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 59 users online :: 4 registered, 0 hidden and 55 guests


Most users ever online was 155 on Mon Aug 15, 2016 1:40 am

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

The Team
Administrators
Global Moderators
global_moderators.png CS

low/no power-mini metal coax

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

low/no power-mini metal coax

Unread postAuthor: Pyro Ninja » Wed Dec 26, 2007 1:51 am

Normally I wouldn't post about a "small" problem like this one but I am getting really tired of screwing around with piston valves.
Well I have a couple of "guns" I need to finish before the end of the holidays, anyway I have built a small full metal coaxial.
Originally it was going to have a diaphragm valve, but with that failing a decided to go with a piston.

I made a piston from a small rubber cork by -ghetto machining- it to the right size.


SPECS

Chamber- 15mm galvanized steel
Barrel- 9mm id aluminum
Pilot valve- 1/4 ball valve
I know, not very detailed specs

Image

Image

Image

Image

The piston seals perfectly, but when I pilot it, there is only a small spurt of air out the barrel.
I can only get it up to 100psi, but the power should be more then what it is.
  • 0

User avatar
Pyro Ninja
Major
Major
 
Posts: 351
Joined: Mon Oct 09, 2006 7:11 am
Location: Australia
Reputation: 0

Re: low/no power-mini metal coax

Unread postAuthor: jackssmirkingrevenge » Wed Dec 26, 2007 2:24 am

Pyro Ninja wrote:I can only get it up to 100psi, but the power should be more then what it is.


Not really, for such a miniscule chamber volume at 100 psi I would expect it to be of very low power.
  • 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: Pyro Ninja » Wed Dec 26, 2007 2:49 am

Can't say I am pleased with your answer Jack (I thought you would come up with some kind of super effective answer to solve my problem :? )
So there absolutely nothing I can do to improve power?

I guess i'll have to buy a shock pump when I make a bit of money.

In the second last picture the copper pipe around the aluminum is only a short length just to relieve some of the stress on the piston.
  • 0

User avatar
Pyro Ninja
Major
Major
 
Posts: 351
Joined: Mon Oct 09, 2006 7:11 am
Location: Australia
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Wed Dec 26, 2007 2:52 am

If you decide to keep the current setup as it is, then higher pressure is really the only solution for more power. With your all metal construction it would be safe to go to the 350-400 psi a shock pump can give you, and if you keep pilot volume low a shrader will be enough to both fill and pilot the launcher.
  • 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: Hotwired » Wed Dec 26, 2007 6:08 am

Umm...

I can see perhaps 2-3mm of clearance round the inner tube as the chamber.

I suspect I might have slightly more chamber volume in my high presure test rig which is literally a 15mm compresson elbow, a ball valve, a barrel and a schrader.

That's filled to 400psi with a shock pump and even up to a 1m barrel it's still got really naff power, but that wasn't what it was about ^_^

Be generous! Give yourself a non-thimble-sized chamber for Boxing Day and all will be well :)
  • 0

User avatar
Hotwired
Lieutenant General
Lieutenant General
 
Posts: 2599
Joined: Fri Oct 13, 2006 5:51 am
Location: UK
Reputation: 0

Unread postAuthor: carter » Wed Dec 26, 2007 7:47 pm

that is a tiny chamber. is there any chance that you could extend it if you wanted to?
  • 0

At my lemonade stand I used to give the first glass away free and charge five dollars for the second glass. The refill contained the antidote

carter
Corporal
Corporal
 
Posts: 77
Joined: Mon Mar 05, 2007 2:47 am
Reputation: 0

Unread postAuthor: Pyro Ninja » Wed Dec 26, 2007 8:29 pm

Well the chamber is approximately 15mL so that would give me 15 cubic cm of air.
The barrel is about 12 cubic cm
What kind of power should I expect at say, 200-300psi
  • 0

User avatar
Pyro Ninja
Major
Major
 
Posts: 351
Joined: Mon Oct 09, 2006 7:11 am
Location: Australia
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: jackssmirkingrevenge » Wed Dec 26, 2007 9:58 pm

Pyro Ninja wrote:What kind of power should I expect at say, 200-300psi


two-three times what you're currently getting. 15mL is the sort of volume I use as a minimum for my 6mm calibre mini-pistons, you should be looking to increase it for this project.
  • 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

Return to Pneumatic Cannon Discussion

Who is online

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

Reputation System ©'