch40 or Sch80 PVC then I believe that your max pressure should be about 150 PSI (with the sprinkler valve), you can safely take it to about 100-120PSI.

~NooooooB~ wrote:Very nice looking! Quite solid too
Assuming you have Sch40 or Sch80 PVC then I believe that your max pressure should be about 150 PSI (with the sprinkler valve), you can safely take it to about 100-120PSI.

Here in South Africa we use Bar for pressure (1Bar ~ 15psi)

My chamber uses Class 12 PVC which means it's rated for 12 Bar (~180psi). My Sprinkler Valve is rated for 8 Bar continuous use (~120psi) and I'm not really planning on using it over 7 Bar (100psi), just to be on the safe side...

I shot a spuddy around 250 yards into some strong head winds. We're busy making plans to get fishing baits out that far...