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Thread: I don't believe a TP smaller than 3.0mm ever works in a 12FP springer....

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    I don't believe a TP smaller than 3.0mm ever works in a 12FP springer....

    I just don't think it can flow properly and make the power... irrespective of length etc, I've never found anything less that 3.0mm to be efficient, and generally unless the port is exceptionally long (like an LGV), 3.2 is a more usual minimum starting point.

    Even 25mm cylinder guns with fairly heavy pistons found 3.0mm too tight, and had to open out to 3.2. And larger bores 26/28/30 3.2 is always too small.

    Discuss.
    Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.

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    look no hands is online now Even better looking than a HW35
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    Interesting stuff, I love the way you share your many years of research and tinkering skills with us

    Pete
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    I've always imagined that for sub 12 ft/lb there must be a maths formula you could use to determine the perfect diameter and length of port if you know how much pressure the compression tube is creating, is this flow rate calculator of any use ?

    https://www.copely.com/tools/flow-rate-calculator/

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    Quote Originally Posted by Shed tuner View Post
    I just don't think it can flow properly and make the power... irrespective of length etc, I've never found anything less that 3.0mm to be efficient, and generally unless the port is exceptionally long (like an LGV), 3.2 is a more usual minimum starting point.

    Even 25mm cylinder guns with fairly heavy pistons found 3.0mm too tight, and had to open out to 3.2. And larger bores 26/28/30 3.2 is always too small.

    Discuss.
    What is the factory 80 size?

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    Quote Originally Posted by Gunfun View Post
    I've always imagined that for sub 12 ft/lb there must be a maths formula you could use to determine the perfect diameter and length of port if you know how much pressure the compression tube is creating, is this flow rate calculator of any use ?

    https://www.copely.com/tools/flow-rate-calculator/
    I have three formulae for transfer port diameter, and they never agree with each other

    There's too many unknowns to make such calculations reliable.

    The flow rate calculator in the link is for fluids, not air.

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    Quote Originally Posted by Barryg View Post
    What is the factory 80 size?
    I think the 80 has a 2.8mm TP standard from the factory, two of mine do.
    Les..

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    Out of interest what size TP as the AA Pro/elite got ?.
    Les..

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    This has the makings of an interesting thread. I'd like to try & get an understanding of how the variables interact with one another.

    Noticed a comment "The flow rate calculator in the link is for fluids, not air."earlier on in the discussion but isn't air classed as a fluid? I think all gasses are regarded a fluids. They are complex in some respects as they are compressible fluids as opposed to liquid fluids which are generally regarded as incompressible.

    Looking forward to learning a bit about flow rates & fluid dynamics....

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    Quote Originally Posted by BTDT View Post
    I have three formulae for transfer port diameter, and they never agree with each other

    There's too many unknowns to make such calculations reliable.

    The flow rate calculator in the link is for fluids, not air.
    I thought in physics fluids were considered liquid, gas (air) or plasma.

    https://en.wikipedia.org/wiki/Fluid

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    Quote Originally Posted by trajectory View Post
    This has the makings of an interesting thread. I'd like to try & get an understanding of how the variables interact with one another.

    Noticed a comment "The flow rate calculator in the link is for fluids, not air."earlier on in the discussion but isn't air classed as a fluid? I think all gasses are regarded a fluids. They are complex in some respects as they are compressible fluids as opposed to liquid fluids which are generally regarded as incompressible.

    Looking forward to learning a bit about flow rates & fluid dynamics....
    Gasses are indeed regarded as fluids but, being compressible, will behave very differently in a transfer port.

    The flow rate link would be spot on if we filled our springer cylinders with water, though.

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    My bachelor's and master's dissertation were based around fluid dynamics, simulation and modelling. One on IC cylinder head flow and one on external aerodynamics. Can be very interesting, but when it comes to transfer ports I would just stick with physical testing. Too many variables and life is too short

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    Quote Originally Posted by BTDT View Post
    Gasses are indeed regarded as fluids but, being compressible, will behave very differently in a transfer port.

    The flow rate link would be spot on if we filled our springer cylinders with water, though.
    The more I look at tuning springers, the more mind boggling it becomes.

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    When writing my earlier post the idea of filling the cylinder ahead of the piston with water crossed my mind too. I thought if I suggested it someone might say'ok, you first' & I wouldn't fancy trying to dry out intrrnals of a springer, even a clunker of a springer. Still as a theoretical model it would be interesting if the weight of the fluid could somehow be factored out & the empirical perfomance evaluated with changes being introduced step by step so the effects of them could be measured. It would take out any varriability arising from the clmpressability of the air. But how it would translate into the real world is anyones guess so I think the advice that life is too short & its probably better to just roll up your sleeves & get cracking ks good advice.

    It will be interesting to see any results from those that have carried them out.......standard rifle v port diameter, differant stroke v port diameter or variability with port volume etc. Its a big topic........but very interesting.

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    Not tried this my self yet.

    I was thinking about making a brass insert as a transfer port, my idea is to make it tapered down from compression tube, with a convex entry, so no sharp corners, highly polished [mirror]. My theory is based on - as a youth I used to polish cylinder head ports on my motor bikes & it did improve performance - better intake/exhaust flow. just an idea at the moment?

    PS. in engineering terms the word fluidic covers both liquid & gas.
    Last edited by cringe; 21-03-2021 at 10:50 AM.

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    Quote Originally Posted by look no hands View Post
    Interesting stuff, I love the way you share your many years of research and tinkering skills with us

    Pete
    Yes, Pete, I also think it's brilliant that we have so many people like Jon who will put the work in, experiment etc. and then share their findings with all and sundry. Like he says, anything tighter than 3mm probably creates too much choking effect on most layouts, but I only base that comment on what I've learned from these many great people who are willing to share their knowledge.
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