QUOTE(skcs1985 @ Sep 26 2008, 09:55 PM)
hop up can be adjust on AEG and GBB guns
Hop-up & the Magnus Effect
The term Hop-up, short for High Operation Power Up, describes the back-spin put on airsoft pellets and BB's to increase their range and (vertical) accuracy via Magnus effect. Hop-up acts somewhat like the rifling on the barrel of a firearm, but without the increase in horizontal accuracy. Also, being light-weight, airsoft pellets are still affected by wind when fired.
Airsoft hop-up devices apply a backspin to the pellet so that the pressure force acts on the pellet opposite to the direction that gravity is pulling it. This causes the pellet to fall less over a given distance than it would without the spin applied to it.
In airsoft guns this is often implemented as a rubber piece at the rear of the barrel that is thicker at the top of the barrel than the bottom. As the pellet moves past this piece it tends to roll, inducing a backspin. This is occasionally adjustable so that the effect can be tuned to suit the weight or speed of the pellet, and each player's preference.
The primary cause of the apparent lift on an airsoft pellet is the Magnus effect. There is a layer of non-moving air on the surface of the pellet (boundary layer). This is why a golf ball has dimples; this layer acts like ball bearings. In the case of a spinning ball, this layer gets thrown off at an angle. Newton's laws say that in order for air to be thrown in one direction, the ball has to move in the other direction. According to the Magnus explanation, the rotating ball would throw air downward and to the rear, thus giving lift. The air on the bottom of the ball is slowed down, so when the separated air comes back together, it is lower than the middle of the ball, appearing like a comet's tail pointing down. This can be verified in wind tunnels and is very well documented in fluid dynamics textbooks.
You are correct sir, in a simple word, the hop up system spin the BB when it is fired, leading to increase in range of fire. It's all physics. Range of fire are generally determined by two factor; your gun FPS and your BB weight. 0.2 gram BB have better range but less accurate than it's heavier brother 0.25g BB. 0.25, have better accuracy but the trade off are shorter range of fire. My personal favourite are 0.23 g but it is so hard to find 0.23g BB in Malaysia. It was so easy when I was in U.S...
Added on September 27, 2008, 9:39 amQUOTE(skcs1985 @ Sep 27 2008, 02:39 AM)
errr can we change the term from "gun" to other thing?
like replicas?
i feel like we are being watched lolz
I second your opinion sir. Instead of the term "gun", let's change it into less appealing term to avoid extra attention from unwanted party.
This post has been edited by WarHawk: Sep 27 2008, 09:39 AM