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Ikv 91 production and prototype & Ikv 91-105


Sp15
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This thread is part of the Swedish tech tree project and one of the threads where I will go more in depth with sources and information which I have not included in the main thread. As I said in the main thread Im currently sitting on about 30 000 pages of information from the Swedish war archive so if there is anything that is unclear please PM me and I will provide a source

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Ikv 91

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The ikv 91 was a light tank/tank destroyer built specifically to provide Swedish infantry with effective and mobile fire support. Between 1975 and 1978 a total of 212 vehicles were delivered to the Swedish army, these served until the early 2000's when they were retired without a replacement.

 

 

Development


The Ikv 91's development began when FMV (Swedish defense materiel administration) issued a set of requirements for what it called the Ikv m/ny (ikv new) project in 1964. By this time the Swedish infantry was operating a large amount of obsolete ww2 era vehicles in so called assault gun companies. The ikv m/ny was meant to replace all of these with a common platform with improved anti tank capability. However replacing 300 or so vehicles would not be cheap and so the ikv m/ny would have to be much cheaper than a traditional tank to produce. In addition the vehicle would have to operate alongside the infantry in all types of terrain, including the forests and marshland of the Swedish north. Because of this the ikv m/ny was to have a amphibious capability and a maximum weight of 15 tons. This would allow it to cross rivers and make use of roads and bridges in undeveloped areas. To ease development a 9 cm low pressure gun capable of firing modified ammunition from the Pvpj1110 recoilless rifle was chosen as the main armament for the vehicle, though everything from ATGMs to proper 105-120 mm anti tank guns had been considered initially. To make proper use of the terrain in which it was supposed to operate the Ikv m/ny would have to have good gun traverse and a gun elevation of at least -10/+20 degrees. Finally the vehicle had to have a crew of no more than 4 men.

 

Ikv m/ny proposals

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These requirements were sent to three companies, Bofors an established Swedish arms manufacturer who was currently developing and producing the S-tank. Landsverk Sweden original tank manufacturer who had supplied most of Sweden's tanks up to this point & Hägglunds. Hägglunds was the creator of the Swedish army's newly adopted Pbv 302 apc and also its earlier Pbv 301 apc, they had also supplied some of the turrets for the Strv 74 but they had never designed a full tank before. In total well over a dozen proposals would be submitted ranging from traditional casemate tank destroyer style vehicles to turreted and remote turreted light tanks with and without autoloaders. One of the proposals from Bofors even took inspiration from the Strv 103 by adopting a gun with fixed traverse. Ultimately however the more outlandish ideas would be discarded and by 1966 only two competing designs remained.

 

 

Landsverk's Ikv 65 Alt. 5

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Landsverk's Alternative 5 design had started out as a traditional light tank with a fully traversable turret, but this vehicle was later redesigned with a raised engine deck and a limited traverse turret. Its not known exactly why this was done but it is possible that it was done in order to keep within the weight limit and to accommodate the larger engine of this model. This would have been the cheaper of the two ikv proposals that remained at this point.

 

Hägglund's Ikv alt. 1

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The Hägglund's Alternative 1 design on the other hand had started out as a monstrosity which promised not only a fully automated loading system but also a 80 kph top speed and an exceptionally low profile turret. To make their design more viable and cost effective however Hägglunds were forced to remove the autoloader which meant the redesigning the tank for a 4 man crew. Perhaps more importantly the vehicle was changed to have a greater interchangeability of parts between it and the Pbv 302, also designed by Hägglunds. It was largely thanks to this parts commonality that Hägglunds proposal was chosen to become the Ikv 91.

 

Ikv 91 prototype

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In April of 1968 FMV placed an order with Hägglunds for three ikv 91 prototypes.They were delivered starting in 1969 and would end up being used for all sorts of tests and trials leading up to the vehicles adoption. Perhaps the most notable difference between these preproduction vehicles and the final Ikv 91 was the design of the turret, which on the prototypes was equipped with a large commanders cupola. The switch from an optical to a laser range finder on the production ikv 91 allowed for a reduced cupola. Other modifications included the switch from a manual to a fully automatic gearbox, an extension of the engine deck and some minor details such as the placement of the smoke launchers and design of the sideskirts. Orders for the production version were placed in 1972 with an order for 200 vehicles and then another 12 in 1975.

