Reducing air volume

Discussion in 'Steyr' started by RichWafta, Nov 16, 2018.

  1. RichWafta

    RichWafta Second time around

    Joined:
    Oct 9, 2012
    Messages:
    174
    Location:
    Newport
    Club:
    Quarry, Castleton, Nelson, East Devon
    I have decided to have a play with my Challenge and attempt to get more shots from it.
    I think it is using too much air per shot and this also shows up as being a bit on the loud side!
    My thinking is to reduce the size of the firing valve air chamber. (don't know what else to call it, but someone will know the correct term) I'm not to sure of the volume of the chamber, I guess the way to measure it would be to fill it with water and measure that, but I don't want to do that just yet. To start things off, I have inserted a plug into the 8.5mm drill hole that is at the bottom of the chamber and by measuring the plug, it will give me a 1.5 ml reduction, not a lot, but it does seem to have quietened the shots down a tad, so I'm hopefully on the right track.
    What I'm hoping for, is that one of the Steyr guru's has already done this and can offer some advice. Any thoughts?
     
  2. cloverleaf

    cloverleaf Active Member

    Joined:
    Sep 12, 2014
    Messages:
    302
    Location:
    Oxfordshire
    All you'll achieve in reducing plenum volume is reducing muzzle energy and efficiency.

    What size / colour port is fitted? If it's the small (green?) one you want to source and fit a larger 4mm black one and wind off striker spring preload - this will improve efficiency considerably.

    Also, the guns are noisy because of striker bounce; which as far as I'm aware nobody has figured out how to prevent yet.

    More info here ;)
     
    RobF and subaru swift like this.
  3. DaveRob

    DaveRob Member

    Joined:
    Nov 13, 2017
    Messages:
    67
    Location:
    Durham
    Club:
    York FT Club
    RobF likes this.
  4. fatwelshboy

    fatwelshboy Member

    Joined:
    Aug 18, 2011
    Messages:
    205
    Location:
    Pontypridd
    Club:
    Nelson FTC
    Drilling the green port on my Challenge to 4mm made a massive difference to the power and shot count. I had to wind the hammer adjuster out a fair bit to get the power down and shot count went up to around 145 shots. Still annoyingly loud though.
     
    cloverleaf and RobF like this.
  5. hmangphilly

    hmangphilly Floppy Quick Phil

    Joined:
    Nov 5, 2013
    Messages:
    2,442
    Location:
    wimborne
    heavier hammer and a bit less main spring for the' hammer bounce '.
    It's possibly just a stack of preload slowing down the valve closing

    but

    they work so well as they are , no body has found the investment in time and mucking about worthwhile .........................

    ...........sounds right up my alley ..........:)
     
  6. Conor

    Conor Never been banned from sales Staff Member

    Joined:
    May 4, 2009
    Messages:
    3,264
    Location:
    Ardboe, Co.Tyrone.
    Club:
    Back Hill Ballistics; DFTC; Nelson FTC
    Is that a long cylinder?
    I’m pushing the boat out at just over 110 shots.
     
  7. RobF

    RobF Administrator Staff Member

    Joined:
    Mar 4, 2010
    Messages:
    12,607
    Location:
    New Forest, Hampshire
    Club:
    Parkstone Gun Club, South Dorset FTC, Southampton Buccaneers
    Rich don't do that.

    There's no need.

    To date i've not seen a single thing that is different on the challenge the the LG110. Even the extrusion that's machined for the chassis is the same. As far as I can tell that's all that's different, the chassis is machined in a different design from the side profile.

    So with that in mind, just fit a 4mm transfer port. That will get you a lot of shots back. As Cloverleaf says... this is step no.1

    Altering reg pressure will tune the feel to your desire. Low is blatty and will make the brake work more. High will be short and snappy and the brake will have less to use. Low tends to be less efficient due to valve bounce but that can be got around. But the meat in the pie is the transfer port.

