Quick ? for those who have experienced regulator creep

Forums PCP Airguns Quick ? for those who have experienced regulator creep

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    cmatera
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    Does regulator creep always affect the POI vertically, or can it affect it horizontally or both vertically&horizontally?

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    nervoustrig
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    Chiefly vertical because it causes the velocity to change.  However the nature of barrel harmonics can also lead to changes in the horizontal as well.

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    Motorhead
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    If the guns hammer strike and base Set-Point pressure are correct … regulator creep has ZERO effect on velocity or POI

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    nervoustrig
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    I’m all but ready to give up on banging that drum :)

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    Centercut
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    nervoustrig

    I’m all but ready to give up on banging that drum :)

    I’m with you. If reg creep didn’t affect velocity and vertical POI then why bother having a reg? Maybe we can take a step backwards in time and get rid of them all?  ;). FYI, I have a properly and perfectly tuned .30 FX Bobcat Mk2 that two years ago had reg creep and inconsistent pressures, which resulted in varying POI. Replaced factory FX reg with Huma set at 165 bar and the gun is golden. Now, I can understand that perhaps a 5 bar creep may not significantly affect velocity or POI, or maybe for short distances up to 55 yards the POI change isn’t noticeable…? But significant creep for shooting at challenging longer distances will affect velocity and POI in just about any modern PCP air rifle.  

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    nervoustrig
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    Actually I was agreeing with Scott.  It's not that creep isn't a problem with some regulators, it's that the extent of it is exaggerated by tunes that are not adjusted properly.  Just a couple of days ago I posted an explanation of how the self-regulation (bell curve) of a conventional PCP applies just as readily to regulated PCPs.

    https://www.airgunnation.com/topic/how-much-effect-of-a-consistent-regulator-on-accuracy/#post-529965

    It was met with crickets chirping, as it is much of the time when someone posts about creep and they can't even be bothered to comment as to whether the HST is adjusted properly.

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    Centercut
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    Ahhh, my mistake. But I still stand by my statement based on actual real world experience. And that is with gun tuned properly, find plateau, back off to the knee of the curve, etc. But hey, it’s ok to disagree… ;) PS., I appreciated and agreed with the article you linked to above. My observation was even at the sweet spot you still get variations in pellet velocity with changes in reg pressure. Try it sometime on your FX Crown or Impact where it’s easy to do. Shoot a few over the chrony. Jack up reg pressure 10 bar. Shoot a few more. What happened to pellet velocity without changing anything else? Yes, even on a perfectly tuned gun…

    • This reply was modified 5 months ago by Centercut.
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    Motorhead
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    nervoustrig

    Actually I was agreeing with Scott.  It's not that creep isn't a problem with some regulators, it's that the extent of it is exaggerated by tunes that are not adjusted properly.  Just a couple of days ago I posted an explanation of how the self-regulation (bell curve) of a conventional PCP applies just as readily to regulated PCPs.

    https://www.airgunnation.com/topic/how-much-effect-of-a-consistent-regulator-on-accuracy/#post-529965

    It was met with crickets chirping, as it is much of the time when someone posts about creep and they can't even be bothered to comment as to whether the HST is adjusted properly.

    What MOST folks do not fully understand or grasp is the basic operation of a knock open valve.  Makes no difference if a conventional or regulated configuration, the base line being if valve has more pressure within, harder it will be to open or the reverse, less pressure easier to open.

     

    The issue that is not being grasped by so many self tuners is that IF YOU HAVE EXCESSES in hammer weight or EXCESSIVE spring force driving the hammer …. valve will respond by still fully opening at differing pressures.  That miens simply … If reg creeps and plenum has more pressure guns going to shoot faster PERIOD !

     

    The missed trick ( Those of us who are attempting to teach you already know this ) is finding that sweet spot where the hammers weight and spring rate driving it are near there peak of strike energy at a specific pressure. * In other words, if valve gets harder to open with a increase in plenum pressure due to creep there is no excess in hammer strike energy to overcome it and gun In simple terms shoots the same speed.

    THE REGULATOR allows the plenum to fill to a far more consistent pressure than a non regulated gun and come fills end … MORE consistent shots in the Fill / Refill range over a non reged gun.

     

    There is a lot more going on that is not getting stated here … And the link above provided by Nervoustrig is a worthwhile read if you actually wish to get a better grasp of what we're saying.

     

    Scott S

    Motorheads AG Tuning Services

    • This reply was modified 5 months ago by Motorhead.
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    nervoustrig
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    Centercut, I don’t  know that we disagree, we just aren't laying out all the specifics.  The devil is in the details.  I touched on it in the linked thread…the extent to which a particular gun is insensitive to pressure variation (creep) has to do with the myriad of parameters that affects an unregulated PCP's ability to self-regulate over a wide pressure range.  In other words, there is a natural bell curve that centers on a particular pressure, and for a couple hundred PSI in either direction it will hold the same velocity (tight ES).  However when we tune a regulated PCP, we often do not know where that optimum pressure is.  Instead we usually pick a velocity we want and then go for it, using whatever knobs and dials are at our disposal.  So it's no surprise when the gun isn't quite so agnostic to creep, especially in cases where a gun is hot-rodded to much higher FPE.

    In terms of the example you gave, I think that's a perfectly valid point.  Changing the setpoint even 10 bar may well alter the velocity and POI.  However the extent to which it does all goes back to that natural balance of HST, hammer weight, stroke, porting, and valve return spring.  If the 10 bars lies within the gun's natural bell curve of self-regulation, it will make no difference.  If it doesn't, then the velocity and POI will change.

