Rcommend piston setup that can take some serious punishment

[Adolf Hamster]

anyone reccommend a piston setup that can take some serious punishment.

 

this is totally unrelated to the ak and m4's ludicrous fire rates, no they didn't both die within 3 seconds of switching to full auto, this is fake news, don't believe everything you see in mainstream media sheeple.....

 

also anyone know if the marui 226 barrel fits we?

[Sitting Duck]

8 minutes ago, Adolf Hamster said:

anyone reccommend a piston setup that can take some serious punishment.

 

this is totally unrelated to the ak and m4's ludicrous fire rates, no they didn't both die within 3 seconds of switching to full auto, this is fake news, don't believe everything you see in mainstream media sheeple.....

 

also anyone know if the marui 226 barrel fits we?

 

SHS std blue full rack piston is the one most go for

alas it can bind slightly in a number of boxes (not G&G's)

 

If it is very slight binding, then sand the rails in box

If it is very tight then the cyma full rack piston is less thick

but is quite sloppy in boxes like G&G's

 

If your box has a rear inspection window then imho avoid the lightened ones

tbh safe bet is the std blue shs metal rack piston - no holes/swiss stuff

 

Do not bother with the 3 or 7 metal teeth SHS pistons

they look like the perfect pistons - but the plastic teeth are DairyLea

the soft plastic teeth strip quite quickly and are a waste of time & money

[Adolf Hamster]

4 minutes ago, Sitting Duck said:

 

SHS std blue full rack piston is the one most go for

alas it can bind slightly in a number of boxes (not G&G's)

 

If it is very slight binding, then sand the rails in box

If it is very tight then the cyma full rack piston is less thick

but is quite sloppy in boxes like G&G's

 

If your box has a rear inspection window then imho avoid the lightened ones

tbh safe bet is the std blue shs metal rack piston - no holes/swiss stuff

 

Do not bother with the 3 or 7 metal teeth SHS pistons

they look like the perfect pistons - but the plastic teeth are DairyLea

the soft plastic teeth strip quite quickly and are a waste of time & money

 

tis a windowed box and i'm not concerned about lightness, only the ability to withstand maximum high speed punishment.

 

the m4 has an all steel tooth piston which is what it just ate, twas blue but darker than shs's.

 

cant recall what the m4 box is but the ak is jg

[Sitting Duck]

.... snip

[Adolf Hamster]

I'm pretty sure in both cases it was the rate of fire did it, the jg was running the stock all plastic piston and i was expecting it to fail.

 

The m4 on the other hand has been a result of my quest for trigger response, it's asg's "high torque" motor with the neodynium magnets but despite being supposedly for torque rather than speed it spits out bb's at an alarming rate.

 

In both cases i'm happy with the rate of fire (hell the m4 i'd rather be a bit slower even) so i dont mind a heavier piston dropping the rof as long as it can survive.

 

I'll crack the boxes tomorrow and see if anything else has died but i'm pretty confident it's primarily schredded pistons i'm looking at.

[Sitting Duck]

... snip

[Adolf Hamster]

2 hours ago, Sitting Duck said:

 

Piston weight has nowt to do with rof - a lighter piston may return quicker to avoid PME

But the cycling speed will be the same as determined by gear ratio, motor, voltage etc....

 

Generally speaking a std setup eg: full(ish) stroke, 350fps you are looking at aprox 20~25rps

(The term twenties is plenty)

Once you approach 25rps you will get serious overspin even double firing on single

Gun is talking to you, if you push it much faster on a std UK gun you will run risk of PME

Unless you run a m120 Short Stroke setup PME will take place at 25~30rps I reckon

Hence why certain TM High Cycle guns were Short Stroked to achieve snappy 320fps

 

If you drop the bearings inside the piston that will save you about 4gms

which you would be hard pushed to swiss cheese that much weight off piston

drop bearings, save about 3gms, pom piston head and you should be about 22~24gms metal rack

you don't want it ultra light coz you arent pushing 50rps DSG

plus an ultra light piston is inefficient in generating compression

 

Most important thing is to ensure piston doesn't bind - this slows piston speed (not good)

(plus increased resistance in cycling - but slow dragging return will increase PME risk)

Then keep the speed at 20rps or just over unless you have done your homework

 

 

i haven't measured it but to ear it sounds like it's in the 1800-2000rpm range so that's around 30 rps.

 

i'd kind of hoped by going for torque the motor would naturally peak itself and limit the rof, but sadly it's much better than that. the etu/motor combo has some insane braking to it so no double spinning on semi but that motor doesn't seem to care what the gearbox says.

 

the aim of this gun is trigger response and good semi performance, so i'd be more inclined to disable fully auto than short stroke it, although it's nice to have the ability to spray and pray as a backup.

