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1/2" Coupling Bow Conversion

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#1 Ice Nine

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Posted 07 September 2010 - 04:19 PM

HELPFUL TIP:

I apologize for the necro, but this adds significant content.
After building several of these bows for my friends, I found that they shattered easily at the point where the hole was drilled. There simply wasn't enough material to withstand the constant bending.
I have a solution. First, use a 1" x 1/2" tee. Then, bore out a 1/2" coupler, so PVC slides through it easily. Drill through this, and the bow arm. Slide this into the tee, and follow Ice Nine's instructions for the rest.

This seems far more durable than the original design, and I have put hundreds of shots through it with no sign of wear.



I want to make this clear: this is the first bow-powered +bow.

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This was an idea I had and discussed it with CaliforniaPants. Since I lacked a 5/8" spade (basically necessary) at the time he built the first prototype, and said it worked great. Supes props to him, and he deserves a lot of the credit as I probably would have sat on this for a while longer unless he hadn't tried it out first. I finally picked up the parts for this, including the bit (total cost: $12), so here's the write-up.

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This tee is 1/2" input with 3/4" sides. Pretty simple stuff, throw a bit of 1/2" in the input.

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Sand out two 3/4" to 1/2" so 1/2" PVC can slide through them without too much force.

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Slide four feet (or whatever) of 1/2" PVC through the bushings.

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Take your 5/8" spade bit through the input. I did it with a drill, not a drill press, and it was a bit tough but totes doable.

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Feed 1/2" CPVC through the whole setup. Cut it down at the end and put a stub of PVC on it for coupling purposes.

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Solvent weld the PVC over the CPVC so it doesn't leak and doesn't get pulled out.

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Then I pulled the spring out of my +bow.

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String 'em up. Variable tension is pretty nice and it's very easy to get the same amount of power out of this gun as with a K26.

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Throwing a hopper on it is the ideal.

Doing this to a +bow may seem odd to some people, since it's a lot more work and a decent amount of "larger gun" as compared to a K26 +bow. However, as people with bows and pump-action crossbows will tell you, bow arms are much much smoother to use as compared to the spring. While supplying the same energy, the bow arms are a lot easier to prime and a lot smoother too. I'm definitely a fan of the spring never rotating so as to grab on the catch notch. I would prefer to use a bow on this for the most part.

The best part of this is that the setup is entirely modular. It's very easy to untie the arms and take it off the gun, and as most +bow owners know it's simple to put a spring in the gun. You could then use the same arms on SNAPs, +bows, a whole host of guns, really anything that has an external priming arm (or even internal, if you were willing to cut the shell up).

Edited by Ice Nine, 29 May 2015 - 07:17 PM.

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#2 Zorns Lemma

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Posted 07 September 2010 - 04:21 PM

What is this, a nerf blaster!? You can't smoke this shit!
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#3 Talio

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Posted 07 September 2010 - 04:27 PM

What happens when you put the spring in and use this?
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#4 CaliforniaPants

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Posted 07 September 2010 - 04:31 PM

What happens when you put the spring in and use this?

Neither of us have tried it with a spring in yet, because we decided that it would probably break the side plates pretty quickly. Maybe a spring of the same length but lower strength would work, but the spring is definitely not needed to get normal +bow ranges.

Small edit: I'd recommend that you pad the plunger head with something fairly thick, because its likely to bash the bushing or whatever a lot harder than normal.

Edited by CaliforniaPants, 07 September 2010 - 04:37 PM.

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#5 Ice Nine

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Posted 07 September 2010 - 04:59 PM

What happens when you put the spring in and use this?


Gun explosion sounds pretty likely.

