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Pinion to Bevel Shimming


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I had the CA M15 open the other day - I run a Lonex ultimate GB and an A3 motor inside it (So maybe not so CA any more.. though that's how it started off life). I noticed that the pinion gear was starting to see a little wear - nothing that will take it out of action any time soon however it will certainly die eventually if it carries on getting gnawed like that.
 

Honestly the shimming in the Lonex is really good, I made a literal single shim swap around on the spur gear to space out the spur and sector a tad, but that was it, best shimmed GB out the factory I've ever seen. 

I remembered a video I watched some time ago which I thought was interesting, but then never got around to trying the method out, so i went and had a look for it on YT.

I think I'll try this bevel/pinion shimming method - does anyone here practice this technique as a matter of procedure?

 

 

 

 

This guy's channel is actually quite good btw - it's a shame as he's stopped uploading, last video was ages ago.

 

For anyone looking for decent gearbox disassembly and reassembly guides, I actually think he has two of the best on youtube, especially his V3 guide:

 

V3

 

V2

 

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  • Zarrin changed the title to Pinion to Bevel Shimming

That version three gearbox video is excellent. Have consulted it in the past. Even just the manner in which her describes different ways to install the various springs is handy. 

 

As regards the Pinion to bevel shimming, it's the manner in which I do my shimming lately. The only caveat is to make sure it doesn't interfere with a ETU like a Gate titan, if you're using one. Have a friend who starts with the spur gear. Works for him.  Both of us are using fairly tame builds so being slightly off in shimming isn't the end of the world. 

 

One thing I will say is it's usually safer to shim slightly loose rather than too tight. 

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19 minutes ago, DerDer said:

As regards the Pinion to bevel shimming, it's the manner in which I do my shimming lately. 

Cool. I'm guessing the shim job on the other two gears isn't much different to how it would be done otherwise, seeing as the meshing of the spur and bevel is rarely too fussy.

 

22 minutes ago, DerDer said:

One thing I will say is it's usually safer to shim slightly loose rather than too tight. 

 

For sure, one of ways you wanna test that is once your done, close up the shell with a couple of screws and all three gears inside, and spin the gears with a finger through the cylinder port. Ideally you want them to carry on spinning a bit after you let go; if there is resistance when trying to role them or if they stop spinning the moment you release them, they are probably pinched off a bit somewhere.

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Ive done it before a few times, although it can depend on the gears/box is the optimal pinion position suits with the rest of the build.

 

Usually i try to shim the sector/idler as close to the left half of the box as i can get away with which reduces things like tappet plate interferance and gives you the most headroom for moving the bevel to where it's needed.

 

Bearing in mind its not just the shimming, using a mis-matched pinion/bevel (eg an asg pinion onto an shs bevel) means you could get noise no matter what.

 

Even using a fully matched set you could get backlash if the positions of the gears in the box dont match up right, one of the reasons why even a good set of gears could have issues in a certain box.

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Shims UNDER the bevel are not too fussy either

it is the one place you don't have to shim to perfection

as the pinion once installed is never going to allow the bevel to move

Not saying don't bother shimming under bevel...

Just that you won't need to shim it to fine tolerance like other instances to hold in position

 

Take up some of slack under bevel - but don't fret over say fine 0.1mm tolerance say like other instances

Try not to use larger diameter shims under bevel, if you pack a considerable bit with larger diameter shims

it can impede/rub slightly with teeth on spur meshing to bevel I've found

So I tend to/try to use smaller diameter shims under bevel & on top of sector

(smaller diameter shims on top of sector is to reduce possible catching/snagging of tappet fin on sector shim)

 

Rough ball-park figure...

 

Bevel gear: 0.1mm to 0.2mm, maybe 0.25mm on TOP OF BEVEL

(take up some of slack underneath)

 

Spur gear: 0.1mm to 0.2mm UNDERNEATH SPUR

(whatever is required on top)

 

Sector gear - roughly 50/50 centered, check for rubbing against COL if too low

& sector cam rubbing on box if shimmed too high (or thick chunky delay clip installed)

(often a ball-park is whatever the spur has underneath - then add 0.1mm

or 0.2mm under spur, then 0.3mm (ish) under sector, then whatever req on top)

 

When spinning gears, also lay box on its side to listen for more friction/rubbing from gears or against box

(you'd be surprised how sweet it sounds upright, but a tin of wasps on its side, so investigate if you got OCD)

 

Once you got the gears "roughly spaced" or as you got the sector/spur "stacked up" nicely

Turn box over so the selector plate side is facing upwards....

lift sector gear up, checking for play - BUT look closely at spur axle...

