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 65 users online :: 6 registered, 0 hidden and 59 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], MSNbot Media, Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

Two questions from a new cannon builder

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: john bunsenburner » Mon Dec 29, 2008 7:41 am

By all means dont get into the idea of using water for such low pressures...If you own a bike pump you will have the same thing for a fraction of the cost, time and worries. Further more the water pressures in pipe lines can varry greatly from place to place, it being 145psi in switzerland and about 50 in the US... A hand pump can really achieve all kinds of pressure, look up high pressure hand pumps, they can reach 3000psi so really they can be all you need.
A bulk tank is an ok idea but prices vary, for me the best deal was to use my scuba tanks fill em up for about 3$ to 3000-4000psi and then strap a regulator on, but that may be different in your area. Really the only time you would want a bulk tank is when working with helium or hydrogen inorder to break the sound barrier, but that is another matter. For your first cannon use a bike pump, anything else coupld result in you blowing your self up(especially with a PVC cannon).
Look around in the pneumatic showcase area of the forum, there are lotsof simple cannons there which you could look at for insperation.
  • 0

"Did you ever stop to think that out of the seven deadly sins envy is the only one which doesn't give the sinner even momentary pleasure"-George Will
User avatar
john bunsenburner
Major General
Major General
 
Posts: 1446
Joined: Sun Oct 19, 2008 5:13 am
Reputation: 0

Unread postAuthor: jared555 » Mon Dec 29, 2008 7:54 am

I wasn't planning on truely using water, more just curiosity. At what point (PSI) do you risk causing catastrophic failure in the bike pump? (I am assuming this is after the pvc explodes but still, always good to ask)
  • 0


jared555
Private
Private
 
Posts: 24
Joined: Sun Dec 28, 2008 8:23 pm
Reputation: 0

Unread postAuthor: john bunsenburner » Mon Dec 29, 2008 8:06 am

you cant pump up to pressures that high m8, itll be so hard to pump, no way in hell you can, but i guess its around 400psi when things start failing... remember there are alot of things that will just let air out at a specifict pressure(the check valve, tubing, threads) I doubt you could manage to just burst the pump, besides with a bulk and the desire to do so...
  • 0

"Did you ever stop to think that out of the seven deadly sins envy is the only one which doesn't give the sinner even momentary pleasure"-George Will
User avatar
john bunsenburner
Major General
Major General
 
Posts: 1446
Joined: Sun Oct 19, 2008 5:13 am
Reputation: 0

Unread postAuthor: jared555 » Mon Dec 29, 2008 12:31 pm

Would I probably get better results out of an unmodified sprinkler valve or a ball valve for my first cannon?
  • 0


jared555
Private
Private
 
Posts: 24
Joined: Sun Dec 28, 2008 8:23 pm
Reputation: 0

Unread postAuthor: Mateo » Mon Dec 29, 2008 12:55 pm

i think even an unmodded sprinkler is faster than a ball valve. for you first a ball valve would be fine but you would quickly get bored of its performance. you could attach it to a spring to help it open quicker but still a sprinkler beats it. also if you could, dont glue the sprinkler in. just use teflon tape(available almost everywhere in plumbing section) and thread it. that way when you get bored of your first cannon you could just unscrew it and still have the valve.
  • 0

User avatar
Mateo
Sergeant
Sergeant
 
Posts: 80
Joined: Sun Oct 21, 2007 8:42 pm
Reputation: 0

Unread postAuthor: jared555 » Mon Dec 29, 2008 12:59 pm

Would stores thread the PVC pipe or are there either cheap tools or pre threaded pipe available?
  • 0


jared555
Private
Private
 
Posts: 24
Joined: Sun Dec 28, 2008 8:23 pm
Reputation: 0

Unread postAuthor: john bunsenburner » Mon Dec 29, 2008 2:37 pm

Tools are not cheep but ask the guy who does your pipe lines or toilets, they can thread any pipe for you(ussually fro free)
  • 0

"Did you ever stop to think that out of the seven deadly sins envy is the only one which doesn't give the sinner even momentary pleasure"-George Will
User avatar
john bunsenburner
Major General
Major General
 
Posts: 1446
Joined: Sun Oct 19, 2008 5:13 am
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: frankrede » Mon Dec 29, 2008 2:49 pm

john bunsenburner wrote:By all means dont get into the idea of using water for such low pressures...If you own a bike pump you will have the same thing for a fraction of the cost, time and worries. Further more the water pressures in pipe lines can varry greatly from place to place, it being 145psi in switzerland and about 50 in the US... A hand pump can really achieve all kinds of pressure, look up high pressure hand pumps, they can reach 3000psi so really they can be all you need.
A bulk tank is an ok idea but prices vary, for me the best deal was to use my scuba tanks fill em up for about 3$ to 3000-4000psi and then strap a regulator on, but that may be different in your area. Really the only time you would want a bulk tank is when working with helium or hydrogen inorder to break the sound barrier, but that is another matter. For your first cannon use a bike pump, anything else coupld result in you blowing your self up(especially with a PVC cannon).
Look around in the pneumatic showcase area of the forum, there are lotsof simple cannons there which you could look at for insperation.

hmmm...hydrogen....
  • 0

Current project: Afghanistan deployment
User avatar
frankrede
Lieutenant General
Lieutenant General
 
Posts: 3220
Joined: Thu Jul 20, 2006 9:47 pm
Reputation: 0

Unread postAuthor: john bunsenburner » Mon Dec 29, 2008 2:53 pm

what did I do wrong?
  • 0

"Did you ever stop to think that out of the seven deadly sins envy is the only one which doesn't give the sinner even momentary pleasure"-George Will
User avatar
john bunsenburner
Major General
Major General
 
Posts: 1446
Joined: Sun Oct 19, 2008 5:13 am
Reputation: 0

Unread postAuthor: Big Boom » Mon Dec 29, 2008 2:56 pm

Why do you need to thread pipe? ... Just use the threaded fittings.
  • 0


Big Boom
Private First Class
Private First Class
 
Posts: 38
Joined: Mon Jun 09, 2008 6:21 pm
Reputation: 0

Unread postAuthor: MrCrowley » Mon Dec 29, 2008 3:05 pm

jared555 wrote:Would stores thread the PVC pipe or are there either cheap tools or pre threaded pipe available?

