Modski66
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Post by Modski66 on May 18, 2023 11:55:26 GMT
Just found an exploded picture of the real valve parts. The BBU slides over the cylindrical part of the valve body; when the hammer falls, the valve stem is knocked off the PTFE seal and allows gas into the centre of the stem, past the green o-ring which then comes out behind the sprung loaded nozzle. The gas pushes the nozzle forward into contact with the bb at the top of the magazine the gas pressure then forces the bb out of the magazine and on its way. Presumably the gas that does not go into the stem and forward will squeeze through the annular gap between the back of the stem and the middle of the black end cap and head backwards to activate the BBU. Everything in the picture is present in my pistol's valve. The balancing of the two gas flow paths will be critical to correct functioning, so what is the variable that seems to have been affected, and how on earth do I check/fix it? www.pullthetrigger.co.uk/Umarex-Walther-PPK-Valve-Unit
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Post by HeadHunter on May 18, 2023 18:43:12 GMT
WOW ! I've had a look at the pictures and must admit that I still am none the bloody wiser, I'd have to have it in my hands to work it all out mentally as I look at it and just end up scratching the ol' noggin and simultaneously sighing "WTF !"
Right, I've been sitting and staring at that bloody picture for the best part of an hour now and I'm still struggling, so many questions ! I might just buy a PPK just to have a look, lol. I'm one of those types of people that need to have it in my hand, so that I can see it's function, I'm looking at the pictures and asking where does that hole go ? (to the front or to the rear), Is the valve body just an empty cylinder with a screw thread at each end or does it have an inner compartment ? (where the valve stem would feed through), Where the fukkin hell are you going to attach the BBU to and how will that work ? (I honestly can't see where it would fit).....
I'm going to have to take a back seat on this one buddy, I've got no experience with the PPK and it's so very different to any other blowback pistol that I own that any suggestions that I could give you would be either be wrong (90%) or just plain stupid (the remaining 10%).
It's given me a headache just looking at it I can't begin to imagine how many paracetamols you've gotten through, lol
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Modski66
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Post by Modski66 on May 18, 2023 21:03:03 GMT
More head scratching and tinkering this evening and a little bit of progress by working on the slide resistance, lubrication and cutting bits off the return spring until it was working better. 😁 Thought I would refit the original piercer, and went almost back to square one. 😭
Still can't see why the gas valve is misbehaving, the fps seems to be higher when it won't recock, and lower when it will. 🫨 Maybe the valve spring is snagging or something... 🤔
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Post by HeadHunter on May 19, 2023 7:02:48 GMT
I thunk about it all again last night (information takes a little while to sink in at my age, lol), the 'balance' between power output (FPS) and blowback must be the set by the differential between both springs (recoil and disconnector). If the hammer fall is consistent then it should have a repeatable performance even if that balance goes awry (one spring becomes weaker), the only thing that I can think of is that there's a 'snag' somewhere or too much sloop in the play that's causing the internals to kink or maybe the parts are locking together and NOT unlocking cleanly (or quickly enough). The thicker spring out of the two will be the last to compress when force is applied but the first to expand once tension is released, so I think that it must be the 'disconnect' spring that sets the 'balance' between FPS and blowback, so if any spring is responsible for the issue then all information points to it being that one. I noticed that it's a flat ground spring, so that implies that it has to have a constant and equal flat pressure applied at both ends, I'm wondering whether it's kinking slightly under pressure (for whatever reason) and pushing the interference fit between the valve stem and top hat out of alignment slightly which will either be causing a poor fit (resulting in low FPS and good blowback) or sticking (which would cause a high FPS and poor blowback). Just a guess buddy (but knowing you as I do, you're probably thinking the along the same lines too, lol)
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Post by HeadHunter on May 19, 2023 7:15:16 GMT
Maybe (just had a thought) using lapping paste on the connecting point between the valve stem and the top hat (stick the valve stem in an electric drill) might grind the fit into a better shape, I wonder if there's been a small amount of metal movement caused by the end of the valve stem going into the top hat slightly off centre resulting in a raised sticking point that causing a delay in its opening and any subsequent CO2 rerouting to the BBU.
