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 71 users online :: 3 registered, 0 hidden and 68 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

valveless pellet gun

Built a miniature cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
Sponsored 
  • Author
    Message

valveless pellet gun

Unread postAuthor: jackssmirkingrevenge » Thu Jun 21, 2007 11:19 pm

This is an idea I had a while back, which was to dispense with the valve altogether and use the projectile to seal the air chamber, locked in place until it was ready to fire. This would be to all intents and purposes the most effective "valve" happy red? :p I could think of.

The prototype I actually made had a bolt as a projectile stopper and used 0.22 airgun pellets which gave a good seal on the barrel. The performance however wasn't any better than my mini-piston designs so I shelved the idea as not offering sufficient benefits to warrant the awkward method of operation.

The disadvantage is that you need a projectile that's a 100% airtight fit in the breech, which also has to be of strong enough construction to retain the pressure behind it without collapsing. Still, for those seeking ultimate performance, it might be a workable idea.

For more detailed information on using epoxy, check out the how-tos here and here.
  • 0

Attachments
valvelessbb.JPG
concept drawing with a sliding lock
valvelessbb.JPG (30.76 KiB) Viewed 2291 times
valvelessclose.JPG
breech concept closeup
valvelessclose.JPG (26.43 KiB) Viewed 2275 times
valveless breech.JPG
prototype breech construction
valveless breech.JPG (33.73 KiB) Viewed 2275 times
valveless.JPG
valveless strafer concept
valveless.JPG (27.2 KiB) Viewed 2275 times
512443.jpg
views of the actual prototype, from top to bottom:

1)rear view of breech and barrel assembly
2)view down the barrel, you can make out the end of the bolt sticking out - note that it only has to enter the barrel a tiny amount to jam the projectile in place.
3)breech threaded to a blowgun for low pressure testing
4)High pressure chamber for 300 psi+ testing.
Last edited by jackssmirkingrevenge on Sun Sep 09, 2007 12:04 pm, edited 4 times in total.
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: Redcoat » Thu Jun 21, 2007 11:24 pm

bravo jack, your ideas keep on comng and there always good.I never would have thought of that.That is a good idea maybe for a sniper?

A one shot pistol is pretty annoying (in my books).
  • 0

Poo.
User avatar
Redcoat
Brigadier General
Brigadier General
 
Posts: 836
Joined: Tue Feb 13, 2007 1:07 am
Location: Sydney ,Australia
Reputation: 0

Unread postAuthor: rednecktatertosser » Thu Jun 21, 2007 11:25 pm

So a valveless gun with the most effective valve you could think of? That made me laugh.

But in all seriousness that is a really good idea. I might just make one this weekend... Providing I find money.
  • 0

User avatar
rednecktatertosser
Colonel
Colonel
 
Posts: 590
Joined: Tue May 22, 2007 7:52 pm
Reputation: 0

Unread postAuthor: noname » Thu Jun 21, 2007 11:26 pm

Knowing you and your epoxy skillz, I think you could make it. Good luck. What kind of projectiles do you have in mind, seeing as they need to seal?
  • 0

User avatar
noname
Lieutenant General
Lieutenant General
 
Posts: 2699
Joined: Mon Apr 10, 2006 9:19 pm
Location: Bay Area, CA
Country: United States (us)
Reputation: 9

Unread postAuthor: hi » Thu Jun 21, 2007 11:26 pm

i think you would have to pull the trigger fairly fast, but it should work, if you can ge it to seal.
  • 0

"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
User avatar
hi
Major General
Major General
 
Posts: 1619
Joined: Thu Feb 01, 2007 9:28 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Thu Jun 21, 2007 11:37 pm

sorry guys but I pressed the "submit" button too early (d'oh!) I actually made a prototype of this, check the edited post :)
  • 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: Velocity » Thu Jun 21, 2007 11:39 pm

Its like a burst disk on steroids! (not really?)

