Categories
Swedish armor

CV9040A and B

Sweden (1991)
Infantry Fighting Vehicle – 345 built

Early in the development of the CV90, it was decided that the CV 9040 version should be developed into a family of vehicles comprising four additional variants:

  • CV90 FCV (Forward Command Vehicle)
  • CV90 FOV (Forward Observer Vehicle)
  • CV9040 AAV (Anti-Aircraft Vehicle)
  • CV90 ARV (Armored Recovery Vehicle)
Strf 9040A. Photo: Måns Thuresson

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.

Any increase in weight and volume lead to a negative feedback spiral, as a heavier or larger vehicle requires the upsizing of many subsystems, which in turn lead to more weight and more occupied volume. During the development of the CV90, the designers realized that every useful feature that could be added to the design or its subsystems had a price to be paid in terms of useful volume and weight.

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.

CV 90 track assembly layout. Source: Hägglunds)

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.

Chassis Layout

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.

CV 9040 main layout. Source: Hägglunds)

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.

CV 9040 driver´s station and engine compartment: Left photo: Saddam the explorer, engine compartment photo from Mats Carlsson, Försvarsmakten
Ammunition stowage and escape hatch under the turret. Photo: Hägglunds

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.

The conventional seating position (left) would mean an increased roof height to cover the soldiers sat in the back, but the semi-reclined position (right) reduces the height of the vehicle. The popular ‘babysitter’ seat was the inspiration for the seat design in the CV 9040. One of the requirements was that it should be comfortable to sleep in, something soldiers know is important.
Soldiers sleeping inside a CV9040. Photo: Bezav Mahmod, Försvarsmakten

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.

Four soldiers inside a CV 9040 popping their heads out of the roof hatches to provide fire support; There is a support for 7.62 mm machine-guns on each side of the troop compartment, with the other two soldiers using their personal weapons. Photo: Henrik Svensk

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 CV 9040’s cooling system air outlet at its rear; Photo Niklas Englund, Försvarsmakten
By having a focus on weight and volume, the CV 90 is approximately three tonnes lighter than other vehicles in a comparable role.
Size comparison between the American M2 Bradley and the CV9040. Source: Raino Sommer

Power-Pack

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.

Power-pack with crankshaft coupling for hydraulic pump drive. Photo: Hägglunds

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.

Cold chamber tests in Karlsborg. Photo: Försvarsmakten

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.

Power-pack lift; Photo Mats Carlsson. Photo: Försvarsmakten

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 Ikv 91. Seen here a Tankfest 2018. Photo: Mark Nash

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.

CV9040 track assembly. Photo: Daniel Klintholm, Försvarsmakten

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.

CV9040 Turret

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.

CV9040 firing, note the ejected cartridge case. Photo: Daniel Klintholm, Försvarsmakten

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.

CV9040B turret with a standing commander. Note the closed sight cowl. Photo: SPHF

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 commander of a CV9040 observing his surroundings with the hatch in the ‘umbrella’ position. Note the smoke dischargers and the open empty case ejection hatch. Photo: SPHF

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 right side of the turret with the gunner’s observation periscopes. Photo: SPHF

CV9040 Ammunition

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.

The 40 mm L/70 gun system. Source: Bofors

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.

Newly developed 40 mm ammunition for the CV 9040. Source: Bofors

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.

Strf 9040A turret with ammunition carousel. Photo: Lovisaulrika – improveme.se

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.

CV9040 gun at full elevation: Photo: David Gernes, Försvarsmakten

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.

CV9040 UTAAS sight. Photo: SAAB

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.

CV9040 first turret version on the left, CV9040A turret on the right. Photo: SPHF

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.

CV9040B turret with back-up sight to the left side of the gun. Photo: SPHF

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.

Conclusion

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.

Strf 9040A

Dimensions LxWxH 6.55 x 3.17 x 2.77 m
Weight 23.5 tonnes
Crew 3 (driver, gunner, commander) + 7 passengers
Powerpack Scania DSI14 8-cylinder Diesel engine giving 550 hp (404 kW) with a Perkins automatic 4+2 gearbox
Suspension Torsion bars
Maximum speed 70 km/h
Maximum range 320 km
Armament Bofors 40 mm L/70 autocannon
7,62 mm ksp m/58C machine-gun
Galix grenade launchers
Total built 345 built

Sources

Video presentation of CV9040 prototype
FMV presentation of the CV90 project
Swedish Armour Historical Society SPHF: CV 90 Photo guide, 2010
Sources for further information in Swedish
Svantesson, C.-G. & Lindström, R.O.: Svenskt Pansar – 90 år av svensk
stridsfordonsutveckling, 2009
Presentation of the CV90 project by Rickard O. Lindström
Swedish Armour Historical Society SPHF

About the Author

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.”


