Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 43 users online :: 6 registered, 0 hidden and 37 guests


Most users ever online was 218 on Wed Dec 07, 2016 6:58 pm

Registered users: Bing [Bot], Exabot [Bot], Google [Bot], Google Adsense [Bot], jimmy101, Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

Best pneumatic launcher for cabbage?

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.
Sponsored 
  • Author
    Message

Unread postAuthor: LastXdeth » Thu Sep 15, 2011 7:29 pm

Technician1002 wrote:If the cannon is to be used at a public event such as a pumpkin patch, care must be taken for liabilaty issues with the spectators. Insurance requirements may limit your choices in materials. Pumpkin Chukin has eliminated plastic barrels for safety reasons.

Is the cannon for personal rec use, or will it be part of a public event such as a harvest festival?


It's just for a school project, but I plan to play around with it in my backyard and mod it afther that.
  • 0


LastXdeth
Private
Private
 
Posts: 10
Joined: Thu Sep 15, 2011 3:47 pm
Reputation: 0

Unread postAuthor: Fnord » Thu Sep 15, 2011 7:59 pm

If you want a simple, not-too-powerful, low budget, 'safe' design, I'd just go with a spring loaded ball valve.
Try to get a fire extinguisher tank and have a 2" threaded nipple welded on at a machine shop. I doubt they'd charge you much more than $20. You can even drill the larger port hole yourself to save them a step (tech will post pictures in a second:).

I think harbor freight has 2" brass ball valves for somewhere between $20-30.
Not sure about where to get a spring... you could use a bunch of rubber bands if you're in a pinch.

A barrel... I'm not sure. As your local plumbing guys if they have any 6" scrap laying around that they don't want. ABS might be preferable in this case even if it's cell-core.

You're looking at $50-100 depending on your scavenging ability. You'll be able to mod/reuse the parts of this cannon in numerous other ways.

Here's a ggdt example.
  • 0

Attachments
cabbageballvalve.gif
500 ft-lbs is more than enough to kill someone, even with a soft projectile.

This may even be an under-estimation; a spring/ball valve has an irregular sine-wave opening curve, whereas the "generic valve" is a linear flow increase.
Image
User avatar
Fnord
Major General
Major General
 
Posts: 2244
Joined: Tue Feb 13, 2007 9:20 pm
Location: Pripyat
Reputation: 7

Unread postAuthor: Technician1002 » Thu Sep 15, 2011 8:21 pm

Hmm, You mention a Fire Extinguisher and then list a large chamber in GGDT. I was going to mention a BBQ grill bottle instead. For a 6 inch barrel, I would recommend at least a 5 gallon tank and a valve larger than 2 inch.

I heard my name called. Here is the photo of a tank being modified for a 2.5 inch pipe..
Image

A 2.5 inch fitting has replaced the 3/4 inch stock one for much better flow.
Image
  • 0

User avatar
Technician1002
Chief of Staff
Chief of Staff
 
Posts: 5190
Joined: Sat Apr 04, 2009 11:10 am
Reputation: 14

Unread postAuthor: Fnord » Thu Sep 15, 2011 8:26 pm

I don't think 6x24 is that large for a fire extinguisher... it's not a common size but I bet the local fire department has a few they'd be willing to part with.

I know the place I used to work at had probably a hundred of them of similar size just stashed away... unpressurized, probably long due for a hydrotest.
Also I was thinking handheld but a propane tank like tech's will still preform better.

edit, that big yellow one(in the link vv) would be excellent but I'm pretty sure it's aluminum:
http://www.spudfiles.com/forums/fire-ex ... 23245.html
  • 0

Image
User avatar
Fnord
Major General
Major General
 
Posts: 2244
Joined: Tue Feb 13, 2007 9:20 pm
Location: Pripyat
Reputation: 7

Unread postAuthor: LastXdeth » Thu Sep 15, 2011 10:06 pm

Would a 5 gallon (about 20 liter) chamber be sufficient? I'm afraid I can't find an insane one (26 gallon) for free. I can pump up to 90 PSI.

One final question. Is it really that easy to install a barrel and a chamber with a butterfly valve? I need to buy a flanged adapter too also, right?
  • 0


LastXdeth
Private
Private
 
Posts: 10
Joined: Thu Sep 15, 2011 3:47 pm
Reputation: 0

Unread postAuthor: Technician1002 » Thu Sep 15, 2011 11:15 pm

A 5 gallon is a little small, but will work fine. The tank on my QDV is a 3 gallon tank and I have used it with a 4 inch barrel. The issue was the valve size more than it was tank size.

Acceleration testing shows continued acceleration all the way to the muzzle at 5.5 feet. Air tank volume is sufficient at 60 PSI and above.

Photo of acceleration testing of the 4 inch barrel on the 3 gallon tank.
Image

Not a great video, but here is a video of that combination shooting a 4 inch ball.
http://inteltrailblazerschallenge.wikispaces.com/file/view/4+inch+foam.avi

Butterfly valves come in various configurations. You can use bolt flanges if you wish.
Image
  • 0

User avatar
Technician1002
Chief of Staff
Chief of Staff
 
Posts: 5190
Joined: Sat Apr 04, 2009 11:10 am
Reputation: 14

Unread postAuthor: jackssmirkingrevenge » Thu Sep 15, 2011 11:36 pm

LastXdeth wrote:One final question. Is it really that easy to install a barrel and a chamber with a butterfly valve? I need to buy a flanged adapter too also, right?