You buy threaded PVC fittings and glue them to the PVC... :roll:
Image
  • 0

User avatar
MrCrowley
Moderator
Moderator
 
Posts: 10207
Joined: Fri Jun 23, 2006 10:42 pm
Location: Auckland, New Zealand
Country: New Zealand (nz)
Reputation: 4

Unread postAuthor: john bunsenburner » Mon Dec 29, 2008 3:07 pm

Ya, i had something similar going through my mind...
  • 0

"Did you ever stop to think that out of the seven deadly sins envy is the only one which doesn't give the sinner even momentary pleasure"-George Will
User avatar
john bunsenburner
Major General
Major General
 
Posts: 1446
Joined: Sun Oct 19, 2008 5:13 am
Reputation: 0

Bike pumps, water pressure and catastrophic failure:

Unread postAuthor: DR » Tue Dec 30, 2008 12:47 am

Ha!

After reading all of the replies to this topic (after the post about using water pressure to fill your cannon) , I'm left thinking that some of you may not understand the concept, so here goes:

1.) Of course it ties you down to your backyard, or to anywhere that actually has a hose bib, but it is a cheap alternative to having NO compressor at all.

2.) The "compressor chamber" must be a larger volume than your launcher's chamber, to maximize whatever pressure that is available at the hose bib.

3.) Even though someone posted that the water pressure overseas may be close to 140+ psi, the pressure IS controllable, as it DOES take a while to fill the "compressor chamber"; Using the ball valve ( V1 ) as a flow control, you only have to barely crack it open, to fill the chamber slowly enough to prevent over-pressurizing. - Most launcher fabricators will incorporate a pressure gauge on their chamber anyway, so just shut the supply off when you've met the desired pressure.

4.) Filling a ball-valve actuated launcher is just fine, with a bike pump.
But filling a modded-sprinkler valve actuated launcher will sometimes not work, especially if you have a large chamber. The reason being, is that a sprinkler valve's diaphragm has a tiny equalization port in it... When filling a larger chamber, each pump from your "bike pump" adds only a fraction of a pound-per-square-inch of pressure. This fractional pressure will quickly bleed out of that hole, unless you can pump like your Beavis on Ritalin. - You could overcome this dilemma (of course) by adding a ball valve between the chamber outlet and your sprinkler valve (same diameter) ... and this is (of course) an unwanted addition, for most.

5.) The least expensive alternative (by far) is to use a disposable propane tank, to pressurize your launcher. Propane IS heavier than air, so you WILL lose a small amount of "performance". And let us not forget:
Propane IS flammable!!! ---

Image below lists the vapor pressure inside a propane container, at a particular temperature, containing some liquid but not more than 80% total capacity. This allows for a 20% vapor space. (courtesy: <a href="http://www.propanecarbs.com/propane.html">Alternate Fuels Technologies, Inc</a>

<img src="http://www.propanecarbs.com/propan4.jpg">

I've used those little 16.4 oz. disposable propane bottles to pressurize many different launchers. Using them in weather below 50*F, runs the risk of your fill valve freezing, so be careful if attempting to use this.

Any leaks in your launcher and a small spark, would be all it would take to render you F.U.B.A.R, so do so at your own risk!

To me though, using CO2, with the bottle filled to a whopping 800psi, is far more dangerous, and the darn bottle will always freeze up at temperatures below 40, anyway.
  • 0

User avatar
DR
Sergeant Major
Sergeant Major
 
Posts: 179
Joined: Fri Oct 08, 2004 8:16 pm
Reputation: 0

Unread postAuthor: john bunsenburner » Tue Dec 30, 2008 8:12 am

And propane wont freeze your pvc?
and that is one of the reasons i am against sprinklers...
  • 0

"Did you ever stop to think that out of the seven deadly sins envy is the only one which doesn't give the sinner even momentary pleasure"-George Will
User avatar
john bunsenburner
Major General
Major General
 
Posts: 1446
Joined: Sun Oct 19, 2008 5:13 am
Reputation: 0

Unread postAuthor: inonickname » Tue Dec 30, 2008 11:40 am

...

No, you wont pressurize the room your in. No way. Still don't blank fire it 3 inches from your dear mother's china.. Keep in mind several things when using CO2. 1: it's inert, so you will need good ventilation (it's heavier than air, so windows won't help much...), 2: CO2 gets very cold, which turns PVC brittle. As for air compressors, I can't really reccomend anything. We have one with a gigantic tank that is easily powerful enough, but it requires a power source. Not a problem seen as I have an inverter in the car for my laptop, but it's still heavy.. A foot pump also works well.
  • 0

User avatar
inonickname
Lieutenant General
Lieutenant General
 
Posts: 2606
Joined: Sun Dec 07, 2008 3:27 am
Reputation: 0

PreviousNext

Return to Pneumatic Cannon Discussion

Who is online

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

Reputation System ©'