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PostPosted: Fri Jan 18, 2013 7:02 pm 
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Location: quebec
two-stage pump

exacly what i have in mind for my pumper :lol: :lol:
easy to built , simply the same tings of the pump tube ,but one on one ,

i realy like the looks and the idea of the double tube

but dont think its always necesaire for small caliber
and the count of pump is seriously to consider

for any caliber i think its possible to do it whit only one tube
even a shotgun or a 50cal. pumper

but for the useful hunting following shot
an extra resevoir should be the best thing


target man

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PostPosted: Sun Jan 20, 2013 3:54 pm 
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Forgot to mention this but do you think it's possible to reduce effort greatly to pump the gun by putting a smaller valve pump check an limiting the air volume around the check? The more surface area on the valve pump check and volume around it the greater the amount of force there is on it in theory?..

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PostPosted: Sun Jan 20, 2013 4:50 pm 
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Kinetic_Genius wrote:
Forgot to mention this but do you think it's possible to reduce effort greatly to pump the gun by putting a smaller valve pump check an limiting the air volume around the check? The more surface area on the valve pump check and volume around it the greater the amount of force there is on it in theory?..


personaly ,,i dont tjink its possible to realy reduce the effort this way

its the presur in the valve ,who creat that force,
the only way i can imagin ,is to change the pumping set-up ,
to create more force by less effort ,

and maybe 2 separated stage of pumping ??

i think it will be necessaire if we want to go up to 2000 psi like any pcp gun ,

as i saw evanix evoluated in airguning
i'l be not surpris,e they were the first to make a kind of self shoebox compressor incorporated on the rifle, :lol:

but i might say i prefer the way of simply change an o-ring to fix the gun in the woods



target man

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PostPosted: Sun Jan 20, 2013 5:18 pm 
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Well when I had took apart my 1077 to my suprize the valve was linked to the other CO2 intake valve piece with a tiny copper pipe with nothing retaining it into place and it did not pop out of place with 850+ psi! So I figure the tiny area in and around the copper pipe was limiting the amount of force pushing on it.. Just think about it.. 850 psi is 850 pounds per square inch, the area of the tube would be 0.015 square inches maybe? 850 psi x 0.015 sqaure inches = 12.75 pounds of force pushing on that tube!?.. I am waiting for rsterne's input on this.

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PostPosted: Sun Jan 20, 2013 8:47 pm 
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Whatever the pressure is in the valve ultimately pushes against the piston.... It's the piston area that governs how hard the gun is to pump.... Parts in between make no difference....

Bob

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PostPosted: Sun Jan 20, 2013 9:29 pm 
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I have to disagree Bob.. I believe the area on the pump check plays a big role too because you have air resting on it too and the larger it is the more air you have resting on it too which makes it harder to open and harder for the pump piston to open! Correct?..

Didn't you mention that you needed more hammer striking force to open a valve stem if the valve throat port was larger? Why should it not apply to the valve check? :?

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PostPosted: Sun Jan 20, 2013 9:40 pm 
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Simply put, to open the check valve requires the same AIR pressure on both sides of it.... If theres is 1000 psi in the valve, there has to be 1001 psi in the pump.... and once the valve cracks open, the pressure around it is the same everywhere.... It wouldn't matter if it was the size of a pin or a baseball....

There is a slight increase in the pressure required to open the check valve caused by the spring that closes it.... If it takes 10 psi to open the valve itself (with no air in it), then it would take 1010 psi in the pump to open the check valve against 1000 psi in the valve.... That 1010 psi pushes back against the pump piston, and it is THAT pressure, times the area of the piston, that produces the FORCE you must overcome to add any more air to the valve....

A hammer is a completely different situation as you are talking force, not pressure, to crack the shot valve in a PCP.... In that case, you have basically zero pressure on one side, and 1000-3000 psi on the other.... It is that differential in pressure that has to be overcome by the force of the hammer strike.... and if the valve seat area is larger, it takes more force for the same pressure....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sun Jan 20, 2013 10:07 pm 
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rsterne wrote:
Whatever the pressure is in the valve ultimately pushes against the piston.... It's the piston area that governs how hard the gun is to pump.... Parts in between make no difference....

Bob


interesting ,,i haved only the presure in mind
as i understand ,, if i imagine the piston at one feet large,
it will be realy harder in any pressure

its seem like the same of a larger boat one the water ,,it could take much more weight for the same presure aply on the water ,

i figure ,,, a 2 stage pump sytem for a pumper ,
should be like 2 different step,
a larger piston who fill a small area at the fist step
and the smaller piston who push the air of the smalest area in the valve ,in the final step

target man

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PostPosted: Sun Jan 20, 2013 10:19 pm 
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rsterne wrote:
Simply put, to open the check valve requires the same AIR pressure on both sides of it.... If theres is 1000 psi in the valve, there has to be 1001 psi in the pump.... and once the valve cracks open, the pressure around it is the same everywhere.... It wouldn't matter if it was the size of a pin or a baseball....

