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My Second Generation Piston Valve cannon

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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My Second Generation Piston Valve cannon

Unread postAuthor: Mr.Gadget » Sat May 08, 2010 4:53 pm

Hello Every one.
I love this web site. So much to learn, So many good designs!!!
Well, I put my little brain to work and ended up with my first cannon. It was made to be mounted on a TANK (Gocart with plywood) and I did not take a picture before one of the guys bought it off of me.
So with cash in hand I ran down to the hardware store to resupply with materials. Guess what, I ended up with a cannon that is just amazing!!! Even thought I can not call it my first any more, it is still the same underlying design, with some new mods, and better configuration. And the cannon is semi-auto, yes it recocks, and repressurizes it's self. My next one will have breach loading barrel.

I added in a double safety. The first is that the trigger cannont be hit by a bush, or stick, or twigg, or clothing, because it is inside the handle. The sencond is a sliding mechanical lock, so when it is sitting on a table at the field, you can easily see it is safetied.

At 40psi, 3 litters of air, I get 175 yards of TANK busting, Nerf launching power!!! I love this cannon!!! and all the info was learned here, with a little added creativity.

I hope it inspires someone. Have fun, and be safe.
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Cannon 2.jpg
One beauty of a cannon!!!
Cannon close up.jpg
Sliding safety white so you can see it

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Unread postAuthor: clemsonguy1125 » Sat May 08, 2010 4:56 pm

Looks good, you really should replace the soda bottle though
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Unread postAuthor: geardog32 » Sat May 08, 2010 5:10 pm

wow i must say i really like it it has a very clean cool look to it. awesome job.
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Unread postAuthor: Mr.Gadget » Sat May 08, 2010 5:24 pm

Ah yes, The soda bottle.
That seems to be the first thing people coment on. I have been using these soda bottles for several years on burst disk designs. The bottles are rated at 125psi specificaly for shipping and rough handeling of carbinated beverages by the manufacture. The soda bottle gets a good wrap of black duct tape (not it this picture) to help prevent sticks, twiggs and such type damage.
Under testing with this launcher, The bottle has taken a close range (15 foot) direct nerf hit to the bottle with 80 psi inside. And a drop from 3.5 feet with the same presure. With the duct tape wrap, I have stabed the bottle with a knife on a stick. It did not explode, but relesed all of the pressure rapidly.
I run this cannon at 40psi, and some times 60psi. well with in the manufacturers rating.

When I want to run higher psi, I use pressure rated Sch40 PVC chambers. I will never run this bottle at higher psi,, and the bottle will get swaped out depending on usage.

I know there will be more soda bottle bashing here, and I'm ok with that, I will keep using it because it fitts my needs. But my needs are not to blow holes in things with high psi, I want lower pressure distance for nerf footballs, and light weight because I am a ground troop.

Thank you for your advice, and your thoughts of safety. For anyone that reads this, that is definatley something to keep in mind. Safety first!!!
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Unread postAuthor: Mr.Sandman » Sat May 08, 2010 5:32 pm

It seems my post didn't make it through before your update. Oh well it's still good to know that you are keeping safety in mind. People like you are what makes spudfiles great, you are new and don't take any offense to some constructive criticism and you use correct grammar and punctuation more so than my own. Right on man, right on.
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Unread postAuthor: maverik94 » Sat May 08, 2010 6:35 pm

you really should replace the soda bottle though

Agreed, but it seems like you are being conscientious about safety, which is good.
It seems my post didn't make it through before your update. Oh well it's still good to know that you are keeping safety in mind. People like you are what makes Spudfiles great, you are new and don't take any offense to some constructive criticism and you use correct grammar and punctuation more so than my own. Right on man, right on.

Ditto, that's the way to get ahead and get respect on Spudfiles (that and building cool and innovative gun designs). Anyway, is there any way you can post drawings or photos of the internals of this gun to show how you set up the semi-auto design? Anyway, nice design, and a very clean build...minus the soda bottle.
The bottles are rated at 125psi specifically for shipping and rough handling of carbonated beverages by the manufacture.

I've seen many people arguing about how tough soda bottles are, but I've never seen a clear, official pressure rating like this. Where did you find this out?[/quote]
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Unread postAuthor: Technician1002 » Sat May 08, 2010 6:40 pm

Soda bottles are OK for low pressure cannons, but I prefer higher flow and thus something with a larger opening.
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Unread postAuthor: Mr.Gadget » Sat May 08, 2010 7:14 pm

I respect the caution many of you have about the soda bottle. I will not argue there are more capable stylea of chamers out there. But not at this weight.

I am not here to argue the soda bottle, but the information can be found if you know what to look for. In short, the soda bottles sit on the shelf at and average of 45 thru 55 psi ready for sale. Now the bottle has to be handled to the counter, droped, kicked,, you know kids and thier acidents. Now for the extream, The bottle has to withstand the internal temperatures of an unattended vehicle. Your nice cool beverage is unopened, and now very hot, but still intact. Internal pressure of around 100psi. Drop it now,,,and it still stays intact.

I use the 3 littler, and 1 litter bottles with the 1 and 1/4inch mouth opening for fast air release. Believe me, it gives Amazing performance, which is why I have used the big mouth bottles for bust disk designs for a long time.