Categories
Cold War Swedish Prototypes

CV90 Development

Sweden (1984)
IFV – 2+5 built

Introduction

“The Swedish CV90 (in Swedish Stridsfordon 90) is a family of tracked combat vehicles available in several variants, specially designed to meet the operational requirements for mobility and accessibility in northern Sweden’s roadless forests and marshes. The most common variant in Sweden, the Strf 9040 Infantry Fighting Vehicle (IFV), is armed with a 40 mm autocannon in a turret that can be rotated 360 degrees. It can carry six to seven combat-equipped soldiers. The autocannon fires dart projectile rounds with armour-piercing capability” – Swedish Defence Materiel Administration, the FMV,
The CV90 is one of the most successful IFVs in recent history from an export point of view, and its derivatives are currently operated by seven different European nations (Denmark, Estonia, Finland, The Netherlands, Norway, Switzerland and Sweden). All the export versions of the CV90 have their origin in the development of an indigenous IFV for Sweden.
The CV9040 is the most produced version with a total of 355 units built. Today, the Swedish Army has 559 vehicles including its latest family member, the SSG 120 fitted with Hägglunds’ twin mortar turret, the Mjölner.

Strf 9040A, Photo: Måns Thuresson
The first export order came in 1994 from Norway for the CV9030, which was based on the Swedish chassis with only minor design changes which included:

  • Add-on armor
  • Increased engine output from 550 to 606 hp to match the increased vehicle weight
  • A new squad leader station with periscopes for observation at vehicle rear
  • New suspension dampers and adjustment of torsion bar stiffness, later to be the base for the suspension in CV9040B

The main development for Norway was a new 30mm turret developed by Hägglunds. This turret was based on the CV9025 turret, which was developed for the Swedish Army as an alternative for a possible mixed vehicle fleet consisting of the CV9040 together with a low cost variant with a 25 mm turret.
The CV90 family has been derived into numerous operational as well as experimental variants and has been committed in international operations. 1,280 vehicles have been sold in total and 4.5 million R&D hours have been invested as a base for the most recent version, the CV90 MkIV.

Study phase prior to development

The development of the CV90 family dates back to the Swedish defense resolution of 1977, which made way for a wide mechanization of the army. Studies for new military vehicles in Sweden were made by HB Utveckling AB, a shared company owned by Hägglunds and Bofors.
This design resolution lead to numerous studies for a new light armored fighting vehicle. A large number of vehicle alternatives with different armaments were initially studied. These included not only conventional vehicle layouts, but also articulated ones, all of them in different weight classes ranging from 8 ton upwards.
During the late 70s, the studied vehicles rose in weight due to demands for increased payload in weight and volume. At the same time, use in northern Sweden was prioritized, with a need to be able to operate in deep snow and marshlands. At this time, the opinion was that this was not possible for tanks, an opinion based on the relative poor mobility of the Centurion and S-tank. (In parallel to APC/IFV variants, heavy guns on light platforms were studied and two alternatives were built, UDES 19 on a Marder chassis and the articulated UDES XX-20).
Deliveries of the Ikv 91, with a weight of 16.3 tons, started in 1974 and gave the Swedish Army a vehicle that met the operational needs from a mobility standpoint. The Ikv 91 gave the base for mobility requirements, formulated as “mobility to be equal or better than Ikv 91”. This mobility came primarily from low ground pressure in combination with a favorable design of the track assembly.
In the early 80s, the studies focused on vehicles with the capability of penetrating the sides of contemporary tanks at the same time as carrying a rifle squad of 8 soldiers. The studied armament was in a caliber range from 25 mm up to 60 mm. The threat scenario included helicopters and low flying aircraft, which gave a special focus to the Bofors 40 mm and 57 mm anti-aircraft high-pressure guns.
The 40 mm two-men turret had a weight and volume similar to those of the Ikv 91 turret. As the vehicle also had to carry 8 soldiers, this inevitably lead to an increased vehicle weight at the same time as the demand for role volume increased. The ambition of the design study was to be below 20 ton (which would be later on exceeded).
The dominant factor for vehicle mobility is ground pressure as this gives sinkage and, by that, motion resistance. By comparing existing vehicles, it can be realised that ground pressure increases in proportion to vehicle weight.

