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 :: 4 registered, 0 hidden and 39 guests


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

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

The Team
Administrators
Global Moderators
global_moderators.png CS

Will this work or not?

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

Will this work or not?

Unread postAuthor: Tobin » Sun Sep 05, 2010 5:07 am

After my first successful gun, I'm on the theoretical stage of a airgun. I want to make a reloading mechanism so i don't have to refill the chamber after each shot. This is my idea:
Image
Look att picture 3
Then i pull the trigger i will release air into the little chamber. When the pressure between the big and the little chamber is almost even the spring will have power to pull the piston against the barrel again. Then i turn the trigger 90 degrees and release the pressure in the little chamber, then continue to turn the trigger 225 degrees and then I'm ready to shot again.

Thoughts about it? :)
  • 0


Tobin
Private First Class
Private First Class
 
Posts: 39
Joined: Mon Aug 16, 2010 5:25 pm
Reputation: 0

Unread postAuthor: grock » Mon Sep 06, 2010 2:50 am

no.

if your drawing is to scale, your going to have a pretty lame shot unless you use high pressures, because the chamber is pretty small.

also keep in mind that your shots get progressivly weaker, as your main chamber pressure decreases.

then there is the matter of the valve. do you have a 4 way valve? also, because of the layout of your gun, when you vent the "pilot" all the air will go out of it, and none will go out the barrel, because youre not making a pressure differential to push the piston open with. the chamber and the pilot areas must be separate.

what you could do is make a T piston gun, and have the firing chamber connected to your main chamber by a ball valve. it would be easier to make or get than a 4 way valve, and would be easier to use.


EDIT: actually, as an afterthought, with the design in the drawing, when you filled your firing chamber, it might fire the main chamber, because you would essentially be creating a low pressure zone behind the piston, with a high pressure one next to/in front of it
  • 0

User avatar
grock
2nd Lieutenant
2nd Lieutenant
 
Posts: 231
Joined: Mon Dec 29, 2008 2:59 pm
Reputation: 0

Unread postAuthor: Tobin » Tue Sep 07, 2010 2:17 pm

grock wrote: no.

if your drawing is to scale, your going to have a pretty lame shot unless you use high pressures, because the chamber is pretty small.

also keep in mind that your shots get progressivly weaker, as your main chamber pressure decreases.



Hi, its not to scale, and the painted piston-valve is just painted to mark that there will be a piston there, not how it will look like. My thought is to use about 40bar and to have a chamber that allows 4 bullets to be shot without falling more than 6-10 bar. I don't know how realistic that is, but its my goal.

My only question was about the idea with the small chamber and the 3 way valve. And this should work? With the right spring at the piston and right size on the small chamber, the piston should seal the barrel about the same time the bullet leaves the barrel?

grock wrote:then there is the matter of the valve. do you have a 4 way valve? also, because of the layout of your gun, when you vent the "pilot" all the air will go out of it, and none will go out the barrel, because youre not making a pressure differential to push the piston open with. the chamber and the pilot areas must be separate.

But when you wrote about the valve, I started thinking more about this.
The pilot area is the area behind the piston right?
You say that the chamber and pilot areas has to be separate, do they?
http://www.youtube.com/watch?v=C-zHW69Y ... re=related
This movie shows a pretty large space between the piston and the wall of the valve.
Or did i get you wrong?

grock wrote:what you could do is make a T piston gun, and have the firing chamber connected to your main chamber by a ball valve. it would be easier to make or get than a 4 way valve, and would be easier to use.


EDIT: actually, as an afterthought, with the design in the drawing, when you filled your firing chamber, it might fire the main chamber, because you would essentially be creating a low pressure zone behind the piston, with a high pressure one next to/in front of it


Doesn't really get how you mean that i should use a 4-way valve, neither the T piston gun. I'm not so in to pneumatic guns yet :scratch:
  • 0


Tobin
Private First Class
Private First Class
 
Posts: 39
Joined: Mon Aug 16, 2010 5:25 pm
Reputation: 0

Unread postAuthor: Technician1002 » Tue Sep 07, 2010 7:27 pm

The gap shown in the video is exaggerated to show there is some coupling between the chamber and pilot area. In real life this has to be extremely small.

If you browse the forum, there are many posts of piston valves that won't fire. The air just blows out the pilot valve.

For a reality check, the piston has to fit with a gap like the ones below.
Image

Image

If the gap is too small (very hard to do) a small EQ port can be drilled between the chamber area if the piston and the pilot area. Again, this is SMALL.
Image

The one in the video is large for illustration purposes. The pilot will be unable to lower the pilot side pressure enough to fire it.
  • 0

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

Return to Pneumatic Cannon Discussion

Who is online

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

Reputation System ©'