Wednesday, July 29, 2009

Developing and Constructing the Team Fortress 2 Force-a-Nature Shotgun

In developing the Force-a-Nature shotgun, I had to get some standardization in how I scale up my reference images to 1:6 scale. There isn't much sense of scale from an in game object, since we don't know what the exact size of the in-game surroundings and models are in Team Fortress 2. However, we do have one handy bit of insight on how big to make something: ergonomics and established design.

I have established a few set of rules based on observation of other model firearms in 1:6 scale. I've referenced a few model firearms, notably ones with fixed stocks. The sample pool included a SPAS-12 (folding and fixed stock, Dragon), an M-1 Garand (Soldiers of the World), AK-47 (ZACCA), and the De Lisle carbine (21st Century Toys). I've compiled my observations into the following standard I will now be using for all future endeavors: The G-43 standard.

Figure 1: The Gewehr 43

I chose the Gewehr 43 as the basis of the standard due to the initial similarities with the Force-a-Nature's construction, and that it was a handy representation of a wooden stocked firearm. First off, from Figure 1, I've taken note from the sample pool that the distance from the trigger to the rear of the stock was about 55mm, with a tolerance of around 1mm. This measurement is useful in approximating the size of weapons with fixed stock lengths.

The G-43 Standard encompasses the following principles:
  1. The distance from the trigger to the rear of the stock is 55+/- 1 mm.
  2. The trigger guard is around 10mm long from front to back.
  3. The handle thickness is a nominal 5mm wide.
  4. The grip thickness is around 7mm to be "wieldable" by a 1:6 scale figure. Larger sizes render the model un-wieldable, and smaller ones necessitate special features from the user's hand (spring loaded fingers) or extra tooling (rounding of the grip) of the handle.
I've previously used the last two pieces of information after purchasing my ZACCA AK-74 in making my StG-44 and M60 models. Those turned out ok, much to my surprise.

Figure 2: Rough Schematic for the Force-a-Nature Model

Armed with the knowledge of what makes a comfortable and usable stock-gripped firearm, I figured out the scale of the Force-a-Nature. The results of my measurements can be found in Figure 2 above. Units are in millimeters, because Imperial units are the fancy of a king's foot fetish.

The top part demonstrates ideas of building the hinge locking mechanism. The actual mechanism I copied can be found and better understood here. The sketch covers my implementation of the locking lever, but naturally, I tend to store 50% of the information on a sketch, 20% by the finished product, and 30% in my head. Not a good way to document things. The aforementioned link does a good job of explaining what the notches and recesses in my barrel are used for. The actual lever itself is a "Z" shaped paper clip section that rotates and obstructs the square cornered part of the hinge from swinging out.
Figure 3: The Blueprints for the Force-a-Nature

In my attempt to better clarify how it works, I drew up rough sketches of all the major components to the Force-a-Nature. The bottom right shows an idea of the rotating lever locking mechanism. Should have drawn that in isometric view. Oh well. I hope you have a good idea of mechanics and a good physics engine in your head. For those of you who can't mind-read, here's some photos of the mechanism.

Figure 4: The Barrel Notch

Figure 5: The Sliding Lever

The sliding lever is limited to an overall travel of 9 degrees. I originally chose for a larger range of 18 degrees, but centering the lever exactly to lock the barrels was a silly idea, unreliable and tedious. The lever end in Figure 5 is barely visible due to the nature of the size involved. There is a bit of play with the barrel assembly, even with the superglue trick to thicken the parts involved. However, post painting, I found a little bonus that corrected that problem.

By sheer luck, I designed the barrels to accept Dragon shotgun rounds. Placing these in the chamber filled up the gap causing the play, making the model a bit more solid to handle when locked.

Regarding the stock curvature and contours, I achieved this by laminating approximately 20 layers of Magic: the Gathering card together, then using a Dremel to shape the stock. Not also do you get a nice shape, but post painting, it looks like wood grain!

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