As practical limitations exist for track width and length on ground, it was very likely that the studied vehicles would have lower mobility than Ikv 91.
One possible solution to maintain high mobility in spite of a heavier vehicle was to use overlapping road wheels, a design frequently used by Germany during the Second World War. To investigate this possibility, UDES 08 was converted from a Pbv 302 APC to have seven road wheels instead of the basic five.

UDES 08 with 25 mm gun, photo from Ointres
The result was that the measured ground pressure was reduced with a factor of 5:7 and the rolling resistance from soil compaction was reduced proportionally.
Alfons Falk, the author of the article, presented the results from these tests at the 1981 ISTVS conference in Calgary. After his presentation, he was contacted by Professor J.Y. Wong from Carleton University in Ottawa who had recently developed a theoretical mobility model for sinkage and motion resistance of tracked vehicles in soft soils including snow. This use of terramechanic science gave the possibility to evaluate the effects on mobility from the variation of different vehicle parameters.
These simulations were based on measured soil or snow strength under vertical and horizontal loading. The mobility model gave theoretical sinkage and draw bar pull, i.e. traction reserve. This meeting was the start of a two year period of mobility simulations of the early CV90 concepts.
A typical Swedish 1 m deep snow and a Canadian muskeg were used to give necessary input parameters. The first simulations were done with Ikv 91 in deep snow to see if the results were realistic.

Ikv 91 reference simulation. Source: Hägglunds
The result from these activities laid the base for the CV90’s mobility elements. In 2002, the author, Alfons Falk, received the Bekker-Reece-Radforth award at the ISTVS world conference in Vicksburg, USA. This award carries the name of the founders of the terramechanic science, and the author was the first to receive this award as acknowledgment of the CV90’s outstanding mobility.
During the final studies in the early 80s, the concept CV90 gradually evolved to its present design. It was also decided that the CV90 should be a vehicle family based on one chassis for all variants, instead of a number of special-to-role vehicles.
The defined variants were:

  • CV9040 Infantry Fighting Vehicle (Strf 9040)
  • Forward Observation Vehicle (EPBV 90)
  • Combat Command and Control Vehicle (Stripbv 90)
  • Anti-Aircraft Vehicle (Lvkv 90)
  • Armored Recovery Vehicle (Bgbv 90)

In the family, the CV9040 was given design priority and family variants were developed with the best possible commonality, only special-to-role equipment would differ.

Layout for the common chassis approach (Hägglunds)
The overarching goal was to create a role volume not containing any vital vehicle system that was as large as possible. The large open “load area” was the base for the CV90 vehicle family. Of vital importance was that the main components of the vehicle (suspension, tracks, engine, transmission, chassis) were retained from the base vehicle and did not need to go through extra development and maturing. This meant that the designers could focus on the role-specific components of the variants.

CV90 prototype chassis, photo Hägglunds
As a result of the studies, about 500 requirements were issued, defining the specifications the vehicle should adhere to. On top of these, FMV also gave a seven-point priority list for development, in this order:
1. Extreme mobility
2. Anti-armor capability
3. Anti-aircraft capability
4. Survivability and protection
5. Strategic mobility
6. Easy maintenance
7. Development potential

Rigs and mock-ups prior to development contract

In 1984, FMV ordered two rigs, one for mobility trials and the other for weapon tests.

Time schedule for rigs and prototypes (Hägglunds)
The main purpose of Hägglunds’ mobility rig was to investigate the most important requirement, that of having the same or better mobility than the Ikv 91.
Similarly, the purpose of Bofors’ weapon rig was to investigate the behavior of a turret installation with a 40 mm gun turned upside down and also to see the vehicle’s response during automatic firing of an eight-round salvo.
The mobility rig had a first version of the track and propulsion systems. All other vehicle systems (armor, gun, turret) were simplified or not present in order to save cost and time.

