Where does the bb go

[Donut]

I've got an idea I want to test out, but I need to know one thing before doing it. It sounds stupid but, where is the bb in the barrel?

Does it travel up hugging the upper part of the barrel or down huggin the lower part of the barrel? Or is it dead centered or random? thanks.

[tfwey]

By the laws of physics it would be the bottom of the barrel due to gravity

[tunabreath]

Actually, that's debatable. I think that initially, it would start at the bottom, as it's forced there by the hopup/gravity. However, this creates a space for airflow from the gearbox along the top which would suck the BB up. This in turn causes the same thing to happen again, only towards the bottom, as well as bouncing off the top. So, it's not really one definate position, but I would guess average would be low center due to hopup (working oppositely, since the air is essentially travelling past the BB in the opposite direction as it would outside of the barrel beyond the thrusting air from the gearbox), intermittantly skipping along the insides.

[tfwey]

Assuming there is hop up.......lol

 

on a serious note it really depends how wound up is the hop up.

 

No hop= bottom

High hop= top

Little hop= middle

[ED-SKaR]

the Theory is that it always travels in the dead centre. imagine the air pushing it down the barrel as an air cushion, the air goes around all parts of the BB in the same way (top side bottom).

In the time it takes for the BB to pass through the barrel gravity is neglegable.

 

HOPUP I think wouldn't make it go to the top or bottom, because a spun BB acts on the benuelli (sp) princaples. and they dont apply in confined spaces. however if it does take effect if its high it will touch the top and low it would touch the bottom(only if gravity is a factor)

but remember, the whole point of hopup is to make the BB go in a straght line, not curl up or down.

 

 

 

please feel free to correct me. my Physics A-level was 2 years ago.

[Donut]

Anyone got ideas? or math? Or a way to figure it out?

 

My plan was to "rail" the barrel, since we all know that rifling doesn't really apply to airsoft, so instead of a smooth barrel I'd mod a barrel to have a sort of rail to stabalize the bb, I've got an idea how to do it, just don't know where to do it. The outcome (in theory) would increase horizontal accuracy but lower fps (but that can be compensated with stronger spring/parts)

[tfwey]

Bla was never to good in physics

[SilentSerpent]

I've done A-level physics, and Ed-skar's explanation seems by far the most plausible to me, although it's possible tunabreath's idea may be correct, but i can't see how the bb would retain it's spin from the hop if this were the case, as it would be hitting the top/bottom of the barrel.

 

SS

[Pablo]

I agree, I'm pretty sure it travels own the centre (although I failed A-level physics)

[Donut]

Interesting... any other ideas?

 

Or better yet, any one got a clear barrel and a high speed camera?

[SilentSerpent]

i think that's unlikely, trust me, due to natures constant quest for equilibrium, i can see no reason for the bb not to travel down the dead centre of the barrel with an equal cushion of air either side, and what the hell do want to know this for anyhoo?

 

SS

[Calcifer]

Pingpong ball + Hair dryer

= BB goes down centre of barrel ?

 

+ at the speed the BB is going i think gravity would have little effect.

[Donut]

I don't think ping-pong ball + hair dryer would work, reason being AEG's use a small gust of air as opposed to the hair dryer's constant supply, and it's not strong enough to simulate a hop-up to be a good test.

 

But I'll try it anyways, I think I have a close enough sized PVC pipe somewhere.

[Pablo]

Surely if gravity was pulling it down while it was in the barrel, it would simply drop out of the end?

[pillow_pwnage]

Holy *beep*, who would have though that a barrel designed to do this already exist? Its called a TK Hop-Twist barrel. Go buy one.

[SilentSerpent]

gravity takes time to accelerate the bb downwards due to the bbs own inertia, think about it, drop a bb from head height and it doesn't rocket straight towards the ground, it gradually accelerates until it reaches either terminal velocity or the floor. then compare the time it takes for the bb to accelerate with the time the bb is in the barrel, then look at the fact that we know compressed air cushions can overcome gravity (hovercraft) and you have your answer: the effect of gravity in the barrel is negligable.

 

SS

[Mister Big Shot]

"Surely if gravity was pulling it down while it was in the barrel, it would simply drop out of the end?"

 

Sideways motion does not effect the amount of time it takes for an object to fall to the ground, it only affects where it will hit the ground. If it takes 5 seconds for the bb to hit the ground with a sideways speed 0fps, then it takes 5 second for it to hit the ground even with a sideways speed of 300fps. < According to my Algebra teacher

[Donut]

Holy *beep*, who would have though that a barrel designed to do this already exist? Its called a TK Hop-Twist barrel. Go buy one.

<{POST_SNAPBACK}>

 

That's not the point here...

And from what I've gathered, TK barrels aren't exactly that great. Not saying my idea will work better (if it even works) but at least I'll get to try something.

It's very fun to try out some ideas and mod something. Instead of buying all the parts pre-made and slap it on.

