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 :: 3 registered, 0 hidden and 62 guests


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

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

The Team
Administrators
Global Moderators
global_moderators.png CS

Need opinions/advice on a bb gun design

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
Sponsored 
  • Author
    Message

Re: Need opinions/advice on a bb gun design

Unread postAuthor: Brian the brain » Tue Jun 02, 2015 10:04 am

Thanks a lot Brian! I've been looking at your rifles for a few weeks now, hoping to make something simillar at some point. What I don't understand is how do you refill a coaxial valve for multiple shots? Is there another valve somewhere that I can't see that when opened, refils the coax? Thanks!


The valve does not dump all of the pressure.
The hammervalve is knocked open only for a split second, dumping the pilot volume and then after is shuts the main piston resets automatically.
An extra supply of air in the shoulderstock makes the total volume big enough to get multiple shots.
  • 0

Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
User avatar
Brian the brain
Moderator
Moderator
 
Posts: 3494
Joined: Mon Dec 05, 2005 2:06 am
Location: Holland
Country: Netherlands (nl)
Reputation: 29

Re: Need opinions/advice on a bb gun design

Unread postAuthor: gpopovic » Thu Jun 04, 2015 2:59 am

Thanks!

I think I get it, will try to make a drawing to clear it in my head :) Do you have an concept drawing perhaps?
  • 0

User avatar
gpopovic
Private
Private
 
Posts: 20
Joined: Sun May 03, 2015 2:46 am
Location: Belgrade
Country: Serbia (rs)
Reputation: 1

Re: Need opinions/advice on a bb gun design

Unread postAuthor: Brian the brain » Sat Jun 06, 2015 10:08 am

Very basic principle.
in a coax pistonvalve the piston seals against the barrel naturally because of the difference in pressure.Inside the barrel is normal atmospheric pressure, all around the exposed sides of the piston is high pressure.

If pressure behind the piston is dropped, the pressure around the barrel will push the piston back,opening the path to the barrel.

With a snug -but not airtight- piston fit...the piston will reset under pressure when the pilot valve closes because the pilot area is refilled almost instantly, while air is rushing out the barrel, creating a low pressure zone in front of the piston while pressure rises behind it,
Effectively sucking the piston back onto the barrel.Asif you are using a vacuumcleaner to suck a snookerball out of the pocket.

The pilotvalve needs to open fast and then almost instantly close again to keep as much of the pressure in the launcher, yet release enough out the barrel to lauch the projectile at full force.

With a hammervalve as the pilot..( I use a partially counterbalanced one for higher pressures)and a very small pilot volume this will give you multishot capacity with much more power than a hammervalve could provide on its own.

This works even without the extra airsupply coming in from the back.Important to know it is not required for the multishot effect.
I just needed more volume for more shots and I could hide an extra reservoir in the shoulderstock.

I guess you could do wonders with this concept!
  • 0

Attachments
Lilshat basic function.png
Lilshat basic function.png (9.51 KiB) Viewed 1108 times
Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
User avatar
Brian the brain
Moderator
Moderator
 
Posts: 3494
Joined: Mon Dec 05, 2005 2:06 am
Location: Holland
Country: Netherlands (nl)
Reputation: 29

Re: Need opinions/advice on a bb gun design

Unread postAuthor: gpopovic » Sat Jun 06, 2015 3:21 pm

Thanks a lot Brian, both for the drawing and the kind words!

It's actually simpler than I thought, great! :) I'm already thinking about the tubes that I already have at the shop,and the ways to hit the pilot... Some drawings are to follow!
  • 0

User avatar
gpopovic
Private
Private
 
Posts: 20
Joined: Sun May 03, 2015 2:46 am
Location: Belgrade
Country: Serbia (rs)
Reputation: 1

Re: Need opinions/advice on a bb gun design

Unread postAuthor: gpopovic » Wed Jun 10, 2015 3:35 am

Finally finishing the pcp. The barrel is threaded and epoxied in, and the reservoire is finally sealed. I will file it flush today and epoxy coat the surface. The action still needs some minor work, mostly due to my fingers being unable to place the 5.5mm pellet into the barrel from the first try :)

Imagepcp montaza1 by Goran P, on Flickr
  • 0

User avatar
gpopovic
Private
Private
 
Posts: 20
Joined: Sun May 03, 2015 2:46 am
Location: Belgrade
Country: Serbia (rs)
Reputation: 1

Re: Need opinions/advice on a bb gun design

Unread postAuthor: gpopovic » Wed Jun 10, 2015 3:52 am

Brian, I drew up something based on your concept, and tried to place it in the form of one of my favourite single shots, Remington Rolling block. Billie Dixon model, 30' barrel, completely to scale, just the barrel is thinner than the original, which is 30mm diameter. Mine is 22mm, and should be counterbalanced by the reservoire in the stock, so it's not too front end heavy.

