AOE Sorbane & Silent piston malarky....

[Sitting Duck]

Just putting back together my CM18 I fixed & broke last weekend.....

Think now the piston snapping at initial tooth was not just down to me pushing her with

11.1v lipo & hi-speed motor but also coz I thought ahh wtf she will be ok as she was.....

long story short AR latch snapped - yup snapped so replaced that and noted was on 300fps

chucked in a new m105 spring in there and also notice seal on cylinder/piston wasn't perfect

so chucked in another piston

Now noticed AOE wasn't brilliant at all but was same as old stock G&G one but better seal

getting 350 or just just under or over a tad - very pleased

pushed her with a newly charged 11.1v lipo - probably coming off charge @ about 12 to 12.5v

BANG she didn't last long.......

tappet/nozzle moving I can see in magwell - yup piston shagged

tried short stroke & hi-speed gears, torque motor, higher springs

but not getting great results I was expecting so gone back to stock gears now

OK - do AOE but thought I'd try a silent piston head as it seemed bigger/longer than most others

yup sure enough it is longer piston head - ok lets use a silent or silent looking brass 2 o ring cyl head too

(using a flat cylinder head seemed too much spacing for AOE it seemed)

checked AOE looked text book perfect after removing 2nd tooth and very nearly removing 3rd on one side

Yup that to me looks dogs dangly bits - exact same as I could hope to achieve with normal sorbane pads

removed the bearing on piston head and replaced with a similar size 5mm thick plastic spacer - much same

as G&G had fitted on stock black piston & head with green o-ring....

(removed bearing on piston head to get weight of thing down to 20g without swiss cheese piston)

bit of tape on cyl head - yup she has good seals plus shs nozzle with o-ring - just like last week btw

(dunno why but G&G nozzle didn't have o-ring inside - or I couldn't see it or fell out)

So - that was supposed to be long story short ????

Anyway she is back together with silent piston & head & M105 in there (torque motor atm)

BUT fps has dropped a bit to about 330fps - lost 20fps or about 6%.....

It is no biggy and in a kind of way was expecting some loss as the piston travel is sightly smaller

with correcting AOE - even with sorbane the piston probably doesn't travel say 1 tooth

- aprox 3mm that is used to with pi$$ poor AOE

Sound is maybe a tiny tiny bit quieter than before but reckon is more muffled or different sound

of piston slapping the head - yup there is a thin stock pad on cyl head and piston is a bit squishy

(getting right techy with all these descriptions now)

So apart from what I hope be ok for a while - two main questions at the end of all this.......

Does this drop in fps kind of make sense or marry up with others findings when doing AOE ???

And are these Silent pistons from element/ultimate/lonex/joe bloggs really worth it or have I just

chased yet another crap idea down an alley & lost myself yet again on my gearboxing journey ???

cheers in advance for any input ideas or comments

 

[PT247]

might have gotten wrong end of the stick here but if you have removed teeth then the piston/cylinder will have lost volume by a bit as it will not be travelling as far, also if you have put a pad on the piston it will also reduce volume, any reduction in volume will drop fps.

 

[Sitting Duck]

not removed any teeth from final stroke - no this stock gear setup hasn't been short stroked

(did that on a previous setup and got unhappy weird results)

This stock G&G gear setup - all teeth on sector etc....

Only teeth removed was to correct AOE - no sorbo used coz silent piston was bigger/longer

but same thing as sorbo pad or two on cyl head correcting AOE

(sorbo's I have are about 2mm thick so usually find 2 req for most times)

But initial starting point is aprox 1 tooth back now AOE is done

So that is a 1/15th less travel I guess or 6.666% which kinda equates to the 20fps loss I suppose

(I was getting 350 last weekend on same gears/M105 spring with crap stock AOE)

If I'm honest I guessed I would be down a bit but was kinda hoping it might be about 10fps loss

otherwise If I know what I know now I could maybe shoved a m110 spring in there and got 350fps

Before anyone says - blow me only 10 off what ya hoping and gotta lose something.....

my site is 350 limit, and quite likely fps will go down in say 3-6months was hoping for best as possible

but if she drops too much then I can throw a m110 (SHS) in there further down the line....

