Retro Arms bushing/bearing holes are badly off?

Discussion in 'Gun Building, Modifications & Repairs' started by Ben3721, Sep 1, 2021.

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  1. Ben3721

    Ben3721 Well-Known Member

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    So awhile back I rebuilt my main m4 after the src gearbox shell rails that support the piston wore a bit thin from years of use. So I bought a retro arms split shell.

    It appears the bushing holes for the bevel are off spec from the motor entry angle. Causing very poor pinion to bevel meshing, and costly damage. Been trying to figure out why I have blew my motor bearings (first time that's ever happened) and blew out a couple pinions. Tried testing with a 3d printed motor angle checker but the gearbox clamps down on it so hard that it straightens out while bending the part that goes in the bushing holes resulting on a false positive angle check, yay... I checked some photos of their other v2 shells and apparently this is a problem with all their shells. My guess is the bushing hole is off by about .3mm forward orr they could have the bottom of the gearbox off causing the bushing hole to be too far forward. Who knows, they would have to check the schematic to what actually comes out of the cnc machine. All the bushing holes could be forward together for all I know.

    Basically when I shim I leave about .1mm to .2mm room between the pinion and bevel for meshing, even with that room the bevel is tightly jammed and doesn't wiggle at all, which it should a hair. Even if I let the motor height way down it still stays too tight,, since the pinion is trying to mesh at a bad angle. It's 100% not the grip.
    A pinion tooth is about 1.20mm wide, so being off by .3mm is enough to cause some some wear or failure. I typically don't complain about issues like this, but this shell was not cheap and when I buy a cnced part I expect it to be usable, not blow out my motor tower bearings and two pinions in less than 6k rounds. Hopefully this issue doesn't go ignored, I contacted them about the issue, but they have ignored me in the past. This issue also will cause absurdly high amp readings. I'll probably switch to a lonex shell. I used to have a src shell and ran about 140k rounds on the same pinion without all this weird drama.

    I bought the shell off brillarmory.com but this clearly isn't his fault. This issue really has torn up my seigetek bevel which isn't cheap to replace. I could try to return it to him but that would likely hurt his pocket in the end. My bevel looks worse than it does in this photo now, that's another 50 bucks down the drain, the gearset isn't from brill.

    I would assume some would think I'm ocd, but when parts that never blew out start blowing out...

    I use a small hole in the shell to adjust motor height and shim the bevel up to the pinion then back off. I had the motor tightly clamped into the shell to set the bevel height with the motor 100% in line with the shell, a method that has worked for over a dozen high speed builds I've done over the years with no issue at all. I also make sure my motor tower is snug in the gearbox, no slack or any room for error.

    So thoughts? Am I going crazy or is this really what's going on? I can't even run 3k rounds without damage.
    The bushings are retro arms 8mm installed with their tool with support on the backside of the bushing holes to prevent warping.

    Oh and if anyone has a couple shells that work with g&p receivers for sale pm me. Lonex shells are sold out basically everywhere.

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  2. ma_airsoft

    ma_airsoft Well-Known Member Supporting Member

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    Personally not a fan of RA shells. Wouldnt surprise me if its off as I’ve got one on my desk right now thats being weird.

    The only other thing it might be is the motor grip but it seems like you’ve checked that already plus im guessing you used it no problem with the other shell.

    If interested I have a g&p stock gearbox ill let go. shoot me a pm if you want it
     

  3. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    It's hard being OCD in a world where nothing is made to a "standard".

    You guys would have liked Airsoft parts 16 years ago...today...I don't do "upgrades" any more, especially if the player dumps the parts on me and want me to put it in and make it work.

    And on that note...I did "blue print" (for you young' in's that means making it to "spec") an AEG totally ignoring all the parts the guy gave me and all I did was swap the inferior battery (Tenergy) and installed a Tienly 35K. Guy was so impressed...then I handed him his bag of "upgrade" parts...and he went wait, what? Priceless!
     
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  4. Squad144

    Squad144 Active Member

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    I thought I was the only one with bevel bushing hole issues! I tell you this, it seems classic army has the same issue in that the bevel gear is off inside the gearbox. It results in a horrible noise coming from the spur and bevel meshing as well as a motor that gets hot rather quick. I swear the shimming is perfect. The meshing between these gears is making me lose my mind!!!!
     
  5. Ben3721

    Ben3721 Well-Known Member

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    I have a classic army shell I was considering using. I'll do a meshing evaluation before I use it.

    I have before in a old cyma seen a spur bushing hole off, it really wrecked those gears.

    It seems for casted shells sometimes they cast the holes, other times they cast then finish them with a machine, which tends to be more random due to human error.

    But a retro arms shell is big bucks and should be correct. I don't know how they messed it up so bad, you'd think the mechanical aspect of the shell would be top priority.
     
