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Ja-bow

It's literally Just A Bow.

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#1 QuidProNihil

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Posted 03 March 2010 - 02:31 AM

Thanks very much for the validation; hopefully my stay here will be longer than some.

This, I hope, will come in handy to someone. Before I go on to the instructions, let me answer the question at least one person will ask...


But WHY?
Recently, the friends of mine who Nerf have (unfortunately) become incredibly fond of swordplay. Not one of them will head to a gathering without one (or two) at this point. This has led to them creating their own "round", or sometimes even phase of a round. They call it "Getting Medieval". At this point, blasters are scrapped altogether, in favour of some good old fashioned beating on one another with swords. All good fun, but fairly anathema to Nerf, in my opinion. What can I say? I'm a fan of projectiles.

That said, the arms race began. I put together a knife out of a wire hanger, cardboard and duct tape for Florentine; I came up with a tsai for deflecting (or capturing) swords. I fabricated a shield from a pizza box. I took a length of 1/2" PVC and some suction darts for a very crude atl-atl. Finally, I decided it was time for something I could more accurately aim. That something is what I'm calling the JA-Bow --- the Just-a-Bow. That's all this is; just a bow.


A quick caveat...
If you are unfamiliar with at least the very basics of archery, this is something you probably won't want to build. It's not at all difficult to use, but if you're not at least a little handy with a real bow, you're probably going to hurt yourself.



Alright, so what do I need?

- 3 pieces of 1/2" PVC, 2' long

- 2 1/2" PVC (2-way) joiners

- 1 1/2" PVC "Cross" (4-way) joiner

- 2 10" bungee cords - I found these at Lowe's Hardware in a 4-pack. Always nice to have extras.

- a hacksaw

- You may need a pipe cutter, but the hacksaw will work just as well for its purpose.

- Some duck tape & e-tape.

- Matchsticks, or something of a similar width.

- A nail.

- A hammer.

- Pliers.

That's all that's strictly necessary. I used some hockey tape for certain things, but it's not needed.



How do I do it?

1. The very first thing you'll want to do is use your pipe cutter or hacksaw to trim each of the three lengths of PVC by roughly 2". This won't need to be exactly 2", as long as it's the same on all three pieces (or at the very least two of them).

2. Saw one of those pieces in half lengthwise. Down the middle, all the way through. This took me a while because I have a very dull blade, but it should be no problem otherwise. This isn't going to have to be perfectly straight, but the straighter it is, the better.

3. Take the two halves, put them back together, and duck tape one end so that there's a small gap between the two of them. --- this is where matchsticks come in handy to hold them apart a little bit. DO NOT tape the other end yet.

4. Now stick the other side (the one you didn't tape) into one opening of your cross coupler, so that if you were to lay it on the ground, the gap would not show. Put the other two pieces in adjacent openings:

Posted Image

5. Using your hammer and nail, bust a hole towards the top of each of your regular couplers. Stick them on the ends of the non-sawed lengths of PVC, with the hole you punched on the further edge from the pipe.

(Ignore the extra opening; I didn't have a spare 2-way to demonstrate)
Posted Image

6. Set this monstrosity aside for now, and grab your bungee cords, and link two of the ends together. Use your pliers to bend the metal bits securely to each other.

7. The other ends of your bungee cords are just made for those holes in your couplers. Link ONE of them through, pinching the ends again:

Posted Image

8. Now, the trickiest part --- slide the whole bungee assembly through the gap in your center pipe. This might take some creative prying, but it can be done. Ultimately, you want the two linked ends of the bungees inside of your hacksawed PVC, and the loose end connected in the same way as the other side.

9. I wrapped some duck tape around the cross coupler and the sawed PVC, continuing down the PVC for roughly 2". I then covered this in e-tape for about 3". The first section from the cross coupler was fairly light on layers. The next section was very heavily layered, and the last was right in the middle. This will become clearer to understand in a moment.

10. Take some more e-tape and wrap it around the metal "coil" that holds the links to each of the two bungees by your hacksawed PVC.

Strictly speaking, you're done at this point, and it's ready to go. Drop a streamline into the open end of the cross coupler, draw back, and fire away. I chose to e-tape the hell out of mine, but this is, for the most part, purely cosmetic.


