FX Crown "Reg Creep"

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STO

STO

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Sep 30, 2018
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Maine
I live in New England. It is cold here this time of year, sometimes I'll be out shooting and it is below freezing. I've put a few tins through my FX Crown, and the reg has broken in nicely sitting at 130BAR and filling quickly after each shot now. Nothing out of the ordinary. However, on some occasions, I'll notice my gun having sat for a while will creep up to 135 sometimes almost 140BAR. (on the reg side this is) This doesn't make any sense. If the reg were leaking, it would continue to climb, but it doesn't. If the reg were inconsistent, why not jump by a larger margin or at least be consistently inconsistent? 



I did a bit of digging, and there isn't a good technical diagram on the Crown reg I could find that really lets me visualize how it works, but seeing the new FX Master Class video (link below) I realized something: The FX Crown doesn't run a balanced reg design. I may be wrong, or messing up my terminology here, but stick with me. Part of the reason you can't turn the reg down on the Crown is that there is nowhere for the vented air to go, so you're just stacking more and more force on the piston. This means that, if there were a pressure rise in the plenum, it would be trapped there and would be reflected in the post-reg gauge pressure. 



Okay, brilliant and all, but what relevance does that have? Well a little napkin math and the ideal gas law (PV=nRT) and I estimate you should expect to see a 5BAR jump in your plenum pressure (remember IDEAL gas law, meaning not perfect/exact) if it went from 50F to 70F. And you could/should see more if you went from 30F to 70F. The Crown action is a big chunk of aluminum, and acts as a heatsink, so you're not going to see this pressure increase quickly, only slowly, if you were shooting outside for say an hour in the freezing cold and then came in to your nice warm house. On most guns you don't have a gauge after the reg, so you can't be anal-retentive like me and watch your pressures so closely, but on the Crown you can. So yay? This also holds true for the tank, which I've noticed loses some pressure after recharging (because the air is quite warm going into it), and that loss is directly proportionate to the decrease in temperature. Similarly if I fill the gun when everything is cold cold cold, I can watch the tank pressure rise by several BAR as it warms up. 



Food for thought. I hope someday this post helps a newbie terrified that he has reg creep or a leak, when actually he is just changing temperatures. 


And the video I was referring to:

https://youtu.be/SRuQHlHDW1g


 
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I've noticed the same thing. I usually park my rifle near a heat source after finishing a session in the cold. I also blow off a few shots as I watch the regulator gauge creep up. (While shooting just recently I watched it go from 120 bar to 140 bar once inside.) Once the rifle is warm again and the regulator pressure is back to normal i'll stick it back in the safe. What i'm wondering is if there are any detrimental effects to having your reg pressure bouncing up and down like that? (In theory it would work the other way too, going from hot to cold would see a decrease in reg pressure, though I've never noticed it.)

Ryan
 
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The first shot from a regulated gun after storage for any period should always be either at regulated pressure or higher than regulated pressure(assuming in most cases, bottle pressure is higher than regulated pressure). Your regulator is a closed system that allows air to be pressurized to regulated pressure from the bottle, hence if temperature changes, it affects the regulated pressure, and depending on conditions, either the bottle tops up the regulated pressure(if room gets colder), or pressure builds up in the regulator(if room gets warmer) - Physics and Thermodynamics.

If regulated gun was stored away and then shot at a higher room temperature from when it was stored, you should expect the first regulated shot to be at a higher pressure/fps. This is because the regulator has no way to dispel the pressure build up from initial regulated pressure as temperature builds up in it – as temperature increases, pressure increases. 

Conversely, if regulated gun was stored for a period and then shot when the room temperature was at its lowest, then one should expect the pressure to be at regulated pressure, assuming no creep. Similarly, if after a shot, the gun was stored at the absolute same temperature as it was before the next shot, without the temperature ever swinging lower, then one should expect the regulated pressure to be unchanged.

You have a regulator creep/leak issue if your regulator creeps gradually towards bottle pressure over time during storage, or if the regulator takes a long time to get back to set regulator pressure after a shot, or it just does not regulate at at all and just shoots at bottle pressure.

