Advice Wanted V2 Gearbox

[Just Joe]

Hi All,

I recently bought a G&P Magpul Moe with some miles on the clock for a good price. Bought with the view of learning how to work on gearboxes for myself in the long run. Just figured it was a good place to start as there is plenty of content out there for advise on how to install certain parts and correct methods.

I've stripped the gear box and I'm currently in the process of getting my head around AofE and shimming.

 

I believe I've correct A of E correctly with a sorbo pad, the sector gear meets the piston at around the 1 o'clock position with the spring in. The sorbo pad however, in diameter a 0.5-1mm wider then that of the cylinder head. Is that much of an issue or not?

Secondly, looking at the shimming. When I opened up the gearbox I found that there was bearings instead of bushings, which I wasn't expecting. The bearings in certain sections have a tiny amount of movement, but on the bevel gear, quite alot. I will try and upload a video but its close to 1mm maybe pushing 2mm movement in the cut out for the bearing (horizontal movement when gear box is upright). 
From my understanding this will negate any shimming efforts by myself, its quite a lot of movement.

I have ordered some SHS bushings, however if I get the same effect I feel logic says I would have to bond the bearings or bushings into the gearbox. 

 

If I do have to do this, is best to have the bearing/bushing in as deep as possible and then shim from this point?

 

Also, bearing or bushings?

 

The plan is to stick to stock internals, install a gate aster mosfter and run 11.1 Lipo on the stock GPM120 motor.

 

Any advice on the points above would be great!

[Skara]

MUST CORRECT AOE! THE INTERNET GUY SAID SO!

[Lozart]

Can you post some pictures? Might help explain.

[Just Joe]

1 minute ago, Skara said:

MUST CORRECT AOE! THE INTERNET GUY SAID SO!

Thanks for your constructive help

I can get some up later tonight. 

 

Both bearings on the bevel gear are very loose and seem to have an excessive amount of movement to protrude out the gearbox shell. Doesn't happen on the others so seems strange to me.

Thank you for your comment 

[DerDer]

Bearings can be quieter and lead to a RPS boost. But would recommend switching over to bushings if you have the funds and time. Higher level of reliability, particularly when running a 11.1v lipo. Also if you are just starting out with the teching, they can be more forgiving.  

[Skara]

23 minutes ago, Just Joe said:

Thanks for your constructive help

You're welcome.

 

AOE is a non existing issue, gears have been engineered to contact the piston rack at a certain angle to ensure a nice and constant transfer of energy.

There are TWO cases in which the AOE should be corrected, LMG gearboxes and super duper ultra hyper high speed builds, and even then it's a matter of half a millimetre at most, sorted by spacing the piston head from the body with a really thin washer, half a millimetre tops as I previously stated.

By slapping a 5mm thick sorbothane pad you've just created more issues (piston rack doesn't contact the gears like it's supposed to, so now you have to remove teeth from the rack itself to avoid PME-premature engagement of the gears-, causing even more issues, you have also vastly increased the stress on the pickup tooth of the rack, which at some point will just explode because instead of transferring the stress as it's supposed to, it now slaps against the first sector tooth) to fix a problem that WASN'T THERE IN THE FIRST PLACE, especially on a standard 18:1 build like yours.

But hey, a random cunt on the internet said so, without providing any evidence of the AOE being useful on his build other than "a friend of mine did it and it worked", must be true, right?

 

Regarding the bearings being loose, could be a whole lot of different factors, what comes to mind is:

-the gun has been used A LOT so the bearings are now worn out and need replacing;

-bearings are of bad quality;

-the guy who worked on the gun knew fuck all and messed something up.

Hard to tell without detailed pictures.

 

Bushings are much more solid than bearings but create more attrition with the gear shaft, effectively lowering the RPS (not by much, could be 1/2 RPS at worst, unnoticeable). They generally require less care.

[Adolf Hamster]

aoe is something that should be checked and sometimes adjusted, but very often it gets over-corrected to ridiculous levels or adjusted in guns where there wasnt an issue to begin with, and i've never seen a gun that needed more than 2mm max of spacing to achieve it.

 

what you want is a nice smooth pickup of the piston rather than "must be at the 12 o clock position".

 

i can't say i agree with the whole "well manufacturers aren't doing it" argument, some do (for example e&l's thicker piston heads do effectively the same job and if you change to a standard head you need to correct the aoe) and lets face it manufacturers like nuprol exist, but that's a can of worms for another thread.

 

the way i tend to check is with the piston fully forward and no spring i'll close the halves together and turn the sector by hand to feel if there's any catching.