 

 

General characteristics

 

The ikv 91 had a crew consisting of 4 men. The Commander and gunner were placed on the right side of the gun with the loader on the left side. The driver was located on the left side of the front hull. The Ikv 91 Was extremely lightly armored featuring a maximum armor thickness of 20 mm at the front and 12 mm for the majority of the turret. This armor was said to protect against guns of up to 20 mm caliber. On the sides and rear the ikv made use of 4 mm thick spaced armor over a 8 mm base plate, this was enough to protect against shrapnel and machine gun caliber rounds. Despite this lack of protection the tank actually ended up exceeding the original 15 ton weight limit by up to 1,3 tons in the final production version. Due to this increase in weight however additional equipment had to be introduced to keep the tanks amphibious capability.

 

Crew & module positions
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Armor layout
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Much of the drivetrain and suspension of the ikv 91 had been taken wholesale from the Pbv 302 but to meet the high mobility requirements an improved Volvo TD 120 A turbocharged diesel engine was chosen to power the tank. At 2200 rpm this engine produced 330 hp which gave the 16,3 ton tank a power to weight ratio of just over 20,2 hp/t and a top speed of 65-67 kph (depending on the source) with a reverse speed of 11,4 kph.

 

Ikv 91 swimming

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In addition to one coaxial and one external 7.62 mm machinegun used for close defense and anti air the Ikv 91 was armed with a 9 cm low pressure main gun. The choice of a low pressure gun eliminated the possibility of using APDS projectiles but also had several advantages like its lighter weight, lower muzzle flash and its ability to share warheads with existing 9 cm recoilless rifles. Depending on the round used the muzzle velocity could range from 600 m/s (HE) to 830 m/s (HEAT). The main anti tank round used by the Ikv 91 for most of its service life (Slpsgr m/72) was capable of penetrating well over 480 mm of RHA steel at 90 degrees. The improved Slpsgr m/84 round introduced in the 1980's further increased the penetration and introduced a hardened nose cap specifically designed to allow the round to defeat reactive armor modules such as the Israeli Blazer used on the Strv 104. Unfortunately when tested against Soviet ERA modules in the 90's this round proved ineffective due to the high inclination at which the soviet ERA modules were mounted.

 

A total of 59 rounds of main gun ammunition were carried in ammo racks located on the turret floor, behind the turret and to the right of the drivers position. For night fighting the tank was equipped with IR marker lights and two "lyran" mortars on the rear of the turret for use with IR illumination rounds. Also mounted on the turret was two sets of 6 smoke launchers carrying 12 smoke grenades, another 12 were carried inside of the vehicle.

 

 

Ammunition storage

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To compensate for its relatively low muzzle velocity the Ikv 91 was equipped with a state of the art fire control system developed in collaboration with the US based Honeywell corporation. By the use of a laser rangefinder and a ballistics computer the FCS could accurately predict a targets position regardless of its speed and direction. In addition this system was hunter killer capable, meaning that the commander could be ranging targets he spotted for the gunner while the gunner was busy engaging another. An ikv 91 loader was expected to be capable of a burst rate of fire of 4 rounds in 10 seconds and a sustained rate of fire of 8 rounds per minute.

 

Usage

 

The ikv 91 came to be used by the Norrlands & the infantry brigades in their "tracked anti tank companies". 12 vehicles were used per company. In addition to directly supporting the infantry during an attack the tracked anti tank companies were also expected to act as the brigade's "fire brigade" - an autonomous unit that could move across the entire brigades area for surprise attacks. During the 1980's the ikv 91 was also included in mechanized battalions together with Strv 101/102. In 2002 despite several modernization attempts the Ikv 91 was taken out of service with the Swedish military due to its subpar armor protection and firepower. Today several examples still remain in museums and private collections around the world such as the Arsenalen museum in Stockholm and the Bovington tank museum.

 

Ikv 91's and Strv 101 on the move

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In Swedish nomenclature the Ikv 91 was regarded as a tank destroyer/fire support vehicle but from an international perspective the Ikv 91 would have been regarded as a light tank. And this is Indeed this how the tank ended up being marketed internationally as can be seen in this promotional video. Note that the vehicle used for the majority of this video is the modernized Ikv 91-105 variant.

 

Other variants

 

In 1971 Hägglunds under orders from FMV fitted one of the ikv 91 prototypes with a 105 mm L7 gun in a provisional turret with the goal of determining what effects this gun would have such a light chassis. They found that apart from needing to reinforce the hull roof in front of the turret this gun could be relatively easily mounted on the ikv 91 chassis with no drawback in accuracy compared to the Strv 101/102.

Already in 1973 plans were drawn up for an improved 20 ton variant of the ikv 91 known as the UDES 14D. This version would have featured a new enlarged turret capable of mounting the 105 mm L7 and improved armor protection of up to 40 mm. The plans for the UDES 14 were shortlived however as FMV favored other more capable UDES 14 proposals.

