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PostPosted: Fri Jan 16, 2015 5:25 am 
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Location: Vancouver
Thanks for keeping on giving Chevota, most useful information! Sounds like you've achieved some really nice results. I'd be glad to see a picture if it's not too much trouble. Type of plastic and thickness if those are available might be useful too. With the plastic I used I'm not sure it'd stand up to a tight fit, and it'd have to be at least two full wraps to get it that snug anyway. So I'll keep looking for something a bit thicker and do as you're suggesting. Hmmm... now I'm wondering about the covers of those cheap 3-ring binders, the ones which always seem to find a way to slip off even quite level surfaces. Bet those are slippery enough, and plenty tough plastic too. My wife's always getting new binders now that she's back in school so maybe I'll see if she has any to donate.

I'm not interested in performance in an absolute sense, more consistently useful performance. So yeah, steady is good. But I have the PCPs for scoped use, no intention of putting a scope on the QB57. It's to be about a 30 metre and closer sort of thing for my use so the Burris Fastfire III will be fine. And I seem not to struggle with just that in making nice enough little groups so still not interested in adding weight. Quiet and comfort are the focus now.


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PostPosted: Fri Jan 16, 2015 10:23 am 
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GerardSamija wrote:
Just wish I could do single point threading on it...

Oh yes, that one is niggling me. I have a plan, but like many of my plans it's probably over ambitious and slow to happen.


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PostPosted: Fri Jan 16, 2015 3:46 pm 
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There has been much written on port size and piston weight on british and s.a. forums. I personally believe that there is a lot more efficiency to be had out of springers, we now have computer programs to juggle the variables. What we don't seem to have is any this-century measurement tech being used to accurately measure pressure rise/pellet departure/air cushion stats. Much of springer design is based on 19th century technology, tube/spring sizes were fixed and metallurgy not advanced. Who has all the expertise on tiny air pressure sensors? If someone was to design/build a test sled that could measure all variables, i would donate to that in a heartbeat. The "major" manufacturers do not have the money/desire for design advancement and any new tech is instantly copied, so answers lie in the hands of skilled hobbyists worldwide.


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PostPosted: Sat Jan 17, 2015 12:09 am 
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Posts: 1079
Location: Calgary, Alberta
morris wrote:
There has been much written on port size and piston weight on british and s.a. forums. I personally believe that there is a lot more efficiency to be had out of springers, we now have computer programs to juggle the variables. What we don't seem to have is any this-century measurement tech being used to accurately measure pressure rise/pellet departure/air cushion stats. Much of springer design is based on 19th century technology, tube/spring sizes were fixed and metallurgy not advanced. Who has all the expertise on tiny air pressure sensors? If someone was to design/build a test sled that could measure all variables, i would donate to that in a heartbeat. The "major" manufacturers do not have the money/desire for design advancement and any new tech is instantly copied, so answers lie in the hands of skilled hobbyists worldwide.


Morris, you're brilliant! The second I read this, I pictured a barrel with a dozen tapped holes in a row and pressure sensors screwed into them. In fact, I bet a low-tech approach, using analog pressure gauges equipped with marker pointers, would work. I'm betting some of our oilfield specialists would know what I'm talking about and, better still, know where to find them.
Then, I wonder if mounting a row of peezos (piezometer) along the tube would be able to detect the movement of the piston through vibration. I have a buddy of mine who makes these and they are designed to detect wire breakage in suspension bridges, so I know they are very sensitive.

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PostPosted: Sat Jan 17, 2015 1:10 am 
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Location: Alberta Canada
Handyguy wrote:
morris wrote:
There has been much written on port size and piston weight on british and s.a. forums. I personally believe that there is a lot more efficiency to be had out of springers, we now have computer programs to juggle the variables. What we don't seem to have is any this-century measurement tech being used to accurately measure pressure rise/pellet departure/air cushion stats. Much of springer design is based on 19th century technology, tube/spring sizes were fixed and metallurgy not advanced. Who has all the expertise on tiny air pressure sensors? If someone was to design/build a test sled that could measure all variables, i would donate to that in a heartbeat. The "major" manufacturers do not have the money/desire for design advancement and any new tech is instantly copied, so answers lie in the hands of skilled hobbyists worldwide.


Morris, you're brilliant! The second I read this, I pictured a barrel with a dozen tapped holes in a row and pressure sensors screwed into them. In fact, I bet a low-tech approach, using analog pressure gauges equipped with marker pointers, would work. I'm betting some of our oilfield specialists would know what I'm talking about and, better still, know where to find them.
Then, I wonder if mounting a row of peezos (piezometer) along the tube would be able to detect the movement of the piston through vibration. I have a buddy of mine who makes these and they are designed to detect wire breakage in suspension bridges, so I know they are very sensitive.

Pembina Controls, Pyramid Insturmentaion. Good starting point for you.

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PostPosted: Sat Jan 17, 2015 8:26 am 
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Sure would be a fun project to work on. Could be coupled with some theoretical/computational modelling work and would make a nice phd for someone.


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PostPosted: Sat Jan 17, 2015 8:49 am 
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Location: Northeastern Ontario
morris wrote:
The "major" manufacturers do not have the money/desire for design advancement and any new tech is instantly copied, so answers lie in the hands of skilled hobbyists worldwide.

