My First Time Opening a Gearbox (VFC avalon gen 2)

Discussion in 'Gun Building, Modifications & Repairs' started by Evan J Johnston, Jun 8, 2020.

  1. Evan J Johnston

    Evan J Johnston Member

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    Howdy. I'm brand new here and thought I should share my latest repair experience. I will attach photos with some commentary/questions in the replies. I will continue to update this thread as I continue work on my RIF.
    This gun was having semi-auto lock-up issues since brand new, not terribly common, but usually at least once per day of play. Finally felt confident enough to open up the GB and found a tooth broken off on the spur gear. I decided SHS 16:1 gears (same ratio as stock) would serve my needs just fine and be usable for a ~400 fps build later on.
    During shimming, I broke a screw off in the GB shell and failed to extract it, so I will revisit that some other time (drill and re-tap threads).
    I bought a new Lonex GB, which I found does not drop right into the avalon body, it seems to get hung up where the motor grip slides over the GB shell, towards where the trigger would be when fully assembled, as well as towards the back near where the wires pass through to the buffer tube.
    Also had to get a new spring guide since the avalon has a quick change design that cannot be used in a standard gearbox.
    Thank you for reading and I definitely wouldn't mind if anyone offered some insights on what I'm working with XD.
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    Update: I've added a summary of the work I've done to this RIF in the replies. Please be sure to read through the rest of the thread or do some research before asking questions here! Here is the summary:
     
    Last edited: Jun 30, 2020
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  2. Evan J Johnston

    Evan J Johnston Member

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    Lonex GB shell fitment with VFC avalon lower receiver
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    no issues with motor grip fitment onto GB
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    VFC GB vs Lonex GB. Lonex is noticeably beefier in several areas. Bearings are also much closer to being flush with the local surfaces, and don't have super glue leaking out around the bearings, like in the VFC.
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  3. Evan J Johnston

    Evan J Johnston Member

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    Lonex GB came with this set of hardware. 3x flat top long, 1x button top long, 4x button top short. I think there's an error here from evike or lonex because there is only one screwhole with a conical shape that matches the flat top screws. Also, I'm not entirely sure why but 5x locking washers? Are these necessary? Why 5?
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    Last edited: Jun 9, 2020
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  4. Evan J Johnston

    Evan J Johnston Member

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    I purchased this gearset from Mir Tactical, my local airsoft shop. They label these as SHS and told me they are the same gears (same manufacturer), just branded differently. I think I paid like $30. The box was just labeled "CNC". At least that appears to be accurate.
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    I got a set of SHS shims from shootercbgear.com. at least half of the .2mm shims have some imperfections, like they were poorly cut or not deburred. Should I try to debur them myself, or can I use them as is?
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    I picked up some other various parts to try out. The gold colored aluminum piston head was $4.50 on shootercbgear.com and it seems to fit similarly in my cylinder as the stock plastic one. It was branded as "SCG" on the website. I assume the smoothed-out shape going into the nozzle can at least attribute to some better airflow. Can this produce any noticeable differences?
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    I also got a madbull m100 spring to drop the power to meet regulations for the local indoor field. The coloring on the spring flaked everywhere inside the gearbox, so I'm not a fan of that. Otherwise, the quality of the spring seems fine. I ordered a lonex sp100 spring to compare.
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    Finally, I picked up these Maple Leaf rubbers because I have heard good things about them. One for my current build, and one for a future build. Perhaps I should have gotten 2 yellows in case it wears out. I do, however, already have a G&G green rubber installed on my barrel.
    20200608_174644.jpg
    Any insights as to how well rubbers can function based on rotary/traditional wheel style hop-up dials? I thought I heard somewhere that rotary dials have a harder time staying in place, so stiffer rubbers can push them out of place easier?
     
    Last edited: Jun 16, 2020
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  5. aotsukisho

    aotsukisho Active Member

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    Might want to pin both the rear takedown and gearbox/trigger to see fitment without the gearbox moving around freely in the receiver, especially if you are comparing grip fitment

    Mine came with strange hardware too, I doubt it matters but you can always get a proper set from the hardware store. I got screws in stainless to match, don't forget to loctite them in

    I don't know if it makes a difference but it certainly appears it will in theory. I countersink the cylinder head openings in my higher end builds.

