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Building a cannon for work!

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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Building a cannon for work!

Unread postAuthor: ryanzander » Sat Aug 24, 2013 1:10 pm

Hey guys, newbie here.I have built oxygen-acetylene launchers before, but never pneumatic. Heres a an overlay of what I get to do. We've built a giant pinball machine for at a tradeshow. We need to build a launcher to fire a baseball to the top of the board. It is 14' tall at the top.

GOALS:
Our products are pvc free, so this shouldnt incorporate alot of it.
Safety: Lets not hurt anyone.
Consistency: It must fire 19/20 times
Range: Fire the baseball in a consistent trajectory 8-10'

Will be mounted on a single plane pivoting mount.

Compressor: will be mounted to back of this board, so it must be able to keep the cannon/reservoir filled, but still remain quiet. Preferably not needing a power supply more than a regular 110V outlet.

We also need to have a way to adjust the pressure to the cannon, with the air compressor shutting off at that psi.

Budget: Have to keep it low. Granted the company is paying for this, but it isn't endless.


MATERIALS READILY AVAILABLE:
We construct our products from galvanized steel and mid grade aluminum. O.D round sizes are as follows in steel: 0.815" 1.029", 1.315", 1.66", 1.99", 3.5", 4", 5"
These range from 7-14 ga.
In aluminum i have 1.315", 3.5", 5" these are 10-13 ga

I also have selections of flat stock, angle and square in both aluminum and steel

Our maintenance department has all kinds of plumbing stuff, and ball valves ranging from 3/4" to 2.5"

I have the ability to weld all of the materials we have on hand.

Im not worried about you guys freaking out about the burst strength of the materials, way i see it, we shouldnt need much more than what, 120 psi as long as we're moving a decent volume of air, right? anybody have starter suggestions of how much barrel to tank ratios?

I guess the biggest obstacles i have are, how do i get to limit the pressure and monitor it? And the compressor itself.

I promise to take lots of pics through the building process.
Also i know a baseball is a horrible ammunition choice, but i didnt choose it, this came from the bosses here because its play oriented. I may be able to switch ammo, open to suggestions but its got to be a decent weight to go through the pinball obstacles and cannot be bouncy. And be easily recognizable and relatable to play and childhood.

Any help and suggestions is greatly appreciated!
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Last edited by ryanzander on Sat Aug 24, 2013 3:02 pm, edited 1 time in total.

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Unread postAuthor: Gun Freak » Sat Aug 24, 2013 1:56 pm

ball valves


This task requires major consistency, which ball valves cannot offer. I would suggest a modified sprinkler valve for your main valve. This will give you consistency between shots and good enough power. Get one in 1" size.

For a chamber aluminum or steel tubing would just be overkill... PVC is the easiest option especially considering you're only going to need 100 psi max. But if you're hell bent on avoiding PVC, a welded metal chamber would be perfectly fine. And since you're capable, go for it. The chamber won't necessarily have to be very big since you're launching a very short distance... But I would estimate a good chamber size to be around 2 feet of 3 or 4 inch pipe.

Barrel will only need to be a few feet long.

You have a couple of options for a compressor... 12v compressors are quiet but won't fill up a big tank very quickly... Fridge compressors are almost silent but are way too low volume... Basically any compressor that will do the job quickly is going to be loud. Why not use a manual pump?

Why even make an air cannon for this simple task anyway?
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Unread postAuthor: ryanzander » Sat Aug 24, 2013 3:18 pm

Thanks! I will have to do a search on here to learn about the sprinkler valves. Im aware a metal chamber and barrel is complete overkill. But since our product comes into contact with kids on a daily basis, pvc has been eliminated and replaced with other options.
I have been thinking about building an insulated box to put the compressor in and adding a muffler to try to keep the noise down. A manual pump isnt exactly optimal due to the fact this thing needs to be launched once about every 30 seconds.
Originally our design called for the ball to get shot through a tube with a 90 degree bend in it, then after the 90 it would have to travel up to 6'. Did i mention this thing is darn near vertical? This was a rather hard task as the baseball causes alot of friciton, even in a 5' tube. We had tried multiple launching methods, slingshots at the base of tubes, spring powered, using both extension and compression springs, the problem with these methods are, we cannot have the potential people at the tradeshow have to exert more than 30 lbs of force, and it has to be consistent. Spring powered took too much energy and the slingshot method was not consistent.
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Unread postAuthor: Gun Freak » Sat Aug 24, 2013 3:31 pm

How many times is the cannon going to be fired in one session? You may be able to get away with pre-filling a big tank (~10 gallon) and filling your gun with that.