Another bonus to this design is that maximum draw is no longer determined by ultimate spring deflection. If I had a scrollsaw or bandsaw I could put a catch almost immediately behind the plunger head and this gun wouldn't have any problems with that.
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Unholy Three: DUPLUM SCRTA, DUPLUM PROBLEMA (2009)

But Zeke guns tend to be like proofs by contradiction

Theoretically solid but actually non-constructive

Rnbw Cln


#6 Ronster

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Posted 07 September 2010 - 05:41 PM

If you were to take a heat gun and give the bow part of the PVC a slight bend outwards--much like a recurve bow--would that increase the chance of the PVC breaking/snapping?
If not, then that could add possibly allow you to shorten the length, but have the same (if not greater) strength...
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#7 utahnerf

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Posted 07 September 2010 - 06:07 PM

Sweet gun/bow. I've gotta try this. I had one question though, does the string stay in place in the handle? I was wondering because there isn't anything holding it in place, only the tension of the string.

Edited by utahnerf, 07 September 2010 - 06:08 PM.

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#8 Gears

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Posted 07 September 2010 - 06:18 PM

Stay tuned for Ellen MK. XXX!
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#9 Daniel Beaver

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Posted 07 September 2010 - 06:45 PM

Nice and simple. Like you said, you could make the whole blaster about 6" shorter if you cut down the plunger tube, and re-notched the plunger rod. Of course, you would loose the easier conversion.

I did the opposite of this with Carbon's SNAP 7.5 Crossbow - I converted a bow-powered blaster to spring. But I have to agree that bows just feel nicer to use. I hope to see more of them on the field.
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#10 Carbon

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Posted 07 September 2010 - 08:53 PM

I like it. A lot. The whole idea of modular bow arms is great, rather than having to build it into the gun.

Questions:

Did you string it with clothesline?

Are you seeing any stress on the tee? Yours is far less "overbuilt" than most bows around the tee section...I'm interested to see how well it lasts.

Edited by Carbon, 07 September 2010 - 08:53 PM.

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#11 Ice Nine

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Posted 07 September 2010 - 09:01 PM

Did you string it with clothesline?

Are you seeing any stress on the tee? Yours is far less "overbuilt" than most bows around the tee section...I'm interested to see how well it lasts.


I used 1/4" nylon cord. It was rated to fifty pounds so I figured it work work well. On the supa' bow I made I used that braided steel cable but I was not a fan of working with it and worried about what would happen if something gave.

I've put a couple full hoppers of slugs through it, and the only thing so far seems to be one of the bushings working its way a little looser from the tee, but not enough to really cause any worry. At least, not yet. There's a war a week from Saturday so we'll see how well it holds up there. Worst case scenario, it breaks and I use a larger size tee and an x-to-1/2" reducer bushing to keep it useable in 1/2" couplers.
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Unholy Three: DUPLUM SCRTA, DUPLUM PROBLEMA (2009)

But Zeke guns tend to be like proofs by contradiction

Theoretically solid but actually non-constructive

Rnbw Cln


#12 Carbon

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Posted 07 September 2010 - 09:59 PM

Did you string it with clothesline?

Are you seeing any stress on the tee? Yours is far less "overbuilt" than most bows around the tee section...I'm interested to see how well it lasts.


I used 1/4" nylon cord. It was rated to fifty pounds so I figured it work work well. On the supa' bow I made I used that braided steel cable but I was not a fan of working with it and worried about what would happen if something gave.

Nice. The PVC would break before steel cable would (it's rated to 480 pounds), but it's definitely a PITA to work with. I'm not fond of how string feels at this kind of tension, though...I may give the rope a try next time I have to string up a bow.
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#13 Ice Nine

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Posted 08 September 2010 - 01:53 PM

Nice. The PVC would break before steel cable would (it's rated to 480 pounds), but it's definitely a PITA to work with. I'm not fond of how string feels at this kind of tension, though...I may give the rope a try next time I have to string up a bow.


It wasn't really the wire I was worried about, it was my lack of a tool to make sure the ferrule stayed on. I had to resort to a hammer which the packaging was very vehement about not using, so whoops!

The nylon stays right below the screw on the priming handle due to tension, and I doubt it would go anywhere.

