How does a regulator work on a gun w/multiple power settings?

[GD Giles]

Let's pick the Hatsan Gladius .22 long as the discussion subject. 

It has 6 power settings from the factory. You could put an aftermarket regulator in the BT65 sized cylinder for more consistency in the shot string and more economical usage of air but aren't those adjustments made based off one setting on the six level power selector? What happens if you select a different power level after you've put in a regulator?

[Motorhead]

All the regulator does is stabilize pressure within plenum / valve so the shot to shot consistency is better controlled.
The miens used in manipulation used to control power/ velocity remains the same.

[nervoustrigger]

Usually the power adjustment isn't the regulator setpoint.  Typically it's either something that restricts air flow through the valve exhaust or transfer port, or it's something that adjusts the hammer strike.

[GD Giles]

So I think you're saying if the hammer strike is adjusted then even if the regulator is set at a specific level in conjunction with a particular setting on the power adjustment on the gun less air is used because not all of it leaves the regulator since the opening time or distance for the valve is decreased? I think I also saw somewhere that on the Gladius the adjustment is not hammer spring but rather valve related. Anyone have some insight on that?

Or, what happens when you put a regulator into one of these guns on all 6 power levels? What are the benefits, what would the potential upticks in performance be?

[nervoustrigger]

Between those two methods, restricting airflow is better for consistency.  When you adjust the hammer strike, especially to detune a lot, you get to the point where the valve is barely opening and the velocity becomes inconsistent.  Often it's not much of a problem in practice because typically one would detune for short range shooting (say, 10 - 25 yards) and the extreme spread doesn't make a huge difference in the POI but may dramatically increase shot count and reduce noise.

For example, I took a 30fpe .22 cal and adjusted the hammer spring preload to detune it to 13fpe for a little suburban squirrel hunt.  It went 6 for 6 that morning and was just silly quiet in doing so.

As far as the potential benefits of adding a regulator to a rifle that has adjustable power, it's the same as one that does not have a power adjustment.  The valve always has a consistent air pressure acting on it so the velocity and trajectory will be more consistent, other things being equal.

[rsterne]

In a regulated gun, unless the power adjuster is changing the output pressure, the two usual methods available are hammer strike (preload or travel) or transfer port size.... If you adjust the hammer strike, increasing it above the ideal setting only wastes air, with little or no increase in velocity.... Obviously that won't adjust the power.... Going to less hammer strike, by the time you reduce the power by any substantial amount (ie worth doing it at all), you will be operating like an unregulated PCP, but without the high pressure (initial low velocity) part of the shot string.... In other words, once you reach the setpoint, the velocity will INCREASE before falling off.... That may not matter to you, if you refill at or above the setpoint, and the gun will be quite efficient, but as Jason said, if you go too far, you may have a wide ES.....

Finding the ideal hammer strike to operate on the "knee" of the curve, and then adjusting the diameter of the transfer port to change the power, is IMO a much better way to go.... The gun stays consistent in ES, and you can dial the power down as far as you like, increasing the shot count as you do.... However, you are not likely to see a huge increase in efficiency using that method....

One other method, using an adjustable hammer stop to reduce power.... while it doesn't work well in an unregulated PCP, because is causes a decreasing shot string.... may work fine on a regulated PCP, although I haven't tried it.... It should reduce the power by decreasing the valve lift, but since the lift can't increase when the pressure drops below the setpoint, might give you the best of everything.... less power, stable velocities, and increased efficiency....

Bob

[LDP]

I will use the S510 as an example because its what I have and what I have played with. The S510 power wheel adjusts the TP size not the HS. After adding a new reg to my S510 I tuned it with the power wheel set at max power. If I lower the setting it does decrease power and stays consistent but you dont really gain any shots. I believe the gladius works the same way in that it adjusts the TP to adjust the power. So even with a regulator you can adjust the power but dont expect a big change in shot count.

[Motorhead]

I will use the S510 as an example because its what I have and what I have played with. The S510 power wheel adjusts the TP size not the HS. After adding a new reg to my S510 I tuned it with the power wheel set at max power. If I lower the setting it does decrease power and stays consistent but you dont really gain any shots. I believe the gladius works the same way in that it adjusts the TP to adjust the power. So even with a regulator you can adjust the power but dont expect a big change in shot count.

Reason this is so .....

With pressure valve is operating at staying the same ...
Hammer Weight & strike energy remaining the same ...

The amount of air released based upon Lift and Dwell remains mostly consistent tho DIFFERS in the delivery duration it has getting behind pellet.

