Some easy simple Airsoft Maths that I think work

[Lozart]

(PS nothing cool about not knowing how to read the above derivation, its the sort of thing any 16 old that isn't failing maths can do, which is the majority of them. If you can't follow it you should consider a trip back to school not trolling me. It only reflects badly on you that you read this. There is a serious ignorance culture in the UK around mathematics and that concerns me greatly considering how much our economy and businesses depend on it. This isn't rocket science, I would know. The above however could still be wrong, I make mistakes like any human)

Is that really necessary?

 

[BrightCandle]

Is that really necessary?

Wow a troll post, surprise! Attack the maths and talk about the topic of the thread. This isn't the topic and your own ignorance or belief that its cool to act ignorant is not the topic and hasn't been since the beginning. So yeah I posted that its not cool to go offtopic in that way and what it makes you look like, you have two options really, complain about it or get on topic. I have a big post on topic, you have posted a lot and said nothing.

 

[Lozart]

Wow a troll post, surprise! Attack the maths and talk about the topic of the thread. This isn't the topic and your own ignorance or belief that its cool to act ignorant is not the topic and hasn't been since the beginning. So yeah I posted that its not cool to go offtopic in that way and what it makes you look like, you have two options really, complain about it or get on topic. I have a big post on topic, you have posted a lot and said nothing.

Wind your neck in!

I was asking if it was necessary to imply that anyone that couldn't understand the maths was stupid. Hardly trolling. In fact there is no trolling on this thread at all, granted there's a fairly hefty derail but that's not the same thing at all.

 

[Sitting Duck]

most cylinders are 23.8 - radius of 11.9mmm

think the differences in between 6.08 & 6.01 barrels - even though most might stay @ 6.03 is more like 1% but i said 1.5% to cover most variables

(if you said 6.02 to 6.08 then 1% difference in diameter or 0.5% in radius before we start the maths)

However the difference in barrel and even in standard & bore up cylinder and there 0.5% or 1% or wtf 1.5% is really very very little

in relation to an incorrect ported cylinder being used

eg: a 3/4 cylinder (363mm barrel type of cylinder) used with say a 225mm barrel = massive over volume of air and a drop in fps for user

Not all air can be full expelled anyway eg: silent piston/cylinder heads

also even though the volume of air is measured up to port for the first few mm there is next to no compression generated

much like even with max stroke of piston - the first few mm's when piston is released the speed of the piston moving is very

very little as it gathers momentum and starts to become effective compressing air in cylinder

Furthermore - the max amount of stroke on a normal cylinder after AOE is really more like 50mm

this figure is derived from the first tooth on sector gear aligned on piston in 12 o'clock position

then 16 teeth later......

16 x 3mm pitch on the teeth = 48mm

add on another half a tooth where the gear drives on a tiny bit further and slips to release piston = 50mm

AOE is done but normally AOE is a max of 4 to 5mm required so that would equate to 55mm on non AOE

but is widely accepted that AOE should be performed in AEG's

the above rough calculation also works on L85/SR25/SVD AEG's with 19 tooth pistons as well

Normal Cylinder 71mm - has max stroke after AOE of 50mm

SR25/L85 has a 82mm - has max stroke after AOE of 59mm (3 teeth more) but lets say 60mm

which kind of equates again to a 455 - 500 absolute max on standard cylinders

and I guess 550 to 600 on the few longer cylinder AEG's

(unless you are using a 15 tooth piston & spacer in ya L85)

for normal 0.20g bb's the accepted 1.5 to 1.6 barrel/cylinder ratio applies

on heavier bb's like I said this is thought to need be higher due to a heavier mass being propelled down barrel

But - unless I am mistaken with barrel differences being like 1.5% different aprox and even with a bore up kit

it can't change that inner volume that much either.....

