Shimming!

[jagillham]

First off, these are the little washer type things between the gears, and the bearing inbedded in the GB casing?

Can someone explain to me the process of correctly shimming the gears?

It looks easy, but it seems lots of people get it wrong and break the GB. So I guess there is some kind of skill to it?

Basically I have 2 GB's I've opened, and want to check it is all there.

First, Systema Reinforced GB. 7mm brushings.

Second, CA, v3 GB from G36.

On both I need to know the size shims, and how many and where.

Cheers,

James

[woottonp]

Re: Shimming!

i would also love to know a bit on shimming, as i understand the different sizes and that but i do not understand the process to get the gears shimmed correctly

paul

[magic_golem]

Re: Shimming!

shimming is really,really simple it just takes some time and care every gearbox ive worked on that needed a good shim ran a lil faster but by far the biggest differece was the sound,my old m16 made half the noise it did after a good shim job, i have a link to a guide i read a while ago somewhere...........will look on my laptop for it.
basically shimming the gears correctly allows each individual gear to rotate with minimal resistance on the axles (which is what the bushings or bearing depending on what you have are in contact with).and by using shims to adjust the height of each gear in relation to each other you want them to have as much 'bite' with each other as possible 'teeth wise' but not touch anything else.
its kinda like a 3d jigsaw a bit.
as for how many and where their isnt really a hard rule for that as no two gears are 100%exactly the same they can be close though.

The main pitfall alot of people do when shimming is put waay too many in which puts pressure on the gearbox case and can mis-mesh with the {sector?} gear wich results in the piston teeth taking all the load down one side and stripping.

i was wondering if i could make money charging for shimming unsa up as i have done quite a few...any ideas?

Ah i found it the site doesnt just cover shimming but most aspects of gearbox work too its not part of a retail site so it should be ok to link it here

enjoy :P
http://pageproducer.arczip.com/daedalus03/workshop.html

[dope_on_a_rope]

Re: Shimming!

basically shimming the gears correctly allows each individual gear to rotate with minimal resistance on the axles (which is what the bushings or bearing depending on what you have are in contact with).and by using shims to adjust the height of each gear in relation to each other you want them to have as much 'bite' with each other as possible 'teeth wise' but not touch anything else.

Also to stop the gears from moving laterally. Lateral movement causes noise.

It's important to note, when checking to see if you've got the right amount of shims on a gear, you should fully tighten the gearbox case. To the same point where you would tighten them for use. Why, should be obvious.

I start by making sure the spur gear, has the right thickness of shims on it. Then taking that out, I move onto the sector gear, then the bevel gear. Now you know how much thickness you have to play with. The next step is getting the gear to gear engagement happy. So I continue by putting the spur gear back in, with one or 2 shims below the spur gear, then sitting the sector gear in, and shimming it upwards until it engages as it should. Every time I put a new shim in, I check the engagement by closing the gearbox and giving them a spin, then visually inspecting the gap between them. Take as long as you like, to get it as good as you can. It's your gun, surely it matters. I don't shim for other people unless they pay me. Even then it's a pain and I don't do it as well, as I do my own shim jobs.
After that, move onto the bevel gear. You might need to play with the shims on the other gears again, if you find that you can't get the engagement between the spur and bevel right. That pretty much adds another 10 min to an annoying job. It's tedious.

As an aside, something that is often missed is movement of the AR-latch. Shimming the AR-latch can often stop it from wobbling as much, and make the gearbox quite a bit quieter. I tend to grease them up heavy as well.

[Peanut]

Re: Shimming!

That's very useful thanks.

Where does one buy these various shims from?

Thanks

[magic_golem]

Re: Shimming!

they typically come in a pack with a few of each size, alot of airsoft sites sell them, also an aution site....

[jagillham]

Re: Shimming!

they typically come in a pack with a few of each size, alot of airsoft sites sell them, also an aution site....

How do you know what size you need?

[jagillham]

Re: Shimming!

Anybody??? I need to know soon

[kalashnikov_kid]

Re: Shimming!

Buy a selection of sizes from 0.1mm - 0.3mm and use them as needed.

K_K

[jagillham]

Re: Shimming!

I thought they came in lengh's, so your saying just widths?

[dope_on_a_rope]

Re: Shimming!

They all fit around the axle. Some are bigger in diameter than others. That's just to make them easier to distinguish.

[magic_golem]

Re: Shimming!

aye they come in a range of thicknesses for different heights needed,