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Barrel Extension Idea


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#1 spaceman

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Posted 28 September 2006 - 02:44 PM

If this'll work or not, I really can't say, but either way I'll probably be trying this tomorrow night. Also, if this has already been posted, my bad; I couldn't find anything via search.

Most of us know that adding a barrel extension requires a bit of balance between length of the barrel and range. If the barrel is too short, you won't be getting the maximum performance out of your gun, while if the barrel is too long, the gun can't put out enough pressure behind the dart and you'll essentially create a vacuum within your barrel (dart never leaves the barrel).

Well, here's an idea to be able to find that (near) perfect length the good old fashion method of trial and error (yeah, I'm working towards my mech. engineering degree; future looks bright for the world :D ).

1. First, use pvc pipe or some other material that you can easily drill holes into and make it overly long for the gun.
2. Next, attach barrel however you'd like to your gun.
*Now if the dart gets stuck in your barrel (by the vacuum)...good, it's long enough.
4. Then drill a single hole into the top of your barrel about a half and inch from the end.
5. Fire again.
6. If the dart still gets stuck, then measure another half inch from your last hole (still only drilling through the top of the tube, not all the way through) and drill again.
7. repeat steps 5 and 6 until your dart not only leaves the barrel, but also gets maximum range.
*if you drill too many...fill one. may I suggest duct tape.

My theory here is that once the pressure maxes out within the barrel, the trial-and-error method will allow you to find right where a hole is needed to create equilibrium and allow the dart to then coast on the air still beneath through the rest of the tube giving you max range and accuracy (the longer the barrel = more accuracy).

Now, I know I'll have to find a way to clean off the hanging material from the drill that could catch on the dart as it passes the holes, but I think a little sand paper and a thin stick could do the trick

I'll post what happens tomorrow night soon. I'll probably use a NF and a modded secret strike (mod doesn't effect how it shoots, just how I can use it...also post later).

peace
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#2 Jergling

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Posted 28 September 2006 - 03:46 PM

But what would a longer barrel do, I mean, there are two factors here.

1. A dart should not have to pass fully through a barrel, this was the fatal mistake nerf made in the Ls

2. without the factor of a dart passing through the barrel, there is no reason to elongate it.

I am not inducing a flame here, I just don't feel that longer barrels serve a purpose, only tighter-more pressurized-barrels
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#3 monkey with a nf

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Posted 28 September 2006 - 06:01 PM

When the air pressure wave is going down the barrel, it accelerates until it is equal to the outside pressure, then starts to slow down. You want it to be going as fast as possible when it hits your dart, so adding a longer barrel lets it accelerate more. Adding too long a barrel slows it down. I'm not too sure about the longshot, though.
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QUOTE(Pineapple @ Sep 12 2007, 03:13 PM) View Post

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#4 AssassinNF

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Posted 28 September 2006 - 07:06 PM

If the barrel is too long, the friction of the extra length of the barrel is a major factor as well. I doubt that drilling holes will change anything, but it's definitely an interesting idea. Good luck with that.

With the Longshot barrel, however, it is just empty space that the dart goes through. The only real barrel is the 3" one that the dart is in before it fires. As far as the barrel goes, the longshot is just a very complicated night finder with alot more power, like all Nerf guns. There hasn't been a Nerf gun with a real barrel that I know of.

Edited by AssassinNF, 28 September 2006 - 07:11 PM.

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Probably dead by now, or something.


#5 spaceman

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Posted 28 September 2006 - 07:44 PM

If the barrel is too long, the friction of the extra length of the barrel is a major factor as well. I doubt that drilling holes will change anything, but it's definitely an interesting idea. Good luck with that.


I've actually thought about that as well, though I don't have a definate solution there just yet. I'm thinking silicon spray and experiment with lengths. This may end up just as an initial test to determine the right length without having to calculate anything and then make a second barrel out of brass or whatever you prefer at that length.

peace
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#6 Draconic74

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Posted 29 September 2006 - 01:05 AM

hello, im new, but ive already made a small mod for my titan. i have refrained from posting until i had something to post. so here it is. i am pretty sure that i have worked some kind of calculation for optimum barrel length. supposedly, the air keeps going until it reaches atmosphereic pressure. so if the barrel is cut off right before that, i was pretty sure that it would have the most acceleration time without being sucked back by low pressure. heres what i came up with:

Tp=Titan pressure (unmodded titan air pressure from firing)
Ap=atmospheric pressure
L=barrel length
Rp=release pressure (pressure in barrel when the dart exits [should equal Ap])
BV=barrel volume

i found that the regular titan barrel is about 13.47 cubic inches.

Rp=Ap Rp=Tp/BV

BV=L*pi*r^2 + 13.47 (titan barrel)


so i just need atmospheric pressure in PSI and the unmodded titans PSI when fired. by solving for Rp, which requires BV, you should get L.