(M105 is Element brand btw - not super highly rated brand by some so we shall see)

My findings at moment it seems:

Correcting AOE - that 3 or 4mm will in effect lose ya about 18-20fps or 5 off ya M105

Don't know about Shushy Silent piston - will give it a while to bed in so to speak n see

(just wanted to know if people think these pistons are crap/ok/good - well its in there for now)

Soz for long post - still learning and you can do all the maths in the world and still get high/low results

not to mention the barrel length/cylinder port matching on top can make such a difference

though think G&G stock blue cylinder is correct (large single port on a 250-ish barrel)

Still quite happy with it and finally put a mosfet & deans connector in there

even pushed it with a 12v nimah that was 14v just off charge - just for a quick test

(the more I break the more I learn from my mistakes)

 

[Sitting Duck]

A small after thought here....

If ya purchased a cheapo gun that is just over the 350 limit - say 365-ish....

Then it "might" be worth checking & correcting the AOE first before chucking in a lower spring

Reckon that some cheaper guns may be like this more than higher end guns

and could be brought down when opening up box to check AOE & re-grease etc....

Hmmm when I tidy up a bit I may just check my slightly hot Cyma 028 AK's AOE

before just reaching for new spring perhaps ???

 

[Sitting Duck]

Final update - well hope so unless she breaks (again)

Fitted new motor connectors coz one seemed a little weak and then blew like a fuse

(probably 14v+ didn't help - bollox don't tell me trigger wire or box jammed - oh just connector phew)

Well changed them both and even added a drop of solder at bend to help strength/lower resistance
Then chucked in the high speed SHS motor, seemed very snappy and decent rof on a 7.4v lipo
then tried a 11.1v lipo - possible 12v not checked atm - WWWWWOOOOowwwwwwww

"She'll no take it captain" as Scotty would say

The reason why I am doing all this - well if works out well then maybe will do similar to other CM18
But more so will hope to do this stuff to my poor old CM FireHawk that has much lower rate of fire
than the first batch Top-Tech FireHawk my son mugged off me a while back
(In the TT FH I put in a slightly harder bucking and few peeps say how the heck is that baby out-ranging me ffs)

anyway - test results and what deans battery was putting out on multimeter

11.1v LiPo - 31.41 rps 329.3 fps (12.25v shown on test meter)

9.9v LiFe - 24.15 rps 328.1 fps (10.1v shown on test meter)

7.4v LiPo - 19.21 rps 323.7 fps (8.1v shown on test meter)

LiFe's are about the only batteries that come off charge with only a slight increase in volts

LiPo's were 2200mah Zippy compacts - LiFe was 1600mah all 3 were 25C rated btw

with the above info most likely will keep her on say 10v LiFe or 9.6v old skool nimah

but deffo reckon G&G might have just used a higher speed motor in TT FH coz it hits

around 22rps on the 10v mark with no mosfet

Normally the CM range with stock motor hits about 15-16rps with say aprox 9v mark - I dunno

but from memory I think thats what they kinda hit stock wise....

Hi-Speed SHS helps and deffo Mosfet is making it running more efficiently squeezing a bit more

out of it than last weekend before she broke - about 26-27 rps on same 11.1v (12v+ from charge)

same spring - same gears - same motor - just 20fps less mainly due to piston head's AOE thingy

yup - gonna leave it there & hope she don't die again too quickly - pretty chuffed if she lasts

 

[Ian_Gere]

Silent piston head is supposed to be used with a silent cylinder head - the cylinder head has a small concave sorbo pad which causes an airbrake effect as the last smidge of air is forced from the outside rim of the piston area past the interface of the protruding piston head and cupped cylinder head - it's not all about shock absorbtion by squidgy faces.

TBH i'm surprised by your findings of 20FPS drop, but as you say, the percentage of piston travel does add up to around that.

 

[Sitting Duck]

it was a brass concave cylinder head used or one that looked like one:

"yup sure enough it is longer piston head - ok lets use a silent or silent looking brass 2 o ring cyl head too

(using a flat cylinder head seemed too much spacing for AOE it seemed)"

it came out of a SRC v2 - deffo concave type but noted it wasn't a 101% perfect fit on the concave's contours

(not bad but deffo not perfect moulding so to speak - but then I am too fussy with mega OCD thrown in too)

think I was expecting only 10 drop but maybe if I had a perfect matching silent head then I may got 340ish

Think also barrel length is on the borders of one or two ports and that can make a difference if it isn't matched up

But hey - it is working - so far (damn that is just tempting fate saying that)

Have pushed her a bit and deffo with fet & 16awg I can see the improvement in rof & response

(27rps nearly on just hi speed motor last week & now getting near 32 on fresh 11.1v lipo with fet n wires)

that works out at about 17% increase - maybe some might be from 20g piston - think snapped piston was about 23g

lets see how she goes - if crap in a few games then m110 in there

soz for yet another epic long winded tale - but just posting my findings and all that

 

[Ian_Gere]

If your concave cylinder head and piston heads do not match up perfectly, that is a bit of air which also fails to be expelled... @its most compressed too, so that will have the effect of losing a lot more volume than would seem to be the case. Those heads are sold in pairs - i have seen them singly though and thought, "WTF?" for exactly this reason.

