Tuning Vs Performance

Discussion in 'Piston & Spring' started by skires, Oct 9, 2018.

  1. Nomads HFT

    Nomads HFT Well-Known Member

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    Recoil displacement is indeed the compression stroke multiplied by the piston/spring mass and divided by the rifle mass.

    In practice, the piston mass that contributes to recoil is nearer a third than a half. I think this is because the masses of the rifle and piston are highly dynamic during the stroke, as more of the spring wire starts to move and transfers more and more of its mass from the rifle to the piston.

    I believe that perceived 'sharpness' of recoil is a function mainly of the force placed on the piston at the start of the compression stroke, and am not surprised you describe your rifle as snappy, as the force on the piston at the start of the stroke is in the order of 830N (Newtons). By way of comparison, my TX200 with an 85mm stroke places a force of 650N on the piston, and I doubt anyone would describe it as snappy.
     
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  2. skires

    skires Well-Known Member

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    I think we're getting there.

    If we actually need more proof ... Give most springer shooters a PCP ... and they still hit **** all. So good luck to them finding a springer tune that makes them knock down more targets.:D

    Most FT and HFT shooters can't see level let alone worry about sea level.

    I think this sort of sums up a lot of what I try and say about all aspects of tin chicken shooting.

    Hence 'Woods for Trees'.

    We are flirting little pellets at targets out to 55 yards. A tad of wind sends them all over the place. If shooting a springer then a slight lack of consistency in the shot release can cause a miss.

    If all the techno details tickle your fluff then that's absolutely brilliant ... but accept the basics that knocking targets down means getting the gun to fit YOU, and then you get used to the gun, and then you learn what happens in different wind conditions and when you are forced out of your comfort zone.

    The techno babble fills pages on internet sites but it won't fill your trophy cabinet. It is great to read though whilst supping a brew, so long may it continue.

    P.S. The great news for the tuners is that no matter what is said in these types of threads ... I absolutely 100% guarantee that in the next couple of months on several internet sites ... there will be many threads along the lines ... " I'm going to shoot springer in HFT/FT ... What is the best tune I can get for my rifle? ". So keep the lathes powered up boys ... You'll be busy for a while yet. :D

    P.P.S I totally understand, and it's great, that for some it's not just about knocking down targets ... It's about understanding how the rifle works and seeing if it can be made to work better ... or being made 'easier' to use. That's a big part of a number of sports for some participants ... and that's fine.
     
    Last edited: Jan 21, 2019
    vangard likes this.
  3. Scott Hull

    Scott Hull Member

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    I avoid calculus and that looked like an integral problem. I had done a rough numerical integration in my head to get the 1/2. But I just did a little research and I believe that you are correct. A solution that I found does show 1/3 of the spring mass for spring-mass systems. So 1/3 would be a better number to use:

    Effective mass (spring–mass system) - Wikipedia

    Just to be clear, the 1/3 refers to just the spring mass. For the piston itself, it's 100% of it's mass.

    Edit: After thinking about it some more, I believe that the 1/3 effective mass is only applied to the dynamic response. For simple mass displacement, 1/2 should be the correct value. It becomes a static problem, with a before and after state.

    Example - When a spring extends from 3" height to 6" height, the CG of the spring moves from 1.5" out to 3". We are moving the CG of the spring 1/2 as far as we move the CG of the piston.
     
    Last edited: Jan 21, 2019
  4. Scott Hull

    Scott Hull Member

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    I used to work as a mechanical engineer. For me, that part of it makes airgunning all the more fun/interesting.
     
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  5. skires

    skires Well-Known Member

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    I get that Scott ... hence my comment on the PPS above.

    I worked as a Senior Engineer in a quality lab and it was my job to try and figure out what had gone wrong and how things could be improved ... so I totally get that part of springer shooting and I really do enjoy reading all about the technical side of the springer and tuning etc.

    My top marks at Poly were in Mechanical Engineering. I loved it. That was when schools were schools, colleges were colleges, polytechnics were polytechnics and there were about half a dozen universities in the country. In Stoke ... schools in the late 60's and early 70's were where PE teachers were paid well to beat kids with bendy canes. Colleges in the late 70's were where you learned what cannabis and beer did to your body and how unbelievably filthy 16 and 17 year old Stoke girls were, but polytechnics in the very late 70's and very early 80's were where you realised that you'd got two years left in your apprenticeship to actually work hard, try and get a degree level of qualification and get a job aged 21. Now most chip shops have been turned into universities so you can get a degree in frying a mars bar, and most cities have nearly as many universities as tattoo parlours.

    From a springer user point of view ... I've found, beyond a pretty early stage point, any extra tuning gives such a minimal improvement in performance, compared to gains made from stock fit and lots of practice and learning that rifle and wind and small variances in position etc, that it's no great advantage ( from a scorecard POV ).

    I just try and get that message across to people that struggle to hit things and then think a mega tune will help them hit lots more.
     
    Last edited: Jan 21, 2019
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  6. Amac

    Amac Active Member

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    Happy days indeed Col!!!
    Brilliant post.
    In my opinion, the bottom line is that regardless of the state of the action tuning wise, as Dan has commented, stock fit, in my own opinion, is probably more important.
    Once the gun fits properly, its just about practise, practise and more practise. Then some more practise, swiftly followed by a touch of practise.
    Andy
     
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  7. Joha

    Joha New Member

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    terryn likes this.

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