Think of it along the line of having FULL GLASS OF WATER & this amount of water is used every shot ....
Now pour water down a garden hose size tube and then down a straw.
YUP, bigger the path water flows threw, faster it is gone which equals in a PCP MORE POWER because the maximum energy of the valves discharge got to pellet quickly.

The soda straw size tube ( Which is equivalent to a choked down transfer tube ) still delivered the same volume, but over a longer time span.  Which because it happens slower the power become less tho you still end up using nearly the same amount of air.  ( There is an air savings, but nothing like other miens to the same end )

Scott

[nervoustrigger]

Yeah, to add to what Scott is saying, the ability of restricting the transfer port to also reduce air usage will have a lot to do with how much volume exists between the valve seat and the restrictor.  It's not very practical to manipulate that volume so this is something of an academic point, but just to explore the idea it may be useful.

In other words, when the valve knocks open, air rushes fairly unimpeded to fill the volume between the valve seat and restrictor.  But those air molecules have to line up and go single file past the restrictor.  Meaning by the time all of them make it through, the pellet is so far down the barrel that they do little to nothing to accelerate it.  Thus wasted air. 

[thespardian]

I will use the S510 as an example because its what I have and what I have played with. The S510 power wheel adjusts the TP size not the HS. After adding a new reg to my S510 I tuned it with the power wheel set at max power. If I lower the setting it does decrease power and stays consistent but you dont really gain any shots. I believe the gladius works the same way in that it adjusts the TP to adjust the power. So even with a regulator you can adjust the power but dont expect a big change in shot count.

Reason this is so .....

With pressure valve is operating at staying the same ...
Hammer Weight & strike energy remaining the same ...

The amount of air released based upon Lift and Dwell remains mostly consistent tho DIFFERS in the delivery duration it has getting behind pellet.

I think, the power adjuster wheel of my Bobcat MK-II adjust the TP only. I have 70 plus regulated shots at full power (33+FPE) but when i adjust the wheel for 12 FPE the shot count dramatically increase.
If i am right about the function of power adjuster, I wonder, the hammer strike and set point pressure is same for each setting but the shot count bumps up in case of 12 FPE.

I refrain myself to get  a full string at 12 FPE. JSBs are rear and expensive here.  But i'll do it. I want to see whether i get a sudden spike when the gun came off the regulator.   

[thespardian]

I think, the power adjuster wheel of my Bobcat MK-II adjust the TP only. I have 70 plus regulated shots at full power (33+FPE) but when i adjust the wheel for 12 FPE the shot count dramatically increase.
If i am right about the function of power adjuster, I wonder, the hammer strike and set point pressure is same for each setting but the shot count bumps up in case of 12 FPE.

I refrain myself to get  a full string at 12 FPE. JSBs are rear and expensive here.  But i'll do it. I want to see whether i get a sudden spike when the gun came off the regulator.   

Sorry for the stupid question which has already been answered by Bob the great

Finding the ideal hammer strike to operate on the "knee" of the curve, and then adjusting the diameter of the transfer port to change the power, is IMO a much better way to go.... The gun stays consistent in ES, and you can dial the power down as far as you like, increasing the shot count as you do.... However, you are not likely to see a huge increase in efficiency using that method....

Bob, if i am already on the knee of curve. To reduce the power, all i need to do is "reduce the TP size". No need to adjust the Set Point Pressure. In such circumstance, I'll notice a huge spike when it comes off the regulator. Am i right? 

[rsterne]

If you are on the knee of the curve, reducing the TP size will NOT cause a spike in velocity below the setpoint.... You will have the same profile shot string, just at a lower velocity.... I have found that on regulated (or unregulated) PCPs that reducing the TP size DOES increase the shot count, because the product of the FPE per shot and number of shots stays relatively constant.... same total FPE, same efficiency.... That means you can go from, for example 20 shots at 50 FPE to 50 shots at 20 FPE (still a total of 1000 FPE).... Generally, if your highest power tune is quite powerful, decreasing the FPE, at least initially, also results in a slight increase in actual efficiency, so you might actually pick up more shots than the straight FPE conversion would indicate.... That is certainly the way my regulated PCPs work out, anyway....

