today, we have a guest article from sp15 (NA server), dealing with the S-tank’s development history. I did only some minor edits (typos and such). Enjoy!
Today I’ve decided to write about Swedens most iconic tank the Strv 103 or – as everyone knows it – the S-tank. The reason for this is that the S-tank is the only known hope for a historical tier 10 TD for the European tree and wargaming don’t know what to do with it. Let me explain.
The Strv 103 has a hydraulic suspension, which means in practice that the whole hull moves to aim the gun. This means that Wargaming would have to implement new aiming system for this sort of tank – and Wargaming does not want to do that for one separate tank, but they have stated this:
The fate of the S-tank is still undecided
What I want to do in this article is to explain the history and characteristics of this tank. I hope you take some time to read and consider this tank for implementation.
The origin of the S tank can be traced back to one man and his fascination with self propelled gun designs of World War 2. After World War 2, the Swedish army decided to purchase and evaluate some German armored vehicles.
One of the people, who were assigned to this project, was Sven Berge, who was to design the S tank in the future.
In particular, Berge was interested in German turretless designs, such as the Sturmgeschütz and the Jagdpanzer. These tanks were cheaper and also faster to produce than their turreted counterparts.
They also allowed for greater firepower while not compromising mobility or protection compared to turreted tanks – in fact, the lack of a turret meant smaller vehicle, which in turn meant it was harder to detect and destroy.
With the purchase of the British Centurion tank, the Swedish army also got access to British damage assessments from WW2. This information stated that knocked out tanks were usually hit in the turret and that hits below 1 meter were unusual. A calculation also pointed out that the turret had around 100% higher chance to get hit than the hull. These were not the only elements that inspired Berge however.In fact, Sven Berge had been in charge of the Swedish test and evaluation of the French AMX 13.
This tank featured an autoloader, which in turn meant a crew member could be replaced and the tank could be reduced in size and weight.
There had also been tests by Bofors with a 20 ton assault gun with a 120mm automatic cannon.
Berge was also involved in the development of a new AA vehicle, made by Bofors, which featured a hydraulic suspension.
This all culminated in the idea to build a turretless tank with a fixed gun. Berge came up with the idea over a weekend and he presented it to his boss on Monday. His boss did not get the idea behind this design but nonetheless Berge got more time to develop it.
It took Berge 1 month to come up with first drawings and patents, these were finished on 22nd of October 1956.
The initial design of what would become the S-tank:
He proposed the idea of adjustable hydraulic suspension to move the hull of the tank. The design was meant to have the weight of around 30 tons, would feature a fixed gun with a automatic loader
and the tank was to be manned by 2 crewmembers.
The proposal was given a go-ahead and the development group was put together. Different designs were discussed.
Here is a picture showing the size advantage of a fixed gun over one with traverse:
The fixed gun means less space and crew required. Furthermore, the automatic loader allowed for the ammunition storage to be placed in the back. This meant that safety devices could be put in to protect the crew if the ammo storage was hit. The main drawback behind the concept was that the tank could not fire on the move.
This however was only a small drawback, as turreted tanks from the same era could only shoot accurately when stationary due to poor stabilization. The lack of a turret meant that in an attack, the tank could not be able to react as quickly as a turreted tank. This was not really considered a problem however, since the role of the tank in the event of war would be a defensive one.
In 1957, Sweden considered 3 options for the new tank.
Alternative A: a tank of either English or American design in the 50 ton range and decent mobility (M60 & Chieftain)
Alternative T: a German or French tank in the 30 ton range with good mobility, but lack of protection (Leopard 1 & AMX 30)
Alternative S: the so called S-tank, a small 30 ton tank with good protection and mobility.
Also in 1957, various aspects of the S-tank proposal were tested, such as aiming of the fixed gun. These tests continued on various chassis types, including a Sherman chassis. In 1959, full scale testing of the hydropneumatic suspension was conducted, using the prototype chassis of the KRV heavy tank. During these tests, 2 road wheels were stripped off the KRV to simulate the S-tank suspension, a 20 pounder gun was also used to test the capability of the tank to aim.
KRV chassis being used as a test vehicle:
At the same time, the automatic loader was constructed and the frontal armour was tested on firing range, with the results from these tests being positive.
Now the tank needed an engine, but there were problems because of the confined space, so a compromise was made – instead of one regular engine, the tank would use a diesel engine for fuel economy when needed, and a gas turbine engine for power and speed when necessary. These engines worked together to allow for maximum amount of power.
In 1961 two prototype vehicles were made (S1 & S2). These were used to test the drivetrain, suspension & optics of the tank, and a new commander’s cupola was developed – it was so good that apparently “it is still regarded as the world’s best”. A full scale wooden mockup was also made.
On the left, the S1 – on the right, the wooden mockup:
The tests with the S1 & S2 were positive and in 1963, the production of 10 fully functional pre-production tanks called the 0-series was finished. These were armed with a Swedish modification of the British L7 gun. The gun was lengthened from L/51 to L/62 calibers and it was equipped with an automatic loader, capable of shooting one shot every 3 seconds.The tests with the 0-series continued until 1966.
Strv 103 0-series:
In 1964 the decision was made to start the production of the S-tank.
The alternative S or S-tank was renamed “Stridsvagn 103A” and the first tank became operational in 1967.
Strv 103A and Pbv302:
The Strv 103A weighted 37.7 tons and was equipped with a Rolls-Royce K60 240hp & Boeing 502 10MA 300hp engines. This meant that the tank had the power to weight ratio of 14,3hp/t, which was less than what was hoped for. This was noticed in particular during the testing with the 0-series. In 1970, the Strv 103B was delivered with a 490hp turbine engine, which meant the tank now reached the power to weight ratio of 18hp/t. Both the A and B versions had the top speed of 50kph and a crew of 3.
Any information on the armour of the tank seems to be rather scarce. With that being said, I’m going to use the English Wikipedia page as my source for this and say that the frontal Armour of the Strv 103 was 60mm thick – and before you start saying 60mm is nothing, we need to take the sloping into account.
In this picture we have the armour angles of the Strv 103 and we can clearly see that the upper frontal armour is sloped at 78 degrees. This (if I calculated it correctly) means the effective upper frontal armour of 288mm – almost 5 times its nominal thickness! The lower frontal plate is sloped at 72 degrees, which means that if we assume that it has the 50mm thickness, it would have 161,8mm of effective armour.
Strv 103 in comparison with the Centurion -as you can see, the S-tank is only slightly above 2 meters tall, which means it is easy to hide.
Overall, the Strv 103 is small but deadly tank with an insane amount of protection for its weight.It also has great firepower with its 105mm cannon with the automatic loader, not to even mention its great optics, which have outperformed the Leopard 1 in tests.
Strv 103B in full elevation:
Statistics for the Strv 103A
Crew: 3 (commander, gunner/driver, rear driver)
Armor: 90-100 mm
Main armament: 105mm (automatic loader)
P/W: 14,3hp/t (unlikely that it will get the strv 103B engine)
Engine(s): Rolls-Royce K60 240hp & Boeing 502 10MA 300hp = (540hp)
I hope this explained the S-tank to you a bit, and I hope you enjoyed reading it.
One thing of note here – most of this information (and pictures) comes from http://www.ointres.se/pansar.htm
Pay the site a visit if you know Swedish, it has some great pieces of information.