PP700sa regulator fix

[bandg]

No problem.  Thanks for the thought.

[nervoustrigger]

Well, it's been a couple of months since I gave an update.  About 2 weeks ago I noticed mine was losing air.  Fortunately I could hear it coming from around the regulator adjustment screw so I disassembled to replace the O-ring on the brass piece.

Apparently sometime in the intervening weeks, the epoxy holding the white disc gave up.  That's actually a good thing...I wanted to flip the disc back over because I was pretty sure the reason the creeping returned is because I had restored it to its factory orientation.  That is, so the tapered head of the tiny screw mates to the taper on the disc.  So I turned it over so the screw's taper would pull against the sharp edge of the disc (easier for it to seal positively), and this time I used Super Glue like Denis recommended.

I'm pleased to say it looks like I now have a regulator that is working properly and POI for the first shot is right on point. 

Here's a test shot at 25 yards after sitting overnight.  At a leisurely 6.5fpe (560fps), the trajectory is pretty loopy even at this distance so this is proof positive the creeping is gone.

[WesBob]

Good news! I'll have to tear into one again to see what you mean. I tried gluing one like Denis mentioned awhile back and didn't have the results I hoped either. This would be great!

[Hobbyman2007]

The new .22 cal I just received from Wes is as consistent as the Huma equipped one I have . That’s straight from the box . They must have done something a little different either that or Wes worked some magic .

[WesBob]

The new .22 cal I just received from Wes is as consistent as the Huma equipped one I have . That’s straight from the box . They must have done something a little different either that or Wes worked some magic .

I've noticed the reg pressure tends to be higher on these ones than last time, maybe that is helping?

[nervoustrigger]

Thanks Bob.  I'm elated to have mine working well but I'd really like to understand the minimum number of things that it takes to get these regs working reliably.  There were probably half a dozen things I did and I'm rather sure at least some of them were unnecessary.  Those things are scattered in 2 or 3 threads so when I get some time, I'll post a recap of the things I did and my reasons for doing them.

Along those lines, I'm interested in your comment about a higher setpoint being beneficial.  Pretty sure I've seen that put forth before but I don't think a theory was given.  Do you have one?

BTW, I'm anxiously looking forward to the folding stock.  I recently removed a 3-9x scope and replaced it with a compact 4x...it looks way better proportioned but this gun is so accurate that I miss the aiming precision of the larger scope.  I imagine the stock is going to tempt me to go back to a larger scope and monkey with the tune again to crank the power so I'll have to reason out where I want to go from here.

[WesBob]

I'm very interested in your results Jason, and I'm sure there is more promise in your latest findings than my comment about the set pressure. I was just wondering about Hobbyman2007 having a more consistent pistol this time around than the one he bought last time. I was simply reporting what I had noticed so far as being different, thinking about creep mostly as being part of the problem with the ones I had worked on, and how the higher set pressure may make it seal in the reg better. However, it seems just as likely the tolerances inside the reg are sloppy enough that some pistols work well and some don't, or some variation in tuning of the reg and hammer spring causes some to be in the sweet spot and some not.
I want to try what you did, flipping over the plastic seal and seeing if that solves creep, along with gluing it. My last attempt at gluing was a failure, but yours was as well befo3your flipped it, so that's exciting. 

[anti-squirrel]

My reg has been very consistent all things considered, but at my short ranges, even if I'm off by 1cm the squirrel is still dead.  I've barely even gone into mine, though.  Not long after I got mine I sent to David fabricate an LDC mount... Speaking of which, when the .22 barrels come in, I'm thinking an extended shroud with better baffles is ideal- would be nice to have a compact carbine without the need for any screw-on LDC.

I'm really looking forward to the stock- and will have to get a different scope since my only 4x scope worthy of it is dedicated to my 2400KT.  A fixed 6x since I leave my 3-9 scopes right there anyway.

[WesBob]

I've found most of the ones I've tested to be very consistent as well, with a bit of a bell curve or on some a gradual rise in velocity, but within a few fps overall. However creep seems to be an issue on quite a few.
Not a big problem if not hunting, as you can just dry fire a couple shots then go at it, but for hunters it isn't really ideal, unless planning ahead and adjusting aim on the first shot to compensate.

[nervoustrigger]

Okay I'm going to attempt to detail my thoughts on getting the regulator working, most specifically with its tendency to either creep or simply not regulate at all.

