Kingdom of Sweden (1953-1984)
Medium Tank – 225 Built
After the Second World War, Sweden was in urgent need of modern tanks. Their current medium tank, the strv m/42, was horribly outdated, being armed with a short-barreled 75 mm gun. The Swedish military was certainly impressed by French AMX-13’s and considered buying them, but eventually they concluded that their armor was too weak to fulfill their needs, along with several other flaws pointed out by General Swedlund. The deal with the French was cut-off and the Swedes eventually decided to buy the British Centurion, which offered significantly better protection against nuclear weapons and conventional weapons.
However, the need for a light tank still persisted. Designing a completely new tank would take too long, around seven years, so instead the Swedes chose to reuse the chassis of the wartime strv m/42.
The idea of upgunning the strv m/42 had been proposed earlier, in 1944. The design would feature a new turret complete with a new gun and autoloader. The turret was named “delat torn”, meaning “split turret”, because the autoloading mechanism would split the turret into two separate compartments. The gun was placed far back in the turret in order to reduce the barrel overhang. A mockup of the turret was made and tested in 1944 and was later prototyped in 1945, but tests in 1946 proved that the design was flawed.
The idea to overhaul the strv m/42 to improve its performance was brought up again in 1953. To revive this old chassis, a new turret was needed in order to fit a more capable gun. Firstly, it was considered to put the turret of the recently studied AMX-13 onto the chassis, but this was not deemed possible as the turret ring was too small. Therefore, a completely new turret was designed. The gun of choice was the 7,5 cm lvkan m/36, one of the most effective Swedish heavy anti-aircraft guns. Modified as a tank gun, it was capable of penetrating 260 mm armor at an angle of 90 degrees at point-blank.
In early 1954, two prototypes were ordered by the Swedish military. One of the main reasons this project was ambitiously supported by the military was the fact that the new turret modification was cheaper than buying a foreign tank. Because the old strv m/42 turrets would later be used as fortification turrets, the new turret could not reuse any of the old parts. As the strv m/42 EH was only available in small numbers and suffered reliability issues because of its Volvo engine, the double-engined strv m/42 TH and TV variants were chosen to mount the new turret on.
The new turret had a futuristic look, being heavily sloped on all sides. Crew conditions were certainly improved over the Strv m/42, with the roomier turret making operating the tank a lot more comfortable. In order to keep production simple, many of the Centurion’s components were used, such as the turret traverse override, the sights, smoke dischargers, sextant and many more. The back of the turret was occupied by an industrial Volkswagen engine, providing power through an electric generator for ventilation and heating. The unique design of the turret, with a specialized gun mantlet, enabled the gun to depress up to an impressive -15 degrees. However, the armor protection was quite disappointing, only 20 mm at best. The armor was kept modest in order not to add any additional stress on the already heavily overloaded suspension.
The original recoil system for the gun had to be replaced, as it was far too big to be mounted in a turret. Besides replacing the old recoil system with a new one, the barrel was slightly cut down as well. A new balancing component for the gun, invented by engineer Sven Berge, who would design the strv 103 later in his career, was also tested and proved to be satisfactory. New APDS (Armor Piercing Discarding Sabot) ammunition further improved the anti-armor capabilities of the gun. The hull machine gun placed on the right side of the driver was removed in order to create more room for the ammunition, as the new shells were much longer than the shorter shells the strv m/42 used. An 8 mm ksp m/39B strv machine gun was stationed on top of the turret and another one was placed coaxially.
Chassis and Body-on-Frame
The heavier turret meant that the chassis had to be revised. The expected weight increase was calculated at 1.5 tonnes, an estimation far from reality. In fact, the increase turned out to be more than double the planned weight increase, 3.5 tonnes. As a result, the front was reinforced, the shock absorbers were replaced with improved ones and the steering mechanism was changed. The tracks were slightly widened, making the ground pressure 25% less, a much needed improvement. Changes to the driver’s hatch were also made. The hatch received a double prism periscope, but the driver did have a harder time getting in and out of the tank. This was because the turret traverse blocked the hatch and prevented it from fully opening up. Plates were put (Note: not welded, they were apparently attached to hinges) over the steering gear hatches in order to make the vehicle NBC proof.
Engine and Other Driving Mechanics
The engines were replaced by the more powerful Scania-Vabis 607 engines, which themselves were improved as well by replacing the carburetor with direct injection. They now delivered 340 hp as opposed to the 325 hp on the original strv m/42. This also resulted in much lower fuel consumption and allowed the engines to function properly at temperatures as low as -25º C.