While some are postulating above that the amount of air being released per shot remains the same, I disagree.... The valve is open for a finite TIME.... If the pellet has not travelled as far down the barrel in that amount of time (because the velocity is lower), then the volume of HPA released by the valve is less.... Think of it as "backpressure" behind the pellet if you like, but in reality it is just the amount of barrel volume uncovered by the moving pellet in the dwell period of the valve.... That is why you can trade off FPE for shot count on (generally) a 1 for 1 basis (ie same total FPE).... If the gun is tuned just below the plateau at high power (eg. the valve is closing when the pellet is halfway down the bore), it isn't getting much of a boost from the expansion of the air after the valve closes.... If you choke up on the transfer port, and slow down the bullet so that it has only moved 1/4 of the way down the bore when the valve closes.... then the air trapped in the barrel after the valve closes still have 3/4 of the barrel length to expand, adding to the efficiency of the shot....

While I am not arguing that you can increase the shot count as much by restricting the transfer port as you can by reducing the dwell (less hammer strike).... you should still be able to count on a direct trade off between FPE and shot count from restricting the transfer port.... The only exception will be if you choke the port down to the point where the velocity is very low (ie under 500 fps), by which time the severe restriction you are imposing on the airflow starts to take it's toll on efficiency....

Bob

[nervoustrigger]

Bob, that is an excellent description...as usual.

Just to clarify my previous post, I would not expect air usage to be the _same_ with a restrictor in place, just not as miserly as adjusting hammer strike to achieve the same detuned energy level.

[rsterne]

100% correct, Jason.... Pretty much any PCP will trade off FPE vs shot count to achieve the same total FPE and the same total efficiency.... Doing better than that requires using tiny sips of high(er) pressure air.... like you get when running a regulated PCP on the "downslope" with less hammer strike and a higher pressure than you need to get that velocity.... Tuned like that is when you get an increase in velocity below the setpoint....

Bob

[nervoustrigger]

Got it.  Thank you, sir!

[LDP]

I didnt notice any real change in shot count by adjusting the power wheel on my S510 but I didnt make a large adjustment either. I only made a change of about 5-10 fpe so I was still above 20 fpe. One day I will crank it way down to about 12-14 fpe and see how much that changes it.

[rsterne]

It may be possible that if you are adjusted up on the plateau (excessive dwell) that you may not get the expected increase in shot count to keep the total FPE relatively constant.... I don't tune that way, so really don't know....

Bob

[LDP]

Its tuned on the knee so I should see a shot increase. It will be very easy to try and I actually get allot of shot opportunities where low power is ideal. So if I can gain some shots for low power pesting that will be a nice bonus. 

[thespardian]

Thanks for a detailed guide Bob.

[rsterne]

I was asked in a PM to explain my previous comments, and by the time I was done, thought more people could benefit if I posted it here.... so here goes....

For the most part, while the valve is open, the area between it and the pellet is pressurized to the same pressure as the reservoir, providing the ports are large enough to permit it.... The maximum amount of air that can be in the barrel when the valve closes is the barrel volume between the valve and the pellet, at reservoir pressure.... If the reservoir/valve volume is equal to the barrel volume, and starts at 3000 psi, then when the pellet reaches the muzzle, the most air that can be in the barrel is half the air that was in the reservoir, as the whole system will be at 1500 psi at that instant.... In a dump valve, all of the air will be lost, whereas if the valve closes at that instant, half will remain in the valve, which is why dump valves have lousy efficiency....

Let's use an example, of a regulated plenum of 20 cc at 1450 psi (100 bar), and a barrel of 20 cc (.25 cal and 25" long), with wide open ports (barrel pressure equals plenum pressure at any instant while valve open).... Pellet position when valve closes is a percentage of barrel length.... FPE/CI and FPE calculated assumes 60% overall efficiency (typical) using Lloyd's spreadsheet....

Dump shot uses all 20 cc x 100 bar = 2000 bar.cc.... residual muzzle pressure = 50 bar.... average pressure during shot 75 bar.... FPE/CI = 0.34 @ 42 FPE....

Valve closes at muzzle (100%).... half the air is still in the plenum, pressure is 50 bar.... air used is 1000 bar.cc.... residual muzzle pressure = 50 bar.... average pressure during shot 75 bar.... Same exact FPE in pellet, half the air used, so twice the efficiency.... FPE/CI = 0.68 @ 42 FPE....

Valve closes at 50%.... pressure is 2/3 x 100 = 67 bar.... air in barrel (used) = 1/3 of 20 cc = 667 bar.cc..... air remaining in plenum = 2/3 of 20 cc at 100 bar = 20 cc at 67 bar.... residual muzzle pressure is 67/2 = 33 bar.... average pressure during valve open stage (100+67)/2 = 83 bar.... average during remainder of shot (83+33)/2 = 58 bar.... FPE/CI = 0.91 @ 38 FPE....