Or... :twisted: Since this is company-funded, buy a Scuba tank and regulator and use that to fill it :D
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Unread postAuthor: ryanzander » Sat Aug 24, 2013 4:17 pm

I cant give you an exact number, but theres going to be a TON of people there, each person will get approximately five shots, a pre filled tank probably wont work, i dont know what im going to run for a compressor, even a small pancake compressor may be too loud. Hopefully i can find something that can fill the volume of air that i need quickly and relatively quietly. Unfortunately this is in some kind of expo center and there isnt readily available air to the spot our display is. i think the max our cannon can cost (not including the raw materials like chamber, barrel and stuff like that or manhours is about $500
That seems like a reasonable budget, especially if i can find a cheap compressor or find something that is generally popular i can borrow or even purchase for myself and let them use.
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Unread postAuthor: Gun Freak » Sat Aug 24, 2013 5:03 pm

You can get a scuba tank and regulator cheap if you know where to look!! The whole setup should cost nowhere near 500!
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Unread postAuthor: ryanzander » Sat Aug 24, 2013 5:43 pm

okay, educated myself on the sprinkler valve a little, where do i get these? local hardware store or ebay? Next, if im using a 3.25" Inner Diameter barrel thats say three feet long, is the 1" sprinkler valve going to flow the volume of air that i need at 100 psi?
And im going to try to educate myself on the scuba regulator, i understand the basic mechanics of it, but if its main purpose is to knock down the pressure from the tank to the breather, how would that help? If im just an idiot and missing something clearly obvious, you can say so :) Sorry im such a noob. My area of expertise is offroad chassis fabrication and welding, so these are things i havent experimented with, thanks Gun Freak for your patience and knowledge.
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Unread postAuthor: Gun Freak » Sat Aug 24, 2013 6:35 pm

You can get them at Home Depot, or your equivalent hardware store. People have made tennis ball launchers using that as the main valve and since you're launching such a short distance I think a large piston valve is a little overkill. Of course other members will soon chime in and say what they think about the valve situation, so don't jump the gun just yet. In my opinion a 1" sprinkler valve will work, but there are also other valves you can use that would be better. For example, there are large Quick Exhaust Valves that would probably work better and are made of metal. Here is one example, unlike a sprinkler valve it is actually designed for air, but it's only 3/4":
http://www.mcmaster.com/#6646k23/=o7jt39

There are also dust collector valves, which I am not an expert on. People have used them here with great success for golf ball guns and things like that. You can find them on eBay if you just type in dust collector valve.
Or here are some on McMaster... they are rather expensive but have much larger ports than QEVs:
http://www.mcmaster.com/#dust-collector-valves/=o7jvt8

Then you have the best option of using a piston valve. Just click on the first link in my signature to see what I mean. They aren't complicated to make but some people prefer to use a ready-made valve. This type of valve could put a baseball a couple hundred yards... So you don't really need to make one.


Scuba tanks are filled to 3000 psi which is far too much for this purpose. The regulator will keep the output pressure within the safe limits of your gun. You could of course slowly fill the gun from the scuba tank with no regulator and carefully monitor the pressure, simply cutting off the supply when you reach the desired pressure, but this is extremely dangerous because you could easily make a mistake and you'll have a bomb in your hands.
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Unread postAuthor: grumpy » Sat Aug 24, 2013 9:48 pm

a scuba reg has several outlets on it, you want to use the low pressure outlet ( around 200 psi ) you hook this up to a secondary regulator to get it to the pressure you want. hook the second reg to your cannon and you have a constant air supply. how many shots you get will depend on how big your cannons air chamber is. and yes a 1 inch sprinkler valve will be easiest to run on constant air.
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Unread postAuthor: Brian the brain » Sun Aug 25, 2013 5:36 am

I suggest you ditch the idea of putting the ball in a barrel.
Too much hassle to " reload" .
Just make guiderails like in the original thing and ram the ball out with an airram.
Have them sit in a row, dropping onto the airram by gravity.Only way out is up through the rails.