To lay a little groundwork, let's quickly cover the symptoms of these problems.  If the reg creeps, what you would see is your first shot (after sitting idle for a few minutes or perhaps hours) will be substantially faster or slower than subsequent shots.  Whether faster or slower will depend on how much hammer spring preload you have dialed in, but suffice it to say if the trajectory of your first shot is wildly off, the reg is probably creeping.  This problem is a minor nuisance for plinking and paper targets but it is a total deal breaker for hunting and pesting duty, and why I hate it like the devil.

On the other hand, a failure to regulate will result in a typical bell curve like this one:


My pistol has exhibited both of these behaviors.  Following is a list of the things I've done and why I did them.  I want to reiterate that I don't know which of these was essential but it is my hope that it will help others who have struggled with getting stable velocities out of this otherwise promising platform, and perhaps if we get enough participation we can suss out the minimum steps.

This writeup will be necessarily long so as to detail certain duties and assumptions of a properly functioning regulator, and then my corresponding thoughts on why this particular regulator may not do it well and how to go about improving it.  So if you have a short attention span, go ahead and hit CTRL+W right now.

• improve the valve seat #1:  The white disc has a taper which mates to that of the little screw that passes through it.  This little cone is a critical sealing interface between the two parts.  What happens is the Belleville washers push these two surfaces apart so as to allow high pressure air to flow from the reservoir into the plenum.  As the pressure climbs toward the setpoint, the screw pulls toward the disc until it eventually squeezes closed to halt the flow of air.  If there are any imperfections in this little conical area, air will continue to seep very slowly into the plenum and its pressure will continue to rise over a period of minutes or hours. 
  
  What we want is for the regulator to cycle quickly after each shot, climb back to the setpoint, and then positively seal.  The usual approach is to lap these two surfaces together with a fine abrasive until they have a matching shape and fine surface finish devoid of any microscopic scratches or pits.  However, I advocate a little change to help with this seal so let's move on to the next one.
• improve the valve seat #2:  Looking again at this conical sealing surface, it represents a fairly large surface area.  Imagine if we instead had two dime-sized flat discs and we were trying to press them to gether to keep 3000psi from seeping out from between them.  They would have to be perfectly flat and mirror polished and then pressed together with supreme uniformity.  Well, that's hard to achieve when tiny molecules of air are motivated by high pressure to find their way through.  This little cone is similar, just on a smaller scale. 
  
  It's easier to get two surfaces to seal well if their contact patch is very small.  It's also easier to lap them together to remove any tiny imperfections in the area of this contact patch.  Fortunately all we have to do is flip the disc over and we have a simple through hole.  So what we want to do is use a black marker  to color the surfaces where these two parts meet and then lap them together until a neatly polished ring forms on both surfaces.  At that point we know they are mating well.  A handheld drill works well for this task, just take care not to chuck it up so tightly as to damage the threads on the screw...and not so loose that it pulls free and chews up the threads as you're doing the job.
• sealing the disc to the reg body:  Just as air wants to seep around the head of the screw, it also wants to seep under the disc, around it, and up into the plenum.  I think the factory attempts to achieve this seal by torquing the daylights out of the assembly to crush the disc, and indeed many users had a problem with a slow leak after reassembling the regulator.  It was leaking from one side of the disc or the other, and escaping through the threads. 
  
  We addressed the leak by adding the O-ring pictured here:
  
  
  Unfortunately that only masks the real problem.  It simply keeps the leak contained and continues to allow air to migrate from the reservoir to the plenum and increase its pressure.  Eventually I presume the pressure rises to the point where the screw pulls so hard against the disc that it helps seal the bottom side of the disc to the reg body.
  
  So Hobbyman proposed gluing the disc down.  My first attempt with epoxy appeared to hold after one disassembly but it gave up sometime thereafter, and for all I know it might have already fractured in one localized spot that I couldn't see.  My second attempt with Super Glue is working great so far which is just a couple of weeks. 
  
  I think it's important to note here three (3) things that I expect will greatly influence the reliability of this fix.  Firstly, the repeated stress from air pressure wants to lift the disc.  Therefore it is important that the reg be tightened to the absolute best of your ability.
  
  Secondly, a comment about the addition of the O-ring pictured above.  I noticed on disassembly that my O-ring was slightly chewed up from screwing the two halves together.  That suggests it may prevent them from threading together fully, thus not preventing the disc from lifting.  For this reason I'm on the fence about keeping it.  As long as the disc stays bonded, it prevents the plenum side of the reg from leaking to the outside world.  So I carefully thinned my O-ring before reassembly and it's working but if the disc breaks free again, I will probably omit it.
  
