| Author |
Message
|
| Hawkeye |
 Posted: 11/13/2007 18:22 PM Post subject: Piston/Hammer Valve combo |
 |
|
Major
Joined: 21 Jan 2007
Posts: 358
997.37 Spud Bux
|
One more thought on repeating shot capability.
This one involves two fairly large tanks pumped to very high pressure. One is set up like any regular piston gun with the piston also functioning as a hammer to knock open a valve on the second tank. The thought is that the valve that the piston strikes against will open under the fairly violent blow a piston tends to give and rapidly re-pressurize the pilot area, with some secondary fill to the firing chamber as well. That should reset the piston long before excess air is wasted.
The piston could just have a long bolt or rod through it and extended behind it so that it reaches the secondary valve as it moves back. Thoughts?
Another possible auto concept would be to mount a weak pop-off valve where the regular exhaust would be and have it held firmly shut. Once the gun is pumped up, if the pop of valve is manually released, will it cycle on its own until it runs down to the set pressure of the pop-off? Still using the above piston/hammer principle of course.
I realize that similar ideas have been posted before but I don't think they were exactly like these ones. Let me know if they are.
As an aside the tanks could still be pumped up simultaneously through the pilot area separating them. The pressure build up will also unseat the rear valve as well and allow the secondary tank to fill at the same time as the firing chamber is being pressurized.
|
|
| Back to top |
|
 |
|
|
|
| jackssmirkingrevenge |
| Posted: 11/13/2007 18:32 PM Post subject: |
|
|
space monkey
Joined: 15 Mar 2007
Posts: 7050
11306.91 Spud Bux
|
Kinda sorta like this?
| Description: |
|
| Filesize: |
21.1 KB |
| Viewed: |
438 Time(s) |
|
|
|
| Back to top |
|
|
| hubb017 |
| Posted: 11/13/2007 18:48 PM Post subject: |
|
|
Sarcasmo
Joined: 28 May 2007
Posts: 1475
584.33 Spud Bux
|
| Assuming the yellow thing is some sort of check valve (referring to JSR's diagram), it looks like it will work, but how much air will be released through the secondary valve? Will it be enough for consistent shots?
|
|
| Back to top |
|
|
| jackssmirkingrevenge |
| Posted: 11/13/2007 18:50 PM Post subject: |
|
|
space monkey
Joined: 15 Mar 2007
Posts: 7050
11306.91 Spud Bux
|
| The yellow thing is meant to be a schrader valve.
|
|
| Back to top |
|
|
| hubb017 |
| Posted: 11/13/2007 18:56 PM Post subject: |
|
|
Sarcasmo
Joined: 28 May 2007
Posts: 1475
584.33 Spud Bux
|
| Technically, a schrader valve is some sort of check valve, correct?
|
|
| Back to top |
|
|
| Hawkeye |
| Posted: 11/13/2007 18:59 PM Post subject: |
|
|
Major
Joined: 21 Jan 2007
Posts: 358
997.37 Spud Bux
|
Not chamber sealing though. Rather a barrel sealer in a T with the chamber under the barrel. A brass T would connect the two chambers and have a pump attachment and blowgun or other exhaust mounted under it.
In your diagram, is it just a schrader connecting the pilot to the second tank? The drawback to that is that I doubt the piston will reset fast enough to conserve air. The piston will likely smash the schrader too hard and striking the pin would take some precise work. Even then, how much air is going to come through that tiny opening? It will be like a mouse fart in a hurricane.
I was thinking a much larger valve to be struck open. Something like hard rubber ball faucet sealer with a spring behind it. Something that could take a whack and allow a good blast of air around it for instant piston reset.
Good thoughts though. I'll take a better look at your post and the opinions on it..
|
|
| Back to top |
|
|
| jackssmirkingrevenge |
| Posted: 11/13/2007 19:04 PM Post subject: |
|
|
space monkey
Joined: 15 Mar 2007
Posts: 7050
11306.91 Spud Bux
|
I just used the schrader to illustrate the concept.
