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My first 2" cannon (just something little) :)

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 first 2" cannon (just something little) :)

Unread postAuthor: High-PSI » Tue Oct 12, 2010 7:43 am

Hey Guys,

Here are a couple quick pics of what little I have put together so far on my first 2 inch bore cannon.

The barrel is a 4 foot long sch 40 aluminum tube, the pressure tank is 4 inch exhaust tube and the valve is a 2 inch Granzow diaphram valve. The valve will be piloted by a second Granzow brass valve (1/2 inch bore). The pilot valve will be triggered pneumatically by a small trigger air valve.

I will be mounting twin grips and a shoulder rest/stock. The shoulder rest will be just under the valve. So, the pressure tank will wrap around my shoulder and run under my arm at my side. This should ballance the weight a bit.

The gun should be able to take 300 psi. However, I doubt my shoulder will be able to handle the recoil from that much pressure. Besides, my compressor is only good for 250 psi. I will start with 100 psi to see how the recoil feels and move up from there.

I will post more pictures as the build progresses.

Matt
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Unread postAuthor: jackssmirkingrevenge » Tue Oct 12, 2010 7:52 am

Looks like a valveless pulse jet :shock:

Very impressive, but with a fast valve and large chamber I think you'll find that even at 100 psi recoil will be quite punishing with a heavy projectile. Since you're evidently handy with a bit of metal work you might want to consider a muzzle brake to help mitigate the forces on your shoulder.

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Unread postAuthor: High-PSI » Tue Oct 12, 2010 8:10 am

Not a bad idea.

Also, don't muzzle brakes aid in projectile accuracy by venting pressure before the projectile exits the barrel, thereby reducing the tendency of the air blast from angling the projectile as it leaves the barrel?

Oh, if the recoil is too severe, I will add recoil dampening by way of a linera bearing that the grips and stock would be mounted to with a dampener added. The cannon is being built with this possible add-on being easy to do.

I forgot to mention, the gun is 3.5 to 1 ratio.........

Matt
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Unread postAuthor: jackssmirkingrevenge » Tue Oct 12, 2010 8:18 am

High-PSI wrote:Also, don't muzzle brakes aid in projectile accuracy by venting pressure before the projectile exits the barrel, thereby reducing the tendency of the air blast from angling the projectile as it leaves the barrel?


That's the theory, although unless you're using a properly made projectile like these fine rounds supplied by our benevolent sponsors, you wouldn't really notice the difference.

I forgot to mention, the gun is 3.5 to 1 ratio.........


For your own safety, and the safety of others, hearing protection ;)
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Unread postAuthor: High-PSI » Tue Oct 12, 2010 8:21 am

Yup, hearing protection all the way!

Also, yes, I ordered a dozen of those rounds. I already make that exact round for my 1/2 inch bore cannons and, quite frankly, for what they are charging for them, there is no reason for me to make my own. That is a very reasonable price! Heck, it takes me about 30 minutes to make a round like that on my lathe. I would rather buy them.

Matt
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Unread postAuthor: SpudFarm » Tue Oct 12, 2010 8:47 am

Looks good, another cannon that reminds me of the gun I was going to make some time ago, might be a project for you.

I was going to make a combustion with a 11kg propane tank as the chamber and 3" exhaust pipe for the barrel.
You will get good results from a 3" bore 300psi pneumatic :D

Good luck on your build.
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Unread postAuthor: jackssmirkingrevenge » Tue Oct 12, 2010 9:04 am

High-PSI wrote:Also, yes, I ordered a dozen of those rounds.


Excellent, we can expect some impressive damage pictures/videos in due course then :D
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Unread postAuthor: Technician1002 » Tue Oct 12, 2010 10:11 am

The recoil with a 1 lb projectile at 100 PSI in a 2 inch barrel isn't bad. 2 lbs will be OK. 2lbs in a 3 inch kicks hard. Are you considering larger screw on barrels?

In launching t shirts, even with a 2 inch valve, we got better launches with 2.5-3 inch barrels. The larger area makes a difference.

At 200 PSI, expect to get hurt with any projectile over 1 lb.
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Unread postAuthor: Benjg555 » Tue Oct 12, 2010 10:36 am

hey that baby looks awesome so far. Better than my first cannon. Looks like you have some experience in metal working cant wait to see it finished
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Unread postAuthor: High-PSI » Tue Oct 12, 2010 12:39 pm

Technician1002 wrote:The recoil with a 1 lb projectile at 100 PSI in a 2 inch barrel isn't bad. 2 lbs will be OK. 2lbs in a 3 inch kicks hard. Are you considering larger screw on barrels?

In launching t shirts, even with a 2 inch valve, we got better launches with 2.5-3 inch barrels. The larger area makes a difference.

At 200 PSI, expect to get hurt with any projectile over 1 lb.


Good info!

Big bore stuff is totally new to me. However, I had better results running a larger bore valve choked into a smaller barrel on my smaller bore guns. I saw an increase in muzzle velocity that way. However, I am open to trying anything.

I have a small machinshop. I have a benchtop CNC mill, 4 axis manual mill, and a small lathe. I also own a MIG welder. I can make pretty much anything. However, some things take more time than they are worth. So, I buy whatever I can.

Wait till you see the shoulder stock and other bits. :)

I sure hope it fires as good as it looks. I can tell you, the 1-1/4" valve I have that is pilotted by a second valve (the same arrangement as this) is freaking LOUD at only 50psi. The slug on the valve diaphram opens so incredibly fast that it sounds more like a bomb than an air cannon. I cannot imagine the SPL level of this 2 inch barrel at high pressure.

Matt
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Unread postAuthor: whoa044 » Tue Oct 12, 2010 2:42 pm

2" solenoid valve O.o How much did that cost?
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Unread postAuthor: High-PSI » Tue Oct 12, 2010 3:35 pm

That valve retails for $586. However, I am a retailer for them. So, I get a discount. I also do R&D for them. I do weird things (weird in their extimation). So, as I modify valves, I pass the learned information to the manufacturer and they treat me well. :)

Anyway, I may start selling two stage 2 inch pilotted valves if this one proves to be what my 1-1/4 inch valve is. Of course, these things are so freakin expensive, I am not too sure how many others would have any interest in one. But, I am open to it. I know I have access to equpiment that others do not. So, I am not against helping others out if they are interested.

Enough of that. Back to business! I will be back at teh shop tomorrow doing some work. I hope to have the pilot valve mounted, teh tank finished with all fittings installed, and the stock begun.

Matt
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Unread postAuthor: Technician1002 » Tue Oct 12, 2010 4:17 pm

On air cannons, not only is the chamber/barrel ratio important, so is the barrel to valve CV important. High flow valves are needed to make large bore barrels work.
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Unread postAuthor: High-PSI » Tue Oct 12, 2010 4:38 pm

Yes, understood. The flow rate is supposedly very high for this bore size, according to the manufacturer. We shall see how it performs in real life. :)

Edit: I just checked, the CV value for this valve is 53 according to Granzow. Is that high?

Matt
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Unread postAuthor: Gun Freak » Tue Oct 12, 2010 6:26 pm

That is a pretty good flow number.
This looks like a fun cannon, can't wait to see some damage pictures and a video maybe, also that valve is awsome. :)
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