 

Ikv 91 with L7

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UDES 14D

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In 1982 the ikv 91 had been evaluated by the Indian army in comparative trials with the AMX 10 PAC 90. The vehicle preformed well and was highly regarded by the Indians, however certain aspects such as the armament were deemed inadequate. Based on the requests made by the Indians Hägglunds began working on what they would call the Ikv 91-105.

 

Ikv 91 105

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As the name suggests this vehicle was a redesigned ikv 91 armed with a stabilized 105 mm gun, specifically the Rheinmetall Rh 105-20 gun. This was essentially a low recoil version of the L7 fitted with a muzzle break and with a longer recoil length. To accommodate the larger gun while retaining the gun depression of the original ikv 91 a new enlarged turret not unlike that proposed for the UDES 14D was constructed. A new gun mantle with a built in IR spotlight was also added for improved night fighting capability, and the coaxial and external MG's were swapped for German MG 3's. To improve the vehicles amphibious capability the hull front was redesigned, the sides were widened by 125 mm above tracks and the rear was lengthened. In addition two hydraulicly driven external propellers were added to give the vehicle a higher top speed while submerged. Due to the decreased angle of the redesigned front the armor thickness was adjusted to compensate. All these changes added up to a total weight of 18 tons, an increase of 2 tons compared to the standard ikv 91. Despite this the mobility of the ikv 91-105 was not substantially worse due to an increase in the engine output to 380 hp.

 

Internal layout of Ikv 91-105

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After all this work the Ikv 91-105 never ended up being adopted by anyone. The Indians and several other countries including the US tested the vehicle but no orders were placed. A variation of the ikv 91-105 was studied as a possible upgrade for the Swedish army's Ikv 91's in the late 80's early 90's. A prototype was constructed but due to budget cuts and doubts about the chassis ability to handle the new gun the project fell through.

 

Ikv 105

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Early in the development of the AMOS 120 mm mortar system which Sweden developed in co-operation with Finland an ikv 91 chassis was used as an test bed. There were also plans to convert ikv 91's to minesweepers or ATGM carriers.


ikv 91 based minesweeper.

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Ikv 91 with AMOS mortar system

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Drawing of Ikv 91 with atgm's
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Data: Ikv 91 Prototype

 

Combat weight: 15,5 ton
Crew: Commander/Radioman, loader, Gunner, Driver
Length: 6410 mm (including gun 8840 mm)
Width: 3000 mm
Height: 2450 mm
Top speed: 67 Kph (-11,4)
Submerged speed: 6,5 kph
Gradient: 30 dg
Side slope: 30 dg
Trench: 2,5 m
Ground clerance: 370 mm
Track width: 450 mm
Ground contact length: 3680 mm
Ground pressure: 0,49 kg/cm^2
Turning radius: 0 m
Vertical step: 0,9 m
Fording: Amphybious
Engine: Volvo-Penta TD 120 A (Diesel 330 hp at 2200 rpm)
Power to weight ratio: 21,2 hp/t
 


Main armament: Kv 90S69
Secondary armament: x2 7,62 mm ksp m/39B strv
Gun elevation/depression: +15/-10 dg
Traverse speed: 20 dg/s
Elevation speed: 10 dg/s
Gun sight: 10x zoom
Ammo: 59 rounds 9 cm, 4000 rounds 7,62 mm, 24 smoke launcer charges
Rate of fire: 8 rpm sustained ("4 rounds within 10 s is possible")
Rate of fire (secondary): 10-12 rounds per second
 

 

Data: Ikv 91

 

Combat weight: 16,3 ton
Crew: Commander/Radioman, loader, Gunner, Driver
Length: 6410 mm (including gun 8740 mm)
Width: 3000 mm
Height: 2320 mm
Top speed: 65 Kph (-11,4)
Submerged speed: 6,5 kph
Gradient: 30 dg
Side slope: 30 dg
Trench: 2,5 m
Ground clerance: 370 mm
Track width: 450 mm
Ground contact length: 3680 mm
Ground pressure: 0,49 kg/cm^2
Turning radius: 0 m
Vertical step: 0,9 m
Fording: Amphybious
Engine: Volvo-Penta TD 120 A (Diesel 330 hp at 2200 rpm)
Power to weight ratio: 20,2 hp/t

 

