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Building the Fury Gun: How NOT to Build a Prop

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Picture of Building the Fury Gun: How NOT to Build a Prop
A complicated fantasy firearm, moving parts and lots of metal in a small apartment?  What could go wrong?
 
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Step 1: The Concept

Picture of The Concept
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As mentioned in my previous Instructable, this was a non-firing replica of a weapon that never was; the heroic and dangerous 45mm double-barreled break-open grenade launcher carried by 1930's pulp adventurer Mr. Fury.

The original concept was to make use of the growing technology of 3d printing; to model the complete weapon in 3d and print out the parts that linked several military surplus parts that looked cool for the project.

It ended up with me doing serious metal working in my apartment, with inadequate tools.  The biggest tool I had was a budget, bench top drill press from Harbor Freight.  Most of the serious cutting was done with a hacksaw!

I also made some serious errors, such as being misled by my experiences with welding steel to think I could braze multiple brass parts together in the same way.  In the end, the thing was as much epoxy and other glues as it was metal, and in hindsight we really could have printed more of it, done a lot less metal work, and saved ourselves much time and money.

Step 2: Importing the Parts

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The first step was to bring the existing parts in to the scale-accurate 3d model.  To avoid lens distortion I placed the pistol grip on top of my scanner and SCANNED it in.  Then I aligned and scaled it (as described in a previous Instructable).

The other parts were done by hand...calipers in hand, frequent measurements, lots of playing with scale tools and grid settings.  Early on I set the project in metric...and then it turned out almost all of the important parts lined up better in Imperial units.  Not only that, there is STILL a bug in Carrara Studio wherein if you set the workspace to metric it multiplies all numeric entry by 2.54 (the number of centimeters in an inch, natch).

Step 3: The First Attachment

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It would have been simpler to epoxy or weld.  It was just too tempting to make it possible to "field strip" the pistol grip.  Thus, the pistol grip is secured to the rest of the weapon by two pins.  And the pins of course had to be metal to be strong enough (I made an attempt to calculate sheer forces but my physics is rusty). 

You can 3d print in a bronze-infused Stainless Steel that is as strong as mild steel.  It also costs over ten dollars per cc of printed volume.  So the decision very early on was to print the smallest shape possible that would attach the pistol grip firmly, and attach everything else to it.

As the design concept evolved, it become clear the barrels would hang from a pivot point that rode a buffer rod through the centerline of the weapon and all the way back to a spring in the butt stock.  Since this was 90% of the serious loads on the weapon, the print was also designed to support this rod, thus becoming an integrated central skeleton of metal to support the weight and other forces involved.

Step 4: The First Fabrication

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We started with several pieces of 2" acrylic.  Unfortunately those couldn't even take the stresses of cutting.  So I placed an order with Online Metals dot com and ordered a chunk of brass tube.  At least the brass was a little easier to cut than steel would have been.  But, really, I wish I could have used PVC.

A problem that plagued the project was that tube is measured by OD (outside diameter) but pipe by ID (inside diameter).  It is easy to find "two inch" pipe in PVC, ABS, and other nice strong cheap plastics.  But it isn't 45mm inside dimension, and it isn't 2" outside dimension (as needed to fit into the surplus butt stock.)  So we had to purchase tube, which limited us to acrylic or metal as the ready choices.

The brass took a lot of sweat to work, and then I discovered the flaw in using a huge chunk of brass.  Brass is a conductor.  A great conductor.  To braze to it, I would have to bring the entire lump up to brazing temperature.  And my tiny portable oxy/butane kit wasn't going to do that.

Fortunately, JB Weld seems to be holding up.  The design of the thing meant I could slather on a good layer of epoxy putties to keep the pieces together.

Oh, and after all of my care there was an error in the dimensioning somewhere, and I had to grind and file at the printed part to make if fit.  Which meant going through several grinding and high-speed bits on my new Dremel, chewing my way into stainless steel!

Step 5: Extending


The next step was to build out towards the front of the weapon, putting down steel so the user could support the weight of the barrels on the wooden forend (a Winchester 93 wooden forend that we mail ordered).

