GTA
All Springer/NP/PCP Air Gun Discussion General => "Bob and Lloyds Workshop" => Topic started by: Nvreloader on May 30, 2023, 10:00:51 PM
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Here is the latest tests, same test format as all the above tests,
Retained air from 1st shot results, in my DragonFly II 22 cal rifle.
Test L4 M +
1= 295 232
2= 433 357
3= 439 449
4= 457 452
5= 495 535
6= 511 625
7= 544 666
8= 611 702
9= 757 779
10= 800 823
11= 849 849
12= 853 869
13= 870* 884*=638@
14= 915* 884*=636@
15= 948* 890*=642@
* = air retained in valve after 1st shot
@ = second shot on the retained air = fps
Bold is my preferred pumps area
M Test
Nothing changed from L4 test, except the weather, down to 60* temps, from 90*+
I am attempting to figure out WHY, I have retained air now, and never had any
on any of the before tests, I check after every shot, past 10 pumps.
I have been told that retained air is a positive, as it allows for a second follow up shot,
if needed, for a hunting pumper rifle.
How would you tune/refine this retained air in the second shot?
Your thoughts or suggestions.........
Thanks,
Don
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Retained air can be increased by reducing the hammer strike, or deceased/eliminated by increasing the hammer strike.... If you are experiencing it now and not previously, did you increase the hammer strike to the point of setting the spring?.... When I am setting up a retained air pumper, I try and get 2 shots of the same velocity, or very close, so you have 1 and a followup....
Bob
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Not sure if the op has gone past factory recommended high number of pumps of 15 as of yet, but that and a little less hammer spring or one or the other should get him close I would assume. Go to 20, slpit the difference and call it 10 pumps per shot ???
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Doesn't pellet weight affect air retention?
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Trolling/Learning ;)
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Last 4 tests, before M test,
Test L1 L2 L3 L4
1= 272 - 252-232-295
2= 351 - 377-354-433
3= 436 - 426-429-439
4= 482 - 465-459-457
5= 511 - 495-482-495
6= 541 - 531-501-511
7= 577 - 567-565-544
8= 593 - 583-705-611
9= 639 - 597-761-757
10= 662- 613-823-800
11= 688- 626-836-849
12= 754- 643-866*-853
13= ------651-900*-870*
14= ------661-------915*
15= ------672-------948*
* = air retained in valve after shot, 1st time ever
(L1 test)
Used a valve with Peek air inlet seal and Peek poppet, .145" air inlet hole,
this air check seal had a .135" Dia x .370" long nose that fit into the inlet hole,
this nose was flush at the face of the valve. TP hole =.145", .156" bbl hole.
OEM valve spring and Valve stem length .180" from rear of valve,
Same test format as above tests, Alum Hammer, Flat wire hammer spring,
airways opened up to .145" Dia. 14gr Crosman ammo.
No air left after any shot.
(L2 test)
Used a valve with Peek air inlet seal and Peek poppet, .156" air inlet hole,
this air check seal had a .145" Dia x .370" long nose that fit into the inlet hole,
this nose was flush at the face of the valve. TP hole =.156", .156" bbl hole.
OEM valve spring and Valve stem length .180" from rear of valve,
Same test format as above tests, Alum Hammer, Flat wire hammer spring,
airways opened up to .156" Dia. 14gr Crosman ammo.
No air left after any shot.
(L3 test)
Used a valve with Peek air inlet seal and Peek poppet, .145" air inlet hole,
this air check seal had a .135" Dia x .370" long nose that fit into the inlet hole,
this nose was flush at the face of the valve. TP hole =.145", .156" bbl hole.
OEM valve spring and Valve stem length .375" from rear of valve,
Same test format as above tests, Alum Hammer, Flat wire hammer spring,
airways opened up to .145" Dia. 14gr Crosman ammo.
*Air left after shot.
