FX Crown: The Dreaded "Regulator Creep"

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MP44

MP44

Member
Apr 3, 2015
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VA, United States
I have had my .25 Crown for about a month. The gun might be the most accurate airgun I have owned. The only problem is it has regulator creep. I thought it would go away with use but unfortunately, it is going to have to go in for warranty work ( waiting to hear back from FX USA )

Yesterday I took it out after work to give it one more chance before contacting FX. 5 shots @ 35yds. You can see the first shot that hit low on the 3/4" sticker and the last four thru nearly the same hole. 

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After the first shot, this rifle stacks pellets all the way out to 70yds ( longest range in my yard ). Even with the creep, I like the Crown so much I have a .177 Crown, also in walnut, on the way. 

BTW, how do you normally contact FX USA? When I wanted to order o-rings I could never get them on the phone, only email and I ended up having to send all my CC info thru an email to order the o-rings. I emailed them about the Crown yesterday but haven't heard back yet :-(

The Rifle

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I have a Crown as well in .25 since June of this year. My reg from the factory is at 130 bar, now about 135-ish after not having shot if for two weeks. Is it worth the trouble to send it back? Not really from my standpoint. I'd rather just look at the gauge, see that it's crept up a tad, dry fire it once, then go shoot one hole groups all day long. Now if it was leaking or accuracy was crap, then yes, I'd part with my gun for a while to get it fixed.

I hate shipping expensive items knowing they may return back to me in worse shape than sent out unless I have no choice.

Good luck with your gun.
 
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I would first make sure that the creep isn't temperature related. If you store it in a cold location, let's say 15 degrees celsius, and take it out too shoot outside at 30 degrees celsius the pressure in the regulated chamber will increase 10 to 15 bar in the time you're setting up to start shooting.

Shoot it and after the last shot check the regulator pressure (first tap the plastic cover plate of the gauge a couple of times to make sure the needle is settled), lay the crown down for an hour or a couple of hours in the same temperature and check if the pressure has risen. If yes than you might have a regulator that isn;t sealing , if not then everything is fine (a couple of bar rise isn't problem, 10 bar or more is for sure a problem).
 
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After double stacking the belville washers in the regulator I no longer have issue with creep, I have over 4000 shots through my Crown 25 and gun is amazing. Keep shooting gun, my Crown really seemed to get better after shooting several thousand rounds. I will not use gun for weeks and regulator does not budge anymore.



Where did you find the stacking order?
Click to expand...


 
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Creep is caused by slight imperfections at the valve seat. What’s happening is, as the pressure in the plenum rises up to the setpoint, the spool moves ever closer to the valve seat until such time as they make full contact and the flow of air is halted. So as you might imagine, just before that happens, there’s a teeny tiny gap through which a very small amount of air is seeping. Similarly, if the two surfaces do not mate together perfectly, there continues to be a very slow movement of air into the plenum until the pressure climbs high enough that the seal material compresses to the point that the flow is halted. The time it takes for that to happen may be anywhere from a few seconds to a few hours.



To repair a creeping regulator, sometimes it is necessary to dress the seat surfaces. Or in some cases, just replace the seal at the end of the spool.



It’s not uncommon for a brand new regulator to creep until it has been cycled a few hundred times. What happens is the seal eventually wears in and conforms to the valve seat. But if it doesn’t correct itself, it may be time to inspect the seal and valve seat. If there are any burrs or if the surfaces are worn, that’s what needs to be addressed.



And eventually the problem crops up after the regulator has been cycled many thousands of times, when the seal wears out or has been cut by tiny debris that zips by.



To give an example, I was dealing with a used paintball regulator from JDS Airman that was creeping up from 1.2k to 1.5k over a period of several hours. Once apart, I could see the seal material was worn. It was a flat seal made of a rigid material. Not a plastic like acetal (Delrin) or PEEK, more like a Bakelite material. I dressed it flat and smooth again, and also made sure there was no burr on the conical aperture to which it mates. After reassembly, the creeping was gone. It would quickly move to the setpoint and hold there.



