Does the reservoir act as pseudo plenum when pressure drops below reg set point?

[FuzzyGrub]

In my findings, the difference between a regulator with a very restrictive orifice that marginally feeds your plenum opposed to a larger orifice that feeds your plenum enough to act as a partial auxiliary plenum, is noteworthy, even more so as you increase caliber or power output. The smaller the plenum is relative to your power output, the more noteworthy. Even in my configuration, with 53 cc, my peak output is currently 64 fpe at sub 2k regulated only because my plenum is partially fed by my reservoir during the shot cycle..if I were to plug my regulators feed holes to where the air flow was negligible, I would likely have a power output of 59 fpe being sub 2k psi regulated...

Having listened to Bob over the years, the gold standard of 1cc of plenum to one FPE of output, echos in my head.  But have definitely gone down to 1/2cc per, with good results.   In your case, it seems like all the work on the reg, only saved about 5cc's of plenum.   Bumping the reg up 50psi would be the next option.  Offhand, just doesn't seem worth the additional design/testing effort.  We all have our areas we like to dig in on.     

Just for clarity. do you build your own regs, or modifying a production one?   Some of the pictures you posted looked like Lanes, but haven't used that one. 

[PikeP]

In my findings, the difference between a regulator with a very restrictive orifice that marginally feeds your plenum opposed to a larger orifice that feeds your plenum enough to act as a partial auxiliary plenum, is noteworthy, even more so as you increase caliber or power output. The smaller the plenum is relative to your power output, the more noteworthy. Even in my configuration, with 53 cc, my peak output is currently 64 fpe at sub 2k regulated only because my plenum is partially fed by my reservoir during the shot cycle..if I were to plug my regulators feed holes to where the air flow was negligible, I would likely have a power output of 59 fpe being sub 2k psi regulated...

Having listened to Bob over the years, the gold standard of 1cc of plenum to one FPE of output, echos in my head.  But have definitely gone down to 1/2cc per, with good results.   In your case, it seems like all the work on the reg, only saved about 5cc's of plenum.   Bumping the reg up 50psi would be the next option.  Offhand, just doesn't seem worth the additional design/testing effort.  We all have our areas we like to dig in on.     

Just for clarity. do you build your own regs, or modifying a production one?   Some of the pictures you posted looked like Lanes, but haven't used that one. 

I use lanes, but I plan on modifying his piston one day to allow a larger od seat / more air flow during the shot cycle in the future...but for now I am very happy with the overall design..

Fwiw, your estimate on 5 cc's is wildly wrong, as well as 50 psi...to hit the numbers that I do, most people will run 200-300 more psi than I currently do..provided their reg isn't feeding the plenum well enough during the shot cycle. I would also have to double my plenum volume to be able to hit the 64 fpe again if I were to plug my reg so it cannot feed anything into my plenum during the shot cycle

Below, pictured on the left is a plenum that is fed very well during the shot cycle by the reservoir, on the right, one that is not...the closer to 1 cc per fpe the less noticeable this effect...but for very small plenums, this effect is quite dramatic. (1975 regulated, 19.5" barrel .225" porting (.23" valve that transitions into .225" barrel port) 53cc plenum 33.95gr jsb)

[nervoustrigger]

Ray, to your question regarding what happens as input pressure and output pressure reach a parity, the seat will be just barely held closed.  As soon as some air is lost from the plenum (i.e. its pressure drops), the seat will open up ever so slightly.  As the pressure continues to fall, the seat will open more and more until it is fully open.
 
Note the amount by which it opens is not a function of output pressure versus input pressure, but output pressure vs atmosphere.  In other words, I'm trying to emphasize the state of the valve seat has nothing to do with a balance between input and output.  It's a difference between the output pressure and the world around it.  That's how a fixed spring force achieves a stable output pressure independent of the input pressure.

