In this episode you’ll learn how tanks first got turrets,
why the French Renault FT-17 became an icon
for military engineers of the early 20th century,
and how the concept of the multi-turreted tank rose and fell.
The Nuts and Bolts of Tanks — Turrets
It’s hard to imagine a tank without a turret.
But the first tanks didn’t have them.
The weapons on the first tanks were mounted in the hull, in forecastles,
or in sponsons—special bulges on the sides.
The layout was modeled directly on battleships.
These types of mounts afforded each weapon a limited firing angle.
Several cannons and machineguns had to be mounted
so that the tank could fire in any direction without turning the hull.
The French, who had introduced two early tanks that were pretty disappointing,
even by the measures of that time,
suddenly hit the bull’s-eye near the end of World War I.
They built a conceptually new tank
that became the model for armored vehicle design
for decades to come: the Renault FT-17.
One of the revolutionary features of this light tank was the turret.
It had full 360-degree rotation:
the cannon and machine gun could fire in any direction.
Renault wasn’t the first to place a turret on an armored vehicle:
rotating turrets with machine guns, cannons,
and combinations of weapons were widely used on armored cars.
The British had tried to mount a turret on their tank prototype in 1915.
But Renault was the first to create a mass-produced,
working tank with a rotating turret.
Such a system had great advantages over the sponson mounts.
Starting from 1918 up until today,
virtually all tanks have a rotating turret.
Actually the idea to mount turrets on tanks was also borrowed from warship design.
The location where the turret is mounted,
usually on top of the upper glacis plate,
is called the turret platform.
It’s basically a big bearing,
consisting of a static ring on the hull
and a moving ring on the bottom of the turret.
Balls or rollers are placed between the two rings
and the turret rolls on them as it turns.
The turret platform has to be strong enough to support the turret
and hold it in place despite the forces of gun recoil,
impacts with obstacles, tank tilting, and so on.
The means of turret rotation evolved over time.
In the first tanks, the driving force was crew muscle, typically with hand cranks.
Later, electrical and hydraulic motors came into use.
These could turn the turret much faster and fire control improved.
Nevertheless, the manual drive mechanism didn’t go away:
even in a modern tank the crew can turn the turret manually
if the turning mechanism is damaged.
In most tanks, the turret houses at least half of the crew.
The tank commander, gunner, and loader are located here.
The main armament is also here along with the crew who serve it.
Part of the ammunition load is stored in the turret, within easy reach of the loader.
Shortly after World War II
the French came up with another revolutionary design concept: the oscillating turret.
It consists of two parts, each of them moving in a single plane.
The lower turret section turns to provide horizontal aim.
The top section, mounted on a trunnion,
can only move up and down—oscillate—
providing the elevation and depression to aim the gun vertically.
The oscillating-turret tanks were usually equipped with an autoloader,
omitting the need for the human loader.
Although several tanks incorporated the oscillating turret,
the concept proved to be a dead end.
Performance was disappointing
and the system was eventually abandoned in favor of conventional turret designs.
The idea to make the turret fully unmanned appeared in the 1960s
and it is still in active development today.
This kind of layout would allow for improvement of the turret’s armor
and would isolate the crew from the ammunition.
The concept looks promising, but time will tell if it will ever come into wide use.
Turret shape is as important for the tank’s survival as hull shape.
Vertical armor plates are usually less resistant to penetration than angled ones.
That is why, even in the era when turrets, like hulls,
were based on an internal frame,
some variations with rationally angled plates appeared.
Turrets made by welding can roughly be divided into a few types.
Cylindrical turrets resemble a cylinder
without angled sides—something like a barrel.
Angling the turret sides improves shell resistance,
leading to the conical turret type.
Both types were installed on the Soviet T-28.
A half-cylinder, or the so called U-shaped turret, was installed on the Tiger.
The back and sides of the turret were a single curved plate,
with a straight plate comprising the turret front.
A big step forward came with advances in casting technology.
Casting allowed different elements of turrets to have varying thickness
and complex shapes— ovals, conical shapes, bowls, and so on,
improving shell resistance.
The post-war Soviet tanks took advantage of these advances.
The first composite armor appeared in the 1960s.
Tank turrets started to be made by welding together plates of multi-layered armor.
Currently this is the main technology.
Regarding turret shape, as with hulls, shape is generally considered secondary,
while quality of composite armor, reactive armor,
and active protection systems have become dominant.
Extra time
The first tanks had no turrets at all.
Then tanks appeared with the now-familiar single turret.
However, from the 1920s through the early 1940s
many countries fielded multi-turreted vehicles.
You asked us to describe them in detail.
The multi-turret concept was born at the end of World War I.
Its appearance was not a surprise,
since most of the tanks of that time were armed with several cannons
or machineguns mounted in sponsons on different sides.
The turret’s advantage over the sponson was obvious.
Multi-turret tanks were designed to break through enemy defense lines.
With their large number of guns,
it was imagined that they could deliver maximum firepower not just in front,
but also to the enemy trenches on the sides.
The term “trench cleaner” was coined,
and multi-turret tanks were considered the best for this role.
The idea was enticing
and almost all leading tank countries in the world fielded such vehicles.
A whole range of problems with these vehicles was discovered later on.
First, because of weight, a multi-turret tank could not be protected
with thick armor without impairing mobility.
The Soviet T-35, the king of military parades of the late 1930s and early 1940s,
had only 30 millimeters of armor in front and even less on the sides.
As anti-tank guns were coming into wide use,
by the mid-1930s such a thin-skinned giant was mostly useless.
Second, the commander of a multi-turret tank
had to coordinate fire of all weapon positions.
In a real battle this was a nightmare for the commander:
it was very hard to spot targets quickly
and pass their coordinates to the gunners in their different turrets.
As a result, these tanks’ combat effectiveness was low.
Third, the design complexity of multi-turret tanks
inevitably led to problems of mechanical reliability.
The abovementioned T-35s ran well only on parade.
They broke down often during field tests, not to mention real combat.
The multi-turret “brothers” of other nations had the same problems.
Although they looked impressive,
tanks with numerous turrets on all sides turned out to be too expensive,
too heavy, and too complex.
This design pattern lost out to the single-turret design,
which easily proved its supremacy in World War II.