 

i'm about to crack it open here so i'll report back on what else has been shredded.

[Adolf Hamster]

welp, post mortem is complete, the existing piston was all steel tooth except the one that counted- the first one.

 

looks like it just couldn't take the strain.

 

i'll get a pair of the shs 15 tooth ones and see how that goes, if it can survive in the m4 it'll defo survive the ak.

 

rest of the gearbox looks fine. i'll hold off on the ak until they arrive as i'm 99% certain it'll be the same story.

[Sitting Duck]

.... snip

[Adolf Hamster]

the gun is old and it was nowhere near stock when i got it (had been upgraded a lot then abused within an inch of its life). the motor it came with was on its last legs.

 

the etu is functioning fine now after much fiddling, it's not really the problem. although sadly i can't use it to tune down the rof.

 

it was the rearmost "tooth" that forms the back of the piston that went, so the rack did nothing.

 

it's primarily a pseudo dmr gun so semi 90% of the time, but it's nice being able to dump the mag if required. but i'd sooner accept the loss of full auto before messing with short stroking it. it was fine in semi for a good while it was definately the full auto just killed it.

[Sitting Duck]

6 hours ago, Adolf Hamster said:

 

 

it was the rearmost "tooth" that forms the back of the piston that went, so the rack did nothing.

 

 

 

 

8 hours ago, Sitting Duck said:

Problem with metal racks & PME = lots of damage

if there are no plastic teeth to shred

then it will attempt to rip out the rack itself or other teeth in drive chain

sector should be ok

 

Blah blah blah....

 

snip once again for the last time

[Adolf Hamster]

34 minutes ago, Sitting Duck said:

 

 

Blah blah blah....

 

or it will try to split the rear of piston at a moulding seam right at the back/pickup tooth area

Thought I had a pic of a shs piston splitting at the pickup seam as the rack tried to get ripped out

That was a m120 13:1 SHS HT running on a bastid 11.1v 33c 1300 mah packed with plutonium I think

the LiPo is f*cked, 1 cell is 3.9, 4.0 & 4.1v - never balances it is w@nked tiny thing I got in bundle of bits

But somehow it contains so much more wallop than usual 25c Zippy 7.4v & 11.1v's 2200 mah

That f*cking battery has wrecked more guns than I dare use it now

Unless it is a really sluggish 28tpa std gear plodding gun

 

The last gun it wrecked m120 SS 3 teeth 13:1 SHS HT was producing about 23~24rps on 7.4v Zippy 25c

Really nice responsive build - so I thought let's see just good my build is... (not such a wise idea I later learnt)

when jumping to 11.1v it is a bit more than 50% as the gun is cycling already

so the boost imho is about 55%, so a zippy 11.1v 25c was cycling about 37rps and wow that is insane

getting a lot more overspin - that should have triggered alarm bells but nope I thought it would be ok

plugged that little bastid in and OMG that is much quicker - oooh f*ck that don't sound right

yup - it wrecked it before I could chrono it FFS wot a nob

yeah I was not a happy bunny after doing all that homework and planning and extra crap etc....

F*CK IT, I'VE HAD ENOUGH OF WRECKING CRAP TAKING THE PI$$ & PUSHING STUFF CLOSE TO LIMITS

 

Moral of the story - even if you do all the extra work

it will still wreck if you sail too close to the wind taking the pi$$

 

Then you will be mega pi$$ed - so plan it well and dial back the pi$$ taking or extra juice/rps

 

i get what you're saying, although i'd rather get it working again and know i just have to be careful if going full auto, if it kills the shs piston then i guess i've a decent reason to run burst fire.

[Guest PT247]

.

[Sitting Duck]

Soz - I shut up now, think I made my point/mountain more like

[Guest PT247]

mate, you offered a wedge of help to him, but he needed a whole topic for his question, not a quick answer! 🙂

[Jedi_Master]

Moved from Quick Questions & SImple answers; this was a lengthy topic in its own right.

[Sitting Duck]

I was TRYING to keep it brief believe it or not

(but as usual once I get started...... )

 

Knew or highly suspected stuff was running too quickly

coz well ergh I have done that loads of times, I'm sure many on here have also gone nutz

 

Off topic a bit, Duck Jnr gets his go faster motor

Tells him this old fart wrecked his beefy go faster motor by taking the pi$$ showing off

(blew one gearbox & the diff TWICE doing burnouts and generally being a younger nob)

 

Yup Jnr's motor has loads of warning lights like a xmas tree again & again costing loads

confides to mum:

 

" I MIGHT have driven it a BIT madly a FEW times.... "

 

rough translation - He has been a nob and driven it LOADS like a mad w@nker despite the advice

 