[FuzzyGrub]

I think of reg fill times in the 1-3 sec timeframe to the 1-2 millisec of the shot cycle.   Doubling the flow rate would seem to only provide 1/100 of assist during the shot cycle.  Quadrupling flow, still seem to provide very marginal gains.   Making up for a magnitude difference is hard.    We do like our challenges. 

[PikeP]

I think of reg fill times in the 1-3 sec timeframe to the 1-2 millisec of the shot cycle.   Doubling the flow rate would seem to only provide 1/100 of assist during the shot cycle.  Quadrupling flow, still seem to provide very marginal gains.   Making up for a magnitude difference is hard.    We do like our challenges. 

I love how you interject thoughts into this with no basis or supporting evidence...I won't debate you here, nor will I try to further explain the process. I already laid out the variables that determine the process, and here you go la-di-da-ing your way into a complex calculation with these off the wall numbers. 1/100th of assist during shot cycle? Okay bud, thanks for educating me today.

[nervoustrigger]

What Matt is very politely trying to say is that the contribution is not linear with time.  The pressure differential is augmented greatest at the beginning and tapers off toward the end.

[AlanMcD]

There's no reason to get snotty here . . . .

I for one agree with John - and yes, maybe the approximation is too much of an approximation for some people's tastes - but I doubt you are getting anywhere near the "assist" you seem to think you are while on the regulator.  Having watched Lane's videos, his regs don't respond that fast, at least as he makes them.  Maybe your customized one does, but answers around your custom high flow reg won't assist the OP in understanding his situation . . . .

I concede that you are probably getting more "assist" than the rest of us while off the regulator.  The fact that you are does not mean that the rest of us did not read the OP's actual post, or that what we shared was factually incorrect in the data we have been able to collect.  I stand by what I said on mine - I get almost the exact same response on and off the regulator.  The response gets better when I am way off the regulator, but I only went there once in testing; I have no idea why someone that has a regulated gun would want to shoot it that far below the reg set point.

Again, in general, when a regulator is installed it will significantly impede the flow of air from the unregulated space into the plenum during the shot cycle.  This is especially true when on the regulator, but even true off the regulator.  One can test it by shooting at the various pressures with and without the regulator installed and note the significant difference in power, due to the pressure drop in the plenum during the shot cycle.  Maybe some air gets through, but in general, the gun does not act as though there is no regulator in the reservoir when shooting below the set point.  And if the dwell is long enough to let a lot of air through, then that is more like venting air than using it to generate power.

[Motorhead]

All I'm going to say is this .... ANY REGULATOR WORTH OWNING and one in the same being it can hold GOOD SET POINT ACCURACY will have a small to very small seat & orifice and absolutely in this realm of accurate and precision regulators the anwser to OP's question is NO !!

That's all folks ... ^*%$#@ contest i won't get into here.

[FuzzyGrub]

Sorry if I don't have an accurate way of measuring the fill times, outside of watching plenum gauge.  Mostly filled in 1 sec, and a couple seconds to settle out.  I do think that is in the ballpark.  Call it a second.  The problem is the shot cycle time, which you even gave a range.  I'm not sure how to measure that, but seems reasonable.  You need very significant increase in flow to help during that time frame.  If you can take an existing reg design and get double or quadruple out of it, that is a significant improvement in overall time, just not much within a millisecond.   Wasn't trying to be sarcastic, etc, just seems like quite the challenge.  Its good to see people who are not afraid of hard problems.   I'll go back to my own sandbox. 

[UnderPressure]

Here are the volumes for a 22.75" long barrel in .177, .217 and .25:

.177 = 9.2cc
.217= 13.8 cc
.25 = 18.3 cc

Assuming a 5cc plenum with a 6cc valve volume having the valve close when the projectile is half way down the barrel would result in the following pressure drops:

.177 = 6+5 / 6+5+4.6 = .705 (So 29.5% pressure drop)
.217 = 6+5 / 6+5+6.9 = .6145 (So 38.55% pressure drop)
.25 = 6+5 / 6+5+9.15 = = .546 (So 45.4% pressure drop)

[UnderPressure]

All I'm going to say is this .... ANY REGULATOR WORTH OWNING and one in the same being it can hold GOOD SET POINT ACCURACY will have a small to very small seat & orifice and absolutely in this realm of accurate and precision regulators the anwser to OP's question is NO !!