[Thorbard]

Surely if gravity was pulling it down while it was in the barrel, it would simply drop out of the end?

<{POST_SNAPBACK}>

 

No, because its still being pushed forwards at that time. You could try getting a BB and colouring it in with ink, then firing it, and looking down the barrel to see where the marks are. But they might not be visible.

 

I think down the middle is most plausible, but I would suggest that the innacuracies of airsoft stuff, and the fact that tightbore barrels improve accuracy/consistancy would suggest that its fairly random where in the barrel the BB goes, and that using a tighter barrel reduces the possible variance between extreems.

 

And isn't a Hop-Twist barrel a rifled system? Or am I thinking of something else?

[SilentSerpent]

No, because its still being pushed forwards at that time. You could try getting a BB and colouring it in with ink, then firing it, and looking down the barrel to see where the marks are. But they might not be visible.

 

I think down the middle is most plausible, but I would suggest that the innacuracies of airsoft stuff, and the fact that tightbore barrels improve accuracy/consistancy would suggest that its fairly random where in the barrel the BB goes, and that using a tighter barrel reduces the possible variance between extreems.

 

And isn't a Hop-Twist barrel a rifled system? Or am I thinking of something else?

<{POST_SNAPBACK}>

 

please refrain from posting if you haven't a clue what you're talking about, the fact that the bb is being pushed forward has absolutely no relation as to whether or not it is being affected by gravity.

 

SS

[Donut]

Here's a crude drawing of my idea. It's drawn in the case that the bb hugs the top of the barrel.

Something like...

Or maybe it could be open on top and bottom.

As you can see, this should stablize the bb as it travels down the barrel and giving it more accuracy. Just an idea.

 

 

Thorbard, aleady tried it, doesn't realy work, the ink gets smeared off from the hop-up and nozzle and doesn't leave much. (I tried it in a crappy gun so it didn't damage anything.)

[Thorbard]

please refrain from posting if you haven't a clue what you're talking about, the fact that the bb is being pushed forward has absolutely no relation as to whether or not it is being affected by gravity.

 

SS

<{POST_SNAPBACK}>

 

It does, however, explain why it doesn't drop to the floor straight after leaving the barrel. Which is the question I was answering.

 

 

Here's a crude drawing of my idea. It's drawn in the case that the bb hugs the top of the barrel.

Something like...

http://i2.photobucket.com/albums/y22/-Church-/untitled.jpg

Or maybe it could be open on top and bottom.

As you can see, this should stablize the bb as it travels down the barrel and giving it more accuracy. Just an idea.

Thorbard, aleady tried it, doesn't realy work, the ink gets smeared off from the hop-up and nozzle and doesn't leave much. (I tried it in a crappy gun so it didn't damage anything.)

<{POST_SNAPBACK}>

 

Seems a good idea, and a logical solution to the problem, but I'm not sure if it will work. I guess if the BB is consistantly in one part of the barrel it would work, but what advantage does this have over a normal tightbore?

 

As for the ink thing, sorry for being unhelpful, it wasn't something I'd tried, having had no reason to.

[hsimoorb]

What you seem to be describing is an LRB, or long range barrel. They work on the same principle. The barrel itself is reccesed on the top, by about 1-1.5 mm. The barrel is then offset so that the BB rolls off the top of the barrel, causing the BB to spin, and giving it hop-up. In classic systems this works to perfection. LRB'd guns can get wicked range(100m). Unfortunately the concept only seems to work with classic guns. I don't know the exact reason why that is, but practical experimentation suggests that it won't work with AEGs. I seem to remember hearing that it has to do with the smaller amount of gas used to propel the BB in an AEG.

[SilentSerpent]

Thorbard, nothing in your post explained in the slightest why the BB doesn't drop straight after leaving the barrel, it's simple maths, if the BB is dropping at a certain rate, and travelling forward at a certain rate, you can calculate when it will hit the floor. as it's travelling faster forwards than it is downwards, it will give the impression of not falling during the first 20m or so of flight. in airsoft this gets a little screwed up by hop, which causes the bb to generate it's own lift, negating gravity for a short while. these are the only two things affecting the BBs path downwards, full *fruitcage* stop.

 

SS

[Thorbard]

The post I was replying to:

Surely if gravity was pulling it down while it was in the barrel, it would simply drop out of the end?

 

My response: No, because its still being pushed forwards at that time.

 

OK, so my explanation of that was poor. The physics was correct. You know the physics is correct, because you said the same damn thing.

 

Full explanation:

Even if gravity had caused the BB to move to the bottom of the barrel (which is possible, assuming no hop-up. Possible. I've not checked whether it would happen, and that probably depends on barrel length, and I dont know how far into the barrel the BB reaches its maximum speed anyway) it still has forward velocity. Which means, assuming you're firing it with the barrel somewhere off the ground (most likely) the BB is going to keep going forwards for some distance until it reaches the ground.