  And thirdly, it's helpful to get the glue bond as close to the hole as possible.  Imagine if the glue were only at the perimeter of the disc.  Any air that manages to get in under the disc will have a substantial surface area to push against in an attempt to break it free.  If the glue bond extends all the way to the center opening, it can't do that.  So that was an aspect I paid close attention to when I glued mine, I just had to take care not to overdo it and get a lot of squeezeout into the opening.  Fortunately I didn't have that problem.  Granted it would be easy enough to clean out so long as I was able to remove the screw.  Might be easy, might not.  Just be mindful of the fact the brass piston can potentially spin with it and make it difficult to unscrew.  Could cut a slot in the end of the brass with a thin emery wheel if you're concerned about that.
• Thoughts on concentricity of the plastic disc:  When I glued down the disc, I wanted to be sure it was concentric with the axis of the screw.  Otherwise they may not seal against each other properly and that effort we put into lapping them together may be for naught.  The way to do that is to run the screw all the way down until it squeezes against the disc.  However the tap depth on mine was not sufficient to allow it to thread in that far so I added a couple of small washers on top of the brass piston to allow me to do that.
  
  Meanwhile I also want the outside perimeter of the disc to make a good bond.  Super Glue (cyanoacrylate) does not bridge gaps well and cures more quickly when the surfaces are close fitting so I also screwed the two halves of the reg together and left it for a few hours to allow it to cure.  I don't know that it needed a few hours but when I disassembled it to check on things, the squeezeout was still liquid but the disc seemed to be bonded well.  So I proceeded to carefully clean up.  I don't know what kind of plastic the disc is made of so I used a cotton swab for cleanup with acetone, allowing some incidental contact with the perimeter of the disc but none to the seat, and not saturating it to the extent that I might weaken the bond between the disc and reg body.
  
  Verbose with a purpose
• Belleville stack:   Regulator Belleville stacks are generally comprised of 5 or more in series.  In this particular case, the factory reg had 5 pairs of Bellevilles in series (( )) (( )) ((.  A series arrangment has the same spring rate as a single washer (or in the case, the same spring rate as a nested pair that, for the purposes of this topic, I'm treating as a single stiffer washer).  So why go to this trouble and expense?  Because it makes the setpoint more stable / repeatable with respect to minor variations in the total travel of the regulator as it cycles open and closed, and presumably in the tiny amount of travel that occurs as the regulator goes from almost-closed-but-still-flowing to fully closed.
  
  The PP700 reg has very small Belleville washers compared to most I've worked with and they have correspondingly very little travel.  5 times not much is still not much.  To put some numbers to it, each washer has 0.007" of travel which means the factory arrangement only has 0.035" of total travel at best.  Potentially much less depending on how much preload is applied and how far the stem has to move to reach the seat.  For comparison, a typical paintball regulator using 0.032" Bellevilles has a max available travel that's 2.3 times as much (0.080" vs 0.035").
  
  I reasoned it might behave more repeatably and perhaps creep less if I changed it to single washers in series.  That halves the spring rate and therefore reduces the maximum setpoint I can achieve so this may not be an option for those of you wanting your pistol to be a hand cannon.  However it's fine for my purposes.  Granted, one of the key reasons I originally wanted this pistol was because of its potential to be run at around 12fpe (in .177 caliber) and use it as a 25 - 35 yard squirrel gun.  But I've since changed my mind and decided a gun with a barrel the length of a soda straw is better suited as a long shot count 6fpe fun gun for the back yard and I can still keep it on me when I'm hunkered down on a pesting session and a squirrel sneaks up on me from above.
  
  So I figured up a simple series stack that is about the same height as the 5 pairs and it worked out to 8.5 washers which I rounded up to 9.  This arrangement ()()()()( bumps up the max travel to 0.063" which is 1.8 times as much as it had from the factory. 
  
  So let me reiterate I don't know if this change is useful in solving the problems outlined at the beginning of this post but I wanted to explain my reasoning for you guys to at least consider as part of your overall strategy.  Also, I have not explored how high the regulator can be set.  I did accidentally get a pellet to hit 900fps shortly after reassembling.  It might have been a fluke, I don't know.  I promptly backed off the reg and have not yet tried tuning it for higher energy.