The radio equipment consisted of 3 independent radios: one for internal communication, one for communication within the battalion and one to communicate with the infantry. Just like most German wartime vehicles, a laryngophone (throat microphone) was used for local communication.
Tests at Särna proved to be successful and more modifications were added to the turret, such as a spare road wheel, smoke dischargers and a turret basket. The idea of attaching a fuel trailer to the tank was abandoned after it was made possible to hang 10 jerry cans at the back of the vehicle, as it was much more practical. This would give it a wider range during mobilisation, but it was eventually decided not to add the jerry cans at all.
Tests were conducted with three different caliber weapons in order to measure the effectiveness of the turret armor:
Firstly, a 20 mm “tubkanon” (a smaller caliber gun inserted into a larger caliber one, usually used during practice in order to reduce costs) was fired, using 20 mm slppjr m/42 rounds. It proved unable to penetrate the turret front, however, the sides were consistently penetrated from a distance of less than 300 m.
Lastly, the 75 mm gun of another strv 74 was fired, using 75 mm slppjr m/49 rounds. It was able to penetrate the turret mantlet from a distance of 1,400 m and cause significant damage to the interior. Its effective distance could quite possibly be more, but this was not tested.
After the design was completed, the production of the two prototypes could begin. The first prototype had a wooden mockup turret, roughly presenting how the strv 74 would look like. The same ammunition as on the pvkv m/43 was used, which made production even cheaper.
After satisfactory tests, manufacturing the production series of strv 74 began in 1957. 225 vehicles were ordered, and the orders were equally spread among the companies Hägglunds & Söner and Landsverk which produced military equipment. Two variants of the strv 74 were produced: the H-variant and the V-variant. The H-variant was based on the strv m/42 TH and the V-variant on the strv m/42 TV. The differences between these versions being only minimal. The gearboxes differed from each other, one being mechanical and the other hydraulic. The order was fully completed in 1960.
The strv 74, just like all other Swedish Cold War tanks, never saw combat. They were dispersed among 4 armored brigades, each receiving 48 tanks. The crew consisted of 4: a commander, a gunner, a loader and a driver. Even though the strv 74 was originally designed as a light tank, the military decided to turn them into infantry support vehicles in the 1960s. Their numbers started to decline when the new ikv 91 entered service, as it was much more efficient in its role of infantry support. The new 90 mm gun it was equipped with provided significantly better anti-armor capabilities than the 7,5 cm kan strv 74. The remaining strv 74s were either stored and kept as reserves or dedicated to other secondary roles. The very last of the strv 74 was retired in 1984. Some of the turrets were recycled and placed on bunkers along the coastline (the so-called ‘värntorn’), staying there up until the late-90s
Conclusion and Fate
The Swedish military considered the project to be a success. Had they bought the French AMX-13 instead, their expenses would have been SEK 80 million (roughly 8.5 million USD) higher, quite a considerable amount. Opinions on the tank however still remain mixed. The profile of the vehicle was quite high and the torsion bars were heavily stressed under the turret’s weight. Many crew members had positive reflections about the vehicles, maintaining that as soon as you ‘had come to know their personality’, they would function properly.
A few Strv 74s have survived to this day and are currently stored or on display at the Arsenalen Museum, the Föringen P5 Museum, Försvarsmuseum Boden, the Kubinka tank museum, the Hässleholms Museum, the Gotlands Försvarsmuseum, the Saumur Museum and the American Armored Foundation Museum. Some were also used as targets on firing ranges.
Illustration of the Stridsvagn (strv) 74, produced by Tank Encyclopedia’s own David Bocquelet.
The basic design philosophy of the CV9040 emerged from the few overarching requirements given by the Swedish Defence Materiel Administration (Försvarets materielverk, FMV) in a priority list, with mobility in northern Sweden being at the top. This emphasized the necessity to reduce the vehicle’s weight without negatively affecting the armament and protection. As the armored hull took up most of the weight, the philosophy was to make the vehicle “big on the inside and small on the outside” or, otherwise said, the vehicle layout had to be as volume efficient as possible.
Terramechanic simulations undertaken during the development stage led to the conclusion that the track ground contact length should be as long as possible in order to ensure a low ground pressure and high mobility even on soft terrain. At the same time, the number of road wheels should be as large as possible and they should be arranged close together in order to create an even distribution of the vehicle’s weight.
In order to have good steering performance, the ratio between the track ground contact to the distance between centerlines of the two track center lines should not exceed 1.7. This put an upper limit on the vehicle length, as the width was already limited by external limitations for road and rail transport.