After the last time of building a 13:1 SS 3t m120 SHS HT running sweet @ 24rps

then pushes it near 37/38 on 11.1v, only to to put a mofo bastid 11.1v on it pushing at say 40+

then wrecked it after all that work - this makes moi a bigger older f*cking stupid w@nker

 

Twenties is plenty and call it a day now

 

If I chose to build for 30~35rps (not often now)

I'll still run on 7.4v at low twenties coz well it's cheaper and well below the limit/margins to last longer

 

Regarding pistons - SHS is a good go to piston as said - just std reg blue SHS metal rack

can be a smidge tight but usually just a mild mod to glide sweetly but not sloppy as f*ck

 

Cyma's are looser, but they are a smidge shorter in length so no chance of bottoming out on full stroke

 

Bare piston weights:

 

SHS std blue weighs 15.75gms aprox

Cyma weighs 16.1gms

 

So there is nowt in it really weight wise, just use which one fits/works best

No real need to swiss cheese them coz they aren't that heavy like some 18~19gms pistons I got

(you don't save THAT much weight even if you go nutz considering time cleaning it all up etc.. maybe 2~3gms)

drop bearing or piston spacer instead is quicker easier if fps doesn't suffer too much on spring compression

select which piston will work best in ya box

(not too tight/binding & not too loose/sloppy)

 

Yes after checking for 2nd tooth removal & reduce 3rd tooth a bit, the rack should be glued into place

not superglue, epoxy for the rack, should use epoxy for rack and bushings if poss

(superglue on bearings is ok at a push, but racks should be epoxy'd in if doing it right)

 

Whoa - getting carried away (again)

[Adolf Hamster]

wow, just goes to show i rely too much on the alerts system didn't realise this had been threadified 

 

shs pistons are in, time will tell if it survives. i'm debating putting the m4 to 3rnd burst for the sake of saving hassle and reserving the ak/mg for when people need a hosing to convince them they've been hit.

 

also, still in my defence, a stock jg ak does not count as a speed build!

 

although the m4 seems to have turned out that way it wasn't my intention, it's my bushlurking gun 

 

also it'd be nice to have at least 1 gun with decent semi auto response, the f2000 is sketchy in semi, the ak double fires and the mg doesn't understand

[Duff]

Sounds like your RIFs need attitude adjustments mate nor more parts!?

 

[Adolf Hamster]

41 minutes ago, Duff said:

Sounds like your RIFs need attitude adjustments mate nor more parts!?

 

 

They need to accept that 11.1v is their future

[Adolf Hamster]

well, time to ressurrect this topic.

 

i'm sure @Sitting Duck will be pleased (well sort of) to hear he was right, it's blown up again.

 

so since this thread it had the shs piston installed and i set the etu to safe/semi/3rnd in the hope of preventing future explosions.

 

which worked, for most of yesterday.... (it was shooting great, to many poor victim's consternation )

 

so the spur gear shredded on it's smaller gear then i suspect the resulting blast of the unloaded motor meant the pinion shredded part of the bevel.

 

the rest of the box seems fine, piston holding up well with just a little of the coating worn on the teeth. rest of the gears are ok and none of the bearings exploded.

 

so i'm wondering where to turn next, sadly as i have no electrical way of adjusting the rof short of either scrapping the etu and getting a titan, or scrapping the motor in favour of something slightly less high speed, either of which is more money than i'd really like to be dealing with.

 

mechanically all i can think to do is swap to bushings, as the piston is full-weight, i have no headroom to increase the fps, and i had the anti reversal latch still installed. gearing wise it was stock asg so i haven't been messing with ratios.

 

or maybe i should just accept my fate and start putting pennies aside for a polarstar

[Sitting Duck]

What motor was in there or you replaced the old grey 18k/blue 24k/orange 25k ifrit with

did you drop in a SHS HT or something ???

(which is 30k 16tpa like zci balanced/speed motor)

SHS HS is a 14tpa 40k motor

 

A zci torque is a 22tpa aprox 22k rpm motor which would probably be up your street @ 11.1v

& dial it back a bit

 

https://www.ak2m4.co.uk/internal-parts/motors-parts/zci-motor-high-torque-long

 

if bevel was shot you could replace it with a 9 tooth one from ak2m4 instead of 10 tooth

that would dial back say 10% rps aprox making say a 18:1 now a 20:1 gear ratio

 

https://www.ak2m4.co.uk/internal-parts/gears/zci-9-tooth-bevel-gear

 

But that bevel only dials it back 10% and feel you was likely going quite nutz 

 

Somehow you need to dial it back a bit

My gut reaction would be grab a 22tpa zci from Pete while he has them in stock

locate a std spur from a junk box of bits that works to get gears moving

 

check bearing under bevel for wear/play and perhaps if iffy replace with a bushing

fit a very thin 0.1 hex shs shim or something very thin under spur/bushing

not much else or a complete new gear set to throw shimming out

though check motor height/bevel etc...