Are we saying that it's air from the secondary chamber that refills the pilot and main chamber of the piston valve area?
|
|
| Back to top |
|
|
| Hawkeye |
| Posted: 11/13/2007 19:21 PM Post subject: |
|
|
Major
Joined: 21 Jan 2007
Posts: 358
997.37 Spud Bux
|
Exactly. Every other idea seems to involve somehow trying to temporarily close off the inlet that fills the pilot until it is exhausted. Why not eliminate that problem and have it so that it triggers normally and then basically an internal shot of air resets the piston rather violently. Surely a piston moves back with sufficient force to unseat a rather large valve, even if there is a lot of pressure holding it shut?
I was hoping that the large firing chamber would only empty a minimal amount with each shot. If the calibre was small and the chambers large, shouldn't the efficiency of the piston reset really conserve air? I was hoping that the piston would barely open before the blast of air behind it slammed it shut again. Then it would only be topping up the firing chamber and refilling the pilot, not attempting to totally refill an empty gun. The secondary chamber won't be knocked open long enough for that unless the piston was hammering open a true HPA source and refilling a small pilot and chamber. Which is another idea....
|
|
| Back to top |
|
|
| Hawkeye |
| Posted: 11/13/2007 19:23 PM Post subject: |
|
|
Major
Joined: 21 Jan 2007
Posts: 358
997.37 Spud Bux
|
|
| Back to top |
|
|
| jackssmirkingrevenge |
| Posted: 11/13/2007 19:35 PM Post subject: |
|
|
space monkey
Joined: 15 Mar 2007
Posts: 7050
11306.91 Spud Bux
|
so basically...
| Description: |
|
| Filesize: |
25.88 KB |
| Viewed: |
392 Time(s) |
|
|
|
| Back to top |
|
|
| Hawkeye |
| Posted: 11/13/2007 19:53 PM Post subject: |
|
|
Major
Joined: 21 Jan 2007
Posts: 358
997.37 Spud Bux
|
Yes, that's pretty close. The materials I have to work with(copper and brass fittings) would have the secondary chamber looking more or less like a soda bottle with a rubber ball inside it and a spring behind it. The piston/rod would hit the ball.
If it was filled from the pilot area I think you can see how it would fill the front and back chambers through the same source. Then the two chambers would be balanced and hopefully the two "shots" will tend to keep them fairly equal. Eventually an imbalance will prevent the piston from being able to open the rear valve. That may be prevented by experimenting with piston and rear valve dimensions.
What do you think?It sure looks feasible.
|
|
| Back to top |
|
|
| jackssmirkingrevenge |
| Posted: 11/13/2007 23:52 PM Post subject: |
|
|
space monkey
Joined: 15 Mar 2007
Posts: 7050
11306.91 Spud Bux
|
| looks like it would work, I would add a pipe from the air source to the firing chamber though.
|
|
| Back to top |
|
|
| Skywalker |
| Posted: 01/02/2008 12:39 PM Post subject: |
|
|
Sergeant First Class
Joined: 05 Aug 2007
Posts: 138
514.57 Spud Bux
|
Yeah, good work Hawkeye. I like your solution of only opening the refill valve at a certain time, rather than trying to get it to close at a certain time. THat's ingenious. I had thought of incorporating a large valve in the piston so that when it moved reward, it would open and allow air from the chamber to fill the pilot, and then a spring would return the piston. I suppose you might cross those designs and connect the two reservoirs together to make one, I don't know if that would be good or not.
I can't figure out how the system will respond to pressure drop. Like you said, making it work would probably involve a lot of fiddling. The secondary chamber size is another variable, as is the pilot valve flow. I guess someone will just have to build it. I might be your man, if I had more money to drop on copper+brass. Maybe I will anyway, I'm kinda bored.
EDIT:
It might be a good place to use a chamber-sealer instead of a barrel sealer, as the chamber sealer appears to need less pilot valve psi drop to fire.
|
|
| Back to top |
|
|
|
|