I know it sounds complicated, but it really is a simple closed system thermodynamics behavior. 
 
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The first shot from a regulated gun after storage for any period should always be either at regulated pressure or higher than regulated pressure(assuming in most cases, bottle pressure is higher than regulated pressure). Your regulator is a closed system that allows air to be pressurized to regulated pressure from the bottle, hence if temperature changes, it affects the regulated pressure, and depending on conditions, either the bottle tops up the regulated pressure(if room gets colder), or pressure builds up in the regulator(if room gets warmer) - Physics and Thermodynamics.

If regulated gun was stored away and then shot at a higher room temperature from when it was stored, you should expect the first regulated shot to be at a higher pressure/fps. This is because the regulator has no way to dispel the pressure build up from initial regulated pressure as temperature builds up in it – as temperature increases, pressure increases. 

Conversely, if regulated gun was stored for a period and then shot when the room temperature was at its lowest, then one should expect the pressure to be at regulated pressure, assuming no creep. Similarly, if after a shot, the gun was stored at the absolute same temperature as it was before the next shot, without the temperature ever swinging lower, then one should expect the regulated pressure to be unchanged.

You have a regulator creep/leak issue if your regulator creeps gradually towards bottle pressure over time during storage, or if the regulator takes a long time to get back to set regulator pressure after a shot, or it just does not regulate at at all and just shoots at bottle pressure.

I know it sounds complicated, but it really is a simple closed system thermodynamics behavior.
Click to expand...

^This. Exactly this. Thank you. One nitpick though:
"If regulated gun was stored away and then shot at a higher room temperature from when it was stored, you should expect the first regulated shot to be at a higher pressure/fps. This is because the regulator has no way to dispel the pressure build up from initial regulated pressure as temperature builds up in it – as temperature increases, pressure increases." 

I don't come from a land of exclusively airgun regulators. Many regulators, like the common type you see on pneumatic equipment in every workshop you've ever been in, are balanced so when you turn them down they will bleed air from the regulated side (what would be the plenum side on an airgun) of the system to meet the set pressure. In this way, even if they have a slight bypass leak, they'll maintain the correct pressure. You also don't have to bleed the system to safely reduce regulator pressure or see what your new system setting is. Silly me, I didn't immediately realize that FX (and probably most if not all airgun manufacturers) run an unbalanced reg that has no bypass, so if plenum pressure rises it is held. 



I don't think HUMA makes a reg for the Crown do they?
Click to expand...

To my knowledge they don't, although they probably will soon. (guessing) In my case though, I have great consistency so absolutely no need for one. I do a lot of diagnostics, and in general I try to understand problems and NEVER throw parts at something to fix it. In this case, had I just assumed it was a reg fault and gotten a replacement, I'd have bought a replacement and the "problem" would remain unchanged. 



I've noticed the same thing. I usually park my rifle near a heat source after finishing a session in the cold. I also blow off a few shots as I watch the regulator gauge creep up. (While shooting just recently I watched it go from 120 bar to 140 bar once inside.) Once the rifle is warm again and the regulator pressure is back to normal i'll stick it back in the safe. What i'm wondering is if there are any detrimental effects to having your reg pressure bouncing up and down like that? (In theory it would work the other way too, going from hot to cold would see a decrease in reg pressure, though I've never noticed it.)

Ryan
Click to expand...

Just guessing here, but coming from Sweden I'd expect that if cold-hot temperature shifts were a threat to the gun, FX would note it in their manual as room temperature is the same around the world but Sweden gets hella cold in places in the winter. You'd also think at least SOMEONE would have mentioned it before now if it were a real mechanical problem, in some brand of gun at least. 


 
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I noticed the same thing about half a year ago (same type of topic)

There is also a different kind of creep in the early version of the Crown regulator (FX impact had the same issue). The BV washers that are used could only handle a certain force and runway before being flattened. The pressure will keep rising very slightly because the reg isn't completely sealing and at a certain pressure the force will be high enough to push the piston enough to seal eventually. This is caused by an adjustment screw that's just a little too far out. This can be fixed by rearranging the BV washer stack so it can handle more force so it can regulate a higher pressure.

