What's Hop Up?

senordingdong

There's a setting on my gun to change the 'hop up'.
What does it mean and what does it do?

TheDoc

its like adjusting accuracy, i think

kdouglas

As per wikipedia:

wikipedia wrote:

Hop-up & Bernoulli's principle

The term Hop-up describes the back-spin put on airsoft pellets and BB's to increase their range and (vertical) accuracy via Bernoulli's principle. 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.

Bernoulli's principle as applied to an airsoft pellet is as follows. As a spinless spherical pellet flies along its trajectory through the air, the pressures on all sides of the pellet are equal because the air is traveling the same velocity relative to the surface of the pellet. If a spin is applied to the pellet about an axis perpendicular to the velocity vector (for example a backspin) the air will be rushing slower (relative to the pellet surface) on the side that is spinning away from the velocity vector and faster on the side that is spinning towards the velocity vector. Bernoulli's principle says this difference in fluid velocity implies a difference in pressures, which is a force that will cause the pellet to move in a direction perpendicular to the velocity vector.

Another 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.

Head_Hunter

In short, it makes the BBs fly much further, roughly twice the distance. However some clones have very crappy hop-ups which have little or no effect.

senordingdong

Head_Hunter wrote: »

In short, it makes the BBs fly much further, roughly twice the distance. However some clones have very crappy hop-ups which have little or no effect.

Is that not against the rules?

If you increase the range are you sacrificing something else in turn?

Tigger

nope hop up is awesome with the little power we have to play with

Shiva

senordingdong wrote: »

Is that not against the rules?

No...the energy actually decreases slightly....you're just applying that energy to the BB in a more efficient way.

senordingdong wrote: »

If you increase the range are you sacrificing something else in turn?

You sacrifice a small amount of energy, usually the rough equivalent of about 10 feet per second on a .2g BB. The hop-up rubber slightly slows the BB as it applies the backspin, but although it reduces the energy, it uses it much more efficiently and you gain greater range and accuracy.

So in effect, less is more

senordingdong

Ok, and is this something I should leave alone untill I learn more about it or is it something anyone can do?

Head_Hunter

Most people use hop-up because without it the range is only 20-30M.
The only sacrifice I know of is slightly less horizontal accuracy. Maybe a very slight decrease in FPS too as the BB hits the hop-up rubber on its way out the barell. You won't be breaking any rules by using hop-up.

Head_Hunter

Shiva wrote: »

No...the energy actually decreases slightly....you're just applying that energy to the BB in a more efficient way.



You sacrifice a small amount of energy, usually the rough equivalent of about 10 feet per second on a .2g BB. The hop-up rubber slightly slows the BB as it applies the backspin, but although it reduces the energy, it uses it much more efficiently and you gain greater range and accuracy.

So in effect, less is more

Damn you beat me to it Shiva!

Shiva

senordingdong wrote: »

Ok, and is this something I should leave alone untill I learn more about it or is it something anyone can do?

Not at all - feel free to play about with it.

Take a couple of shots with the hop-up fully off, then turn it full on, and take a few more.

You'll probably notice the BB will curve upwards after about 20-25 metres. Just play about with the setting until the BB flies straight for as far as possible. Hop-up is something you'll probably find yourself adjusting on a regular basis.

Just be careful to turn it fully off when you're cleaning the barrel, or you could damage the rubber.

o1s1n

senordingdong wrote: »

Ok, and is this something I should leave alone untill I learn more about it or is it something anyone can do?

It's very easy to set up. Try putting it on the middle setting and work from there. What you're trying to find is the longest distance the bb will travel without arcing up in the air.

With hop up totally off, you won't be getting any good range at all.

kdouglas

you can learn about it by trying it. Simply adjust the hopup until you get the longest/straightest BB flight path you can. Too low hop and the BB will drop early, too high and it will veer up into the air after 50ft or so, you want to get it somewhere in between. Be careful not to turn up too high aswell as this can sometimes cause a jam.

senordingdong

Yeah, from what I could understand of my Chingrish instructions, jams are common when you mess with the hop up? No?

o1s1n

senordingdong wrote: »

Yeah, from what I could understand of my Chingrish instructions, jams are common when you mess with the hop up? No?

If you start getting jams when you're testing it then put the hop up down a bit lower. It's all just trial and error really.

senordingdong

Ok, I get ya. I was just afraid that the errors in the trial and error could have serious consequences.