Understand Cylinders and Ports for AEGs
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- Опубліковано 2 лют 2023
- Chris Trivane at Replay Airsoft examines various cylinders and port configurations to discover what gives the best performance for airsoft AEGs
#airsoft #gearbox #cylinder #porting #aeg - Розваги
Mechanical Engineer here, just wanted to say great video and testing process as well as that your theories are very close, with merit to both. The reason for your results is that the piston is always going to be traveling at its maximum speed right before the piston head slams into the cylinder head. Like you said, the un-ported cylinders gain compression immediately and this doesn't allow the bb to take advantage of the pressure peak, as they exit the short 200mm barrel long before the piston slams home (aka, max pressure, which = max fps). This can be thought of as similar to, assuming your fist (the bb) is allowed to travel equal distances in both cases, trying to punch an object (the bb) with your fist already on the object and not drawing back any vs being able to fully draw your fist back and "wind up" for the punch. In the second case, your fist actually has time to accelerate without resistance before depositing its energy in the object and thus will make the object move much faster and go further than in the first case. The same rules apply to the piston and bbs. The higher fps on the longer ports ending at the same length of the port from the cylinder head is likely due to the piston head O-ring encountering less friction from the cylinder and thus is able to accelerate slightly more. Hope this helps make sense of the results.
Such a clear explanation, thank you! Does it mean that if we will swap the barrel, it will change the distance for travelling so the results can become worse?
@TheXoJIog potentially, yes. The results are usually pretty negligible as long as you're +/- about 50mm from the "optimal" barrel length for your cylinder, although the biggest issue with running a barrel way too short or too long for your cylinder is undervolumimg (barrel too long) or overvoluming (barrel too short). Both undervoluming and overvoluming will cause accuracy issues with a setup if it is not tuned correctly for the weight bb you want to use. You want to get a ratio of cylinder air capacity to your barrel capacity that is optimal. There are many guides out there on this, my favorite being from TheAirsoftTech here on youtube. In short, yes it will affect the fps as long as there are no air leaks in your system as the goal is to match the cylinder and barrel to each other.
This makes sense, thank you kind sir.
@@anthonyseverino8292 No problem. I'm always glad to help out.
so essentially by fine tuning port size and position with barrel length and piston travel you can make your aeg the most efficient@@blakeetter2200
air compression starts at different piston velocities so the bb start accelerating at different pressures (full cylinder = lower, higher when the port is closer to the cylinder head), which is relevant in this case because the barrel is short and the bb can't accelerate much in the barrel
Thanks for taking the time to put this together. What I would say is you're simply finding the optimal cylinder for that barrel length and BB weight. What you will find if you do some more testing is that heavier BBs need more cylinder volume to achieve the same muzzle energy as a lighter BB with the same barrel length. When Tokyo Marui created different cylinder ports for all their different lengths of barrel, they based the matching of the cylinder volume to barrel length on a 0.2g BB weight. As soon as you go above 0.2g, you will likely see your muzzle energy tail off when using Marui's ratios.
I’m a newbie and just getting into airsoft, currently repairing a gifted old m4 , watching these videos helps so much, I love how detailed your explanations are and really does help me and others I’m sure how to understand the purpose/how everything works, thank you!
I am a mechanic what you are dealing with here is a thing called “volumetric efficiency” give that a UA-cam/google.
It’s not all about how much volume you have in your cylinder at that RPS but how much air you can get into the cylinder. No port cylinder the only place air can enter is the nozzle and around piston head. Meaning you are pulling a vacuum at that speed. (To help on a full cylinder you can modify the piston head to pull less of a vacuum)
What I would think would make a very large difference is doing this same test with same parts and precooking maxed out with gun set to SEMI. To give time for the air to full the cylinder.
I could be wrong but that test would help to prove that theory would love to see that thanks for the great video.
Nah, you can get ported piston heads that work like a one way check valve so air can come in from that direction as well.
im loving the tech videos. ive watched every video youve made and can clearly see that you are one of the most knowledgeable airsoft retailers ive seen. i am certain i can trust the information you put out to the public which is often times not the case. so i appreciate your hard work and non bias. that why i bought my stuff from replay. keep up the awesome tech content. cheers
Barrel length matters and determines the port location
470mm+ closed
407-470 tip hole
357-369 4/5
229-351 3/4
94-208 1/2
too short of a barrel and no ports your are basically vaccuming the BB as pushing it, with a long barrel then yes your original hypothesis holds true since you need as much volume as possible.
so what do you suggest i do with a 229mm barrel? which port type should i go for
@@danielschmidt1990 3/4
Regarding the results, such low spring will act like that since it will encounter less resistance on a ported cylinder. when the piston head starts to seal and compress air, it already has momentum so it outputs more pressure, at some point you will have a spring that will surpass the terminal velocity of the mass of the piston so you wont see this result, meaning the piston will accelerate at the same rate no matter if ported or not ported. you should consider using a longer barrel to match the non ported cylinder volume and heavier bbs that will need more pressure to move and reach the optimar velocity inside the barrel.
it is like if I start inflating a bike tire vs a body builder, if we had a ported inflator you could imagine at first it will be super easy for me to push hard and accumulate momentum and I would gain pressure output (given it is just a bike tire aka low volume barrel), the body builder will have such force that if the inflator has a port or not it wont matter, he will push at the same speed resulting in the same pressure, the key aspect here is the volume required to accelerate a given bb mass inside the barrel, if you have low volume at a given stable pressure your bb will reach a speed that might not be optimal, same happens on overvolume vs short barrel, you are pushing too much air that the short barrel cant use.
this is basically how joule creep works.