Main armament: 9 cm kan Ikv 91
Secondary armament: 7,62 mm ksp m/39B strv
Gun elevation/depression: +15/-10 dg
Traverse speed: 20 dg/s
Elevation speed: 10 dg/s
Gun sight: 10x zoom
Ammo: 59 rounds 9 cm, 4250 rounds 7,62 mm, 24 smoke launcer charges, 12 71 mm illumination mortar rounds
Rate of fire: 8 rpm sustained ("4 rounds within 10 s is from ready rack")
Rate of fire (secondary): 10-12 rounds per second

Penetration Slpsgr m/72 @ 90 dg (HEAT-FS): 573 mm
Penetration Slpsgr m/84 @ 90 dg (HEAT-FS): 800 mm (can defeat ERA unless steeply angled)

 

Data: Ikv 91-105

 

Combat weight: 18 ton
Crew: Commander/Radioman, loader, Gunner, Driver
Length: 6660 mm
Width: 3240 mm
Height: 2380 mm
Top speed: 61 Kph (-10)
Submerged speed: 7,5 kph
Gradient: 30 dg
Side slope: 30 dg
Trench: 2,5 m
Ground clerance: 370 mm
Track width: 450 mm
Ground contact length: 3680 mm
Ground pressure: 0,49 kg/cm^2
Turning radius: 0 m
Vertical step: 0,9 m
Fording: Amphybious
Engine: Volvo-Penta TD 120 A (Diesel 380 hp at 2200 rpm)????
Power to weight ratio: 21,1 hp/t
Armor: 30/8+4/8 mm

 


Main armament: Rh-105-20
Stabilization: fully
Secondary armament: 2x 7,62 mm MG3
Gun elevation/depression: +15/-10 dg
Traverse speed: 20 dg/s
Elevation speed: 10 dg/s
Ammo: 32 rounds 10,5 cm, 4250 rounds 7,62 mm, 24 smoke launcher charges
Rate of fire: 6-8 rpm

 

Note: The documentation for the stats of the Ikv 91-105 has been taken from SPHF's private archive. As this information is not publicly available please PM me for exact Information and documents.

 

 

Pictures
 

Spoiler


Ikv 91 walkaround
http://www.primeportal.net/tanks/gunther_neumahr/ikv_91/
http://www.primeportal.net/tanks/olof_nilsson/infanterikanonvagn_91_walk.htm
 

Winter trials with Preproduction Ikv 91

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Additional pictures of Ikv 91-105

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Source's & Historical Refrences

 

Technical specification for Ikv 91 - 1972

https://imgur.com/a/WGkRhi9

Datasheets for Ikv 91 (UDES 13) - 1971

https://imgur.com/a/OlQEER1

Ikv 91 instruction manual - 1980

https://imgur.com/a/x4xN8WX


- Landsverk Blueprint archive (Part of Krigsarkivet in Stockholm) https://riksarkivet.se/krigsarkivet

Book - Svenskt pansar: 90 år av svensk stridsfordonsutveckling - By Rickard O. Lindström & Carl-Gustaf Svantesson http://www.ointres.se/ikv_91.htm
Book - Landsverk i Landskrona https://i.imgur.com/tJ6dJBv.jpg

- SPHF's (swedish historical armor association) private archive

Edited by Sp15
  • Like 6
  • Upvote 13
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  • Senior Suggestion Moderator

Open for discussion. :salute:

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  • 4 months later...

I would love this, be something unique and fun to play with.

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  • 8 months later...
  • 3 months later...

54FvPik.jpg

 

The Ikv 91 was added to the game. I'm a bit surprised the Ikv 91-105 wasn't added as well, seeing how that would fit the gap between the Ikv 91 and Strf 90C (honestly the latter might be a bit over-tiered considering it doesn't have ATGM's, but I dunno).

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  • 4 weeks later...

well

we have the Ikv 91 in the Swedish tree now

Hopefully we will see a variant with a 105mm (L7 or otherwise)

 

also, did any variant of this tank come equipped with thermals?

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  • 10 months later...
  • Technical Moderator

@Sp15 would you be able to potentially provide more details about the Ikv 91-105's reload cycle? Currently on the public dev server, it can maintain a sustained rate of fire of 15 rounds per minute (4 seconds) sustained with an ace crew, and 11.5 (5.2 seconds) with a basic crew.

 

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EDIT: didn't read the bit about private info, apologies. PM sent.

Edited by Optical_Ilyushin

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  • 3 weeks later...
  • Senior Suggestion Moderator

As the IKV-90 previously and now the IKV-90-105 has been implemented with update 2.5 Ixwa Strike,

 

Moved to Implemented Suggestions. :salute:

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