SpudFiles

This is my first attempt at a spud gun, and while I have yet to launch a potato, I am thoroughly pleased with the results. A lot of credit goes out to this community for providing the wealth of knowledge for me to base my first designs on! Well... here it is: Resovoir is 4”x 28”, and the barrel is... about 36” of thinner 1.5”. Its all solid PVC and rated above 200psi, though I only reach 145psi with my compressor. I have other barrels that screw on after the valve body; 2” for small tennis balls (small dog balls), 2.5” for large tennis balls, 1/2” for nerf dart (loose fit), and I’m working on one that shoots cheese puffs!(about 1” pipe). Each barrel uses a 2” threaded fitting. The valve (I believe) is a diaphragm QEV that came from a magnesium die factory... not sure what it came off of though, it was gifted to me long after it left the factory. It uses a secondary diaphragm to release the air behind the main diaphragm. It is lightning fast and sounds like a gunshot more than an air cannon. The trigger is an old air hammer that I pilfered for the crisp trigger and high flow rate.

Don’t mind the mess in the garage, just got through spring cleaning... in the fall... and well... the extra stuff goes to the garage untill I find a better place for it.
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Very nice for a first attempt!

Jamzearljones wrote:small dog balls

That sounds a little cruel...

Seriously though, that valve is a beast, good find. The trigger is a little... special, but hey, it works!

A word of caution when firing heavier projectiles, the PVC Tee fitting becomes the weak point and it is much better to hold it from the barrel to avoid it trying to rotate around the fitting due to recoil.

jackssmirkingrevenge wrote:Very nice for a first attempt!

A word of caution when firing heavier projectiles, the PVC Tee fitting becomes the weak point and it is much better to hold it from the barrel to avoid it trying to rotate around the fitting due to recoil.

I do fire it with one hand under the barrel. What I think you’re suggesting though, is moving my air hammer handle to another position? I’m not particularly thrilled with the way it feels in the hand as of now, so I would be open to that. I was looking for more of a “minigun” feel but the vertical handle puts me behind the thing instead of above it. I’m puzzled on how else to attach it, any suggestions are welcome, and a rebuild is not out of the question. I had to buy 10’ of the 4” tube so I’ve got plenty of extra.

Brace the barrel and chamber together

Here’s a couple of videos

Vertical launch test:
Testing the time in flight to determine theoretical velocity and maximum height. Projectile was a golf ball fired from a 1-½ PVC barrel with a chamber pressure of approximately 145psig.

Results are; Time: 18.45 seconds, Horizontal Distance: 325 feet
Calculated results; Launch Velocity: 297.33 feet/sec, Launch Angle: 86.60°, Max Height: 1,369.016 feet.

These results are theoretical and include some degree of error. Due to wind resistance, I do not believe the golf ball reached the Launch Velocity upon landing. The ball also impacted small branches from a 150 foot tree canopy (direction of travel was not visibly affected but the impact was heard). Wind aloft May have affected horizontal travel. Ball spin was not controlled and may have affected all variables (I do not plan on producing calculations to that degree of accuracy)

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And here’s me showing off to the neighbors.
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farcticox1 wrote:Brace the barrel and chamber together

How about this? I don’t like how far away the barel is from the chamber and not sure about huge braces, so I was thinking about bringing the barrel down to the chamber.

And here’s me showing off to the neighbors.

Sweet, dog seemed to enjoy it too

How about this? I don’t like how far away the barrel is from the chamber and not sure about huge braces, so I was thinking about bringing the barrel down to the chamber.

Looks good to me, that way you could have an arm under the chamber without stressing the elbow fitting.

So here it is. The almost straight from the legal pad golfball cannon MK III. There was a MK I before all of this that... well let’s just pretend that never happened.

I realized that the exhaust port on the QEV could use a ball valve as a safety of sorts. When the trigger releases the pressure off of the back of the QEV, the diaphragm tries to exhaust out the side. With the “safety” ball valve closed, nothing happens except for a quick puff (and small hiss) out of the trigger... NO shot fired. Tested and works at all pressures, just a little peace of mind. I also machined the air hammer handle into a nicer trigger setup. I use the term machined loosely as all I have to use at the moment is a drill press and an X-Y slide vice. The air flow through the handle is still impressive, even though the flow/volume required to actuate the valve is minuscule. Final addition was a pressure gauge on the back of the QEV. I relocated the fill plug for the resovoir to the front of the chamber but I don’t really like how that looks. I’d like to put it somewhere else, but I’m not sure where it would work out (suggestions?).

I realize the barrel is not attached to the chamber yet, I forgot to pick up the pipe clamps when I was at the store.

I have 3 working barrels, same as before; 2” small tennis ball (small dog balls ), 1-½” golfball (with Backspin “break”), and a ½” nerf dart barrel. The nerf dart barrel also shoots foam ear plugs quite well.

That looks great. How do you get your small dog's balls in there without the legs getting in the way?

I relocated the fill plug for the resovoir to the front of the chamber but I don’t really like how that looks. I’d like to put it somewhere else, but I’m not sure where it would work out (suggestions?)

About the only place it's going to be safe if you keep it on the chamber "as is", is on an end cap, so either where it is (at the business end of the barrel, even with safety...) or at the other end of the chamber.

My understanding, perhaps wrong, was that it's easier to charge through the pilot valve.

mrfoo wrote:My understanding, perhaps wrong, was that it's easier to charge through the pilot valve.

I’m not sure if I am able to charge through my pilot valve since it is a two diaphragm valve. I do know that I cannot charge through the “exhaust” port, but my interest now is to see if the pilot valve is usable as a fill point. That would be fantastic :bounce: I really don’t like the way the fill looks up front.

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Jamzearljones wrote:There was a MK I before all of this that... well let’s just pretend that never happened.

We won't judge, you're among friends here

Looking good, once you have the barrel strapped to the chamber it should be able to handle heavier projectiles with ease.

jackssmirkingrevenge wrote:

Jamzearljones wrote:There was a MK I before all of this that... well let’s just pretend that never happened.

We won't judge, you're among friends here

It was a 1” sprinkler valve that I modded to actuate pneumatically. Still didn’t get a crisp enough release to satisfy my inner demons. And I guess... before that was a horribly failed attempt at a piston valve, it didn’t work and I didn’t make the piston accessible, so I abandoned that and went with the sprinkler. Call that MK-0.

jackssmirkingrevenge wrote:Looking good, once you have the barrel strapped to the chamber it should be able to handle heavier projectiles with ease.

Yeah... about that... I got a little too eager and needed to try it out. Hardware stores were closed on Sunday so I had no choice but to just go for it. I took a slowmo video to watch what the barrel would actually do... let’s just say I only shot it like that once.

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I got a little too eager and needed to try it out.

Standard Spudfiles Attitude

let’s just say I only shot it like that once.

Nothing better than a visual demonstration, it will serve as a good manner of illustrating the importance of barrel support of future builders.

jackssmirkingrevenge wrote:Nothing better than a visual demonstration, it will serve as a good manner of illustrating the importance of barrel support of future builders.

Without straps
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Closeup without straps
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WITH straps
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Closeup With straps
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