Bevel Gear Stripping Help

Discussion in 'Electric Guns' started by mvsrocks, Sep 14, 2012.

  1. mvsrocks

    mvsrocks New Member

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    For some reason, I keep stripping my bevel gear where it meshes with the spur gear. I've gone through three bevel gears where this has happened... an SHS Gen 1, and two SHS gears with gear sheets. I'm pretty sure that the shimming is decent. Here is the video of my shimming. It shoots about 36 rounds per second.

    [ame]http://www.youtube.com/watch?v=uvYYPOhOf5w&feature=plcp[/ame]

    I am using SHS 16:1 gears with 2 shortstroked, M125 spring, and the gears have stripped with both a 11.1v LiPo and 10.8v NiMh. Am I doing something wrong? I saw that one person had this problem before, but he was not specific on the issue in his thread:

    http://www.airsoftforum.com/board/lofiversion/index.php/t98237.html
     
    Last edited: Sep 14, 2012
  2. tscebu

    tscebu New Member

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    Dayton
    The m125 might be too powerful for the high speed gears to pull back that quickly. Your motor could also not be adjusted to the proper height.
     
    Last edited: Sep 14, 2012

  3. mvsrocks

    mvsrocks New Member

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    The shimming is near dead on. An M125 is nothing to pull back for SHS 16:1 gears, especially because I short stroked two teeth. A ROF like that with an M140 or so would be very stressful to the gears. Motor height doesn't even effect the area of the bevel gear that meshes with the spur gear.
     
    Last edited: Sep 14, 2012
  4. tscebu

    tscebu New Member

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    Dayton
    What double post? Also, I'm just trying to help, so no need to freak out.

    Back to the point. Gears that are not shimmed properly might not show effects on semi, but might cause gear stripping on full auto, especially high ROF full auto.
     
  5. mvsrocks

    mvsrocks New Member

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    What? As I said, the shimming is dead on.
     
    Last edited: Sep 14, 2012
  6. tscebu

    tscebu New Member

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    Dayton
    Just to make sure, you don't use a mosfet with active braking, do you?
     
  7. mvsrocks

    mvsrocks New Member

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    No I don't use a mosfet with active breaking. Also, that won't effect breaking the bevel gear the way I did... It only will effect the motor temperature, the electrical components, and the semi shot.
     
  8. tscebu

    tscebu New Member

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    Dayton
    If you are sure that your internals can candle an M125, then it could just be that your motor is moving to fast for you bevel gear to handle. What type of motor do you use?
     
  9. mvsrocks

    mvsrocks New Member

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    The motor brand/model should not effect the bevel gear as long as it is shimmed correctly. What matters is how much power it outputs, and as said before, it rotates the bevel gear about 600 times per second, which is about equivalent to 36 rounds per second. No more redundant questions please.
     
  10. alex

    alex New Member

    4,794
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    Atlanta
    with an m125 and 16:1, you will need both a hardened bevel and pinion gear when using 11.1v. ever tried slamming a manual transmission on 2nd gear at a light (using very high revs). that's what's happening in your gearbox.

    or stick with stock JG 18:1 gears using bearings 16awg shs or lonex torque motor, deans, mosfet and it will last longer (~30rps). short stroke only affect the release stage, it will still stress the pickup stage (starting amp load).
     
  11. Star_folder

    Star_folder New Member

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    Lexington
    Use a different bevel gear. SHS bevels are know to be weak. If you've got a JG bevel laying around, it will work. Personally, I've never had the issue you're having, possibly, you're just really unlucky. I've had several builds with SHS 13:1s and M140s or M150s that are running just fine.
     
  12. alex

    alex New Member

    4,794
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    Atlanta
    forgot to mention, did you shim bevel to pinion? ignoring this can cause bevel/pinion failure.
     
  13. mvsrocks

    mvsrocks New Member

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    So there is no way to use a 410 fps M125 spring (worn down and used a lot, plus matrix)? With the short stroking, it shoots about 350 fps with 0.2g bbs.

    Also, all I need to do is get a better bevel gear? I thought the SHS gen 1 was supposed to be quite strong.
     
  14. alex

    alex New Member

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    Atlanta
    you can use it with 11.1v, but you need to shim the bevel to pinion correctly. 16:1 adds more stress than 18:1. if the bevel to pinion is too loose, it will fail early.

    reducing the load as much as possible is key. make sure your piston is lightened. piston to guide rail smooth and not binding. tappet plate not rubbing against sector gear. also note that matrix pinion gears are fatter than other pinion gears. if it's too tight, it will also fail really quick.

    bevel to pinion shimming is the main cause of bevel to pinion failure.

    did i mention that you need to shim bevel to pinion?
    if you want to avoid properly shimming bevel to pinion, you can get chromoly gears and pinion.
     
    Last edited: Sep 14, 2012
  15. mvsrocks

    mvsrocks New Member

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    The shimming for the bevel to the pinion is almost perfect. It's very quiet, doesn't grind, the pinion gear is at the perfect height, fully engaging the bevel gear teeth but not too high, and the gears spin freely. I am pretty sure I got that part correct. The bevel gears all look new except for the bevel teeth that mesh with the spur.

    The bevel teeth that mesh with the spur gear are the only problems.
     
    Last edited: Sep 14, 2012
  16. alex

    alex New Member

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    Atlanta
    what method did you use to shim bevel to pinion?
     
  17. mvsrocks

    mvsrocks New Member

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    I've read almost every method of shimming the pinion to the bevel, and use a mix of them with some of my own techniques too. Here are some I used.

    http://www.airsoft-barracks.com/forums/topic/24099-shimming-the-bevel-gear-with-pictures/

    http://www.airsoftsociety.com/forums/f10/how-shim-like-true-mechanic-30461/

    Here is literally my process:

    1.) Take out all the gears and air seal parts except the bevel. Start off with a round estimate (half and half on top and bottom of bevel)

    2.) Only put the grip on the right side of the gearbox with the bevel in place. Add the motor to it. I observe the motor height with the space between the tip of the pinion to the ARL teeth on the bevel.

    3.) I see how much the bevel can move up and down towards and away from the bevel gear. Once I find an ideal amount of space with shims, I assemble the other side of the gearbox and test the sound with only the motor and bevel gear.

    4.) If the sound is horrid, I take off less shims from the top of the bevel and recheck the motor height.

    5.) If the sound is decently quiet, I put in all the other gears and see how loose the bevel is to the pinion.

    6.) If all is well, I assemble only the gearbox, motor, and motor grip and test it, like in the video.
     
  18. alex

    alex New Member

    4,794
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    Atlanta
    you left out a step. did you mark the lower receiver on the gearbox and line up the pistol grip to make sure there isn't a gap between the gearbox and pistol grip? this is a common problem with the half shell method. if there is a gap, the motor height will drop and will get partial contact between the bevel and pinion. if there is a gap, you can sand down the pistol grip where it makes contact with the lower receiver.
     
  19. mvsrocks

    mvsrocks New Member

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    So I mark the gearbox somehow to make sure that the piston grip is in the correct position while putting it in the lower receiver? Also, does that affect the bevel gear teeth that mesh with the spur gear to break? (the part that is near the bottom shaft, not the umbrella teeth)
     
  20. Star_folder

    Star_folder New Member

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    Lexington
    Have you checked the spur gear, to make sure it doesn't have any issues with it's teeth? I've seen a few that have small burs on them that could cause this kind of damage.