Air fittings...

Discussion in 'General Airgun Chat' started by RobF, Nov 22, 2015.

  1. RobF

    RobF Administrator Staff Member

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    I know, call Best fittings, but it's sunday and i'm pondering.

    I want to be able to measure the cylinder pressure of a rifle while shooting. That's no issue, i could put a QF onto a gauge and leave it on the gun. But I also want to use the same gauge when I fill.

    So what I want is some sort of tap, that I can put upstream of the gauge in between gauge and dive bottle, close it after filling, purge the line, disconnect and the gauge not to budge. Effectively like another bottle tap, only not so expensive and difficult to connect.

    Does such a thing exist considering we're talking 2-300 bar?
     
  2. johnharper

    johnharper Member

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    Yes Rob this would be do-able
    using a high pressure ball valve either an 1/8 bsp or a 1/4 bsp with fittings and the gauge attached to the ball valve
    john
     
  3. Tench

    Tench WHFTA World Champion 2016.

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    I have some 400bar rated ball valves on my reg setter so yes they do exist, bulky and not cheap though!
    you could use a T piece fitted in place of the guns filler with a gauge in one side and a daystate style filler in the other.
     
  4. RobF

    RobF Administrator Staff Member

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    Here's what I was thinking...
     

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  5. RobF

    RobF Administrator Staff Member

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    Many thanks to John Harper for lending his expertise and assistance, this is now up and running.

    First I tested the whole assembly connected to an air tank, for leaks, then closed the tap on the tank so just the air in the assembly was there (i.e. it wasn't getting topped up by the tank anymore), it held pressure, so i swung the ball valve... slight loss of 7 bar as that happened but then she held to the decimal. Then ran the purge valve on the tank, still held... then disconnected... and she's holding, to the decimal. In fact she's gone up at tad as the tank has just come out of the boot and gone from night time Bournemouth's 11.3 degrees to Miss England's preferred room temp of 21.0 degrees C.

    [​IMG]

    The whole assembly is on quick fill adapters so i can swap cylinder adapters for different bottles and various other elements I want to test. By building blanking plates for regs etc I can leak test every stage of the rifles, which saves a lot of guess work, because sometimes it might just be a cheap o-ring on a bottle or a washer instead of the gun itself.

    I can also shoot with this attached and see where there's any oddness or consistency in the pressure range as I shoot, and I can get an accurate idea of consumption, by knowing the volume of the cylinder and taking a guess of that of the assembly. With that i can compare then rifles, and say different setups of those rifles.

    For those that are wondering why a digital gauge, well we've found that parallax error when reading them can add a variable, and some even change their reading as you hold them different ways. We're trying to dial out the "i think it's doing this" and get to the "I know it's doing this".

    We've got a really gucci one on the reg tester which is showing some very interesting stuff. More on that soon.

    Anyway, that's me geeked out for today. :D
     

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  6. Chris Coombes

    Chris Coombes The specialist

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    You could of asked for a train set for Christmas instead.

    See you at Bisley
     
  7. C.Eaton

    C.Eaton Confirmed Anschutz Nut...

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    I may be wrong but I seem to remember the Matisse rifle had twin pressure gauges, one for the cylinder pressure, the other showing the reg. pressure in real time. Ben Taylor at his best... :D
     
  8. johnharper

    johnharper Member

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    good to see it worked out for you Rob do like that gauge
    john
     
  9. RobF

    RobF Administrator Staff Member

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    You should see the ones we have for reg testing... ;)

    Setup is paying dividends. A slow leak on the Steyr has been ruled out as being the cylinder, from either the probe, or the connection to the gun or the seal when it's removed from the gun. Now looking at next in the chain.
     
  10. Lol Moore

    Lol Moore Banned

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    Pressure gauges

    Wise to use digital, should be more precise than an mechanical but not necessarily any more accurate than a good one used correctly, as you have found :)

    I have a set of digital pressure calibrators accurate to 2 decimal places (+/- 0.1% at full scale) and calibrated to national standards - not for air gunning as such but as part of my work.

    You would be amazed at how far out some of the Rifle/bottle/checker gauges are when I have checked them.

    Not so bad if you know the error and just want the same thing every time but useless if you want to get a known pressure reading.

    Makes me chuckle when I look at the gauges normally supplied with reg checkers, you would be lucky if you got an accurate one but with such a small face/accuracy (probably quoted as 4% or maybe even 5%) and a needle that is probably 3 Barg wide, confidently saying your reg is set to 85 Barg is a bit of a push.
     

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