NOTE: this will only work for the certain mod i did. the mod i did does not require the titan itself to change in any way, the barrel simply gets an exstension. more to come when i finish the rest of it.
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#7 spaceman

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Posted 29 September 2006 - 02:14 AM

Well, first, Welcome to Nerf Haven!
I'll give you kudos for going the extra mile, however I just got finished with 9+ hours of physics and calc homework and can no longer think well enough to check your work. So I'm just going to assume that you're right at this point. Well done. A++ :)

How'd the mod work out for you?

peace
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#8 Draconic74

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Posted 29 September 2006 - 10:03 AM

First of all, i checked with my dad, and he said it wouldnt work. But im going to completely disregard that, and say it does. The new mod i have on the Titan works ok, but i found that it shoots less. The rubber on my stock darts are rubbing the walls of the barrel. I havnt had time to get some backing rod, but im going to do that as soon as possible. Other than that, the mod is awsome. Its not practical in a Nerf war, but unfortunatly there arent any around here that i can easily get to. Anyway, the basic idea of the mod is to not mod the Titan and instead add a barrel. So now i have 1 loser barrel and Im working on a four shot. Im sure it will be pretty cool when done.
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#9 spaceman

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Posted 29 September 2006 - 10:47 AM

Why don't you just pull the ends (velcro tip, whistler, suction cup, etc.) off and drop some hot glue + weights (if you want) onto your stock darts?

Instant stream-lined darts.

peace
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#10 Draconic74

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Posted 29 September 2006 - 06:57 PM

Because i only have about 10. That and im getting some backing rod soon. Also, its not the streamline problem, its that the rubber ends are rubbing (big surprise) the sides of the tube. That wil be fixed with the homemade darts.
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#11 spaceman

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Posted 30 September 2006 - 03:00 PM

Sorry guys, but during my massive modding session, I ended up helped everyone else mod their guns/make stefans and forgot to do anything to mine.

When I get some time, I'll post up everything I've done so far including pics from last night.

til then,
peace
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#12 Falcon

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Posted 30 September 2006 - 04:19 PM

I don't think most darts really make a good enough seal to be held in place by a vaccum.

No, I worded that wrong. They make a good enough seal, but a vaccum isn't what's holding the darts back from leaving an extralong barrel so much as friction. If a barrel is too short, all of the air pressure will not have been used before the dart leaves the barrel and it will have so much speed behind it with so little stabilization that it will go everywhich way (often fishtailing) with no hint of accuracy whatsoever. If a barrel is too long, the air pressure will all be used up before the dart leaves the barrel and it will do one of two things:
1) the friction caused by the barrel on the dart wikk keep it from leaving the barrel.
2) the momentum given to the dart by the air pressure will allow it to leave the barrel, but it will lose some range due to the friction of the barrel after the pressure was all expended.

Side note:
DON'T lube your barrels! The lube gets on your darts and makes them sticky. When they hit the ground, dust sticks to them and collects on them. Eventually, you get a massive buildup of gunk inside your barrels. This is firsthand experience talking here. I sucked nearly all day at a YANO early on this year, and it was because my darts weren't always firing. They'd fall out of the barrel like I was trying to shoot a dart out of a scout through my crossbow barrel. It was because there was all sorts of shit built up in there. Nice thought, but it doesn't work.

A barrel of the proper length will not only allow all air pressure to be used on the dart, but it will end right at the point where all pressure has been exerted on the dart so the dart is onlt traveling on momentum after it is out of the barrel. No pressure is lost, and no extra drag on the dart exists. The barrel length at this "point of equilibrium" (air pressure to barrel length) should be long enough to facilitate the optimum firing range of your gun while providing outstanding accuracy (as can be expected from anerf gun, anyway).

To increase the accuracy of a gun without having to lose much range, many people have found that (I'm using brass as a barrel material for this example) once they've found their optimal barrel length, they will then sleeve over the barrel a piece of 1/2" PVC (whether it be Sch 40 or 80 makes little difference. Sch 80 just looks cooler 'cuz it's grey...lol) that is longer than the brass barrel section. This does not add a significant amount of friction to the dart once all pressure has been exerted on the dart and the dart has left the brass; it simply serves to keep the dart on track once it is on its own for its flight path. These extra 5 or so inches of PVC extension help eliminate occasional fishtailings, errtic shots, and other unexpected issues.

This is why I don't like when people put superlong barrels on their crossbows and such:
They've got a nice long piece of brass in there, which is slowing down their dart already. Then, there's this massive piece of PVC over it that goes out so far that it does begin to have an effect on the dart's flight.

You just can't overdo the barrel length issue. It'll hurt your gun's performance. Most of the reason for my crossbow's physical performance level is based around two things:
1) Dart to barrel match.
2) Barrel length.

Once you have it right, your gun (no matter what it is) will work wonderfully well and will allow you to play to your full potential. I've found that a lot of players that suck on the field usually have some gun issues to work out. They're used to working with a gun that sucks, and then start blaming themselves.

So to make sure I have a point here, I don't think the hole drilling thing will really help. Once the dart gets to the holes, it will still be slowing down due to the sides of the barrel, regardless of there being holes there.

Draconic74, welcome to the forums. Way to gow with your first few posts. Props.
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