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Autobow Mk Ii


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#1 KaneTheMediocre

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Posted 03 June 2010 - 05:45 PM

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The Autobow is a bow powered, clip fed, autoloading blaster, made to fire streamlines from standard nerf clips and drums. Range is 30-40 feet ish, but I'm hoping to tweak the design to fire at least 40-50.


Firing video:



Parts:

Bow
-2 3/4" CPVC Flex rods
-2 1/2" EMT Stubs (~2 in)
-2 1/2" Thinwall PVC sheaths (~3/4")
-1 PVC Cross
-2 10-32 x 1" Screws

Bow Assembly:

1. Superglue the thinwall PVC sheaths to the EMT, nesting the EMT inside the thinwall, such that the ends are flush. The glue is not critical or loadbearing, it's just to hold it in place during assembly.

2. Put the assemblage from (1) in the PVC cross, PVC side first. Make sure that the PVC goes all the way in, bottoming out in the connector. This can be tricky, because the EMT will want to slide relative to the thinwall, even if you superglue it.

3. Put 2 screws, of no particular size, through the cross on each side. Center the holes in the coupling region, so that there is plenty of material on both sides of the hole. This is why getting the PVC all the way in was so critical in (2).

4. File / dremel / whatever any sharp edges from the screw, then wrap many layers of duct tape over the screws for safety and structure.

5. Cut a slit into one end of the CPVC. My slit was only the width of my hacksaw, but somewhat wider will be better (You'll see why when you string up the bow).

6. The CPVC should slide with some resistance over the EMT stubs. I never did anything to anchor mine to the EMT stub, and they seem to stay on just fine.

Breech/Guide
-1 Breech Machined sch80 PVC
-1 Guide Machined sch80 PVC
-1 straight PVC coupler
-1 1/2" x 1/2" Wooden stick.
-Mad hot glue.
-Duct tape

Make the breech and guide per schematics. I have the luxury of a mill and a lathe, if you don't you'll need to get creative about this. I think it could be done by nesting Mcmaster 1658T49 (5/8" OD x .527 ID Al), EMT tubes (.719"ish OD x .625"ish ID steel), and thinwall PVC (.840"ish OD .718"ish ID) Both are made from sch80 1/2" PVC, which is where the .840 OD and .526 ID come from.

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To make the breech hold clips straight, I made a hot-glue mold (the same process is used in the raider-bbb).

1. Put paper under the clip, and fold it out of the way. It's a good idea to have the straight coupler on for this process:

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2. Put the assemblage in a vise, or otherwise prop it up so that you can pour hotglue on it. Make sure you have a clear workspace without clutter which may be damaged by the hotglue, or just get in your way.

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3. Make sure the clip is aligned with the breech

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4. Pour on the hot glue. I usually put something on top of the hot-glue which is friendlier to attaching stuff, or otherwise helps to reinforce, since hot-glue isn't known for its structural strength, or it's effectiveness as a glue. Ideally, all we should ever use it for is moulding to a shape. For the AB, I used a 1/2" square stick.

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Bowstring / plunger
-1 string
-1 3/16" OD, 1/8" ID steel Tube (~1.5 in) (89955K11 is 6 feet for 20$. Might find something smaller/cheaper, but since I can imagine quite a few uses for this stuff, 6' was worth it for me)
-E-tape
-1 PEX tube


To assemble the whole thing, you need to plug the PVC into the connectors as shown in the photo. I prefer to arrange them such that the clip points downwards-. This is absolutely necessary if you want to use a raider drum, but if you're just using clips it looks cooler if the breech faces sideways. And the lefty/righty distinction is moot, because you can turn the AB upside down.

Cut the PEX tube to size. Size the PEX by finding the distance from the front of the slot, to the end of the sch80 PVC. Add 3/4" to that size, and put a hole 3/4" from one end. Chamfer the front tip (far from the hole) so it passes through the breech more smoothly.

To string the bow, put the machined PEX tube into the guide such that the rear hole is visible through the slot. Put the steel tube through the PEX.

Put a knot in a long piece of string, then put the string through the slot such that the knot stops it from being pulled farther. Then feed the string through the tube, and through the slot, knotting the string as before. Wrap the interface between the steel tube and string in E-tape, with gusto. To tighten the string (which gives the bow its shape, among other things), wrap the string around the bow a few times, putting the string through the slot on the final wrap.

More Pics:

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There are a lot of useful bit that I haven't told you, like McMaster numbers, and an alternate method of construction that doesnt require machine tools (purely theoretical at this point). I'll add these later, but ATM i have to get to a mobstacle for CHANO

Edited by KaneTheMediocre, 04 June 2010 - 05:56 PM.

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#2 nerfer9

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Posted 03 June 2010 - 07:47 PM

I don't get the point of this or any the rest of your homemades. I doubt the accuracy of this thing is all that great, the ranges suck, and it looks like shit. I can't see how this would be very useful in a war.
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#3 durka durka

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Posted 03 June 2010 - 08:02 PM

Yet another unconventional, yet awesome homemade. I can't wait to see what's next.

The clip stays in place by hooking on to the outside pipe of the breech assembly, right?
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#4 mike180

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Posted 03 June 2010 - 08:38 PM

I don't get the point of this or any the rest of your homemades. I doubt the accuracy of this thing is all that great, the ranges suck, and it looks like shit. I can't see how this would be very useful in a war.

Thats like asking why use a Recon in a war, because its fun as Hell.
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#5 MindWarrior

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Posted 03 June 2010 - 08:42 PM

My sisters coming back from China, And as an advid archery lover, shes gonna love this! Thanks for the writeup.
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#6 Echnalaid

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Posted 03 June 2010 - 08:59 PM

I love over the top ridiculous weapons. Good work.
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#7 nostyleguy

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Posted 03 June 2010 - 10:59 PM

I don't get the point of this or any the rest of your homemades. I doubt the accuracy of this thing is all that great, the ranges suck, and it looks like shit. I can't see how this would be very useful in a war.

What a ridiculously unnecessary post. There is such a thing as constructive criticism, and then there is just being a giant douche. Seriously. Just because its not a UBER MEGA HAMP doesn't mean its useless.

Most guns can't fire nearly that fast. Its basically semi-auto since the priming and firing mechanisms are built into the same motion.

I'm sure the range could easily be improved simply by scaling up the strength/number of flexing arms.

Most of all, it looks reliable. A lot of breeches shave/jam darts, but this went 6 for 6 in the firing video. That alone makes it very appealing to me. I'd be drooling over a chance to use this
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#8 Ambience 327

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Posted 04 June 2010 - 07:59 AM

I don't get the point of this or any the rest of your homemades. I doubt the accuracy of this thing is all that great, the ranges suck, and it looks like shit. I can't see how this would be very useful in a war.



That is because you don't understand Kane's mentality. He isn't all about "my gun is the farthest-firing, most accurate, highest-ROF piece of equipment on the field". From what I've seen (both from his mods and by squaring off against him on the field of foamy battle), he's more about "hey, this looks neat, is great fun to play with, and/or was an interesting challenge to build." We would all probably have a lot more fun if more of us thought like that.

Kane - this thing is sweet. I'd love to see how ridiculous it would be with a full drum-mag. I hope to get a chance to face off against it some time soon. (Any chance of you making it down to my war on the 19th (hint hint, nudge nudge) :blush:

Edited by Ambience 327, 04 June 2010 - 08:02 AM.

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#9 taerKitty

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Posted 04 June 2010 - 11:12 AM

I don't get the point of this or any the rest of your homemades. I doubt the accuracy of this thing is all that great, the ranges suck, and it looks like shit. I can't see how this would be very useful in a war.


Different styles for different Nerfers. Having just gotten into homemades (WIPs only, so nothing for show-and-tell, sorry) I've learned to appreciate creativity, craftsmanship and the increasingly-rare 'hell, it's fun!' aspect of Nerfing in a whole new way.

In this case, props to Kane for using a mill + lathe for this. Yes, it puts it out of reach of most of the rest of us in the PVC gallery, but there's something to say for one-off pieces of finely machined works. It inspires the rest of us to improve our own craft, it elicits admiration, and, let's be practical here, it leaves at least in me the niggling idea of trying to replicate this with just ©PVC, brass, copper, et. al.

No, not duplicate, replicate. Multiple mods and homebrews out there have shown it possible to work a CS-6 clip into something other than factory CS-6 blasters. Kane's upped it one by making it feed reliably, not shred, etc. Already I'm thinking of some way, albeit ungainly, to do much the same with some copper (for rigidity) + brass (for tolerances) nested in a length of 3/4" PVC (for increased volume) to do something similar.