 

i tend to prefer putting something in the cylinder rather than on the piston as i like to keep the mass of the piston low (for example i don't run thrust bearings on the piston, only the spring guide), but unless it's a high speed build you can certainly get away with spacing on the piston rather than the cylinder.

 

 

as for the bearings are you meaning that they're loose in the shell? because the shimming will help hold them in position, if you're meaning the inner section is moving independently of the rest of the bearing then they're worn out.

[Just Joe]

27 minutes ago, Skara said:

You're welcome.

 

AOE is a non existing issue, gears have been engineered to contact the piston rack at a certain angle to ensure a nice and constant transfer of energy.

There are TWO cases in which the AOE should be corrected, LMG gearboxes and super duper ultra hyper high speed builds, and even then it's a matter of half a millimetre at most, sorted by spacing the piston head from the body with a really thin washer, half a millimetre tops as I previously stated.

By slapping a 5mm thick sorbothane pad you've just created more issues (piston rack doesn't contact the gears like it's supposed to, so now you have to remove teeth from the rack itself to avoid PME-premature engagement of the gears-, causing even more issues, you have also vastly increased the stress on the pickup tooth of the rack, which at some point will just explode because instead of transferring the stress as it's supposed to, it now slaps against the first sector tooth) to fix a problem that WASN'T THERE IN THE FIRST PLACE, especially on a standard 18:1 build like yours.

But hey, a random cunt on the internet said so, without providing any evidence of the AOE being useful on his build other than "a friend of mine did it and it worked", must be true, right?

 

Regarding the bearings being loose, could be a whole lot of different factors, what comes to mind is:

-the gun has been used A LOT so the bearings are now worn out and need replacing;

-bearings are of bad quality;

-the guy who worked on the gun knew fuck all and messed something up.

Hard to tell without detailed pictures.

 

Bushings are much more solid than bearings but create more attrition with the gear shaft, effectively lowering the RPS (not by much, could be 1/2 RPS at worst, unnoticeable). They generally require less care.

 

 

Thanks for sending this.

I can easily enough revert AOE. A SHS cylinder head isn't much money. I feel the airseal isn't good enough as well. The cylinder head sits somewhat loose in the cylinder itself. One thing at a time though.
Just following advice from what appear to be reputable airsoft techs. Feel like I'm being told off by my old man here.

I'll get some pictures, i'll try and get a video up too later of the bearing issue. 

I've ordered some 8mm bushings. Based upon what you have said about them requiring less care it makes sense for my current extremely limited abilities. 

Pictures are clearly going to help massively here so let me get them up but thank you for the help.

6 minutes ago, Adolf Hamster said:

aoe is something that should be checked and sometimes adjusted, but very often it gets over-corrected to ridiculous levels or adjusted in guns where there wasnt an issue to begin with, and i've never seen a gun that needed more than 2mm max of spacing to achieve it.

 

what you want is a nice smooth pickup of the piston rather than "must be at the 12 o clock position".

 

i can't say i agree with the whole "well manufacturers aren't doing it" argument, some do (for example e&l's thicker piston heads do effectively the same job and if you change to a standard head you need to correct the aoe) and lets face it manufacturers like nuprol exist, but that's a can of worms for another thread.

 

the way i tend to check is with the piston fully forward and no spring i'll close the halves together and turn the sector by hand to feel if there's any catching.

 

i tend to prefer putting something in the cylinder rather than on the piston as i like to keep the mass of the piston low (for example i don't run thrust bearings on the piston, only the spring guide), but unless it's a high speed build you can certainly get away with spacing on the piston rather than the cylinder.

 

 

as for the bearings are you meaning that they're loose in the shell? because the shimming will help hold them in position, if you're meaning the inner section is moving independently of the rest of the bearing then they're worn out.

Thanks for the reply. 

I'll get some pictures up tonight of everything. I'll upload a picture here of the previous AOE before my treasonous crimes of using a sorbo pad.


Based on what you said about the bearings being loose and that shimming will help them in position. This may just be the case, it does seem like I would need a fuck tonne of 0.1mm shimms in order to negate the movement. Would that be normal?

 

[Skara]

31 minutes ago, Just Joe said:

One thing at a time though.

Absolutely correct, one step at a time so you learn how each part interacts with the system and changes the performance.

 

Sorry if I sounded rough, but the whole AOE argument always pisses me off. if said angle was really wank I am sure TM (the company who invented the gearbox) would've addressed it in the design stage  they aren't know for "eh, good enough" when engineering and manufacturing stuff

Some conspiracy theorist say that it was deliberately done to prevent people from having a functional gun with a stronger (illegal) spring in Japan, but it's mostly faff just like every conspiracy theory out there.

