| Author |
Message
|
| hyperspaz |
 Posted: 02/26/2010 19:13 PM Post subject: Frictionless barrel idea |
 |
|
Private
Joined: 26 Feb 2010
Posts: 17
62.02 Spud Bux
|
Hi guys,
I have this idea of making a frictionless barrel, but I'm unsure if it will work, or if it will even make a difference. My idea consists of a barrel with a bunch of small, evenly spaced holes in it; surrounded by another tube, that would supply air to those holes in the barrel. Which, in turn, should make the projectile float, as it travels through the barrel. It's basically the same principle as an air hockey table.
Please, let me know what you think. Thanks!
| Description: |
| Sorry for the horrible schematic, I was in a hurry when I made it.. This isn't exactly how I would make the cannon, its just to help you better understand my idea, and how it might work. |
|
| Filesize: |
33.21 KB |
| Viewed: |
748 Time(s) |
|
|
|
| Back to top |
|
 |
|
|
|
| Hubb |
| Posted: 02/26/2010 19:17 PM Post subject: |
|
|
Major General
Joined: 28 May 2007
Posts: 2410
701.43 Spud Bux
|
| That's almost inline with a ram accelerator (if you know what that is) except for pneumatics. If there were a way to trigger the secondary valve for the barrel as the projectile passed a certain point, it may work. I'm interested to see this go past the design stage and how much, if at all, it increases performance.
|
|
| Back to top |
|
|
| Hawkeye |
| Posted: 02/26/2010 19:29 PM Post subject: |
|
|
Lieutenant Colonel
Joined: 21 Jan 2007
Posts: 464
1237.72 Spud Bux
|
| It's still going to have air blasting into the barrel. I can envision the projectile being hit by such turbulence that it would be lucky to clear the barrel.
|
|
| Back to top |
|
|
| Lockednloaded |
| Posted: 02/26/2010 20:07 PM Post subject: |
|
|
El Moderador
Joined: 03 Sep 2009
Posts: 1345
376.81 Spud Bux
|
I don't understand how this works, but i think i can help simplify the design. Instead of two chambers and two pistons, why don't you just use the pilot of one piston to go to your barrel shroud thing. If this is not enough air, you could increse the pilot volume (jsr's gonna hate that  ) and use a huge pilot valve. These should help make it much simpler to build
~lnl~
|
|
| Back to top |
|
|
| inonickname |
| Posted: 02/26/2010 20:57 PM Post subject: |
|
|
Major General
Joined: 07 Dec 2008
Posts: 2487
6556.71 Spud Bux
|
If the force on either side is balanced then the weight of the projectile will still cause friction on the bottom of the barrel. It needs to be so that it can barely hold the projectile off the barrel.
It's fairly likely to hurt performance though.
|
|
| Back to top |
|
|
| Brian the brain |
| Posted: 02/27/2010 11:47 AM Post subject: |
|
|
Dutch Spud Clan Leader
Joined: 05 Dec 2005
Posts: 2763
6458.86 Spud Bux
|
The idea is completely ridiculous...
I love it hahaha
But I'm fairly positive of negative results
If you where to launch a ringshaped piston through the barrel schroud simultaniously you might be able to ...well...have it suck less I guess..
WTH?? I'm trying to improove on a no chance design..
Think about this..what's the difference between this design and using slightly undersized ammo??
|
|
| Back to top |
|
|
| jackssmirkingrevenge |
| Posted: 02/27/2010 11:58 AM Post subject: |
|
|
aspiring machinist
Joined: 15 Mar 2007
Posts: 18058
32513.12 Spud Bux
|
Interesting concept but flawed, there already is a thin cushion of air between the barrel and the projectile when you fire it anyway (assuming your projectile hasn't got o-rings fitted), performance gain is highly unlikely and even if there is some it would be insignificant. You're better off dedicating all that extra valving to making a semi-auto mechanism 
|
|
| Back to top |
|
|
| jimmy101 |
| Posted: 02/27/2010 16:19 PM Post subject: |
|
|
Lieutenant General
Joined: 28 Mar 2007
Posts: 2866
11974.95 Spud Bux
|
Like Jack said. A loosely fitting ammo will pretty nearly be floating on a thin layer of blow by anyway and that's a lot easier to do than is plumbing in an extra air supply via a bunch of holes.
In addition, many guns designs (both pneumatic and combustion) benefit from a bit of friction. If not from the friction then often just the lack of blow by adds enough power that that is more important than friction.
HGDT or GGDT will let you estimate how much friction actually hurts (or helps) performance. I suspect you'll find that friction that either (1) it doesn't make much difference and can be offset with a slightly larger chamber or that (2) friction actually increases performance a bit.
(Combustion guns typically work much better with a fair amount of friction.)
|
|
| Back to top |
|
|
| Brian the brain |
| Posted: 02/27/2010 16:23 PM Post subject: |
|
|
Dutch Spud Clan Leader
Joined: 05 Dec 2005
Posts: 2763
6458.86 Spud Bux
|
Friction allows for pressure buildup..
True.
|
|
| Back to top |
|
|
| inonickname |
| Posted: 02/27/2010 17:31 PM Post subject: |
|
|
Major General
Joined: 07 Dec 2008
Posts: 2487
6556.71 Spud Bux
|
| Good point with the pressure buildup. If you want less resistance in your barrel, draw a vacuum in it. Vacuum alone can propel a ping-pong ball to near the speed of sound.
|
|
| Back to top |
|
|
| jimmy101 |
| Posted: 02/27/2010 19:14 PM Post subject: |
|
|
Lieutenant General
Joined: 28 Mar 2007
Posts: 2866
11974.95 Spud Bux
|
| inonickname wrote: | | Vacuum alone can propel a ping-pong ball to near the speed of sound. |
Only if by "vacuum alone" you mean the gun itself was already moving at Mach 0.5 or so.
|
|
| Back to top |
|
|
| Lentamentalisk |
| Posted: 02/27/2010 19:16 PM Post subject: |
|
|
Resident Tinkerer
Joined: 07 Aug 2007
Posts: 1202
2200.81 Spud Bux
|
inonickname: "Vacuum alone" can accelerate anything to the speed of sound (actually to the speed of the fastest moving particles) it just takes a damn long time and zero friction. Assuming, of course, that both sides aren't vacuumed.
Its called unbalanced forces. They cause acceleration. End of story.
|
|
| Back to top |
|
|
| inonickname |
| Posted: 02/27/2010 19:28 PM Post subject: |
|
|
Major General
Joined: 07 Dec 2008
Posts: 2487
6556.71 Spud Bux
|
| Lentamentalisk wrote: | inonickname: "Vacuum alone" can accelerate anything to the speed of sound (actually to the speed of the fastest moving particles) it just takes a damn long time and zero friction. Assuming, of course, that both sides aren't vacuumed.
Its called unbalanced forces. They cause acceleration. End of story. |
Indeed, but I meant in practicality for the average spudder (not many of us are building particle accelerators). Zero friction, perfect fit and perfect vacuum is essentially out of our reach.
|
|
| Back to top |
|
|
| Ragnarok |
| Posted: 02/27/2010 19:37 PM Post subject: |
|
|
Lord of Karma
Joined: 19 Dec 2006
Posts: 5158
16113.53 Spud Bux
|
I'm a little surprised that the flaw in having a barrel with holes in it hasn't been mentioned.
As far as friction, it's largely irrelevant in a spudgun barrel - the equivalent of a couple of dozen kPa compared to numbers of several hundred or even thousands. If you're that fussed, my suggestion is to get a PTFE spray, squirt it down the barrel and that should reduce friction just fine.
I do have a project with a frictionless barrel (and indeed, frictionless "rifling"), but it's electromagnetic, not pneumatic.
|
|
| Back to top |
|
|
| Hawkeye |
| Posted: 02/27/2010 20:31 PM Post subject: |
|
|
Lieutenant Colonel
Joined: 21 Jan 2007
Posts: 464
1237.72 Spud Bux
|
| Better to use the second piston to work a gas ram that operates a loader.
|
|
| Back to top |
|
|
|
|