My finished product:
Posted Image

Collapsed:
Posted Image


Odds and ends...
The line of red e-tape just before the cross coupler is what I call my "bloodline" -- the idea being that if the bungee starts to cut into that, I'm going to bleed. You may need to re-tape outside of that area every once in a while, but with a very thick layering of e-tape, it'll be every once in a long while.

I wrapped some hockey tape just under the cross coupler for a handle, and at the very end of the hacksawed PVC. I tend to take my time aiming it, so I like to be able to rest my hand on it.

As you can see, it can break down fairly easily for storage/transport, etc. These pieces, when held together, also make a fairly effective defensive tool against those pesky swords.

The JA-Bow works wonderfully with streamlines that LS's or other clip-system blasters chew up. I don't make stefans, so I can't accurately say how well they'd work. --- I tried stuffing some FBR in there, but it's a bit too snug to work proper.

I've managed to squeeze some more power out of it by twisting the PVC so that the bungees twist around them. Never done more than two rotations without the pipes trying to run away, however.



Ranges?

Can't take a good outdoor range test at the moment, but indoors, I can stand at one end of my 80' apartment and hit the other wall. The dart does start to fall by the time it hits the wall, so I'll give a conservative estimate of 60'-75'. Not bad for what it is, if I do say so myself.

Hopefully this will be of assistance to someone. I know this is clearly not for everyone, and not something I'd bring to a legitimate war, but certainly a good projectile weapon against my sword-toting friends.



Questions, comments, flames?

Edited by QuidProNihil, 03 March 2010 - 02:33 AM.

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#2 Zorns Lemma

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Posted 03 March 2010 - 02:10 PM

Kane built a similar physical propulsion bow, but instead of using a bungee, he used the elasticity of PVC pipe to power it. Clearly this method is probably much more reliable. However, one thing you can do is nest some tube so that you can clip on an N-strike magazine so you can fling darts 50 or so feet as fast as you can "prime" it. And since you're using physical propulsion, building anything airtight is completely irrelevant.
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#3 billyblue888

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Posted 03 March 2010 - 04:46 PM

You could probably add more bungees but then it might not work with streamlines. Anyways I like it.
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#4 Stud Muffins

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Posted 03 March 2010 - 06:49 PM

And since you're using physical propulsion, building anything airtight is completely irrelevant.

As I believe the MEGAHAMP proved in the shop tests. I might have to make one of these bws for myself and use it suring a round. (I love using shit guns and inaccurate stuff like this. Once got a barrel tap with an eliminator. Good times...)

Edited by Stud Muffins, 03 March 2010 - 06:49 PM.

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#5 HOTH

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Posted 03 March 2010 - 07:32 PM

Thats pretty cool. Also, with a first post of such caliber, I"m sure you'll be here longer than some.
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#6 KaneTheMediocre

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Posted 03 March 2010 - 09:16 PM

The 1/2" CPVC gets plenty of tension, and on its own could do 50-80 feet flat, with just as much reliability as this bungee powered contraption. However, adding the plunger rod (which is necessary for the clip feed, unless you do something incredibly creative structurally), cuts the available stroke length in half, AND adds lots of weight to what is otherwise just string and dart. So while the clip fed Autobow is cool as hell (I swear, I'll post a writeup soon...), it probably doesnt do better than 20-30 feet of range. I'm going to try using PVC, or maybe 3/4" CPVC, to try to compensate for the inefficiency with greater bow tension, but unfortunately, adding a clip is not a free lunch.

Quick note- Airflow DOES matter slightly--if you make your system airtight, and the plunger doesn't reach the end of the tube, you will actually LOSE range (or prevent function altogether!) due to the vacuum created between the dart and the plunger as they separate. For this reason, I used PEX tubing as the plunger rod.

Also, Muffin, although I am very proud to have created the Megahamp, and the as yet unseen Autobow, that's about the only connection I can see between the two...

And yeah, good job with having a high quality first post here. It's good to see homemades and mods that focus on the fun / cool factor more than war-viability.

Edited by KaneTheMediocre, 03 March 2010 - 09:18 PM.

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#7 A side of nerf

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Posted 04 March 2010 - 06:23 PM

I built a crossbow like this once. The problem I ran into was shearing of the plunger rod because the cords pulled up on it so it went down the tube at an angle.

Edited by A side of nerf, 04 March 2010 - 06:24 PM.