 

 

This is how involute gears (same shape as the gear teeth in our gearboxes) are meant to work. As @Adolf Hamsterpointed out, in some cases a very slight correction has to be done (I've narrowed it down to two very specific cases, mistake on my side ) but it's mostly due to tolerances and in most cases it's negligible, it may shorten down the lifespan of a piston by idk, 1000 cycles? over an effective life of hundreds of thousands cycles. Piston failures are more due to the actual quality of the part (Ares dark earth pistons say hello), rather than an imperceptible difference in the angle at which the sector gear interacts with them.

As mentioned in my previous post, in LMG type boxes there is just a design flaw that kills pistons really quickly, basically the piston rests too far forward for the sector gear to properly pick it up, so the geat tooth strikes the "bottom" of the piston's pick up tooth and smashes it to pieces. In that case a shim/pad is required

 

You then have so called "techs" who say "eh fuck mechanical laws, hold my beer" and come up with uber thick pads, giving no mechanical or physical explanation other than "I'm right, you're wrong, fuck you, 'murica"

[Adolf Hamster]

2 hours ago, Just Joe said:

Feel like I'm being told off by my old man here.

 

is it racist if i blame it on him being italian

 

(you know i love you really @Skara )

 

2 hours ago, Just Joe said:

I'll get some pictures up tonight of everything. I'll upload a picture here of the previous AOE before my treasonous crimes of using a sorbo pad.

 

to my eye (caveat ofc that it's just one photo) it wouldn't hurt to shift it back a bit, not too much though.

 

i'd also be sure to check the piston isnt rubbing on the gear- that extended rear tooth looks like it might be rubbing.

 

3 hours ago, Just Joe said:

I feel the airseal isn't good enough as well

 

if, like me, your objective is perfect accuracy then the air seal is never good enough

 

3 hours ago, Just Joe said:

it does seem like I would need a fuck tonne of 0.1mm shimms in order to negate the movement. Would that be normal?

 

hard to say, but i have had boxes *cough*lct*cough* that needed as much as 1.5mm of shims.

 

that's admittedly on the extreme end but not unheard of.

 

personally i like these kits from ak2m4:

https://www.ak2m4.co.uk/internal-parts/bushings-shims/xt-shim-set-etched

 

because it's real handy having them marked what they are.

 

2 hours ago, Skara said:

Absolutely correct, one step at a time so you learn how each part interacts with the system and changes the performance.

 

^this

 

2 hours ago, Skara said:

Sorry if I sounded rough, but the whole AOE argument always pisses me off. if said angle was really wank I am sure TM (the company who invented the gearbox) would've addressed it in the design stage  they aren't know for "eh, good enough" when engineering and manufacturing stuff

 

can't say i've ever opened a stock marui box to see what their stock aoe is like, but i reckon it's less about design and more about manufacturing tolerance, or lack thereof.

 

plus it's possible that in the very early days marui didn't put in as much effort as they would now purely because they wouldn't have known what they were starting/didn't think it was going to take off like it did, although take that with the huge pinch of salt required for one guy speculating on the internet.

 

2 hours ago, Skara said:

Some conspiracy theorist say that it was deliberately done to prevent people from having a functional gun with a stronger (illegal) spring in Japan, but it's mostly faff just like every conspiracy theory out there.

 

must admit not heard that one before, although certainly i can see them not bothering to correct something that wouldn't be an issue with a sub 1j gun being cranked by 90's spec nicads.

 

2 hours ago, Skara said:

You then have so called "techs" who say "eh fuck mechanical laws, hold my beer" and come up with uber thick pads, giving no mechanical or physical explanation other than "I'm right, you're wrong, fuck you, 'murica"

 

yep, the issue with aoe correction the impression given that it needs done to every gun, when the reality is some guns need it, some don't, some need a little, some need a lot. the "5mm of sorbo minimum in everything" school of thought is as ridiculous as suggesting every gun needs 2mm of shims on every gear to work properly, which is the message i think folk like yourself and negative airsoft are really trying to get across.

[Just Joe]

2 hours ago, Skara said:

Absolutely correct, one step at a time so you learn how each part interacts with the system and changes the performance.

 

 

I do have a big long list of things I need to have done by the 9th Jan.

I ordered an SHS cylinder head that will hopefully get the airseal a bit better and reverse the AOE change.

For the fucking life of me I can't find the SHS shims I bought. But reshim once I figure out what the hell is going on with the bearing on the bevel gear, I feel like i've missunderstood shimming a bit and it may just need way more shims then the other gears. Hopefully my pictures later clear this up.
Dremel 2/3 teeth of the release side of the sector gear

M110 spring

Install my Gate aster (probably was a bit overkill but couldn't be arsed with soldering)

Got to see the difference between bushings and bearings. Presumably going with bushings.

 

I have a maple leaf bucking and nub. Also have all the gear to "R" hop. Tempted but gearbox first. 

Don't worry about sounding rough, you've gone out your way to help me so thank you.

 

[Skara]

2 minutes ago, Just Joe said:

Dremel 2/3 teeth of the release side of the sector gear

 

I'd do that from the pickup side, so you don't screw up the tappet timing.

But that's just me, it may have no downsides so I'll let someone else confirm/deny this 

 

There are two main schools of thought about shimming: spur first and bevel first. Up to you to decide which one you want to follow, I personally do the spur first, but there are plenty of people who do pinion-bevel first and achieve quiet running boxes.

Shimming isn't hard to do, but it requires patience at first.

 

R-Hop is kind of a gimmick when Maple Leaf exists, keep it as the absolute last thing to do (you may find the ML rubber to be adequate enough for your project).

 

Also be aware that the Aster requires a bit more care than say a Titan/Perun during installation as it needs some gearbox bits sanded down, plenty of detailed instructions found online though so shouldn't be too difficult.

Also keep in mind that some users had issues with the trigger hitting the wires, this causes the whole board to move and messes up the trigger readings.

[Just Joe]

4 minutes ago, Skara said:

I'd do that from the pickup side, so you don't screw up the tappet timing.

But that's just me, it may have no downsides so I'll let someone else confirm/deny this 

 

There are two main schools of thought about shimming: spur first and bevel first. Up to you to decide which one you want to follow, I personally do the spur first, but there are plenty of people who do pinion-bevel first and achieve quiet running boxes.

Shimming isn't hard to do, but it requires patience at first.

 

R-Hop is kind of a gimmick when Maple Leaf exists, keep it as the absolute last thing to do (you may find the ML rubber to be adequate enough for your project).

 

Also be aware that the Aster requires a bit more care than say a Titan/Perun during installation as it needs some gearbox bits sanded down, plenty of detailed instructions found online though so shouldn't be too difficult.

Also keep in mind that some users had issues with the trigger hitting the wires, this causes the whole board to move and messes up the trigger readings.

 

Can I ask why you would do it from the pick up side? 

I had been following a pinion - bevel first. But I see where you are coming from with doing it this way - I did think that the bevel to pinion had the most tolerance due to how the gears intertwined. Could be horribly wrong on that.

I've got a fair bit of patience and plenty of time. 

I've just issued a return on the Gate Aster - Sounds way to complex for me.

Do you have another suggestion for 11.1 set up?

I'll try the ML set up on the 9th. See how I get on. 

Does what I have said seem appropiate for a just achieving a nicer better working AEG?

[Skara]

44 minutes ago, Just Joe said:

Can I ask why you would do it from the pick up side? 

If you look at how the whole system works:

1. motor spins the gears;
2. tappet plate fin gets pulled back by the sector's pin (you have a delayer on that, it's the round metal thingy that's offset from the axle, its purpose is to keep the nozzle retracted for longer than usual to ensure that the bb is fully lifted), tappet pulls the nozzle back allowing a bb to get pushed up, at roughly the same time the piston is beginning to move back and compress the spring;
3. gears are still spinning, the tappet fin clears the delayer and is sprung back forward along with the nozzle, this effectively chambers the bb and seals the nozzle into the hop unit, specifically in the rubber's feed lips;
4. gears are still spinning, the last gear tooth clears the piston rack, piston is pushed forward under tension from the main spring, compresses the air that goes through the nozzle into the barrel and the magic happens.

If you remove teeth from the pickup side, nothing bad really happens, the cycle is still the same but the piston is now being pulled between steps 2 and 3 (doesn't affect anything), is still released when it's supposed to, after the nozzle has sealed and the bb is in position to be fired. You can compensate by applying some precocking with a smart mosfet like the Aster.

 

If you remove them from the release side you're effectively reducing the time from when the nozzle goes in battery and the piston is released, if you reduce it too much there is a chance that the piston is released too soon, worst case scenario the piston is released when the nozzle is still retracted and hasn't sealed against the hop rubber lips, in that case you get zero energy output and there is not much you can do about it apart from replacing the gear.

 

In either case a stronger spring is required to make up for the loss of "stroke"

 

Now I have listed the extreme case, but imo it's better to be safe than sorry.