 

chuck it back together with a once over and gun should be less insane or not so prone to wrecking

 

keep old fast motor for a 7.4v build

[Adolf Hamster]

it's an asg 40k, with extra fancy neodynium magnets, so yes pretty spicy (and pricey, hence wanting to keep it).

 

i do have an shs hs motor knocking around somewhere, or potentially could pillage the g&g high torque from the f2000 (which still isn't feeding, well, not on the field at least)

 

i guess my choices are keep upgrading the gearset/rest of the box until it can take the punishment, change motors, or just give up and go hpa.

 

but then i'll be tempted to drop that motor in the mg42 and we'll be right back to square 1

[Sitting Duck]

High Speed Motors run at 40 to 45k rpm with a 12 tpa producing lots of heat/amps/watts

really only for say 7.4v lipo

this in a stock gun will produce at least 20rps maybe 24rps

 

you might be able to run on modest 9.6v which is about the same as a beefy 7.4v

but not 11.1v lipo coz increase rps by 55% or x 1.55 and you are over 30~36rps

 

depending on G&G motor is 18k to 25k

grey are ferrite 18k ferrite 27/28 tpa,

so is blue but slightly better ferrite magnets & faster at 24k rpm (19/20 tpa maybe)

Orange is 25k neodym likely 18/19 tpa-ish

 

If G&G motor is grey and gearset is totally shot with no spare spur to hand

you could drop in a 16:1 replacement set - or at least the spur which is what alters the ratio from 18 to 16

(actually it is a con, 18:1's are 18.65:1 & most 16:1's are in fact more like 17.25:1 - so 16's are a con)

but if set is totally shot 16's would be worth considering over a 18 set if buying new

you got plenty of grunt running on 11 & ratio change is very slight like about 7% quicker

 

if running on 18k grey which is quite slow then might be an option if gears are shagged/no spare spur

a blue/orange - hmm might not need it with a snappier motor

 

Twenties is plenty, when you get near 25rps you get overspin but you got AB with ETU

but still overspin if quite severe the gun is talking to ya

more overspin from worn COL occurs but if all working OK & no worn COL etc....

if a reg gun is overspinning quite a bit without AB then the gun is screaming ease up trying to push it

 

so really 20rps to 25rps is limit unless you did homework like Short Stroking & all that crap on UK 350 gun

 

now 18k motor will produce about 12~13 rps on 7.4v

11.1v will get you 20rps on std gears or maybe 21.5 on 16:1

 

24k~25k will get you about 15rps on 7.4v aprox

11.1v will get you about 23rps on stock 18:1's and leave it there

 

These a rough but fairly accurate-ish figures depending on numerous factors

how good shimming is/isn't

wiring crap 18awg to mental 14awg

spring/barrel/compression & efficiency blah blah blah

mental 45c battery or mild 15/20c battery deans & f*ck knows what else.....

 

but roughly give or take a round or two a second

 

Ya gun won't destroy itself so quick

your battery will last longer

And your gun apart from running cooler, you shouldn't need to keep picking up bits of teeth every month or so

 

The gun is always gonna complete the cycle due to ETU

so it is very unlikely you can spam the trigger on semi faster than 20rps in real instances

but about 20rps to 25 rps or twenties is plenty the guns just run better

regular manual AEG's are much less prone to releasing the trigger too quickly & locking in dead zone

once you get to 20's the risk of dead zone due to bad trigger discipline really reduces

 

you can get a bit faster say 30's with a bit of SS work m120 spring etc....

well really 35rps but you wanna always dial back a smidge to not sail too close to the PME wind

you only need one misfeed on auto/burst to clog & slow piston's return speed and BAAAANNGGGGGGG

you are picking out teeth once again - not worth it going too nutz and too close to PME limit

 

I'm not clever - far from it

 

I've just done EXACTLY the same thing as you like many on here have learnt the hard way

 

Clever people would have heeded good advice but I thought nah I'm sure it will be OK....

So alas I ignored sound advice and found out through my own mistakes

But then again that is what wisdom - wise after the event is all about

 

Learning from our mistakes & that is one thing I am good at- making lots of mistakes...

 

 

 

but my fav I live by....

 

 

 

[Adolf Hamster]

hmmm.

 

having tried running it previously on 7.4 to test for problems (which turned out to be the cutoff lever but we were just throwing everything at the wall at that point) and the rof wasn't noticably lower. it wasn't catching/overspinning.

 

i do have a spare spur, but being from the original king arms box it's been through the wars and then some and not in great shape.

 

i'm leaning more and more towards just giving up and going hpa at this point, feels like changing motors and gearsets is throwing good money after bad.

 

maybe keep the 40k motor for the mg, as thats a gun i would be happy doing a ss/dsg build in.