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Sledgehammer

Fun with solid CAD and plastic

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#1 CaptainSlug

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Posted 22 February 2006 - 11:26 PM

Interested purely in the mechanical challenges presented by such a project and as yet another excuse to have more fun machining plastic I've been working on designing what I would have envisioned in my younger years as the ULTIMATE Nerf gun. The Arrowstorm was my pride and joy until the spring snapped in half from one-too-many one-handed firings and then I moved onto the crossbow so both have nostalgia for me.

As boltsniper pointed out my earlier designs were a bit more complicated than they needed to be.
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So I started over trying to put myself in the mind-set of having to make a gun with limited tools and a limited budget. I ended up with a VERY simple (machining-wise anyways) design that I'm quite pleased with.
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$25 worth of polyester, a scrollsaw, power drill, some solvent, and a #6-32 tap wrench are all that would be needed to make this design which includes the following features.

- 14 inch barrel length
- Made completely out of PETG
- 5 inch travel spring-loaded plunger
- Removable/Stowable stock
- 8 round clip that feeds during each priming cycle
- Front reloading of the 5 lower chambers on the clip
- The ability to preload a second clip (or just a larger one) after two darts have been fired
- Ease of disassembly and replaceable barrel

What I would eventually like to do is do a complete instruction manual of how to make your own including power tool specific usage tips and general plastics machining advice. I've been primarily making computer cases out of plastic but this would be an interesting change from that. ^_^

I need to make an image outlining the priming and round advancing cycle...

Edited by CaptainSlug, 22 February 2006 - 11:29 PM.

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#2 CaptainSlug

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Posted 23 February 2006 - 09:24 AM

This should clarify the priming action a little bit.
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The tubing needs to be shorter than shown in the model.

Edited by CaptainSlug, 23 February 2006 - 12:02 PM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#3 ShadowSniper

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Posted 23 February 2006 - 09:51 AM

I'm liking the top one and the bottom one. Very original designs and they probably would work well. The top one reminds me of a grenade launcher and the bottom one looks very functional. Good job man.
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#4 WEASEL

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Posted 23 February 2006 - 03:29 PM

So your going to have the spring piston that supplies the air connected to the dart fireing thingey ma bob by using a hose? I have thought of using this idea many times to conserve space and make a more pistol like homemade, but never got around to it. I've always wondered if it would restrict air flow or have too much expansion area in the tube. I would love to see how these work if you ever give them a shot. Great work, and good job actually having a plan and not just some vauge waving hands in air description.
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#5 CaptainSlug

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Posted 04 March 2006 - 06:34 PM

I'm currently considering alternative designs. I don't have alot of time to machine this right now because I have other projects that are taking priority at the moment.
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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#6 CaMbLaM

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Posted 04 March 2006 - 07:48 PM

Slick man.
I look forward to the completed version
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#7 davidbowie

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Posted 04 March 2006 - 08:38 PM

One problem: the way you have it now, the pump handle goes completely into the grip when cocking. Given the way you normally pump a pump handle, this presents a problem. Where does your hand go?
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#8 ompa

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Posted 04 March 2006 - 08:47 PM

On top.

[Insert your mother joke here]

~ompa
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#9 LastManAlive

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Posted 04 March 2006 - 11:52 PM

I have a name for the snimated gun for you.

Big F*cking Gun.

It just looks so much like a huge ass gun to me. I love the simplicity to it, yet it holds its' semi-strength-esque form with the crude butt and exterior of the gun.

If (or when) you make this, don't paint it fancy. Make it battel scared and beaten-up some.
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#10 CaptainSlug

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Posted 06 March 2006 - 10:49 AM

It's nowhere near as large as some of the other homemades I've seen, but it does have an interesting weight balance.
I'm working on a design that if used with a shoulder strap can be primed and fired using only one hand. At present it's design is nowhere near as cleanly line as the previous design, but in terms of functionality it's much more interesting. I'll have some pictures this afternoon.

Edited by CaptainSlug, 06 March 2006 - 10:53 AM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#11 NerfLad78

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Posted 07 March 2006 - 08:29 PM

Um, these are Nerf Guns, right?

Now that that's clarified, I think that these guns look excellent, though they look like you would need a plastic mold to make them. How do the actions work on the other two? I would love to see these at a Nerf war, blowing the shit out of people.
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#12 euphemism

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Posted 07 March 2006 - 08:42 PM

I'm confused about one thing. What is the pump to shot ratio? It seems to be 1:1 and that doesn't seem like it would provide enough air for a decently powered gun.
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#13 CaptainSlug

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Posted 07 March 2006 - 08:45 PM

Um, these are Nerf Guns, right?