A final bonus of using this nylon cord is that you can take a flame to the ends to seal it and stop it from fraying, which makes stringing it a bit easier, and it won't come unraveled with use.

If you were to take a heat gun and give the bow part of the PVC a slight bend outwards--much like a recurve bow--would that increase the chance of the PVC breaking/snapping?
If not, then that could add possibly allow you to shorten the length, but have the same (if not greater) strength...


I think heating the PVC to shape it would make it more fragile and prone to breakage, but that's just speculation on my part. One could shorten the arms anyway, these are pretty long and it's not that hard to get good power out of smaller arm lengths.

Edited by Ice Nine, 08 September 2010 - 02:29 PM.

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Unholy Three: DUPLUM SCRTA, DUPLUM PROBLEMA (2009)

But Zeke guns tend to be like proofs by contradiction

Theoretically solid but actually non-constructive

Rnbw Cln


#14 Ryan201821

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Posted 08 September 2010 - 04:22 PM

Very cool, of course. I like that you used adjustable tensioning so you can choose your level of diddle.

The .5" PVC seems like it should hold since you have one continuous bow arm, but we'll see if the Tee is going to hold up. Also the reason it's easier to draw is because you simply have less tension than a [k26]. Goes to show you how overkill the [k26] is.

Anyway, Super Effeminatesub-optimal.
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#15 TantumBull

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Posted 08 September 2010 - 07:15 PM

It wasn't really the wire I was worried about, it was my lack of a tool to make sure the ferrule stayed on. I had to resort to a hammer which the packaging was very vehement about not using, so whoops!

I solely use a hammer, and have never had any problems, but I'm sure its less than ideal. It's also probably more important that it doesn't fly off of a bow arm than just something like a plunger handle. Do you, or anyone else know what those actual "ferrule fastener tools" do differently?

And you're right about the PVC. Whenever you heat bend something rather than getting it into a liquid and casting it in a mold, the piece as a whole will be more fragile at a chemical level.

Also great job with this attachment. It's pretty darn neat that you can just attach something like that rather than tailor a whole blaster to it.
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#16 Carbon

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Posted 08 September 2010 - 08:37 PM

Also the reason it's easier to draw is because you simply have less tension than a [k26]. Goes to show you how overkill the [k26] is.

Less tension, but also reduced friction from not having a spring bunching and rubbing against the plunger rod.

And yeah, I crimp my ferrules with a hammer and a screwdriver. Sub-optimal, but probably OK for our purposes. Anyway, I think I'm going to be going with rope in the future....cheaper and easier all the way around.
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#17 Galaxy613

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Posted 08 September 2010 - 10:32 PM

I think I am going to try this to my 2-11 tomorrow. If not, I have a snap body that is dieing to be used.
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#18 Galaxy613

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Posted 09 September 2010 - 01:25 PM

The #NF Joint was not hard at all to make, just really messy with the PVC shaving and crap.

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So now I have a 2-11 XBow! I had to put some duct-tape behind the plunger head because of how CS designed the plunger head.

Tomorrow/later today I might increase the length of the main rods to get a longer draw.

I used 4ft of 1/2 PVC, at first I was skeptical of the length, it seemed like too much. But now it seems like just enough, but it doesn't make it any less smaller!

Currently, it's doing a little less as good as it did with the spring, but it's waaaAAAAAAAaay easier to prime than with the spring, and it's still doing 80-90something feet.

*Edit* I also had a hilarious thought, now that we are making other nerf blasters into crossbows... when will someone make an actual Nerf Crossbow, crossbow powered? :D

Edited by Galaxy613, 09 September 2010 - 01:26 PM.

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#19 Fome

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Posted 09 September 2010 - 01:32 PM

PVC bow arms are a cool fad and all but they do add an undeniable bulk to a gun. Why not do a slingshot instead? You'd still have an adjustable external power source and you could keep a much lower horizontal profile.

Just a thought, this is a neat project.

#20 Ice Nine

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Posted 09 September 2010 - 03:09 PM

Galaxy, that is a sweet gun. I am a fan.