In order to ensure that the vehicle would not get stuck on obstacles, the armored hull should not protrude too much in front or behind of the track assembly. These mobility concerns more or less determined the maximum possible length of the armored hull and, thus, the maximum size of the role-specific volume. The role-specific volume is the internal vehicle volume left after subtracting the volume needed for the armor, suspension and automotive components.
The CV 9040 has a three-man crew consisting of a driver, a commander, and a gunner, with the commander and gunner operating the turret. In the rear of the vehicle, a rifle squad with eight fully equipped soldiers is carried, who can disembark through the rear doors. This was later reduced to seven men in order to free up space for more equipment.
It was preferred to have the load area rectangular in shape and as long as possible. It was also decided that no other vehicle systems, such as the transmission or fuel tanks, should intrude in the role-specific area in order to provide a common base within the vehicle family. The length of the role-specific volume was increased by the use of a short power-pack. For this, the natural engine choice was the Swedish Scania DSI14 V8 diesel giving 550 hp.
By placing the cooling system in the rear of the right-side sponson, the driver´s station and the engine compartment could be efficiently placed side by side at the front of the vehicle, without any other ergonomic compromises. The CV 9040 turret has a shallow basket offset to the left side and above the bottom of the track sponson.
The dimensions and volume needed for the rifle squad were determined during early mock-up tests made by the Swedish Army. In comparison with the American M113 APC, the troop area in the CV9040 is taller and approximately 200 mm wider.
The space needed for a sitting soldier is directly linked to the vehicle’s internal volume and the sitting position is also closely related to the vehicle’s width and height. In the CV 9040, the soldiers’ seats have a “relaxed” position that lowers the required height of the compartment and of the vehicle. Mine tests with instrumented test dummies have shown that the seats gave good and well-distributed support for the backbone which reduced the risk of severe injury from explosion shocks from underneath.
Early full-scale complete-vehicle mock-ups showed that an inclined hull rear wall was optimal for exiting the vehicle. This also gave a shortened the hull bottom, and it eliminated any issues related to the lower hull protruding beyond the track assembly.
The roof above the rifle squad has a 1° inclination with the purpose of increasing the height of the rear door. Two large, rectangular hatches are located on the roof, allowing for close fire support from two soldiers on each side.
Size of the CV 90 Compared With Other IFVs
The low frontal height of the CV 9040 was made possible by having the radiators in the rear part of the right sponson instead of above the engine. Due to this placement of the radiators, all of the major systems in the vehicle’s front are at the same height, an important factor for high volume efficiency.
The CV90’s 550 hp power-pack consists of a Scania DSI14 engine built together with the X-300-5 transmission originally developed by Detroit Diesel Allison for the M2 Bradley.
The basic Scania truck engine was modified for a dry sump lubrication system to reduce the engine height and allow for operation at large vehicle inclinations.
The X-300 transmission was first used in the British Warrior IFV under the X-300-4B designation. It is a fully automatic cross-drive transmission offering four forward and two reverse gears driven through a torque converter with a lock-up clutch.
Steering is continuously variable (meaning the vehicle can turn with any turning radius) with true pivot turn in neutral (meaning it can turn on the spot) which is achieved with hydrostatically controlled double differentials. Service and parking brakes are incorporated into the transmission and they are hydraulically applied with mechanical back-up.
The Swedish version has the designation X-300-5. The main difference is that the transmission oil filter is inclined to enable a direct assembly to the engine.
During cold chamber tests, excessive oil pressure occurred, leading to transmission damage, a significant problem for a Swedish IFV given the harsh winter climate. Modifications to the transmission were introduced to limit pressure build-up. The cold start problems were solved by these modifications together with the use of synthetic oil with better low-temperature viscosity.
The power-pack is designed with a minimized number of connections in order to enable a fast exchange of the complete unit without drainage of fluids. The hydraulic system’s reliability is closely linked to oil cleanliness and it is therefore important to avoid opening the system at a power-pack lift.
The complete hydraulic system is located in the chassis, there is no power-pack hydraulics. The pump unit is located in the rear part of the engine compartment and the pumps are mechanically driven from the engine crankshaft. A disconnect of the drive shaft is the only action at power-pack lift.
Maintenance and repair are also possible without a power-pack lift as most subunits are accessible from inspection hatches in the engine compartment walls.
CV 90 Suspension and Tracks
As with the CV90 in general, the suspension was designed with efficiency in mind. Besides being weight-efficient, the suspension also has a low height in order to allow as much volume as possible inside the hull sponsons.
