Gearbox smoothness?

[Ace]

Hey all!

I have no idea how this rifle sounded the way it did, but I was a bit dribbly afterwards...

I was at Urban Assault the other week, and there was a chap using an M4 that sounded NOTHING like I've ever heard before. There was next to no noise coming from the gearbox, it sounded so smooth and fast, as if there was no friction or resistance. I was just wondering if anyone has any information on how you can get a rifle gearbox to run smoothly and sound as perfect as this one did? - I was about to ask him as I was shot. Bad times.

I've read up a bit about a couple of things to do but nothing has sprung out at me. Could anyone also explain what "Shimmying" or whatever it's called does and how it's done? That'd be great!

Thanks y'all! :D

[The Keeper of Secrets]

Re: Gearbox smoothness?

One word: shimming.

Ok, it's not just that. But a good shim will go a long way to making your gearbox run smoothly. Personally that's what I go after when I do work on my own rifles. A smooth, healthy, purring thud comes before ROF or range or FPS or anything like that (although a healthy gearbox will give better performance overall than a screechy grinder). It's something that irritaes me with 'techies' who pust highspeed parts into their guns with a highspeed motor, don't shim it, and are left with a gearbox that makes the most horrendous noise.

Another big thing is motor height adjustment, which in a way is the same idea as shimming.

It's something that requires time and experience. If you're looing to get into tech work, find yourself an old gun that you don't mind if it goes wrong and work on it. Just get to know how the different parts work together A mechanical mind helps here.

If you feel like it, shoot me a PM and I'll be more than happy to talk you through the basics of getting a nice noise from your gearbox.

[B.E.N.]

Re: Gearbox smoothness?

It starts from the ground up I find...

Best thing to do, in my eyes:

Make sure you have a clean, tidy and comfortable workspace, all your tools at hand, well lit etc.

Give yourself PLENTY of time.

Take your time and be meticulous, make the effort to understand how each component interacts with others.

Clean and re lubricate all the moving parts, don't over-torque any screws and as above take time to ensure the shimming and motor height is bang on...


You're never going to get good results with shoddy tools, a wonky workbench and a rushed job.

[Ace]

Re: Gearbox smoothness?

So shimming if effectively positioning the gear perfectly to interact with one another as accurately as possible? Assuming this, do you require things such as washers (example) to position and realign the gears? Or have I got the wrong end of the stick something serious here?

[Ace]

Re: Gearbox smoothness?

The ROF was incredible but this doesn't interest me so much - simple to upgrade a ROF from what I've seen, just spend some money! Whereas having a sexy sounding kit...

[Bluegill]

Re: Gearbox smoothness?

So shimming if effectively positioning the gear perfectly to interact with one another as accurately as possible? Assuming this, do you require things such as washers (example) to position and realign the gears? Or have I got the wrong end of the stick something serious here?

You're pretty much spot on! The washers you refer to are indeed the shims (hence the shimming) and they are placed on the gear axles to assist you in gear alignment.

[The Keeper of Secrets]

Re: Gearbox smoothness?

Bang on really. The shims themselves are the washers and you can buy packs of them for a good price on ZeroOne.

They position the gears to mesh together as you said. Too close and the faces rub together, too far and you don't get enough tooth engagement. There are other factors as well, such as the sector gear tappet nub having to be spaced far enough away from the tappet plate rails. You also have to close and screw the geabox together after every adjustment to make sure you've not shimmed them too tight.

At the end of a good shim you'll be able to splin the gears with your fingers and they'll keep going for a while. They also shouldn't wobble or slide side-to-side on the shafts.

That's the basics of it. You just have to spend a long time playing around with it and seeing what works best. Personally I really enjoy shimming gearboxes.

[Ace]

Re: Gearbox smoothness?

That's great info, thanks guys!
I'm not terribly gearbox literate, but I'm getting to grips with it - mainly via my friend who has quite an understanding! It's something I will fo'sho look into! Is there any other info? I hear you also don't want too much grease on the inside?

[The Keeper of Secrets]

Re: Gearbox smoothness?

Again it's an experience thing with the grease. Too little is very bad but don't lather it in the stuff.

[sparrowhawk]

Re: Gearbox smoothness?

in my experience,i dont close AND screw the gearbox together,i take the piston,spring cylinder etc out, basically leave just the gears in (and possibly the anti reversal latch)and work on them, shim the gears and hold the two halfs of the GB together with one hand,you can then hold it up, check for perfect alignment with the spare hand, spin the gears through the cylinder hole, or up through the motor hole, turn over the GB several times so you can listen to them sliding about on their axis(slight rattle)...just keep doing this until it looks,sounds or seems satisfactory...make sure you take note of what shims have gone where, generally there are 3 thicknesses of shims...maybe theres more...but its just a trial and error to find the right combination, once its running ok, and you have a note of which shims go where,then you can put the rest of the parts in

[guard-sniper87]

Re: Gearbox smoothness?

actually,

first thing is first, what was the other guy using, what make gun, this would help to know,

as if it was a SYSTEMA PTW you will not get the same sound due to the weapons design and function...

but if was a normal AEG like CA M4, or VFC Scar-L etc then have a look on youtube and on the tech section on here as there are loads of guide on how to shim a gearbox properly

in turn the properly shimmed gearbox will run smoother and more effecient, with no movement from the gears ie side to side play making more un-needed movement and vibration, make the gearbox sound smoother and run in some cases alot quicker after a proper regrease and motor height adjustments..

there are many shim packs on the market, best pack by far is the systema packs of shimms followed closely by the CA shim pack

[The Keeper of Secrets]

Re: Gearbox smoothness?

in my experience,i dont close AND screw the gearbox together,i take the piston,spring cylinder etc out, basically leave just the gears in (and possibly the anti reversal latch)and work on them, shim the gears and hold the two halfs of the GB together with one hand,you can then hold it up, check for perfect alignment with the spare hand, spin the gears through the cylinder hole, or up through the motor hole, turn over the GB several times so you can listen to them sliding about on their axis(slight rattle)...just keep doing this until it looks,sounds or seems satisfactory...make sure you take note of what shims have gone where, generally there are 3 thicknesses of shims...maybe theres more...but its just a trial and error to find the right combination, once its running ok, and you have a note of which shims go where,then you can put the rest of the parts in

Yes,you take the other parts out first in order to have a look at the gears.But you MUST make sure you screw the casing together every time you change something. You can't hold it as tight as the screws can and it does make a difference.

[B.E.N.]

Re: Gearbox smoothness?

actually,

first thing is first, what was the other guy using, what make gun, this would help to know,

as if it was a SYSTEMA PTW you will not get the same sound due to the weapons design and function...

First time I heard a systema I thought somebody had caught a cat in it!

[guard-sniper87]

Re: Gearbox smoothness?

First time I heard a systema I thought somebody had caught a cat in it!

yeah the chirp though is sooooo nice, it scares people when i use it at my site with soundpig on :p

[B.E.N.]

Re: Gearbox smoothness?

yeah the chirp though is sooooo nice, it scares people when i use it at my site with soundpig on :p

It's the proper pistol grip and furniture that gets me... Stock and buffer tube and that.

I got one in to photograph the other week (a CQB-R), and I didn't dare fit a battery and have a whirl, because it would have pushed me over the edge and been tantamount to spending the money there and then.