Balancing the flow within the Mutant valve
:ugeekn: Just had to go in after the success of the plenum mods to find out how balanced the flow was within the mutant valve.
Emptied the air and dismantled barrel / trigger group from receiver / air tube so I could unscrew air tank fitting from receiver giving access to valve body & poppet.
Valve & poppet in hand started measuring the throat & transfer passage sizes finding BOTH at @ .200″
Poppet stem is @ .118″
When doing the math on area of a .200″ hole ( This for Throat ) … we get an AREA value. ( * .0314 sq in )
Then we do the math on the area of the .118″ poppet stem … we get an area value. ( * .019 sq in )
SUBTRACT the area of Stem from the area of Throat … we get a value of whats left in Area to pass air around the two. ( * .0205 sq in )
NOW KEEP IN MIND THE transfer port leaving the .200″ throat is also .200″ all the way to barrel ( Which we’ll cover shortly )
In the case of the Mutant we have a pretty good restriction within the Valve throat when the .118 stem partially blocks it and WHY the practice of stepping down the diameter of poppets stem is a common modification trick :biggrinn:
In this case DID NOT WISH TO WEAKEN poppets stem by reducing its diameter making the stem more prone to breakage … so we address this by increasing the throat size just a little bit.
* In doing some math again for area gain required within throat the Diameter figured is .235″ having an area of ( .0426 sq in )
When we subtract the stem area of .019 sq in from the larger .235″ throat of .0426 sq in we end up with .0317 sq in of area to pass the air headed for the transfer port :biggrinn:
REMEMBER when we started with that .200 throat feeding a .200″ transfer port ( Area of .0314 sq in ) now with valve throat opened up to .235″ diameter with .0317 sq in of actual area past the stem … we now have a balanced flow within valves throat & no longer having any restriction throttling back the air flow & no need for a reduced diameter potentially fragile poppet stem.
:suprisedn: NOW TO MAKE THIS WORK we did need to rebuild the poppets head using a tougher material ( PEEK )
Was able to simply twist and pull off the white ( Delrin perhaps ? ) poppet head from the OEM stem so it could get reused.
The Diameter of the OEM poppet head was .265″ and we Kept it exactly the same with the PEEK replacement made.
* In looking at the OEM poppet head under a magnifying glass it was lightly dented already and would not have survived IMO asked to plug a throat just .035″ larger in diameter ( .0175″ per side which is not very much ) thus w/o even trying it just made up a Heavy Duty replacement.
Thats it for a few hours of fiddle time on the Mutant :8:
Scott
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Hello Endo,
I took a few pictures of my barrel. Unfortunately I have to recharge the batteries so they will be strong enough to transfer the pictures to my PC for uploading. I looked at the barrel port in the link you posted. The port on mine looks similar, but I found the edges inside the barrel to be lightly burred, which I cleaned up. I found the retaining dimple to be well aligned with the barrel port. The crown looked very even in it’s circumference and somehow the lands seems to be burr-free. So I put it all back together and got a bit of an air sting across my face. Just goes to show, it’s always something! I’ll try to sort that out tomorrow.
Darryl
Darryl,
I use J-B paste and Flitz to polish the barrel.
There is a picture on TP of Petr’s “mystery barrel” that I posted earlier in this thread:
http://www.talonairgun.com/forum/viewtopic.php?f=55&t=32414&start=160
Regards,
Endo
HI Endo,
I’ll try to get the barrel pulled in the next day or so, then take a few pictures. Maybe you can help me solve the “mystery” after all. What product did you use to polish your barrel?
Thank you,
Darryl
Darryl,
I got the shorty from Petr with Germany made barrel, which was a substandard barrel.
Then I requested him to replace with the “Cz Made” barrel that he originally promised in his advertisement.
After a few weeks/months, he sent me a “mystery barrel” with slanted TP unaligned with dimple. Dman helped to relocate the dimple. The barrel was shooting so so, but it shoots very well now after I spent quite a bit of time to polish the barrel and TP and also smooth out the inlead. This barrel always shoots faster than any other barrels I had/have – Germany barrel, Listone and the factory stock barrel by ~20 fps under the same HST.
I think the slanted TP may help air pressure and the larger elliptical TP may help air flow. I guess we both have the same barrel since it was a replacement barrel from Petr. Is the TP slanted with elliptical shape? Show me a picture of it (TP and crown), I might be able to recognize it.
