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Ammo for large pipes

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Ammo for large pipes

Unread postAuthor: geniusbomberman » Thu May 28, 2009 9:46 pm

I am thinking of making a large( 4 or 5 inch) barrel, and I want to know what would be good ammo for it. Do hardware or craft stores sell Styrofoam or wood cylinders that are this size, because that would be good. An obvious solution would be to take a piece of the next smallest size pipe, slightly make the bottom of it wider with the standard method and make PVC rockets. Would the projectile have to be pressure rated at all? This is for a combustion cannon.
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Re: Ammo for large pipes

Unread postAuthor: Technician1002 » Thu May 28, 2009 11:46 pm

geniusbomberman wrote:I am thinking of making a large( 4 or 5 inch) barrel, and I want to know what would be good ammo for it. Do hardware or craft stores sell Styrofoam or wood cylinders that are this size, because that would be good. An obvious solution would be to take a piece of the next smallest size pipe, slightly make the bottom of it wider with the standard method and make PVC rockets. Would the projectile have to be pressure rated at all? This is for a combustion cannon.


4 inch will fit 4 inch round poof brand foam balls and camping stove propane cylinders. Small grapefruit, large oranges and other produce is lots of fun.

5 inch is an odd size. 2 liter pop bottles would work, but the fit isn't the greatest. Cantaloupe small gourds and pumpkins are good for 5 inch to 12 inch cannons.

Depending on the pressure used, it does pay to figure out the recoil forces before launching heavy large diameter stuff. 100 PSI on a 3 inch barrel can push an object at over 700 LBS. :shock: Tread carefully when working with larger diameters.

How long have you been spudding?

Maybe I read your question wrong. Do you mean 4 or 5 inches long? :D
If so wooden dowels 2 inches and smaller in diameter are common and can be found in lengths exceeding 4 or 5 inches. :D

It is hard to find ammo for stuff over 3 inches in diameter. It gets expensive.

Use the math for the area of a circle and multiply the area times the pressure of combustion to get an idea of the expected recoil impulse force. In round numbers use 35-100 PSI. It varies between spray and pray and metered propane.

Area of a circle is Pi times radius squared. 5 inch has a 2.5 inch radius. Radius squared is 6.25. That times Pi (3.14) is about 19 square inches. If you have a heavy projectile and a 100 PSI combustion pressure rise, the force is 1900 Lbs. It's a Ton of force in round figures. Care to hand hold that cannon? Please be careful.
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4 inch test.JPG
Testing a 4 inch barrel.
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Unread postAuthor: jook13 » Fri May 29, 2009 12:13 am

I say take a section of the pipe to the grocery store and see what cans fit well inside of it. I made a 3 inch bore (schedule 40 pvc) and found some dog food cans that work great. The cans work even better after you use them and fill them with water then freeze em.

As tech said, be carefull of the recoil. At 100 psi I seriously hurt my wrist and cut my hand wide open. Worth it, but it sucked.

Tech... I dont think your 4 inch barrel counts. I consider it a 2 inch since that is the flow of your valve. :lol: :lol: :wink: :wink:
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Unread postAuthor: Technician1002 » Fri May 29, 2009 12:26 am

jook13 wrote:I say take a section of the pipe to the grocery store and see what cans fit well inside of it. I made a 3 inch bore (schedule 40 pvc) and found some dog food cans that work great. The cans work even better after you use them and fill them with water then freeze em.

As tech said, be carefull of the recoil. At 100 psi I seriously hurt my wrist and cut my hand wide open. Worth it, but it sucked.

Tech... I dont think your 4 inch barrel counts. I consider it a 2 inch since that is the flow of your valve. :lol: :lol: :wink: :wink:


I consider the 4 inch the same way. Still I only launch light weight stuff out of it. It's a 2 inch cannon with a 4 inch barrel attached. It can still launch a foam ball at over 500 FPS. 60 PSI got it to 454 FPS.

The one to watch out for is the 3 inch barrel on that thing. It about knocked me on my behind, even when I braced for it. I got a nasty bruise on my thigh where I braced the breech of the tank. Without the restriction of the 2 inch valve, the 4 inch would be a hazard to hold with anything heavy in it.

I'm working on a 3 inch valve cannon.

take a section of the pipe to the grocery store
:lol: :lol: :lol:

How about a small tape measure. :?:
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Last edited by Technician1002 on Fri May 29, 2009 12:33 am, edited 1 time in total.
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Unread postAuthor: jook13 » Fri May 29, 2009 12:33 am

I'm working on a 3 inch valve cannon.


Haha. I know about these plans. Trust me, you will enjoy the insane power of a 3 inch valve. It does not take much psi to impress.

http://www.youtube.com/watch?v=psnFmQmTQ84

This was at 60 psi. And I am sure that your valve will be more impressive.
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Unread postAuthor: Technician1002 » Fri May 29, 2009 12:37 am

jook13 wrote:
I'm working on a 3 inch valve cannon.


Haha. I know about these plans. Trust me, you will enjoy the insane power of a 3 inch valve. It does not take much psi to impress.

http://www.youtube.com/watch?v=psnFmQmTQ84

This was at 60 psi. And I am sure that your valve will be more impressive.


Sweet :D That's an impressive video. Need to invest in a tripod to remove the Blair Witch Project shakies. I like the recoil. Have you tried higher pressure? I'm targeting 200 PSI max.
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