Overspin??

Discussion in 'Gun Building, Modifications & Repairs' started by John Daley, Oct 25, 2020.

  1. John Daley

    John Daley New Member

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    Gardner
    Completely new build that half-cycles every other full trigger pull in semi, full auto works fine. I’ve read countless other threads with similar symptoms, but I’m wondering if a Gate Titan or other higher-end MOSFET with active breaking is my only solution.
    This issue only occurs in an 11.1 LiPo, it fires as expected with a 7.4, but the ROF is poor.
    Build list:
    CA V2 9mm Shell, polished and radius’d
    SHS 13:1 Gears
    FLT bushings on step and sector
    Stainless bearings on bevel
    Shimmed and AOE corrected
    SHS Full steel 15 tooth piston
    ZCI stainless full cylinder
    Lonex Cylinder head
    Lonex tapper plate
    Lonex nozzle
    Retro arms steel cut-off lever
    Retro arms CNC trigger
    Lonex trigger contacts
    (first attempt used original CA wiring harness and contacts, had same issue)
    Guarded SP 140 Spring (have tried SP110, 120, and 130)
    ZCI 22tpa motor

    I really took my time with this build and tried to make it as durable as possible. I guess I’m looking for ideas to actually correct the issue versus “fixing” it with active breaking. Any input would be much appreciated.
     
  2. Ben3721

    Ben3721 Active Member

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    You shouldn't have this issue with that gear ratio, motor and spring...

    I had some issues with the retro arms trigger tolerances awhile back, I wonder if that has anything to do with your particular build. I'm taking about the height of the trigger, too high and the cutoff lever can't kick the trolley off causing full auto in semi, too low and the trolley slips before the trigger is fully pulled causing half shots. Different trigger trolleys with different triggers can change this interaction broadly. Making unpredictable behavior unless you know what to look for. Try putting the gearbox together without the compression parts/motor, hold the trigger in semi and rotate the sector back until it kicks the trolley while looking down the cylinder windows. You could be able to locate what is going on from doing so.

    This is fixable without spending 150 bucks for an electric trigger board.

    Good luck!
     

  3. John Daley

    John Daley New Member

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    Gardner
    Thank you...I did give the trigger some thought but the thing that confounds me is the problem disappearing with the weaker battery. I do know the CA triggers have less material where it meets the trolley than most other triggers which caused the trigger to not reset properly in a different build and shell but had not experienced any of those issues with the speed trigger and Lonex contacts in this shell but I guess it’s time to try the CA trigger and see if anything improves. I really appreciate you taking the time to share your thoughts.
     
  4. John Daley

    John Daley New Member

    18
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    Gardner
    Edit: I meant that non-CA triggers were not resetting using a stock CA harness and contacts. Sorry for the error.
     
  5. Ben3721

    Ben3721 Active Member

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    Well it working with a weaker battery has me more puzzled.

    Unless the overspin lands it right back to almost cutting off again. Where is it landing in the cycle with the overspin in semi with the stronger battery? If the piston is basically all the way back that could be a possibility, but the cutoff lever should only engage once the piston is let go, but it could basically have the cutoff lever halfway up, making the phenomenon happen where it wants to shoot every other shot... yeah a video would definitely help. Even hearing the sound could make it easier to identify.
     
  6. Lefse

    Lefse Well-Known Member Supporting Member

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    I'd try shortening the spring on the trigger switch, it can often fix overspin issues in my experience. No need for a super expensive computer mosfet.
     
  7. Guges Mk3

    Guges Mk3 Well-Known Member Supporting Member Lifetime Supporter

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    Actually the weaker battery is a clue. It means the power is at a level that is not useable to keep the motor running...thus it cuts a fraction of a second quicker.
     
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  8. John Daley

    John Daley New Member

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    Gardner
    Update: Well, FML. I was making a video of it so I could post it and, well, I guess my radius job didn’t turn out so well. I guess I will just appreciate what I learned during this build and look for a new shell. Thank you to those who shared their ideas and knowledge.
     

    Attached Files:

  9. Guges Mk3

    Guges Mk3 Well-Known Member Supporting Member Lifetime Supporter

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    You didn't have a curve in the right spot.