    I recommend also getting a Prometheus and/or Guarder spring to compare. I have not used Madbull and the one Lonex spring I bought I think is off spec or mislabeled

    Rotary style usually has notches that the rubber will hold to. In my experience traditional dial hop units have more of a tendency to drift as they rely only on friction.
     
  6. -Spitfire-

    -Spitfire- Well-Known Member Supporting Member

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    Rotary tend to hold position better, though it's possible for there to be exceptions.
     
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  7. Evan J Johnston

    Evan J Johnston Member

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    Shortened original post for ease of reading, and edited title for clarity. :p
    Thanks for the replies.
    Did some more work this weekend, about to upload some photos and videos and update this post with my progress. Having issues with semi-auto. Locking up as if its in safety most the time, but sometimes fires full auto in semi mode if I switch to full auto, fire, then switch to semi.
     
    Last edited: Jun 15, 2020
  8. Evan J Johnston

    Evan J Johnston Member

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    I wasn't able to pin the lonex gearbox into the vfc lower, that was the point of the photo. I had to grind material away in order to get it to fit. Clamped the dremel to my desk for stability. Started with a grinding bit, then smoothed it out with a coarse buffing bit.
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    I'd say this worked really well!
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    Did an all new wiring job. The soldering isn't perfect, but the overall product aint too shabby. That last section of red wire between the fuse and the deans connector is 16awg. Everything else except the signal wire is 18awg.
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    Last edited: Jun 15, 2020
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  9. Evan J Johnston

    Evan J Johnston Member

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    Here's a video demonstration of the issues I'm having with semi-auto.
     
  10. aotsukisho

    aotsukisho Active Member

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    Looking back at the photos now that makes sense. I would have left the motor grip off to better show the alignment of the shell.

    It sounds like your anti-reversal latch is missing or not engaging properly (spring slipped off maybe). The safety lock might be due to the alignment of the safety mechanism being off, make sure it's not binding on anything and the two parts are keyed together properly. All of the safeties I've seen are fairly soft so they can rotate internally which throws off the angle between the selector plate and the trigger stop.
     
    Last edited: Jun 15, 2020
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  11. Evan J Johnston

    Evan J Johnston Member

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    Gotcha. This being a non-QC spring gearbox, it was much more difficult to reassemble and it felt like it was binding up right near the AR latch, but I just kinda forced it closed lol. There was a point when I reshimmed the original gearbox, before I noticed the broken spur, it wasnt locking up going from safe to semi, but it fired full auto in semi every time without fail. Perhaps there's now two separate problems going on here? I'll take a look at it again sometime this week. Really hoping to get out and play this weekend! Thanks for the reply.
     
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  12. Evan J Johnston

    Evan J Johnston Member

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    Looks like my anti-reversal latch axle is bent. My local shop has OEM avalon AR latches and G&G AR latches. Any recommendation before I go check them out? Any materials or build characteristics to look for? I've heard of integrated axles for gears. I don't really know what this means or if its good or bad.
    With the top half of the GB shell removed, the AR seems to function just fine, but when closed, it seems as if it doesn't engage at all. Cut-off lever is also getting worn at the top, so its engaging, but not stopping the gears from spinning. I even installed new Modify springs all around except tappet. They seem stronger.
    Here are some pics and a demo of me spinning the bevel with a screwdriver with everything installed in the GB:
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  13. aotsukisho

    aotsukisho Active Member

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    Ooh yeah that's not good. I would inspect the gearbox carefully around the ARL socket areas to make sure they aren't damaged as well.

    ARL brand I've never noticed to make a difference, they aren't supposed to hold a heavy weight on their ratchet after all.

    The cutoff lever isn't supposed to stop the gears from spinning, it's supposed to kick off the trigger contact trolley from the trigger itself and thus disconnecting power.
     
