In this episode you’ll learn
why the Germans made “square cut” tanks,
what technologies turned out to be the most effective
and what happens to a tank when a shell hits the target,
but doesn’t penetrate it.
Watch now!
The biggest and perhaps most important part of a tank is the hull.
It must provide space for the crew and protect them,
and hold all the armaments, mechanisms,
and other parts of the combat vehicle.
Up until the second half of the 20th century,
the material for hull manufacturing was armor steel.
Thanks to thermal processing or the addition of certain elements to the alloy,
it was much more durable than ordinary steel.
Armor steel was invented long before tanks,
in the middle of the 19th century, primarily for use in battleships.
The technology of assembling tank hulls was also borrowed from shipbuilding:
armor plates were mounted onto a frame with bolts and rivets.
joining with rivets had several disadvantages.
The frame that held the armor had to be made of high-quality steel and very durable,
which added an excessive amount of weight.
Moreover, the frame took up precious interior space.
The assembly of the hull was very time-consuming.
Also, rivets and bolts had a bad trait:
If the head was destroyed from the outside,
the body of the rivet or bolt could “shoot” into the tank, causing damage.
However, despite these problems,
rivet and bolt assembly was used up until the 1940s.
As technologies developed,
all countries that built tanks gave up on the frame assembly method
and replaced it with welding or casting, which created a much stronger hull.
These structures were much stiffer and more resilient;
they could withstand much stronger impact forces without deforming or shattering.
Hulls assembled from cast elements
as well as ones fully cast as a single element
were widely used between 1930 and 1960.
But, over time, cast armor lost out to welded armor.
In time, welding became the standard technique of hull-making.
Shape has a great influence on a tank’s survivability.
For example, vertically mounted armor plates have less shell resistance
than those mounted at an angle.
This became especially noticeable
when specialized anti-tank artillery became widespread.
The Germans built “square” tanks for most of World War II,
but not because they didn’t know about optimal armor angles.
This was an intentional tradeoff for the sake of easier manufacturing,
assembly, and maintenance.
The German late-War tanks,
the Panther and the King Tiger, were protected by angled armor.
Along with the ability to withstand enemy shells,
a tank needs to have enough durability
and structural strength to handle the stresses exerted on it by its own operation.
For example, the high-caliber cannons
used on tanks from the late 1930s onward produced a recoil so powerful
that it could distort the hull of the vehicle.
The same fate threatens a tank with a hull
that is not strong enough to survive numerous other battlefield effects:
landmine explosions, non-penetrating hits from anti-tank rounds,
and near misses by aerial bombs and artillery.
When designing a hull,
optimal placement of crew hatches
and mechanical access points in the armor is very important.
Any hole through the hull, even one covered with an armor plate,
weakens the integrity of the tank, so there shouldn’t be too many.
On the other hand, ease of access to the engine must be considered,
and the ability of the crew to bail out quickly from a burning tank is crucial.
The most famous Soviet World War II tank, the T-34,
had a large driver’s hatch in the front glacis plate.
It was one of the most vulnerable points of the early models of the “Thirty-four,”
up until the spring of 1943.
A shell hit to the front usually hammered the hatch into the interior of the tank,
where the driver was located.
It was not until the new T-44 medium tank came into mass production after the war
that this Achilles’ heel was eliminated.
Later Soviet tanks had the drivers’ hatches on the top of the hull
rather than in the glacis.
After the war,
advances in the technology of anti-tank weapons
gradually reduced the importance of hull shape for tank protection.
The new armor-piercing composite rigid or HEAT shells have such high penetration potential
that they pay little attention to the angling of armor plates.
Today, active, add-on,
and reactive armor have become crucially important for most tanks.
An incoming projectile has to pass through these three lines of defense
before it even reaches the main hull armor,
which is itself a cutting-edge product of metallurgy and materials engineering.
Reserve Time
Armor is the external shell of a combat vehicle;
its main goal is to stop or deflect enemy shells.
But the armor has a reverse side facing the crew.
In the comments to the last video you asked:
what happens inside the vehicle when a shell hits the armor
but doesn’t penetrate?
It’s time to discuss behind-armor effects!
Shells affect the armor differently.
Kinetic ammunition —
armor-piercing and APCR shells —
pierce it with the impact of their dense metal body.
HEAT shells do the same,
but with a directed stream of molten metal
under enormous pressure and temperature.
HE shells affect the target with an explosion.
In any case, whether the armor is pierced or not,
any shell can have behind-armor effects.
An impact or an explosion on the outside often leads to spalling —
pieces of metal shattering from the interior face of the armor.
The speed at which these fragments shatter can be enough to endanger crew
or damage interior components of the tank.
If the armor is penetrated, things get worse:
both the shell and armor shatter into numerous red-hot splinters
that can ricochet around the fighting compartment.
Along with impact damage, they can also start fires.
A HEAT stream piercing the armor isn’t a walk in the park either:
it punches through the armor
and penetrates the interior of the tank until it dissipates.
Its velocity is enormous and its temperature is enough to cause fires
and detonate ammunition.
Behind-armor effects are countered by different means.
First of all, the inner layer of the armor isn’t hardened,
because hardened metal spalls more.
Second,
various types of spall liners are widely used on the interior face
to prevent or reduce fragmentation.
Spall liners have been made from various materials
such as rubber and asbestos,
but nowadays are made from advanced polymers.
Still, even today,
behind-armor effects are extremely dangerous to a tank and its crew.