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Sitting Duck

Some easy simple Airsoft Maths that I think work

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I'm sure these easy ways to work stuff out is pretty damn accurate & no calculator
or degree in mathematical engineering required

I have checked them and the gears ratio saves a major headache indeed

(unless you love counting up tiny teeth - 21 22 23 23 - no crap start again 1 2 3)

 

Count amount of turns on bevel gear to rotate the sector gear 1 full revolution & multiply by 3

checked this against stock, high speed & high torque gears - works out very well

and finally figured out wtf all them 100:200 & 100:300 gears bloody mean as well

 

Then just recently noticed how the port on cylinder kind of works out right without
all that Pi r ² crap working out volumes of cylinder & barrel and ratios etc....

So please have a look and if your own gun is running well see if the cylinder port bit makes sense
eg: length to port minus 12mm aprox = say 30mm....
multiply that final figure by ten - yeah I think you shouldn't need calculator for that one
= 300mm barrel for that port position

yes there a few variables eg: Tight Bore & Bore up kits but in general these will only throw out figures
on volume ratio by about 1% to 1.5% max on each variable....

 

I have checked this against a few cylinders that are for certain barrels and it works out very well indeed

(it is that simple to me I dunno why peeps bother with old π r ² x cylinder/barrel length)

plus some programs for calculating ratios are not easy to understand or don't seem to work out right to me

(bit where you enter or measure cylinder length or port is a little unclear to me)

plus people saying oh yeah a 3/4 cylinder is for 363 to 410 - wtf ?

3/4 is not exactly very pinpoint accurate and range of nearly 2 inches is also a little wide too ffs

I think it is nigh on there with the 12mm figure subtraction is about correct - but the cylinder should have AOE done

(Should really do AOE anyway is the general feeling)

This adds aprox 4-5mm to say 6mm on cylinder head inside the cylinder itself - never mind go with 12mm for now ffs

(O-ring sits aprox 2mm back from piston and is what creates the seal really so just go for 12mm - trust me)
anyway here are the pics that should be speak for themselves

give us any feedback if you can though chaps.....


azuqG5g.png

&

3iRwplA.png

cheers for any feedback even if I am talking out of my ar$e one more

Just thought if anybody was putting together a gearbox these could come in handy
to suss out what gear ratio you putting in there (in case you forgot or lost the packet they came in)
and also if you got a cylinder knocking about but unsure what barrel it is supposed to be used with etc....

Yes they ain't 101% accurate but imho these 2 quick tests are bloomin' close without all the maths :)

 

EDIT - make that figure aprox 15mm NOT 12mm - my very bad

12mm is piston but aprox 3mm further back from piston is center of O-ring which in effect is where the compression is created

or rather not created until it passes the end of port - therefore it is the O-ring's start & finish or travel is what we are trying to work out

 

So measure front of cylinder to port and subtract 15mm not 12mm - then multiply by 10 = ideal barrel range chaps

 

EDIT - 2018, after reviewing my crap I revised this to 15mm for 0.20's and say 20mm subtraction for say heavier 0.30's

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And who said you wouldn't need math outside of high school...

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I'm all for doing stuff properly when it has to be

but if there is an easier simpler method that works I'll deffo use that

but sod doing an Open University Course just to figure out some stuff in my toy gun

(I get bored at work sometimes and kept doing all these maths and wtf - that simple crap works as well)

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Ugh regret failing maths back in school...

 

Don't suppose you could use your genius mind to create a time machine to go back to the 80/ 90's?

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Just a week would be perfect to win last week's lottery = MY OWN AIRSOFT ARMY

 

Seriously the maths on ratio does work BUT - for "general" chrono/airsoft setup's

eg: this is the maths that in effect gives you the 1.5~1.6 ratio's for the "normal" 0.20's and maybe 0.25's

 

All this bollox can really change when using heavier 0.30's and will be off for say DMR's using .36's

The heavier bb's will need a great ratio of 1.8 to 2.0 perhaps to shift the heavier mass of bb correctly

 

Airsoft Ed made a post about this over volume and there are many articles saying heavier bb's need higher volume ratio

 

As it stands the basic quick check does work I reckon - for 0.20's at the chrono and how most stuff is shipped to run with

However for those players seeking better performance with slightly heavier bb's the number 12 will not work for them

 

These heavier bb's or higher volumes may need a larger number subtracted - eg: 16 instead of 12mm

(42mm - 16 = 26 or 260 barrel with higher volume to push out heavier bb's - but I am guessing this bit atm coz I dunno)

 

Heck I'm no expert mofo but just the numbers adding up or correlating on the 1.5/1.6 ratio and thought I'd inform you chaps

and gear check thingy is coz I hate counting tiny gears and all that crap multiply this n that divide by wtf etc...

