How to shim like a true mechanic

Discussion in 'Gun Building, Modifications & Repairs' started by Age, Aug 27, 2011.

  1. Age

    Age Member

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    ***Photobucket is being a pita right now, so some of the pics have text and show where clearance is needed while other pics do not. It seems to change around. I'll try and find out what photo bucket's problem is, but for the time being please bare with me***

    Well most of you all know what shimming is, if not just search, plenty of answers as to what it is.... although, not many answers or guides on how to do it correctly, so here is a guide on how to shim like a true mechanic. A lot of people will tell you to start with the spur gear, that is not correct. There is no mechanical application on the planet earth in which you start shimming in the middle and I can't fathom why anyone would. You always want to start on one side and finish on the end, you don't want to start in the middle then get caught up going back and forth between gears. You always want a nice and clean start to finish in your shim job. Do this correctly and your gun will not only function, it will function like it is suppose to.

    I'm going to try to make this as simple, easy and quick as possible for you guys.

    First, take the pistol grip with the motor and the end cap, then screw it onto the top half of your gearbox shell with only the bevel gear installed. If you have a v3, v6 etc. just screw on the motor and motor cage.

    Adjust the motor hight so the pinion gear makes full contact with the bevel gear just like this (obviously it would be inside the gearbox, but this is just so you get a good view of the what it should look like).

    [​IMG]

    Then, place enough shims of the top face of the bevel gear so that it has enough clearance to avoid grinding against the gearbox shell and meshes well with the pinion gear. The bevel and pinion should be making as much contact as possible without hindering the movement or causing to much pressure.

    [​IMG]

    Now that the bevel gear and pinion gear are aligned and meshing properly, you can remove the motor and pistol grip or motor cage.

    Now place enough shims on the bottom of the bevel gear so it prevents the bevel gear from riding to low.

    [​IMG]

    Screw the gearbox shell together and test the movement of the bevel gear. If shims need to be removed or added, do so to the bottom of the bevel gear, not the top face. If you alter the shims on the top face it will effect the way the pinion gear meshes with the bevel gear.

    Next you install the spur gear. Put enough shims on the bottom of the spur so it has just enough clearance so it doesn't grind against the face of the gearbox shell, the anti reversal latch notches on the bevel gear, and also the bevel gear's bushing or bearing.

    [​IMG]
    [​IMG]

    Then put enough shims on the top of the spur gear to prevent it from riding up. Screw the gearbox shell together and test the movement. Add or remove shims from the top of the spur gear if need be.

    Then install the sector gear with enough shims on the bottom so it has enough clearance from the spur gear and cutoff leaver, and also makes as much contact as possible with the teeth on the piston.

    [​IMG]
    [​IMG]

    This is wrong. The teeth are not fully contacting each other.
    [​IMG]

    This is correct. The teeth are fully contacting each other.
    [​IMG]

    Then put shims on the top of the sector gear to prevent it from riding up. Screw the gearbox shell together and test the movement. Add or remove shims from the top of the sector gear if need be.

    All the gears should have as little play as possible, yet spin freely and without hesitation. I take my time shimming, and I shim gears to the point where they don't move side to side at all, so you may mistake them for being to tight considering you cannot feel them move from side to side, however they spin incredibly well when you move them and you can't even hear them spinning. That's the kind of precision and high tolorances you want, so take your time a get it right.

    All there is to it.
     
    Last edited: Aug 27, 2011
  2. Uller

    Uller Well-Known Member

    2,212
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    Topeka
    I had heard and talked to techs about this,but never seen it done.The next GB I build im going to try this.The Mods need to sticky this after we get some contributors.
     

  3. XxdarkraidxX

    XxdarkraidxX New Member

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    Fort Thomas
    This is an amazing thread to have posted age, thank you for doing so. As uller said, this should be stickied.
     
  4. Adman234

    Adman234 Active Member

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    Wildwood
    I want a sticky too. Very informative pics, and it is obvious that this works very well, because I see that the gears are RIOT's DSGs.

