Huma reg pressure creeping up

[Bladebum]

Hey guys, so I've had my daystate huntsman XL with the Huma reg for a couple months now. Mine came to me set at 150 bar and the velocity(and noise) showed that where I was pushing jsb 18s at 890. The shot count was 30-35.

I adjusted the hammer spring down to make the gun shoot 850-860 as well as get my shot count up around 40+ .

Recently was doing some bench shooting over the chrony and noticed some pretty wide spreads where some shots jumped over 900 fps...I've also noticed, that when the gun sits for a bit the reg pressure creeps a bit, and as of now its sitting at about 160 bar.

Anyone have any idea or advice on this? I've been wanting to take the gun apart and adjust the reg down but according to AOA that is a job and a half and the factory installed regs dont have markings so you really cant dial up or down without just guessing and hoping for the best.

Any advice or help on what to do here is greatly appreciated. 

[SILENT SQUIRREL]

following
and sending you a PM
Ed

[Motorhead]

if only months old ... WARRANTY

[SILENT SQUIRREL]

if only months old ... WARRANTY

Motorhead
Would it be advisable for Bladebum (the OP) to restore his hammer spring adjustment before sending the gun in for a warranty claim?
The Huntsman Regal XL does not have an external adjuster.
Ed

[Motorhead]

well that said ... was wondering how a reduction is HST was achieved

But then again if REG is not holding set point pressure potential exists velocity is going to drift about.

THO ... If the factory setting of HST and SET pressure was in SYNC slight changes in set point drift would be negligible.

Yup .. when you screw with settings you better have an understanding of cause & effect.

[Bladebum]

well that said ... was wondering how a reduction is HST was achieved

But then again if REG is not holding set point pressure potential exists velocity is going to drift about.

THO ... If the factory setting of HST and SET pressure was in SYNC slight changes in set point drift would be negligible.

Yup .. when you screw with settings you better have an understanding of cause & effect.

Scott, you obviously have much more understanding of this topic then myself. If I understand correctly a regulator is simply giving the same available amount of air from shot to shot. then by adjusting the hammer spring tension via more or less spring preload you then are choosing to hit the valve harder or less to use said available amount correct?

My logic is if I had 150 bar available,  i could adjust the hammer hit to the valve to use maybe say 125 bar each time thus dropping velocity. Up until the other week the gun was shooting with an ES of only a few fps, then had some spreads.  As far as accuracy goes, nothing changed there I have just noticed the reg pressure reading a touch higher, and it SEEMS to be right after I fill the gun when it stays a tap higher.

Adjusting the HST takes a minute to do, is it possible my "light" hammer strikes are causing the reg to act up?

FWIW I did mention how my gun came to me over the phone the other day with AOA and how high my velocities were. I was talking to none other than Kip P himself and he was surprised the gun was shooting so hot, so...maybe another call tomorrow is in order.

[SILENT SQUIRREL]

well that said ... was wondering how a reduction is HST was achieved
But then again if REG is not holding set point pressure potential exists velocity is going to drift about.
THO ... If the factory setting of HST and SET pressure was in SYNC slight changes in set point drift would be negligible.
Yup .. when you screw with settings you better have an understanding of cause & effect.

Scott, you obviously have much more understanding of this topic then myself. If I understand correctly a regulator is simply giving the same available amount of air from shot to shot. then by adjusting the hammer spring tension via more or less spring preload you then are choosing to hit the valve harder or less to use said available amount correct?

My logic is if I had 150 bar available,  i could adjust the hammer hit to the valve to use maybe say 125 bar each time thus dropping velocity. Up until the other week the gun was shooting with an ES of only a few fps, then had some spreads.  As far as accuracy goes, nothing changed there I have just noticed the reg pressure reading a touch higher, and it SEEMS to be right after I fill the gun when it stays a tap higher.

Adjusting the HST takes a minute to do, is it possible my "light" hammer strikes are causing the reg to act up?

FWIW I did mention how my gun came to me over the phone the other day with AOA and how high my velocities were. I was talking to none other than Kip P himself and he was surprised the gun was shooting so hot, so...maybe another call tomorrow is in order.

Hey Josh
Allow me to jump in and clarify a few things
It seems to me you are equating BAR with volume of air, instead of the compressed pressure of the air.
BAR = pressure, CC = volume
That said,it is my understanding from what I have read on the topic, that this is how it works
Let's assume the volume of air in  reservoir is pressurized to 200BAR , the regulator set at 150 Bar,  & the hammer spring at the stock setting
Each time the spring driven hammer hits the valve air is sent to the pellet at 150BAR resulting in velocity x
The volume air released is dependent upon how far the valve opens & how long it remains open.
Within limits:
When one adjusts the spring to be stronger the hammer hits the valve harder and opens it wider and the valve also has further ( takes longer) to close
The air released to the pellet is still at a 150 Bar pressure however the greater volume of air  presented to the pellet increase the velocity to x+
Again, within limits
The opposite holds true should the valve spring be made less powerful
The valve does not open as wide, and does not stay open as long, resulting in less velocity.

