AOE question

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ProPain87

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Evening all, 

so im correcting the AOE on a m4 and using these http://www.patrolbase.co.uk/airsoft-piston-piston-cylinder-heads/laylax-pss10-sorbo-silent-damper-pads.htm#.WW_i_YXTWEc

my concern is that there is a good gap around the outside of the pad (between the cylinder and the sorbo) thinking of using silicon to fill the gap but then would it be better to leave it to allow room for the pads expanding when the piston head hits? 

Would I get fps inconsistencies if I leave it as is or am I overthinking things a little (it is getting late lol) 

last time I used sorbo, it was a good few years ago and I used airlabs but I can't remember if there was a gap like with these laylax 

Any advice appreciated

 
Leave it as it is, it'll be fine.

If I use Sorbo pads I usually use a shower hose washer as the top layer.. They're a lot tougher than the sorbo and don't compress as much. So you get a more consistent AOE correction and the sorbo pad lasts longer.

 
Thanks!

do you know what size the washer is that you use and I'll grab some from b&m or somewhere. I did think that these laylax pads felt very soft

 
20mm diameter (cylinder is aprox 23.8mm)

2mm thickness with a 5 to 6mm hole - no less

(M5 or M6 they might say)

1mm thickness is a bit too thin, 1.5mm min or more for durability on top of sorbo

3mm thickness at a push but might be a tad too thick on some builds & correction of AoE

 
Sorbothane on it's own is not very tough (we've had this convo on here before), best bet is to face it up with something more resilient. Personally I use the Airlab sorbo pads https://airlab.parts/collections/gearbox-parts/products/sorbothane-pad-70d-hardness which come with a protective cap as standard. 

If you bond the outside of the sorbothane with something that prevents it from "squishing" under impact then you're preventing it doing one of the main things it's there to do (protect your gearbox from impact damage).

 
Well that's annoying, he was out of stock Sunday when I ordered the Laylax otherwise I would of used his as I said I've used the airlabs sorbo before and liked it. I'm using the gun soon so I'll use what I have and get the airlabs when it needs replacing. 

I got the washers to top the sorbo anyway 

http://www.screwfix.com/p/arctic-products-shower-hose-washers-5-pack/3841J?kpid=KINASEKPID&cm_mmc=GoogleLocal-_-Datafeed-_-Heating%20and%20Plumbing&gclid=EAIaIQobChMI563Wpb2X1QIVar7tCh1rvAtXEAQYASABEgLHE_D_BwE&gclsrc=aw.ds&dclid=CKn5i7SAmNUCFTOg7QodbrMDQw

 
Well I started to reply earlier and got carried away - as per usual...

20mm diameter (cylinder is aprox 23.8mm)

2mm thickness with a 5 to 6mm hole - no less

(M5 or M6 they might say)

1mm thickness is a bit too thin, 1.5mm min or more for durability on top of sorbo

3mm thickness at a push but might be a tad too thick on some builds & correction of AoE

You can buy sheets of neoprene in different thickness to cut/punch out if you are sad

but a rubber washer & some superglue is really all you need on top of sorbo - it's a toy gun ffs

There is the DIY silicone pad mod:

http://www.airsoftsniperforum.com/43-longrange-aegs/9062-guide-cylinder-head-damper-remold-bye-bye-sorbo.html

This is dirt cheap to do, but takes a bit of time to accurately "guess" the amount to mold & all that

Plus you need to leave it to cure overnight/24hrs - I suppose you do this first as you rebuild a box

Sorbo is expensive, much more than ordinary rubber even buying it in small sheets (70D)

Do you really need sorbo compared to using a soft-med soft neoprene ?

(cheap china guns come with a wtf hard as nails/bricks disc half glued on there)

Yes/No - depends on gun/budget, some people always use it others not so much

If installed on its own sorbo shreds asap so as Hangtight said cover it with a washer

There are also piston head spacers/shims to fine tune/adjust AoE if required

but really not needed for most builds - can use a really thin 1mm x 15mm washer say

(when fitted between piston/head it squishes to 0.5mm to fine tune the final AoE)

But Really ??? it shortens the stroke a whisker, adds weight (a fly's scrotum) and tbh not that much of a biggie

Correct it to "there abouts" - it varies on cylinder head & piston head being used

(some piston heads are longer/shorter)

Test the AoE with spring fitted - get the AoE as good as you can (better than stock)

Whooooaaaahhh - gone overboard again

Hence why I snipped it and just said get a 20mm washer..

Washer size: 20mm x 2mm & 5/6mm hole will do ya

Reason I included all this crap is to provide loads of info, pro's/con's etc...