Yep, designed to shoot 1/2 Foam Backer Rod (presumably, but I'll have to test a variety of PETG tube sizes first).

Now that that's clarified, I think that these guns look excellent, though they look like you would need a plastic mold to make them.

No molding required. Thanks to large suppliers such as McMaster-Carr PETG (polytester) is easy to purchase as sheets and hollow round tubes. And that's what these are designed to be made out of with minimal machining work.

I'm confused about one thing. What is the pump to shot ratio? It seems to be 1:1 and that doesn't seem like it would provide enough air for a decently powered gun.

I should have said in the first post that these are spring-powered designs. I didn't bother to model the springs because they're such a pain to make, even in solid CAD.

Here's the new design: The One-Armed Bandit (OAB)
It's nowhere near as graceful but it should prove heavily functional. I need to do some very detailed tweaking on the model but here's basically how it works.
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It's designed to be easily disassembled with a screwdriver so that the pieces can be mirror left-to-right allowing one to be held in each hand. And the butt of the gun will have a thick padded shoulder rest with a shoulder strap so that each grip can be pushed forward with a single hand to prime the next round.

Edited by CaptainSlug, 07 March 2006 - 09:30 PM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#14 Meaker VI

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Posted 08 March 2006 - 01:22 AM

:ph34r:

Those designs are killer. Although I saw one problem with your first version of the one you plan on building, that the barrel looked like it would take alot of force from pumping. And, while somewhat confused by how the second version works (i think it's the handle being in both color and white, is there only one handle or 2?), it seems to have solved that problem.

Your very first one looks similar to the Pancor Jackhammer, the fully automatic 12 gauge shotgun I've mentioned before; and your second one (Designs, not versions of the third design) is probably my favorite. Looks easiest to build and like a enourmous pistol w/pump action.

I'll look forward to seeing what you do with all this...
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#15 CaptainSlug

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Posted 08 March 2006 - 02:05 AM

I won't bother explaining the very first design (the black one) because it's a bit more complicated that I would like to attempt right now.

The pistol also got too complicated but could be redesigned with the new tooth-advance systems to make it easier to machine. I'm also left wondering how much of an effect the tubing would have on performance. My gut tells me that it adds too much volume to the system and would prevent the plunger from building up an effective level of pressure.
Great, now you've given me another idea I could use. :ph34r:
You pump the grip back like a shotgun, but a cable and pulley pull the plunger forward into the primed position. This would also give the gun a weak recoil effect when fired while simplifying the internals a little.

Although I saw one problem with your first version of the one you plan on building, that the barrel looked like it would take alot of force from pumping.

The priming grip doesn't really touch the barrel, it slides along the plunger tube. And the plunger tube acts as a frame support for the barrel. It it does turn out to be an issue I could get a tube with thicker walls for the barrel.

And, while somewhat confused by how the second version works (i think it's the handle being in both color and white, is there only one handle or 2?), it seems to have solved that problem.

The latest design only has one handle/grip. The white in the animated images is just a background. Another benefit of the design is that since the plunger/tube, and grip parts are on the side the grip can be rotated around 180-degrees if for some reason you want it on the side, or you want the clip to advance downward instead of upward.

Your very first one looks similar to the Pancor Jackhammer, the fully automatic 12 gauge shotgun I've mentioned before

Actually I was drawing inspiration from the AA-12 for most of the design.

Edited by CaptainSlug, 08 March 2006 - 02:25 AM.

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#16 Meaker VI

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Posted 08 March 2006 - 07:50 PM

Well, I'm very impressed with your designs at any rate. I'll be even more impressed when I see the finished product; you may have introduced a new aspect to building nerf guns with that website. Most people don't use flat/square surfaces in thier guns, you've found a site that provides them in abundance and cheap.

So I'll be looking forward to actual plans and things, since right now I am busy architecture-ing and trying to build a chair out of cardboard (If you're wondering what that has to do with architecture, we are in the design portion of the degree right now, not the architecture part).
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#17 Agent X10

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Posted 09 March 2006 - 12:31 PM

Gah! Why must you all conspire against me to make me want to finish making my spring homemade rifle when I should be making darts?!

