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.”