If it fully leaks it indeed will go to the bottle pressure, therefore it might be wise to store the gun at a lower pressure than maximum. There is a possibility that the hammer won't be able to open the valve anymore at max pressure. In the unlucky event that the regulator will not dump it's plenum when the cylinder or bottle is detached your stuck with max pressure in the reg chamber. With the pressure gauges that measure the reg pressure it is possible to unscrew them a little to let it his out (although the brass of the gauge won't really like that) but if you don't have this alternative methods are needed.
 
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My Crown has the very same creep..

I have just replaced my Regulator with new Parts from FX USA..

FX has replaced the regulators in newer Rifles with a larger Brass Body..

Mine measures 8mm outside diameter on the end diameter. Newer models measure 10mm. This is all they told me..

Oh and no reworks for older models like mine.. Takes a replacement of the entire action block..

Also the older models have a small point on the end of the pressure adjust screw.. This was replaced by a

screw with a polished end slightly domed instead.

So I replaced the old with a new..

I also changes the BV Washer configuration.

This part is all here:

https://www.airgunnation.com/topic/fx-crownimpact-regulator-mod-tutorial/

I set my Regulator to 151-154 bar and so far creep goes up to 160 over 6hrs and holds steady..

So far things shoot excellent.. Smoking the 25cal. 34gr. MK2s at 890 to 900fps.. Energy around 60flbs

with all the accuracy.. After over 24hrs. the Regulator is still at 160 bar..

Now read that post and follow the instructions on the BV washer configuration with a added washer..

High pressure damage comes from total compression of BVs and flexing of the piston shaft..

Results can be seen on this shaft when removed.. It will show the BVs have damaged the shaft surface from flattening BVs, binding and flex..

This new configuration so far works well.. If any issues result???????

I will post it for sure..






 
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I've noticed the same thing. I usually park my rifle near a heat source after finishing a session in the cold. I also blow off a few shots as I watch the regulator gauge creep up. (While shooting just recently I watched it go from 120 bar to 140 bar once inside.) Once the rifle is warm again and the regulator pressure is back to normal i'll stick it back in the safe. What i'm wondering is if there are any detrimental effects to having your reg pressure bouncing up and down like that? (In theory it would work the other way too, going from hot to cold would see a decrease in reg pressure, though I've never noticed it.)

Ryan
Click to expand...

If the pressure in regulated side goes down, the tank will fill the gap, the reg valve will open.

The regulated air pressure is what is sealing the valve cone. If the pressure goes down the valve will open.

If the pressure rises in the regulated side, the reg "valve" will only seal harder.



If the regulator is malfunctioning where the regulated pressure is increasing.

The only reason for this (except manometer) that I can find is if the regulator is not sealing properly here (see pic). All other problems with orings, dirt, damaged surfaces etc will cause leakage. But not increase of regulated pressure.

1540911557_14602491735bd871c5afe044.10854355_asdasdasdasdasdasd.jpg




Edit I actually thought of another way to make it fail, if done deliberately

spurt compressed air through the small hole shown in the pic below, and the reg.pressure will go to max

1540912148_14017498435bd874148ae6d3.13615992_asdasdasdasdasdasd.jpg





 
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STO you too go back to school



the physics equations work in Kelvin not in C or Fahreheit. so the temperature difference influence is smaller/ negligible. few degrees up and down will not have that effect.



HUMAs are also creepy/slow refill, nothing is perfect. but better than the original. if you have a bad reg, send it back they should not get away with it within warranty. why should you buy a huma for your extra money?
 
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3 Options IMO. Tune around it (ie: tune to around 3% of your plateau), replace the regulator with huma or lane, warranty it. Creep is NOT a normal function of regulators...but the third option will likely get you back to point a with creep. FX regulators aren't superior by any means to whats on the market...the 'creep' seems to be a common trend with them.
 
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the physics equations work in Kelvin not in C or Fahreheit. so the temperature difference influence is smaller/ negligible. few degrees up and down will not have that effect.
Click to expand...