Would it work? The inner barrel would be 10x2mm, which with some minor work works great with the 5.5mm lead pellets.

Imagebtbinspiredrolingblock by Goran P, on Flickr
  • 0

User avatar
gpopovic
Private
Private
 
Posts: 20
Joined: Sun May 03, 2015 2:46 am
Location: Belgrade
Country: Serbia (rs)
Reputation: 1

Re: Need opinions/advice on a bb gun design

Unread postAuthor: Brian the brain » Fri Jun 12, 2015 1:46 pm

For 5.5mm a pistonvalve is overkill..

You could use a hammervalve for that.
The benefit of a piston valve is you can use much bigger calibers.
I recently put a .50 barrel on Lil'Shat.
  • 0

Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
User avatar
Brian the brain
Moderator
Moderator
 
Posts: 3494
Joined: Mon Dec 05, 2005 2:06 am
Location: Holland
Country: Netherlands (nl)
Reputation: 29

Re: Need opinions/advice on a bb gun design

Sponsored

Sponsor
 


Re: Need opinions/advice on a bb gun design

Unread postAuthor: gpopovic » Mon Jun 15, 2015 3:14 am

Overkill is not a problem :) 5.5 is cheap and readily available, and I would primarily use it for plinking. 10x2mm that I can get is supposed to be ID6mm, but it never is, it's closer to 5 really, so I enlarge it a bit. and its just right for 5,5mm.
These tubes are rated to 9bar I think, ~130+ psi.

BTW, what's your wall thickness on the inner tube? I planned this with both wall thicknesses 2mm.

On the other side, I epoxied the reservoire as planned, and should machine the action on the pcp a little to allow better access for the fingers when placing the pellet, hopefully tomorrow. Will make some pics if I manage.
  • 0

User avatar
gpopovic
Private
Private
 
Posts: 20
Joined: Sun May 03, 2015 2:46 am
Location: Belgrade
Country: Serbia (rs)
Reputation: 1

Re: Need opinions/advice on a bb gun design

Unread postAuthor: Brian the brain » Mon Jun 15, 2015 1:20 pm

Barrel walls are just 1.1 mm,copper, the walls of the outer tube however are 3- and then some-mm seamless steel..
  • 0

Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
User avatar
Brian the brain
Moderator
Moderator
 
Posts: 3494
Joined: Mon Dec 05, 2005 2:06 am
Location: Holland
Country: Netherlands (nl)
Reputation: 29

Re: Need opinions/advice on a bb gun design

Unread postAuthor: gpopovic » Tue Jun 16, 2015 4:27 pm

I guess my 22x2 with car compressor would be quite OK then.
Got my bandsaw back in the working order with some nice new bands, 6mm wide, supposed to cut even mild steel, but I don't suppose I'll try that ;)
Looking around the shop and some pieces of cherry look suspiciously like a RB stock, we'll see...
  • 0

User avatar
gpopovic
Private
Private
 
Posts: 20
Joined: Sun May 03, 2015 2:46 am
Location: Belgrade
Country: Serbia (rs)
Reputation: 1

Re: Need opinions/advice on a bb gun design

Unread postAuthor: gpopovic » Fri Jun 19, 2015 3:18 am

Some more work done on the receiver, drilled the port from the bottom, and I am toying with the idea of it's plug being also a screw that's holding it to the stock. It would be hidden under the guard probably.

Imagepcp montaza2 by Goran P, on Flickr

When I start a new project from the scratch, I'll make a separate thread, I think this is OK for now?

BTW, I got asked to replicate a broken stock for a really old russian breakbarrel, side-by-side. It's still in one piece, but with a few nasty cracks and a poor attempt of a repair. I can fix it, but he'll probably prefere a brand new one, perhaps with some twists of his own. I'll repair the original anyway, and it will hang nicely on my shop wall if he doesn't want it :)
  • 0

User avatar
gpopovic
Private
Private
 
Posts: 20
Joined: Sun May 03, 2015 2:46 am
Location: Belgrade
Country: Serbia (rs)
Reputation: 1

Previous

Return to BB/Airsoft/Pellet Gun Discussion

Who is online

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

Reputation System ©'