Here is where you will have to trust me (and Lloyd's spreadsheet) a little bit.... The initial acceleration of the pellet is where most of the FPE is transferred to it.... It turns out that when you close the valve when the pellet is half way down the barrel, you will only lose about 5% of the maximum velocity you could get with a dump shot.... So you get about 90% of the energy, while using only 1/3 of the air of a dump shot, and 2/3 the air you would use if the valve closed at the muzzle.... PCPs that are operating efficiently have the valve close BEFORE the pellet has travelled halfway to the muzzle.... This is because the air trapped between the (closed) valve and the muzzle expands to continue to push on the pellet, greatly increasing the efficiency of the shot.... Really efficient PCPs will have the valve close when the pellet has only gone about 20-25% of the barrel.... By the time you get down to 10%, the gun is so quiet it is hard to believe, because the residual muzzle pressure is down to 1/10th the reservoir pressure.... Not much power, but very efficient.... Using the example above, here is what you could expect with different valve dwells.... still with wide open ports....

Dump shot yields 42 FPE @ 0.34 FPE/CI
100% yields 42 FPE @ 0.68 FPE/CI
50% yields 38 FPE @ 0.91 FPE/CI
33% yields 33 FPE @ 1.05 FPE/CI
25% yields 30 FPE @ 1.14 FPE/CI
20% yields 26 FPE @ 1.20 FPE/CI
15% yields 23 FPE @ 1.26 FPE/CI
10% yields 18 FPE @ 1.32 FPE/CI

OK, so now you understand the basics.... Let's use the example of a PCP with wide open ports, where the valve closes when the pellet is 1/2 way to the muzzle.... Now introduce a restriction between the valve and the pellet.... The valve is still going to stay open for the same length of time (it might actually close fractionally quicker, because the primary closing force is the pressure in the exhaust port pushing on the stem area, but we'll ignore that).... The restriction (smaller transfer port, for example) reduces the airflow to the pellet, and hence the pressure and acceleration of the pellet, which means it doesn't travel as far in the FINITE length of time the valve is open.... OK, so let's use Lloyd's spreadsheet to figure out what pressure at the pellet will give us the same 30 FPE that we can get above with wide open ports and the valve closing at 25%.... It turns out that 1150 psi is the magic number, if we keep the valve dwell the same.... With the restricted porting, the pellet has now moved 41% of the way down the barrel in the exact same time that it moved 50% with the wide open ports.... and the corresponding efficiency would be 1.02 FPE/CI.... Note this isn't as good as if we closed the valve with wide open ports at 25% (1.14 FPE/CI).... but it is actually better than the 0.91 FPE/CI we were getting at the 38 FPE power level....

Although the plenum had 1450 psi of air inside it, the restricted transfer port made the pellet act like it only saw 1150 psi, for the same length of time as before.... Lloyd's spreadsheet allows us to do one more thing.... It tells us how much air was used to create this shot.... It is 480 bar.cc, which has to be replaced by the regulator for the next shot.... With the wide open ports and 25% closing point, we used 425 bar.cc, which has to be replaced by the regulator for the next shot.... However, with the 50% dwell and wide open ports, we used 685 bar.cc for the regulator to replace....  Let's say the bottle feeding the regulator is 200 cc at 200 bar.... With our 100 bar setpoint, we have 200 x (200-100) = 20,000 bar.cc of air available.... This should give us....

20,000/685 = 29 shots at 38 FPE = 1102 FPE using the longer dwell and wide open ports
20,000/480 = 42 shots at 30FPE = 1260 FPE using the longer dwell and restricted transfer port
20,000/425 = 47 shots at 30 FPE = 1410 FPE using the shorter dwell and wide open ports

So using this example, and reducing the power by restricting the transfer port, we can expect AT LEAST the same total FPE at our lower power setting.... If we got the same total FPE with the restricted ports, we would get about 37 shots at 30 FPE (instead of 29 shots at 38 FPE).... The spreadsheet predicts we should actually do better than that.... The reason is, that we are starting from a relatively low efficiency of 0.91 FPE/CI at 38 FPE.... However, it reinforces the "rule of thumb" that in a PCP you should be able to trade off more shots at lower FPE and get the same total FPE.... The way to get the maximum efficiency, however, is to reduce the dwell to reduce the FPE....

Bob