If it was made from aluminum, then it would have an aluminum piston hammering an aluminum seat (receiver). That seems like a bad combo for longevity.
Dave
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Huben Any issues or problems with Huben gk1 please share your experience
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Dave
Yeah that part should've been made out of some stronger material. For some important details on it I recommend checking out Gregor's disassemble video.
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I had it on 350 at first. The issue started at around 300 bar. But it's rated to operate at that pressure. Also I never shot it at full power.
Which version do you have? Because my V3 doesn't have a brass part in it. The pressure is adjusted by the grub screw of the trigger unit which pushes on the steel pin of the closing valve unit. The V1 has that brass part I believe.
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Yeah, mine is a V1. Maybe that’s the difference, hmm. So it may be possible something wasn’t aligned correctly.
You are correct that it should operate fine at the manufacturer’s recommended fill pressure.
Can you post a picture of the other parts while you have it apart? It would be interesting to see the difference between v1 and v3.
Thanks,
Dave
You are correct that it should operate fine at the manufacturer’s recommended fill pressure.
Can you post a picture of the other parts while you have it apart? It would be interesting to see the difference between v1 and v3.
Thanks,
Dave
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I'd agree. I was simply thinking about replacing the part with something easy to machine. I was only looking at the part breakdown, which isn't all that clear. I see the string of parts 19-28, but not exactly where the stack goes. Obviously it somehow is mounted in the receiver, which is aluminum.
So what metal would be appropriate? Brass is heavy, and soft but easy to machine. Steel beating on aluminum seems worse in a way. Or is some sort of plastic the best material?
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Peek or glass filled peek would be my recommendation, looking at the pic, the material already may be peek? Similar color at least.
A step up from that may be PAI. They're quite similar, although glass filled peek would beat both.
www.makeitfrom.com
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-Matt
A step up from that may be PAI. They're quite similar, although glass filled peek would beat both.
PAI vs. PEEK :: MakeItFrom.com
www.makeitfrom.com 30 GF PEEK vs. PEEK :: MakeItFrom.com
www.makeitfrom.com -Matt
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Thanks, definitely a different setup from the original. I can see what you mean about adjusting the screw (I assume resides in the guard) out before assembly.
Dave
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As far as using a different material, I don’t think we are quite to the point of needing something different. This is the first I’ve heard of this happening. Without knowing what created the failure, I’m not sure it requires a material change.
If it were the wrong material however, sometimes going harder/stronger is not the answer. If it shattered due to closing impact, a softer, more impact tolerant material may be the answer.
If we continue to see this type of failure, corrections may be necessary.
Dave
If it were the wrong material however, sometimes going harder/stronger is not the answer. If it shattered due to closing impact, a softer, more impact tolerant material may be the answer.
If we continue to see this type of failure, corrections may be necessary.
Dave
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No, hardness alone does not determine brittleness. While hardness is a measure of a material's resistance to indentation or scratching, brittleness refers to a material's tendency to fracture or break when subjected to stress or impact.
*edit* to elaborate, tensile strength doesn't dictate impact strength or flexural strength. Material science especially with thermoplastics is complex.
Example, delrin(top) vs peek(bottom): delrin will fracture much sooner than peek from impact and bending, however it's a much lower tensile strength...
-Matt
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It’s funny you mention aluminum for the closing valve. The original closing valve in the Huben k1 is aluminum. 
Nary a problem with the closing valve until it dropped off the table (during a re-seal) and broke the retaining clip.
Nary a problem with the closing valve until it dropped off the table (during a re-seal) and broke the retaining clip.
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When I first saw the plastic part, I thought the top surface did the sealing. Now I see more clearly there's a groove on the angled edge on the plastic GK1 part and the aluminum K1 part. Where is the seal, or is this more like a hammer? The groove looks like a vent or leak. What is the function of the groove? Hmm, there's quite a bit I don't understand about this design. I'd like to know more.
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The top (angled) part does do the sealing. The groove is lets air bypass the valve to repressurize the opening valve. It’s the only valve I know in the airgun world that is designed to “leak”. A simple yet genius design.
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It is a purpose created leak. Not enough to keep the opening valve from resetting but enough to allow the opening valve chamber pressure to equalize (once reset). This equalization allows the closing valve to reset to it’s ‘open’ position.
Oops, looks like it got answered already. lol
Dave
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IMO, that piece should be metal due to that angle and seat dimensions alone, and either what it slams against or itself should have a thermoplastic seat. That nature of that angular geometry just looks prone to..what we see in reply #234.
You can see the indentation where it seats/slams. Reducing the OD of that if possible would also reduce the damage from repeated impacts, seems quite unnecessarily large.
Does the OD of that metal piece have to terminate to such a large degree? I know it breathes but, I'd rather see it taper where the plastic piston seats, thus reducing the impact forced on the outer circumference, thus reducing the stress on that weak spot...having it transfer energy more center lined would mean the whole piece absorbs the energy, opposed to that..poor outer edge...so I could see staying plastic, with a reduced OD on its seat/where it slams.
-Matt
You can see the indentation where it seats/slams. Reducing the OD of that if possible would also reduce the damage from repeated impacts, seems quite unnecessarily large.
Does the OD of that metal piece have to terminate to such a large degree? I know it breathes but, I'd rather see it taper where the plastic piston seats, thus reducing the impact forced on the outer circumference, thus reducing the stress on that weak spot...having it transfer energy more center lined would mean the whole piece absorbs the energy, opposed to that..poor outer edge...so I could see staying plastic, with a reduced OD on its seat/where it slams.
-Matt
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Is the groove on the top surface a seal, or is the angle on the side? On the K1 it is the angled side, not the top, at least according to @Pale_Rider .
If that were true, on the GK1, then what's the top groove for? And what's the edge groove for? Wouldn't there be a leak structure designed from one groove to the other? Or (as usual) I'm not understanding this...
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Can you post a pic of the top of the valve? The top of the valve shouldn’t matter because it’s not doing any sealing. Only the angled portion directly below the top is sealing.
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I haven't taken mine apart yet. Was hoping to learn what the top groove was, besides being a potential failure point. At the moment, mine is shooting at 37FPE average for a magazine with a 30MPa fill. (28.4 grain NOE slugs.) Rather not crack it open unless I need to. If needed (or when needed) I'll open it. Still in the honeymoon stage
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