 

I'm throwing this out there and if anybody looks into it and gives us some feedback we might all be able to arrive at a good

all round quick ratio checker for normal bb's AND if we get some feedback adapt change the magic number 12 according

to what bb's people use and we may be able to perfect it more for all weights of bb's

(might be increase 12mm by 1.5 or 2mm for each .05g increment etc... but am open to any feedback like I said)

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And who said you wouldn't need math outside of high school...

 

"maths", "secondary school". Where did you grow up, America?

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"maths", "secondary school". Where did you grow up, America?

although I am American, I have been living elsewhere since I was 12. Math was a typo, or mybe autocorrect. And its just habit to call it high school, as my US and Singapore schools both called it that, and my current IB school has PYP, MYP and IBDP, not primary and secondary school.

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although I am American, I have been living elsewhere since I was 12. Math was a typo, or mybe autocorrect. And its just habit to call it high school, as my US and Singapore schools both called it that, and my current IB school has PYP, MYP and IBDP, not primary and secondary school.

 

:D fair play then! Where in the US are you from then? How come Singapore, forces parents? Just being nosey like....

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haha, not forces. my dad works for Abbott Labs, which is a big pharmacutical (pardon my spelling, my ipad doesnt do autocorrect) company, and he keeps getting promoted, so we move every two years or so. I lived in five states by the time I was five, but we set up in Tennessee for 8 years. Singapore was our first overseas move, and now we are about to start our fourth year here in the UK.

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So how do you like it here? Are you near Maidenhead then? I'm assuming as that's where Abbots are....

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Im in Sunningdale, as you should know Lozart :) (think UGL). Its nice here, and I dread moving back to the US for uni, as I dont wnt to lose my sport :(

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Im in Sunningdale, as you should know Lozart :) (think UGL). Its nice here, and I dread moving back to the US for uni, as I dont wnt to lose my sport :(

 

Oh yeah.....duuurrrrrrrr. Sorry having a bit of a "slow" day today :)

 

Can you not do uni here then?

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based off my career options and wants, I am torn between Richmond uni here, and either FIT or UCF in Florida. Also, I have an open offer for an internship in florida, but whether I decide to do that year-round, or just over the summers, i do not yet know

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What are you looking at going into as a career then?

 

To be fair if you already have an internship offer I can see why you're torn!

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im big on CAD/CAM and computer design manufacture. Based my IB diploma around it as well, and have been doing it with Autodesk Maya, ProDesktop, and Solidworks for four years in Singapore and here. Also, as some of you will probably like to hear, I have been to the main Safariland plant in Florda and met with the designers there (thats why I know Bill Rogers amd have so many Safariland products).

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haha, I was thinking we had kinda disrupted the thread....

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Oi - do you two wanna flirt somewhere else or something

jeeeez thought there was gonna be some new findings/results

 

And I thought I was the main thread derailer or hijacker :D

 

Derailed.jpg

 

 

Yeah....sorry about that :)

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Lets assume that there is a magic ratio of air volume for the barrel verses the cylinder, that is the current theory that if we maintain this ratio then we get the best performance. We can define that ratio as follows:

 

MagicRatio = VolumeOfBarrel / VolumeOfCylinder

 

I make a 453mm 6.05mm barrel volume of 16580.93mm^2

I make the volume of a non ported cylinder as 8111.17mm^2

Making the ideal ratio 16580.93 / 8111.17 = 2.044

 

The volume of cylinder is radius ^ 2 * length.

 

Lets assume a 6.05mm barrel for simplicities sake and a variable length we get VolumeOfBarrel= 36.6025 * BarrelLength

The VolumeOfCylinder uses the same equation for the volume of a cylinder. A full length cylinder has 58.75mm of usable length but this varies with the port but its inner radius is going to be 11.75mm (not a bore up). So we get 138.0625 * LengthOfCylinder

 

If we substitute those into the equation:

 

MagicRatio = 36.6025 * BarrelLength / 138.0625 * CylinderLength

 

The MagicRatio we know from the considered optimal setup so we can use that to eliminate the term:

 

2.044 = 36.6025 * BarrelLength / 138.0625 * CylinderLength

 

Now we need to rearrange it a bit

 

138.0625 * CylinderLength * 2.044 = 36.6025 * BarrelLength

282.19975 * CylinderLength = 36.6025 * BarrelLength

 

And divide by 36.6025

 

7.71 * CylinderLength = BarrelLength

BarrelLength = 7.71 * CylinderLength

 

So your equation is off a little bit, but it may all depend on cylinder volume estimates and the thus the magic ratio. Still 10x is only about 25% off of the actual magic value I derive from the underlying volumes and in this case we can see the volumes of each is linearly scaled with each other, so we don't technically need to use R^2 in the end so long as we can fix both the inner barrel radius and cylinder radius. The later is basically fixed and the differences in volume from a 6.01mm inner barrel and 6.08mm is just 2.3% so its a small factor we can ignore. A 6.23 is actually quite a difference, more like 7.4% but its still a relatively small error when we consider we have to choose between 293mm and 353mm barrels which has a much larger difference.

 

(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)

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(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?

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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.

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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.

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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)

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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)

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