Page 4 of 7 FirstFirst ... 23456 ... LastLast
Results 31 to 40 of 61

Thread: Airflow: Is more ever too much?

  1. #31
    Insider imped4now's Avatar
    Join Date
    Feb 2015
    Location
    Indianapolis
    Posts
    278
    This has already become one of the better threads ever on this site. And there are a lot of good ones.
    OlllllllO

  2. #32
    Quote Originally Posted by imped4now View Post
    This has already become one of the better threads ever on this site. And there are a lot of good ones.
    Agreed. This is why I tell people to come here.

    Thanks again, all. Will chew all of this over and bring more questions.

    In meantime, I'll also post back with some spring and valve specs for my setup, to see what can be gleaned from them.

    Thanks again!

  3. #33
    Insider
    Join Date
    Apr 2012
    Location
    Knoxville, TN
    Posts
    2,303
    One point on the above - the force to return the assembly decays as a function of the valve chamber size.

    So, the more volume you have, the higher return forces you have to snap the valve shut, and you avoid "long tails".
    Exactly. Good way of describing it and definitely a factor.

    That Racegun timing point is insane - that can't have been terribly consistent, to have the backblock pluck the hammer off the active valve. Cockers are such a glorious mess.
    It was consistent, but for the wrong reasons - It basically was a dump chamber. So most of the work was done, ball down the barrel, before you dropped pressure enough to dump the LPR. The rest was just waste, not used. Pressure was sealed till 8" or so of ball travel. If you didn't have a ball they often would 'Bolt Stick' due to lack of back pressure, then run fine when the ball was in there to leave some air in the system. Like the Impulse did. Same problem really. So, consistent - but horribly wasteful.
    Last edited by pbjosh; 11-20-2018 at 01:35 PM.
    Josh Coray
    J4 Paintball
    Lead Design
    www.j4paintball.com

  4. #34
    Back again.

    Josh, to answer some of your thoughts/points, questions:

    Yes, the marker hisses momentarily on gassing, or else fires a half shot if the EZ ASA is slammed home. Then it stays quiet.

    Here is the valve spring - Gardner 36362GS stainless precision compression
    OD- .30
    Wire diameter - .026
    Free length 1.25"
    Rate (lbs/inch) - 3.74

    Hammer spring I don't have on the table as it's still in the marker, but it's a bit softer than Simon's hammer spring.

    Valve is small. .250 inlet and outlet, sealing face is slightly larger, and cup seal is a soft o-ring.

    Cup seal stem is necked down to .126

    Timing is very, very conservative. Fires almost immediately in the pull, and recock is at the very end. In fact, it's so conservative that, even with the ID frame, you can isolate the firing and recock phases with a single finger.


    Threw a cheap gauge on it and showed just high of 300 psi.

    I should also point out that, when fired side by side with my Resurrection, using identical barrels, paint, etc., the mini fighter doesn't even sound like the same kind of marker. The Ressie has a sharp pak-pak, and is loud, while the mini has a soft thup-thup, and is substantially more quiet.

    As I said, I wanted this to be very soft-shooting, and didn't expect efficiency to be even as good as the Ressie. And based on everything I've seen, heard, and read (especially including here), it definitely sounds like it's doing all the wrong things on paper, yet it's still getting a case per fill.

    So, does this mean this thing is (theoretically) capable of even more?

    I like it just as it is, but if I can push the performance even further in this next build, that would be hilarious.
    Last edited by Menace; 11-20-2018 at 11:17 PM.

  5. #35
    Insider
    Join Date
    May 2012
    Posts
    1,114
    Supports Inception Designs
    I don't think you're doing the wrong things on paper - 300 psi is quite high.

    A smaller valve head diameter affects everything: closing force goes down as the radius squared, but valve flow for a low lift poppet valve is generally governed by curtain area (Perimeter), which scales linearly.

    You get back the flow by having to run a higher pressure in the chamber.

    My guess is that with the extra volume you've got, a high initial pressure, and a relatively small valve orifice, you're not losing much valve closing force and the chamber is over 100psi at the nadir.

    The lower valve rate also explains why you've got a quieter marker despite the higher pressure.

  6. #36
    Insider imped4now's Avatar
    Join Date
    Feb 2015
    Location
    Indianapolis
    Posts
    278
    I did a little checking last night....with my IVG flush with the body, my hammer was resting against the valve stem and holding it full open, or close to it. The valve spring (ID V2 11/16" valve with included spring) feels similar to a medium Madman spring from years ago. I don't have any other data on it other than that. Perhaps Simon can drop in....

