AEG fires at random
 

okay so i finally got my gun rebuilt the other week and took it out to a game last week it was a lil chilly so the hop up wasnt working so i didnt use it. However the other day i was going to plink with it to make sure the hop worked in warmer weather it shot okay for a while then it randomly shot without the trigger being pulled.
Then it would shoot going from safe to semi then wouldnt work with the trigger pulled but would agin going from safe to semi on its own.
Its a v2 lonex shell with a merf3.2 with a 2 signal wire setup.
When i first built it i noticed the wires became a lil pinched from the small exit hole in the back and from some pin on the top of the shell that sticks into the wire channel so i filed those bits down to avoid damage to the wires but i think there was alrdy some damage done. Is this likely a short in the wires causing this?

Entirely possible and highly probable.

Tear down the gun and inspect all your wiring. Your trigger wires are probably shorting each other somewhere. Those trigger wires are also fragile as hell so you should be wrapping them in heatshrink wherever possible.

I figured as much. New issue. Now WTF did i do. I opened it up to check out the wires. (they do look okay save for a few knics on the motor wires i think it may be just the sure tightness of the space to run all those wires through)
Befor i opened it it worked fine no issues with firing on its own and the 3round burst was right on time. (still no semi as some of you may alrdy know)
So to my supprise i found this work of beauty inside when i opened her up.
http://i197.photobucket.com/albums/a...425_150945.jpg
http://i197.photobucket.com/albums/a...425_151006.jpg
The shim job is sweet you can see the sector was runnin right down the middle.

The aoe should have been fine you can see where the lil tab sticks up on the sector that is about where it is set to.
You can see the last three orange teeth and its hard to see but the metal tooth is also busted off in there tho its still just barely held in by the plastic.
So WTH causes this?
Its onlly a stock echo1 spring 380-400 fps or so its lonex hs gears (16:1 i think they are) stock motor 9.6v battery so not a crazy fast build. In fact i didnt even have to change the timing from the stock setup for the 3rnd burst.
Do i just have that bad luck or suck that bad at rebuilding or what gives.

If your metal tooth failed then the rest of the teeth are going to shear. Plastic is not meant to hold loads like that. Typically multi-metal tooth pistons save you in that department.

Get a new (better) piston.

What the heck is that orange thing anyway?

As a tip, the 1-wire method of wiring the MERF is preferred as it makes for less wiring to snake through. There is no performance degradation. You'll run into pinches if you do the 2-wire method, unless you clear the proper path for the wires.

im no gun doctor but def looks like your last tooth failed and the gear just grinded down your piston teeth. Why its shooting randomly I have no idea

So one of them lonex high strength pistons (like half the teeth are metal)
Guess i change out the piston head for an aluminium one while im in there.and ima try i different cutoff lever and trigger assembly hopefully solve my semi issue too so when i put the new trigger switch ill wire it up the one wire way to avoid the random shooting lol.
Well its official i shoulda just bought the lonex complete box snd dropped it in.
Lesson learned lol.

release tooth failure = goodbye plastic rack piston.

at least you got a chance to discover the piston issue while investigating another issue.


shs metal rack15 tooth , file down the 1st regular sized tooth and half the 2nd... get the lonex pom piston head.

1) SHS 15T or Lonex Red is fine.
2) Get the POM head, aluminum heads are useless, remove bearings from piston head
3) Try playing around with the trigger prongs and sled with a multi-meter and see where it "trips" the cut-off lever.

Scratch-building boxes isn't for everyone... seems easy, but tuning is crucial.

If you still have the electronic safety (the metal plate on the selector), it can short on the body.
That coupled with a pinched wire can make your gun shoot on it's own.

A dead MOSFET will also burn shorted (closed) and will cause the gun to enter a full-auto madness.

As for your piston, it looks like the plastic around the metal teeth bent a bit/have some play and allowed the gear to skip on the plastic tooth.

Looks like you need a piston with 3 metal teeth lol
And +1 to what Kos said. Only takes one bare trigger wire to cause the loop to close and the gun to shoot.

POM for piston head
and Aluminum for cylinder head

Yeah i think i actually can do it just i should have used good parts not reused the crappy echo1 parts (that orange thing is the echo1 stock piston)
Okay so ill grab the modify polycarb head remove the bearing the lonex red piston and a ka low resistance trigger setup and just run the 1 wire method to avoid the squishing of the wires. And a new cutoff lever as that is what is causing my no semi issue. If i run it by hand i can get the cutoff to disconect the trigger switch but it barely catches it and i have to push dosn on the trigger switch a lil and the cutoff lever has to be super loose.
Obviously as all you gundocs prolly know the echo1 parts work okay in an echo1 shell but fail horribly in another shell.
Thanks all for the help. This time for sure lol

What? No, don't get a polycarb head.
Polycarbonate != POM
POM = Polyoxymethylene

Polycarbonate is far more brittle compared to POM, and POM is actually the material real steel M16 stocks are made of.

2 totally different things.

$17.00
Polyoxymethylene (POM) piston head made by Lonex with ball-bearings.

Polyoxymethylene is a low-wearing, low-friction, high-strength and lightweight plastic. Its properties make it an excellent material for a piston head. Other manufacturers use polycarbonate, which is also lightweight and high-strength, but is extremely brittle and will shatter leading to catastrophic failures.

It's also super fun to machine and makes a wicked mess :D

No polycarb okay lol.
So what is that whits/beige stuff the stock head is made of polycarb or some other crappy stuff?
Ihave a sorbo installed so i dont think itll break anytime soon.
Also i may as well ask why remove the bearing doesnt it help reduce the stress caused by the twisting action of the spring or is the bearing spring guide enough for tha?

simple way to tell polycarbonate from POM... is it clear?

yes = poly carbonate.

no = another material, probably more suited to use in shear force conditions.

polycarb is terrifically strong... in 1 direction. you can hit it and it could probably take a lot of impacts before breaking, but you can't pull it or twist it, it shears a whole lot faster.

Theres tons of polymer blends being used in pistons... yours could be straight nylon, could be nylon reinforced with fiber, could be a few other materials too.

Piston head bearings are redundant if you have a BSG.

You want to reduce the overall weight of the piston assembly as much as possible - just more efficient that way.

Tip: For even higher ROF, don't use the bearings that come with this piston head. Instead, use a bearing spring guide only as it takes the weight off the piston assembly.

Lol this info keeps coming from the site ill be buying my internals from once i get some moneys
So backing stealth up each time
grabbing an aluminim cylinderhead
POM piston head
Sorbo
Aluminum nozzle with oring


EDIT............ That would be stealths store......

You haven't seen a mess until you create a Brass milling snow storm! :D

I wish I had a camera that time

(The guy standing behind me didn't like it one bit)

I used to have some great videos of dry milling A514 and a semi-complex 6061 piece out of a 6x4x9 square billet but I had to take them off youtube and I didn't save them anywhere X_X
Such a shame, I used to make such beautiful handwritten G-code too :(

would the madbull px piston be a good option? it already is missing the second tooth (for better engagement) and all the teeth are metal...

I find buying a piston with a full set of teeth id better... Some AOEs require only 1 tooth shaved others require 1 1/2 to 2

Airsoft Store Canada

We do product testing so you don't have to.

DON'T USE POLYCARBONATE PISTONS

http://i.imgur.com/fgKMRYe.jpg

guess I got lucky, it worked perfect with my setup...

BAM!!!!

God this pictures gunna give me nightmares

On a side note. is there anything that can be "Macgyvered" when the trigger trolly slides back past the trigger on every trigger pull, before making the electrical connection? is this problem caused by a bad cutoff lever or is it the switch assembly that needs replacing? I've glued a small piece on the back side of the trolly so the trigger has more to grab on to, but I'm sure someone with more experience will have a better idea.

P.S I know I know, just buy a new cut off/ switch assembly...

You can put a small screw in the bottom of the trigger switch. No semi tho

ya, I have no semi with the piece glued there. while the glue is holding for now, when it breaks I'll use a screw... if i don't have replacement parts by then...
Thanks Hectic, While your posts are sometimes a difficult read, you sure are helpfull :)

I try to be lol.
Been workin on at least breakin my posts down into paragraphs so folks can read em without their heads exploding lol.
Im a little beter on the computer but on the phone (most of the time im just usin my phone) i ramble on and on lol.
You gave me another line to add to my sig thanks lol.

I have fixed a friend's with a smalish laptop screw, placed near the rear/lower edge from under, then filed the part of the head that was extending past the rear edge. Still Semi with that, as the head of the screw is about 1/2mm.

full metal rack on an AEG is a bad idea. The steel they use is too brittle to absorb constant impact

That's why it's recommended to epoxy the rack to the body. Short of the pistons binding to the rails, I've had very good experiences with SHS full tooth pistons.

Ummm... Hectic... how come no one noticed before, but how are you correcting for AoE without shaving the 2nd tooth?

John

haha good catch
but he mentioned something about the AOE being correct already, so i know i didnt even look after i read that... still wouldnt cause this problem, but would def help ur gearbox by shaving down atleast the first tooth

You know, we went years without shaving the 2nd tooth off any pistons and some of them lasted a really long time lol

if he has a Sorbo pad on the cylinder head, AOE would have to be adjusted.

im still learning.. so i cant think straight without taking my gun apart and looking at my AoE. mine is set up fine ive shaved the first tooth off mine and some of the second, this is without a sorbo.. What would happen to him if his gear tooth catches the piston too early by hitting the first tooth or the second?

Would it cause the piston to launch forward with a gear tooth still in the way?

Coach got it. The sorbo pad seemed go have it perfect. When i spin the sector by hand with out a spring or guide in the first tooth on the gear lined up with the tooth on the piston perfectly didnt seem to want to half catch or skip over to the seccond tooth or anything.
As far as i knew the sorbo and or a shaved tooth of two wer ways to correct the aoe and that you didnt always have to shave a tooth if it all lined up good good so i didnt see a need to shave it.
In hind sight looking at the piston the pickup tooth and the ones close to it look nearly new so id say the engagement was good

Just because the first few teeth, where the gear grabs, are in good shape, doesn't necessarily mean your AOE is good. Theres not enough force or speed to rip at the plastic tooth at the beginning or "engagement."

Correcting AoE with 70D Sorbo for Airsoft Aeg - YouTube
this guy has a great vid for checking your AOE

As far as i can tell you dont really need to shave teeth unless your going higer speed (like 13:1 gears on a high speed motor or runnin 11.1 lipos)
The shaving of the teeth alows the sector to grab the picup tooth then the tension of the spring increases slowimg the rotation a bit then the sector can cleanly grab the seccond or third tooth (depending what you shave)
When the sector is spinnjng real fast as it grabs the picup tooth it wants to spin faster thdn the piston is moving back so the seccond tooth on the gear will want to grab the seccond (first regular) tooth on the piston too soon and winds up chewin the heck out of it.
I think personnaly in most cases the teeth will wear out if the aoe isnt good and the issue will sort of work itself out( only downside will be the bits of plastic in the gearbox)
Im surs the gurus will chime in but thats my baisic understanding of it.
The sorbo pad brings the piston back a bit aligning the picup tooth and first tooth of the sector and sort of preloading the spring a lil so the stuff will all move at the same sort of speed.
Im sure if i threw a 11.1 jn my gun j may have to shave a tooth (or it would shave itself ) but on a 9.6 with the sorbo it was perfect.

Only one explanation.

Your AEG has become self-aware. O.O

The purpose for adjusting for AOE is so that the first tooth of the sector gear meshes with, and only with, the first tooth on the piston.