Absolutely awesome, these are the sort of tech vids one needs 👌👍
The barrel has to be longer to get a higher fps with larger volume cylinder.
From my own research I found that any inner barrel longer than 400-410 mm requires a full cylinder with no porting for the best results. Good informational video man!
Makes sense to me. I had an inconsistent Cybergun F2000 with a cheap V3 gearbox. The cylinder had a port. The nozzle was cheap, without an O-ring, so I replaced that for a proper one. Piston and cylinder are replaced as well, without a port. The F2000 now shoots very consistently and more quiet. It has become my dream assault-rifle, after all this time that it caused me some grief.
I also applied the hack with the little machining within the "breech", where the BB sits before it gets blown through the hopup-unit. All it took was a 6mm drill and a little drilling, machining something like 0.1mm of an indentation. This made the feeding very reliable. No more double-feeding at all. Never.
Excellent, data driven analysis! Thank you for showing everything and taking several samples. I'm about to watch the follow-up video, and I'm very curious to see if the hypothesis I made up in my head will match the results you get. For brevity, I'm betting that there will be a positive correlation between barrel length and cylinder volume. In other words, longer barrels will perform better with smaller ports, and shorter barrels will perform better with larger ports (or ports further forward).
Amazing and very interesting, yes please test more variables!
Very interesting results. Thank you
video that i search for so long
thanks
Volume to barrel length ratio.
Theairsofttech talks about it in 1 of his video.
Really like your videos 👍 waiting for more 😊
Nice video, very helpful and Im learning a lot
Awesome video 🎉
very good testing what I really need, thanks
Thank you for this video as I also wanted to investigate this but I don’t have your equipment or materials.
Judging from your results, I agree with your theories.
I think the reason for higher velocity with larger ports is that the piston reaches higher speeds when released due to the exhaust ports offering much less resistance than a closed cylinder.
This added speed helps impact the air in the closed section of the cylinder rather then “push” when if the cylinder was closed.
I think it has also something to do with the piston head design which provides a seal when the piston is moving fast. The faster the piston, the better the seal.
If you balance this, you get to get more out of the “shorter” closed cylinder even though technically you are pushing a smaller air volume out.
In other words, with a closed cylinder you may be pushing out more air but at a slower rate.
With an open cylinder you push out less air but at a much faster rate. This will in turn result in a better energy transfer to the BB.
With the closed/smaller ports cylinder, you might get an advantage with longer barrels as you will have more length over which to transfer the compressed air energy to the BB where as an open port cylinder may lose power with longer barrels as the piston may hit the head before the BB leaves the barrel at which point, the barrel becomes resistance rather than power transfer.
It’s a matter of balance and tuning in the end as you said 👍🏼
love the videos post more!!!!!
What I did was calculate my barrel internal gas volume based on length +10mm(to compensate compression and possible vacuum created by lack of gas) .. Then I converted that to the cylinder volume, where I custom cut the port hole starting at that volume. My fps is 400 with a m110 spring and only a 1-2 fps difference per shot.
i miss playing at replay.. got your patch out here on my helmet since i moved to Washington..
Many surprises.
Increased FPS is seemingly the desired outcome for any airsoft cylinder config but BB speed is a measure of transferred energy, not a true measure of a system's efficiency. While Fps may give you a very good idea of this - air directly propelling an object is a very energy efficient system, you might get a better insight into what is going on by measuring aspects of the configuration's air output - volume, psi, airspeed, etc. Perhaps there's some important dynamics to consider, eg spread between high and low fps as the system finds a thermodynamic 'gold zone' for piston efficiency at full auto that a larger port/moved will affect, for example? These factors might be a little difficult to test, but here's some ideas: maybe a balloon at one end for volume, maybe the air speed can be gauged with a small volume anemometer, and air pressure wave by deflection of obstacles at tip of barrel? Median fps, voltage/amp stats could be also useful and help give a broader idea about cylinder performances. Also would recommend that you place the gun in some sort of fixed support so that its position in alignment is consistent with the chrono. Good vid, thanks for the posting!
