Pinion to Bevel Shimming

[Zarrin]

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?

 

[DerDer]

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. 

 

[Zarrin]

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.

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.

 

[Adolf Hamster]

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.

 

[Sitting Duck]

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

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

 

[Zarrin]

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!

 

[Adolf Hamster]

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.

 

[Zarrin]

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.

 

[Sitting Duck]

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...

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...

View attachment 63453

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 

 

[Zarrin]

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.

 

[Skara]

Lemme necro this.

Yesterday I was discussing shimming techniques with a random dude on a discord server I'm in.

He's a fan of the bevel to pinion method, I'm not, he didn't give me anything to support his thesis other than "every good tech does it".

There are 5 components to shimming, the "energy" travels from the battery to: pinion, bevel, spur/idler, sector, piston in this order.

So looking at it this way, correctly setting up the pinion and bevel first would make sense.

But then we look at how much each component can be moved around and we notice that the sector can't be shimmed too high, as it'll grab on the tappet plate and has a chance to miss/not engage properly with the COL, nor shimmed too low otherwise it'll grind against the spur. This gear engages other stuff in only ONE direction (perpendicular to its axis).

We then notice that the spur gear generally wants to sit as low as possible (one or no shims depending on how the gearbox shell and bushings/bearings sit in their slots) to allow the sector to sit low too (optimal engagement of the piston rack, COL and low chance of grabbing the tappet plate), having the spur sitting as low as possible also allows more adjustment in case either the sector/bevel need to sit higher for some reason. Just like the sector, this thing only engages other gears in ONE direction.

Then the bevel gear. This gear gets engaged from TWO different directions (perpendicular to its axis with the spur and ARL, at an angle with the pinion). As with all gears, the trick is to have it contact the spur teeth as much as possible to avoid unnecessary stress, premature wear and breakages.

Last, but not least, the pinion.

This thing only engages the bevel gear at a fixed angle and has the largest range of adjusment via the screw on the pistol grip, which allows some pretty dank fine tuning compared to the rest of the system.

Looking at the way the bevel and pinion work, they'll always mesh well regardless of where the bevel sits (gear sits lower, motor will sit further away, gear sits higher, motor will be pushed deeper into the box) provided that the pinion is actually compatible with the bevel.

By this last point, it makes no sense to me to tune the pinion/bevel meshing first.

What if you fuck up and shim the bevel so high that you in turn need to shim the spur high too, consequently the sector will sit WAY too high and grab the tappet/miss the COL/interfere with something like an optical mosfet?

Why would you "use" the finest and widest range of adjustment (motor height) from the start?

Am I missing something?

 

[Adolf Hamster]

Honestly as long as nothing is catching and binding, and theres not enough free motion to allow it, then its good enough.

Once the sector/idler have been set the pinion only has so far you can move while maintaining good contact which limits how perfect you can get it.

There is a level of adjustment at the pinion via the motor that you dont get with the other gears, and its more important the whole system is running smooth.

Tbh its kind of academic as technically you should also be ensuring all the gears are matched manufacture too (no sense having perfect pinion-bevel shimming and mismatched tooth profile).

Same applies to backlash, even a matched set can have issues if its not the right set for the box.

 

[AK47frizzle]

By this last point, it makes no sense to me to tune the pinion/bevel meshing first.

What if you fuck up and shim the bevel so high that you in turn need to shim the spur high too, consequently the sector will sit WAY too high and grab the tappet/miss the COL/interfere with something like an optical mosfet?

Why would you "use" the finest and widest range of adjustment (motor height) from the start?

Am I missing something?

Because it's not that wide range. Even though you move the bevel and motor up and down, they have only one optimal position where they mesh the best, and most people want to achieve that before anything else because it's the most important drive. No other gear mesh has more impact than the bevel and motor. So it makes sense to get the most important one first because everything else is easy after that. Obviously, it may not work all the time, and that's why you'd adjust it to compromise. But in general, pinion to bevel meshing is the critical one you want to get right for efficiency and longevity.

 

[Sitting Duck]

I think the answer is ALL OF THE GEARS matter

They all have to sit at their optimal position

I personally work backwards - I've been told this numerous times

I roughly set sector in middle - maybe low middle of box,

then sector-spur together - check for lifting of axles etc...

then remove both & set bevel to pinion as perfect as possible

after motor height/pinion is just correct height just fully engaging the bevel at outer edge

(play or walk of about 0.15mm to 0.20mm)

then drop the spur/sector back in & check for good meshing between bevel/spur

(if not adjust if possible the shimming/spacing on spur/sector)

As said I know the rough ball park, so lifting the spur/sector up is fairly straight forward

but as I've shimmed the pair originally I already know if sector rubs on COL or top casing/tappet

(and if I lift spur only up too much, the risk of swirling on sector for example)

Shimming is an art almost in itself & we are still learning & perfecting out methods/technique

but one thing I do know - at times there is certainly a sprinkling of luck or good fortune

sometimes it sounds smoother than silk & others it still sounds a bit rough - despite our best efforts/planning

(that fucking JG v3 - changed motor in the end and it shut up at last

It was all bang on but sounded rough on original motor no matter what I tried)

Latest thing I'm messing with has very little space to play with at all

so each build is a new challenge in itself to obtain the best optimal shimming

and subsequently - our own personal shimming methods/techniques are tested & evolve as we go

(what I do know is shimming should be easier & quicker as we go on & so called "master" these crap toy guns

yet for some OCD reason I'm finding me being tart so much means builds take a little bit longer with each time)

Fuck me I ain't that bad though...

If you watch Rogers - Shut up gears pt 1~3, well yeah that is perhaps a little bit too nutz on shimming

but a bit that, a bit of something else, noting somebody else's technique together with my own crap...

mashed up together - is what I call my own personal method or approach to shimming

(but for the record I'm still learning myself with ever box/build, coz they are all different as always)

 

[Adolf Hamster]

(that fucking JG v3 - changed motor in the end and it shut up at last)

just goes to show, my experience with jg boxes is with all the original parts they run smooth as anything no matter what you do to them. maybe they wear in? all the ones i've worked on have been pretty old.

there can also be differences in gearing even within manufacturers, was working on a g&g recently that sounded like absolute crap, until i changed the bevel from the g&g bevel to a g&g bevel.......

tbf, the original bevel looked to have fewer teeth than the replacement, maybe gear reduction for a hotter spring (gun had been "downgraded" by drilling a hole in the cylinder), but with the correct spring and higher tooth bevel she ran pretty damn nice.

 

[Sitting Duck]

just goes to show, my experience with jg boxes is with all the original parts they run smooth as anything no matter what you do to them. maybe they wear in? all the ones i've worked on have been pretty old.

there can also be differences in gearing even within manufacturers, was working on a g&g recently that sounded like absolute crap, until i changed the bevel from the g&g bevel to a g&g bevel.......

tbf, the original bevel looked to have fewer teeth than the replacement, maybe gear reduction for a hotter spring (gun had been "downgraded" by drilling a hole in the cylinder), but with the correct spring and higher tooth bevel she ran pretty damn nice.

Did you know G&G make a bevel in usual 10 teeth

plus the 9 tooth bevel like ZCI

BUT ALSO AN 8 TOOTH BEVEL that was fitted to slower FH's

https://www.guay2.com/en/product/detail-977

hence why some FH's were quite snappy

& others were a bit sluggish

I've found there "appears" to be two types og G&G pinions...

one has the teeth cut straight with the actual tooth/teeth cut all right down to base of pinion

others appear to slightly curved, with the tooth/teeth slightly angled at base

now there could be variations due age/revisions on G&G motors I've come across

but some bevels the outer teeth at base of pinion are sometimes cut like arrow

so when setting height, you gotta remember the base of pinion is not always what it appears

pic says 1,000 words as they say...

see this pinion's "cut"...

fairly straight - right ???

now look at this one...

the base of teeth are cut backwards at the end

and this apparently is a G&G pinion that "appears" to be a bit curved in the way the teeth are cut

View attachment 65366

I've definately looked at some G&G motors and swore blind the teeth appear slightly curved than straight cut

but then looked at other motors from G&G guns and they looked different to others

Then again - I've found Big Dragon motors/pinions seem to mesh nicely with cheapo Cyma bevels

but not so smooth on other guns/boxes/pinions

it is a tiny bit of pot luck or hit n miss getting some shit to mesh perfectly smooth with other crap

 

[Adolf Hamster]

i was meaning the teeth that are engaging with the idler gear, the bevel faces looked the same.

 

[Skara]

gun had been "downgraded" by drilling a hole in the cylinder

It's a quick and cheap way to reduce the energy. don't see anything wrong with it (if done properly)

 

[Sitting Duck]

i was meaning the teeth that are engaging with the idler gear, the bevel faces looked the same.

Well that correlates with why some gearsets work better in some boxes

& other gearsets work better in other boxes....

eg: sometimes SHS 13:1's roll really smooth in many boxes

& sometimes the cheaper ZCI/BD/XYZ 13:1's roll smoother

(the bevels in cheapo 13:1's are a bit more miss than hit I'll agree)

my theory is that some boxes have those 3 axle holes set slightly different and in certain instances

some gear sets may allow the 3 gears teeth to engage too deeply and almost bottom out

suffice to say you get more gear noise as they mesh a whisker too deeply

(or at least until they get "run in" a bit)

It's a quick and cheap way to reduce the energy. don't see anything wrong with it (if done properly)

yeah tell that "if done properly" bit to G&G on their HC05 FH...

NO THAT WAS NOT MY WORK - how it came from G&G

& it was not finished very well - some twat just got a Black & Decker

and went - fuck it, about there roughly should be about right-ish

left the inside as rough as fuck, maybe went over it from outside with round file

but inside was burred a bit, a really bodge indeed

(that is before I did my own bodge up on it)

 

[Skara]

G&G being G&G

Heh, that is a shit job.

The one I did on both my amoebas was fine though. Still drilled, but I did it very carefully and removed all the burrs on the inside.

Also I used a 3mm bit so the hole is tiny.