My first piston powered pneumatic tater gun

[tvouthilak]

Hey all. New to the forum. I built my first combustion 'tato launcher about 5 years ago and thought it was time to step it up to the next level.

Been looking through a lot of the threads and there are some very nice spud guns people are making out there. Great job to all!!

I started researching pneumatics about a week ago and really had no idea how to go about it. When I made my combustion gun 5 years ago, I just thought pneumatics were too complicated and expensive to build. And at that time, I don't think people were using pistons and sprinkler valves. I do remember reading something about using washing machine water valves but seems those are not the popular thing anymore?

Anyway, on to my creation.

Air chamber is 2" pvc
Barrel is 1" pvc- Barrel is detachable and I plan to make a .5" and 2" barrel for it as well.
2" Piston casted from hot glue
1" sprinkler valve for filling and firing- filled using tire valve and fired with stock solenoid

Only problem I'm facing is with filling the gun with the tire valve. The issue is that when unclamping the pump from the valve, if I don't do it quickly enough, air will discharge from the valve and the gun will fire. Only way I can think to resolve this issue is to either add a check valve(which I am finding very difficult to find) or a shut-off valve(ie. small ball valve) so that the air won't discharge when I'm disconnecting the pump.

I'm a total noob at this pneumatic stuff so please feel free to critique my design and offer comments or suggestions.

I've fired the gun at 80 psi and WOW it really packs a punch. Any suggestions on max psi this thing will handle?

The only thing I have left to do is attach a power source for the solenoid and a push button trigger.

Sorry for the dark pics(taken with my cell phone)

Enjoy!!

[Gippeto]

I like the design. The 1" sprinkler as a pilot is overkill on a 2" piston, but that's alright.

I suppose that your barrel threads on? This is good thinking.

If it is ALL NSF-PW stuff, I would suggest 120psi as a safe max.(it also happens to be what I use as a max on my pvc gun)

Nice job.

Welcome to Spudfiles.

[mark.f]

Nice job with the stock. As for the problems with the air source, I would just add a small ball valve.

[i-will]

the pics r fine. and the cannon looks great. that is a great first. looks awesome and will look better if u paint it. what do u use as ammo and what's the damage?

is that barrel screw-on cuz using friction alone is a bad idea.

also i think u should use that sprinkler valve for something else but if u like it then cool.

[cannon monkey]

as for ur pics great job
as for ur air problem move the valve dont put it on the valve
if that possibe i never use a piston so idk

[tvouthilak]

Thanks for the comments. I know I still have a lot to learn but I'm quite happy with my first attempt at pneumatic power.

As for the 1" sprinkler valve, yeah I realize it is overkill. When I started this project I had planned on building a bigger cannon with 3" piston and 4" chamber, but thought that was a bit much for my first. I also like the concept of an electric trigger, but I guess I could have done that with a 3/4" sprinkler valve as well.

yes, the barrel is thread on.

"as for ur air problem move the valve dont put it on the valve"

-Yeah, I was thinking of putting it on the back of the piston, but with the 1" adapter for the sprinkler valve on a 2" plug, there didn't seem to be any room for it.

I will most likely install a small ball valve like markfh mentioned.

"what do u use as ammo and what's the damage?"

-so far I've only used potatoes for testing purposes but have also used some 1" dowels cut to about 1" long. I've only really tested for distance so far so no real damage to report..

Keep the comments coming...

[experament-u2]

you have done some research that's a good sign

cannon looks good as, great job

[potatoflinger]

That looks great, especially for a first. I didn't notice any DWV, which is also a good thing.

[tvouthilak]

**UPDATE**

Just thought I'd keep people posted on my progress. Last time I posted, I still needed a power source and trigger mechanism. Seems like the common thing to use are 3-9v batteries and some sort of push button switch to activate the solenoid.

After working on an unrelated project, I came up with something that works pretty well. I took apart an old camera and discovered that the flash circuitry could be adapted to power my solenoid and the cool part is that it only runs off of 2 AA batteries.

Here's the concept:

Normally when you fire up a flash on a camera, a transformer charges up a Capacitor which stores necessary voltage(this one was 330V) to power the flash. Obviously, 330v is a bit much for the solenoid. So I removed the original capacitor and replaced it with a 35v one and now I have my power source. I added two micro switches to activate the power source. One is to fire up the transformer to charge the capacitor(that's the high pitch whine you hear on a camera when you push the flash button and the other is for the trigger. This sort of works as a safety because the gun won't fire unless you hit the charge button first. It only takes a few seconds for the capacitor to charge then you're ready to fire..

Another feature of this system is that the capacitor discharges in a very quick burst. What this means is that instead of keeping the solenoid open and expelling all my air, it opens and closes real quick so that I can actually get 2 shots out of my air chamber. If I fill the chamber to 80 psi, I can usually get another shot at about 50 psi before having to refill the air. Cool!!

[Demon]

Thanks for the comments. I know I still have a lot to learn but I'm quite happy with my first attempt at pneumatic power.

What? I bet you are happy, you made a fu#$%&* cool piston valve on you FIRST ATTEMPT!!!

My first attempt was a ballvalve!I only made a coaxial(same thing as a piston) 2 years after...

[tvouthilak]

Thanks for the comments. I know I still have a lot to learn but I'm quite happy with my first attempt at pneumatic power.

What? I bet you are happy, you made a fu#$%&* cool piston valve on you FIRST ATTEMPT!!!

Thanks for the kind words.
Yeah, I've been very satisfied with the cannon so far. However; after a week of use, it does seem to have developed a small leak. Either the piston is not sealing completely with the barrel any more or the piston itself is leaking(through the bolt in the center of it) No big deal, I can live with it if it doesn't get any worse.

My next step is to work on a pump action reload..

STAY TUNED...........

[tvouthilak]

**UPDATE**

Just a quick damage photo to share. I built a pretty crude indoor shooting trap to test out the gun. The trap is just a cardboard box with layers of paper inside and a board behind to stop any stray shots. So far at 100 psi, I have been able to shoot through about 100 sheets of paper(which is one row of papers) from 25 feet away. The ammo is a 1/2" marble.

The gun shoots pretty accurately from 25 ft. I was able to get within an 1" from where I was aiming after calibrating the scope. If you look closely at the yellow board, you can see a couple dents from when I missed the target while calibrating..

I was hoping to be able to shoot through more pieces of paper at 100 psi, but I think since the papers are just loosely sitting in the slots, they are able to flex and absorb the energy of the marble. I'm pretty happy with the test results though..

I'm currently working an a revised version of this cannon, so stay tuned for further updates...................

[woden the awsome]

That thing is pretty cool! I like how compact it is, but you don't need a capacitor and transformer, all you need is 3 nine volt batteries.

[Brian the brain]

He knows that.He just found another way of doing it with less battery power.
I , for one, think it's cool.

The 1" valve, when modded, would definitely be overkill.
Considering you want to keep it the way it is, it's better to have it that big.

Now build a remote control for the valve and you can make spudding history!

So...all in all, a great build.

[tvouthilak]

That thing is pretty cool! I like how compact it is, but you don't need a capacitor and transformer, all you need is 3 nine volt batteries.

Thanks for the compliment. Yeah, my main objective for this cannon was to make it small and compact without sacrificing performance and ergonomics. With it shaped like a rifle, it is very comfortable and easy to handle and operate. and yes, 3 9-volts would have been the easy thing to do, but I was looking for something more unique and that used less battery voltage.