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At the outbreak of the Second World War, the US was lagging behind many of the other nations
in the industry of tank development and manufacture, and their British Allies were not much better
equipped in the field of armoured warfare. Following the speedy fall of France in 1940
at the hands of the aggressive German advance. They knew that they needed to upgrade and
develop their weapons and armoured vehicles. Making a new tank model to compete with the
very capable German tanks would require it to be agile, well armoured, with rock-solid
reliability, have a powerful gun that could take out enemies from all angles, and perhaps
most importantly of all be quick and cheap to manufacture.
However, combining all these traits into one tank is no easy task and in July of 1940,
a new Medium Tank model, the M3, was proposed. Intended to be a stop gap solution [1], the
War Department confirmed and authorized its development quickly, and just a year later
the first models were rolling off the production line and shipped to the front line.
The US wanted a 75mm gun in a turret, however their engineering capabilities were nowhere
near advanced enough to realize this goal in such a short turn over time.
Fitting a large gun like this presents numerous design challenges, chief among these was building
a hull capable of supporting it. At this stage the US did not have the equipment needed to
build a large turret ring, and the technology needed to cast a hull strong enough to bear
a large turret. And thus the M3 Lee was produced as an interim
model, while the design of a larger fully traversable turret fitted with a 75 mm gun
was figured out, and the moulds for a cast hull were developed. The M3 only ever managed
to bear a sponson-mounted 75mm gun and the turret was instead fitted with a weaker 37mm
gun with a hull consisting of simple flat panels riveted together. This gave the 75
mm gun the space it needed inside the hull, which was not available in the small turret.
These design trade-offs disadvantaged the M3 greatly.
If the crew wanted to fire the main gun over a sand or earth bank, they would be forced
to fully expose the hull of the tank. While the entire tank would have to turn to aim
the main gun. Making the main gun clumsy and slow to control.
The Americans were well aware of these design issues, and were busy designing the M3s replacement
even before the M3 entered production [2]. This replacement would eventually become known
as the M4 Sherman. The most produced Allied tank of World War 2, and the workhorse of
the front line.
While the M3 was never intended to be a long term solution, it did influence many of the
design decisions for the M4 Sherman.
The M4 and M3 shared the same Vertical Volute Suspension system [3], which used coiled sheet
spring steel. This structure allows the coils to slide past each other, opposed to typical
helical springs which hit a limit in compression when the coils contact each other.
Allowing this sheet metal spring to tolerate heavier loads in a more compact space, while
being easy to maintain and replace. [3] The lessons learnt from the past year of the war
taught the Ordnance Department that the new tank would have to be both fast and easy to
produce. Taking lessons from the American automotive mass manufacturing industry, Chrysler,
Ford and General Motors all contributed to its manufacture.[4]The engineers of the Sherman
wanted all parts to be standardized so that each unit could be simply and hastily assembled.
These parts would also need to be simple to remove, so that the M4 could be repaired in
a combat situation with minimal delays.
The bogies, which were sets of rubber road wheels that transfer the weight of the tank
to the track, were bolted to the hull, so that they could be removed with ease for repair.
[5]
The M4 finally fulfilled the American’s desire for a 360-degree fully traversable
75mm gun. The turret itself was made from a single cast part, rounded to deflect income
rounds, and bolted to the turret ring. They fitted the turret with a single-axis gyro
to stabilize the gun allowing it to fire with greater accuracy while in motion.But, with
the relatively low muzzle velocity of 610 metres per second [6], it diminished the effectiveness
of the turret and would be the basis of most problems the M4 faced in the latter years
of the war.
The main weapon was however complimented by a 50 calibre machine gun mounted on top of
the turret with a coaxial 30 calibre machine gun and another 30 calibre gun operated by
the bow gunner. Making it a formidable infantry support tank.
Production was simple and in full-swing by 1942. At the height of production one M4 Sherman
rolled off the assembly line every 30 minutes. [7] Just as American revolutionised mass manufacturing
with the Ford Model T, which I have covered in more detail in the past, America was now
revolutionising the production of armoured vehicles. And thanks to the Lend Lease Agreement,
signed in early 1941, America was allowed to export thousands of tanks to Britain and
the Soviet Union.
Most estimates of wartime production reach over fifty thousand units [8], but the Sherman
wasn’t produced in just one model. Each new variant built upon those before it. Mostly
focusing on improving the engine and the method of construction for the hull. For example,
Early hull M4 designs, like the M4A1, were constructed from a cast hull. Where the entire
hull was cast in a single block. This was a difficult process and required a lot of
specialised workers and equipment, and was difficult to repair in the field. It was soon
dropped in favour of a simpler welded design where the hull was constructed from multiple
flat and casted parts welded together. These welds were a weak point in the hull, and these
too were gradually minimized with additional armour plating, and superior construction
to reduce the number of welds needed.