Eliminating the valve and simply putting a bit of frangible material between the barrel and chamber flanges gives you a burst disk launcher as has been previously suggested.

"good" column:

cheap
fantastic performance no other valve type can keep up with

"bad" column:

bigger reload time
slight delay between trigger pull and firing, unless you opt for a dual disk setup.

Image
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Sponsored

Sponsor
 


Unread postAuthor: Technician1002 » Thu Sep 15, 2011 11:57 pm

@JSR Burst disk pros and cons were mentioned on page one. The triggered dual disk was mentioned too. Thanks for providing a detailed diagram of the operation.
  • 0

User avatar
Technician1002
Chief of Staff
Chief of Staff
 
Posts: 5190
Joined: Sat Apr 04, 2009 11:10 am
Reputation: 14

Unread postAuthor: jackssmirkingrevenge » Fri Sep 16, 2011 12:02 am

Technician1002 wrote:Burst disk pros and cons were mentioned on page one.


Right you are, checking spudfiles while trying to focus on work is a bad idea :roll:
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: LastXdeth » Fri Sep 16, 2011 8:12 pm

Would I have to go to a machine shop to cut my propane tank to a better fitting? When installing a filling valve such as a Schrader valve, can I use a carbide-tip and drill a hole?

Sorry if my questions are ridiculous, but my engineering skills are horrible.
  • 0


LastXdeth
Private
Private
 
Posts: 10
Joined: Thu Sep 15, 2011 3:47 pm
Reputation: 0

Unread postAuthor: Fnord » Fri Sep 16, 2011 9:19 pm

If you don't know anyone that can weld it then yes. But you can probably try enlarging the port by drilling it yourself (refer to what Tech posted).

What tools do you have available? Most normal drill bits go through steel just fine as long as you don't force them. Pressure tanks aren't usually hard alloys for obvious reasons.
  • 0

Image
User avatar
Fnord
Major General
Major General
 
Posts: 2244
Joined: Tue Feb 13, 2007 9:20 pm
Location: Pripyat
Reputation: 7

Unread postAuthor: Technician1002 » Fri Sep 16, 2011 9:29 pm

LastXdeth wrote:Would I have to go to a machine shop to cut my propane tank to a better fitting? When installing a filling valve such as a Schrader valve, can I use a carbide-tip and drill a hole?

Sorry if my questions are ridiculous, but my engineering skills are horrible.


Don't use a masonry carbide bit on steel. Use a High Speed Steel (HSS), Titanium, or tool steel bit. Normal high speed twist bits work fine. Use a little oil. If it smokes. slow down.
  • 0

User avatar
Technician1002
Chief of Staff
Chief of Staff
 
Posts: 5190
Joined: Sat Apr 04, 2009 11:10 am
Reputation: 14

Unread postAuthor: LastXdeth » Sat Sep 17, 2011 2:46 pm

I cannot find a butterfly valve anywhere in my local hardware stores and and called all of them to find out that they carry the same exact valves. They only have 1 inch ball valves, and the trigger handles are not even springs, so I have to trigger my launcher by turning.

Also, my propane tank has a 1 inch stock, and I'm afraid I cannot weld it for 2 reasons: 1)No welding experience 2)Don't know any welders.

Would a one inch ball valve be sufficient enough to accelerate a cabbage through a 6 inch wide (5-6 feet long) PVC barrel at least 15 meters if I fill the air chamber to around 90 PSI?
  • 0


LastXdeth
Private
Private
 
Posts: 10
Joined: Thu Sep 15, 2011 3:47 pm
Reputation: 0

Unread postAuthor: Technician1002 » Sat Sep 17, 2011 3:55 pm

Local hardware stores are for homeowners to furnish their homes. There is no use for one of those for a typical suburban resident. You need to look to commercial public works or industrial type suppliers.
  • 0

User avatar
Technician1002
Chief of Staff
Chief of Staff
 
Posts: 5190
Joined: Sat Apr 04, 2009 11:10 am
Reputation: 14

Unread postAuthor: Gippeto » Sat Sep 17, 2011 3:59 pm

Are you trying to "splat" the cabbage at 15m or simply have it get that far...roll included?

A cabbage is a fairly respectable projectile mass wise...shouldn't take much in the way of muzzle velocity to get it to simply travel 15m. Lower velocity requirements reduce the need for high flow valves.

Where are you located? Odd mixture of metric and imperial that you use quite naturally....similar to what I find myself doing. :lol:
  • 0

"It could be that the purpose of your life is to serve as a warning to others" – unknown

Liberalism is a mental disorder, reality is it's cure.
User avatar
Gippeto
Donating Member
Donating Member
 
Posts: 2394
Joined: Sat Jan 19, 2008 10:14 am
Location: The Great White North...Canada eh!
Reputation: 11

PreviousNext

Return to Pneumatic Cannon Discussion

Who is online

Registered users: Bing [Bot], Exabot [Bot], Google [Bot], Google Adsense [Bot], jimmy101, Yahoo [Bot]

Reputation System ©'