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#8 death by cheez

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Posted 04 March 2010 - 06:49 PM

Hmm.... Seems interesting, almost exactly along the lines of a project I was debating upon doing. The thing I was going to do was use 1 and 1/4 inch PVC pipe, a spring, and a homemade plunger system (though I may just use the HAMP) and get a +bow spring as well as a couple bungies. Once I get the cash for parts I may finish this, but so far all I've got is the PT and the PR, no plunger head or end-caps.
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#9 QuidProNihil

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Posted 09 March 2010 - 04:14 PM

Thanks all for the feedback. :)

I considered some kind of clip system, but scrapped it because, in my humble opinion, it would do more harm than good. Much as I love the idea of not needing to reload after every shot, I just couldn't figure out a way to do so without sacrificing propulsion space - something I've already sacrificed quite a bit more than I'd like to due to silly little things like personal safety.

Nevertheless, in the interest of Science(!), the closest thing to a working clip design I came up with looked like this:

Posted Image

In order to avoid a plunger system that would eat up precious space, the clip would have to be "on top" of the dart-holding PVC, so that the darts could simply "fall" into place. The bungee would then slide "under" the dart.

Once fired, the next dart would then fall into the same place.

My biggest issue was finding (or constructing) a clip that would be secure enough to hold darts within itself while not in use, but be loose enough to let darts fall while attached to the bow itself.

Placement of the clip would not nearly be as straightforward as the picture implies - I tend to tilt my bow. I also tend to point it downwards after firing; a perfect recipe for wasting darts.

If I do think of something, and in fact build something that works for me, I will of course update the thread to reflect that. As for right now, however, it works for what I need it to - hitting an opponent before they reach me with their sword.

_____

Also, I'm very interested in taking a look at this PVC-tension bow. Where should I look for that? I tried searching for bows before I posted, and mostly found crossbows and +bows. Or is this the "as yet unseen Autobow" you're talking about?
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#10 KaneTheMediocre

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Posted 09 March 2010 - 06:28 PM

Also, I'm very interested in taking a look at this PVC-tension bow. Where should I look for that? I tried searching for bows before I posted, and mostly found crossbows and +bows. Or is this the "as yet unseen Autobow" you're talking about?


Yes, it is the "as yet unseen Autobow", and I'm sorry I haven't posted it yet. I'm on a big project, which should be finished this week, then I'll get on my writeup backlog. There's really no magic trick to using CPVC for tension--slit the ends, and tie a string between the two. To tighten the string, add wraps around the CPVC before coming out the slit again--this will also bend it into the traditional bow shape, as it's the only way for the CPVC to accommodate the shortened string length between the ends. The tricky bit is attaching this to your barrel/slot/whatever, which can be achieved with a PVC cross, shooting darts through the middle (the bow is in 2 parts in this case), or by having the barrel rest on top / to the side of the bow itself. The cross is the more elegant solution I think, but you definitely need to reinforce the hell out of however you couple to the cross.

As far as clips go, mine was made to take standard N-strike clips. I cut a breech out of some aluminum that's .527 ID .625 OD, and made a hot-glue mold of sorts to hold the clip (again, sorry there's no writeup yet, I'll cover this in greater detail then. The string could NOT go past the clip, so I about a foot of 1/2" PEX tubing as the "plunger". The weight and reduced draw to accommodate the clip in this way REALLY kills range--I got about 25 feet on average, and the occasional fat streamline would stick in the barrel and barely make it 10 feet. Larger bow-tubes for greater tension will probably help, but I expect that this design will never get past 50-60 feet without requiring a real archer to draw it.
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#11 Naes Draw

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Posted 10 March 2010 - 06:59 PM

Out of interest, how exactly did you do the atl-atl? The way I'm thinking wouldn't be very functional.
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#12 QuidProNihil

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Posted 10 March 2010 - 09:19 PM

Out of interest, how exactly did you do the atl-atl? The way I'm thinking wouldn't be very functional.


I took a 2' length of 1/2" PVC, put a whistler (or suction) dart into one end, and just kind of..."flicked it", is the only word I can justifiably use for the motion I did.

Nothing else is technically required, though I suppose you could put some kind of stopper a few inches in if you're dying to use streamlines. I used the other kinds because they'd not fall inside the PVC. Also, I "built" it in the middle of a round out of frustration, so there wasn't much I could do in the way of design. I'm sure there's a better way, but I don't know that it's even worth the effort.

Range was, at times, fairly impressive for what it was. Accuracy however, was shaky at best.

I don't recommend it.
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