If when checking the sector play, the spur's axle lifts too...

then they are stacked a little too close together and/or too much slack on those gears

(if left unchecked - it can produce those "swirl marks" on spur gear)

 

Another check & easier to see on a v3, once finished - have a look at how much of bevel's teeth

actually mesh with spur's teeth through motor entry point...

You want to aim for as much of the bevel/spur's teeth meshing as possible

BUT you will never get it meshing as closely as say the sector-spur - you can get these close without touching

but often the bevel-spur will not mesh anything quite as close...

 

If there is very little meshing at bevel-spur, then try to shim the spur and sector higher

by swapping some shims from top to underneath - keeping the gears together without becoming too tight

(as said say shim the spur (0.3 or something now and also the sector increase underneath & less on top)

 

Reason for this checking the bevel's teeth mesh with spur more...

Moment you get any strain/lockup, the light meshing contact between the bevel-spur

will result in those 10 teeth flying off as little may have made contact with spur

 

You can view this as a weak point - at bevel to spur shim/meshing if you wish

but it stands to reason, if little of the bevel's 10 teeth is making solid contact with spur's teeth

only the tips of 10 teeth mesh with spur - then under load,

the bevel's 10 teeth will tear themselves out at slightest sign of stress

 

BUT - as said, you just won't get enormous near full contact across the width of the teeth like spur/sector

Just check for hardly any contact width & adjust/lift up if possible, the spacing of spur/sector

 

Some bevel's have chunkier and wider 10 teeth cut to spur, meaning better contact than others

It is the instances where hardly any of the bevel's 10 teeth contact the spur

(here is where a bevel may encounter "tooth decay" at some point under stress)

 

Everybody's shimming technique varies & every box is different

(heck some gear sets are smooth as silk in one box & rough in another box)

 

But I check for sector lifting spur (selector plate side up)

how much actual contact bevel to spur, if poor, look to lifting/shifting spur/sector shimming if required

(as said it will never be extremely close, but look to ensure decent contact without throwing out stuff much)

Spinning the gears upright AND on on both sides to listen for rubbing/contact of gears/gearbox case etc... 

 

TL-DR

check for gears being too close together (sector/spur example)

check for decent contact between bevel/spur, or as much as feasible to reduce tooth decay

spin gears upright and on sides (both sides) for any excess rub/friction if you have OCD  like moi :D

 

or fuck it - just slap them in like the 5yr did at the factory sweat shop

(and just say Homer Simpson style - it was like that when I got here/bought it)

 

PS for the record - I know absolutely FUCK ALL tbh...

my latest was a v3, shimming was the bollox - really smooth

dropped motor, that was I thought meshing nicely at height/angle - even angle of cut of gears 90 degrees

 

FUCKING PILE OF SHIT - 10.2amps, low draw but sounded absolutely fucking awful

wobbled motor cage - still sounded SHIT - just doesn't make sense at all

Had to shelve it on Monday & hope to look into it this weekend, likely change motor

or investigate just WTF is up with it, never expected it to sound so crap

after all the attention to detail & sweet it all seemed to go

yet proof of pudding was a tin of angry wasps trapped inside a tin of rusty ol' nuts & bolts

 

So what the fuck do I know - ignore my advice, I know completely fuck all

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Yeah, one would hope you'd be able to mesh a pinion and bevel both made by Lonex together - will see, might try this evening, if not saturday.

 

One of the frustrating things I've found with shimming is it's easy to throw semi auto out the window if you shim the bottom side of the sector too high - the COL section that get's pushed down by the sector's protruding peninsula, is semi grooved meaning that lower chunk of the COL is usually only half as thick as the overall thickness of the piece, so if you shim it up from the bottom too high it sometimes wont engage properly with the sector.

 

This always turns out to be the number one thing I look to avoid in shimming, as a result I like to shim the sector as low down as possible while still allowing appropriate clearances between all the gears, occasionally you'll get a an awkward GB and gear set where achieving that is easier said than done.

 

In my mind, I'm hoping starting the process from the bevel and pinion and then ending up with the sector doesn't force me into the above scenario - but like I mentioned, I don't anticipate having to touch the spur or sector at all - we'll see I guess!