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Modski66
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Post by Modski66 on May 19, 2023 9:18:25 GMT
They don't make 'em like they used to...
My old PPK had a broken lip on the bb feeder nozzle, no spare available, so I ended up buying a complete valve assembly. OBVIOUSLY I retained the old one, which I have just tried using with the newer feeder nozzle installed, and it appears to have sorted it. There is a caveat that the old valve body is snagging on the newer slide somewhere, but as it is currently gassed up, I can't fully investigate. The snagging is when the slide is fully forward, so the BBU is really having to work hard to get the slide moving, but I can easily fire off 12+ shots without pause before it runs out of puff. I am now curious about what is different between the valves; the front end of the stem is pointed on the new one, but flat on the old one, as in the picture linked above. It will have to be a forensic strip-down of both valves to work out what the root cause is though.
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Modski66
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Post by Modski66 on May 20, 2023 0:16:12 GMT
The snagging was an easy fix once I found it. The top back edge of the the BBU was the problem, just needed some filing and smoothing. So far working flawlessly. 😁
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Post by HeadHunter on May 20, 2023 7:51:59 GMT
The snagging was an easy fix once I found it. The top back edge of the the BBU was the problem, just needed some filing and smoothing. So far working flawlessly. 😁 Excellent ! Well done that man
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gunman1964
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Post by gunman1964 on May 20, 2023 8:08:18 GMT
Im glad you got it fixed modski ... i havnt had time to even have a look at mine yet ..... hopefully over the weekend. i must admit im not overly impressed with the build quality on these ppks ... i now have 3 of them ALL of which were bought with problems i managed to salvage 1 pistol out of the first 2 by swapping parts and filing/polishing /cleaning and i hope i can fix this one with some of the parts left over. they do look nice though lol
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Modski66
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Post by Modski66 on May 20, 2023 9:11:58 GMT
It's funny, I was very taken with the Sig P365, impressive design to get a 12g capsule in a full size drop out magazine etc, but I am finding the PPK/s nicer to hold and look at, it's just more elegant, even if it is quite old technology. It also has the historical value of being the first blowback co2 replica, so quite a trailblazer. 😁 I am getting a bit of a Bond collection going on now, with the CP99 and the Predom Lucznik copy of the Walther LP53.
Wonder if I can pick up a tuxedo at one of the local charity shops? 🤵
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gunman1964
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Post by gunman1964 on May 20, 2023 9:22:34 GMT
Ha Ha Ha ...... I think a tux might be a touch over the top for your local boozer though mate lol i do agree, the ppk is a nice gun ... if they did one with woking safety and full drop out mag i would have one ....
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Modski66
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Post by Modski66 on May 20, 2023 9:49:50 GMT
Me too!
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twodoctors
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Post by twodoctors on May 20, 2023 11:03:24 GMT
The snagging was an easy fix once I found it. The top back edge of the the BBU was the problem, just needed some filing and smoothing. So far working flawlessly. 😁 Which part? Hopefully I can fix mine also...
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Post by Darkshadowhawk on May 26, 2023 18:46:26 GMT
Mine appears to have the same issue, I purchased mine pre-owned. Appears to blowback fine for around 1 mag then it's almost as if the slide isn't going far back enough with the blowback to cock the hammer, so it requires manual cocking of the hammer to fire. The power still seems there in the shots however and keeps firing for multiple shots. I assumed it was something to do with the spring causing too much resistance but I'm not very technical with these sort of things haha.
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Modski66
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Post by Modski66 on May 27, 2023 6:48:48 GMT
I am afraid that I still don't know what it is about the old valve that I fitted that fixed the blowback problem. 🤔 It isn't resistance caused by the recoil spring, nothing I did on mine made any difference.
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