    Forget small plenum chamber, if you want to know why look up Boyles Law.
     
    cloverleaf likes this.
  8. fatwelshboy

    fatwelshboy Member

    Joined:
    Aug 18, 2011
    Messages:
    205
    Location:
    Pontypridd
    Club:
    Nelson FTC
    It's the gun Doz had for second place at the world's, I've sold it back to him since so can't measure the cylinder.
     
  9. RichWafta

    RichWafta Second time around

    Joined:
    Oct 9, 2012
    Messages:
    174
    Location:
    Newport
    Club:
    Quarry, Castleton, Nelson, East Devon
    There, Plenum chamber. I knew it would have a proper name ;)
    Right, firstly there is a 4mm port fitted and the hammer spring preload is backed off quite a bit. The reg pressure is 86 bar. I'm getting about 80 shots from a 195 bar fill, which although enough for a comp, I think should be a lot more.
    My issue with regards to hammer bounce is with the correct valve spring tension, and assuming the hammer isn't over heavy, then it should be minimal. I have tried tensioning up the valve spring, but other than needing more on the hammer spring to compensate, it didn't make a lot of difference to shot count.
    A good few years ago, I had an issue with a daystate CR97, the velocity used to go wild in high temperatures. over a few months of playing, I found that if I reduced the volume of the "plenum chamber", it would run at 770 - 780 but restrict any increase that could embarrass me on the chrono because there wasn't enough air in the chamber to take it over the limit. I did this very much by trial and error, fitting different size tubes into the chamber until I got the right balance. One of the most striking things that came from this was the shot count went up and the gun felt a lot "sharper" to shoot.
    I'm hoping that the same will work for the Steyr. Only problem for me is the Plenum chamber, being oval, will be harder to reduce.
    You may well be right Cloverleaf and the efficiency may go the wrong way, but until I try.............?
    Now I need to look up this Boyles law o_O:confused:
     
  10. hmangphilly

    hmangphilly Floppy Quick Phil

    Joined:
    Nov 5, 2013
    Messages:
    2,442
    Location:
    wimborne
    I like meat pie ........
    steak and ale ,
    steak and kidney ,.........yummy .

    Not chicken though.......

    and fish pie ?? what's that about ? no pastry ? ..........that's not a real pie .............oh. hang on ...sheperd's pie .........I take it back ........


    Meat for your pie .............( not fish though )..........

    IMG_2204.JPG IMG_2205.JPG IMG_2206.JPG IMG_2209.JPG IMG_1905.JPG IMG_1906.JPG IMG_1907.JPG
     
    Last edited: Nov 16, 2018
  11. frank

    frank Reactive Member

    Joined:
    Oct 7, 2014
    Messages:
    252
    Location:
    lincoln
    Club:
    lincs hft
    On my long chassis Lg110 with the long cylinder fitting the black transfer port increased the shot count to 150 shots per 200bar fill, gun running at 11.19
    foot pounds with 8.44 jsb's, almost double the shot count it had with the green port fitted, reg has not been touched, still very loud though
     
  12. RichWafta

    RichWafta Second time around

    Joined:
    Oct 9, 2012
    Messages:
    174
    Location:
    Newport
    Club:
    Quarry, Castleton, Nelson, East Devon
    So what were these ports from Phil? were they all from the same model perhaps?


    I think you may have unwittingly backed up my theory Rob. The rifles are all the same. The chamber is machined for 7, 16 and 30+ joule. What I am hoping to get is a chamber size that is right for 16 joule and no more. It might turn out to be fruitless, but what else is there to do during the winter months?? :rolleyes:
     
  13. hmangphilly

    hmangphilly Floppy Quick Phil

    Joined:
    Nov 5, 2013
    Messages:
    2,442
    Location:
    wimborne
    3 different factory variations
    gold, green and silver you can see the hole sizes . the others are home made 4mm .

    As you say the block reservoir is the same for all out puts , the factory choke the port for lower powers .

    Black 4mm is the way to go for 12 ft lb

    Higher output guns have a heavier hammer . quite a few variations of those . There's a thread somewhere in the steyr dept.
     