Plus other options if doing crap to more than one gun

If just doing one gun buy Airlab stuff than a pack of washers, sheets of sorbo/neoprene

Or pi$$ball about with silicone in a slow speed drill - bloody messy and setting time etc....

More than one way to skin a cat - to each their own as they say

 
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Cheers for all the help, I glued it all together and filed down the piston teeth tonight, just got to wait for a new spring. Gone for a 110 to compensate for correcting the AOE

i did see the silicon mod but tbh it sounds like way too much hassle to me lol but that's what got me thinking about running it round the outside of the sorbo. (Which I haven't and won't)

the washers from screwfix we're a tiny bit smaller that the sorbo but same internal hole so it'll take the brunt of the hit (hopefully) 

 
I've never had to go with a harder spring to compensate for the slight loss of piston stroke you get from AOE adjustment. You'll find you'll be shooting over 350fps, unless you're using a really short (less than 180mm) barrel.

 
Hangtight said:
I've never had to go with a harder spring to compensate for the slight loss of piston stroke you get from AOE adjustment. You'll find you'll be shooting over 350fps, unless you're using a really short (less than 180mm) barrel.
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The barrel is very short although I've not measured it, it's smaller than my hand (wrist to finger tip) it was firing at 300 before so it's going to drop to 280-290 if all is well I suppose I can test it with the spring but I'd like to get as close to 350 as possible. I can always snip the spring if it's hot 

 
In which case you may still find you're  a little over 350 to start with, but it should settle to just under. Don't cut the spring if you can help it, unless you're good at collapsing the last coil and grinding it flat. You're better off taking the bearing off the guide or out of the piston to give the spring a bit more space.

Although you reduce the stroke slightly by doing the AOE adjustment, you'll still have enough cylinder volume for a 370mm barrel using 0.3g BBs, but the short barrel only need the stronger spring to accelerate the BB hard enough to get it up to velocity in the smaller distance available.

Have you got the correct ported cylinder to suit that barrel length?

 
I'm using the one that came stock in the gun. It's either a 3/4 or just under I'll measure it later or stick a picture up to show you I'll chrono it with the spring I have first. What about a nuprol 105 spring? I've never cut a spring so I'll probably not bother doing that 

 
If you're going to get a 105 spring then the Element works well. Depending on the build, in a regar carbine then you might have to take the bearing off the guide to drop the fps under 350. But a good M100 with decent airseal will shoot 335-340.

My CQB gun has a 170mm barrel, SHS M110 spring and now it's settled in it runs just under 340 with the bearing in, and 320 without (site measured) . First time I fielded it out was 353fps on the site chrono, 347 on mine.

 
So I put the gun back together today with a nuprol m110 spring and removed the bearing from the piston and it chrono'd at 300fps +/- 2fps so got good consistency but a lot lower fps than I expected. Going to put the piston bearing back in tomorrow and try again. Any suggestions as to why my fps is low.

 
Either you've got drag somewhere in the system slowing the piston down, or an air leak.

You should gain about 20 fps putting the bearing in, and have you got the spring the right way around? If it's got an end with closer spaced coils that should be on the spring guide. A non linear spring installed the wrong way around losses around 7-10 fps.

Do the 'bit of paper in the magwell' air seal check, and with the upper receiver off put a finger over the end of the air nozzle and fire a shot on semi only. The piston should either stop, or at least take a while to reach the end of the cylinder.

 
I'll strip it tonight and check there's nothing dragging and put the bearing back in, the spring is like you described so I'll check that aswell, I've got another barrel which is about 100-150mm longer do you think I should try that first, maybe the cylinder is over volumed? Also the nozzle doesn't have an o ring inside but compression seem fairly good considering. It was solid with out the nozzle and with it on the piston moved down slowly as I expected for a non o ring nozzle.

if I can get it to 330-340 I'll be happy at that

 
If your barrel is only 150mm long and you're using a 3/4 cylinder then you're over volumed. Even using 0.28g BBs you will only need around 25mm of active piston stroke,which would be a half cylinder. With the 3/4 some of the energy stored in the spring is shifting the BB but then the rest is wasted because the BB has already left the barrel before the spring has fully extended.

With the half cylinder the spring has transferred some of it's stored energy into kinetic energy of the piston before it even starts compressing air and moving the BB. The combination of the kinetic energy and the remaining energy stored in the spring then go to compressing air, so more energy is recovered to do useful work. The BB leaves the barrel about the same time the piston completes it's stroke so much less energy is wasted.

 
So would a half ported cylinder actually increase fps in my current set up. I do have one my mate gave me to try but it's poor quality made by 5ku it's paper thin. So a longer barrel will increase fps so I'll give that a try before I strip it but I'm going to strip it to check the spring anyway and put the bearing back in and I might even try the other cylinder if you think it'll make my current spring and barrel set up better

 
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