    I clipped the hammer spring to set it such that with the IVG flush with the body, the hammer was just resting against the valve stem but not opening it. We'll see what effect that has on velocity when I chrono it this afternoon.
    OlllllllO

  7. #37
    Insider imped4now's Avatar
    Join Date
    Feb 2015
    Location
    Indianapolis
    Posts
    278
    In response to the post above, it had a massive effect on velocity, which went from 280ish to 190ish after trimming the spring. To get ti back up, I had to crank the IVG in a good 3+ turns from flush, so nothing here was really gained it seems.
    OlllllllO

  8. #38
    Interesting.

    Will be looking forward to learning what the increased input pressure does for your efficiency.

  9. #39
    Insider imped4now's Avatar
    Join Date
    Feb 2015
    Location
    Indianapolis
    Posts
    278
    I do suppose I could test out a lighter valve spring, but am not sure if I will see any net gains vs the two springs I had (untampered hammer spring).
    OlllllllO

  10. #40
    Insider
    Join Date
    Apr 2012
    Location
    Knoxville, TN
    Posts
    2,303
    And based on everything I've seen, heard, and read (especially including here), it definitely sounds like it's doing all the wrong things on paper, yet it's still getting a case per fill.

    So, does this mean this thing is (theoretically) capable of even more?

    I like it just as it is, but if I can push the performance even further in this next build, that would be hilarious.
    If you are getting a case per fill, you are already there.

    I would say the interesting factor is the small port - that does restrict flow, and would lead to the higher Sweetspot - a larger valve opening would work like the heavier spring, the lowering the sweetspot location.

    What bolt are you using?

    There are so many little factors, and the reason I say SWAG (Scientific Wild Assed Guess) - fixed cocking issues with a valve spring, LPR, or even a bolt change. I remember we couldn't get the velocity up on a cocker once, much above 210 or so. Turned out the Titanium cocking rock was too light. It ended up a stock rod upped the velocity quite a bit. ALMOST had a bunch of bronze cocking rods built with a couple different weight sized. Would just need to drop in a heavier one to get more velocity. Quick and easy vs changing a hammer. Small changes can have weird affects.

    So, when you do this:

    I clipped the hammer spring to set it such that with the IVG flush with the body, the hammer was just resting against the valve stem but not opening it. We'll see what effect that has on velocity when I chrono it this afternoon.

    In response to the post above, it had a massive effect on velocity, which went from 280ish to 190ish after trimming the spring. To get ti back up, I had to crank the IVG in a good 3+ turns from flush, so nothing here was really gained it seems.
    If you were getting 280 on a spring, cutting it short won't add velocity. Ha! You still have to put a certain amount of energy INTO the valve stem to get an effect - the hammer and spring balance you had before stores a certain amount of potential energy. To replicate your situation for 280 fps you would need a heavier spring that traveled a shorter distance to store the same energy, as in, the IVG is all the way back. Then the spring would have come to full extension before contact with the stem, allowing for a faster closing setup. Though with a heavier hammer, to some balanced extend, you could have more hanging energy in it's mass - making the valve dwell a bit higher. The AKA valve only needed to open 1/16th of an inch to get full velocity.

    Most of this really is in tuning mechanically a few ms of action in a mechanical manner. With valves, bolts, available chamber volume, hammer, spring choices, barrel, IVG and pressure all being factors in the action - some times it just is dumb luck either way.

    I don't think you're doing the wrong things on paper - 300 psi is quite high.

    A smaller valve head diameter affects everything: closing force goes down as the radius squared, but valve flow for a low lift poppet valve is generally governed by curtain area (Perimeter), which scales linearly.

    You get back the flow by having to run a higher pressure in the chamber.

    My guess is that with the extra volume you've got, a high initial pressure, and a relatively small valve orifice, you're not losing much valve closing force and the chamber is over 100psi at the nadir.

    The lower valve rate also explains why you've got a quieter marker despite the higher pressure.
    Nothing I disagree with there. Could you explain the bolded part a bit more? I intuitively know it, but I haven't come across the 'engineering' on it much.
    Last edited by pbjosh; 11-26-2018 at 02:58 PM.
    Josh Coray
    J4 Paintball
    Lead Design
    www.j4paintball.com

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •