Got some overspin going on, need some tech savages to help me out. [Pics of gearbox inside as well as parts list and description]

[Keldri]

I have already short stroked the gear and piston, two teeth on the gear and two on the piston, as well as swiss cheesed. My idea is that i need a stronger spring, but i have a site limit on 350fps on .20g bbs.

Gearbox:
http://imgur.com/bk88ojo
http://imgur.com/72HOvXY

Does anyone have any good ideas?

List of upgrades i did so far:

ZCI piston head silent

SHS M4 cylinder head double o-ring

SHS M4 aluminum nozzle

SHS 12:1 ultra high speed gears

SHS 7-tooth piston

SHS plastic Gear Delayer

SHS shim set

SHS 110 spring

Airlab Sorbothane Pad for AOE

8mm Bearings

Nuprol HIGH TORQUE MOTOR

PS. if anyone know where i can get my hands on a btc spectre, throw some information my way!

[Sitting Duck]

Please tell me 2 things:

 

You are NOT trying 11.1v

 

That box is NOT a G&G blowback box

It looks like it and if so you may as well cut off the front of box now with hacksaw

 

You still using stock wire no fet

No bearing spring guide but....

 

Oh rather than pull it apart....

What battery, think you gotta stick on 7.4v coz 11.1v will over spin. Though a 10mm spacer n bearing spring guide could be used instead if m120

It will be about same...

 

Bearings also are adding say 2rps or more to rof which might be OK on lower 7.4v 20c but higher juice/burst she will spin over or double fire

 

Gis a bit more info...

 

I'm at work but you gotta go easy and if that is a G&G blowback you can't push blowback's too much...

They crack up or bits break off - or both at once

 

Think it is case of going too nutz too quickly

[Sitting Duck]

Soz you gotta fet In there

But stock wire all the same

 

You can't go nuts on 11.1v and if blowback you can't shortstroke too much if you still want blowback coz it needs more volume for be blowback

(Well you have lost blowback with new cylinder head unless you drilled that new head but the box is still weaker than a normal non-blowback box)

Plus it is weaker at front that is why they can crack easily if going mental or pushing mp5's with a slightly higher spring on shorter barrels....

Google up cracked G&G blowback boxes, they can run risk of cracking even on near stock setup over time

 

Speed comes with higher risks and experience trust me

 

11.1v high burst lipo's will double fire my FFR a2

Hence I keeping her at 27 on 7.4v

I can get 32 on speed motor but I like it to feed on auto as well as semi perfectly

 

Yes it could hit 40+ but the response isn't as bigger increase from 27 to 40 say

But stock 12-13 rps to 25-27 on fresh battery BIG DIFFERENCE

 

you gotta get it right in stages - we keep saying it

Bearings won't last trust me they won't

They need bushings glued in

Or bushings underneath gears and maybe bearings on top but deffo bushing under spur gear

 

I have broke loads trust me you are trying to run too fast imho before you got it jogging along nicely

Or trying to sprint all the way through a marathon

It won't work/last

 

RIP poor soldier last weekend

[sp00n]

Are you running an active MOSFET?

 

My advice, go with a trigger replacement active 'fet

[Keldri]

Are you running an active MOSFET?

 

My advice, go with a trigger replacement active 'fet

I'm running the mosfet ive linked below. Im not 100% sure which one it is but i THINK it is this one: http://www.gatee.eu/products/aeg-mosfets/nanoaab But again im not sure. The gun is preowned and the mosfet is one of the things that was already installed. Anything you could recommend? I was thinking of hunting a Spectre to be honest.

 

Front: http://imgur.com/gHNRqdb

Back: http://imgur.com/MdxlZWK

[Keldri]

Please tell me 2 things:

 

You are NOT trying 11.1v

 

That box is NOT a G&G blowback box

It looks like it and if so you may as well cut off the front of box now with hacksaw

I have both a 11.1v lipo and a 7.4v lipo, where i usually use the 7.4 out of the two.

 

It is not blowback no

 

Also the wiring is going to get replaced as soon as possible thats for sure, the guy that had the gun before me had it screwd up.

The gun is ment for semi auto only, i forgot to mention that, so im not after the RPS at all. Its more for trigger response.

[Sitting Duck]

I have both a 11.1v lipo and a 7.4v lipo, where i usually use the 7.4 out of the two.

It is not blowback no

Also the wiring is going to get replaced as soon as possible thats for sure, the guy that had the gun before me had it screwd up.

The gun is ment for semi auto only, i forgot to mention that, so im not after the RPS at all. Its more for trigger response.

Looks like a G&G blowback to me

Bit missing on top of cylinder where blow back piston would of sat

Metal safety arm, trigger switch looks G&G-ish

Metal STD spring guide looks G&G

Bolts going through "normal" right side of box where as G&G's usually go through from selector plate side except on blowback models...

 

Hey I could be wrong and looking at a G&P box or something but first glance she looked to me like one

 

Anyway you will get overspin on 11.1v on 12:1 etc....

You shouldn't get it that much on 7.4v with stock wiring but depends on lipo C or burst and how quick the actual motor really is

 

And I would get her chrono'd first coz tbh m110 isn't gonna make any increase over a m100 with 2 teeth missing and not even a bearing spring guide or spacer to claw back any fps lost on AoE...

So yes either a bit more spacing or m115/120 on its own

 

BUT get it chrono'd first

 

Also when you get ya head round the speed issue and not to push it too much....

Your SHS piston is not going to last you yonks if going 30+. That plastic is very light - very very light like 10gms or so on its own but the plastic teeth strip very easily when pushed.

The swiss cheesing you may done - I wouldn't have drilled holes below the rail/guides as piston's plastic is very weak to begin with

also you probably haven't much of a dent in the weight of bare piston unless you start removing quite a bit and usually on top is best bet

unless you go real nutz swiss cheesing ya bare piston yo may only lose about 10% of piston weight

on a piston weight of say 11gms that equates to probably less than 1gm by what I can see in picture

Now if you fitted a bearing piston head - hope you used loctite thread seal coz they do come undone very easily/quickly

and add up to 5gms just on their own - G&G use a 5mm plastic spacer and you can go up to say a 10mm spacer

but you need to check the spring or spring guide don't bottom out on 10mm spacers

spacers will only be about 1.5gms to 2gms - so that alone will save up to 3gms over piston bearing - you would have to go some to swiss that much off.....

This attention to piston weight - which could be over 20gms:

edit: probably is over 20gms - 11gms piston and as you are using aluminium piston head with bearings....

that comes in a whopping 12.4gms !!!! so your piston weight is say 23gms or more fully assembled

you can get a full metal rack shs with piston head, o-ring + spacer coming in at about 19gms

or another heavier brand-x full rack piston - lightened at 22gms fully built

 

now getting a lighter piston as possible is good for faster return but on blowback box you don't want a heavy piston thudding into cylinder head if possible to reduce cracking - yes you got sorbo but still you want to try and keep it light as possible

(bit like being shot with 0.12 @ 350fps or .43 @ 350fps impact - the heavier mass at same speed will have more ouch)

 

Piston's and piston heads on their own are a ball-ache but if you understand and wish to not go so crazy then all steel shs blue pistons are best performers - the plastic tooth pistons by shs are crap by comparison

you can get a full metal shs piston pre swissed @ 13.5gms full metal rack

or an un-swissed one @ 15.6gms aprox

or a brand-x full metal piston is about 17.5gms

an ultimate plastic/metal mix piston is over that @ about 17gms & about £15 - why bother

yes plastic has the strip safety factor but if you keep it sensible you won't need to worry

Yes you can fit an AB Mosfet but these can make motors run warmer/hotter....

 

First off test where you at fps, rps on 7.4v and how she performs...

 

Also is she double firing or piston say half cocked...

Or

Are you flappin' about nozzle retraction and therefore it must be over running badly - nope very normal unless you run gun very slowly like stock on 7.2v nimah

 

PS - in one of them pics, ya AR latch is positioned wrong sort of trying to latch on spur gear instead of bevel gear

it is hard to see clearly but not sure if AR latch is fitted correctly or can't quite see where spring & which whay the latch is pointing

 

Now you may have just put it there out if way, but there is some wear on it and if not fitted properly the piston rolls backwards...

 

Is that what you mean by overspin, if so it is AR not fitted properly.

Yes it is a bitch to fit but Samurai's tip of neodym rare earth magnets underneath saved many a gearbox thrown across the room

And deffo yes you do need it and the bastid's spring too

 

 

uploaded and nicked from this post on Zero One:

http://forums.zeroin.co.uk/showthread.php?258993-G-amp-G-MP5-cracked-gearbox

 

Sorry Shizbazki, a clever mofo who know loads more about blowback boxes and how they can break

he is on here too and knows loads plus how to get blowback working effectively if anybody needs help

(bloody hate pbb, I struggle with just normal boxes)

 

I'm pretty - no bloody handsomely sure (in very poor lighting btw)

you got an old blowback G&G box so ease up a sec....

do some checks - hope AR is fitted correctly excuse if I'm wrong but hard to tell

get here chrono'd using just 7.4v first

report back with results on fps and rps - lay off 11.1v

and then we can go from there....

 

But if I'm right - really stick to 20rps on that box coz she very likely won't last too long even with no blowback operating

The G&G pbb boxes are weaker than normal non-blowback boxes so ffs go easy on this build