Apparently PikeP's Lane regulator does not creep despite the large seat and orifice:

https://www.airgunnation.com/topic/do-regulators-need-breaking-in/#post-184836

My regulator settled after about 100-200 shots. I have a Robert Lane reg as well and many of his designs do not use a bellvue washer stack and use a very stiff compression spring as well. I experience no creep with the rifle sitting unused.

[UnderPressure]

In my findings, the difference between a regulator with a very restrictive orifice that marginally feeds your plenum opposed to a larger orifice that feeds your plenum enough to act as a partial auxiliary plenum, is noteworthy, even more so as you increase caliber or power output. The smaller the plenum is relative to your power output, the more noteworthy. Even in my configuration, with 53 cc, my peak output is currently 64 fpe at sub 2k regulated only because my plenum is partially fed by my reservoir during the shot cycle..if I were to plug my regulators feed holes to where the air flow was negligible, I would likely have a power output of 59 fpe being sub 2k psi regulated...

Having listened to Bob over the years, the gold standard of 1cc of plenum to one FPE of output, echos in my head.  But have definitely gone down to 1/2cc per, with good results.   In your case, it seems like all the work on the reg, only saved about 5cc's of plenum.   Bumping the reg up 50psi would be the next option.  Offhand, just doesn't seem worth the additional design/testing effort.  We all have our areas we like to dig in on.     

Just for clarity. do you build your own regs, or modifying a production one?   Some of the pictures you posted looked like Lanes, but haven't used that one. 

I use lanes, but I plan on modifying his piston one day to allow a larger od seat / more air flow during the shot cycle in the future...but for now I am very happy with the overall design..

Fwiw, your estimate on 5 cc's is wildly wrong, as well as 50 psi...to hit the numbers that I do, most people will run 200-300 more psi than I currently do..provided their reg isn't feeding the plenum well enough during the shot cycle. I would also have to double my plenum volume to be able to hit the 64 fpe again if I were to plug my reg so it cannot feed anything into my plenum during the shot cycle

Below, pictured on the left is a plenum that is fed very well during the shot cycle by the reservoir, on the right, one that is not...the closer to 1 cc per fpe the less noticeable this effect...but for very small plenums, this effect is quite dramatic. (1975 regulated, 19.5" barrel .225" porting (.23" valve that transitions into .225" barrel port) 53cc plenum 33.95gr jsb)

Sounds like something that could be interesting for JSAR Raptor HP (.257) and JSAR Raptor 357.....but also to boost the unregulated operation.

[Motorhead]

Your MISTAKING Creep for set point ACCURACY.    If reg stops flowing at say 1850 and does not creep from thats great which is what your stating, but if regulator cycles and holds +/- 50-100-150 psi with each reset w/o creeping your ES has gone to shite.

Big seats, large orifice & side intake regs simply don't have the resolution of a definitive set pressure not changing with HPA storage pressure and those in the know realize this.  For most a non issue, but those who understand and require such set point accuracy over a broad HPA storage pressure the CAUSE & EFFECT of higher flowing designs are well known.

Not Poo pooing ... just a matter of fact reality.

Scott S

 

[rsterne]

I'll throw in a quick calculation here.... Using the 66 FPE of those graphs as what happens with a plenum/reservoir of 3 cc per FPE or larger (212 cc / 66 FPE = 3.2), and further using the assumption that the efficiency is only 1.00 FPE per CI.... and using a setpoint pressure of 1975 psi (136 bar), at that pressure we would be using (66 x 16.4 / 136) = 8 cc of HPA.... Starting with a plenum of 53 cc, starting at 1975 psi, if we remove 8 cc for the shot, with NO top-up during the shot cycle, the remaining pressure is [(53-8) / 53] x 1975 = 1677 psi, and the average pressure would be 1826 psi.... That should produce at least (1826 / 1975) x 66 = 61 FPE.... If we cut the plenum in half to 27 cc, and still use the same volume of air (8 cc at 1975 psi), the average pressure would be 1682 psi, producing at least 56 FPE.... This is close to a plenum of 1/2 cc per FPE, about as small as practical with a conventional regulator.... With a plenum of just 14 cc, and still using 8 cc at 1975 psi, the average pressure would be 1410 psi, producing at least 47 FPE.... Note that these conservative numbers are higher than the right hand graph presented by Matt....

The reason I say that the FPE should exceed the numbers above is that as the plenum gets smaller, and the average pressure decreases, the gun will use less than the 8 cc of HPA per shot used in the pressure calculations.... That will mean a higher average pressure, and greater FPE.... If that did not occur, by the time you got down to the 14 cc plenum, if you were still using 8 cc of 1975 psi air (66 std. CI) to produce 47 FPE, the efficiency would be down to just 0.71 FPE/CI.... While efficiency does drop as you decrease the plenum size, it doesn't drop that drastically.... In addition, the starting efficiency I used of 1.00 FPE/CI is likely lower than what you might expect.... The higher the efficiency, the less air is used per shot, and the less the pressure drops as you decrease the plenum volume.... We know from experience that using a plenum of 1/2 cc per FPE with a conventional regulator (slow refresh rate) you need about a 10% increase in setpoint pressure to maintain the FPE....

Matt was trying to make the point that if the regulator has a fast refresh, then it helps to keep the pressure up in the plenum, which of course is correct.... It makes the plenum act as though it was larger in volume.... You may still have to increase the setpoint pressure to make up for a really small plenum, but not as much as with a conventional regulator which may take several seconds to bring the plenum back to full pressure.... What the flow rate is through that 4mm hole in the piston actually is, depends on how far and how fast it opens during the shot cycle.... It would need to open at least 1 mm to achieve full flow, and that flow rate would still only be 49% of the flow through a 0.225" port.... Using the 14 cc plenum as an example, to maintain 55 FPE (as in the left graph) needs an average pressure of 1646 psi.... I have no idea if the Lane regulator can open 1 mm in 1 mSec with a pressure drop on the output side of just 330 psi, but that is about what would be required.... If the FPE numbers on Matt's left graph for the 7cc and 14cc plenums are measured data, and not calculated, then I am very impressed.... As Motorhead says, however, consistency of setpoint pressure as the reservoir pressure changes is not one of the strong points of a side-flow regulator design with a large seat area.... As long as the Lane regulator can maintain a (nearly) constant output pressure from full reservoir pressure down to the setpoint, then no reason it should not be an improvement....

To answer the original question, a conventional regulator, which uses a HP port of about 1-1.5mm, will not allow the HP reservoir to increase the plenum volume by a noticeable amount even when the pressure is below the setpoint and the regulator is open.... The Lane style, once the pressure drops enough to allow it to open 1 mm, should flow about half what the ports can, and so should add some pseudo plenum volume....

Bob

[Wayne52]

The only way to be able to tell exactly where the pressure of the regulator output is sufficient would be to have two gauges, one for filling the gun and one for showing the regulated pressure.  These gauges would have to read exactly the same under the same pressures. Once the reg isn't closing both gauges would start reading the same after each shot on a downward pressure.  I'd simply say that once you are down to what you might think the regulated pressure is it's time to refill the gun.  This is actually the first time I've read this thread and just seeing the title to this thread put a BIG question mark in my head. 

[Ribbonstone]

HAve to agree that shooting past the reg-set pressure pretty well negates the whole reason for having regulation in the first place.

IF it is off reg set...then the reg is open....and all it does is act like a flow restriction.  Whatever the speed of the regulator's cycle, it's not cycling.

All the regulator is doing at that point is acting like a restriction (lets say a too-complicated gauge block with a tiny hole).

A penalty for high power regulationtunes...maybe not for lower power.

[UnderPressure]

Your MISTAKING Creep for set point ACCURACY.    If reg stops flowing at say 1850 and does not creep from thats great which is what your stating, but if regulator cycles and holds +/- 50-100-150 psi with each reset w/o creeping your ES has gone to shite.

Big seats, large orifice & side intake regs simply don't have the resolution of a definitive set pressure not changing with HPA storage pressure and those in the know realize this.  For most a non issue, but those who understand and require such set point accuracy over a broad HPA storage pressure the CAUSE & EFFECT of higher flowing designs are well known.

Not Poo pooing ... just a matter of fact reality.

Scott S

 

Thanks for explaining that.

Maybe instead of having a Lane regulator with modified orifice greater than 4mm in diameter a person could have two lane regulators (with 4mm orifices) operating via a dual tank adapter?

2 x 4mm orifice would have 82% of the area of a .250 transfer port.

[PikeP]

Here is both a ninja style reg (actually raptor in yellow) versus my marauder with lane (in blue) prior to buffering out both pellet weight and valve lift



What you will see, if you observe well enough, is that both tunes have a slight cliff through the shot string, while the first half is mostly above the trend line, the second half is mostly below...odd how physics applies to both regulators equally...even more odd that both can be dealt with via proper tuning...

Here is my most recent tune...it speaks for itself..

[PikeP]

Your MISTAKING Creep for set point ACCURACY.    If reg stops flowing at say 1850 and does not creep from thats great which is what your stating, but if regulator cycles and holds +/- 50-100-150 psi with each reset w/o creeping your ES has gone to shite.

Big seats, large orifice & side intake regs simply don't have the resolution of a definitive set pressure not changing with HPA storage pressure and those in the know realize this.  For most a non issue, but those who understand and require such set point accuracy over a broad HPA storage pressure the CAUSE & EFFECT of higher flowing designs are well known.

Not Poo pooing ... just a matter of fact reality.

Scott S

 

Thanks for explaining that.

Maybe instead of having a Lane regulator with modified orifice greater than 4mm in diameter a person could have two lane regulators (with 4mm orifices) operating via a dual tank adapter?

2 x 4mm orifice would have 82% of the area of a .250 transfer port.

One could easily just run a 6 mm regulator seat too...or be happy with flowing between 50 and 75% or so of the capacity of your forward porting.

The flow out of a.250 port would be regulated and be of lower pressure than the flow through your 4mm regulators refresh orifice which would be fed by much higher pressure air through the majority of your shot series/string...meaning that pressure difference through most of your shot string, helps make up for the size difference in the two's ports.

Another way to look at it, is the percentage of flow your regulator can flow compared to what your valve flows, essentially increases your plenum volume by that same percent...so if you run a 10cc plenum, and have a regulator that can flow 50% of the forward porting capacity, and you want to calculate some internal ballistics for your air gun with...you're essentially going to have calculate using a 15 cc plenum...

Or in other words, your plenums effective volume, is equal to itself, plus its own volume multiplied by the percentage of its flow rate compared to that of your valves flow rate...

[PikeP]

I am pretty sure, no one here is qualified, nor has the equipment or capacity required, to test the shot to shot precision of a regulators set point with a 1mm seat, versus one with a 4mm seat...I am pretty sure Robert Lane does, and has tested his own design to be within a margin he finds acceptable...

I am also quite confident, that I have seen enough strings, and their minor cliffs through-out, with both ninja and huma regs, to conclude they are not superior in the sense of a regulators precision or resolution, and I happen to be 'in the process of soaking up information and learning'...as opposed to 'in the know' so excuse my open minded approaches as I explain...

All you need to do, for either regulator style, to obtain more consistent shot to shot energy output/release from your valve, is introduce methods of buffering out variation, be them valve springs, valve lift buffers, valve stems with appropriate closing force for your application, and weigh your pellets to within 1.5% or so of labeled weight. Simple.