Cylinders have an external diameter of 1 inch or 25.4mm - or won't fit inside the box easily

25.4mm - 23.8mm internal leaves a wall of 0.8mm.....

can't see a bore up having a much bigger internal diameter more than say 24.2mm or it wouldn't be very strong

(can't measure as I don't have a bore up cylinder myself but if the above figure is correct-ish then that is just 1% increase diameter max)

 

[Sitting Duck]

The general idea is to take a cylinder and within say 5 seconds have a fairly good idea

what length barrel will work with this cylinder and its port location

all without needing a calculator or a pen/pencil

I think the above guidelines do work out very well considering for general factory standard 0.20g bb's

bear in mind that the general norm also states that max max barrel on a normal 16 tooth setup

is between 455 on large AK's but not much more as 500mm barrels are not really efficient on 16 teeth setups

hence why SR25/L85 barrels and SVD go for the extra 3 teeth giving them an aprox 100mm extra barrel length

of 550

yes some SVD's have a 590 or 610 and yes you can fit a 500 barrel to a standard 16 tooth setup box

but many posts say this is not quite as fully effective/reliable as you are right on the limits

I refer to my quote that the stroke is 50mm x 10 = 500mm

but remember the fact that piston speed is only just starting move from 0mph and first few mm before compression begins

(probably why most tech's - (I am not btw) state 455mm barrels for normal gearbox's is rule of thumb)

 

[Sitting Duck]

If anybody is actually interested.......

Just done some quick rough tests on 2 guns that I think are over volume'd

1st gun is deffo way over volume'd

it should be hitting about 300+ but is hitting 240 !!!

(this increases a fair bit to 280 with a longer barrel but this is too long so under volume'd)

2nd gun I strongly suspect the port is marginally incorrect - hitting nearly 300 but likely to hit 345

Also I think though over volume may push out heavier bb's better perhaps on gas guns/pistols

this does not quite seem to be the case on AEG's - I'll explain......

1st gun - seriously over volumed - barrel needs to be about 120mm longer I reckon by my maths

(deffo seen higher fps on longer - but too long barrels so a little under expected fps)

240fps on 0.20's average

So I thought I might see a slight increase or same on heavier bb's rather than usual drop

(sounds reasonable if ya pushing out too much air for 0.2 but might be good for .25 or .30's)

NOPE both guns did not show any close performance at all on using .25's or .30's

240 on 0.20's

215 on 0.25's

190 on 0.30's

aprox 25 fps drop each 0.05g increase

2nd gun - I suspect needs a barrel maybe about 80mm longer for the current port position

(haven't tried slightly longer barrels but I have a gut feeling the port is a bit out)

300 on 0.20's

270 on 0.25's

240 on 0.30's

aprox 30fps drop for each 0.05g increase - but starting figure is higher if that means owt

So the above crap kind of blows the idea that an over volume'd aeg will push out heavier bb's

much much more effectively and maybe close to 0.20 performance......

(well it might if you whack in a heavier M120 spring on first gun but not tried that and probably won't atm)

Also by studying the output figures it might come to light on the performance lost factor

THIS IS JUST A ROUGH AS OLD BOOTS FIRST GUESS THOUGH......

Gun 1 has a barrel aprox 120mm too short I strongly reckon - take half of that 120 figure = 60

add 60 to 240 then that would equate to about the right amount expected 300fps

sounds a lot but this is well n over volumed and the seals are or was very good

(it is a CM FireHawk with a 120mm barrel and a port for about 250mm)

Gun 2 has a barrel I think of about 80mm too short - take 50% of that 80 = 40

add 40 to 300 and I really think it should been hitting about 340+ fps

(crappy SRC with a 275mm barrel and a port I cut on full cylinder that I reckon was more for a 363 aprox)

I haven't tested this second gun a lot or with any other different barrel lengths

But there ya go - 2 guns over volume'd and serious drop in performance from it

(rough estimate though as to performance lost but I do think hop/tappet/nozzle is sealing good before you think its that)

Also - Ithink my calculation of 12mm might be a litle too low

I think the more accurate figure is about 15mm to 16mm as the O-ring on piston can sit quite far back on some

Suffice to say correcting the AOE can vary - usually it is about 4mm-ish but recently had a box that needed 7mm - no $hitting 7 bloomin mm ffs !!!

(in the end I put a 5mm spacer behind piston head - checking central alingment to piston & a thin sorbo/washer on cylinder head)

So yeah - ignore the 12mm & go with say 15mm off the port measurement chaps - my bad