Another example is the little ball seal on Ninja regulators. It will develop a little indentation where it presses against the conical aperture. If you’re careful, you can punch out the ball from behind, rotate it around to a fresh surface, and press it back in. Or you can get the rebuild kit for about $15 which contains a complete replacement spool.
 
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A few comments on the Belleville arrangement...



If it was originally a series arrangement where each washer is opposing the last () () () () ()



Changing it to doubles (( )) (( )) (( )) doubles the spring rate and reduces the amount of travel the stack can undergo. The increase in spring rate means the adjustment range will shift up, thus you may not be able to get back to the same setpoint. And the reduction in travel means there will be more pressure variation each time the regulator cycles. That may or may not be a problem depending on how carefully the rifle is tuned.



I will respectfully submit there is no fundamental reason it would solve regulator creep. I think you either got lucky, perhaps cleared a tiny piece of debris that was trapped in the seal, or the seal finally wore in against the seat and stopped creeping.
 
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A few comments on the Belleville arrangement...



If it was originally a series arrangement where each washer is opposing the last () () () () ()



Changing it to doubles (( )) (( )) (( )) doubles the spring rate and reduces the amount of travel the stack can undergo. The increase in spring rate means the adjustment range will shift up, thus you may not be able to get back to the same setpoint. And the reduction in travel means there will be more pressure variation each time the regulator cycles. That may or may not be a problem depending on how carefully the rifle is tuned.



I will respectfully submit there is no fundamental reason it would solve regulator creep. I think you either got lucky, perhaps cleared a tiny piece of debris that was trapped in the seal, or the seal finally wore in against the seat and stopped creeping.
Click to expand...

Based on personal experience with the FX regulators I believe the tolerances are horrible. Double stacking might help keep them aligned on the piston better. Not sure if you've seen one before, but the differences in the belleville ID and the piston OD (IMHO) is a major part of the problem.

Here is what I found with my WC regulator. The difference in OD of the piston and the ID of the belleville washers allows the washers to “slide” between cycles. With the washers not “centered” all the same, the stack length can change. If the measured stack of washers is not the same each time the the pressure is different. Notice in the below pic how I can move the washers. I get a measurement of 6.16mm ID for washers and 5.68mm OD on piston. Then add to this the piston is threaded where the washers ride.

1534381668_16607926185b74ce647cc344.03539951_20180508_161140.jpg




Here is the thread where this was discussed earlier this year

https://www.airgunnation.com/topic/fx-regulators-problems-and-fixes/page/2/#post-301205
 
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A few comments on the Belleville arrangement...



If it was originally a series arrangement where each washer is opposing the last () () () () ()



Changing it to doubles (( )) (( )) 



I will respectfully submit there is no fundamental reason it would solve regulator creep. I think you either got lucky, perhaps cleared a tiny piece of debris that was trapped in the seal, or the seal finally wore in against the seat and stopped creeping.
Click to expand...

By double stacking the BV washers, you are also making the spring package less sensitive.

With other words, the "door is slammed harder", thus a faster regulator response, and less prone to creep. (Keep in mind that the delrin piston also has got some flex in it, and the nose in the adjustment screw will slightly dig in the sealing surface.)

If the spring is weak, pressure will slowly keep on rising until the balance between pressure and spring tension on the reg. piston settles.

When the spring is stiff, the reg piston will move faster, and also close faster.

It is very hard to explain, but more spring tension helps to prevent regulator creep. 
 
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After double stacking the belville washers in the regulator I no longer have issue with creep, I have over 4000 shots through my Crown 25 and gun is amazing. Keep shooting gun, my Crown really seemed to get better after shooting several thousand rounds. I will not use gun for weeks and regulator does not budge anymore.
Click to expand...


You shouldn't have to do this.
Click to expand...


I agree. You pay almost $2000 for rifle it should be right when it leaves the factory and not require modifications to shoot correctly.
 
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