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    Centercut
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    Good explanation. Fully understand computational fluid dynamics, it’s what I did for a living. And I do agree if tuning services, expertise, time, materials, etc are available and implemented, you are correct. My point is that tuning a Cricket or Crown with the Stock valve, stock spring, and stock hammer weight, and the gun tuned as described for a given reg pressure, increasing pressure will increase velocity. I’ve done this with a Daystate, FX, Cricket, Vulcan and EDgun. Adjust HST to plateau. Back off to the knee of the curve. Shoot. Increase reg pressure 10 bar. Shoot. Velocity increase in each and every case. Usually 30 to 40 FPS. However, this is only my observed experience, and being a nuclear engineer I may have overlooked something…  

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    Motorhead
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    Which brings up a statement to regurgitate …. finding that sweet spot where the hammers weight and spring rate driving it are near there peak of strike energy at a specific pressure.

     

    That is many cases will deviate from the factory supplied hammers weight & spring rate  ….. leading to, actually tuning and not just adjusting stuff.

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    Centercut
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    Bingo. But that is beyond the capacity or capability of most that post about reg creep. So I think we’re all in agreement. :)

    FYI, this increase with reg pressure is even true with a Daystate Harper Slingshot valve which supposedly has a very flat bell curve.

    • This reply was modified 5 months ago by Centercut.
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    PerkyVal
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    Oh my!

    You guys with your big brains put me to shame. I can barely understand how to make coffee, let alone actually do it.

     

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    Motorhead
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    Lets visit the basic COWBOY COFFEE ….. Dump liberally an amount of ground/ beat down etc coffee beans into a Tin cup,  ADD boiling water & let sit just long enough to not scald lips or tongue.

    Drink straining coffee grounds threw your teeth … Refill  with hot water & repeat.

     

    Simple really … LOL

    • This reply was modified 5 months ago by Motorhead.
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    nervoustrig
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    Well, I just hope I know as much as Scott when I get that old.  :)

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    PerkyVal
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    Motorhead

    Lets visit the basic COWBOY COFFEE ….. Dump liberally an amount of ground/ beat down etc coffee beans into a Tin cup,  ADD boiling water & let sit just long enough to not scald lips or tongue.

    Drink straining coffee grounds threw your teeth … Refill  with hot water & repeat.

     

    Simple really … LOL

    That's what I mean about a big brain!

    Who would have ever thought you needed water, or that it needs to be hot?

    Imagine my suprise when I bought a can of coffee and it was filled with dark sawdust.

    It sure doesnt come like that at Starbucks.

     

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    zx10wall
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    Take a non-regulated, beautifully tuned PCP that delivers a killer bell-curve of 30 fps extreme spread over 35 shots. The above mentioned performance all occurs when said non-regulated PCP is filled to 205 bar max and shot down to 130 bar. 

    Fill this same beautifully performing PCP to 250 bar and watch valve-lock take over. It’s going to shoot low POI and velocity until the pressure drops. This is because the set hammer strike cannot now properly open the valve as it requires more force with the added pressure.

    A regulated system allows one to fill to much higher pressure such as 250 bar or higher and never experience valve-lock. This is because the pressure that the valve is subjected to is now limited by the regulator controlling it.

    Take a well tuned regulated PCP that can perform very well for 50 shots producing a standard deviation of 3 fps and an extreme spread of 10 fps. All this said performance is with a max fill of 250 bar and regulator set to 135 bar.

    If this regulated PCP has regulator creep, the regulator’s piston seat bleeds by and is not sealing properly due to one problem or another. This system that once performed so well, being that the pressure in the plenum and on the valve was regulated to 135 bar, could now be subject to much higher creeping pressures of well over 200 bar. This will usually occur, once the reg has the issue, after the gun sits for a good length of time. The first few shots will have valve-lock like symptoms (low POI and velocity) until the pressure is regulated again.

     

     

    • This reply was modified 5 months ago by zx10wall.
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    Eaglebeak
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    For anybody that is interested and can follow Technical detail, there is a series of articles in Hard Air Magazine that explain what nervoustrig has been banging on about as well as the advantages and disadvantages with regulated PCPs. Too many people believe that regulators are magic wands and can be installed in any unregulated gun and set to the centre of their velocity plateau pressure, without any other tuning and it will magically increase their shot count, power and accuracy. Instead of me trying to put into words that will be misunderstood, just look up those articles.

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    Saltlake58
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    Eaglebeak

    For anybody that is interested and can follow Technical detail, there is a series of articles in Hard Air Magazine that explain what nervoustrig has been banging on about as well as the advantages and disadvantages with regulated PCPs. Too many people believe that regulators are magic wands and can be installed in any unregulated gun and set to the centre of their velocity plateau pressure, without any other tuning and it will magically increase their shot count, power and accuracy. Instead of me trying to put into words that will be misunderstood, just look up those articles.

    Aint that the truth.  I regulated a Marauder, and am still working on the accuracy part.  The regulator only gives a more consistent air pressure to work the rest of the accuracy equation including stuff like, twist rate, pellet weight, pellet BC, distance to target harmonics, and more.  The regulator just reduces the variability of air pressure (One of many elements), reducing one element in the accuracy equation!

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    Greenarrow
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    Eaglebeak

    For anybody that is interested and can follow Technical detail, there is a series of articles in Hard Air Magazine that explain what nervoustrig has been banging on about as well as the advantages and disadvantages with regulated PCPs. Too many people believe that regulators are magic wands and can be installed in any unregulated gun and set to the centre of their velocity plateau pressure, without any other tuning and it will magically increase their shot count, power and accuracy. Instead of me trying to put into words that will be misunderstood, just look up those articles.

    Maybe these are the articles that you were referring to?  Thanks for the heads up.

    Here is a link should anyone be interested.  Good stuff there to study.  

    https://hardairmagazine.com/category/ham-columns/airgun-technical/

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