  6. Ben3721

    Ben3721 Well-Known Member

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    So they brushed me off pretty harshly. Their logic was that they have made thousands of gearboxes without reports of problems. They also tried to blame my gearset of being low quality, its the latest generation of seigetek 10:1 ssg... I also ran shs 13:1 and 12:1

    So I guess they will continue to make thousands more of defective gearboxes. If you look at photos you can clearly see this issue is persistent with all their latest generation v2 shells. It's not a defect but an off spec issue.

    It's their sales they will be hurting as word spreads among techs to not use these shells due to the issue.

    I've already thrown together everything in a different shell and the problem is gone.
     
  7. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Thus the issue of no standards and "mess" yourself continues...sad really.
     
  8. Ben3721

    Ben3721 Well-Known Member

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    The gearbox feels like it was made backwards. Like external specs are spot on but then they struggled to align the key mechanical parts after.
    I wonder how they decided gear placement. It wouldn't surprise me if all the holes are too far forward from the motor shaft.

    Well its in the past now. Back to a zinc gearbox.
     
  9. aotsukisho

    aotsukisho Well-Known Member

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    That's really too bad, I guess I was lucky or their one-piece shells aren't affected (one new v2.5, two used first-gen v2). I didn't get the best vibe from their tech support either, I had asked them what thread/pitch their trigger/tappet spring standoff posts were and they just emailed me back a link of the internal parts kit for sale.
     
  10. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    They are Czech...it's kind of their nature...
     
  11. OPairoft

    OPairoft Active Member

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    The m249/m60/pkm shells from RA are known to have massive spacing issues for bushing holes also. Really sad that RA still seems to be in the mindset of “let the customers be the beta testers but still charge full price”. But honestly at this point, almost all other internal parts manufacturers are becoming the same.
     
  12. Ben3721

    Ben3721 Well-Known Member

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    Their English was kinda bad in the email.

    There are also new aluminum shells for gelsoft but they seem to be only sold overseas.
     
  13. Ben3721

    Ben3721 Well-Known Member

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    Ran my aeg with a new zinc shell pretty hard today.

    Motor and pinion was fine.

    It's a pity retro arms failed at making a proper split shell. Some other techs are emailing them now too, with photos of their own damage.
     
  14. Squad144

    Squad144 Active Member

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    What zinc shell did you end up using?
     
  15. Ben3721

    Ben3721 Well-Known Member

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    I tried to get what I had before, and ordered two src shells but they apparently were out of stock and sent two reinforced echo 1 shells. However they aren't oem by echo 1, echo 1 shells in their stock guns are pretty bad. But these turned out really nice. They fit my receiver perfectly. Cant really complain when they ship two shells normally sold at like 45 bucks each for just 40 bucks for both.

    I wanted a lonex shell but man those things are sold out everywhere.
     
  16. Squad144

    Squad144 Active Member

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    Did you ever end up testing your classic army shell? Cause all of my classic army shells (I have a Proline, Sportline, and two Nemesis shells) have the bevel gear problem...

    Also, how can an Echo1 shell not be an Echo1 shell? Is it the one that is all black and have no white accent paint but still have the Echo1 symbol engraving?
     
  17. Ben3721

    Ben3721 Well-Known Member

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    I never ended up using the classic army shell. It's trigger hole was warped bad. And I didn't feel like fixing it.

    I will post a photo of a echo 1 shell from a stock gun then of the ones I received. They have a spot where the previous name was casted into the shell that was either filled or milled off. But I just can't find what it was either cloned from or what mold they bought from another oem. It has the echo1 painted on the side, and the externals of the shell appear very precise and line up, unlike other shells, which is unlike echo 1, all other echo 1 products I've touched have been hot garbage. The metal is stronger than the echo 1 shells found in stock guns. It bends rather than cracks. I replace trigger trolley reset posts with a screw in all my builds so I find out how hard the metal really is.

    With photos I legit think only guges would be able to ID the original OEM.

    I'll upload some photos in a bit.
     
  18. Squad144

    Squad144 Active Member

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    Sweet I hope Guges sees this cause we need his brain for this ID!:D
     
  19. Ben3721

    Ben3721 Well-Known Member

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    In the first two photos,, top is the aftermarket reinforced one, bottom is a stock one from a retired mp5.
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    on the reinforced one it has a rectangular spot above the logo that suggests another brand was using the cast before or its just a rebrand. Idk
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  20. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Black one on top with the extra material is an old "Progear/SystemA" Cast Mechbox. Looks like they up bored the holes to 8mm

    Still slinging the old crap about it being a "reinforced" mechbox.

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    Bottom one is a early JG clone of a TM open cavity mechbox.

    Both mechboxes have the "TM" notch, vestigial casting...
     
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