CV90 test rig, photo Hägglunds
The mobility test results were very promising, indicating that the mobility requirements could be met. They also showed that mobility increased significantly with the use of the rig’s active track tension system, maneuvered by the driver during driving. The test result was in accordance with earlier simulation results.
The Bofors weapon rig was also simplified and contained mainly the gun and the ammunition magazine. All other vehicle systems (engine, transmission, suspension) were simplified or not present to save cost and time.

Bofors weapon rig mounted on an Ikv 91. Note the ejected spent cartridge. Photo HB Utveckling
The results showed that the gun’s upside down position was feasible together with a powered ammunition feed from below.
When firing an eight-round salvo, the last round was 10 m above target at 1000 m distance. In 1984, there was no requirement to fire on the move. These tests lead to the suspension system of CV9040A, where road wheel stations 1, 2, 6 and 7 are locked when firing.
Extreme mobility and protection are closely linked to vehicle size, as weight of the armored hull dominates, even more so when the vehicle carries add-on armor. The philosophy was to make the vehicle “big on the inside and small on the outside” (i.e. high volume efficiency)
High volume efficiency means good utilization of vehicle volume. A full-scale mock-up was made in parallel with the rig phase in order to check that the vehicle was not made too small.

Full-scale mock-up, photo Hägglunds
Similar vehicles fulfilling the same requirements are usually about 3 tons heavier. A key characteristic of the Strf 90 is high payload to weight ratio.
High volume efficiency is also important for the rifle squad. The Swedish Armour School PS conducted mock-up trials with different seating positions to find out the necessary length, width and height at the rear of the turret. To obtain the required low height, the best seating position was with soldiers facing each other. The first version, Strf9040A, had 4 soldiers on each side.
To improve weight efficiency, the CV90 has less protected sponsons on each side of the better protected central fighting compartment. The photo above is also showing a separate mock-up made to study stowage of soldier back-packs in the right sponson.


CV90 weapon test rig based on the Ikv 90. Illustration by Andrei ‘Octo10’ Kirushkin, paid for with funds from our Patreon campaign

Development contract for design and testing of five prototypes

In 1985, it was formally decided that the full development of the CV90 would commence. Development was carried out by HB Utveckling AB and five prototypes were built.
Hägglunds was responsible for the chassis while Bofors was responsible for the turret. One exception from this split was the 9025 turret, which had its origin from the program of a possible firepower upgrade of the Pbv 302 APC.

CV9025 with Diehl tracks (part of track evaluation activities). Photo Hägglunds.

Prototype design and production

From the start, all prototypes were used to improve reliability, which was extremely difficult as a ten-fold improvement was required compared to the quite reliable Ikv 91. Four prototypes had the same type of clutch and brake steering system as the Ikv 91, while the remaining one had the X-300 transmission as used in the British Warrior (a minor transmission modification was made at the oil filter to avoid interference with the 550 Hp Scania DS14 engine).

CV90 power-pack with X-300 transmission, photo Hägglunds
The X-300 transmission was approximately 100 mm shorter and 35 mm higher than the clutch-brake transmission alternative, which resulted in a raised engine hatch.

Engine hatch for the X-300 transmission prototype, photo Hägglunds
Besides the engine-hatch difference, all five prototypes had identical hulls and fitted with CV9040 turrets.

Rollout of the first prototype, photo Hägglunds. The author, Alfons Falk, is standing to the right together with Hagglunds project manager Liss-Olof Berglund
The CV9025 turret used the same very basic systems as in the one-man 25 mm turret intended for a possible upgrade of the Pbv 302 APC,i.e. manual gun laying and a day sight. Besides the Chain Gun, the Oerlikon 25 mm KBA and Mauser MK 25 (UDES 08) were evaluated.

CV9025 turret, photo Hägglunds. The turret design manager Michael Hortlund in the center, test engineers Jan Wikström (left) and Peter Lindström in front
The CV9025 turret had a smaller diameter, as the Bushmaster 25 mm Chain Gun was smaller in size compared to the 40 mm gun and its 24 round magazine. The Chain Gun’s weight was also considerably lower. An adapter ring was used to enable the turret installation.

Adapter ring for the CV9025 turret, photo Hägglunds
Three prototypes were designated for trials with different configurations of the CV9040 turret. Different solutions for important subsystems such as gun control systems, sights and machine-guns were evaluated.