 
That's about all I can think of at the moment, although I have a sneaking suspicion I'm forgetting something.  I'll give it some more thought today and if I think of something, I'll post an update.

Until then, best wishes for dependable first shots and long flat shot strings!

[anti-squirrel]

Nice legwork, Jason.

I'll be headed down this path eventually- once Wes gets the .22 barrels in, I'll probably start digging in.  My Maximus will be my go-to PCP while the PP700 is "in surgery".

Got some other ideas in the works but travel-season is upon me so I may end up focusing energy on bottle-feeding my 1740 and keep the PP700 mostly-stock.

[WesBob]

Very good layout of what you've tried and the reasoning behind it. Thanks!
Which would you think would be most logical to try first? It seems to me the flipping of the white seal, lapping and gluing, plus the change of the reg stack may all be part of the solution, but I suppose doing the white seal mods first might give a good indication if changing the washer stack is needed.

[nervoustrigger]

Hi Peter, I know the .177 has been very good to you so far so best wishes on the .22.

Wes, if you're keeping it non-PAL (is that the right term in the Canadian parlance?), personally I'd go ahead and reconfigure the washer stack.  No need for the nested pairs for a 500fps limit.  The only reason to skip it would just be an attempt to gain a better understanding of what changes are necessary.   I do hope we can eventually figure it out but don't let that influence your decision because I think we're gonna need multiple instances of corroborating experiences to draw conclusions.  I mean, you're welcome to kick things off but this is mostly anecdotal stuff so it's not a big deal.

[WesBob]

Sounds good. I'll rearrange the stack. These are coming with a reduced transfer port size so we'll see if it  keeps enough power variance to get it close to 500fps.
Thanks,
Wes

[WesBob]

Oh, and good on you for picking up Canadian parlance 🙂. Non-pal is one way of saying it for sure

[Hobbyman2007]

That’s a good collection of thoughts about how to go about getting rid of the creep . Good work Jason . I had no idea about what the actual travel of the washers was . There sure isnt a lot of play available . I’d go on a limb and blame the white disc for the creep , although it’s a novel idea I think there must be a better way to seal the reg from the plenum . The initial glue job that I did on my first pistol held up until I installed a Huma Reg . The second has not got the glue treatment yet .

[mackeral5]

You guys are making it very difficult to resist the urge to pick up one of these.... If one happens to show up in the classifieds that may be the tipping point.

[anti-squirrel]

You guys are making it very difficult to resist the urge to pick up one of these.... If one happens to show up in the classifieds that may be the tipping point.

For the price, just get one new.  I don't there's have been too many duds in the accuracy department.  Mine is decidedly not pellet-picky and has put a goodly number of squirrels to rest.  I've also used it one-handed at arms length with a rifle scope and nailed a CO2 cartridge at 35 yards many a time.  You can adjust the trigger, hammer spring tension, TP, and regulator, and both David (Rocker1) and Donny have adapters to make 'em have a softer bark.  I haven't checked with anybody else, but I'm sure others can too.

I keep telling folks it is the best way to get into PCPs since everything is adjustable and the tiny tank makes pumping a snap.

[WesBob]

Well, Stacking the washers like you did, Jason, provides plenty of power to get to 500+fps, even with the reduced transfer port on the Canadian version. I've got the pistol filled and have it tuned to 490fps at the moment, so we'll see in the morning if creep has been eliminated or not. I did as you had, and flipped the plastic seal, spun it against the screw with a drill then glued it down with super glue. Hopefully it's all sealed up now and I can reproduce your results. 🙂

[WesBob]

You guys are making it very difficult to resist the urge to pick up one of these.... If one happens to show up in the classifieds that may be the tipping point.

For the price, just get one new.  I don't there's have been too many duds in the accuracy department.  Mine is decidedly not pellet-picky and has put a goodly number of squirrels to rest.  I've also used it one-handed at arms length with a rifle scope and nailed a CO2 cartridge at 35 yards many a time.  You can adjust the trigger, hammer spring tension, TP, and regulator, and both David (Rocker1) and Donny have adapters to make 'em have a softer bark.  I haven't checked with anybody else, but I'm sure others can too.

I keep telling folks it is the best way to get into PCPs since everything is adjustable and the tiny tank makes pumping a snap.

Yep! Great gun to start off with in pcp, I agree!
Great for a hand pump too, so no need to buy compressors and tanks and gives a lot of shots per fill.