One of the largest problems that resulted in a major redesign was the floatation problem.
Where the weight of the tank was not being spread over a wide enough area. This increases
the pressure the tank will exert on the ground, and thus make it sink further into the ground.
Increasing both the power needed to move and slowing it down, or worse still getting stuck
completely. [10] To deal with this problem some Shermans were fitted with track end connectors
called grousers to increase the track width and thus decrease the ground pressure. A more
significant design changed was brought in 1944, with the introduction of a horizontal
volute spring suspension.
This, as the name suggests, moved the springs from a vertical to horizontal position, which
reduced their height and allowed for the addition of a hydraulic shock absorber to smoothing
the ride and reduce the stress on the springs, which had a notoriously short life. The road
wheels were now placed in parallel pairs, which allowed the track to increase in width
to 0.58 of a metre. A massive increase in track width that drastically decreased the
tanks ground pressure, and thus increased it’s mobility
Other changes were made to improve the survivability of the M4, as a result of horrific lessons
learned on the battlefield.
The Sherman initially had 57 degree frontal armour, forcing the designers to implement
tiny driver and bow gunner hatches. These hatches were far too small and made evacuation
procedures difficult. Made even worse by the fact a large amount of ammunition was stored
in the vulnerable turret, which often cooked off when the tank was hit resulting in horrific
fires. In late 1943 changes were made to improve the crews chances of surviving after a critical
hit. The armour angle was reduced 47 degrees, providing
more space to incorporate larger hatches. The majority of ammunition was also moved
to the floor of the tank, where it was better armoured and less likely to catch fire.
They also implemented wet storage [12], where each shell was separated by canisters filled
with a gel like substance made of water, anti-freeze and a rust inhibitor. If the ammo rack hit
these containers would be pierced releasing the gel, which would cool and quench the rounds.
At this stage the Sherman was a formidable foe for any Panzer tank. However, as the war
progressed newer and stronger German Panther and Tiger tanks entered the fray.
To increase the M4s chances against these advanced German tanks a final major redesign
was introduced with the inclusion of a more powerful 76 mm gun. Bringing us to perhaps
the best M4 variant that fought in world war 2. The M4A3E8, or the Easy 8, which incorporated
every improvement I have mentioned in this video. Making it a formidable opponent for
ANY german tank.
This was just one of many Sherman variants that entered the fray with specialised weapons.
Some were fitted with rocket tubes which rotated with the turret and fired in a barrage at
soft targets, others were fitted with flamethrowers.
While some took on roles as frontline work horses, being fitted with bulldozer blades
and hedgerow clearing tools to clear a path for other vehicles and infantry.
Others were modified with flails to clear mine-fields, designated as the Sherman Crab.
This was a tremendous sight during D-Day operations with the chains swinging wildly around striking
the ground with a sickening sound for any onlookers. Occasionally the chains would break
off after successfully detonating a mine, forcing any nearby infantry to duck for cover.
[7] [3]
290 Shermans were modified for the amphibious assault of Normany, called the DD Sherman.
These Sherman’s were fitted with rear-mounted propellers, which diverted power from the
tracks using a bevel gear. Which was the origin of the DD suffix, standing for Duplex Drive.
They were also fitted with a folding canvas screen to increase the buoyancy of the tank
and allow it to wade into shore.
Despite showing itself to be an incredibly capable machine, the Sherman has a bad reputation
in some circles. The old myth that it took 5 Shermans to defeat one tiger, as perpetuated
by the movie Fury. It shouldn’t be a surprise that a medium tank like a Sherman would be
at a disadvantage to a defending heavy tank, but this statistic is simply untrue. The Allies
were also at a huge disadvantage with getting larger and heavier tanks into mainland Europe,
where Germany could easily transport these vehicles overland straight out of the factory.
These World War 2 logistics are one of the most fascinating subjects I have ever encountered,
and so I have decided to create an entire series dedicated to exploring the logistics
and planning that went into d-day and other battles of World War 2. Starting with the
first episode exploring how and why the Allies chose Normandy as a landing location. That
series will be made with the support of CuriosityStream, a subscription streaming service with thousands
of documentaries and nonfiction titles, and will debut next month on Nebula, a streaming
video platform built by and for independent creators like Tierzoo, Lindsay Ellis, MinutePhysics,
Wendover Productions, and loads more.
Where CuriosityStream is all about big-budget non-fiction videos, we're building Nebula
because we want a place for education-y creators to try out new content ideas that might not
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CuriosityStream loves independent creators and wants to help us grow our platform, so
they're offering Real Engineering viewers free access to Nebula when you sign up at
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By signing up for CuriosityStream you'll get access to thousands of documentaries like
this one called Plane Resurrection that details the restoration of WW2 era planes AND you'll
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JT from Second Thought and Joseph from Real Life Lore.
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Logistics of D-Day series that would just be too risky to rely on YouTube.
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