Okay, a full day today, both historical and sci-fi gaming … so I’m just getting to watch this show and offer detailed comments now …

First up, @johnlyons – great prop weapon, it really looks like a post-apocalyptic piece of improvised (yet complete functional) gear.

Great info on the actual meaning of the “M4A3E8” – I always knew what an “E8” stood for, but I didn’t know about the engine, suspension, and gun specifications.

Justin, the American “military call sign alphabet” has changed over the years. During WW2 it was Able, Baker, Charlie, Dog, Easy, Fox, George, How, Ida, Jig, King, Love, etc . . . In modern times it’s been updated and standardized to the present model: Alpha, Bravo, Charlie, Delta, Echo, Foxtrot, Golf, Hotel, India, Juliet, Kilo, Lima, etc . . .

You’re right, E used to = “Easy,” not sure if that’s why they started calling it the “Easy Eight.”

THE (FIVE?) ELEMENTS OF TANK DESIGN:

The classic three elements are: firepower, survivability, mobility. But this has always been an over-simplification. This model only works if tanks are meeting in imaginary, one-on-one “jousting combat.” If course real warfare doesn’t work that way.

As John correctly points out, ease of manufacture can be a “fourth” element, because this is what’s going to determine how MANY of tanks you’re going to have. NUMBERS matter, and this explains the primary merit of models like the Sherman and the T-34. This also explains why “humbler” German designs like the PzKpfw IV and the StuG-III were far more important to the German war effort than the “big cat” Panthers and Tigers.

This can be further expanded into ease of operation / maintenance in the field. Tanks like the Panther and Tiger were 45- and 60-ton Swiss watches, they were prone to breakdown and once they did, required a mountain of work to repair because of terrible maintenance design and complex component systems. Infamously, many parts on the Panther engine had to be worked on upside down and blind, and don’t you dare drop your tools. Conversely, tanks like the T-34 and Sherman were easy to work on, with plenty of room to switch out components, and even if knocked out in combat, could usually be brought back into service with fairly straightforward first- or second-echelon repair work.

There’s actually a fifth aspect of tank effectiveness – kind of hard to define with a single phrase, maybe we can call it “crew ergonomics?” How many crewmen are there, how are they laid out, how are their responsibilities and “combat loads” balanced, and how well can they communicate?

This was the crucial edge that the German tanks had over British and French designs early in the war that were far superior to German machines if one only considers the “firepower / mobility / protection triangle.” German tanks all had radios. The crews all had throat mikes so they could communicate over the deafening noise inside the tank. Most German turrets had three men in them, a commander, loader, and gunner. Sounds basic now, but back then this was a novelty. The French Char-B and excellent S-35 tanks, for example, had only one man in the turret, the commander . . . who ALSO had to load the gun AND fire the gun. This meant no tactical flexibility, and a 1/3 rate of fire compared to a German tank. The Char B had its main gun in the hull, which meant reduced visibility and field of fire. The driver also had to “aim” the tank by pivoting the whole 60-ton vehicle. And fire the gun. Wait, wasn’t he the driver? And let’s not even get into how ammunition is laid out of stowed.

Even today this “crew ergonomics” debate rages. Note the modern Soviet / Russian line of tanks since the T-64, that choose an automatic loader rather than a human loader. Saves space and operating expense, sure . . . but it’s never as efficient or as fast. If you don’t think that has an impact on the tank’s ability, play T-72s in Team Yankee that get to fire once every turn . . . while the M1 gets to fire twice every turn. All this is down to this nebulous “Fifth Element” of tank effectiveness: Crew Ergonomics.

There may even be a sixth and seventh elements, being crew training (crews are always the most important element of any tank system) and combined arms / logistical support. In other words, how well does the tank, and all its merits and flows, fit into the larger operational doctrine and methodology of the army overall? But, admittedly, these aren’t really design features of the tank itself and so are probably out of scope of a conversation on the five elements of tank design. 😀

Don’t worry about it @warzan – the whole “calibers” thing can get a little confusing.

Basically, there are two definitions of the word. In small arms, “calibre” can be the hundredths of an inch the bullet is WIDE. Not the casing, not the shell, just the actual projectile. So a .30 caliber rifle bullet is .30 of an inch wide (7.62mm). This is the calibre of the bullet. A .22 pistol round is .22 inches wide, and a big round like the .50 cal is, well, half an inch across (12.7mm). 🙂

In bigger guns like cannons, “calibers” is usually an expression of the length of the barrel in relation to its bore. So a short, stubby howitzer-type shell like the early StuGs is usually listed as “7.5cm L/24.” The 7.5 cms is the width of the projectile. If you walk up to a StuG and stick your hand into the front of the gun, that hole is 7.5 cms (just short of 3 inches) wide. The “L/24” is the calibre. It basically says that the barrel is 24 times longer than it is wide. So the early-model StuG gun barrel was only about 71 inches long, or not quite six feet. A VERY short gun, meant for lobbing low-velocity HE shells at targets.

Later, the StuG would be upgraded to an L/48 gun for high-velocity work. Same size projectile (7.5cm), but the round leaves the muzzle much faster for increased range, accuracy, and kinetic hitting power.

A longer barrel (higher “L” calibre number) means more velocity. The bullet flies right at the target in a flat trajectory and blasts into the target with no explosive, just punching through the armor with sheer kinetic impact. Basically, Ek = 1/2 mass * velocity (squared). What matters is how fast the shell is travelling, so a high-velocity shell like a 17-pounder (77mm) hits armor harder than a low-velocity 105mm howitzer round

A shorter barrel (lower “L” calibre number) means lower velocity. Like a mortar or a howitzer, the gun “lobs” a big bomb at the enemy that contains explosive that detonates on impact. Usually better suited for soft targets, infantry, buildings, bunkers, etc.

Making a gun’s barrel longer is a little more complicated than simply “making the pipe longer on the end of the gun.” The reason longer barrels yield higher muzzle velocity is because the round is in the barrel longer, and the expansive gasses of the propellant charge are accelerating the round for a longer period of time (granted, this is probably two milliseconds rather than one millisecond, but it’s enough to make a huge difference on the speed of the round and it exits the muzzle).

The problem in Newton’s Third Law . . . every action has an equal and opposite reaction. Higher muzzle velocity means exponentially more chamber pressure, recoil, and a whole stack of other design features that basically means the back end of the gun has to be much bigger (chamber, breech block, recoil braces, gun mantlet, etc.). To the point where the 17-pounder is so big and bulky that it has to be installed in the Sherman turret sideways (as @johnlyons has often said) just to get it to fit.

This is the reason why many guns that DON’T need super-high velocities (i.e., not antitank guns) don’t often have long barrels or high “L” calibre numbers.