    Awesome writeup. I feel comfortable with my shimming, but not professional.
     
  5. G36airsofter

    G36airsofter New Member

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    lexington
    Love it! This should be stickied. I feel better shimming now
     
  6. germanphoenix13

    germanphoenix13 Member

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    Fullerton
    I agree, this shall be stickies! This is the same method I now use when shimming, that I've been using for about 2 years now. In my earlier days, I shimmed from the sector back.
     
  7. Tackett

    Tackett New Member

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    Charleston
    Niiiiiiiiice...I've shimmed bevel first for a while. But for some reason it never occurred to me to turn....the...gearbox...over...

    LOL.
     
  8. Mikeandwendy74

    Mikeandwendy74 New Member

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    warwick
    Great pictures, good explanation. I agree the spur gear method is absolutely 100% INCORRECT. Bevel to pinion all the way, my homemade minigun with a version 3 gearbox has been fired over 300,000 times and the stock JG gearset has zero wear shooting at 21 rounds per second. I hold the trigger down until the battery dies. The motor gets warm but not hot. The gearbox is super smooth and sounds great. The Bevel to Pinion gear method is the only correct mechanical gear alignment method, and if your tech does not shim your airsoft gearbox this way FIRE HIM.
     
  9. AirsoftimusPrime

    AirsoftimusPrime Active Member

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    Satellite Beach
    Bevel to pinion all the way.

    I've contacted age about this- i changed my shimming method to this around a year ago and it works so well.

    But I can't do It like age. I contacted him about a build- I can't wait for a reply ^.^
     
  10. sp7549

    sp7549 New Member

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    San Diego
    Wow this is a great guide for people starting out in internal work.
     
  11. Njnewland

    Njnewland New Member Lifetime Supporter

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    Cherryville
    This a great guide for people who have been doing internal work, lol.
     
  12. SkateSoft

    SkateSoft New Member

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    Scotch Plains
    I just bought some gears, they only have 2 shims, and I have another two from others. Will this be enough to shim the gun. I don't need it to be perfect, just enough so the guns shoots (not my primary).
     
  13. Njnewland

    Njnewland New Member Lifetime Supporter

    6,559
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    Cherryville
    Your gun won't be very reliable, but yes it will fire. You should definetly buy a shim set in the future if you're gonna upgrade.
     
    Last edited: Sep 17, 2012
  14. Coin3

    Coin3 New Member

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    The amount of shims you need is different for every gun. Assess the play in the gears yourself, to find out how bad or good the tolerances are. Most ACM guns have bad tolerances, so you will either A LOT of shims to get rid of play, or barely any. That's for you to find out.

    But if can, just buy a nice shim set. IT will save you the trouble of trying to get something to work that just wont.
     
  15. SkateSoft

    SkateSoft New Member

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    Scotch Plains
    So it's going to work, its just not going to be reliable?
     
  16. Zarknorg

    Zarknorg New Member

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    Vancouver
    @SkateSoft, well most guns aren't even shimmed properly anyway and they run just fine, so even if you do a little shimming work, it should help out your gun. However, if you do too much (a gear needs lots of shims to correct it) and you don't have enough shims to finish the job you started, then life might suck.
     
  17. Purplestorm3

    Purplestorm3 New Member

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    Harrisburg
    Thanks Age, when i finally get around to shimming this will help alot.
     
  18. Tdabrow

    Tdabrow New Member

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    Exton
    I love you age. I have been trying to find a guide on shimming for a long time.
     
  19. Adman234

    Adman234 Active Member

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    Wildwood
    Hey age, I have adopted this, but I am having trouble deciding exactly how much to make the bevel mesh with the pinion.

    I just put shims on the far side until it seems to make contact really well, but has just a bit of up/down play in the bushing (maybe .1mm up/down play)

    Do you have a better method for checking this? I am good on the rest of the guide, but I just want to know if there is a really nice method for that first step.
     
  20. Adman234

    Adman234 Active Member

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    Wildwood
    Anybody have any input on this? I could use a tip.