Early 9040 prototype with unprotected headlights. Gun muzzle pressure caused some damage when the gun was fired in an unfavorable position. Photo Ointres.
A fourth vehicle with a 40 mm turret was the air defence variant which was permanently stationed at Bofors, Karlskoga. This vehicle was fully designated for weapon system tests and was of limited use for chassis reliability tests.

CV9040 AAV prototype, photo soldf.com/images
The fifth vehicle carried the CV9025 turret which was fully tested during the Swedish development. This was of great importance for the first export version, the CV9030 for Norway.

The first CV9030 turret based on an up-gunned CV9025 turret. Note the machine-gun installation and raised engine hatch. Photo: Hägglunds

Test period, maturing of CV90

The maturation progress of a new vehicle is often underestimated regarding both cost and time. The below advertisement from Hägglunds was published in the military press and says that the cost of maturing a military vehicle is much higher than the cost for design and production of prototypes.

The author, Alfons Falk, standing on CV90
The test period for a military vehicle is often two times longer than the time for design and production of test vehicles. During the test period, all designers remain in the project, now fully occupied with design changes from reasons such as:

  • Fulfilling all requirements
  • Occurring failures from nearly catastrophic to detail level
  • Reliability and operational life in general
  • Redesign for improved maintainability
  • Redesign to meet user requirements (often not part of the specifications)
  • Design for producibility

In addition to the designers, many more people are involved. The maturing process could very well be five times more costly than the effort to make the vehicle roll.
Reliability was a very demanding requirement which originated from strategic mobility. One alternative to conventional transport (by rail or trucks) was to drive the vehicles on their own tracks from, for example, middle Sweden to the northern border, a distance of 1000 km, without losing any vehicle on the way.
The given requirement was to have 10 times better reliability than the already-reliable Ikv 91. Due to this demanding challenge, the requirement was met only at the end of the test period.

Test of family variants in parallel with CV9040 production (Hägglunds)
After the serial order for the basic version CV9040, the prototypes were rebuilt into family variants. Due to the high commonality, the variants were produced on the same assembly line as the regular CV9040 in a mix requested by the Swedish Army.
Important for reliability growth was that critical systems or components had fallback alternatives tested in parallel on different prototypes. Of special interest were the tracks and road wheels, as they are dominant with respect to mileage costs. The evaluations ended with the M2 Bradley’s tracks and road wheels as winners.

Road wheels of SSAB high strength steel, photo Hägglunds
During the test period, the vehicle crews consisted of conscript soldiers, however, one vehicle was driven by Hägglunds professional test drivers. An interesting observation was that this vehicle was driven with twice the average speed, but with only half the number of failures. It was an advantage to use conscript soldiers as the purpose of reliability testing is to detect possible weaknesses in design.
To meet the demand for easy maintenance, the Swedish Army workshops conducted a very large number of reviews, gradually improving maintainability. This meant hard work during the whole development!
A reference group from the Swedish Army, ‘the four majors’, had the task of ensuring that the vehicle met the user’s demands for ‘fighting ability’. Several reviews were conducted, all resulting in design changes to improve CV90 for the user (the number of requests for change was also influenced as more majors were involved. Some of these requests came very late).
The most important fallback alternative was the X-300 transmission, as the clutch and brake steer system was not reliable enough. After the decision was made to abandon the clutch and brake, the height of the vehicle’s hull was increased by 35 mm and the turret was moved 100 mm forwards, increasing the role volume correspondingly. After the test period, an additional 6th vehicle was produced having these changes.

CV90 family, photo from Ointres
The CV90 family has recently gone through a life extension program, but almost none of the upgrades were related to the availability or operational life extension of the main automotive components. With CV90, the Swedish Army has a vehicle to be proud of.

Sources

Video presentation of CV9040 prototype: https://youtube/WdhewPo0Ur8
FMV presentation of the CV90 project www.fmv.se/sv/Projekt/Stridsfordon-90/
Swedish Armour Historical Society SPHF: CV 90 Photo guide, 2010
Sources for further information in Swedish
Svantesson, C.-G. & Lindström, R.O.: Svenskt Pansar – 90 år av svensk
stridsfordonsutveckling, 2009
Presentation of the CV90 project by Rickard O. Lindström www.ointres.se/projekt_strf90.htm
Swedish Armour Historical Society SPHF www.sphf.se/svenskt-pansar/fordon/stridsfordon/

About the author

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.”