So, did I strip one of my gear?

[Crunchmeister]

First, this may or may not be in the right section. I placed it in this section because it deals with a problem, but it also discusses upgrades, so if a mod feels that it's not in the right section, my apologies and feel free to move the thread.

I was shooting my Marui M4 today. I went through 2 68 round mags and a 130 round, in mixed semi-auto / auto. I decided I wanted to dump my last 130 round mag in full auto, just to see how quickly I could empty it. About halfway through the mag, the sound of auto fire was replaced by the horrible sound of grinding gears.

Note that although new, this gun had some some significant firing even though it hasn't been fielded. It's seen about 10 000 rounds to date, although I don't think that's very high since I've put about double that through my cheapo Double Eagle AK47 and it's still going strong.

The gun is a completely stock Marui M4A1 carbine. The only mod is in the foregrip to fit a 9.6V nunchuck battery instead of the 8.4V mini battery it should take. Not sure if overpowering a stock gun is the cause of the failiure or not, but I wouldn't be surprised to hear that it is. Either way, there's a problem.

I removed the motor and looked at its gears to see if they had stripped, and they appear to be in perfect condition. Reseating the motor had the same grinding gear effect. I took the gun apart and am down the the mechbox. I'm looing into the mechbox and I can see the bevel gear, and it doesn't appear stripped either. I don't have a torx screwdriver handy, so I can't get into the mechbox right now (Cdn Tire, here I come), but I'm assuming it's either the sector or spur grear.

I've done some research and after all I read, I'm left with a few questions that I think I would rather throw out to the pros, since I've never done this before. Here are my questions:

1. Short of taking my mechbox apart, is there any way I can tell what's wrong with the gun? If it isn't a gear problem, what could it be?

2. If I do open it and find stripped gears, should I replace just the stripped one, or should I replace them all? If so, what brand should I get? I see high speed gears, high torque gears, etc. I assume the high speed gears will increase ROF. Will the high torque produce a higher muzzle velocity or just be able to handle a stiffer spring?

3. If I do need to replace a gear and will have the mechbox apart, what would be some worthy internal upgrades that will increase performance (not drastically), without requiring too many other part upgrades and putting too much strain on my wallet in the process? I know about the metal bushings and will be ordering some of those for sure. I was considering a King Arms M110 spring to get in the 350 FPS range. What other not-too-costly, but necessary upgrades would I need in the gun to handle this stronger spring?

Keep in mind that I'm a noob and this is my first time disassembling an AEG. I've watched the disassembly / assembly and mechbox upgrade videos on www.mechbox.com several times now and I feel pretty comfortable doing the work myself. I'd just like some tips and pointers on the problem and what I should do about the upgrades.

[Mantelope]

Where in Kingston are you? I might be able to help at some point in the future...

[TrueTGN]

Well lets start off by saying I had the same thing happen to me with my first gun, a CA M15A4. I basically knew how to take everything apart but it was just the fact of doing it for the first time. Now option 1, you go see a gun doc and he does it all for you. Option 2, you take your time.. take the mechbox apart and learn by yourself. I didn't take any of my stuff to a gun doc because I wanted to learn how... even if it meant screwing things up. The vids on mechbox.com are great and they're what I followed for taking apart and reassembling my mechbox.

You have some stripped gears, plain and simple. The mechbox will have to come apart. When you know which gears or what gear is stripped then it'll be easier to decide on your plan of action. They're stock marui gears so you can just order a replacement for the one you need, giving that the others are still fine. If more then one you could still order 2 new gears, but i'd rather just go with a brand new set of hardened gears.

With upgrades, maybe slap a bit stronger spring in and put in some torque up gears.

If you're going to be putting in new gears and other upgrades, maybe just take it to a gun doc and see if you can watch him.

[Crunchmeister]

Thanks for the offer of help, Mantelope. I think I'll be ok for now. Like I said, the videos on mechbox.com were very helpful. I'm totally comfortable disassembling and reassembling the gun itself right now. I think the mechbox won't be too bad either with that video as guidance. Seemed simple enough, at least. But should things go awry, I may have to bribe you with beer or something and enlist your assistance for the reassembly. lol

Thanks TrueTGN. That's what I was thinking too. I was considering some reinforced gears. Am I correct to assume the high torque ones are better to handle stiffer springs? I know I don't care about the ROF. It's more than fast enough, and even if I were to lose a few rounds per second with higher torque gears, I wouldn't mind at all, especially if they're more capable of handling the stiffer KA M110 or Systema M110S spring.

Other than those issues, anything else that I NEED to upgrade in order to safely install the stiffer spring?

[beach_boy]

Ever consider that you stripped your piston instead of your gears?

[TrueTGN]

Originally Posted by beach_boy

Ever consider that you stripped your piston instead of your gears?

Haha good point, I didn't even think of that. Either way you'll be replacing something just have to take it apart and assess the damage.

[Crunchmeister]

Originally Posted by beach_boy

Ever consider that you stripped your piston instead of your gears?

Now there's the answer I was looking for. No, I hadn't considered that at all. I'm heading out to pick up my son right now and stopping by Cdn Tire on the way back for a torx screwdriver set and some krylon clear (gonna be doing the M4's furniture in OD while it's apart). I'll pick it apart and see what's up with it.

[Greylocks]

It may simply be the motor is not seated properly. That produces a grinding noise from hell.

[CDN_Stalker]

Could be the motor (if when you were shooting it the baseplate screws if loose could have shifted, not likely but still...........)

Could be your piston, if it strips you'd hear the gears spinning (whirring metallic sound) but no impact of the piston.

If the gears, it'd give a horrible grinding noise. If you replace one gear, make sure it's from the same brand and type to the gears in there. If not, get a new gear set. Stock TM gears are pretty damned good, and can be cheaper in price to the likes of Systema (and if you replace the gears with same brand/type, you shouldn't have to reshim the mechbox).

I've seen the bevel gear's smaller teeth shear off on a G&P SPR after one game (mind you, it was a 4 C-mag game for the owner) because one tooth snapped off and stuck in the spur gear (middle one) and diagnosis at the field led to shearing off all the rest. I've seen spur gears shed their teeth, and also the smaller teeth on a TM sector gear. Is really hard to say what it is. So go grab yourself a Torx #10 and let us know what you find. If yo have to replace something, PM Jugglez and he'll set you up with most of what you need (he doesn't sell patience though).

[Crunchmeister]

Just cracked open my mechbox. Seems the spur gear is the culprit. SERIOUS teeth strippage on about 1/3 of the gear.

So how does this sound for parts:

Modify High Torque Modular Gearset Marui

-built-in shims and bushings

http://www.airsoftparts.ca/store2/in...roducts_id=687

Prometheus Non-Liner MS110SP
- should give in the 385 FPS range according to the chart on mechbox.com. I don't really want to go higher than that, really. That should be more than acceptable for velocity. Anything more is probably just too powerful anyway.



http://www.airsoftparts.ca/store2/in...roducts_id=222

[CDN_Stalker]

Should be fine, the Prometheus 110 spring is a damn good spring, easy on V2 mechboxes (buy a King Arms reinforced one at the same time, cost you about $40 extra) and reinforce the whole thing! I have that 110 spring in one of my MP5s, it spits out at 365fps and I've used it all year and my stock mechbox hasn't broken yet. My MP5 SD with a PDI 150% spring went two years with a reinforced mechbox before it snapped earlier this year.

In other words, go for it, let us know how it turns out.

[Crunchmeister]

Should be a piece of cake once I get my parts in. I've fully disassembled and reassembled the mechbox 4 times how using the video as a guide the first 2 times, and 'solo' the last 2. No problems getting it together at all. Once I receive the actual parts, it should be dead simple.

[CDN_Stalker]

Dead simple is when yo ucan disassemble it and reassemble it four times and test fire it successfully after each time. THEN you got it down.............. until an issue comes up that you have to try to figure out and get baffled, more so when it baffles people on here. Then you'd have one more tool in your AEG box to use inthe future (there are dozen of possible problems that occur in mechboxes, even though I've worked on a shit load of guns the past few years, there are still things that pop up that make me scratch my head and delve deeper). As long as with each experience you learn something, you'll be a pro in no time!

[Crunchmeister]

Well, you make a good point, and that's the catch. I'm not able to test fire to see that everything is working correctly. But I have no leftover parts (always a plus) and the gears seem to move very smoothly as in the mechbox.com video. Then I reassembled and everything SEEMS to work fine, as best as I can tell without reassembling the gun.

At the very least, the mechbox is no longer a total mystery to me as it once was. I know how it works, what each part is called, what each part does, etc. And I theoretically know how to tear it apart and put it back together unassisted. Now, we all know that theory and reality can be 2 VERY different things at times. I just ordered the parts and should have them by Friday. I'll update when (and if) I get the whole thing reassembled and working again.

[CDN_Stalker]

My first attempt at upgrading a mechbox (Dec. 2004) was my TM MP5A5. Took me five nights of figuring out how to put it back together and get it working properly again. So don't feel bad if yo umake some mistakes, as long as nothing gets royally fubar'd, you have the time to do it properly.