SO, if the first tooth of the sector gear touches or drags the second tooth on the piston and/or the second tooth of the sector gear on the third tooth on the piston before the first tooth mates with the first tooth on the piston, pull out the dremel.

Hectic, I think your piston is releasing early and the wear is from dragging along the last tooth on the sector gear. You're lucky you don't have more metal teeth on the piston or you may have pouched your sector gear. Check your AOE again and ensure the sector gear is not engaging the second tooth on the piston.

HAHA yes if this is the problem i feel super smart. This is why i asked that question. I watched vids and paused to figure it out and yes if your gear picks the piston up from the first or second tooth instead of the BIG TOOTH, then itll release your piston too early and your whole piston will now grind away along the last tooth of ur gear

Coach does have it

When I say first tooth on piston, I am referring to big tooth or how you put as pickup tooth.

Ok i gotta get this straight then lol
First tooth means engagement tooth

so shave the second and third

Yeah. The first actual full tooth is what people refer to as the second tooth that you grind off. But sometimes it's also the first tooth.

Confused yet? Can I make it worse for you? ;)

haha i understand. i got it right, just the numbering of the teeth i didnt have right
now when im refering to shaving the fist tooth off, its actually the second lol i probably confused people

Like i said Hectic watch that youtube video, you can sckip most parts until he gets to the piston part

I alrdy got it all tore apart. Tommorow ill pester jugglez and grab some parts and check everything again befor i reassemble.
Yeha i seen that video. Thats what i was sayin the first tooth on the sector has to grab the first/big/pickup/engagement tooth (we need a standard name for this tooth lol) cleanly and meshes with the rest of the teeth without tryin to chew em up or grab em ahead of time.

Is it just me or this alrdy has at least one tooth shaved?
http://www.airsoftparts.ca/store2/im...on-10teeth.jpg

yes some pistons come like that

The standard name for that tooth IS the pickup tooth.

It seems like the general consensus is an AoE issue. So how does damage like that happen without any sign of wear on the pickup tooth, 2nd tooth or release tooth? The release tooth looks perfectly fine, a release tooth failure results in stripping of the entire piston rack not just damage to the front few.

http://imageshack.us/a/img28/3532/img00411k.jpg

I've seen similar damage but to a much lesser extent on one of my Modify pistons. The gun still worked fine, but it was caused by a worn out bushing, so make sure your bushings are perfect.

I actually figure that the stripped piston is a result of the last tooth (the metal one at the head end of the piston) failed. It looks in tact in the pic i posted and it actually is but it is broken off of the rack and if you put pressure on it it will lay out almost flat and press into the piston allowing the piston to slip forward befor the sector is finished its cycle so the last tooth of the sector would drag along the piston a bit stripping those gears.
Aoe was good piston, not so much lol
Edit if you look closely at the front of the metal tooth you can see the crack and if you wher to push on the metal tooth it wobbles and will lay out flat if pushed towards the other teeth
http://i197.photobucket.com/albums/a...425_150945.jpg

your piston crapped out on you... :( sucks but buy a new one and youll be alright. Lonex?

I guess it just wasn't clear in the image.

You should do well with a Lonex piston. I have one in one of my guns, but what really impresses me is my Modify Quantum Piston in my DMR, it's been in there for almost a year and the piston still looks pretty much brand new if I clean off the gear grease. Don't use this piston unless you have a high quality gearset, the reason the piston still looked new was because the titanium coated steel teeth were harder than my gears and very slowly wearing away at the pickup tooth on the sector gear.

WoW, That's the first time I seen a piston fail there.

May I ask what spring your pushing.
I think some time's people expect to much from stock part's.
Not pointing any fingers.

Hectic, you've got smoking-gun evidence of PE, so don't let yourself get distracted by the discussion around weak pistons and AoE. You need a strong piston, you need to correct AoE, but the reason your orange piston failed was because you've had PE (pre-engagement).