Very informative, thank you. Can we assume then that the volume of the barrel and the volume of the cylinder (measured from the front to the start of the port) should roughly be equal
Did you notice that the un-ported/smaller ports closer to the rear were louder than the ones with the ports closer to the front of the box? My theory is that the un-ported/more rearward ported ones allow for more air volume to push the BB, as the piston builds compression sooner (longer) and the ones ported more to the front are pushing less. I suspect that if you use an un-ported cylinder and increase the barrel length you may see gains in fps, vs the short 200mm. Also, if the piston is pushing more volume, the spring effectiveness is lessened as it is doing more work. I believe that the port location/size needs to work directly with the barrel length, similar to dwell time on an HPA gun to match the volume of the barrel. At a certain point you're just pushing more air out the end with no more velocity gain, and the gun gets a lot louder at the muzzle due to the extra air volume. I think what your results proved is that a properly balanced setup will yield higher fps as the gun isn't fighting itself with a given barrel length, spring, and piston sleeve. Again, just my theory. I appreciate you taking the time to do the testing!
Interesting. How many ports are in the piston head? Have you tried the test doing single shots with time between shots. I'm wondering if it takes time for air to get in front of the piston? As you say this is not what you expect.
On my dmr builds on swapping out a 3/4 cylinder to a full on a 370mm tight bore barrel I've gone up 27fps with .36bbs.
This reminds me of porting my two stoke race bikes. Pistons are pistons after all. Do they make progressive springs?
Very good video!
Shame you didn't do double test with long and short barrel to see de diferences. But so good!
have you done similar tests with bb's 0.28 and 0.32? I think this will allow you to understand the impact more.
Higher fps with port is because the piston can accelerate faster when it has more free flow of air and is not shoving it all out of the nozzle from the beginning, also helps rate of fire because the piston can go backwards much faster
Also bb weight has a huge impact on the fps with different barrel lengths and ports
It probably works similarly to a two stroke motor being the port is where the air would come in to the combustion chamber due to the vacuum being created my the piston going backwards that quickly fills the cylinder with air I would also say the barrel length has something to do with it being like the exhaust system in a motor
Im guessing you get higher FPS with the last cylinder because of the barrel length, I suppose that the barrel not being too long it doesn’t need big amount to air volume to push the BB out, but as the port is higher the piston has more length to accelerate? I am not mathematician either but that’s what I can think of, if you use a longer barrel with the last piston I am guessing the BB is going to struggle to get out
I have 450mm barrel i want to have the best compression i ordered new piston and cylinder head, do i need to buy a new cylinder because my stock cylinder is without port?
When are you doing the next tests with barrel length
In a nutshell, the volume of the cylinder has to match that of the barrel in order for the BB to travel the fastest. Too much air decreases FPS because the excess air creates nothing but turbulence (hence significantly more noise) when the BB exits the barrel. On the contrary, too little air and it will not be able to overcome the pressure of the atmosphere, leading to again lower FPS. The volume of the cylinder is a function of the location of the port - the more forward the port is, the lower the volume will be.
Let’s get them views up people ..
Maybe more manufacturers need to standardize to add air intake to their AEG product.
I have a question what kind of gun is this
power of spring/less resistance (ports)/ Volume of cylinder/ Volume of Barrel=fps. Over/under Volume of the inner barrel is a thing
You should perform same tests with 2 ports on each cylinder.
You asked for physics. My theory is the vacuum effect on the cylinders. If it can’t suck enough air into the cylinder on each stroke it will under perform. Just like the internal combustion engine without the combustion.
Just goes to show that in science there is still always another factor to take into account
🇵🇭🇵🇭🇵🇭
PH Here.
How about 363mm military action 6.01 tight barrel
Please give me an idea of what cylinder to use
if you would've used heavier bbs, like 0,32g, and a longer barrell, the cylinders with less volume would've performed much worse. it's always the ratio between cylinder volume and barrell volume, and the mass of the projectile you want to move.
Maybe the piston is moving fast enough that air can't leak out?
Mabe the non ported cylinder has too much air volume and the bb comes out the barrel before it can all be used up in the barrel
Esto tiene que ver, con el cañón... Si todo está bien es solo el cañón y cilindro....
Aquí eh aprendido mas por que pensé que el de 25% era lo máximo que daba fps a hora veo que el de 50% da mejor resultados en tipo mp5
The port on the cylinder is to match volume in the barrel. Too much volume of air will create turbulence as the bb exits the berral. Also, the rate of fire will have an effect on the bb as the piston, even if the head is ported, will draw air from the berral and cause fps inconsistency. All of this was figured out back in the 90s. I'm a little disappointed that this knowledge didn't get passed on.
Volume of air in the cylinder needs to match the length of the barrel. To much/little air - wild grouping and less accurate. Un-mathed version 270mm - 80%port, 300mm- 90% port, 350mm- full. Check out cylinder porting vs barrel length videos.
Love what you doing, you asking exactly my kind of questions. By the way I seen you taking the screen shot of your phone pressing the 2 or 3 buttons there is an easier way with just a swipe of your palm - see video ua-cam.com/video/JEnmB0nGXWY/v-deo.html
Suprised
The port increases fps by relieving the vacuum on the backside.