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 54 users online :: 4 registered, 0 hidden and 50 guests


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

Registered users: Bing [Bot], Exabot [Bot], Google [Bot], Majestic-12 [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

preloaded pneumatic cartridge

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

Re: preloaded pneumatic cartridge

Unread postAuthor: hectmarr » Wed Nov 15, 2017 9:55 pm

A question. What is the advantage over a pre-compressed air gun with a camera, a PCP, of this system of cartridges?
The smaller size of the weapon when there is no air tank? Is the pressure you use greater?
  • 0

When I had nothing, I did a lot. Now that I have everything, I do not do anything. Damned karma
User avatar
hectmarr
Major
Major
 
Posts: 399
Joined: Sat May 07, 2016 3:49 pm
Location: San Miguel de Tucumán
Country: Argentina (ar)
Reputation: 64

Re: preloaded pneumatic cartridge

Unread postAuthor: jackssmirkingrevenge » Thu Nov 16, 2017 6:32 am

One of the greatest personal incentives to me is having a mechanism that replicates that of a firearm, long time members will tell you of my fascination with shell ejection :) Some other practical advantages include the possibility of a repeater with irregular projectiles (such as a shotgun), having the leak-prone pressurized mechanism restricted to an easily replaceable cartridge as well as the opportunity to create a variety of different cartridges that can all be fired from the same launcher.

In the meantime I've crunched some numbers and figured some practical mechanics, here's what a high pressure exhaust valve cartridge wold look like for a 3/8" ball bearing, 0.75" diameter and 3" long making it roughly the size of a shotgun shell.

Image

The front end is permanently pinned in place while the rear is removable for maintenance purposes. The piston is machined from a single piece of delrin, and I envisage filling being done through the mouth of the cartridge via an appropriate fill rig. Not shown is a groove or rim for extraction purposes, I'm still debating if this will be necessary - technically it would be easier to extract a shell that for whatever reason didn't fire, but the same can be accomplished by pulling the bolt back and letting it fall out by gravity - not exactly elegant engineering, hmmm...
  • 0

hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 25079
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 136

Re: preloaded pneumatic cartridge

Unread postAuthor: hectmarr » Thu Nov 16, 2017 6:57 am

A question. When it is fired, the oring comes out of its housing, where is the spring, escaping the air of the pilot there?
  • 0

When I had nothing, I did a lot. Now that I have everything, I do not do anything. Damned karma
User avatar
hectmarr
Major
Major
 
Posts: 399
Joined: Sat May 07, 2016 3:49 pm
Location: San Miguel de Tucumán
Country: Argentina (ar)
Reputation: 64

Re: preloaded pneumatic cartridge

Unread postAuthor: jackssmirkingrevenge » Thu Nov 16, 2017 7:12 am

This is how I envisage the firing stem, with a flat machined in it to allow air to flow past the o-ring:

Image
  • 0

hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 25079
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 136

Re: preloaded pneumatic cartridge

Unread postAuthor: hectmarr » Thu Nov 16, 2017 8:01 am

Is that so? If you do not correct me ...
  • 0

Attachments
S7ncL2u.png
S7ncL2u.png (14.09 KiB) Viewed 753 times
When I had nothing, I did a lot. Now that I have everything, I do not do anything. Damned karma
User avatar
hectmarr
Major
Major
 
Posts: 399
Joined: Sat May 07, 2016 3:49 pm
Location: San Miguel de Tucumán
Country: Argentina (ar)
Reputation: 64

Re: preloaded pneumatic cartridge

Unread postAuthor: jackssmirkingrevenge » Thu Nov 16, 2017 8:17 am

More like this, the stem is not airtight at its widest diameter so it should leak with minimal movement:

Image

I also envisage the spring being very weak so as not to encourage the stem to re-close as the piston recoils.
  • 1

hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 25079
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 136

Re: preloaded pneumatic cartridge

Unread postAuthor: hectmarr » Thu Nov 16, 2017 9:14 am

Ok now I understand well. Good design in my humble opinion of neophyte. Thanks for the clarification.
  • 0

When I had nothing, I did a lot. Now that I have everything, I do not do anything. Damned karma
User avatar
hectmarr
Major
Major
 
Posts: 399
Joined: Sat May 07, 2016 3:49 pm
Location: San Miguel de Tucumán
Country: Argentina (ar)
Reputation: 64

Re: preloaded pneumatic cartridge

Sponsored

Sponsor
 


Re: preloaded pneumatic cartridge

Unread postAuthor: jackssmirkingrevenge » Wed Nov 29, 2017 7:40 am

More practical musings, perhaps a mechanical lock is a better idea.