If the regulator is not creeping ( holds a consistent pressure),  the velocity will remain consistent until the pressure in the reservoir drops below the regulator's set pressure

With luck  members with more experience than you & I will clean up this scenario, & fine tune the explanation as needed.

Hope this helps
Ed

[BeauJames]

Can’t add to the conversation, not enough experience. Just gotta say we’ll done Ed. Never thought it out all the way, thanks for putting the actions of a regulated pcp into understandable terms. Can’t say if you are %100 correct, but that’s my understanding of how a regulated pcp works.
Bladebum, best of luck.

[PikeP]

Well...different levels of lift (hammer strike) that alter your muzzle velocity do ultimately result in different pressures at the base of the pellet, so a regulator set at 150 bar, and tuned with little strike that has a muzzle velocity of 600 fps may only see 90 bar at the base of the pellet, where as one that strikes the valve towards 950 fps, may see closer to the likes of regulated pressure (there is really no scenario where the pellet sees full regulated pressure with zero loss).

This is in part because, as the pressure rises in the transfer plenum/port, the pellet breaks free and starts movement prior to reaching its pressure peak in the barrel...and the pressure loss gradient begins...and when coupled with pressure loss prior to even reaching the barrel (due to transfer plenum volume, port size differences, turns, transfer port height, and other minor causes), you can bet your tuchus, that your pellet does not see the pressure you have inside your regulators plenum or better known as your set point.

[rjp]

My understanding from the Marauder world is that there is some interplay between hammer strike force and pressure that must be considered. This interplay has a self regulating effect and is responsible for the typical tuning curve with a smooth peak in unregulated guns. But the same principle applies to any pressurized system.

When the internal pressure is high it is harder for the valve to be opened, so the same hammer strike force will move the valve less on a high pressure chamber than on a low pressure chamber. This is true regardless of whether the chamber (plenum) follows a regulator or not.

Now, if you lessened the HST below Daystate's tuned point it may be that this lower HST is causing the released air charge to be more sensitive to plenum pressure, which would explain the increased velocity spread.

So in short, the HR may have some inherent variation in pressure from shot to shot but when the HST is at the optimum point this variation is effectively balanced out.  Just a guess.

[Bladebum]

I want to say thankyou all for the excellent replies on this subject. Learning more every day from the vast knowledge here.

I think I do need to clarify my POSSIBLE problem here and pick some more brains.

The regulator is not changing from shot to shot, but rather(for instance) it SEEMS as if the gun sits for a couple weeks the pressure appears to have creeped up on the guage.

Now, When I was shooting that day I had some velocity spreads, it was a hot day and I only had a few fps readings that were out of the norm. I did check reg pressure between shots and everything was sitting right on 150 bar....so possibly the chrony did what chronied do and gave me a slight misread...OR is it possible that the heat that day increased a bit of pressure in the gun?

I did pull the gun out two days ago and shot 5 shots over the chrony after the gun had been sitting for probably two weeks and the pressure on the reg was reading roughly 160(very small increments on the guage)
Here's what I got-

1-861
2-859
3-864
4-860
5-859

So obviously everything is on point and immediately after the first shot the reg pressure dropped to 150 bar where it has been set from beginning and checking it today is still there.

Do you guys in any of your regulated guns EVER see a slight fluctuation in reg pressure and are there circumstances you can point out that might have affected it?

I live at 3400 ft elevation and the day I had issues I was at sea level in hot weather.

[PikeP]

Reg creep is inevitable with regulators. Air molecules are 1/1,000,000th of an mm....and any imperfections between the regulator seat and piston will allow those through, albeit very slowly...until that imperfection is reduced to below that...

So in a nutshell, there is your issue...and changing elevation from 3,400 to near 0 and temperature from X to Y certainly can contribute some to this issue, which will remain present even at static elevation and temperature...albeit likely to less effect.

Nominally you want the reg creep to be within 1-6% of your set point. Creep within that range is usually easy to manage via proper tuning. HTH

[Bladebum]

Reg creep is inevitable with regulators. Air molecules are 1/1,000,000th of an mm....and any imperfections between the regulator seat and piston will allow those through, albeit very slowly...until that imperfection is reduced to below that...

So in a nutshell, there is your issue...and changing elevation from 3,400 to near 0 and temperature from X to Y certainly can contribute some to this issue, which will remain present even at static elevation and temperature...albeit likely to less effect.

Nominally you want the reg creep to be within 1-6% of your set point. Creep within that range is usually easy to manage via proper tuning. HTH

Pikep, i think you just cleared up my issue. This is my first pcp since my very first back in 2010 when i bought the benji disco. Needless to say pcp shop talk wasnt to common then(atleast not to me) . Long story short, lost that gun, got back into airguns about three years ago and jumped right into springers, which have a PLETHORA of natural bugaboos that go along with diagnosing issues. I was hoping that was the case here in pcp world. Thankyou for the info, and thankyou for everyone elses input as well!