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  14. Evan J Johnston

    Evan J Johnston Member

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    Right right. Duh.
    I think I just figured out the issue.
    It appears the sector gear is contacting the top surface of the COL, either holding it just high enough where it blocks the part of the trigger trolley that its supposed to slip under, and then lift up on (blocks trolley from moving forward), or even higher so that the COL is doing nothing. I've basically had this issue since the gun was brand new, but it never fired full-auto in semi until I took it apart and reassembled it. It would just lock up in semi, and I could change to full auto, fire it, then switch back to semi and it would work fine for awhile. I've put in a new COL, and the same thing is happening, so the only parts that could affect this that are from the original VFC gearbox are the trigger trolley and contact assembly.

    I don't think it will be a good idea to shim the sector any higher. I think shaving down material on the sector could produce bad results, or be too easy to mess up, and I think trying to shim the trigger trolley will produce unreliable results with the materials I'm thinking of using (tape or paper).
     
    Last edited: Jun 18, 2020
  15. aotsukisho

    aotsukisho Active Member

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    It's possible that the trigger components are out of spec, it's also possible that the trigger contact assembly is mounted off spec as well. I'd loosen the screw holding it down and see how much play in all directions it had compared to how it was assembled. I've had a gearbox give me nasty problems with trigger tolerances, tried mixing and matching a whole bunch of brands of parts in order to get it to work.

    I've also incorrectly installed the cutoff lever before, it was not interacting with the trigger trolley correctly. Externally, the cutoff lever would not disengage in full-auto correctly - like it would stop moving a couple mm early. I remember this clearly since the symptoms were just like yours, full-auto in semi. Maybe you can try confirming proper cutoff operation with the gearbox open and installing just the cutoff lever/selector/spring, trigger contact assembly, and trigger/spring.
     
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  16. Evan J Johnston

    Evan J Johnston Member

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    Good info. I did pick up an SHS trigger contact assembly so I will use those pieces one at a time to see if anything changes when fully assembled. I have tested with the sector gear removed, and the cut off function works flawlessly in that scenario. The SG is the only part affecting the cut off mechanism that is not held in place sufficiently when the gearbox is open.
     
  17. Evan J Johnston

    Evan J Johnston Member

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    Heres another demo of the issue I'm working with. New cutoff lever did nothing. Swapping trolley did nothing. After putting in a whole trigger contact unit and seeing some promising results, I decided to try and replace the mosfet onto the new unit which seems to have worked well, still have to test it though. I went for removal of the original mosfet and I almost had it, and I think would have come free near perfectly had I undone the plate that holds the contacts to the plastic assembly before trying to pry it off. I had a spare unit however and was able to separate that one successfully and replaced it on my "shs" unit. It was labeled shs by my local shop but seems more similar in build to a lonex just judging by pictures online. Material appears to be nylon fiber/polymer.
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  18. Evan J Johnston

    Evan J Johnston Member

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    Got some Facebook consultation on this, and many saidt that"higher end" guns as of late have an issue with contact unit fitment. Supposedly "off spec" as you said. Can't remember if it's supposed to be TM spec or not or maybe new TM spec vs old. Kinda got lost in translation on that one. I was recommended an shs red unit so that will be my next purchase if this new black one doesn't work out well. Important note that I probably should have mentioned sooner: My contact unit did in fact fit VERY tight to the pin in the gearbox. I filed it out a bit to help it out. Really didn't even consider that in my diagnoses tbh.
     
  19. aotsukisho

    aotsukisho Active Member

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    I shot a quick vid for function testing the cutoff lever without too many components installed, does your gun pass this? Notably try doing semi/full auto selector plate engagement with the cutoff lever without the gears in, trigger should pull cleanly on both modes. If the cutoff levers are sticking halfway that can affect trolley movement, you might need to shim the lever upwards
     
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  20. Evan J Johnston

    Evan J Johnston Member

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    So, I swapped around trigger contact components and put the original VFC COL back in. Had it working for a bit, put the whole thing back together and went to chrono. Reported about 150-160 FPS with hop turned all the way off. Got like 10-15 shots and then it stopped firing altogether. Not sure if I was using .2g or .28g as I mixed up the mags before I was able to label them. Previously the gun was shooting ~314fps with a .28g BB.
     
    Last edited: Jun 26, 2020