Will it be practical in a war? Maybe. Certainly not in an open-field scenario, where century blasters take command. However, in CQB situations such as indoor settings or perhaps denser foliage, it'd work just as well as any other mid-sized blaster. Also, can you imagine if "bow rounds" became a standard format as are "ballguns rounds" and "pistol rounds"?

Lastly, how cool would it be to get a kill with that? (Or, given my lack of Nerfmanship, it'd be cool to even be killed by it. :) )

Seriously, if you have nothing good to say about another person's work, then save the effort of posting and apply it to working on your own uber-efficient killing machine. A little respect helps the community; you know the 'C' in NIC?
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#10 Ryan201821

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Posted 04 June 2010 - 12:00 PM

LOLOMG IT DOESN'T SHOOT 100' IT SUCKS!


Seriously though, very cool. I've fired this myself, and it's the definition of fun. Great work.
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#11 KaneTheMediocre

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Posted 04 June 2010 - 05:52 PM

I don't get the point of this or any the rest of your homemades. I doubt the accuracy of this thing is all that great, the ranges suck, and it looks like shit. I can't see how this would be very useful in a war.

What a ridiculously unnecessary post. There is such a thing as constructive criticism, and then there is just being a giant douche. Seriously. Just because its not a UBER MEGA HAMP doesn't mean its useless.

Most guns can't fire nearly that fast. Its basically semi-auto since the priming and firing mechanisms are built into the same motion.

I'm sure the range could easily be improved simply by scaling up the strength/number of flexing arms.

Most of all, it looks reliable. A lot of breeches shave/jam darts, but this went 6 for 6 in the firing video. That alone makes it very appealing to me. I'd be drooling over a chance to use this


On reliability: It's pretty good, but not jam-proof. I'd say less than 1/20 will missfire or jam. Also, the vid was 5/5 darts in the clip, + 1 dry fire which makes a different sound. Since the clips are loaded with the breech closed, the clips don't work well with more than 5 darts.

On ranges: While pneumatic blasters (normal springers/airguns fall in this category), bigger or stronger components are all that's needed to increase range. However, with purely mechanical blasters like this, most of the energy is expended accelerating the bow, string, and plunger, which weigh MUCH more than the dart. Unlike a springer, there is no ratio of diameter between plunger and barrel, so however fast the plunger moves is how fast the dart flies. Nor can the blaster store energy during the firing action as springers do, by keeping the dart in tight barrels that prevent it from moving until the tube has built up pressure.

Most things that I could do to increase the tension of the bow will also add mass to it (ie using thicker bow material). However, I have lots of room to cut the bow shorter, which increases the amount of tension per draw, but reduces the total draw. Right now the bow could handle much more draw than the guide, so there's something to be gained there. Hopefully it's enough to get into the 40-50 zone, which is plenty for a novel blaster like this.


I don't get the point of this or any the rest of your homemades. I doubt the accuracy of this thing is all that great, the ranges suck, and it looks like shit. I can't see how this would be very useful in a war.



That is because you don't understand Kane's mentality. He isn't all about "my gun is the farthest-firing, most accurate, highest-ROF piece of equipment on the field". From what I've seen (both from his mods and by squaring off against him on the field of foamy battle), he's more about "hey, this looks neat, is great fun to play with, and/or was an interesting challenge to build." We would all probably have a lot more fun if more of us thought like that.

Kane - this thing is sweet. I'd love to see how ridiculous it would be with a full drum-mag. I hope to get a chance to face off against it some time soon. (Any chance of you making it down to my war on the 19th (hint hint, nudge nudge) :)


I've used it with a drum mag, but in a war it would probably fall off. As far as understanding my mentality, I DO like having the most effective piece of equipment on the field from time to time, but I already hoppered-HAMPs for when I want to dominate people. So I'm diversifying.

I don't get the point of this or any the rest of your homemades. I doubt the accuracy of this thing is all that great, the ranges suck, and it looks like shit. I can't see how this would be very useful in a war.


Different styles for different Nerfers. Having just gotten into homemades (WIPs only, so nothing for show-and-tell, sorry) I've learned to appreciate creativity, craftsmanship and the increasingly-rare 'hell, it's fun!' aspect of Nerfing in a whole new way.