The Infanterikanonvagn 91 was the first armored vehicle in the Swedish Army that met the mobility requirements for use in northern Sweden due to low ground pressure in addition to a favorable suspension and track design from a mobility standpoint. This vehicle was the natural starting point for the design of the CV90 track and suspension system.
The Ikv 91 had six road wheels. Each was 670 mm in diameter and had 220 mm of travel. The bottom of the sponsons acted as a stopper for the road wheels, preventing the torsion bars from being overloaded. The large road wheel diameter, in combination with the limited road wheel travel, made it possible to use conventional linear shock absorbers.
The road wheel diameter of the CV90 is smaller than that of the Ikv 91 in order to enable the installation of seven wheels in a densely packed configuration. The M2 Bradley’s tracks and 610 mm road wheels were a natural choice to use, with the additional benefit of ease of production. The increased road wheel travel in the CV90, together with these smaller wheels, means that there is no room for conventional linear dampers.
The CV90 rotary dampers exist in two versions, the first one is designed to cope with the high gun recoil at salvo firings, being lockable. The introduction of a stabilized turret in the CV9040B upgrade opened the possibility of introducing a new damper which did not have to support locking in place for firing.
The 40 mm gun in the CV9040 is based on a modified 40 mm L/70 towed anti-aircraft gun, but inverted with the ammunition feed from below. The gun can fire single shots or salvos of 4 or 8 rounds, with an automatic rate of fire of 5 rounds/sec. The spent cartridge cases are ejected upwards and forwards through a hatch in the turret roof.
Additional armament consists of a 7.62 machine gun and two banks of Galix smoke dischargers that fire IR concealing smoke grenades. The 7.62 mm coaxial machine gun is linked to the 40 mm gun and aimed from the main gun’s UTAAS sight. The turret can be rotated 360 degrees and has an electric gun drive system with a manual back-up in both elevation and traverse. The turret houses two crewmembers, the commander and the gunner, sitting on either side of the Bofors 40 mm L/70B gun system.
The commander has seven fixed periscopes for all-around visibility. The hatch can be locked in an “umbrella” position enabling the commander to have direct observation with overhead protection.
The gunner has the UTAAS IR-sight in front. The top module of the sight has an armor protection cowl that can be opened from inside the turret. The gunner is provided with three periscopes for observation to the right of the turret.
The ammunition magazines are divided into three eight-round compartments. Each compartment is loaded with one type of ammunition. The change from one compartment to another is done by sliding the magazine sideways. With those three compartments, different ammunition combinations can be fired in the same salvo.
One basic requirement was that all types of existing L70 ammunition should be usable by the CV90’s gun. In addition to the existing types of High Explosive (HE) ammunition, a new Armor Piercing Fin Stabilized Discarding Sabot (APFSDS) ammunition was developed.
In order to further enhance ammunition performance, the new programmable 3P ammunition was introduced (3P ammunition – Prefragmented Programmable Proximity fuzed ammunition). A video of the 3P ammunition in use can be found HERE.
The 3P bursting munition has a programmable multi-function fuze that can be set in one of six modes in order to achieve the best effect on target. Each 3P fuze is automatically and individually programmed by a Proximity Fuze Programmer which continuously receives data from the Fire Control Computer. Immediately before firing, the fuze is programmed to the selected mode.
Reloading the gun is done by a rotatable carousel that is easily accessible by both the gunner and the commander. This carousel can store 48 rounds and is a part of the turret basket.
UTAAS Sight and Fire Control System
The basic requirements for the fire control system come from the seven-point priority list. Namely, it has to be effective against land targets and, at the same time, be effective against low flying aircraft and helicopters.
UTAAS is short for Universal Tank and Anti-Aircraft Sight and it is designed to be effective against both ground and air targets. The design of the top module allows for large lead angles in both azimuth and elevation that are essential for effectiveness against fast aircraft.
The sight is of a modular design with an integrated fire control system that includes both a ballistic calculator and a variable repetition frequency laser rangefinder for both ground and air target capability.
UTAAS has an independent line of sight that enables the operator to retain the target in the center of the reticule during the entire aiming and laser range-finding sequence. No re‑aiming is needed. Gun-laying is automatically controlled by the fire-control computer.
Night and all-weather operations are enabled by a thermal camera integrated to the sight. A monitor at the commander’s station gives access to the IR picture from UTAAS.
