Gearbox noise - helical cut gears

[Lozart]

Can anyone tell me if helical cut gears (like SHS ones) make more noise than standard straight cut ones? I'm shimming my TM gearbox having fitted a set of SHS gears and it just seems a lot noisier even when they're shimmed.

 

[Ian_Gere]

My ICS MC-108 helical gears are quieter than flat gears in the same box, but they are the only ones I've tried and i have read other people who said that helical gears were noisier.

 

[Lozart]

Exercising my Google-Fu last night it seems that shimming is absolutely critical to getting them to run quiet. Never having shimmed a gearbox before last night I am happy to accept that I am not blessed with mastery of that particular black art just yet. What I did find though is that the bevel angle on the motor pinion didn't match the angle on the bevel gear so I think there was also some noise coming from there as I couldn't actually get the motor to mesh properly. After searching a bit, it seems that's not an uncommon issue!

Anyway, the new spring is only an M105 so I went back to the original TM gears for now. I'll change them if and when they go south.

 

[Ian_Gere]

Ahh, live and learn! Cheers for that nugget, Loz. The motor in my CYMA tac AK is an ICS Turbo 3000 so no wonder it meshes quietly with ICS gears. Pity those motor pinion gear removal tools cost a disproportional amount for what they are.

I think the trick with shimming is to keep going until it's too tight, than back off by the thinnest amount your available shims allow. I've started using copperslip between the bearing and outside shim, a drop of silicone oil in the bearing, and a smear of copperslip on the outside, to seal the oil in. I use SHS shims with the copper plated ones against each side of the gear. Apparently you're supposed to get them as far to the left as possible, but that doesn't always seem to work for me.

 

[Lozart]

Ahh, live and learn! Cheers for that nugget, Loz. The motor in my CYMA tac AK is an ICS Turbo 3000 so no wonder it meshes quietly with ICS gears. Pity those motor pinion gear removal tools cost a disproportional amount for what they are.

I think the trick with shimming is to keep going until it's too tight, than back off by the thinnest amount your available shims allow. I've started using copperslip between the bearing and outside shim, a drop of silicone oil in the bearing, and a smear of copperslip on the outside, to seal the oil in. I use SHS shims with the copper plated ones against each side of the gear. Apparently you're supposed to get them as far to the left as possible, but that doesn't always seem to work for me.

Click to shrink...

I think part of the issue is trying to do all this with the original (10+ year old) TM plastic bushings. Not sure if the gun actually warrants the extent of finding new 6mm bearings though...

 

[Ian_Gere]

Up to you mate, what gun is it?

I found 6mm Kanzen steel bearings for my ICS AKS-74U from a French site. I wanted their ceramic ones, but they were OOS and I hadn't seen them in stock anywhere for a while. I can have a look for a linky if you're interested?

In fact my google fu is strong today - this isn't the site i bought from but it has them. I forget but the site I bought from was called something like Monde de les roulements.

Aha! Universe, pas de Monde lul! Plus de les Euro, mais avec le free shipping aussi...

 

[Lozart]

It's kind of like triggers broom now! Started life as a bog stock TM M4A1 (old one - about 10 years old - so no recoil or that fancy shiznit) and it was getting pretty tired. Bought an SHS upgrade kit (nozzle, piston head, cylinder head, spring guide and gears) because it was cheaper than getting the bits separately. I reckon the only TM bits left on it are now the front sight, the gearbox shell, buffer tube and pistol grip. It's basically become my "learn how airsoft guns work" test bed (now that I've got other and indeed better primaries).

Thanks for the links though bud, I'll check them out. I did find 6mm G&G bearings at LWA too. Are they any good?

Screw it, bought the Kanzen ones. Cheers buddy!