Featured Having some overspin issues.

Discussion in 'Gun Building, Modifications & Repairs' started by kylendm, Nov 22, 2021 at 6:00 PM.

  1. kylendm

    kylendm Member

    81
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    Atlantic City
    So I have a sig 551 that has been having overspin problems for a while.

    It happens on 11.1 and 7.4. Installed is a Gate Titan, an older systema medium type motor, 13:1 gears, and I believe a M120 spring.

    I understand the titan should be able to help this with active braking but no setting solves it. Even at 100%.

    Also it doesnt double shot on every trigger pull. On 11.1 its double every 3-4th pull and 7.4 its every tenth or so. Any suggestions?
     
  2. Ben3721

    Ben3721 Well-Known Member

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    This sounds like a mosfet issue with cutoff somehow.

    Overspin with that setup on a 2 cell lipo would be very little on a m120 with those gears and motor.
     
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  3. Squad144

    Squad144 Active Member

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    Ocean Springs
    I know this sounds completely crazy, but I was having a similar problem for a while and, again I know it sounds crazy, but is your bevel gear lining up perfectly with your pinion gear? You can tell if, even after a perfect shim job, your gears still sound noisy.

    I will explain why I am asking this question later as I have a theory on why this happens with poorly made gearboxes that suffer from improper bevel placement.
     
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  4. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

    8,357
    4,726
    Minneapolis
    Not to many makers of the SIG 551, I can only think of TM and ICS.
     
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  5. OutlawAirsoft

    OutlawAirsoft Active Member

    287
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    Hamilton
    Maybe try replacing the motor. I know active braking puts a lot of stress on the brushes.
     
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  6. Ben3721

    Ben3721 Well-Known Member

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    Sometimes if a motor is jacked up it will stop at a different spot every cycle. But I've only seen it happen on really snappy setups that already have a lot of overspin.
     
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  7. kylendm

    kylendm Member

    81
    1
    Atlantic City
    Ok so I opened up the gearbox, probably should have did that first, and found a bunch of broken pieces of metal in there. I think the spur gear ripped up a shim on the bevel gear. Anyway, I also noticed a bunch of grease on the sensors so i cleaned it up.

    I tried it again after reshimming and all seems to be pretty good until i turned precocking on and then off again. Now its got some overspin again. I did notice that the spring lost a lot of power though. It was a m120 but now its only shooting about 1 joule. I know a weak spring can cause overspin so I'll order a new spring and I'll post again.

    Also yes, this is an ICS 551. Very cool gun but it has a few archaic things like the medium motor and proprietary hop up unit.

    Thanks for the suggestions everyone. I might also swap out the motor since it is quiet old. I think Tienly makes nice medium motors still.
     
  8. Squad144

    Squad144 Active Member

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    Ocean Springs
    Try a PDI spring. Very consistent.
     
  9. kylendm

    kylendm Member

    81
    1
    Atlantic City
    How are the asg ones? I like that they are color coded
     
  10. Ben3721

    Ben3721 Well-Known Member

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    The coloring is nice but some still ends up flaking around the shell.

    Springs are good tho.
     
  11. Squad144

    Squad144 Active Member

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    Ocean Springs
    I have heard the opposite. Color coating is nice but it will flake off as Ben mentioned above. Not to mention, look at how long that spring is. From what I hear, they are that long because of the cheap material they are made of. I am sure they are better than a stock spring, but if you want something that will last, invest in a quality spring. PDI 170% will get you around 380-390 fps and the PDI 190% will get you around 410-420. These are chrono reading with with .2 and good compression.
     
  12. Ben3721

    Ben3721 Well-Known Member

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    I've always stuck to guarder springs for my personal builds. Never shattered one yet.

    Make sure the piston moves freely and the tappet/nozzle actually seals too if it still acts up.