shimming bevel issue

Discussion in 'Gun Building, Modifications & Repairs' started by Big Chungus, Jun 9, 2021.

  1. Big Chungus

    Big Chungus New Member

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    Mount Sinai
    Need some help. The gearbox is a king arms qc out of a 9mm pdw. The bearings are flat with the shell. The shell is not warped. I've tried 3 different 16:1 gearsets, and 3 brands of shims, and I can not get it quiet once the bevel gear is in the shell. No matter how high or low I shim the bevel just to clear the spur and spin, once I close the shell and rotate the gears with my finger, they spin many rotations but I hear a slight banging like something is catching. I've checked all clearances and everything checks out. The spur and sector are shimmed perfect and spin many times together, but once the bevel is placed in the gearbox, it turns to ****. I'm considering running the stock bevel as that has not gave me and issue. I have shimmed a dozen aegs without running into this issue. Yes I use bevel to pinion method. Any help is appreciated!
     
  2. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    We'll things are not made to any "standard" in Airsoft any more. So, your set may just be of very low quality, which can be the case since the Airsoft industry is an inverted pyramid when it comes to supply chain.

    Post a video demonstrating the noise issue you are having. It would be a lot better than just trying to describe it with words.
     

  3. Big Chungus

    Big Chungus New Member

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    Mount Sinai
    it will not let me post a video here, but it will on reddit. Not sure why
     
  4. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    You post the link for the video.

    There is a size limitation for images or videos.
     
  5. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    That..."rrrrururururrur"...noise is "normal".

    Gears are seldom "silent"...especially if the gear set is "Made in China"

    Gear sets that are all smooth and "nearly" silent cost about $130.00+ a set at retail.
     
  6. Big Chungus

    Big Chungus New Member

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    Mount Sinai
    yes the rurrr noise i know but the slight bangingor clicking as they are rotating. I dont remember hearing that in the past few boxes ive shimmed. I assume it all sounded fine?
     
  7. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    The...."...jug-chuk..." mixed in the rurururur? That sounds like side to side play. Is this box buttoned down?
     
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  8. Big Chungus

    Big Chungus New Member

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    yes all screws are tightened
     
  9. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Shimming maybe a hair loose...but the noise is not anything "unusual".

    If you just flip flop the mechbox from side to side are you hearing a noise? Specifically, that "...jug-chuk..." as the gear slaps the sides?
     
  10. Big Chungus

    Big Chungus New Member

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    Yes I hear it when I flip it on each side when I spin it really fast. No more than 1mm movement in the axles. It seemed to make less of that jug chuk noise with the stock bevel. Im building a dsg so I want to take my time with this.
     
  11. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    1mm...that is big gap.

    I try to maintain a .1mm after it's snapped up.
     
  12. Big Chungus

    Big Chungus New Member

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    lol thats what i meant
     
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  13. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Are the bushings/bearings in snug?
     
  14. Big Chungus

    Big Chungus New Member

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    yes and completely flat. I'm just gonna go for it. I'm sure its fine. When everything is all assembled, the clearances between the gears is perfect and it rotates fine. Just the clatter here and there. Is it possible that the shims are not wide enough so maybe the gears are rattling?
     
  15. Ben3721

    Ben3721 Well-Known Member

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    I would try spinning just the bevel alone to see if its hitting anything weird or if the bearings are blown. Then I would test the slack of the teeth by holding the sector still and moving the bevel to see how much wobble it has when you try to rotate it.

    Its also important to know gears under no load can bounce on the rotational axis since nothing is keeping them tight. This can prevent free spinning of gears, lube can add some resistance/sticky and stop this phenomenon from happening.

    Another issue is 12:1 gears and 16:1 gears use an oddly shaped spur lower that tends to leave more slack with your standard 10 tooth bevel.
    There is some history to the reason of why this flaw exists, something about the use of wider fat 9 tooth bevels years ago that got discontinued due to being proprietary or something. But that may not be accurate with all brands. If someone knows more about that it would be nice to hear.
     
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  16. wetpee

    wetpee Active Member

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    Have you tried spinning the gears the other direction? My brain tells me it shouldn't matter as airsoft gear teeth all appear to be symmetrical, but strangely, I've had experience with fresh, unused gears being quieter spinning the intended direction for operation. Either way, sounds like average luck with chinese lottery or perhaps SHS gears in particular. Something is definitely hanging up somewhere and it seems you've already deduced it has to do with the interaction between bevel and spur. I'm sure with enough observation you could further narrow down where the imperfection lies. However, listen to Ben before me. If he says the zero-load factor is important, it's probably worth noting, although if the stock bevel does not make this noise, then I would say it stands to reason that there is an inefficiency somewhere when using the bevel that does.

    Which brands of gears have you tried? Do all bevels except for the stock bevel produce the same noise no matter the spur gear used? Have you checked the meshing of the teeth between various combos of gears?
     
    Last edited: Jun 11, 2021