The reason for PE in your case could be anything, but it can be caused by too weak of a spring, a heavy piston, or a piston that had trouble moving along the rails. You might have also had a BB jam in your hopup chamber and you kept firing full auto (if your gun was a little off its rocker, this could have easily happened).

All of those things can cause PE. In your next refresh of this build, solve AoE, get a strong piston, but make sure you've prevented pre-engagement. If you put in a slightly stronger spring but steal away volume using a sorbo pad (which you'll need for AoE anyway), you can neatly tie up both of these problems with a single solution.

+1 on the lonex red pistons. Don't forget to check that yours moves up and down the gearbox nice and easy!.

Also Hectic, Stealth, let's all chat about this at Finch's on Sunday ;)

Alright you might be taking me to school on this, but a sign of PE would have the piston wear/damage near the rear of the piston, not the front near the release tooth.

My money is on piston getting stuck on rails.

I don't possibly see how AoE is corrected without removing a second tooth. It's just impossible. That being said, notice how there's very little damage to the second tooth?

In this scenario, the sector would try to pull back the pick-up. It would jam into the second tooth, slip, and attempt the entire pullback process.

Piston makes it almost to the end before it gets stuck. The gears power through it all. Notice how the front is stressed to hell.

Piston is released but gets stuck or slows at the very same position.

The sector gear is coming around again for a second pull-back. Instead of engaging at the at the first tooth, it starts pulling back somewhere at the position of the shredded teeth. Cycle repeats.

This would have been super evident with a chrony. If you're doing gun doc work, get one.

TL;DR: Piston gets stuck. Hectic somehow short strokes his system.

John

No damage at all on the rear teeth of the piston just some lil bits of loose cral there. The seccond from the front is actually sheered right off just like the next ones are. For the heck of it i practiced shaving teeth on the old piston so it looks like hell now at the back but im sure what happened was the metal tooth failed causing the piston to slip forward one tooth and as the sector was still tryin to complete the cycle the piston was trying to start its forward jurney thus causing the damage you see. The aoe wasnt "corrected" really it was just alrdy lined up nicely so i didnt see any need to shave the teeth.
In hind sight the day i tryed to game it it was coold and i did get a jam or two and during one i got 3x3round bursts try to go off on their own so that likely is what killed that first tooth.
Hopefully ill have it running for sunday but ill bring that old piston so you can see what i mean about the metal tooth.

As for spring its the stock echo1 spring (useually they run the stock piston for quite a while)
Just my bad luck on this gun after i get this one running ima stick to external adons and gbb's me and gesrboxes seem to not get along sometimes lol.

Wtf mate. Is everyone going to this game on sunday?

Oh yes.

All the cool kids are gonna be there lol

Wondering if the second tooth ended up acting as a pickup tooth...? If it did, that would have broke the last steel tooth... So perfectly timed PE on the 2nd tooth.....

If my tax refund magically came in today id go :(

Thats why i do mine right at ghe end of january and get direct deposite. Then i can get it fast (and spend it faster lol)

To me...

Looks like the gear slipped off the last (metal) tooth and raked the plastic teeth.

1. A crappy piston that let the last tooth flex/break out of position, allowing the gear to rake the plastic teeth is possible. That would be a piston failure.

2. If it was cycling way too fast...the sector gear came around and picked up the piston on the 2/3/4'th tooth, the piston would jam back and then the last tooth would break or slip out of positon and the gear would rake the teeth as in the pic. That'd be early engagement.

3. If the piston was getting hung up on the rails, it could result in early engagement and break/strip things as you described. But I find it a bit unlikely as it did shoot/cycle a number of times and 3 shot bursts before it failed (unless it sounded like a grinder for those shots).

It didn't sound like there were that many shots before failure...but there doesn't seem to be any wear/tear on the first tooth (pickup) or second.

I choose #1 lol. Looks to me thats exactly what happened the last tooth (the metal one) broke for whatever reason (likely just cause it sucked) and the way it broke it is still in the piston but can wiggle and lay down almost flat when there is pressure put on from the front side thus allowing ylthe piston to slip forward one tooth. When it slips there is only one or two plastic teeth tryin to hold back the 400ish fps spring thus causing the teeth to fail just as the sector is finnishing its cycle so it was only enough sector to piston contact time to strip those few teeth as opposed to the whole piston.

Ive been running the stock cylender (4/5 port) with a 455mm inner.
Im going to be putting a thicker sorbo pad so now ill likely be running short on cylender volume for the barrel. You think i should swap in a full cylender to combat this?
Was looking at the modify enhanced cylender for 450-590 inners thatll leave me room to put in a longer inner for my dmr build that im going for with this gun.
http://www.airsoftparts.ca/store2/im...linder-aeg.JPG

The thickness of a sorbo pad really won't change your cylinder volume THAT much, as long as you're removing the stock pad and only adding enough to correct AoE. You're only losing the slightest bit, translating to maybe 20 or 30 mm of barrel length which is nothing.

Hectic is like a woman after menopause... no periods

John has said that - and I quote - "I refuse to read Hectic's posts. It hurts my head".

He also needs to turn on the spell check on his smart phone.

BUT, his posts are at the stage where I am too lazy to be the grammar/spelling Nazi.

Just do what I do, skim! Then wait for someone else to read it and post. Then read their reply before you post referencing his thread title. Hahaha!

I put a ruler on my screen so I dont read the same line twice.

Very effective, except you look like an dumbass who's trying to get the length of is computer screen at work... You should try it!!

Lmfao! good stuff. Hectic I'm laughing with you, not at you. I swear!!!

This has degenerated into a chat thread.

I use the modify enhanced cylinder as well, a good choice. A balanced gearbox is a happy gearbox.

This may help http://arniesairsoft.co.uk/?filnavn=...andbarrels.htm go for the best match.

Just watch out when you start mixing different brand part's. I use the goldilocks rule.

Thanks. Yeah im well aware of matching cylender to barrel. Every gun i buy first thing i do is check the cylender and buy an inner to maximize effeciency.useually 430 or 455 in m4's my two current ones are 455 i figured sdding sorbo and havin an inner that was alrdy at the max volume wasnt good so i went to the non ported cylender. Now i can go longer inner for a dmr build (prolly go 510mm)
Well after working out a trigger bug (the switch was sticking cause the prongs wer too tight)
Ive got a working gun even got semi!!
Now to see if it holds up. Gonna have the gurus take a listen to it on sunday. Sounds good to my untrained ear at any rate.

All i gotta say about my spelling and grammer and punctuation..
For those of you with kids let them read my shit and tell em "see kids this is why you should stay in school" lmao.
Seriously tho i dropped out in grade 9 and from grade 7 on i was hardly ever at school they just kept pushing me ahead cause i could pass the tests just never did any of the homework.
Was good at math science music and technical classes sucked at geography history and english. (go figure its my first and only language and i masacre it lol)

I had the hardest time matching my air-seal to my barrel length. I ended up with a custom cut 3.04 bore 404mm barrel just to get the right spit of the BB.

Must be a 3/4 port with a sorbo and maybe short stroked?
Mostly if you use the arnies list as a reference you can go close to whatever the largest is for your cylender and get maximum fps out of a setup snd decent consistancy. But for the most part 300-400mm is ideal length (is a lilconflicting as there hasnt been alot of testing)
I personally have always had good results with 4/5 cylenders running 455mm inners but now i got the full cylender so ill up it to a 509 one of these days.

OOps my mistake it's a 4/5 Hole Cylinder, 3.04 bore 404mm barrel

With my mix of part's & the kind of air-seal it gave me I had to find that sweet spot when the stork of the pistons air presser ends a split second after the BB leaves the barrel. I judged it by hearing it make a spit sound to put it to a better term.

I had many say that I had a very quiet running gun but to me it sounds like a sowing machine in my ear.