Nice design here... I am surprised that you were able to get it to seal.

It would be interesting to compare this to a burst disk gun of similar size.
  • 0

User avatar
Velocity
Brigadier General
Brigadier General
 
Posts: 1039
Joined: Tue Feb 07, 2006 5:42 pm
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: rednecktatertosser » Thu Jun 21, 2007 11:40 pm

well another one of your wonderful innovations has been put into my "stuff to build" file in my favorites. once again good job jack, like usual.
  • 0

User avatar
rednecktatertosser
Colonel
Colonel
 
Posts: 590
Joined: Tue May 22, 2007 7:52 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Thu Jun 21, 2007 11:40 pm

rmich732 wrote:Nice design here... I am surprised that you were able to get it to seal.


It sealed easily without any rubber because the soft lead skirt of the pellet "inflates" and seals agaisnt the barrel. This is after all the same way that brass cartridges seal the propellant casses inside firearms.
  • 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: rednecktatertosser » Thu Jun 21, 2007 11:44 pm

AH so it works off the pricipal of grease seals on a car axle, where its cupped to one side, the side it seals so that it helps hold pressure. thats ingenious.
  • 0

User avatar
rednecktatertosser
Colonel
Colonel
 
Posts: 590
Joined: Tue May 22, 2007 7:52 pm
Reputation: 0

Unread postAuthor: shud_b_rite » Fri Jun 22, 2007 1:36 am

I like your chamber. Where did you get it? Or how did you make it?
  • 0

Airbeds... so many different uses
User avatar
shud_b_rite
1st Lieutenant
1st Lieutenant
 
Posts: 290
Joined: Tue Jan 30, 2007 7:10 pm
Location: Auckland, New Zealand
Reputation: 0

Unread postAuthor: FreakyShotGlass » Fri Jun 22, 2007 1:51 am

You could use a solenoid to hold back the projectile and then apply a current and the solenoid would activate and release the projectile.
  • 0

User avatar
FreakyShotGlass
Staff Sergeant
Staff Sergeant
 
Posts: 114
Joined: Fri Dec 02, 2005 6:34 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Fri Jun 22, 2007 2:16 am

shud_b_rite wrote:I like your chamber. Where did you get it? Or how did you make it?


I made it myself, as per attached diagram.

You could use a solenoid to hold back the projectile and then apply a current and the solenoid would activate and release the projectile.


You'll need a pretty hefty solenoid to achieve that, for a 3/4" barrel at 100 psi it'll have to hold a force of 44 lbs.
  • 0

Attachments
untitled.jpg
chamber diagram
untitled.jpg (18.44 KiB) Viewed 2243 times
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: potatoflinger » Fri Jun 22, 2007 8:11 am

That's a great idea, but wouldn't the pellets wear down the barrel after a while, since they expand to fit the barrel perfectly? It seems like they would scrape the sides the whole way down the barrel.
  • 0

User avatar
potatoflinger
Brigadier General
Brigadier General
 
Posts: 1136
Joined: Thu Nov 02, 2006 3:26 pm
Location: Maryland
Reputation: 1

Unread postAuthor: lukemc » Fri Jun 22, 2007 8:34 am

jackssmirkingrevenge wrote:
You could use a solenoid to hold back the projectile and then apply a current and the solenoid would activate and release the projectile.


You'll need a pretty hefty solenoid to achieve that, for a 3/4" barrel at 100 psi it'll have to hold a force of 44 lbs.


what if you made it like this the solenoid wouldnt have to direcly hold back the pressure
Image
  • 0

Last edited by lukemc on Fri Jun 22, 2007 8:35 am, edited 1 time in total.
"Those who are different change the world. Those who are the same keep it that way"
User avatar
lukemc
Colonel
Colonel
 
Posts: 565
Joined: Sun Feb 25, 2007 8:48 am
Location: NY
Reputation: 0

Next

Return to Miniature Cannon Database

Who is online

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

Reputation System ©'