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 80 users online :: 4 registered, 0 hidden and 76 guests


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

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

high velocity burst disc 6mm pneumatic

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

Unread postAuthor: jackssmirkingrevenge » Sat Sep 08, 2007 1:07 pm

Here it is in pure pneumatic configuration and somewhat finished, the epoxy is more or less cured but I'm giving it at least another 24 hours before further testing.
  • 0

Attachments
6mmburstdiskbreech.JPG
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: DYI » Sat Sep 08, 2007 7:12 pm

You're not going to get much higher velocities than you already are anyway. Don't you just hate the speed of sound problem?

What kind of damage can it do with a .12 gram?
  • 0

User avatar
DYI
Lieutenant General
Lieutenant General
 
Posts: 2861
Joined: Sat Jul 07, 2007 8:18 pm
Location: The People's Republic of Canuckistan
Country: Turks and Caicos Islands (tc)
Reputation: 9

Unread postAuthor: jon_89 » Sat Sep 08, 2007 7:35 pm

very nice. how loud is it?
  • 0


jon_89
Colonel
Colonel
 
Posts: 607
Joined: Wed Apr 11, 2007 9:50 pm
Reputation: 0

Unread postAuthor: PVC Arsenal 17 » Sun Sep 09, 2007 12:58 am

Nice gun jack. I pondered the same thing earlier today. Think you could break the sound barrier?
  • 0


PVC Arsenal 17
Major General
Major General
 
Posts: 1762
Joined: Mon Mar 27, 2006 4:18 pm
Location: United States
Reputation: 1

Unread postAuthor: rna_duelers » Sun Sep 09, 2007 3:04 am

Nice velocities,only 12 FPS off the sound barrier(Sea Level)if I remember correct.There is no reason why you couldn't break the sound barrier,but could you be getting incorrect results from having the chrono to close the the muzzle?I did that with one of my pneumatics and I thought I broke the sound barrier but I was really about 200 FPS shy.
  • 0

Image
User avatar
rna_duelers
Major General
Major General
 
Posts: 1740
Joined: Mon Sep 26, 2005 7:07 am
Location: G-land Australia
Country: Australia (au)
Reputation: 1

Unread postAuthor: DYI » Sun Sep 09, 2007 9:14 am

The reason that he couldn't break the sound barrier is because he is using room temperature air. Unheated air will not push a projectile past the speed of sound under normal circumstances.
  • 0

Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.
User avatar
DYI
Lieutenant General
Lieutenant General
 
Posts: 2861
Joined: Sat Jul 07, 2007 8:18 pm
Location: The People's Republic of Canuckistan
Country: Turks and Caicos Islands (tc)
Reputation: 9

Unread postAuthor: joannaardway » Sun Sep 09, 2007 9:37 am

DYI wrote:The reason that he couldn't break the sound barrier is because he is using room temperature air. Unheated air will not push a projectile past the speed of sound under normal circumstances.

Not necessarily. As it's being pumped in, the temperature will have risen quite a bit.

It's also not impossible to achieve supersonic air currents in a smooth enough barrel. If the pressure differential at the valve is high enough, and the projectile is really light, the supersonic air currents generated at the valve could continue down the barrel. And if your airflow is supersonic, you can get a projectile to go supersonic.

Take something like this MTU.
That uses supersonic airflows to generate vacuums. (Actually, that 6.3mm version might be useful to enhance a BBMG...)

With that C:B ratio, the smoothbore brass barrel, a burst disk and 400 psi of air at above room temp, it's far from impossible.
  • 0

Novacastrian: How about use whatever the heck you can get your hands on?
frankrede: Well then I guess it won't matter when you decide to drink bleach because your out of kool-aid.
...I'm sorry, but that made my year.
User avatar
joannaardway
Brigadier General
Brigadier General
 
Posts: 949
Joined: Mon Oct 09, 2006 4:57 pm
Location: SW Hertfordshire, England, UK.
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: jackssmirkingrevenge » Sun Sep 09, 2007 9:55 am

What kind of damage can it do with a .12 gram?


I certainly wouldn't want to be hit by one, here's some 0.25 gram BB tests:


[youtube]http://www.youtube.com/watch?v=lMWNpiaPha8[/youtube]

0.25g BB at 1017 fps straight through a steel (empty!) lighter fluid can

[youtube]http://www.youtube.com/watch?v=t0OnQZvvR7g[/youtube]

0.12g BB at the same can, only penetrated one side. Sadly the chrony didn't get a reading.