Image
  • 0

hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 25079
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 136

Re: preloaded pneumatic cartridge

Unread postAuthor: hectmarr » Wed Nov 29, 2017 10:06 am

It seems a little more complicated, without this being a problem.
Question: What material is indicated by the red arrow?
What are the advantages compared to the previous design?


Note:
There is NOTHING to replace your practice of having seen thousands of these mechanisms .... :|
  • 0

Attachments
T60shnS.png
When I had nothing, I did a lot. Now that I have everything, I do not do anything. Damned karma
User avatar
hectmarr
Major
Major
 
Posts: 399
Joined: Sat May 07, 2016 3:49 pm
Location: San Miguel de Tucumán
Country: Argentina (ar)
Reputation: 64

Re: preloaded pneumatic cartridge

Unread postAuthor: jackssmirkingrevenge » Wed Nov 29, 2017 11:02 am

Question: What material is indicated by the red arrow?


Those are steel balls, the function is like an airsoft grenade:

Image

They hold the piston in place in the same way that a quick-connect fitting works:

Image

What are the advantages compared to the previous design?


No air is wasted for piloting, and piston release is instant, there is no pilot chamber emptying that will slow the piston down. It's a little more complex to make, but also more reliable and in theory faster opening. If the difference in diameter between from and rear o-rings on the piston is small, the force needed to actuate it will also be minimal.
  • 1

hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 25079
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 136

Re: preloaded pneumatic cartridge

Unread postAuthor: hectmarr » Wed Nov 29, 2017 3:31 pm

The fact that it opens faster is important. I like it. :bounce:
  • 0

When I had nothing, I did a lot. Now that I have everything, I do not do anything. Damned karma
User avatar
hectmarr
Major
Major
 
Posts: 399
Joined: Sat May 07, 2016 3:49 pm
Location: San Miguel de Tucumán
Country: Argentina (ar)
Reputation: 64

Re: preloaded pneumatic cartridge

Unread postAuthor: hectmarr » Fri Dec 15, 2017 8:35 pm

Hi Jack :) How is the construction of the preloaded air cartridge? Could you advance something on this topic?
  • 0

When I had nothing, I did a lot. Now that I have everything, I do not do anything. Damned karma
User avatar
hectmarr
Major
Major
 
Posts: 399
Joined: Sat May 07, 2016 3:49 pm
Location: San Miguel de Tucumán
Country: Argentina (ar)
Reputation: 64

Re: preloaded pneumatic cartridge

Unread postAuthor: jackssmirkingrevenge » Sat Dec 16, 2017 5:20 am

I've been distracted by other projects :)

I current have a box of parts that used to be one of these that I would like to turn into something like this:

Image
  • 0

hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 25079
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 136

Re: preloaded pneumatic cartridge

Unread postAuthor: hectmarr » Sat Dec 16, 2017 6:15 am

It looks interesting. The line of this weapon is very pleasing to the eye.
On the other hand, I've been doing nothing until. These days I will resume the tests.
  • 0

When I had nothing, I did a lot. Now that I have everything, I do not do anything. Damned karma
User avatar
hectmarr
Major
Major
 
Posts: 399
Joined: Sat May 07, 2016 3:49 pm
Location: San Miguel de Tucumán
Country: Argentina (ar)
Reputation: 64

Re: preloaded pneumatic cartridge

Unread postAuthor: jackssmirkingrevenge » Wed Jan 03, 2018 6:21 am

In conjunction with a nice rifled big bore barrel and a Crosman 2240 grip, I think something like this is looking feasible:

Image

Single shot and perhaps with enough force to blow the cartridge back and eject it.

With a good bit of force behind the bolt I think I could go with a spool design:

Image

GGDT suggests performance within my expectations at 3000 psi:

Image

Even with the pressure balanced, there will still be a substantial amount of friction on the o-rings, I wonder if it would be worth unbalancing the spool slightly with a bias towards opening.
  • 0

hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 25079
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 136

PreviousNext

Return to Pneumatic Cannon Discussion

Who is online

Registered users: Bing [Bot], Exabot [Bot], Google [Bot], Majestic-12 [Bot]

Reputation System ©'