PVC bow arms are a cool fad and all but they do add an undeniable bulk to a gun. Why not do a slingshot instead? You'd still have an adjustable external power source and you could keep a much lower horizontal profile.


You'd have an adjustable external power source with a much lower horizontal profile... That doesn't store energy nearly as easily as a bow would.

McMaster sells surgical tubing which I have used in the past (Uruk-Hai bows) and it's a fun material to work with, but it would need very high tensioning to be as useful as a K26 (or even K25) and at that point I doubt it would be any smoother or easier to prime. However you would get to keep the extra draw length capabilities which is something the springs don't have on it.

I'd be interested to see the results if someone tested it out but I'm not optimistic that it would be more effective or useful than a spring.

Edited by Ice Nine, 09 September 2010 - 03:11 PM.

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Unholy Three: DUPLUM SCRTA, DUPLUM PROBLEMA (2009)

But Zeke guns tend to be like proofs by contradiction

Theoretically solid but actually non-constructive

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#21 diamondbacknf1626

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Posted 09 September 2010 - 03:38 PM

*Edit* I also had a hilarious thought, now that we are making other nerf blasters into crossbows... when will someone make an actual Nerf Crossbow, crossbow powered? :D


I don't know when...but I smell a bow-powered Ellen on its way.

Also, great work as always, I may apply this to my pumpbow if I get the chance to go out this weekend and get the materials.
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#22 Zorns Lemma

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Posted 09 September 2010 - 05:16 PM

Something to note: one of the reasons why this is easier to draw but gives pretty similar results is that while your stiffness coefficient from the bending forces of your arms is much lower than that from the shear forces of a spring, you're basically starting at a rest force > 0. In blasters with poor design or poor fabrication, this doesn't bode well for your front bushing, plunger head, or side plates.

(To clarify, a [k26] goes from 0 lbs to ~34 lbs over the course of its draw. Bow arms would go from say, 10 lbs to 20 lbs over the course of the same draw. Energy is pretty comparable, but the forces are drastically different.)
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#23 Ice Nine

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Posted 09 September 2010 - 10:54 PM

Also, great work as always, I may apply this to my pumpbow if I get the chance to go out this weekend and get the materials.


One of my original goals for this project was to make an adaption system for my near-future pumpbow, so I wouldn't end up making two guns. Best of luck to you.

Right now I'm working on a prototype for a compound bow-esque design but it would probably be a much more difficult conversion, if not impossible. If it works (which I'm not entirely optimistic it will) it'll probably be more appropriate for purpose-built guns.
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Unholy Three: DUPLUM SCRTA, DUPLUM PROBLEMA (2009)

But Zeke guns tend to be like proofs by contradiction

Theoretically solid but actually non-constructive

Rnbw Cln


#24 TantumBull

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Posted 09 September 2010 - 11:08 PM

Right now I'm working on a prototype for a compound bow-esque design but it would probably be a much more difficult conversion, if not impossible. If it works (which I'm not entirely optimistic it will) it'll probably be more appropriate for purpose-built guns.

That's awesome! The other day I was just thinking about the possibility of something like that but I wouldn't know at all where to start. Best of luck to you, and I can't wait to see what you come up with! Do you think it would help much with a blaster with a catch, though, because I thought one of the main advantages of a compound bow was that it was easier to hold at full draw? Or would it also help with the actual priming?
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#25 NerfGeek416

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Posted 21 December 2010 - 05:38 PM

I apologize for the necro, but this adds significant content.
After building several of these bows for my friends, I found that they shattered easily at the point where the hole was drilled. There simply wasn't enough material to withstand the constant bending.
I have a solution. First, use a 1" x 1/2" tee. Then, bore out a 1/2" coupler, so PVC slides through it easily. Drill through this, and the bow arm. Slide this into the tee, and follow Ice Nine's instructions for the rest.

This seems far more durable than the original design, and I have put hundreds of shots through it with no sign of wear.
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