In this case, props to Kane for using a mill + lathe for this. Yes, it puts it out of reach of most of the rest of us in the PVC gallery, but there's something to say for one-off pieces of finely machined works. It inspires the rest of us to improve our own craft, it elicits admiration, and, let's be practical here, it leaves at least in me the niggling idea of trying to replicate this with just PVC, brass, copper, et. al.

No, not duplicate, replicate. Multiple mods and homebrews out there have shown it possible to work a CS-6 clip into something other than factory CS-6 blasters. Kane's upped it one by making it feed reliably, not shred, etc. Already I'm thinking of some way, albeit ungainly, to do much the same with some copper (for rigidity) + brass (for tolerances) nested in a length of 3/4" PVC (for increased volume) to do something similar.

Will it be practical in a war? Maybe. Certainly not in an open-field scenario, where century blasters take command. However, in CQB situations such as indoor settings or perhaps denser foliage, it'd work just as well as any other mid-sized blaster. Also, can you imagine if "bow rounds" became a standard format as are "ballguns rounds" and "pistol rounds"?

Lastly, how cool would it be to get a kill with that? (Or, given my lack of Nerfmanship, it'd be cool to even be killed by it. B) )

Seriously, if you have nothing good to say about another person's work, then save the effort of posting and apply it to working on your own uber-efficient killing machine. A little respect helps the community; you know the 'C' in NIC?


On the mill+lathe: I think added an idea on how to build this without with nested tubes available at hardware stores + McMaster. Even still, most of the work is assembling, not machining, so I could probably sell and ship kits cheaply if there was interest.

I'll be bringing it to CHANO, and given the size of our mobstacles I'm confident that I can get kills with it. It's loads of fun to shoot, so I might end up using it for most of the war.

Edited by KaneTheMediocre, 04 June 2010 - 06:01 PM.

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#12 phillypretzel

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Posted 05 June 2010 - 11:20 AM

Great work (again): you are truly an original thinker in the world of nerf. I just completed my first HAMP, and I dig how your designs reduce the number of steps in firing a dart (priming and firing being done in the same motion). Thanks for the inspiration.

Edit: Just a thought- I fly r/c model airplanes, and we use lengths of surgical tubing to launch competition sailplanes: have you considered using surgical tubing, in place of the string? They sell it at my local Ace, and though it's kind of pricey (in the neighborhood of $4.00 a foot), it may pack significantly more energy per foot than the string- it could get you the 50+ foot ranges you're looking for. And if it doesn't work out, you can always make a slingshot with it :P

Edited by phillypretzel, 05 June 2010 - 11:46 AM.

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#13 KaneTheMediocre

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Posted 06 June 2010 - 02:42 PM

Great work (again): you are truly an original thinker in the world of nerf. I just completed my first HAMP, and I dig how your designs reduce the number of steps in firing a dart (priming and firing being done in the same motion). Thanks for the inspiration.

Edit: Just a thought- I fly r/c model airplanes, and we use lengths of surgical tubing to launch competition sailplanes: have you considered using surgical tubing, in place of the string? They sell it at my local Ace, and though it's kind of pricey (in the neighborhood of $4.00 a foot), it may pack significantly more energy per foot than the string- it could get you the 50+ foot ranges you're looking for. And if it doesn't work out, you can always make a slingshot with it :(


The tension is not provided by the string, which does not stretch significantly while firing. The tension comes from the CPVC bow, which flexes as the bow is drawn and fires. If I used an elastic string (such as surgical tubing) for the bowstring and kept the bow rigid, there would not be enough proportional difference in length for the elastic string to provide much tension, unless I made the bow so short that the whole assemblage looked like (and basically would be) a slingshot. Also, whatever the bowstring is made of needs to fit through a small tube that goes through the PEX perpendicularly, or otherwise goes through the hole in the PEX directly and survives rubbing against the guide.

So in short, surgical tubing WOULD make a great slingshot, but would not be helpful in the Autobow.
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#14 SerpentofSet

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Posted 06 June 2010 - 09:09 PM

I don't get the point of this or any the rest of your homemades. I doubt the accuracy of this thing is all that great, the ranges suck, and it looks like shit. I can't see how this would be very useful in a war.

I saw this post, and waited for a couple of days for the inevitable flames against it. I wasn't disappointed.

Could the range be increased by using a bungee cord instead of a string and non-flex CPVC?
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#15 taerKitty

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Posted 06 June 2010 - 09:54 PM

I think bungees and rubber tubing would elicit the same response and rationale.
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