Saturday, September 04, 2010

This Week's Project : 1:6 Scale ТОЗ-34/TOZ-34 Hunting Shotgun

 This weekend's project comes from the pile of inactive projects I have lying around due to insufficient tech to advance. The list results from ambitious project ideas that have been stopped by one or two major problems that prevent finalization of construction. Oddly, the one stopping this week's project was something fairly simple: a hinge mechanism.

After moving off to other games, I ended up playing S.T.A.L.K.E.R. : Shadow of Chernobyl with the 2009 Complete mod. Bad idea. Mostly because it ended up crippling the AI and giving me the most lopsided and overpowered weapon in the game's programming: the Hunting Rifle, otherwise known as the ТОЗ-34 double barreled shotgun. So I had fond memories of using my Russian beatstick to take down mutant dogs, SPETZNAZ and other hostilities using a variety of buckshot, slugs and the occasional flechette. Thing is just absurd with slugs.

Anyways, to properly give tribute to my trusty pal that stood by my side for 90% of the game (the 2009 Complete mod gives you this shotgun fairly early in the starting zone), I had to recreate it in 1:6 scale. To understand what the gun is like, here's a Russian tech spec for the gun. The hinge mechanism is composed of a ring and guide rails, so there's no traditional hinge pin type joint. The issue is that the center of rotation isn't somewhere convenient, as it becomes located near the bottom surface of the barrel assembly, where there isn't enough material to support a pin. A fairly simple problem and one that prevented it from going anywhere for about 3 months. I decided to do an approximation that put the pivot somewhere close to the original but used a traditional pin to hold it together. I used some tricks to hide the hinge so you can't tell offhand how it's done.

First, the schematic! (A very poor one)

 This is all you're going to get. It's not a very complex model in theory, but I had some additional plans. For this model, in addition to the expected break action and lever lock mechanism, I wanted to go one step further and add a working shell extractor mechanism similar to the one on the actual shotgun. For that, I needed some extra shotgun shells, since the Force-a-Nature and Sledge's Shotgun are tying up the remaining shells I had. Hence, the endeavor to build my own shotgun shells last post.

The barrel is hollow, and to make one strong enough to withstand minor bending and light play, I chose to use one layer of Magic: the Gathering cards wrapped around a 2mm diameter compressed air straw, surrounded by printer paper for a final outer diameter of 4mm. Process is fairly simple, I'm sure you know how to roll a paper around a tube. I had to make two of these for the upper and lower barrels. I had to sand them down flat where they'd join for extra contact and to minimize the overall height of the assembly.

 The stock is the standard 4-card lamination combined to form 16 cards' thickness worth of material. Nothing exciting here. Had to remove a chunk off the template to account for the latch mechanism, but that's about it.

The latch mechanism is the same from the Force-a-Nature shotgun: Z shaped lever pivoting around a tube embedded into the stock, then sliding to engage a 1mm wide notch.

This is the hinge piece. The top notch is for the hidden hinge mechanism, which will be composed of a paper clip bent to a "U" shape with a inner width of 3mm. The bottom notch was something I didn't use in the final assembly. The middle piece shows the notch that will be used to engage the latch mechanism.

Here's the hinge mechanism. The "U" shaped paper clip glued to the stock will ride on top of the groove in the hinge piece, rotating around that point. The barrel will sit on top of that block, securing the pin in place. The structure is fairly narrow compared to the rest of the gun, so I can hide the hinge with the rest of the gun's structural components. This does make the hinge integral and irreparable if something goes wrong, but it's a low risk. So much for that holdup that I described. This next part should have been my excuse for the holdup, but I accomplished it in an hour or so.

The way the barrels are situated, there's a groove where they meet due to the curvatures. Normally, I'd fill in this material to get them flat, forming an oval shaped cross section. I decided to use a paper clip to fill in the gap, and use it to slide a small piece of material along the barrel axis to function as the shell ejector. The actual TOZ-34 has this mechanism, and uses these prongs to engage part of the main body to pull the ejector outwards. This piece was easy to replicate, due to how things were going.

I did have to cut away a piece of the barrel assembly after gluing them together, since the ejector was an afterthought that was born from convenience. Not hard since I was removing soft printer paper and not a durable Magic card. I had to replace the missing section with a similarly shaped piece of printer paper, with the same curvatures. Gluing the two paper clips to the sides was easy with the resultant grooves.

 Here's the mechanism in place. It consists of two paper clip guide rails using the barrel grooves as the guide. It slides in and out fairly well, with some fine tuning of the dimensions required to get a smooth consistent operation.

 The mechanism doesn't extend very far in the real shotgun, and doesn't need to go far for this gun. I won't be getting any fancy things going like having the shells fly out of the barrels when I break it open.

This is the engagement mechanism. It consists of another set of paper clips on the edge of the blue regions to engage the extractor tips on the sides of the barrel. Chose paper clips since it'll take longer to wear out, despite being much easier to shear off after repeated use. Nothing a lot of glue can't fix.

After adding the rest of the bodywork onto the gun, here's the near completed gun. 

 There's a few small details on the latch. Mostly a raised portion at the end for easier manipulation, and what I presume is the safety switch selector.

 Here's the gun with a coat of primer on it. These Obitsu stands are great for displaying new projects.

 With the right amount of friction, I can get the ejector to move and engage the rims of my poorly machined shells, and pull them out slightly. I'm happy with the end result.

This shows the level of movement the lever can be displaced. Unfortunately, there isn't a detent for the closed position to hold the lever in place. I think it should be fine. 

And that is the TOZ-34, a fine addition to my wall of increasing firearms. I'm thinking of not painting this model since everything I paint turns to crap. I'm best at building the prototype and getting it functional, but I'm absolute rubbish at painting. Rather than ruin a well executed model, I'll leave it in the prototype primer color for now until I get some motivation.

I've learned to appreciate the level of detail a toy manufacturer can get into a model after attempting to get the shell ejector mechanism working. This model would be costly and fragile if it weren't for the metal components, and even then, it has a lot of delicate features that aren't good for a frequently handled item. Best as a showpiece.

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