  14. RobF

    RobF Administrator Staff Member

    Joined:
    Mar 4, 2010
    Messages:
    12,607
    Location:
    New Forest, Hampshire
    Club:
    Parkstone Gun Club, South Dorset FTC, Southampton Buccaneers
    Yes, higher power (+12 ft-lb) also have an additional part and it's actually difficult to get down to 12 with it.

    Think we're on about 4 hammer variations now.
     
  15. MickyFinn

    MickyFinn I❤HFT

    Joined:
    May 7, 2013
    Messages:
    1,845
    Location:
    Matlock, Derbyshire
    Club:
    The Anston Massive & Kingsley HFT
    I think Steyrs "waste" air as the Steyr barrel/ Ostler stripper combo i have made a hell of a row on a Steyr. Now that it's fitted/machined to fit onto my Anschutz its much MUCH quieter + more shots per fill.
     
    RichWafta and frank like this.
  16. Conor

    Conor Never been banned from sales Staff Member

    Joined:
    May 4, 2009
    Messages:
    3,264
    Location:
    Ardboe, Co.Tyrone.
    Club:
    Back Hill Ballistics; DFTC; Nelson FTC
    And you aren’t wasting air via the transfer port not sealing on the stabilizer bolt. Some ports need a little shim, makes a wonderful difference you know ;)
     
  17. RichWafta

    RichWafta Second time around

    Joined:
    Oct 9, 2012
    Messages:
    174
    Location:
    Newport
    Club:
    Quarry, Castleton, Nelson, East Devon
    So what is different between the Steyr set up and the Anschutz? The reg pressure is probably about the same. Does anyone know the volume of the air chamber in comparison to the Steyr?
    Conor, I haven't got a shim under the port, so that is a possibility, something for me to play with today
     
  18. Ratinator

    Ratinator 77.74

    Joined:
    Jan 2, 2010
    Messages:
    2,765
    Location:
    stourport
    Club:
    Millride FTC / Nomads
    I didn't have any issues with achieving 12 when I used the FAC hammer.
    The old style hammer is my preference due to its rotational capabilities being removed ,second choice would be the FAC hammer due to it offering a little more support to the hammer spring.
    I did make a hybrid that combined the 2 and that also was not a problem ,power wise.
     

    Attached Files:

    hmangphilly likes this.
  19. hmangphilly

    hmangphilly Floppy Quick Phil

    Joined:
    Nov 5, 2013
    Messages:
    2,442
    Location:
    wimborne
    Rich you only need a shim if the tp is blowing ....pull a few strands off a cotton bud , put near the tp and fire a shot to test . Give us a shout if you need one . Or see Chris

    The air Volume is much lower in the Anschutz . IDont have accest to one but I'd GUESS ( very approx ) 3cc ISH is about the most you could achieve with the usual modifications

    Anschutz tuners increase the volume when converting to 12 ft lb .
    The factory Anschutz conversion gives slightly more volume , along with a heavier hammer .

    Anschutz now use a Steyr Looking valve .
    Reg pressure varies from one tuner to another , I 'd be interested to learn what the factory use .
    I've heard of different Anschutz tuners using pressures from less than 70 to up around 100 to use in 12ft lb guns .
    Steyrs are generally accepted to work well around the middle of this range


    I like the extra support and weight of the steyr (fac ) hammer .
    I think the small 16 g hammer requires more spring pre load .

    It's possible utilise the extra air that goes down a steyr barrel to achieve a reduction in shot feel.

    Be aware . reg pressure will affect more than the power out put .

    we have tested the same gun at the same fps but using different reg pressure set ups and found different aim points and feel .
     
    Last edited: Nov 17, 2018
  20. hmangphilly

    hmangphilly Floppy Quick Phil

    Joined:
    Nov 5, 2013
    Messages:
    2,442
    Location:
    wimborne
    You put a steyr barrel on the anshutz Mick ?

    what length ?
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice