G3 Mechbox Cycle issue
 

OK, after battering Amos and Dark Angel over TS/MSN for a good 2.5 hours we have not come to a solid solution other then possibly bad shimming, which I am sure is fine...

So here is the issue.

Up until today, the box was working fine, I opened it up to put in a new lower powered spring. Put the box back together and went to test fire and that when the fun began.

Basically what is happening is in semi mode, the gear is cycling a bit past the point where the cut off leaver engages and end up holding the nozzle back, the way the gun then continues to cycle stops the bbs from firing consistently, and has killed the air seal - otherwise - useless in semi, the ONLY MODE I USE >:(.

After numerous tests, Its been determined that the cut off leaver IS engaging and separating the contacts. The sector gear cannot be moved until the trigger is released and pulled again. but as soon as I assemble everything again it fucks up.

The pic shows where it is stopping. The nozzle and tappet plate are fully to the rear, it cannot be pushed in or be pulled out at all.

http://img146.imageshack.us/img146/5356/gearbox.png

Hopefully somebody can help me out on this :S

Have you tried putting the stronger spring back in? The motor could be overspinning in semi mode, happened to me before I install a MOSFET as my motor had so much torque it would start a new cycle when firing semi.

I have tried this, nogo, still over cycling.

I am glad I am not the only one that thought of that XD

are you using a lipo?

Hes using a 9.6

ok. so from what i understand the piston is being held back by the sector gear over rotating on each cycle, causing it to draw the piston back prematurely?

dumb question: same battery you were using before right?

Yes, same battery.

Both the piston and the tappet plate(and therefor nozzle) are being drawn back prematurity.

Sector gear shimmed to high causing binding with the tappet?? Maybe a shim was mistakingly put on the bottom side of the gear when reassembled? Does the tappet and nozzle move freely before you try to cycle the gearbox?

well thats a new one isnt it?

i wonder if the cut off lever isnt functioning fast enough. check it and the teardrop on your sector gear for wear on all contact points including the pivot of the cut off lever.

@ pokey:
i doubt thats the issue. jamming would cause under rotation. the problem here is over rotation

My guess is because you installed a lighter spring, there is less resistance so the motor will over spin. Now if you still have the same problem with the original spring, that just means your gearbox is shimmed nicely and has very little resistance. To me, having a little over spin is good as your next shot will be faster because of the precocked. Also, is the second last tooth on your piston removed?

As positive as this sounds, its is an issue because in my case the nozzle is not staying forward long enough to get a good seal and shoot the BB.

It is not.

It was just a quick spring change. The gears were not removed, bushings and shims were left in place during the whole procedure.

Though this was brought up during my trouble shooting, so I removed 1 shim from the bottom of the sector gear and spun it around a few times with some very bad grindy noises lol, so i replaced the shim and everything was smooth and quiet again.


They do.

so it seems you have a premature engagement problem. Remove the second last tooth from the end of the piston. And half of the third tooth from the same end.

Ah! fair enough, I read wrong. I does seem as though its getting too much juice though. Look into the electrics and cutoff mechanism as Finch has said.

next question - what make is the gearbox - I recall having this same issue with 4 KWA G36's this year alone already and in every case the cyllinderhead shaft had become loose and disengaged mostly but not all the way from the seating - I'd be checking that to make sure it's solid - have the same probs with alot of the cansoft M4's that KWA makes as well.

I don't believe this is the problem as AOE is good. That and if the sector gear was stooping where it is supposed to, the tappet plate would not be pulled back.

I will play around with AOE again though just to make sure.

TM

Only non TM parts are the Cylinder head, Piston head, spring and spring guide.

I'm not talking about the AOE. This is the mod http://media.photobucket.com/image/p...th_removed.jpg. Just do a better job than this person.

I knew what you meant, but when I cycle it without spring, the sector gear is catching on the correct tooth and matches up correctly.

Again, the problem is that the sector gear is progressing too far past the point where it is supposed to stop in semi, even though the disconnect lever is working properly : /

Try a 8.4v. Other than that, I can't think of anything else. Is it possible for you to take a pic of the gearbox?

I Can, are there any specific spots/level of assembly?

I wont be able to do this until late tomorrow since I'm getting to bed now and have a long day planned tomorrow.

Thanks fro the help.

Try the piston mod.

YouTube - Amos Airsoft how to: AOE and the ARS MASK kit!

We've got the exact same compression set-ups in our G3 and I needed to remove the last tooth and 1/3 of the 2nd last one.

Other than that, when I get a chance I'll talk to you on MSN, I didn't really have time to read what you were writing before.

Could it be due to the trigger contact's spring not pulling it back soon enough?

Some pics.

Shot it a few times in semi.

Position of the cut off leaver before opening.
http://img821.imageshack.us/img821/3795/imgp7370.jpg


As you can see, the nozzle/tappet plate are being held back. I cannot push it in or pull it out any more.
http://img850.imageshack.us/img850/7833/imgp7372.jpg


Immediately after opening.
The tappet plate was still being pulled back by the sector gear put i pulled it off the post to remove pressure.
You can also see that AOE is good. Gears are meshing properly.
http://img862.imageshack.us/img862/6615/imgp7375.jpg


Parts removed so you can see the position of the gears.
http://img844.imageshack.us/img844/1020/imgp7379.jpg

so this happens even when the mechbox is out of the gun correct? how good a shape are the piston head and washer in?

This happens when the mechbox is both in and out of the rifles body.

The piston/piston head have not even seen 1000 rounds yet, exelent condition.

Nobody? :(

Basically you have an over spin problem. Your setup is much stronger than the spring so, either use a weaker battery, weaker motor or stronger spring. If you don't want to change any of those things, get an ASCU.

Cobra, all those pics look normal to me. Nozzles normally are solid in place after firing at least once when you put the mechbox back together.

If this was the case, replacing the old spring would have fixed it. Moving up to a more powerful spring did not fix it either.

I would have ordered an ASCU last week if I could find any in stock in Canada >_<

None of my other AEGs preform this way though.

The way it is preforming currently is causing massive air seal and feed issues.

No, the nozzle should be able to push inwards when the piston and gears are at "Battery Position".

Nothing should EVER prevent the nozzle and tappet plate from moving back. (With exception of the nozzle and tappet plate being already pushed as far as it can go)

After single shots on any mechbox I've seen or worked on, the nozzle is rearward a bit and almost immmovable. Maybe it can spring back a few mm but that's it.

inspect the gears VERY closely.. you may have worn teeth..

The nozzle should go fully foreward. That is the purpose of the tappet plate spring. If it is not able to move, then you are doing something wrong.

The ONLY thing that moves the tappet plate away from battery is the notch on the sector gear. and it does not hold the tappet plate foreward, only pulls it back

I don't think you understand what I mean.
Oh well.

SO after replacing the gears completely, I am still having the SAME problem >_>

If anybody knows of a place that has an ASCU in stock - please tell me. I am thinking i need soemthing with active breaking, and there is no room in my rifle for a trigger master.

Not having read the whole thread, I may be repeating but I would check the spring on my selector plate to make sure it is moving the cutoff lever properly.
I would also check the tension on the screw that holds it in place. Too tight won't move enough, too loose and it may not catch. I would also check the tappet spring to make sure it's tight enough to snap the nozzle back.
And maybe the cutoff lever has been damaged.

Do you have a sector gear clip installed? Sometimes if it's in backwards, it can cause nozzle/tappet problems

Your real problem is the feeding and airseal problem focus on that not the overspin. My highspeeds overspin and the nozzel wil be half cocked but it should not interfere with feeding or airseal. Try tightening your tappet plate spring if your worried its not returning in time(if you dont know how google will show you). There should not be a feeding or airseal issue regardless of overspin.

The air seal issue is coming from the nozzle being pulled back too soon. As a result, the BB is not shot and another one cannot feed in.
I do not see any way to fix the airseal/feeding problem when the nozzle does not function properly.

Its a fixed thing if your nozzle is not sealing its your spring. The tappet pickup is a fixed thing your saying that your guns cycling so fast that your picking up the nozzle before your piston slams home?

another blindingly obvious question to put forward here for consideration and I accept it may be barking up the wrong tree - u mentioned replacing the nizzle - did u replace the original with a G3 nozzle or just a version 2 nozzle because I'm kinda sure they are different lengths - same thing with VFC SCAR H's

If you still can't figure it out or none of your methods has worked, contact a gun doctor in your area. I think venture is from the east end or ship it to me.

Nozzle was not replaced.

Sent out PM to local gundocs yesterday, awaiting replays.

I just read this whole thread jr.

I think the problem is not what you think. I think the spring swap gave you a misdirection.

When you shoot in semi, as Styrak noted, the nozzle is left pulled back. It is very common and it will spring forward into the hopup to form an airseal before the piston shoots forward again.

Therefore your problem is probably at the cylinder head or, more likely, the nozzle itself needs to be replaced.

Thank you!

Try replacing you're tappet return spring. If you do not have a replacement, heat the old one with a torch and quench it in oil, that should tighten it up. Also you might want to check if you're tappet plate is moving freely and returning all the way, make sure to add some grease on the tappet rails as well to aid in free movement.

hey jr.,

i plan to be at the game on Sunday, maybe i can explain what i mean better there.

if you shoot in full auto then eventually the nozzle should be left forward and the piston back some. then push the nozzles in toward the back. it should smoothly spring forward again about 7 or 8 mm.

It dose do this, and has since the start. The tappet plate is fine. The tappet return spring is fine.

I think you guys have the wrong idea about what is wrong with the mechbox, and this is going nowhere.

Just forget it.

I'll see you on Sunday venture, If there is time after the game we can open it up and I can show you in more detail whats going on.

EDIT

Trigger mech contacts were arcing, fixed by getting new trigger mech in there and now a V2 ASCU.

Everything is working normally, nozzle is stopping the the forward most position after every shot.