A few Kelvin up and down indeed won't have a large effect but going from a cold outside temperature (0 degrees C = 273.16K) to room temperature will bring a reg pressure increase of a little over 10 bar. The percentage increase in temperature is directly proportional to the percentage increase in pressure and vice versa.
 
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Every closed reservoir containing a gas is subject to the gas law. The only reason we can visually see it now is because FX was the first to put a pressure gauge in that reservoir. If this was done 10 years ago it was assumed normal by now. Never noticed that after filling your scuba bottle (which will get warm while being filled) the pressure will slowly drop when it cools down? There's no witchcraft or leaking happening there... The specific phenomena mentioned in this topic by TS is nothing specific to FX regulators, all regulators that seal properly will have this "problem".

Test the following if you still think this won't happen: take a reg pressure tester and pressurize it, if the regulator seals properly you can degas the filling hose without degassing the regulated chamber. Leave the pressurized chamber in a room at 0 degrees C for an hour, afterwards bring it to a room at 20 degrees C and see the magic happening.

I've seen this exact thing happening with my Crown with the bottle detached and the plenum pressurized, the pressure was measured with a digital pressure gauge. The only explanation for this is the gas law...


 
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That is a perfect View of the Regulator I have..

The New Adjusting Screw has been slightly domed instead of that point right at the arrow.. As I posted, I changed the BV configuration as well..

6 to 8 bar rise in 8 hrs before creep stops... I can live with that no problem if the Regulator can handle higher pressures..

I am set at 154 bar.. The Regulator now sets and seems to work so much smoother with more perfect doubles and triple shot consistency....
 
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STO you too go back to school



the physics equations work in Kelvin not in C or Fahreheit. so the temperature difference influence is smaller/ negligible. few degrees up and down will not have that effect.



HUMAs are also creepy/slow refill, nothing is perfect. but better than the original. if you have a bad reg, send it back they should not get away with it within warranty. why should you buy a huma for your extra money?
Click to expand...

I know that the SI unit for the ideal gas law is Kelvin, however most people (yourself included apparently) don't really understand what that means or how to do the conversions. For the convenience of the people reading, I did the math in the requisite SI units, then converted to Fahrenheit. The numbers should be accurate, or at least if they aren't that isn't the source of error. 
 
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 ...the regulator IS a balanced design, only you don't see it how it works my friend.

3-5 bar up and down is closer to the reality maximum as far as the reg chamber pressure temperature dependancy. i calculated with 30C to 0C and it was 10bar. 10C will give you 3bar roughly

by the way you will not see it on the POI as the knock open valve compensates for that little change. the fps will be lower in cold overalll but thats a different temperature phenomenon.

someone gave me a -, so i will stop no point going into details on how this reg works.

right so how DreamSmoker solved his 'temperature problem' by tuning his reg?
 
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I believe that all the factors we have addressed are contributing to the CREEP..

Any surface that comes in contact with another moving surface with one O"ring using these pressures will

have some blow by or creep..

O"rings have a tolerance on how much they can be compressed.. So squeezing those O"rings tighter is wrong..

You could make surface contact more efficient with making double O"ring seals in these areas.

Seems the higher you push the Regulator, the more creep appears.. Seems linear here.. The higher you set, the higher the creep..

Keep in mind this creep takes a bit of time with Gun at rest to be even noticed when you are shooting...

Now using the BV washer configuration described in the Link above

allows much higher pressure to be achieved without damaging your Regulator..

So far so good at 154bar/900fps/JSB/MK2/34gr with less deviation then the Day This Crown Arrived at any velocity with any Pellet.

With a full supply tank at 250bar.. Regulator is set at 154.. Creep rise was to 163 to 165bar over night..

This Crown is one Hot Rifle and more accurate than anything I have ever shot or fired in my life..

The Hotter I set her, the better she shoots..

I can stack those Heavy 25s in the same hole all day long at 50 yards..

Lock time is amazingly short, crisp and the Pellet goes right where your trigger breaks 100%..

Now on to replacing a crap fish tank pump that failed in my compressor just after I replaced and modified my Regulator.. GO Figure..LOL

If its not this thing??? Its another that breaks... All my high $$$$$ Toys have had parts that only cost Pennies fail this week..


 
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