Anyway, looks like someone has been having way too much fun with CAD. I have wondered whether a barrel mag like in your first design would work, but it'd be hard to make it do so, as far as I can see. Anyway, nice designs and stuff. I'm looking forward to seeing it made, possibly.
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#18 CaptainSlug

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Posted 09 March 2006 - 02:44 PM

Yes, a drum magazine is definitely not the easiest thing in the world to make.
It would involve cutting uniform lengths of PETG tubing, drilling the pattern in a disc or two, then using IPS Weld-on solvent to adhere all the peices together. All of which I can do with the tools I have.

I'm considering making a new design similar to the arrowstorm, but I'll have to figure out an easier way to make the advancing mechanism for the drum.

Edited by CaptainSlug, 09 March 2006 - 02:46 PM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#19 CaptainSlug

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Posted 11 March 2006 - 08:17 PM

Alrighty. I wanted to approach the drum magazine differently with everything I've learned so far with each successive design. This has become the most adaptable design yet.
The Nerf Monsoon.
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+ Can use stock darts (loaded in the end of the barrel) and stefans (loaded from the rear of the drum)
+By swapping out some plates on the outside of the gun the control of the priming/advancing cycle can be changed from the grip to a secondary handle.
+The stock can be folded to fit flat over the top of the gun.
+The clip ejector is the hoop on the top of the gun and once depressed the drum can be removed.
+The plunger is attached to 1/16th-inch steel cable on a pulley so that the priming action is reverse of the plunger travel.

The only thing I'm stuck on is what compression load I want to have on the spring. It's currently designed around a 16lb spring, but with only minor adaptation I could use an 11lb spring instead.
Is it better to have more spring load or more spring travel? I'm kind of stuck between choosing a 4"/16lb spring or a 10"/2lb one.

Edited by CaptainSlug, 11 March 2006 - 08:31 PM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#20 m15399

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Posted 11 March 2006 - 08:27 PM

How does the drum rotate? I can't quite see the top part clearly. I see a triangle, though.
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#21 CaptainSlug

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Posted 11 March 2006 - 08:41 PM

How does the drum rotate? I can't quite see the top part clearly. I see a triangle, though.

Yeah sorry about that. It's really hard to get a good image to explain it.
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1. The triangle on the top of the gun advances the drum. As it moves forward it rotates the drum by forcing the outside tooth on the clip to move counter clockwise.
2. The drum is advanced to the point that the locking tooth (which is tensioned to move upward thanks to two rubber-bands) on the inside of the drum has engaged the notch.
3. As the triangle on the top retracts the locking tooth finishes the advancing cycle and centers the next barrel.

The yellow circles in the image are free-spinning aluminum spacers with slightly larger washers on the end that act as a clamp that holds the drum in place. The rolling spacers on the inside of the drum can be disengaged by pressing down on the clip eject loop on the top of the gun.

Edited by CaptainSlug, 11 March 2006 - 08:46 PM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#22 CaptainSlug

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Posted 12 March 2006 - 12:15 AM

Had to modify the body of the gun to accomodate a change in the main spring.
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Many thanks to boltsniper for the measurements I needed. Industrial supply doesn't have the right kind of springs so I'll just have to go with what is known to.
Ironically the measurement changes also made the folding stock fit perfectly onto the top of the weapon when folded.

Edited by CaptainSlug, 12 March 2006 - 12:26 AM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#23 ristrictor-distructor

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Posted 15 March 2006 - 10:33 PM

Those drawings are sweet
i learning to use AutoCAD in school now but those look like invertor, or your really good. what ever your still really good but the true challenge will be building those guns your last post i think is the most realist building wise and also the best looking

Edited by ristrictor-distructor, 15 March 2006 - 10:35 PM.


#24 CaptainSlug

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Posted 16 March 2006 - 12:09 AM

I have ample experience machining plastic, I just need to find time away from machining computer-related parts to make this happen. It may be a few weeks before I can start work on a design because I have a case I need to finish.
I'm using Alibre Xpress for these designs, which functions similarly to inventor. I have several years of experience with low-poly 3D modelling but only a few months of practice in solid CAD.

Edited by CaptainSlug, 16 March 2006 - 12:22 AM.

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The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?

#25 CheeseNerfer

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Posted 16 March 2006 - 10:19 AM

Awesome designs, my only concern is that, that design looks extremely front heavy making it rather hard to aim well, run with, etc. (kind of like a minigun?). Anyway I'll enjoy seeing the finished product.

Just out of curiosity, how long does it take you to draw up those desings? I'm an a engineering acadamy at my highschool using inventor and if I was to make those it would take days but you seem to push em' out almost immidietly!
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