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46 minutes ago, Sitting Duck said:

Reason for this checking the bevel's teeth mesh with spur more...

Moment you get any strain/lockup, the light meshing contact between the bevel-spur

will result in those 10 teeth flying off as little may have made contact with spur

 

Yeah, always worth checking you've got decent tooth engagement.

 

The other fun one is the idler not being true, always notice a little wobble in them.

 

As for noise, my current theory is the metal of cheaper boxes seems to be better at dampening or something, only way i can explain how a jg box seems to sound smooth as silk even with minimal fucks given to shimming.

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2 minutes ago, Adolf Hamster said:

As for noise, my current theory is the metal of cheaper boxes seems to be better at dampening or something, only way i can explain how a jg box seems to sound smooth as silk even with minimal fucks given to shimming.

 

Yeah, it's funny that though - this Lonex ultimate setup is probably the best sounding cycling I've ever heard, it's so brisk and clean .... like a 'tk tk tk' sound, pretty much zero whine or grind; this is why I was slightly surprised to see the wear building up on the pinion gear.

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43 minutes ago, Adolf Hamster said:

 

Yeah, always worth checking you've got decent tooth engagement.

 

The other fun one is the idler not being true, always notice a little wobble in them.

 

As for noise, my current theory is the metal of cheaper boxes seems to be better at dampening or something, only way i can explain how a jg box seems to sound smooth as silk even with minimal fucks given to shimming.

 

LOL - the box I'm having grief with IS A JG

Originally an early one with white plastic 7mm bushings

that I replaced with some 7mm bushings/bearings (50/50 mix)

 

But other than this fuckpig one, I really like JG v3's

These seem to be finished better than cheapo Cyma's

(an unpainted/unfinished 028a box, was fucking razor sharp edges

& once closed the motor cage was loose across the width of base

like the box closed up together way too tightly, even cage tightened there was play)

 

Some JG's are just black on outside, some are painted on inside too

They accept the v3 cylinder head with "lug" where as Cyma's don't...

 

Ultimate Aluminium Cylinder Head for Version 3 Gearbox (Purple) - Airsoft  Shop, Airsoft Guns, Sniper rifles, Airsoft pistols, parts and bbs by  FireSupport

 

JG G36 & SIG use a weird COL with reduced arm cam ??? (silver)

where as their AK's use a regular V3 COL like black SHS one in pic...

 

image.jpeg.1678982650afbaecc47dd1442bff3012.jpeg

 

Other than a couple of qwirks, they are a nicely finished cheap v3 imho

 

Their stock cylinder head is a double o-ring type, that seals very well as std

(fucking way better than shitty loose useless Cyma stock cylinder head)

I've notice some spouts do vary in tightness - nozzle wise

some glide nicely with a new nozzle, but another JG head, the spout is larger/tight fit

(mind you some of these boxes & bits are over 6 years old so variation in manufacturing is expected)

 

Piston head is a fatter/chunkier o-ring, on a flat 5 hole vent, which works well

(slightly widen if you wish, but really works as is, and with cylinder head gives good compression

 

Sometimes 7mm solid bushings, sometimes bearings - or older ones with white plastic bushings

But they are a good box, the way they are finished & what is inside, req very little changed tbh

 

I personally would give JG boxes the slight edge over say basic Cyma v3's due to finish

& slightly better parts inside as standard, a slight tweak & service ends up costing very little

 

but just my opinion for what it is worth 

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So i re-shimmed the bevel today with the above method. I ended up adding one of the very fine 0.1mm shims to the total with 1x 0.1 on the 10 tooth side and about 1mm worth of shims on the broad side of the bevel and results seem very good tbh.

 

While it doesn't sound much different, you could see originally the pinion was riding with a gap between the teeth; the rearrangement brought the pinion downwards sitting nicely into the bevel teeth. I also found that with the new shim config, backing the motor height screw out a 1/4 turn gave the new sweet-spot.

 

The optimal pinion/bevel engagement honestly seemed to be 100% of the shims on the broad side of the bevel, however that caused the bevel and spurr to make too much flat surface contact and I also don't like the idea of running one side totally shimless with bearing bushings - therefore the single 0.1mm shim went in.

 

Overall very happy with the result - I think it should preserve the Lonex pinion gear for some time to come.

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