Peeque's Tech Thread

Discussion in 'Gun Building, Modifications & Repairs' started by Peeque, Sep 12, 2017.

  1. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    It is a myth that "all" SHS pistons are made well or are really durable.

    These DSG builds are truly pushing these items beyond their performance specs.

    And as you now have first hand experience...to affirm the case that they are suspect from batch to batch...

    I see some gear teeth damage...if you are not PME'ing...then that piston is not moving in the ideal geometry...
     
  2. Peeque

    Peeque Well-Known Member Supporting Member

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    I don't think it's PME. The piston assembly is 20g and I'm using an SP170.

    The gears have side-to-side play in the bushings I'm using. Combined with a bad piston that could be the problem.


    As for a different motor - My first thought was an ASG U-18000 but that's sold out and won't be available until July. A high speed motor would heet up even faster with this setup, wouldn't it? So that's not really an option.

    I've tried my hand at building motors and it didn't work out. I could put a 28tpa armature in a StarWei can but again I'm not seeing Armatures available anywhere.

    I'll have to settle at 55RPS until the U-18000 is available I guess.
     

  3. danerd

    danerd Well-Known Member

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    I have a few G&G 18K arms in a box somewhere, as well as a plethora of other armatures from various makes. If you want them, I can get them to you rather than you wait for the ASG to be restocked.
     
    Peeque likes this.
  4. Peeque

    Peeque Well-Known Member Supporting Member

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    Yeah. I can give them a try.
     
  5. Wingman703

    Wingman703 Moderator Staff Member Moderator

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    Did you... not shim the sector gear?
    And yeah, SHS are great... when you get a good one. Chinese lottery.
    Its hard to tell from the photo, I can't tell for sure PME or not, but I'm leaning towards no PME, bad rack. If that's a Seigetek sector gear with an ACM gearset you probably would have stripped the spur/bevel gear first.
     
  6. Peeque

    Peeque Well-Known Member Supporting Member

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    It's a complete Siegetek gearset. All the gears are shimmed. I meant the axles are able to move left and right inside the bushings. Not up and down.

    The F.L.T bushings came earlier today. I put those in and reshimed. That's no longer an issue now.

    I can get you a better picture of the piston teeth if you want.
     
    -Spitfire- likes this.
  7. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    So, the sector gear was riding high due to worn bushings?
     
  8. Peeque

    Peeque Well-Known Member Supporting Member

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    High towards the piston? Yes, probably. There was a considerable amount of side to side play inside the bushings.

    After replacing the bushings, my tappet plate is now too short to feed in full-auto. I'll start over at 11mm with a new one. I cut it very short but the sector must've been quite far up for it to not work anymore.
     
  9. Peeque

    Peeque Well-Known Member Supporting Member

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    20210507_203003.jpg
     
  10. ma_airsoft

    ma_airsoft Well-Known Member Supporting Member

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    Did the rack split between the last tooth and the rest of the piston and the rest of the rack?
     
  11. Wingman703

    Wingman703 Moderator Staff Member Moderator

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    I think that's just wear. Luck of the Chinese lottery.
    There should not be play inside the bushings though, in any direction. If you can move the axle laterally(i.e, bounce it around in a circle) loud enough to hear it, then the bushings are worn/were poor to start with. Not that I think that caused your piston to die, but sidenote.
     
  12. Peeque

    Peeque Well-Known Member Supporting Member

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    That vetical line a few mm back? I think that's part of a tooth I didn't get completely flat. I can check later today when I'm home.
     
    aotsukisho likes this.
  13. ma_airsoft

    ma_airsoft Well-Known Member Supporting Member

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    Ok yeah that makes much more sense.
     
  14. Peeque

    Peeque Well-Known Member Supporting Member

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    I got a Tienly 25K from Guges a couple days ago. With that, a Guarder SP150, and an 11.1v 5.5A 50C I get 60rps @ 315-330FPS with .28g or ~ 1.3 - 1.4J. Perfect. FPS could be more consistent but I'm not worried about that right now.

    I'm still working out the FPS drop on full-auto. I remembered I can adjust the PWM value with the Titan to lower RPS. With the fin at 8.5mm I get no FPS drop up to 60% PWM or 52RPS. At 70% or 55RPS I start to lose FPS and the gap between semi and auto gets worse as I get closer to 100%.
     
  15. Peeque

    Peeque Well-Known Member Supporting Member

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    20210514_141834.jpg

    Nothin' some JB Weld can't fix. Everything's fine.
     
    Chow likes this.
  16. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    JB weld won't hold a cracked rack very well.
     
  17. Peeque

    Peeque Well-Known Member Supporting Member

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    Probably not.
     
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  18. Peeque

    Peeque Well-Known Member Supporting Member

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    So I'm pretty sure now that I'm getting PME just a little bit. Not enough to fully engage the piston before it returns. Just the tips of the teeth right at the end of the cycle, I think.

    I prepped a new piston and put about a mags worth through it in semi and the piston had no damage. After a short burst in full auto the teeth started to strip in the same way as the last three did.

    I'm gonna put a hold on this build for now until I can find a Siegetek GEN 3 8t DSG. That should give a little more headroom for the piston to return. I could probably Dremel away the first tooth on each set to make it an 8t gear, but I'd rather not risk ruining a $65 gear. I'll save it for a future build that's more semi focused than high ROF.
     
    Last edited: May 26, 2021
  19. Peeque

    Peeque Well-Known Member Supporting Member

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    Alrighty. The Siegetek 8t DSG finally arrived from Evike.

    It turns out I was definitely hitting PME with the 9t. After a few second long burst on full auto with the 8t I disassembled the gearbox and was not greeted by metal debris everywhere for the first time.

    With the SP160 and 8t DSG it averages 1.25J with a 200x6.03mm barrel, and 58RPS. FPS is the same in full-auto finally, too!

    Final parts list:

    Retro Arms V.2 in Red
    Siegetek 10.78:1 8t DSG gearset
    Guarder SP160
    Gate Titan Advanced
    F.L.T 8mm bushings
    Lonex nozzle
    Lonex cylinder head
    Lonex cylinder
    Lonex POM piston head
    SHS 15t piston
    SHS tappet plate
    JG ARL
    Tienly 25K

    Misc info:

    Total piston weight 18.8g
    9 teeth on piston. Too lazy to remove the extra tooth.
    AoE corrected with a 5.9mm spacer printed in Alloy 910.
    Tappet fin 6.6mm.
    Cylinder volume 12860mm^3
    9lb/in tappet spring
    ARL modified for Siegetek 3rd gen Bevel
    Trigger shimmed down so it doesn't mow capacitors off the Titan.
     
    Last edited: Jun 6, 2021
  20. Peeque

    Peeque Well-Known Member Supporting Member

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    Here is a short video of the new DSG build.



    Last week I finally joined the HPA gang after eight years of playing Airsoft. I got a PolarStar F2 for my G36K. It feels so weird to have no "feedback" when I pull the trigger.