Air conservation Theory....

Air conservation Theory....

Joined: March 1st, 2002, 12:22 am

November 21st, 2011, 4:44 am #1


All this talk of HDDs has thinking of AC stuff again.....

Scot said:A half weight striker should get you started. Once the gun will fire a second shot with no pumping, at somewhere near the velocity of the first shot, figure out how many pumps it takes to recharge the gun for another two at the same velocity, then start tweaking stuff to up the power on those shots.

Scot's stance on lightwieght strikers is well known. And I understand why he says that. But my perspective has some trees blocking the view.... What do I use to "fill in the gaps" toward getting the second shot being roughly equivilant to the first? Spring adjuster (like I did on the AC397build)?, more pumps? Increase valve volume? More red parts?

Are there generic steps to follow for experimentation towards the operational goal?

TIA



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Last edited by dan_house on November 21st, 2011, 4:45 am, edited 1 time in total.
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Joined: April 28th, 2010, 12:23 am

November 21st, 2011, 4:58 am #2

having more valve volume and a gauge would be key to having duplicate shots with less pumping, basically 20 pumps or so to get started , then maintaing said pressure by eying the gauge as u go.
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Joined: April 1st, 2009, 3:18 am

November 21st, 2011, 5:08 am #3

...and traded to your buddy Chris? With that gun, the little pump stroke is has, uses a 2100/2200 valve. On ten pumps, it would produce two 450fps range shots.

That was a real one-off proto for when the next time comes around. The work will be much nicer next time, but the same ideas used. No HDD in it, but suspect that it would have truly gained a great deal of benefit.

"The majority of things in our lives are created by folks no smarter than the rest. Afterall, the world is comprised, and operated by C average people intellctually, academically, and morally. These people are often the great pioneers that set the precedent for what excellence should be."
Last edited by Duane30 on November 21st, 2011, 5:58 am, edited 1 time in total.
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Joined: March 1st, 2002, 12:22 am

November 21st, 2011, 5:21 am #4


Which is where I was going with my prodding of Scot and Steve.


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Joined: April 28th, 2010, 12:23 am

November 21st, 2011, 5:30 am #5

...and traded to your buddy Chris? With that gun, the little pump stroke is has, uses a 2100/2200 valve. On ten pumps, it would produce two 450fps range shots.

That was a real one-off proto for when the next time comes around. The work will be much nicer next time, but the same ideas used. No HDD in it, but suspect that it would have truly gained a great deal of benefit.

"The majority of things in our lives are created by folks no smarter than the rest. Afterall, the world is comprised, and operated by C average people intellctually, academically, and morally. These people are often the great pioneers that set the precedent for what excellence should be."
and got the idea real fast, didnt quite grasp the bigger picture at the time, now i do.. was it a different valve or res on it??
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Joined: March 1st, 2002, 12:22 am

November 21st, 2011, 5:34 am #6

having more valve volume and a gauge would be key to having duplicate shots with less pumping, basically 20 pumps or so to get started , then maintaing said pressure by eying the gauge as u go.
would that be a Mindi? Ignoring the bad pun, AC takes the one thing wrong with pumpers mostly out of the picture.

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the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
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Joined: April 28th, 2010, 12:23 am

November 21st, 2011, 5:41 am #7

shot the 760 today, thats getting incinerated next time i see a fire, except the stock , i like that.yes steves design is simple and works well.for some reason i have a strange obsession with bigger storage.
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Joined: November 28th, 2002, 6:26 pm

November 21st, 2011, 6:09 am #8

All this talk of HDDs has thinking of AC stuff again.....

Scot said:A half weight striker should get you started. Once the gun will fire a second shot with no pumping, at somewhere near the velocity of the first shot, figure out how many pumps it takes to recharge the gun for another two at the same velocity, then start tweaking stuff to up the power on those shots.

Scot's stance on lightwieght strikers is well known. And I understand why he says that. But my perspective has some trees blocking the view.... What do I use to "fill in the gaps" toward getting the second shot being roughly equivilant to the first? Spring adjuster (like I did on the AC397build)?, more pumps? Increase valve volume? More red parts?

Are there generic steps to follow for experimentation towards the operational goal?

TIA



dr_subsonic's pneumatic research lab
<img alt="[linked image]" src="http://img.photobucket.com/albums/v301/ ... od-1-1.jpg">
the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
...not to the general problem of making a pumper run successfully in AC mode, but to one particularly elusive aspect of it: Coaxing the valve to consistently pressurize to the same chosen PSI, shot after shot, and not gradually drift away to either...

1. Low pressure with wimpy MVs, or (even worse)...
2. Valve-locking and pump-lever-bending high pressure.

Accomplishing this the elegant way Scot does - with implicit regulation based on pump stroke counting - is a cool trick, in which flea-weight strikers are (just one) key ingredient in the recipe.

But another AC recipe evades the whole issue - by adding the ingredient of a pressure sensor. Then all you have to do is choose a target charging pressure and pump until the sensor says you're there.

After that, AC tuning consists mostly of just adjusting hammer spring energy for whatever amount of power - and pumping between shots - you prefer.

Steve
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Joined: February 9th, 2006, 10:35 pm

November 21st, 2011, 12:27 pm #9

All this talk of HDDs has thinking of AC stuff again.....

Scot said:A half weight striker should get you started. Once the gun will fire a second shot with no pumping, at somewhere near the velocity of the first shot, figure out how many pumps it takes to recharge the gun for another two at the same velocity, then start tweaking stuff to up the power on those shots.

Scot's stance on lightwieght strikers is well known. And I understand why he says that. But my perspective has some trees blocking the view.... What do I use to "fill in the gaps" toward getting the second shot being roughly equivilant to the first? Spring adjuster (like I did on the AC397build)?, more pumps? Increase valve volume? More red parts?

Are there generic steps to follow for experimentation towards the operational goal?

TIA



dr_subsonic's pneumatic research lab
<img alt="[linked image]" src="http://img.photobucket.com/albums/v301/ ... od-1-1.jpg">
the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
In trying to build a pumper that stays just below the 500 fps limit, regardless of how many times the gun is pumped this guy manages to get a little air conservation going on. At 14 to 16 pumps he gets three shots between 400 470 fps, from a 2289 (basically a 1377 with a .22 caliber, 14" barrel and shoulder stock) using little more than a FTP and valve and a 2240 hammer spring. I know that we in America "need" more fps in order to punch holes in our better grade of paper and tougher bunnies and squirrels, but it's a start.

http://www.getphpbb.com/phpbb/viewtopic ... orum=drfaf

Another similar project this fellow did was with a 1377. I think on that one he had to lighten the hammer/striker too. Don't have that link handy.

I plink, therefore I am.
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Joined: November 28th, 2002, 6:26 pm

November 21st, 2011, 3:29 pm #10

...at 16 pumps. I think he claims only two at 16, and doesn't even start taking a third shot until 17. Also, he shows no combination that gives three shots at 400 fps or above, not even out at at 20+ pumps.



Still it's an interesting post. Thanks for linking to it.

Steve
Last edited by pneuguy on November 21st, 2011, 4:40 pm, edited 1 time in total.
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