The original concept was to braze a short pipe into the stainless steel print, then thread that into a necking adaptor down to 1" black pipe, which in turn slid inside the wooden shotgun forend with a little space to spare.  As the concept evolved, a second 3d print -- this time in plastic -- was incorporated to fill the difference between the diameter of the wood and metal parts, and to provide a protective flange for the user's hands as the barrels "recoiled during firing."

When the wooden forend arrived, it was obviously too thin to directly support the surplus swivel clip the sling would be attached to, so I extended the 1" black pipe, filed a flat spot, and drilled and tapped it to bolt the swivel clip to it.

Also, it turned out there was no such neck-down fitting available.  Not for those pipe sizes.  So I laboriously cut threads into one end of a 3/8" brass rod and inserted that into the print instead.  That went through a hole drilled in a brass pipe cap and a 3/8" coupler stood in for a large nut; because I filled the cap with JB Weld to keep the parts tight and aligned.

Step 6: The Buffer Assembly

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So there is a 5/16" stainless steel rod running the length of the weapon.  The barrels hang on one end, and the other goes into a spring.  This (in the imaginary world in which this thing could actually chamber live rounds), takes some of the recoil shock. 

I was looking at lots of enclosed spring and gas spring assemblies, and had built a closed spring assembly from 1" pipe, but when it finally came down to it I went simple; a couple of pieces of PVC glued together, filed down until it just fit inside the rear of the brass piece, and epoxied in place.  If it looked too fragile, I could always drill through the side and run in a steel pin.

The spring is simplicity itself; a 3/8" t-nut is epoxied on to one end, and a 5/16" collar is locked on to the buffer rod with a set screw.

Step 7: Joinery

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With the forend assemblies all epoxied into place, the time had come to smooth the join between the carved brass of the receiver and the printed plastic flanges that extended out along the forend.

Apoxie Sculpt, rough-carved with x-acto knife, then filed and sanded.  Then a second pass to build up and smooth the shapes more (Apoxie also bonds very well to itself).

Step 8: The Front Fork

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To hang the barrels I needed the part that connected the buffer rod to the barrels...or, technically, the trunnions (the pins in the barrels.)  The original drawing had the pivot on the bottom but this seemed simpler and more elegant.  In the final version a pair of holes was drilled and tapped and set screws inserted in them from the outside of the fork, and CA glued to keep them from backing out.

To take the weight it needed steel.  To stay on schedule and under budget I couldn't have it printed.  But I'd designed knowing that years back I had bent steel to make wrought-iron look scenery for the stage.

I cut a jig out of the only wood I had -- white pine -- and heated the 1/8" thick mild steel bar stock to red-hot.  The first bend was nearly perfect, but carbonized the jig (it also set fire to the jig, but I had been expecting that.)  Did I mention among my hardware store runs was a run to the welding supply store for gas goggles and new welding gloves?  Or the fire extinguisher?  Or that I did THIS part outdoors?

One jig and two more bends later, I took the two with the closest match and hammered and twisted at them until they looked like they matched.

Step 9: Welding

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I couldn't finish the fork without finally attaching the barrels together.

First I tried with my little Worthington welding kit.  No go.  The tiny tank of oxygen gave out before I could get started on a braze.

Then I tried to have it done.  Chased after a local welding company for days, getting a terrible run-around, before realizing I was better off dealing with it myself.  I knew how to weld.  Trouble is, I didn't have a shop any more.

At last I picked up the phone and called my brother.  Visited his wonderful shop for one short trip -- used his MIG kit to make the ugliest weld that would ever leave his shop.  Also used his cold saw to trim the barrels flush; I'd had them cut by the metal supplier but the tolerance was no more than 1/8" of an inch.

I knew not a lot of strength was needed on this weld, though.  And even better; it would never be seen.  Because the weld would be under a strip of aluminum bar stock.  And to add to the amusement, a sculpted set of fake weld beads done in Apoxie Sculpt adorned the edges of the bar stock.

Step 10: Detailing the Fork

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Such a pity...after all of this metal, right at the front of the prop where it was most likely to get dinged up I'd have fragile plastic and epoxy.

With the newly-bent fork pieces bolted to the buffer rod and anti-twist rod, they could be fleshed out to look properly beefy.  First was a simple washer, filled out with Apoxie. 

Next were strips of styrene half-round.  The styrene was heated with a hot air gun until it could be bent easily, then CA glued in place.  One trick I discovered is that the heat loosens the glue...I had to bend the whole thing then glue it all at once. 

A few bits of sheet styrene cut out and also CA glued on to the washers completed the look, and more Apoxie smoothed out the joints and filled the gaps.  I even put lumps of Apoxie over the exposed bolts -- they look sort of like rivets now.

Painted up, it looks pretty much like I wanted it to look; like a single rough metal casting.  So nice that for this prop, a lack of fifteen coats of primer and wet-sanding with 800 grit in between was actually an advantage.

Step 11: Surgery

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At this point I'd completed the interior mechanisms (see my other Instructable) and I could check latching and unlatching the barrels.

And failure.  The plastic printed part that was transferring the force from the wooden forend to the presser rod couldn't take the stress.  it was coming apart.

With the trusty razor saw I cut a slit in the smoothed, sanded, and painted receiver (sigh) and extracted the broken part.  Then got a sheet of steel from the hardware store and over a long day of cutting and filing created a replacement.

There were more adjustments to make, more errors...the brazed connection from the sliding brass guide to the rod that pressed against the breech assembly didn't hold.  And the rod was too small and was getting bent.  Still later in the process, the fake weld detail I'd added in a fit of foolishness to the bottom of the barrels got caught on the presser rod as well and had to be carved away. 

The basic concept of the mechanism worked, but it took a bit of adjustment!  I know it all seems the obvious way to build it now (actually, the obvious way is with pivots instead of sliding joints...!) but it took two weeks and several dozen sheets of sketches on paper to work it out.

Step 12: Final Details

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I did the last stages from final paint to the last little details in one great rush, not stopping to take pictures.

For a week I was moving half-painted parts back and forth.  Multiple coats of auto primer, sprayed thin, with sanding and patching with Tamiya White between coats as well.  Then several coats of a harder-wearing flat black epoxy.  Then staining and wash with acrylic paints.  A "chip and scratch" layer of silver paint dry-brush.  And, finally, a hand-rubbed graphite treatment to give it a metallic luster.

I drilled and tapped for the surplus "ladder" sight.  Created a front sight by chucking a piece of 1/8" brass rod in my drill press and holding a hand file against it.  Kids, don't try this at home!  The piece of stainless steel acting as a "dust cover" (mostly, hiding the springs and bolts and stuff) needed to be cut and drilled and that meant more ruining tools on hard steel. 

The German butt stock was thick paint over rust and I chose to partially strip it before re-painting.  I also stripped off some of the layers of grease from the furniture on the pistol grip, and painted it up with acrylics to match the nice new wood of the Winchester shotgun forend.  I carefully wiped down the stainless pieces, and even buffed the larger one with buffing compound and a Dremel buffing wheel.

There is one thing I have not done yet, however.

And that is to take the final model out into the woods, with of course the appropriate costuming, and take some decent pictures of the completed prop!

Step 13: Complete!

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Assembled, handed over to the client.  A couple weeks later, we took it out into the woods to take some pictures.
Anthonyp48 months ago

can you build a real wone

can this thingy use as a grnade luncher?
nomuse (author)  assassino desigen3 years ago
Well, yes but mostly no!

It was designed to be dimensional with certain real-world rounds -- because that gave us more options for associated props. And the original design did have functional trigger and hammer fall -- there is actually an open hammer (but no spring) on the breech face.

However! There isn't a pin, and the breech cover doesn't lock (and is plastic anyhow.) Nor is there any space or gripper to hold a round against the breech face.

We pretty much fudged the entire question of "how does it hold the round in?"
This is probably the most worked and planned out prop manufacture I've seen!
Though I must say it looks amazing.... (What got you into using really parts from other real firearms?)
The Rambler3 years ago
This is one of the most beautiful and realistic props I have seen. I wish I had the resources, the time, and the know-how to replicate what you've done here.
nomuse (author)  The Rambler3 years ago
Well, thank you for saying so. I like it okay myself..I think the treatments came out pretty realistic overall (thanks to the Replica Props Forum and several informative posts), and I think it has some of that gangly look of real between-the-wars firearms.

That said, the whole point of my Instructable was about making do with far too little. I admit freely I finally broke down and spent an hour at my brother's wonderful shop. Would that I could go there more often...in addition to 15" cold saw, MIG welder, and power bender, he owns his own 4' x 8' ShopBot!

But I could have done the welds elsewhere, or paid a local sheet metal company a few hundred bucks to do them. Everything else was marginal tools...mostly a single Dremel...and hand-sculpting with such wonder materials as Apoxie Sculpt and 3d-printed Alumide and Stainless Steel.

If I had to quantify the things that really made it possible, it would be patience, planning, long experience with hand tools, and my theater-trained sense of where and how to fake it (when you couldn't do it right).

It is really those new materials and new forms of access -- such as Tech Shop, the rental tool place -- that make it possible for us amateurs to make things we didn't think were possible. All I can say is start small, have a plan, and embrace failure -- it is from failure that one learns. If you are afraid of failure you will never start anything. But if you fail enough you learn how to turn it into just part of the creative process.

Hrm. I think I have another blog entry there. So...thank you again!
sergio004 years ago
:O
glitchus4 years ago
That 45 mm looks absolutely real. I certainly wouldn't want to be looking down the wrong end of that thing! You need (well, we all need) a serious machine shop rather than an apartment. You do know that there are 37 MM flares available (hint) for that added touch of realism, if you were to fabricate an all metal MK II, Just don't catch the woods on fire!
nomuse (author)  glitchus4 years ago
The flares are one of the things that got my friend into the original design spec. Actually, he also wants me to build or modify (the Japanese made one) a double-barrel flare launcher. Also non-firing, I presume.
glitchus nomuse4 years ago
if your interested in going to the 'next step' in realism, check out these guys for some ideas in munitions:

http://www.freewebs.com/grog/

'Grog', evidently has reloading data for 'home-brew' exotic munitions. I haven't ordered his 'disc' yet, but I've been thinking about it, as it would save a lot in 'trial and error'.
glitchus4 years ago
What the heck did that trigger group come out of? I initially thought it was from a WW II PPSh-41 Russian submachine gun but it's not. I'm curious, as an amateur antique gun collector.
nomuse (author)  glitchus4 years ago
Not too far off. It's a 1924/29 Chatellerault trigger/frame assembly.

http://www.longmountain.com/store/machine-gun-parts/Chatellerault-1924-29/
doomsdayltd4 years ago
wow just wow this prop is a beauty, you are a excellent craftsman making this top notch prop in just your apartment. This is hands down (other than movies) the best prop i have ever seen, the d@mn thing looks like it could fire and good work with the old gun parts added. I wish i could see this in person, keep up the good work, oh and last thing is this prop of your design or based upon something else other than the double barrel shotgun :D
nomuse (author)  doomsdayltd4 years ago
Thank you for the wonderful comment. My biggest disappointment is that the metal-to-metal braze I had planned for didn't work -- if it had, the final thing would have been as strong as a real weapon. As it is, I can brandish it one-handed, pick it up by the stock even, but if I drop it on a concrete floor...

We're hoping to take some proper pictures of the final thing this week.

You'd have to ask my client/friend, the gun nut, about where he came up with the basic design. It is extrapolation from period arms; there are 30mm flare guns in the period, including a Japanese over-and-under double barrel pistol. The 45mm shaped charge is similar to actual rifle grenade rounds. Where he thought of firing basically one out the other, I don't know! The rest of the design evolved from the premise, particularly, that it had to both break open to reload, and slide backwards against a strong spring to take up some of the recoil of pushing a 45mm shell down range.

Since I'm not a gun expert by any means, there were quite a few emails and luncheon sketch sessions where he'd say "Make up some part for here," I'd make up a part, and he'd say "No real gun ever did it THAT way. Here's a sketch of what those really look like." So it evolved cross-wise. I am happiest that we made very few compromises based on what we COULD build as opposed to what we WANTED it to look like. The trunnion leans furthest in that direction; the design of the trunnion is entirely based on the kinds of shapes I could achieve with materials at hand that could take the forces involved.

Still, I finished the project with a strong desire to make a laser pistol carved from a single block of wood, with NO moving parts, and no metal. (Unfortunately, what I've done since then is experiment with a mess of electronics I've now got to somehow fit INTO that proposed wooden shell!)
wow sucks if you drop the thing :( but um i think it will be a slightly big feat to carve a laser pistol from block of wood but i wish you good luck!
scoochmaroo4 years ago
Wow. Well, the finished product looks great!