CV9040 Variants in the Swedish Army
The first 9040 serial vehicles were delivered in 1994, with the last deliveries being completed in 2002. Originally, these vehicles did not have a fire on the move capability due to the lack of a gun stabilization system.
The later produced CV9040A version can easily be recognized by the addition of a damping cylinder on the turret front that reduced gun oscillations during movement.
A number of modifications were introduced during production, primarily to improve firepower and to allow for firing on the move. All the first series of Strf 9040’s were later rebuilt to the same standard, named CV9040A. In addition to turret modifications, more storage and better emergency exits reduced the number of seats in the troop compartment to seven.
In total, 209 Strf 9040A have been produced or converted. Of these, one vehicle was rebuilt to an electronic warfare vehicle. All the remaining Strf 9040A vehicles are still in service with the Swedish Army as of the writing of this article.
The 146 remaining CV9040 were all produced to the CV9040B standard. The Strf 9040B turret has an improved stabilization system for firing and observation on the move and the external damping cylinder was removed.
Important inputs for the suspension redesign of the Strf 9040B variant came from the Norwegian testing of the CV9030, where early tests of firing on the move clearly showed the necessity for an improved suspension system. These tests included firing at different vehicle speeds on an obstacle track representing extreme rough terrain. During these trials, it was recognized that the performance of the suspension system was an essential part of achieving a good hit accuracy.
With the fully stabilized 9040B turret, the suspension dampers could be redesigned to only account for mobility aspects. Above the dampers, a new set of torsion bars was introduced having lower spring resistance, leading to better crew comfort and improved hit probability at high vehicle speeds.
146 CV9040Bs were produced and 55 vehicles of those are upgraded primarily for peacekeeping missions. The Strf9040B1 and Strf9040C versions are upgrades to already produced CV9040B´s.
Strf 9040B1: 13 Strf 9040B vehicles were modified for international peacekeeping missions, having a 3P ammunition programmer, climate control and anti-spall liner.
Strf 9040C: 42 vehicles were upgraded for international peacekeeping operations. This version has add-on armor, laser filtering in all periscopes and tropical grade air conditioning. Due to the bulk and weight of the upgrade, only six soldiers are carried.
The Strf 9040 were deployed with combat units spread all over Sweden for home defence and training. The Swedish Strf 9040, 9040A, and 9040B did not see any combat action. Only the Strf 9040C version saw action in Liberia and in Afghanistan. The CV90 platform also saw action with other countries, but the Strf 9040, A and B were not tested in actual operations.
The Strf9040 was a success for the Swedish army, which not only acquired hundreds of vehicles for its own use, but is also planning to upgrade them in order to keep them in service for the foreseeable future. The Swedish army also uses other variants of the CV90 chassis for other roles.
The Strf9040 did undergo a series of improvements during production and upgrades after its entry into service, mainly dealing with gun stabilization and mobility aspects.
The true claim to fame of the Strf 9040, however, is the fact that the CV90 platform has been a worldwide commercial success, with six other European nations operating hundreds of CV90 vehicles. The CV90 is also proposed to several other countries looking to replace their obsolete IFV fleets.
At this point, the CV90 is the most common Infantry Fighting Vehicle used by the nations of the European Union and will probably play an important role if a common EU army ever comes to fruition.
A Swedish Strf 9040A in a usual Swedish three-tone camouflage scheme. Illustrated by Tank Encyclopedia’s own David Bocquelet.
6.55 x 3.17 x 2.77 m
3 (driver, gunner, commander) + 7 passengers
Scania DSI14 8-cylinder Diesel engine giving 550 hp (404 kW) with a Perkins automatic 4+2 gearbox
Bofors 40 mm L/70 autocannon
7,62 mm ksp m/58C machine-gun
Galix grenade launchers
Alfons Falk graduated in 1967 from the Royal Institute of Technology (KTH Stockholm), majoring in aircraft engineering. In 1975, he started his employment at BAE Systems Hägglunds and became the head of armor vehicle design in 1979, later to include test and verification. Being the head of all armored vehicle design, he has been responsible for the development of the CV90 for Sweden and thereafter for CV90 export versions.
In 2005, The Society for Swedish Mechanical Engineers (SMR) presented him with the Ljungström Medal, an award given only once every three years. The medal was given with the following commendation:
“CV90 – today the most modern IFV in the world – has been a great success in Sweden and internationally. Alfons Falk’s wide knowledge, commitment and ability to transfer operational requirements to excellent technical solutions from system level to detailed design have been decisive for the success of all BAE Systems terrain vehicles. His systematic way of working has changed the development culture within the company.”