 

[Sitting Duck]

cheers for that

I got the ASG version piston head from LWA as a freebie points thing a while back

I got a matching v3 AK cyl head as I was looking to use it in an AK type DMR

kinda looked at silent coz of it doing AOE as is but my "that will do" SRC head let me down

I should of got this:

http://www.patrolbase.co.uk/airsoft-piston-piston-cylinder-heads/asg-ultimate-cylinder-head-v2.htm#.VIXvxMkknIU

deffo more sorbo/rubber on outer ring than the SRC one and no doubt it would be a perfect seal/fit

so maybe will look about & grab one ready to put in there next time she plays up

hopefully claw back of the missing fps

atm it is still better fps wise than it was @ 300fps

can take it anywhere even the 328 sites...

fires like hell compared to old stock setup

(shs motor, fet deans etc....)

both me & duckling - my thieving tea leaf son will nick her back

(he is happy now hitting 30rps but said keep it at 24 on 10v)

fps is not the ultimate be all & end all but maybe if spring starts

to lose its tension will drop 110 or maybe look out for proper head or set

or just use conventional piston/cylinder heads with sorbo......

Hmmm those options I may do on either other CM18 or CM FH

This rof is on stock 18:1 stock gears and think it is a safe option to obtain better rof

Than use a silly hi-speed gear set like 12:1 and maybe run risk of pre-engagement

plus 12:1 strain on stock motor so may require new hi-torque motor anyway

Yup will give her a good stress test next weekend and if she still works then maybe

will start putting together some bits I want for chrimbo.....

Dear Santa,

I have been a very good boy....

Well most of the time I was very goo....

I really tried to be kind and go......

Ok I did intend to be goo

Oh f**k it - tell ya what Santa - maybe I will just buy my own presents this year

 

[Sitting Duck]

small update - she lasted 3/4 of the day......

motor height screw kept undoing a little bit - looked ok but guess when hammered

she thought about unwinding a bit on full auto with 11.1v

(need some thread glue - oh well...)

kind of limp along with her going nuts and pushing her - jeez went through some ammo....

Finally fet decided to quit - a pcb based fet and think was getting too hot and some contacts

started to crack/unsolder - still works but only if you squeeze fet a bit

No doubt the basic fet would be ok on standard setup I reckon

but on this gun I am pulling loads of juice on hi-speed motor

Ah well - was hoping gbox was gonna die and then I was gonna fit the proper silent cyl head

but as box seems ok still no point opening her up just yet as is running ok mechanically

Ah well just ordered a load of 3034 mosfets + some bits to put together my own mosfet

(may look into a small heatsink - pc mem stick spreader or something if it really needs it)

not bothering with another P-Mosfet for braking just yet - hoping I might get away with it

as it seemed to not over-spin much even at hi speed - just need a better fet like 3034

(it is highly regarded as one of the best fets out there - so we shall see)

Yet more breaking stuff & learning - good fun all the same

 

[Sitting Duck]

Blimey - sorbo can really affect stuff.....

http://www.4shared.com/zip/aNKGJs4F/barcyl_installer_2.html

if you mange to get that sodding running from this place:

http://www.filairsoft.com/forum/showthread.php?79832-Cylinder-Barrel-Ratio-Tool-%28updated%29

well blow me - do some maths on cyl/barrel setup & click on sorbo yes/no

can really make a difference doing text book AOE & volume malarky....

Yeah I know this stuff can only be taken as a guide and there numerous variables plus the odd

weird result on what works/don't and perfect optimal stuff but you get to see stuff without reaching

for calculator or a PhD in mathematical bollox

jeez - I just struggle with stuff not breaking atm let alone all this geeky anorak maths crap too

but was shocked the effect correcting AOE or sorbo "can" have on your previous cyl/barrel ratio malarky