Air Venturi Avenge-X O-Rings

[M Volle]

I have an Avenge-X 25 cal and have had numerous o-ring issues over time -

There are two different schematics of the rifle that I know of - with variations for the stocks and tube or bottle air storage. The drawing available at Pyramid Air is the clearer one but doesn't list a few of the pieces (they are in groups and assemblies)

I took just the core parts and made a slightly revised diagram with a bit more information about the o-rings - including the Shore hardness - showing the Shore 70 and Shore 90 o-rings (there are also a few "white" poly o-rings on the bottle I didn't note)

I have replaced the ones labeled #79 twice now - seem to be a frequent source of leaks

I have replaced the #77 o-ring inside the regulator three times now - Careful checking around the threads of the regulator has revealed slow leaks and each time, the inside o-ring replacement cleared the issue.

O-Ring #74 is actually the one visible on the stem when you remove the regulator - its outside the enclosed core. Its the most challenging to install but doesn't have to be replaced to get to the #77 ring that keeps deforming and leaking.

Ring 27 is actually inside the end of the valve seat - part 29 - and the stem inserts from the poppet side - not from where its shown.

This isn't anything official - just thought I would share as I made the chart to make my maintenance easier.

 

[Aslap]

Thanks for this! The way that AV has the parts schematic and list is not very good. Why they don’t have the parts description listed in numerical order is beyond me. The interactive feature is OK but I’d much rather see a part number then go to the description and go to that number to see what it’s called.

Anyway, I have this saved with the other AV info I have. When it comes time to replace O rings, this will be very helpful!

Tony

 

[davee1]

thank you for that OP. thats very interesting to me about having to replace #77 3 times. Usually that would indicate some kind of design flaw like wrong material. Have you inspected one of the failed orings for failure mode? Maybe try Viton or cast PolyUrethane for a different material.

 

[M Volle]

thank you for that OP. thats very interesting to me about having to replace #77 3 times. Usually that would indicate some kind of design flaw like wrong material. Have you inspected one of the failed orings for failure mode? Maybe try Viton or cast PolyUrethane for a different material.

I have been looking at the failures - and am thinking about alternate materials.

A few locations show classic "extrusion" with the impression of the gap and edges showings micro tears and "chips" - a good indication of a fit or tolerance problem - and I'm gathering dimensions and info on those - possibly choose an alternate sized o-ring.

The other failure I am seeing, I'm not so sure about - the o-ring becomes glazed or polished on the outside, deforms to have a slightly crowned top edge and gets very hard - they crack when removing and some have shattered into several pieces. Two of the originals were almost square in cross section.

The groove and clearance on the ring inside the regulator looks to be a tolerance issue.

Some of these, the process of installing them requires enough stretch that some materials wouldn't survive trying to install them. I had to make a tapered guide to fit the one on the exposed end of the regulator (takes only seconds to replace with the tool)

I've also been trying to learn about the available materials - some of the best options for wider gaps and higher pressures also seem to be poor at handling dynamic pressure changes - The cast PU rings would be great for pressure and are on the bottle neck but even unscrewing the bottle too fast will blow them out.

Viton looks like a good alternative but can swell with any moisture (which shouldn't be in the gun anyway) - I'm trying that on the exposed ring on the regulator right now. I think I have dealt with any moisture from my compressor and filling process - added a large desiccant filter in front of the compressor (its a small compressor) and secondary high pressure side filters remain completely dry.

 

[davee1]

Specifically for #77, I would buy em and try em...and add teflon to the materials to try, along with viton and cast PU. Just buy them and try them. Dont try to rule them out right now. The fact that some of them have broken into pieces to me means that they may be succeptible to the oils there, which should be silicone oil, but may be contaminated by something else. Also, what size/durometer are you currently using for #77? 6x2 90?

 

[M Volle]

Specifically for #77, I would buy em and try em...and add teflon to the materials to try, along with viton and cast PU. Just buy them and try them. Dont try to rule them out right now. The fact that some of them have broken into pieces to me means that they may be succeptible to the oils there, which should be silicone oil, but may be contaminated by something else. Also, what size/durometer are you currently using for #77? 6x2 90?

The current o-ring is id 6mm cross section 2mm and Shore 90 -
My first thoughts were contamination too - but I have replaced all of the o-rings, cleaned everything and am only using 100% silicone oil - but it still happens - I am going to try several materials -

 

[OTmachine]

Sounds like it needs to be modified for back-up rings.

 

[davee1]

The current o-ring is id 6mm cross section 2mm and Shore 90 -
My first thoughts were contamination too - but I have replaced all of the o-rings, cleaned everything and am only using 100% silicone oil - but it still happens - I am going to try several materials -

cool. Probably not silicone orings tho because they are too squishy. But teflon 90durometer is really tuff stuff.
And maybe try a 104 size for fun lol.

 

[M Volle]

Sounds like it needs to be modified for back-up rings.

This is a relatively inexpensive rifle - yes backup rings and tighter tolerances would be ideal but I'm not sure at what price point they become practical - I think that in this case a slightly larger cross section to take up the width of the groove may work - even if I need to make the groove correspondingly deeper - or I can remake the part - but if I can find an alternate o-ring that works, then it is a viable solution for anyone else with an Avenge-X

 

[nervoustrig]

The other failure I am seeing, I'm not so sure about - the o-ring becomes glazed or polished on the outside, deforms to have a slightly crowned top edge and gets very hard - they crack when removing and some have shattered into several pieces.

O-ring hardening in PCPs is usually the result of thermal stress. Common with regulator O-rings on the low pressure side, for example, due to the temperature rise associated with the pressure replenishing after each shot. Viton/FKM is a good choice if you are experiencing what seems to be unacceptably poor longevity, but in most cases good old Buna-N will last a long time.

True that an incompatible lubricant is another potential cause but it's pretty far down on the probability spectrum. The common O-ring materials (Buna-N, FKM/Viton, and polyurethane) are pretty resilient to the lubricants typically used on airguns.

Viton looks like a good alternative but can swell with any moisture (which shouldn't be in the gun anyway)

You will definitely encounter swelling with Viton but it's more of a nuisance than a problem. For example if you intend to disassemble and immediately reassemble, the swelling may prevent you. Either give it overnight to allow the outgassing to occur (return to normal size) or plan ahead to have spares onhand to swap out for a fresh one.

 

[MattR302]

Thanks OP!!

I am currently troubleshooting leaks on a new-to-me Avenge X. Does anybody know if this kit fits the X; and/or if it is missing any of the ones highlighted above?