Tuning FX Impact Mk2/M3 - slower first shot - no reg creep - quasi-scientific analysis

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It is a peek spacer and it can slide easy on the rod if need be the first oring should do all the sealing it does in the first place all the peek spacer is meant to do is keep the oring out of the pinch point which isn't a pinch point to help with sealing I believe it was left in there from the tip of the drill bit because it matches the angle on a drill bit perfectly I wouldn't use derlin it is to soft and I wouldn't put a oring or x ring on both sides of the spacer it will be back to the exact same problem if you look back up in the posts from earlier I would use a x ring or oring only on the one side of the peek spacer which isn't made to seal anything just to keep the oring out of the pinch point the single oring seals just fine with out the spacer why wouldn't it do the same in this application
 
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After looking at SEEKERS drawings, which I might add is great and kudos to him for pioneering all of this, tell me if I’m missing something-

SEEKER mentioned he would make the thru hole in the Delrin seal larger to accommodate the rod and guarantee no sticktion- got it.

Another o ring will go behind the back side of that Delrin piece, wether it be a standard buna o ring or X ring- got it

here’s my problem- where’s the seal? That back up o ring is not going to seal tight to the rod, no way. The Delrin, if made to allow movement as the plan, along with not crunch tight to the rod (then it’s back to square 1 with sticktion), then how is that sealing? 


i take back my input a page or so ago when I felt the duro nitrile back up o ring was the sealing o ring. I had not realized the front of the plenum end cap beak had a taper to it, but now that I see it thru SEEKERS sketches, it looks to me that taper was purpose built to wedge into that taper, which would squeeze the circumference of the PUR o ring, and that squeeze creates the seal against the rod. I also understand why polyurethane in a DURO 90 would be chosen for this as it’s just a tough o ring resistant to abrasion. The Leroy Brown of O rings. It’s unfortunate that the downside is the stick it gets against the rod, which is seen after a length gap between shots.



maybe another view into this is instead of a 2.84 ID o ring maybe the thickness of 2.62mm could’ve been less, enlarging the ID but not by much, to still create the seal but allow the rod to move more freely.



Tell me if I’m off base here on questioning where the seal against 110 to 160 bar plenum pressure would be. Maybe SEEKER can pop a drawing that shows in blue arrows the air flow or static pressure inside that plenum with the rod and both seals in view.



Tell you what, if this works, this mod should be named after SEEKER just like BSTALEY with his o ring mod on the marauder pistols
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Actually i came up with idea to use peek and sandwich the oring between it seeker was talking about using ptfe which would be to soft and we settled on just using peek on the one side the peek isn't made to seal anything the one oring does that and from his mold it just so happens that the angle matches the tip of a drill bit and am pretty sure it was left in there to speed up the process of making the parts we don't think it is using the pinch point to do the sealing any longer but oring is getting shoved into it causing more sticktion so it was a combined effort of thought to come to this others have stated they are going to machine in a oring on the other side and this is a work around to not have to do that so the peek would go up to the pinch point and the oring or x ring would sit behind it doing the sealing away from the pinch point the peek is of tighter tolerance to help minimize the sticktion if we can get some x rings it could be better because of the oil they hold between sealing surfaces
 
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When my plenum end cap gets here I’m building a 12mm long plug with dual external orings and one internal oring. Maybe the plenum pressure will seal Seekers idea but I would rather over build something and not take any chances. I hope his works but my gut tells me that taper isn’t there out of laziness. Oh and Airgunman, that was one hell of a sentence. I was out of breath when I got done reading it.
 
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When my plenum end cap gets here I’m building a 12mm long plug with dual external orings and one internal oring. Maybe the plenum pressure will seal Seekers idea but I would rather over build something and not take any chances. I hope his works but my gut tells me that taper isn’t there out of laziness. Oh and Airgunman, that was one hell of a sentence. I was out of breath when I got done reading it.
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I was out of line and I am sorry just wanted people to know it was brain storming effort if he makes this work it's all him he is doing the work to see if it will help my bad and am sorry
 
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Hi guys.

I've just started testing. The following stack was installed:



From left to right:

- peek washer which enters into conical cavity. It is snuggish around the rod. I mean it does not move freely with gravity. It has two roles: it makes the gap between the rod and the washer itself as small as possible which should minimize oring extrusion which is the next element on the right hand size. The second role is to make the sealing surface perpendicular to the oring - no more cavity. This peek washer does not need to seal anything.

- Viton FKM80 2.84x2.62 oring. Its role is to seal the plenum. I may change it to NBR90 or HNBR90 in the future which should be better in terms of extrusion and abrasion resistance.

- NBR70 5.5x1.5 oring - the only purpose of this one is to keep Viton oring in place when plenum is not pressurized. When you assembly the gun you move the rod back and forth and the role of this oring is to keep Viton in place.

There are absolutely no issues with pressurizing the gun whatsoever. Sealing is perfect. Now I need to wait at least 12 hours and verify v0.

Now goes a not so funny part. One plug which I have - has the bore non concentric. It works fine with FX's design but when you insert a peek washer which is snuggish around the rod and bore everything must be pretty much aligned. Please take a look at this picture:



Mentioned stack of a washer and orings was installed there. It is evident the rod is higher on the left side and lower on the right side. If you have such a plug then this design is not going to work. I tried it with a different plug and everything was smooth.
 
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Maybe the poorly machined plugs that aren’t concentric cause a more noticeable problem with what started this topic.
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I rather doubt in that. Original hole in the plug is concentric. It's the bore which lacks the concentricity which is not that important in FX's approach. It makes the conical cavity not concentric to the hole only.

As of RAW the question is if there is any way to check reg pressure. If there is some reg creep then this thread cannot help with that. This thread is all about having slower first shot(s) despite the same reg pressure (+-1 bar). Impact allows to verify that pressure efortlessly if one has a digital gauge.
 
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Seeker Nice work I like to here the good news so far 

Mubhaur is that in your raw with Royale design balance valve ?
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My hm1000x is typically 4-6fps high on the first shot 

like it will be 900-902fps…then is will settle around 895.

has a peek poppet, otherwise stock 

I’ve been checking all my guns for this issue for several years now. 
 
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Just for sharing, I just checked RAW HM1000X after sitting for 12 hours.

1st shot 50fps low

2nd shot 20fps low

3rd shot as per previously adjusted fps

After 3rd shot all shots are good and consistent. 

Hmmm

RAW doesn't have any conical plenum. 

Bhaur
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RAW might just have a reg creep problem.
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I have tested my RAW and the creep over 12 hours is just 1 bar.

Must be some other justification. 

Bhaur 
 
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Maybe the poorly machined plugs that aren’t concentric cause a more noticeable problem with what started this topic.
Click to expand...

I rather doubt in that. Original hole in the plug is concentric. It's the bore which lacks the concentricity which is not that important in FX's approach. It makes the conical cavity not concentric to the hole only.

As of RAW the question is if there is any way to check reg pressure. If there is some reg creep then this thread cannot help with that. This thread is all about having slower first shot(s) despite the same reg pressure (+-1 bar). Impact allows to verify that pressure efortlessly if one has a digital gauge.
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I have tested my both RAW guns with digital guage and both show only 1 bar creep over 12 hours.

But if you know that I am also using the modified valve with valve stem sealing with 90 shore PU O ring, it might have similar reasons as you gave found in impact. 

May be imperfect clearance of valve stem and O ring and outer dia of O ringb holder.

Bhaur 
 
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