Enjoy your tuning…
Regards,
Endo
Hello again Endo,
How did you come across this information. It’s not that I doubt you, because I don’t. And for the record, I have no problem accepting that mystery barrel at the end point of my dealing with the old TGAG. I find the information helpful to me, especially if it means I can play with tuning the Short , keeping in mind what you’ve told me here. I’m thinking short range accuracy (for my shooting needs) and increased shot count. Won’t know until I try.
thanks again Endo,
BTW do you have any idea what barrel I may have? I keep thinking it may be one of those barrels Petr told me was made in the same way as LW barrels. No markings on it at all.
Darryl
Darryl,
The “mystery barrel” from Petr does have elliptical TP and it does have higher air efficiency in terms of pushing higher pellet speed (~20 fps) under the same HST setting for various barrels I have tried in my record — Germany Made, Listone and factory CZ.
The TP in Petr’s barrel is also slanted and the opening is larger than others, which may also help.
Regards,
Endo
It upon measuring was drilled at .170″ being .030″ smaller in diameter than the entirety of transfer passage.
* Sadly a .170″ TP in a .22 caliber barrel is already at the limit IMO in not having a pellet tilt and try to snag the holes edge as it passes by upon loading.
If one were to try and get equal area of the port in barrel to that of transfer it would need to be done by making an elliptical or oval port hole in the barrel.
I HAVE NOT done this and won’t until able to go back in and see HOW DEEP different pellets seat relative to the OEM .170″ round transfer port there now ?
* We don’t want the SIDE of pellet skirt exposed to the air blast coming from the TP. ALL the air as it enters behind the pellet needs to do so 100% from behind the skirt !!
If pellets are seated deep enough so that a little bit of Oval shape can be applied to port to get equal area of the transfer passage feeding it … MORE power will be found.
Scott
Interesting about the barrel port. I was told that my copy (with the mystery barrel) has an elliptical barrel port, but the reason for it was never explained to me. I’ve since seen the term used here and there, but I still hadn’t understood the function of this mod until I read your post. I do recall something about improving efficiency, but I was still uncertain. Your post has helped clear that up a little for me. But it seems that increasing the barrel port is one part of improving the efficiency of the gun. I do not know if the valve was touched at all. Is barrel porting in itself effective at improving the air efficiency of the gun without the other changes? This is for more power per what?
thanks!
Darryl
I don’t know what any of this means or if it makes a difference but I can see you have a passion for this kind of thing. And I respect that, Keep it coming! :8:
Regards
LarryW 😉
That area gain is nothing and in choosing size of .235 was as close as i could get to TP’s area with reamers I had on hand.
Bigger won’t gain you a thing and slightly smaller … say .220″ /.225″ likely be better yet and may allow keeping OEM poppet in place ?
Forgot … The barrel port.
It upon measuring was drilled at .170″ being .030″ smaller in diameter than the entirety of transfer passage.
* Sadly a .170″ TP in a .22 caliber barrel is already at the limit IMO in not having a pellet tilt and try to snag the holes edge as it passes by upon loading.
If one were to try and get equal area of the port in barrel to that of transfer it would need to be done by making an elliptical or oval port hole in the barrel.
I HAVE NOT done this and won’t until able to go back in and see HOW DEEP different pellets seat relative to the OEM .170″ round transfer port there now ?
* We don’t want the SIDE of pellet skirt exposed to the air blast coming from the TP. ALL the air as it enters behind the pellet needs to do so 100% from behind the skirt !!
If pellets are seated deep enough so that a little bit of Oval shape can be applied to port to get equal area of the transfer passage feeding it … MORE power will be found.
Scott
Very interesting Scott, welcome and I enjoyed reading your design modifications. Can we agree you are starting with a very effective design to begin with? What are your expectations with an increase of .0003″ of area? The modified stem valve would be a big positive. Please post your results as your mods take shape.
Regards
LarryW 😉
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I took a few pictures of my barrel. Unfortunately I have to recharge the batteries so they will be strong enough to transfer the pictures to my PC for uploading. I looked at the barrel port in the link you posted. The port on mine looks similar, but I found the edges inside the barrel to be lightly burred, which I cleaned up. I found the retaining dimple to be well aligned with the barrel port. The crown looked very even in it’s circumference and somehow the lands seems to be burr-free. So I put it all back together and got a bit of an air sting across my face. Just goes to show, it’s always something! I’ll try to sort that out tomorrow.
Darryl
Can either of you MEASURE diameter of the transfer port hole in these barrels please ?