Here is a long read, but more information than I ever knew about PET soda bottles. THere are even newer articals than this available. And can be found using Google and "PET soda bottle pressure tests."

http://webarchive.nationalarchives.gov. ... e21474.pdf

Now for the internals. It's your standard piston valve, Semi auto was just an after thought during the build. I am a long time paintballer, and it you notice, the cannon resembles a paintball gun. Run a line from my fill location, to the back of the pilot (sprikler valve) and the piston resets, then the tank refills.
The only problem I have had with the design, is when the system starts at zero psi, and the valve open. Air just runs though it out the barrel. To start the cycle, I use the palm of my hand, plug the end of the barrel untill I feel pressure and release. The valve seats, and its semi-auto from there on out. The lowest operating pressure the launcher fires effectively is 20psi. And that little Nerf ball still goes flying!!!!
Hope that helped.
I you would still like, I will post pictures
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Unread postAuthor: clemsonguy1125 » Sat May 08, 2010 8:36 pm

Well yes soda bottles can handle pressure but I they get hit multiple times the will blowup, I used to fill soda bottle with baking soda and vineger, then throw them in the air, when they hit the ground they would shoot off like a rocket, this would work because either the cap would crack and blow off, or the bottom would crack, you dont have the problem with the cap, But I would renforce the bottom of the bottle somehow
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Unread postAuthor: Mr.Gadget » Sat May 08, 2010 9:28 pm

Lieutenant Colonel clemsonguy1125,
I do, I really respect all concerns of the soda bottle. I have done my research, and extensive testing over the years, and accept any risks for what I have chosen as my air tank. I will start a new thread and specificaly attack the soda bottle air tank, and see what I can do, or what it takes for a real life catistrophic failure. Safety first, and fully documented. That acctually sounds like a fun and informative adventure. Lets look at the other portions of the launcher for a while.

Not many launchers have incorperated safety locks, or the mounting of the trigger, or the semi-auto function, or just the amazing internal workings of what a pneumatic piston valve has done for the sport of spuding. I have looked for a long time to find the power of a burst disk, in a reusable setup------ Pneumatic piston valve has turned out to be my answer. I have everyone here to thank for my success. Thank you all.

If there were one queston I have for anyone,,, and because I am the newbe here, "What the heck are Spud Bux?" LOL I have 20 of them!!

Thanks guys and gals,,,, look at the launcher,,, not the tank please. I am using the most unpopular tank and I know it. But in what I consider a responsable maner, I never intend to TAKE IT TO THE MAX. I am launching Nerf footballs at PEOPLE.. Living ones.. and at the end of the day, I would like to see them still alive, because I call them my firends. And at at 220 foot per second exit velocity, and 175 yards at 40 psi,, I don't need to go any higher. I out shoot all the unrgulated co2 cannons (800psi) on the field now any way, and hope people will follow suit.

OK the beers have got hold of me,, now I need to go clean up my mess in the garage before the Domestic Commander chews me a new one.
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Unread postAuthor: Gun Freak » Sat May 08, 2010 9:31 pm

Just so you know, you ain't supposed to talk about shooting people, or living things for that matter, with the exception of paintball and airsoft, on SpudFiles. SpudBux are for spending in the store on Signature and Title changes.
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Unread postAuthor: clemsonguy1125 » Sat May 08, 2010 9:34 pm

Mr.Gadget wrote:If there were one queston I have for anyone,,, and because I am the newbe here, "What the heck are Spud Bux?" LOL I have 20 of them!!
.

I dont mean to bug you, Im just giving my saftey concerns, you can buy signature privleges and title changes and stuff
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Unread postAuthor: maverik94 » Sat May 08, 2010 9:46 pm

Ok, fair enough, i see you have done your research on this one, and it looks like you're keeping safety in mind. If I understand your piston problem correctly, you should be able to remedy that sealing problem with a weak spring pushing your piston shut when the pressure is low. The only disadvantage that has is that is reduces the gun's performance a bit, but it seems you are using this gun as a casual, mid-power rifle. Not a high-powered cannon, so it shouldn't be a big problem for you. Anyway, It's good to see that someone new is actually researching things before posting :) Good work! I hope to see some new, cool, and innovative projects from you!!
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Unread postAuthor: clemsonguy1125 » Sat May 08, 2010 10:14 pm

Is that a sprinkler valve piloting your gun, I'm in the process of making a nerf vortex piston valve myself
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Unread postAuthor: Mr.Gadget » Sat May 08, 2010 10:16 pm

Thanks for the spring info, Yes I have thought of that as a solution,, and an easy, cheap one at that. But not a real concern, just a simple reset on start up.

Ok, I only shoot at people that are informed, PROTECTED, and willing participants, and shooting BACK at me. So I would consider that to be in the catagory of paintball/airsoft/scenario play.

All of you are really cool people, with even more stuff I can learn. Remember, this is only my second pneumatic piston cannon.

Lets take a short vote,,,,,,,,, Who wants me to SAFELY CAUSE A FAILURE on a soda bottle. I will be safe, with video, and guages and all the cool stuff. I'll do it, for other peoples benifit ...........SAFELY!!!!!

Oh one last thing,,,,, I will try not to be so long winded from now on. (thanks for that input)
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