(L4 test)
Used a valve with Peek air inlet seal and Peek poppet, .156" air inlet hole,
this air check seal had a .145" Dia x .370" long nose that fit into the inlet hole,
this nose was flush at the face of the valve. TP hole =.156", .156" bbl hole.
OEM valve spring and Valve stem length .375" from rear of valve,
Same test format as above tests, Alum Hammer, Flat wire hammer spring,
airways opened up to .156" Dia. 14gr Crosman ammo.
*Air left after shot.
Bob,
Here is the last 4 tests, before the "M" test, with the notes for each test listed.
I have changed nothing, the pump rod and head "O" ring were oiled
at the start of the L1 test.
Because of the Peek seal/poppet, I did pump to 10 pumps and left it over night,
then fired that shot and checked for retained air, there was none.
I then started the "M" test, as I wanted the info on the retained air shots to explore.
The L1-2 tests were with the OEM .180" length valve stem,
.145" air passage ways then .156" air passage ways,
the L3-4 tests were with the .375" length valve stem,
.145" air passage ways then .156" air passage ways,
Bbl hole is .156"
Using a Flat wire spring, 2.500" long, weight = 8-9#'s, .415" O/S Dia, .265" I/S Dia,
.022" thick Flat wire, 25 coils, Alum Hammer weight at 533grains. 14 gr Crosman ammo.
The spring was set several times before use, and is the same spring used thru all the tests.
https://www.gatewaytoairguns.org/GTA/index.php?topic=195725.500, (https://www.gatewaytoairguns.org/GTA/index.php?topic=195725.500,) all tests are listed here.
James,
Yes, I have gone to 20 pumps, but stop when there is no gain in the fps, for any test,
any test with -------- indicates there was no fps higher.
Sam,
same pellet weight used all thru the 20+ tests.
Thanks all,
Your thoughts or suggestions.......
Don
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Just musing here but it seems that (theoretically) with the right combination of hammer/spring, TP diameter, poppet, and pellet you could tune a modern pumper to be a two shot repeater. Finding the sweet spot where the two shots will fall within 20% (or better!) of each other as regards velocity seems to be the biggest challenge.
I know Airguns of Arizona was marketing an air conserving pumper based on a Benji 392/397. I have no idea what the efficiency or the consistency was like and they don't seem to be offering it anymore. Probably an indication that it didn't work that well.
Good luck! As a pumper enthusiast I'm hoping you succeed.
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Retained air can be increased by reducing the hammer strike, or deceased/eliminated by increasing the hammer strike.... If you are experiencing it now and not previously, did you increase the hammer strike to the point of setting the spring?.... When I am setting up a retained air pumper, I try and get 2 shots of the same velocity, or very close, so you have 1 and a follow up.... Bob
Bob
Per the above information on increasing retained air, I have only 3 ways to allow this,
1. Reduce the Hammer weight,
2. Reduce the hammer spring weight,
3. Or a combo of both?
Or change the valve stem length as per the testing results I have done?
I DON'T like the hammer smacking the rear of the valve, with the .180" OEM stem length.
The best tests have been with the .375" length of valve stem,
with NO hammer strikes.
Am I correct in this line of thinking? I am in uncharted waters here,
as I have no experience, yet of doing this.
I have done these calculations, for the top 3 reading of 13-15 pumps, M test,
the average of the top 3 fps = 886fps av,
the av of the 3- 2nd shots = 639fps av,
886 - (minus) 639 = 247fps difference,
1/2 of 247 = 123fps,
886 - (minus) 123 = 763 fps
639 + 123 = 762 fps,
I know, I can't get this close of (762/3)fps readings, but if I am between 750 to 775fps,
this should be close enough to average around 763fps,
for any of the top end readings that retain air?
Am I correct in this line of thinking??
Sam
I am in uncharted waters for me, but I'll attempt to do the best possible,
providing I can figure out the best way to do it.
As I do want the second shot backup when needed, for this pumper.
Then I see what the best pellet is for this demented Dragon Fly II 22 cal is, I hope. ::)
Thanks Guys,
Your thoughts and suggestions are greatly appreciated,
Don
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Following
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I very much doubt that you are using even 0.180" of poppet travel, more like 0.05-0.10" for most valves that are operating efficiently.... Dump valves, of course, may travel further, and I do agree with you that having the hammer hit the back of the valve is not great.... It gets unpredictable, as the hammer bouncing off the back of the valve can reduce the dwell, even though you were striking it harder....
Hammer energy (valve lift) can be increased by increasing the (average) spring force and/or the travel (compression) distance.... The momentum (valve dwell) can be changed relative to the energy by changing the hammer mass, which changes the ratio of lift to dwell....
Bob
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Bob
This is the latest retained air tests, using a Peek Hammer @ 195grs,
with a flat wire hammer spring 7/8#'s.
5p = 1 shot = 475fps
6p = 1 shot = 511fps
7p = 1 shot = 541fps
8p = 1 shot = 577fps
9p = 1 shot = 564fps
10p = 3 shots = 670-561-511fps
10p = 3 shots = 511-695-423fps
11p = 3 shots = 462-672-544fps
12p = 4 shots = 380-498-692-380fps
13p = 4 shots = 334-423-580-649fps
14p = 6 shots = 252-298-360-465-570-419fps
15p = 6 shots = 223-249-364-469-620-446fps
I am going to make some 100 to 200gr lead weights for the hammer,
to test the results for retained air, the 10p tests is getting close to where I want to be,
for 2 shots, I think?.
I am making an SSG for this rifle, to fine tune it after I get close with the hammer weights.
Your thoughts and suggestions......
Thanks,
Don
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Looking at the 10 shot count #'s I wonder if by adding only a couple pumps or so if that would flatten the 2nd shot, also wonder if that process would continue to produce same speeds or gradually drop off as the balance fades.
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I think I am right on the edge on the hammer weight, by adding some more weight,
it may result in a slightly faster shot and use more air from the next shot,
therefor reducing the number of retained shots?
If you look at the progression of the shots, most of the higher fps readings
come at the end of the string, which I take to mean that the internal pressure of the valve
is lower, so the higher fps reading is shown.
Which would indicate that the hammer weight needs to be increased more?
Or hammer spring needs to be heavier weight?
I just added 100grs to the Peek hammer, and will test for the results today.
I am kinda taking a SWAG here, as I don't under stand it all.
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I think I am right on the edge on the hammer weight, by adding some more weight,
it may result in a slightly faster shot and use more air from the next shot,
therefor reducing the number of retained shots?
If you look at the progression of the shots, most of the higher fps readings
come at the end of the string, which I take to mean that the internal pressure of the valve
is lower, so the higher fps reading is shown.
Which would indicate that the hammer weight needs to be increased more?
Or hammer spring needs to be heavier weight?
I just added 100grs to the Peek hammer, and will test for the results today.
I am kinda taking a SWAG here, as I don't under stand it all.
On the retained air shots from 10 pumps to 15 pumps, the high fps number moves from the first shot (@ 10), to the second shot (@ 10.2 & 11) to the second to last shot (@ 12+).
This is bizarrely associated in my mind with the pcp curve we tune except with a retained air pumper. Hopefully a heavier hammer or spring lands you in the sweet spot of first shot on one side of the curve and second shot on other side of the curve at a similar fps.
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Bob
Does this include the use of a SSG or RVA, for better regulating/uniforming the velocity etc.
Thanks,
Don
Retained air can be increased by reducing the hammer strike, or deceased/eliminated by increasing the hammer strike....When I am setting up a retained air pumper, I try and get 2 shots of the same velocity, or very close, so you have 1 and a follow up.... Bob
Bob
Does this include the use of a RVA or SSG, for regulating the velocity etc.
Thanks,
Don
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Steve Woodward, (Steve n NC) designed and built a 2 shot 39x gun, using a butterfly hammer brake
IF the old yellow is still up on Tapatalk or thw wayback machine then those details should be out there
I built one but havent messed with for so long I forget al the details......