There is a slight increase in the pressure required to open the check valve caused by the spring that closes it.... If it takes 10 psi to open the valve itself (with no air in it), then it would take 1010 psi in the pump to open the check valve against 1000 psi in the valve.... That 1010 psi pushes back against the pump piston, and it is THAT pressure, times the area of the piston, that produces the FORCE you must overcome to add any more air to the valve....

A hammer is a completely different situation as you are talking force, not pressure, to crack the shot valve in a PCP.... In that case, you have basically zero pressure on one side, and 1000-3000 psi on the other.... It is that differential in pressure that has to be overcome by the force of the hammer strike.... and if the valve seat area is larger, it takes more force for the same pressure....

Bob


If that is true then how does a 850 psi regulator keep the regulator close to stop the 3000 psi of air from the going into the 850 psi portion of the regulator? Or is there different physics involve between both of them (the pump piston and regulator, air going out and air going in, etc.)? Anyways I would like to take a look at some 2-stage and 3-stage diagrams.

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PostPosted: Sun Jan 20, 2013 11:39 pm 
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A regulator has two different diameters on the piston.... The small end is at 3000 psi, and that plus the springs push it open.... The big end is at 850 psi pushing it closed.... When the forces balance, the regulator closes.... When you use air from the output, it opens again....

A two stage pump divides the compression ratio between two sections.... Instead of trying to get 100:1 in a single stage to raise the pressure to 100 bar, it uses two stages of 10:1 each.... The first raises the pressure to 10 bar, and the second goes from 10 bar to 100 bar.... If you want equal resistance to pumping in both directions, the second stage would be 1/10th the area (ie about 32% of the diameter).... If the first stage was 1" diameter and the second stage was 5/16" diameter, and they both had a compression ratio of 10:1, then one complete cycle would raise the pressure 100 times and the force on both strokes would be the same....

Bob

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Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Thu Aug 29, 2013 8:35 am 
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rsterne wrote:
My version of the Millenium Pumper is finally finished.... It uses a .25 cal Lothar Walther barrel, a Disco main tube, and a Mac1 extended Billet linkage, and weighs 7.25 lbs. without the scope, which is a Leapers 4-16 x 40 AO MilDot.... Here's what it looks like....

Image

The Boyd's Blaster thumbhole stock has a swell in the forearm right where you grip it for pumping, and was a perfect choice.... The pump stroke is long, but significantly easier at 1800 psi than the Carbine was at 1500.... I have pumped the gun by hand to 2000 psi, and I would consider that a safe upper limit.... Over 60 FPE with EunJins should be pretty easy at that pressure....

Image

The pump actually works better than the one in the Carbine did, filling the 28.5 cc valve faster than the Carbine did its 27 cc valve.... It takes 80 pumps to fill to 1800 psi from empty.... The second graph shows the number of pumps to refill after each shot when the gun is set up for three shots of 40 FPE.... This gun actually takes fewer pumps while producing 40 FPE per shot than the Carbine did at 30 FPE per shot....

Image

Filling to 1800 psi gives a choice of three different tunes just by resetting the RVA.... I can get 1 shot at 950 fps (51 FPE), 2 shots at 898 fps (45.4 FPE), or 3 shots at an average of 846 fps (40.4 FPE) within 30 fps (less than a 4% ES).... While the gun can be pumped to 2000 psi, I feel that these three settings give the best balance between power and pumping....

Image

The graph above shows the velocity of the "next" shot in each string.... You can see that the 4th shot when the gun is set up for three shots of 40 FPE is still about 30 FPE.... plenty good enough for a close follow-up or a coup de gras.... I'm extremely pleased with the way this project turned out.... It surpassed all my expectations, and performs better than I could have ever dreamed or hoped for....

Bob
Bob sorry to bring up an old post but I was curious. I have trouble interpreting the graph to find what I'm looking for. I was wondering how many pump,s to recharge per shot. If I read the graph right it look,s like 10. If I were to recharge after 1 shot.?

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PostPosted: Thu Aug 29, 2013 9:48 am 
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11 pumps after one shot, 24 after two, 40 after three.... That makes the first shot the most efficient, so if possible you would always recharge after 1 shot....

Bob

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Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Thu Aug 29, 2013 1:13 pm 
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Thank,s Bob.

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