    Comeplete G&P Mechbox is 45.00 shipped from me....
     
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  10. Ben3721

    Ben3721 Active Member

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    Thats a bummer. The guarder sp140 is a powerful spring, when you corrected AOE did you just space the piston head out with washers or with a shock absorbing pad? Even so I'm surprised you cracked it with the radius job. I've been running a sp130 spring on a very similar build short stroked by 3 for about 5 years every other, roughly 1-2k shots each time, however i have a 1/4" shock absorbing pad and I have my metal hop up unit pressing against the front of the shell with quite a bit of pressure and have lucked out so far.
     
  11. John Daley

    John Daley New Member

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    Gardner
    I guess I didn’t radius correctly, I had used a neoprene washer from the hardware store to help correct AOE. Perhaps a softer material with more dampening potential should have been used in addition to a better job rounding out the steps in the corners. Sucks but I learned a lot getting to this point and I know what I’m trying to build isn’t unreasonable I just need to execute better.
     
  12. John Daley

    John Daley New Member

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    Gardner
    I appreciate the offer but I won’t learn anything by buying a complete gearbox.
     
  13. Guges Mk3

    Guges Mk3 Well-Known Member Supporting Member Lifetime Supporter

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    Not true. You are making some generalized assumptions that all things are equal in Airsoft...its far from it.

    You will see how durable a well made and put together G&P box from the factory runs in stock form...but since you are driving it above spec...your mileage will vary.

    And your mechbox is a CA unit? I can see a "ic Army". That mechbox alloy is rather brittle...compared to a G&P unit.
     
    Last edited: Oct 30, 2020
  14. OPairoft

    OPairoft Active Member

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    Bend
    Was the piston head metal? If it was that definitely caused more stress on the shell with a metal cylinder head.
     
  15. John Daley

    John Daley New Member

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    Gardner
    Yes, SHS blue with the thrust bearing metal head bc the first piston I tried broke. I thought the neoprene washer, though pretty rigid, was enough to dampen the impact of a 30 gram piston even with the stiff spring. The results prove otherwise, and I’ve checked the radius job I did vs. the guide here and a couple YouTube clips and can’t figure out what I did wrong in that procedure.
     
  16. Ben3721

    Ben3721 Active Member

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    I would go with a plastic piston head with a proper buffer glued on the cylinder head. Sorbo pad or some other soft material. There used to be a detailed thread on ASM about radiusing. Including digital diagrams showing the beneficial effect of it. When you radius you want to not only make a round cutout, but also prevent a thin edge anywhere on the curve, thats where a crack would try to start. I wouldn't let it bother you, just find a new shell and take a bit more precaution, it likely will not happen again.
     
  17. John Daley

    John Daley New Member

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    Gardner
    Thanks, I’m going to keep at it until I get it right. I’ve really enjoyed the process and even the frustrating results of my inexperience, although the shell cracking is kind’ve a kick in the nuts bc I have a pristine CA body but have had fitment issues with some non-CA shells so I bought the one I ruined and gutted it. I’m trying to confirm whether the RA cnc shells fit and if so may go that route.
    Thanks again for the help, I really appreciate it.
     
  18. Guges Mk3

    Guges Mk3 Well-Known Member Supporting Member Lifetime Supporter

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    That is an overly optimistic statement. His CA mechbox cracked, 60% of the mechboxes on the market are worse than the CA unit...so, it will most likely happen again unless you get a better alloy mechbox.

    BTW...6mm tapered rat tail files make nice little round holes...unlike what you used.
     
    Last edited: Oct 30, 2020
    CacheFlow likes this.
  19. John Daley

    John Daley New Member

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    Gardner
    Thanks, I’ll definitely grab a new file. Didn’t you say CA shells are brittle? Or do you mean just compared to the G&P you sell?
     
  20. Ben3721

    Ben3721 Active Member

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    A little optimism never hurts :D
    Proper precautions lead to a higher chance of success. There are many ways to prevent this type of failure these days. One could even get a shock transfer block for under 20 bucks after adding a sorbo buffer and radius and that would basically make the chances of failure very low.