Search    Main Website    Parts Store    Forum    FAQ    Login

Board index » Archive » Old Spudtech Message Board » Pneumatic Launchers




Forum locked This topic is locked, you cannot edit posts or make further replies.  [ 13 posts ]  Go to page 1, 2  Next
Author Message
 Post Posted: Sun Jul 27, 2003 5:00 pm 
Offline
Site Admin

Joined: Sun Feb 12, 2012 1:19 am
Posts: 10742
Originaly posted by GisMo,

My hypothesis is that a 1" Ball Valve, when operated consistantly and quickly enough, it will perform better than a 1" sprinkler solenoid valve. I reasoning: A ball vavle is straight through. It is not Channeled and forced between a tight space when the diaphragm opens. Also, as the pressure is being relieved, the diaphragm lowers and the space the air is coming from gets smaller. The ball valve is a static 1". I feel that the sprinkler vavles are more popular because it is "automatic", looks "cooler", and is extremely consistent, hence, people think it works better.

Comments? Additions? Rebuttles?





Also, when I modified a sprinker vavle I had with the blowgun and hose coming from the top....The vavle didn't work well at all! about 1/2 of the pressure was relieved from the blowgun and the other half from the outlet. Anyone know why? its just like all the other blowgun valves modded ones.



Top 
 Profile  
 
 Post subject: intresting...
 Post Posted: Sun Jul 27, 2003 5:00 pm 
Offline
Site Admin

Joined: Sun Feb 12, 2012 1:19 am
Posts: 10742
Originaly posted by someguynamedchris,
you are right about the flow but the speed in witch a pneumaticly operatd sprinkler valve opeans is mutch faster. I have a 3/4" ball and a pneumaticly operatd sprinkler valve. With the same barrel and chamber the sprinkler valve is better.
But what you say could be true if the ball valve would opean really fast but that could be hard to do. Sure to be a real chalange.

Chris


Top 
 Profile  
 
 Post subject: but...
 Post Posted: Sun Jul 27, 2003 5:00 pm 
Offline
Site Admin

Joined: Sun Feb 12, 2012 1:19 am
Posts: 10742
Originaly posted by perkulator,
When the diaphragm lowers did the projectile left the barrel a looooong time ago!
If you think about it it doesn´t take much force to open the diaphragm.
(I don´t have a spring or anything to close the diaphragm with by the way,it seals ok anyway.)


Top 
 Profile  
 
 Post Posted: Sun Jul 27, 2003 5:00 pm 
Offline
Site Admin

Joined: Sun Feb 12, 2012 1:19 am
Posts: 10742
Originaly posted by mta,
How quick is quick enough? In any decent pneumatic with a reasonable barrel length (<20 feet) the projectile is out of the barrel in a twentieth of a second or less. How are you going to open a ball valve that quickly? If it doesn't fully open till the spud is almost out the barrel it won't matter much if it has a slightly better flow coefficient than a sprinkler valve. Speed matters.


Top 
 Profile  
 
 Post Posted: Sun Jul 27, 2003 6:00 pm 
Offline
Site Admin

Joined: Sun Feb 12, 2012 1:19 am
Posts: 10742
Originaly posted by Namor,
to actuate a ball valve faster than a sprinkler, then I think ball valves would be way better...

thats the main reason sprinkler valves are better, because of the speed of actuation


Top 
 Profile  
 
 Post subject: What you need...
 Post Posted: Mon Jul 28, 2003 3:00 am 
Offline
Site Admin

Joined: Sun Feb 12, 2012 1:19 am
Posts: 10742
Originaly posted by GalFisk,
...should actually be a way to keep the valve closed by some object until it's fully open, something that is pressed against the ball and cannot pass through the valve until the opening is perfectly round. I don't know about the actual design of such a device, but if you can create something that will pop out quickly enough, be that some sort of piston, a rubber ball, the ammo itself or something different, you should have a pretty fast valve.
I just got an idea for a piston design while typing: after the ball valve, instead of a 90 bend, you put in a T coupling. The ball valve goes at one end of the T, the barrel goes to the leg of the T, and a short piece of pipe, with a cap and venting holes, and maybe a good spring in the cap, goes on the other end of the T. Now the piston, which needs to be airtight, and very lightweight not to blow off the endcap, goes on the other side of the ball valve. The valve can be slightly open to ensure that the pressure pushes the piston into the valve.
When the valve is fully opened, the piston will go through the valve and continue straight through the T, stopping at the endcap (a spring here would probably be needed to relieve stress from the cap), while the air escapes through the leg of the T and into the barrel. Returning the piston could be done by gravity, by a spring/rubber band pulling it back, or manually by poking through the vent hole in the endcap. Some sort of push rod could be placed on top of the endcap to simplify resetting. Also using an unvented endcap might work, using the built-up pressure to return the piston, but that might decrease efficiency somewhat since the piston will be pushed down by the air pressure while firing.
I hope someone will atleast try out this idea, just to see if/how it works... I don't have the materials/tools/space/pressurezed air to try it out.
Maybe


Top 
 Profile  
 
 Post Posted: Mon Jul 28, 2003 5:00 am 
Offline
Site Admin

Joined: Sun Feb 12, 2012 1:19 am
Posts: 10742
Originaly posted by Namor,
on a lathe to fit perfectly in the ball valve opening


Top 
 Profile  
 
 Post subject: Spring loaded.
 Post Posted: Mon Jul 28, 2003 7:00 am 
Offline
Site Admin

Joined: Sun Feb 12, 2012 1:19 am
Posts: 10742
Originaly posted by thehalls,
At work we've got a 5" air gun that operates at (IIRC) 250 psi. It uses a ball valve. What opens that ball valve is a pnuematic actuator that is actually hooked into the main reservoir.

We've another gun (don't remember the bore or pressure, but reasonably large I assure you) that just uses some large springs to open the valve.

Both guns are (obviously) massive and work quite well for their intended purpose (military R&D).


Top 
 Profile  
 
 Post Posted: Mon Jul 28, 2003 7:00 am 
Offline
Site Admin

Joined: Sun Feb 12, 2012 1:19 am
Posts: 10742
Originaly posted by mta,
Are you guys shooting chickens at jet windshields to see how they hold up to bird strikes?


Top 
 Profile  
 
 Post Posted: Mon Jul 28, 2003 8:00 am 
Offline
Site Admin

Joined: Sun Feb 12, 2012 1:19 am
Posts: 10742
Originaly posted by GalFisk,
When the valve is almost fully open, the piston will only have a small edge to seal against, and the force on that edge will be quite high. I think PVC would work though, it would probably hold longer if the end sealing against the valve is shaped to fit snugly against the ball, but that might be hard to achieve, and the result would probably not justify the work it takes. If the pipe inside and/or the piston outside isn't perfectly smooth, O-rings might be an idea to use to prevent leakage. But then again if the leakage isn't very big, the period when it can occur is very short, and any leakage will be vented through the endcap instead of nudging the projectile. Proper sealing when the piston reaches the endcap would be much more important.


Top 
 Profile  
 
Display posts from previous:  Sort by  
 
Forum locked This topic is locked, you cannot edit posts or make further replies.  [ 13 posts ]  Go to page 1, 2  Next

Board index » Archive » Old Spudtech Message Board » Pneumatic Launchers


Who is online

Users browsing this forum: No registered users and 7 guests

 
 

 
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron