DEMYSTIFYING " What is COBRA valve tech ? "

[HYspd]

oh yeah....i got the program on the vent as soon as i understood it's a gas ram that starts out at reservior pressure ...


i have been building a series of project guns as my basic knowledge grows and I'm in the planning stages of an attemp at 100fpe in a QB platform using .30cal 51gr pellets at 940fps.....I contacted Bob and he was generous with advice and a thread referral that were spot on what i wanted to know even though i didn't know that was what I wanted to know...and even more than that covered 3 or 4 follow up questions i hadn't asked yet...

so much for short story long....the end is.....bore diameter ports for power production and a super fast valve for air conservation tuned to the gory edge might get there if i can get enough reservior area at the valve and the streamlined spring concept ought kick up the flow rate.....the vent gives tuneablity

[Denward]

I have a war Cobra valve in my 22 marauder. It's paired with a Huma regulator set at about 2100 psi. As some of you may know from my other posts, I've been having major consistency issues. While it is more efficient compared to my stock valve at the same power level, the trade off for me, has been consistency. Keep in mind this is a sample size of 1. Even without the regulator, the stock valve is more consistent for me.

With a regulator, mine cannot use a light weight hammer in conjunction with a free floating system (TSS, short 262 spring, etc). Mine currently uses the hill hammer with stock spring and about .25 inch of preload on the hammer spring. ES is about 35fps. It was about 17fps with the stock valve, hammer, spring, regulator. With the war Cobra valve, regulator, hill hammer free floated, ES was 150+ feet. Again, this is a sample size of 1. Take it with a grain of salt.

[Motorhead]

I have a war Cobra valve in my 22 marauder. It's paired with a Huma regulator set at about 2100 psi. As some of you may know from my other posts, I've been having major consistency issues. While it is more efficient compared to my stock valve at the same power level, the trade off for me, has been consistency. Keep in mind this is a sample size of 1. Even without the regulator, the stock valve is more consistent for me.

With a regulator, mine cannot use a light weight hammer in conjunction with a free floating system (TSS, short 262 spring, etc). Mine currently uses the hill hammer with stock spring and about .25 inch of preload on the hammer spring. ES is about 35fps. It was about 17fps with the stock valve, hammer, spring, regulator. With the war Cobra valve, regulator, hill hammer free floated, ES was 150+ feet. Again, this is a sample size of 1. Take it with a grain of salt.

As with ANY PCP be it regulated or not, is finding at any desired power / speed setting where it is operating in respect to it's bell curve potential. If or when the balance of hammer weight, stroke of hammer, strength of hammer spring & pressure as primary contributors are skewed extremely one way or the other and not sorta in the middle ranges your going to get funky operation & instability. 
Now add in a "Cobra" air spring which can / has such strong influence on the valves dwell cycle and things can really go wonky !!!

Knowing folks love to self tune, read How-Too threads, Buy hop-up parts based upon someones elses tuning tech and then MARRY this Mix & Mis-match group into what is thought to be the best of all worlds so it has to work great configuration.   
In theory all these parts have merit used somewhat within the parameters of the original tuning but don't always work together as one might expect.

In my own R&D of valving ( That I keep to my self mostly ) I too have hit speed bumps being stumped that the combo in the gun is not performing or working well at all. 
With all we know, think we know & info shared freely out there on the web to read the modern PCP is still being figured out as more tech gets used within them.   
YES the rabbit hole keeps getting deeper !!

[Dairyboy]

Something seems off with consistency issues with your WAR Cobra valve. Just ran 2 guns through the chrony a week or 2 ago one a buddies .25 I was getting setup and one my personal WARP and both have very good consistency.

Created: 02-05-2018 05:52:41 PM
Description: .25 Mrod
Notes 1: 130bar reg set (too low)
Notes 2: Cobra valve
Distance to Chrono (FT): 3.00
Ballistic Coefficient: 1.000
Bullet Weight (gr): 25.390
Altitude (FT): 0.0
Temp: 54 °F
BP: 30.04 inHG
Shots
#     FPS        FT-LBS     PF
27    851        40.84      21.61     
26    851        40.84      21.61     
25    846        40.36      21.48     
24    851        40.84      21.61     
23    848        40.55      21.53     
22    848        40.55      21.53     
21    847        40.45      21.51     
20    847        40.45      21.51     
19    849        40.64      21.56     
18    849        40.64      21.56     
17    846        40.36      21.48     
16    848        40.55      21.53     
15    852        40.93      21.63     
14    852        40.93      21.63     
13    847        40.45      21.51     
12    847        40.45      21.51     
11    849        40.64      21.56     
10    852        40.93      21.63     
9     849        40.64      21.56     
8     846        40.36      21.48     
7     850        40.74      21.58     
6     850        40.74      21.58     
5     848        40.55      21.53     
4     849        40.64      21.56     
3     848        40.55      21.53     
2     848        40.55      21.53     
1     847        40.45      21.51     
Average: 848.70
StdDev: 1.88
Min: 846
Max: 852
Spread: 6
True MV: 848.99
Shots/sec: 0.15
Group Size (IN): 0.00

Created: 02-02-2018 06:47:01 PM
Description: .30 WARP COBRA
Notes 1:
Notes 2: reg set 2400psi
Distance to Chrono (FT): 3.00
Ballistic Coefficient: 1.000
Bullet Weight (gr): 44.750
Altitude (FT): 0.0
Temp: 47 °F
BP: 30.10 inHG
Shots
#     FPS        FT-LBS     PF
44    807        64.72      36.11     
43    808        64.88      36.16     
42    807        64.72      36.11     
41    808        64.88      36.16     
40    811        65.37      36.29     
39    813        65.69      36.38     
38    814        65.85      36.43     
37    810        65.20      36.25     
36    812        65.53      36.34     
35    808        64.88      36.16     
34    810        65.20      36.25     
33    811        65.37      36.29     
32    808        64.88      36.16     
31    807        64.72      36.11     
30    812        65.53      36.34     
29    813        65.69      36.38     
28    812        65.53      36.34     
27    813        65.69      36.38     
26    807        64.72      36.11     
25    815        66.01      36.47     
24    817        66.34      36.56     
23    815        66.01      36.47     
22    812        65.53      36.34     
21    808        64.88      36.16     
20    812        65.53      36.34     
19    814        65.85      36.43     
18    812        65.53      36.34     
17    811        65.37      36.29     
16    812        65.53      36.34     
15    811        65.37      36.29     
14    815        66.01      36.47     
13    817        66.34      36.56     
12    811        65.37      36.29     
11    812        65.53      36.34     
10    817        66.34      36.56     
9     814        65.85      36.43     
8     815        66.01      36.47     
7     811        65.37      36.29     
6     809        65.04      36.20     
5     814        65.85      36.43     
4     817        66.34      36.56     
3     817        66.34      36.56     
2     815        66.01      36.47     
1     806        64.56      36.07     
Average: 811.82
StdDev: 3.15
Min: 806
Max: 817
Spread: 11
True MV: 812.09
Shots/sec: 0.07
Group Size (IN): 0.00

[Denward]

Something seems off with consistency issues with your WAR Cobra valve. Just ran 2 guns through the chrony a week or 2 ago one a buddies .25 I was getting setup and one my personal WARP and both have very good consistency.

Created: 02-05-2018 05:52:41 PM
Description: .25 Mrod
Notes 1: 130bar reg set (too low)
Notes 2: Cobra valve
Distance to Chrono (FT): 3.00
Ballistic Coefficient: 1.000
Bullet Weight (gr): 25.390
Altitude (FT): 0.0
Temp: 54 °F
BP: 30.04 inHG
Shots
#     FPS        FT-LBS     PF
27    851        40.84      21.61     
26    851        40.84      21.61     
25    846        40.36      21.48     
24    851        40.84      21.61     
23    848        40.55      21.53     
22    848        40.55      21.53     
21    847        40.45      21.51     
20    847        40.45      21.51     
19    849        40.64      21.56     
18    849        40.64      21.56     
17    846        40.36      21.48     
16    848        40.55      21.53     
15    852        40.93      21.63     
14    852        40.93      21.63     
13    847        40.45      21.51     
12    847        40.45      21.51     
11    849        40.64      21.56     
10    852        40.93      21.63     
9     849        40.64      21.56     
8     846        40.36      21.48     
7     850        40.74      21.58     
6     850        40.74      21.58     
5     848        40.55      21.53     
4     849        40.64      21.56     
3     848        40.55      21.53     
2     848        40.55      21.53     
1     847        40.45      21.51     
Average: 848.70
StdDev: 1.88
Min: 846
Max: 852
Spread: 6
True MV: 848.99
Shots/sec: 0.15
Group Size (IN): 0.00

Created: 02-02-2018 06:47:01 PM
Description: .30 WARP COBRA
Notes 1:
Notes 2: reg set 2400psi
Distance to Chrono (FT): 3.00
Ballistic Coefficient: 1.000
Bullet Weight (gr): 44.750
Altitude (FT): 0.0
Temp: 47 °F
BP: 30.10 inHG
Shots
#     FPS        FT-LBS     PF
44    807        64.72      36.11     
43    808        64.88      36.16     
42    807        64.72      36.11     
41    808        64.88      36.16     
40    811        65.37      36.29     
39    813        65.69      36.38     
38    814        65.85      36.43     
37    810        65.20      36.25     
36    812        65.53      36.34     
35    808        64.88      36.16     
34    810        65.20      36.25     
33    811        65.37      36.29     
32    808        64.88      36.16     
31    807        64.72      36.11     
30    812        65.53      36.34     
29    813        65.69      36.38     
28    812        65.53      36.34     
27    813        65.69      36.38     
26    807        64.72      36.11     
25    815        66.01      36.47     
24    817        66.34      36.56     
23    815        66.01      36.47     
22    812        65.53      36.34     
21    808        64.88      36.16     
20    812        65.53      36.34     
19    814        65.85      36.43     
18    812        65.53      36.34     
17    811        65.37      36.29     
16    812        65.53      36.34     
15    811        65.37      36.29     
14    815        66.01      36.47     
13    817        66.34      36.56     
12    811        65.37      36.29     
11    812        65.53      36.34     
10    817        66.34      36.56     
9     814        65.85      36.43     
8     815        66.01      36.47     
7     811        65.37      36.29     
6     809        65.04      36.20     
5     814        65.85      36.43     
4     817        66.34      36.56     
3     817        66.34      36.56     
2     815        66.01      36.47     
1     806        64.56      36.07     
Average: 811.82
StdDev: 3.15
Min: 806
Max: 817
Spread: 11
True MV: 812.09
Shots/sec: 0.07
Group Size (IN): 0.00

I agree something is up, it performed very well just a few weeks ago with the same reg pressure, war cobra, 44 gram MDS hammer, stock spring  with 1/8 preload. Ive taken it apart about 20 times the last few weeks to try to figure out what's wrong. O ring is good. Valve doesn't bind. Who knows. It works now with my current setup. I'm gonna leave it unless it goes crazy again

[Tweeter]

So is the JSA SS valve considered a better alternative to the Cobra?

I'm not sure ( but pretty confident ) the Cobra valve was the past WAR valve with the Cobra tech similar to 1st example shown.  The SS valve is a new beast all together being a Balanced valve with cobra tech.

The SS balanced version opens with less hammer strike , weight of hammer, spring energy etc ....
Honestly in terms of power there both going to be similar tho will require far different hammer strike energy and cocking force to run at the same power level.

My WarP uses the WAR valve with Cobra tech and makes more than enough power for .177 /.20 / .25 cal pellet duty.

** Please correct me if I am mistaken tho 

Does the Cobra valve require less hammer strike/cocking force than the original WAR valve to shoot the same speed?

[oldpro]

Something seems off with consistency issues with your WAR Cobra valve. Just ran 2 guns through the chrony a week or 2 ago one a buddies .25 I was getting setup and one my personal WARP and both have very good consistency.

Created: 02-05-2018 05:52:41 PM
Description: .25 Mrod
Notes 1: 130bar reg set (too low)
Notes 2: Cobra valve
Distance to Chrono (FT): 3.00
Ballistic Coefficient: 1.000
Bullet Weight (gr): 25.390
Altitude (FT): 0.0
Temp: 54 °F
BP: 30.04 inHG
Shots
#     FPS        FT-LBS     PF
27    851        40.84      21.61     
26    851        40.84      21.61     
25    846        40.36      21.48     
24    851        40.84      21.61     
23    848        40.55      21.53     
22    848        40.55      21.53     
21    847        40.45      21.51     
20    847        40.45      21.51     
19    849        40.64      21.56     
18    849        40.64      21.56     
17    846        40.36      21.48     
16    848        40.55      21.53     
15    852        40.93      21.63     
14    852        40.93      21.63     
13    847        40.45      21.51     
12    847        40.45      21.51     
11    849        40.64      21.56     
10    852        40.93      21.63     
9     849        40.64      21.56     
8     846        40.36      21.48     
7     850        40.74      21.58     
6     850        40.74      21.58     
5     848        40.55      21.53     
4     849        40.64      21.56     
3     848        40.55      21.53     
2     848        40.55      21.53     
1     847        40.45      21.51     
Average: 848.70
StdDev: 1.88
Min: 846
Max: 852
Spread: 6
True MV: 848.99
Shots/sec: 0.15
Group Size (IN): 0.00

Created: 02-02-2018 06:47:01 PM
Description: .30 WARP COBRA
Notes 1:
Notes 2: reg set 2400psi
Distance to Chrono (FT): 3.00
Ballistic Coefficient: 1.000
Bullet Weight (gr): 44.750
Altitude (FT): 0.0
Temp: 47 °F
BP: 30.10 inHG
Shots
#     FPS        FT-LBS     PF
44    807        64.72      36.11     
43    808        64.88      36.16     
42    807        64.72      36.11     
41    808        64.88      36.16     
40    811        65.37      36.29     
39    813        65.69      36.38     
38    814        65.85      36.43     
37    810        65.20      36.25     
36    812        65.53      36.34     
35    808        64.88      36.16     
34    810        65.20      36.25     
33    811        65.37      36.29     
32    808        64.88      36.16     
31    807        64.72      36.11     
30    812        65.53      36.34     
29    813        65.69      36.38     
28    812        65.53      36.34     
27    813        65.69      36.38     
26    807        64.72      36.11     
25    815        66.01      36.47     
24    817        66.34      36.56     
23    815        66.01      36.47     
22    812        65.53      36.34     
21    808        64.88      36.16     
20    812        65.53      36.34     
19    814        65.85      36.43     
18    812        65.53      36.34     
17    811        65.37      36.29     
16    812        65.53      36.34     
15    811        65.37      36.29     
14    815        66.01      36.47     
13    817        66.34      36.56     
12    811        65.37      36.29     
11    812        65.53      36.34     
10    817        66.34      36.56     
9     814        65.85      36.43     
8     815        66.01      36.47     
7     811        65.37      36.29     
6     809        65.04      36.20     
5     814        65.85      36.43     
4     817        66.34      36.56     
3     817        66.34      36.56     
2     815        66.01      36.47     
1     806        64.56      36.07     
Average: 811.82
StdDev: 3.15
Min: 806
Max: 817
Spread: 11
True MV: 812.09
Shots/sec: 0.07
Group Size (IN): 0.00

I agree something is up, it performed very well just a few weeks ago with the same reg pressure, war cobra, 44 gram MDS hammer, stock spring  with 1/8 preload. Ive taken it apart about 20 times the last few weeks to try to figure out what's wrong. O ring is good. Valve doesn't bind. Who knows. It works now with my current setup. I'm gonna leave it unless it goes crazy again

I would look at the hammer and not the valve. Looks like a typical hammer binding issue.

[oldpro]

So is the JSA SS valve considered a better alternative to the Cobra?

I'm not sure ( but pretty confident ) the Cobra valve was the past WAR valve with the Cobra tech similar to 1st example shown.  The SS valve is a new beast all together being a Balanced valve with cobra tech.

The SS balanced version opens with less hammer strike , weight of hammer, spring energy etc ....
Honestly in terms of power there both going to be similar tho will require far different hammer strike energy and cocking force to run at the same power level.

My WarP uses the WAR valve with Cobra tech and makes more than enough power for .177 /.20 / .25 cal pellet duty.

** Please correct me if I am mistaken tho 

Does the Cobra valve require less hammer strike/cocking force than the original WAR valve to shoot the same speed?

It has a smaller or lighter return spring but the piston does close it fast so its pretty much a wash. So not by much

[Tweeter]

Thanks Travis, I thought I had read somewhere that it did but they might have been talking about the smoothness of the MDS hammer or the SS valve.

[Motorhead]

Thinking this thread & subject has been buried long enough .... Shameless bump to get the info out there to a new audience.

[oldpro]

Thinking this thread & subject has been buried long enough .... Shameless bump to get the info out there to a new audience.

I dont think people quite understand whats taking place in the thimble or understand how it helps. Might need to make a video or something.

[Motorhead]

Somewhat a double post ... but don't shoot the messenger 
here is a recent addition in the evolution of the devise with pictures being worth more than words ... the concept should be clear as mud 

https://www.gatewaytoairguns.org/GTA/index.php?topic=149519.msg1525979#msg1525979

[Rallyshark]

I AM going to do this on my Flash, just to see if I can gain some noticeable efficiency.  It ain't bad on the gun now(1.4), but I'm not against getting up higher for sure.  That 1.4 efficiency is at 30fpe, and it is regulated.  I'm able to get 3 magazines per fill(36 shots).  It took a lot of warranty voiding to get there, so what's a little more   I like working on this gun, because it is so simple, and lite.  I tried once to get the cobra working, but I failed on the venting I think...  I hope to get around to version 2 this weekend.  I will update with pictures, of course

On a side note:  I may try to get one of you guys(Travis or Scott) to machine a barrel for it soon?  I'm thinking an 18" LW on it sure would be nice.  The good thing is these barrels should be easier to machine than some of the other Hatsan barrels. 

[rsterne]

Scott, somehow I missed this thread.... Thanks for the great explanation and pics.... When the COBRA tech valve first came out, Lloyd and I looked at it and quickly realized it didn't have any "balancing" effect, so I really never even gave it a second look.... Travis sent me one to try, and I never found any advantage when installed in one of my "high powered" (and therefore high dwell) PCPs.... Travis told us it was much easier to open, but then later discovered that was because the MRod valve used a very strong valve spring, and it was eliminating that which reduced the hammer strike required.... I understood the idea that there was less turbulence, and possibly less "sail" effect on the poppet, which would increase the dwell, allowing a slightly lighter hammer strike, but I never "got" what Travis was talking about regarding the valve closing faster and saving air until I read your excellent explanation, comparing the COBRA cylinder to an "air spring".... THAT's when it finally sunk in what was happening.... 

If we look at using a large vent in the front, and lots of flow into the inside of the valve body, in theory there is no change to the valve operation, because the pressures in all regions (reservoir/plenum, valve body, and poppet chamber) would be the same.... Other than getting rid of turbulence around the valve spring and the head of the poppet, the valve should operate the same (and that is what I found occurring at "maximum" power)…. However, once you restrict the front of the poppet chamber with a small jet, just like in the SS valve, things change.... I still don't understand the exact mechanism why, but as you reduce the jet size, the air in the poppet chamber appears to increase in pressure from compression by the poppet, which increases the rate of the "air spring", and limits the poppet lift, reducing dwell.... It's like using a very light spring when the valve is closed, but a heavier spring during the shot cycle, at least that appears to be what is happening....

I'm sure that cleaning up the flow around the poppet head helps as well, but I'd like to hear your opinion on the above.... Have I finally "got it?".... 

Bob

[nervoustrigger]

Bob, thanks for that.  I was just catching up on this over the last couple of days and that matches my understanding as well except you helped me connect the sail effect to it.

[triggertreat]

I have an original prototype Cobra valve.  It's difficult to crack open much past a 2000psi set point even with the one pound valve spring it has and using a heavy hammer spring, but boy is it efficient.  I'm not sure how the latest/current Cobra valves perform.  Mine has no jet capability.

[oldpro]

 The Cobra valve is actually easier to open but has such a short swell it takes more hammer energy to get up to a high power level so it feels like it’s harder to open. The Cobra chamber acts like a Air spring so when the valve opens the pressure drop around the poppet head isn’t there allowing the valve to dwell long instead the high pressure is trapped inside the poppet driving the valve closed as the pressure drops around the outside of the Cobra chamber. Also this helps reduce hammer bounce and also allows for very low pressure tubes.

[Motorhead]

Bob,
In a nutshell ..... Controlled pressure differential.
The area within valves internal space has a pressure drop as flow heads out towards the pellet. The confines of the "Cobra tube" holds most of the pressure bearing down on the poppet while it was closed ... So the valve poppet once open now keeps a much more even pressure attempting to close it independent of what flow and pressure drop is happening OUTSIDE the tube.

[rsterne]

The area within valves internal space has a pressure drop as flow heads out towards the pellet.

If I understand how flow works, and assuming the inlet area of the valve is greater than the exhaust area (and it always should be)…. there should be virtually no pressure difference between the exhaust port, and the area surrounding the poppet (at the seat), and the area surrounding the Cobra tube (or the valve spring), and the plenum/reservoir.... at the point the air reaches the pellet and it starts to move.... Don't forget, when the valve first opens, the pellet is stationary, and the air molecules are moving randomly at ~ 1650 fps.... so it only takes about 0.05 mSec for the air to travel that ~1" to the pellet, and for the pressure in the exhaust ports to reach reservoir pressure, during which time there is virtually NO flow volume (the HPA just fills the exhaust port, transfer port and chamber), and certainly that small amount of HPA (~1cc) needed to pressurize the porting system can easily get into the valve during that time period through the large holes in the front of the valve....

For there to be more pressure inside the Cobra tube than outside it, there must be something "holding back" the air from moving into the valve body, in the area surrounding the poppet chamber.... I think it much more likely that the poppet moving forward into the Cobra poppet chamber, increasing the pressure there by compressing the air, is a more likely scenario.... I think that is why using a smaller "jet" on the front of the Cobra poppet chamber increases the pressure inside it during the shot cycle.... and thereby reduces the dwell....

As I said before, I don't fully understand the process, but I think it likely that a pressure increase inside the poppet chamber is more likely than a pressure decrease outside it.... certainly in the first part of the shot cycle, anyways.... During the latter part of the shot cycle, when the flow velocity through the seat is high, then the lack of a "sail effect" on the poppet, and less turbulence because of the lack of valve spring, may indeed be playing a part.... but again, if the inlet into the valve is larger than the exhaust there should be almost no pressure differential upstream of the poppet (except that caused by the Cobra inlet jet containing the increased pressure from the poppet compression inside the poppet chamber)....

Whatever the actual mechanism, when used to reduce lift and dwell (as opposed to a high power application)…. it seems that "Cobra Tech" works, and that is what is important.... I suspect using a jet to tune the SS valve for similar applications works in the same way.... but with the added benefit of a balanced valve to reduce the hammer strike required....

Bob

[Motorhead]

The area within valves internal space has a pressure drop as flow heads out towards the pellet.

As I said before, I don't fully understand the process, but I think it likely that a pressure increase inside the poppet chamber is more likely than a pressure decrease outside it.... certainly in the first part of the shot cycle, anyways.... During the latter part of the shot cycle, when the flow velocity through the seat is high, then the lack of a "sail effect" on the poppet, and less turbulence because of the lack of valve spring, may indeed be playing a part.... but again, if the inlet into the valve is larger than the exhaust there should be almost no pressure differential upstream of the poppet (except that caused by the Cobra inlet jet containing the increased pressure from the poppet compression inside the poppet chamber)....

Whatever the actual mechanism, when used to reduce lift and dwell (as opposed to a high power application)…. it seems that "Cobra Tech" works, and that is what is important.... I suspect using a jet to tune the SS valve for similar applications works in the same way.... but with the added benefit of a balanced valve to reduce the hammer strike required....

Bob

A "Point" and an important one at that is .... We're using these primarily in REGULATED guns where there is indeed a pressure loss within the valves interior & plenum.
And is where at the end of the shot cycle the residual pressure kept mostly intact WITHIN the Cobra chamber is indeed higher as valve is closing and only equalizes upon valve shutting and regulator bringing the plenum back up to the set pressure.

My bad ... oups