You'll limit the noise output, airconsumption and wear.
The airchamber won't have to be as big, it'll just be used to fill the airram...fast!

Just use the regulator on the output of the compressor to adjust the pressure to your requirements and use fast valve setup to pop that airram.
You could use a leaky homebuilt airram ( leaky is good as it resets itself) or use a commercial aircilinder and switch the airflow to reset it.

I suggest just building one yourself.You can choose the size of the in-port to match your valve.

An airram is nothing but a captive piston with a rod placed inside a " barrel" with an endcap.

The rod sticks out the endcap and will be used to drive the ball.
Without O-rings on that piston it will still work, but it won't have to fight the pressure to return to firing position.
Springs can be used to help it return.

A 3" barrel , 2-3 feet long should do the job.
A pistonvalve piloted by a solenoid should be sufficient to drive a ball probably beyond what you need.
Just press a button to launch.

You can test this method at low cost if you doubt me.
You'll need to tinker with the pressure to get it just right, but after that it should be quite consistent.
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Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: ryanzander » Sun Aug 25, 2013 11:18 am

Thanks guys for all the info! Im not sure which way we're going to go yet, Another struggle i can see coming now is a way to make everything smooth looking. Im going to have to make the chamber, do whatever valving and what not to lead to the barrel or ram or whatever, and its basically all going to have to be contained in what appears to be either a 3.5" or 5" pipe bent with a 180 degree bend and no seams.
Im sure we're going to be building two models. i kind of like the ram idea as it seems practical for what we're doing, and rather cheap, assuming i can find a ram. I only have a couple hours a day here and there for two weeks to get this done. And then we'll build an all-out completely overkill straight up launcher version, just for funsies.
I'll be sure to get some pics/sketches put up when i go to work tomorrow so you guys can visualize whats going on. I'll need to do some shopping around and see what i can cook up.
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Unread postAuthor: Technician1002 » Sun Aug 25, 2013 11:59 am

Is now a good time to mention GGDT? If the baseball needs to make a lob at low speed, using the trajectory tool to work backwards from a desired muzzle velocity could save a lot of over kill in power.

For all metal, the plastic sprinkler valve can be replaced by a dust collector valve. A small chamber can be used to limit the energy of your launch to design goals, while reducing the volume of air needed so for the dozen or so needed shots, a rented Nitrogen tank and regulator may be all you need for totally silent air supply.
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Unread postAuthor: Bezee » Sun Aug 25, 2013 12:16 pm

i agree with btb. This is not a job for a airgun. Your better off using an air ram to "kick" the ball up. You then can rig it up to the pull thing on a pinball table to set the air ram of. If you are going to do this idea, make sure the ram can return quickly. Have fun!!! :D
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Unread postAuthor: ryanzander » Sun Aug 25, 2013 7:25 pm

Hmm, i will definitely look into the air ram, i just hope i can get one that really kicks it!
I am impressed with the amount of knowledge and especially the warm welcome to a first time poster! I've never had this good of a reception on any forum before. The guys here at Spudfiles really are top notch, i thank everyone here and the creators and mods for this forum!
Whether this is a ram or we go cannon or end up doing both, im pretty sure i owe you guys at least some pics so you can see what we end up doing. Im convinced were going to build an overpowered beast for the heck of it at the shop.
Tomorrow i will at least try to get a snapshot of the "pinball" machine. Dont expect anything serious as its made of some of the products we make and the processes used to make them. I'll explain where we're at and where we're going.
Thanks again guys for the warm welcome, the pool of knowledge and keeping a wonderful informative community! I think i will try to become a regular here and absorb what i can, thanks!
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Unread postAuthor: Gun Freak » Sun Aug 25, 2013 8:55 pm

When people like you come on here asking for help we have no opposition to giving it. You clearly stated what you were trying to do and what you have to do it with, asked direct, clear questions, and you write in an understandable manor.

When ignorant 12 year olds come on here asking "how to builds teh piston vavle?!", that's when we don't offer help.

If you do decide to become a regular, we'd be thrilled to have you! Be careful though because its easy to get hooked ;)
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