Return and Grandma

Wow, that was certainly a long and busy hiatus! Two moves and two states later, I am finally back in a situation where I can continue this little project. To start off, here are some fun renders of a 3D cutaway model I made for an RPG campaign I am running. The game is set in the Warhammer: 40K universe by Games Workshop, and involves the crew of an Imperial tank trying to survive after the near annihilation of their operational maneuver group. Their vehicle is a Leman Russ Main Battle Tank; Conqueror variant. Being as obsessed as I am with realism (not to mention armored vehicle design and engineering), I couldn’t help but make changes. After all, I take it that since human beings are not 5 heads high it is reasonable to assume that the other miniatures are similarly exaggerated versions of what exists “in universe.” So, here is “Grandma” (I love my players).

Run for the hills!

Front view showing off the main gun and lascannon. Glass for driver’s vision blocks, along with much else, is a work in progress.

Armored vehicles are designed around their intended battlefield role. The M-1 Abrams was designed to skate (occasionally backwards) from one hull-down prepared defensive position to another while popping as many members of the oncoming horde of soviet armor as possible. It was assumed that it would generally be retreating back upon its own supply lines rather than advancing deep into enemy territory, so raw horsepower and torque were judged more important than range or fuel economy. Soviet tanks were designed with an almost precisely opposite set of requirements, so they are (relatively) small and light instead of big and heavy, long range instead of short, and generally designed for a more cavalry-like role than western tanks.

The fist step in determining how I would modify the official Leman Russ design was figuring out what the Imperials need from their tanks. I’ve done a bunch of work over the years in figuring out precisely how the Imperium works: administratively, logistically, militarily, and technologically. This meant that I had a ready supply of rough-order-of-magnitude quantitative data available to help me characterize their military requirements. The upshot was that generally, the Imperial Guard faces opponents that utilize infantry horde tactics (the Orks and Tyranids are practically archetypes of this). They are also called upon to fight in every extreme of climate and terrain. Additionally, the Imperium has at its disposal materials much stronger and lighter than we are currently capable of making. Since they need to produce  equipment on an almost unimaginable scale they favor fewer, modular designs rather than many specialized ones.

These pieces of information lead one to a design with a high profile (good line-of-sight), the option to mount a withering array of infantry-supressing weapons, and good cross-country mobility. Indeed, the Leman Russ profile is quite high, and the vehicle has both the option to mount automatic weapons or flamethrowers in side-sponsons and the internal volume to accommodate an additional crewmember or two to operate them.

The table-top model exaggerates these features by stretching the height out, shrinking the turret to a ridiculous degree, and increasing the size of the gun to comical proportions. Another primary feature of the Leman Russ as it appears in the official art is the wrap-around tracks. I preserved this feature in my design, as it increases obstacle-crossing ability, but replaced the model’s WWI-inspired lack of suspension (no, really) with a torsion bar system. On the whole, my design is about two feet taller than an M-60, while having a ground footprint somewhat wider and shorter than an M-1 Abrams (weight is about equal, increased width is for stability purposes). The tall, flat sides are not armored against main-gun hits; the primary armor is behind them and sloped inward around the box structures that would normally house the sponsons. These have their outer face armored over quite thickly.

Side view.

Front view, above. Note the commanders cupola vision blocks, TV sight, and main FLIR sight. Also bow-gunners TV sight.

“Grandma” is an anti-tank variant and so lacks side sponsons. Instead, she mounts a bow lascannon (high-energy pulse laser for anti-armor work). The lascannon is a semiconductor-stack infrared laser that fires 10 megajoule bursts in the form of a train of smaller pulses, with a full burst lasting about 1/10 of a second. It and its capacitor are a module that bolts to the outside of the vehicle so as to not compromise the glacis armor. By my calculations, the beam is self-focusing within a kilometer or so, but rapidly defocuses after that and becomes ineffective against armored vehicles beyond about 1200 m. At short range (within 750 m) it can burn through the frontal armor of any opposing MBT.

Good view of the Lascannon Module.

The Leman Russ is powered by a diesel-electric system, with an 1800 HP engine running a generator which charges batteries. The batteries feed electric motors which actuate the final drive for the forward drive sprockets. This variant uses the volume freed up by removing the sponson gunners to add another bank of batteries to keep the lascannon capacitor charged. The batteries are rechargeable low-temperature liquid salt batteries and can store enough energy to fully operate all vehicle functions (including locomotion) for 10 minutes without running the engine.

Rear view. Note the open engine louver.

Overall cutaway view. Blockheads inserted to indicate crew stations. No seats yet because CHAIRS ARE HARD.

Cutaway of engine. It’s an opposed cylinder design. In this and the previous render, you can see the round generator housing a bit forward of the engine. The big blocks to either side are the two main batteries. The fuel tank is beneath the engine deck and has a 600 gallon capacity.

One of the forward motors and drive sprocket (final drive is off with the other half of the hull).

Torsion Bar Suspension.

You may notice the odd lack of a turret basket. This is intentional. The commander and gunner sit in bucket-seats suspended from rails fastened (very securely) to the inside wall of the turret. The seat assemblies have a pair of stirrups for their feet. These both aid stability and to allow them to stand up through their hatches. They can drop down into the hull space  beneath the turret and lie down, have a meal, or take a nap (I’m sure they’d have a couple of bedrolls down there). A key point of my design is to enable the crew to spend long periods of time inside the vehicle without undue discomfort. Power is transmitted to the turret not via a traditional axial slip-ring but with a rolling-loop rim contact in the same housing as the turret drive gear.

Turret detail. Chain-drive cassette magazine holds 34 rounds of varied 120mm combustible case ammunition for swinging-arm autoloader. Gunner is in foreground with direct access to FLIR feed. Commander is on opposite side of autoloader arc with repeater monitor for both FLIR and external camera. Brass block is breech (30 cm recoil).

The turret is kept small in an attempt to limit profile, so there is no room for a human loader. I decided on a Meggitt-style autoloader (make sure to see the cool video) and cassette-type ammunition storage with overhead blowout panels. Grandma’s 120 mm high-velocity smoothbore gun has excellent accuracy at long range and is fully stabilized for on-the-move shooting.

The Bow Gunner (wears a second hat as the primary vehicle mechanic) operates his weapon via a simple joystick and monitor interface. He doesn’t have to worry about ballistics, after all.

Lascannon operator’s station.

That’s about what I have so far. I need to add the commander’s pintle-mounted weapon, the gunner’s hatch, the belly escape-hatch, and a score of other details before I’m happy with the model, but I think that it has definitely assisted my players in visualizing their surroundings.

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