[youtube]http://www.youtube.com/watch?v=jiw_r_IxSEE[/youtube]

0.25g BB at 982 fps straight through a plastic toy container

very nice. how loud is it?


Actually not that loud, thanks to the approximately 1:1 chamber/barrel ratio and long barrel.

could you be getting incorrect results from having the chrono to close the the muzzle


That's the way this particular chrony is meant to be used, and as I've said I've compared it to other chronies at high velocities and got consistent results.

The reason that he couldn't break the sound barrier is because he is using room temperature air. Unheated air will not push a projectile past the speed of sound under normal circumstances.


Not so, commercially available air rifles like the Airforce Condor can break the sound barrier using unheated air and a hammer valve.
  • 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: DYI » Sun Sep 09, 2007 10:50 am

I don't think it is impossible to push a projectile pass the speed of sound with air pressure, it is just difficult. I will be trying it soon, and hopefully I can make it happen.

Those are some great videos Jack, but what happened to the sound?
  • 0

Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.
User avatar
DYI
Lieutenant General
Lieutenant General
 
Posts: 2861
Joined: Sat Jul 07, 2007 8:18 pm
Location: The People's Republic of Canuckistan
Country: Turks and Caicos Islands (tc)
Reputation: 9

Unread postAuthor: jackssmirkingrevenge » Sun Sep 09, 2007 11:32 am

No sound unfortunately, 3 digital cameras in this house and none of them have a microphone :?

I tried a Diabolo Baracuda extra heavy 31 grain 0.25 pellet (6.35 mm, needs to be rolled down a little to fit the barrel) and got 577 feet per second, an impressive 23 foot pounds :D

Sadly I still can't get a velocity reading for the 0.12 gram BB, the chrony keeps saying "bad" :?
  • 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: joannaardway » Sun Sep 09, 2007 5:29 pm

Impressive energy figures for something so small. Considering how that stacks up at about 20% of the .22 LR round, I'm damn impressed.
Yeah, I know the .22 LR is pretty wimpy, but I still wouldn't want to get hit with it.

Any idea why the chrony is objecting to the .12g?
  • 0

Novacastrian: How about use whatever the heck you can get your hands on?
frankrede: Well then I guess it won't matter when you decide to drink bleach because your out of kool-aid.
...I'm sorry, but that made my year.
User avatar
joannaardway
Brigadier General
Brigadier General
 
Posts: 949
Joined: Mon Oct 09, 2006 4:57 pm
Location: SW Hertfordshire, England, UK.
Reputation: 0

Unread postAuthor: Fnord » Sun Sep 09, 2007 5:47 pm

It's also not impossible to achieve supersonic air currents in a smooth enough barrel. If the pressure differential at the valve is high enough, and the projectile is really light, the supersonic air currents generated at the valve could continue down the barrel. And if your airflow is supersonic, you can get a projectile to go supersonic.


Has anyone ever tried drawing a vaccuum in the barrel to increase the initial pressure difference? A thin burst disk on the end would be used to seal it before the projectile hits.
A better question is, how much difference would it make?

(Oh, and nice Plinker from Hell)
  • 0

Image
User avatar
Fnord
Major General
Major General
 
Posts: 2244
Joined: Tue Feb 13, 2007 9:20 pm
Location: Pripyat
Reputation: 7

Unread postAuthor: Novacastrian » Sun Sep 09, 2007 9:15 pm

You would of nailed mach 2 in Hybrid form (jokes).
Well done with those velocities, the lighter bb that the chrony can't read must be going super-sonic :twisted:
Let us know when you get bored and turn it into a hybrid 8)
Nice work.
  • 0


Novacastrian
Major General
Major General
 
Posts: 1604
Joined: Sat Aug 11, 2007 6:59 pm
Reputation: 0

Unread postAuthor: Lentamentalisk » Sun Sep 09, 2007 10:09 pm

how are you using tape as a burst disk? can you demonstrate in any way?
  • 0

User avatar
Lentamentalisk
Brigadier General
Brigadier General
 
Posts: 1202
Joined: Tue Aug 07, 2007 5:27 pm
Location: Berkeley C.A.
Reputation: 0

Unread postAuthor: frankrede » Sun Sep 09, 2007 10:25 pm

Have you tried using PBA Raptor pellets? 25% increase in velocity
  • 0

Current project: Afghanistan deployment
User avatar
frankrede
Lieutenant General
Lieutenant General
 
Posts: 3220
Joined: Thu Jul 20, 2006 9:47 pm
Reputation: 0

PreviousNext

Return to Pneumatic Cannon Database

Who is online

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

Reputation System ©'