I don't know that I'd go so far as to say that the folks at Weihrauch or Air Arms don't have the money or interest in advancing the design of the guns they make. It hardly makes sense for them to ignore it. At the same time they don't promulgate their research and development until they produce new designs for manufacture. Walther has demonstrated this with their LGV and LGU rifles. It's a competitive market, especially in Europe and the U.K. The technical sections of the U.K. airgun rags often have information about "spring piston dynamics" which is arcane for most readers, often old news to experienced airgunners, or just mostly irrelevant for significant design changes. These discussions do, however, give impetus to tinkering and making improvements, which are there to be had, in all airguns.


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PostPosted: Sat Jan 17, 2015 11:14 am 
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I remember reading when diana airguns hired an automotive engineer on contract to design their t06 trigger. I think that the manufacturers are only 'tinkering' with established designs. All of the airgun companies are small, financially, except for the state-owned china companies. Perhaps a volute spring in an ultra short stroke tube, or a valve as mentioned previously, or a small expansion chamber, or a piston de-accelerator, or a rising rate spring, or a ......... Accurate measurement of all the variables would make it easier to move forward.


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PostPosted: Sat Jan 17, 2015 11:55 am 
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Location: Northeastern Ontario
morris wrote:
All of the airgun companies are small, financially, except for the state-owned china companies.

Small? Compared to ...? They compete with one another. Any improvement in design would be quickly adopted to improve competiveness. Chinese companies don't even belong in the discussion as they copy rather than innovate.
morris wrote:
Perhaps a volute spring in an ultra short stroke tube, or a valve as mentioned previously, or a small expansion chamber, or a piston de-accelerator, or a rising rate spring, or a .....

It would seem that these ideas are alien to the airgun companies, that they would have no interest in them, and that they actively eschew new ideas. That would make them rather short sighted. On the other hand, the dreams of amateur tinkerers could breath new life into what must be a rather moribund (and small) industry and, if only they would listen, new and much better air guns would be born. The alternative might be for those who know what must be done to do it themselves and build a better mousetrap, as it were.


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PostPosted: Sat Jan 17, 2015 12:27 pm 
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While I applaud the idea of using modern equipment and test methods, the last extensive set of testing wasn't done in the 19th century, but by the Cardews in 1995, only 20 years ago (ie late 20th century).... Ever since, people have been skeptical about their proof that controlled combustion (as opposed to dieseling) is one of the main sources of power in springers, and I'm one of those that finds it hard to believe the a gun could consistently combust traces of oil over hundreds or thousands of shots, but it is pretty hard to deny what happened when they removed Oxygen from the process and lost a huge percentage of the power....

There is no question that air compression in springers is an Adiabatic process, raising not only the pressure of the air, but the temperature as well (by hundreds of degrees), completely the opposite of what happens in a PCP where the gun cools with repeated firing because the air is expanding.... Any attempt to better understand how springers work, must, IMO, start with measuring and confirming that process, which is one of the reasons that springers, air volume for air volume, are so efficient compared to any other airgun type....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sat Jan 17, 2015 1:04 pm 
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How i wish that someone with the knowledge, skill and ingenuity of mr. sterne was actively researching springers. My own crude testing showed no fps loss with a small china springer [synthetic seal] thoroughly and completely degreased. I will get around to a small pre-chamber, army recoiless rifles [cannon] used that to some effect. Cardew designed a low pressure pumper, not sure if that was a success or failure.


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PostPosted: Sat Jan 17, 2015 1:16 pm 
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Cardew's make a distinction between what they call "pop-gun" springers of low velocity and pressure, and the ones that rely on combustion for a large percentage of their power.... You are not the only one who has tried to disprove the Cardew's claim, but to the best of my knowledge, nobody has duplicated their Nitrogen only atmosphere experiment to refute it....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sat Jan 17, 2015 1:30 pm 
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Sounds like that really needs to be looked into. I can't imagine consistent combustion as a high percentage of power without a reliable way of introducing a consistent amount of fuel into the chamber on each stroke. Having it happen as a "lucky accident" seems remarkably unlikely! Although, alternative explanations for a loss in power using nitrogen as the working gas don't immediately spring to mind. The whole thing just gets more and more fascinating.


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PostPosted: Sat Jan 17, 2015 2:07 pm 
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Presumably the "reliable way" of introducing fuel, as I understand it, was distribution of a molecule thick layer of oil residue by the edge of the seal on the cocking stroke, which is then (partially?) scraped away by the piston on the compression (firing) stroke, and combusted....

I agree, it makes little sense to be so consistent.... but find no other way to explain the Cardew's results.... It has been suggested that it could be water vapour flashing to steam, but that can't be the cause as water vapour already IS "steam", and besides, it takes energy to make the state change from liquid to gas (and a lot of it), it doesn't release energy....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sat Jan 17, 2015 4:06 pm 
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Location: Vancouver
While it is impossible to ignore the sometimes dramatic increases in velocity one sees (and hears!) with dieseling, I do not understand how this effect can be rendered usefully in terms of shot-after-shot consistency. For instance, adding a drop of a vegetable-based bicycle oil to my QB57 I have seen velocity jump to a ridiculously high velocity, almost 800fps with JSB Heavy pellets. But that's one shot, it's loud and the gun feels harsh, and I'd have significant worries about the effects of such obvious explosions over the longer term. Probably fatigue and crack the piston if not worse. A 300fps+ jump in velocity may be desirable for some shooters, but then the next shot is much slower, and the shot after much slower still, as the oil is burned off. So how is dieseling a useful strategy for an accuracy-dependent sport? Even if someone could deliver a precise dosage of an oil to the cylinder prior to every single shot (and wanted to engage in such a tedious activity), it seems unreliable at best, destructive or even dangerous at worst. And yet I see posts all over the web about how dieseling is now considered part and parcel of modern, high-powered spring airgun use. Colour me confused.


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