 

44 minutes ago, Just Joe said:

I had been following a pinion - bevel first. But I see where you are coming from with doing it this way - I did think that the bevel to pinion had the most tolerance due to how the gears intertwined. Could be horribly wrong on that.

As I said it takes time and practice, my first attempt at shimming went horribly wrong, it was so tight that a SHS HT couldn't pull a M90 on 18:1 gears lol

 

44 minutes ago, Just Joe said:

Do you have another suggestion for 11.1 set up?

Your current one is good, no idea why you are returning the Aster, the quirks I mentioned are valid for all the optical mosfets available. Get a tech to do the installation for you if you are not confident enough

[Adolf Hamster]

46 minutes ago, Skara said:

There are two main schools of thought about shimming: spur first and bevel first. Up to you to decide which one you want to follow, I personally do the spur first, but there are plenty of people who do pinion-bevel first and achieve quiet running boxes.

Shimming isn't hard to do, but it requires patience at first.

 

i'd go for sector through to the bevel first, with the sector biased to the right side (upper if you're working on the left box half as i tend to)

 

then once i've got them set i'll adjust the bevel up/down to match the pinion within the range where you're still getting good enough engagement with the idler.

 

but it's one of those things that you can kind of do it however you like as long as the gears aren't binding with anything, aren't too tight/loose and the pinion position isn't too egregious.

 

52 minutes ago, Skara said:

I'd do that from the pickup side, so you don't screw up the tappet timing.

But that's just me, it may have no downsides so I'll let someone else confirm/deny this 

 

y'know short stroking isn't something i've done all that often but when i did i used to do release side, but i can't say i have any valid reason for that. i can definitely see the logic in what you're saying.

 

42 minutes ago, Just Joe said:

Do you have another suggestion for 11.1 set up?

 

depends on the functionality you want, but i'm kind of liking the warfet these days for a milder build (ie not extreme response/rof builds that merit a titan).

 

gives you some nice snappy response with precocking and not too bad to wire in if you're not afraid of a soldering iron.

[Just Joe]

So I just got in, I tried putting every shim i had that came out the AEG onto the bevel gear to negate any play. I had no idea what the size of these shims are though.

 

Hopefully you will see what I mean from this video. It still moves but is better then before.

Couple of images of present AOE. 

And a video.

Piston and the sector gear seem to have a very small gap between them. 

 

The none pick up side of the gear doesn't look all that round. 

Video of one of the bearings, this is how I would presume they would all fit

 

 

If any further videos would help let me know

If this aster gate is good I will continue with that. I'm sure with enough patience I'll be able to get it in.

 

First thing for me would be to rebuild this gear box with appropriate shimming

[Sitting Duck]

I assume 2 things...

 

I hope you fixed the sorbo pad FIRST, then the more robust rubber pad on top

(else the sorbo will shred to bits very quickly)

 

If you are going to short stroke - you might need a metal rack or part metal rack piston

(still plastic, but teeth should be say half metal at least for SS-ing)

 

also that white piston appears to be plastic teeth...

I hope you have it part metal with the last few teeth or a 50/50 mix

coz you will need the final tooth that releases to be of metal than plastic

 

it will work - but the last tooth or two should be metal to ensure durability long term

[Shamal]

Bloody hell what a curfuffle!Just buy a new gnu if it breaks.

I might take up knitting.its simpler...🧶😉

Regards 

 

[NathanW8]

@Skara Grazie millie! I'm an engineer and when I saw a video of someone shimming a pistons with washers and cutting teeth off, I was very confused. They preloaded the spring and have just one tooth where there would have been 2 or 3. Plus a heavier piston to accelerate and stop, along with reduced cylinder volume. I couldn't see the reason why, I thought I was missing somthing.

[Adolf Hamster]

23 minutes ago, NathanW8 said:

@Skara Grazie millie! I'm an engineer and when I saw a video of someone shimming a pistons with washers and cutting teeth off, I was very confused. They preloaded the spring and have just one tooth where there would have been 2 or 3. Plus a heavier piston to accelerate and stop, along with reduced cylinder volume. I couldn't see the reason why, I thought I was missing somthing.

 

Apart from the heavier piston side of things it's pretty much all done in the name of a higher rate of fire.

 

It's a debhilitating condition that starts with fast motors, evolves to short-stroking but if left unchecked can lead to dsg builds.

 

The final stage of the illness is scrapping the gearbox entirely and fitting a hosepipe to it at which point there's nothing for it but a good ol' fashioned witch burning.

 

Man that post got increasingly off-brand as it proceeded