Strv fm/31 - The Swedish Transformer.

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After WW1 the presence of tanks in modern combat became more and more common.
They offered a protected place for soldiers as well as a great tool for breaking enemy lines.
The Swedish army was quick to hop on this new trend of armored vehicles and wanted a tank of their own.

In the 1930s Sweden commissioned a tank of their own and three companies showed interest.
Those being Bofors, Landsverk and Mogårdshammar. Mogårdshammar had problems with their lead constructor dying and Bofors tanks was decided “Not fit for Swedish conditions”.
And thus AB Landsverk was chosen to build Sweden’s new tank.

The first problem that needed to be solved was mobility. tracks at the time were not great and the max speed of tracked vehicles were not adequate for Swedish doctrine.
It just so happened that in the 1920s Landsverk had been bought by Germany and thus they had early German prototypes to base their designs upon.
And as it turned out, these German prototypes happened to have the solution to the mobility problem.

This solution is called the Wheel-cum-track type tank. Despite its humorous name it was quite a simple and genius way of solving the issue.
Tracked vehicles are slow, wheeled vehicles are fast. So when the tracked vehicle needs to be fast?
Just give it retractable wheels!

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Strv fm/31 in wheel configuration.

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Strv fm/31 in track configuration.

This is the Stridsvagn fm/31. The fm in the name stands for FörsöksModell, which means “Testing Model” or “Prototype”.
It was a prototype tank that was supposed to be used by the Swedish army.
The wheel-cum-track design did manage to increase the tanks mobility on road significantly.
However the added complexity and weight made the tank to vulnerable to enter service.
Combined with the fact that tank track technology had advanced significantly during the development made the wheels on the wheel-cum-track obsolete.
In the end the Strv fm/31 never entered service and was only used as a training vehicle for later tanks.


The Strv m/31 that is already in game.

Mobility wise the fm/31 is kind of a sidegrade to the m/31.
They share the same engine but the older tracks and added weight of the fm/31 gives it a top speed of only 35kph on tracks.
With the wheels however that top speed is increased to 75 kph! Although only on roads.

The mechanism to lower the wheels was automatic and could even be used while on the move,
And thanks to there being two drivers, one in the back and one in the front, it could be driven at the same speed in both directions.

The gun and turret is the same as the m/31 which is already in game. Its stats would be identical.

And as usual, on to some general statistics of the vehicle:
Weight: 11.5 metric tonnes
Crew: 4, two drivers, one gunner and one loader
Armament: 37mm bofors. (Same as the m/31) + ksp 6.5mm
Maximum speed: 35kph on tracks, 75kph on wheels.
Maximum traversable incline: 40 degrees.

In game the Strv fm/31 would probably fit in the premium section of low tier Sweden, however much it pains me to say it.
The Swedish tree in low tier is already pretty fleshed out with several vehicles of almost equal performance.
That combined with Gaijin’s tendency to make cool prototypes into premiums makes it the most likely scenario.
Either way it would probably be a very fun tank to play. Since it wasn’t in service when the APDS round was created it probably should not get it.
Without the APDS it could probably sit quite well at 1.0 though you never know with nimble vehicles, they have a tendency to climb the ranks, so to speak.

Sources:
https://www.ointres.se/strv_fm31_m31.htm

5 Likes

Huge yes!

If we add this gaijin will surely add the road mod on the EBR so YES

This could honestly be a reserve vehicle for Sweden, as it doesn’t get APDS. That would allow for the sabot tanks to be moved up a little! +1

1 Like

Given the Strv m/31 gets it it probably should imo.

I’ve tried to upload a suggestion for this twice now, so im happy someone else was successful in it.

here are some additional sources and more detailed specifications:

Very informative video as he does a (mostly) complete rundown of the vehicle. Also includes numerous clips of the internals of the vehicle.

Basic rundown of the vehicle done by the museum it resides at. Also quite informative and gives a general overview of the vehicle.

Specifications

Most of these are from Sp15’s original forum post, however I have made minor corrections as some information was either incorrect or omitted for unknown reasons.

  • Name: Strv fm/31

  • Type: Light Tank

  • Weight: 11500 kg

  • Length: 5200 mm

  • Width: 2400 mm

  • Height: 2220 mm

  • Crew: Commander / Rear Driver, Driver, Gunner

  • Engine: Maybach DSO 8 (150 hp at 3000 rpm)

  • Top speed: 35 km/h (tracks), 75-80 km/h (wheels)

  • Reverse speed is not specified, however it is said to be able to “quickly reverse”. According to the director of the Arsenalen museum Sweden aimed to have shared parts across vehicles. Without any other information to go off-of, it can be presumed that the Strv fm/31 retains the reverse gears of the Strv m/31 until further information can be found.

  • Wheels take 20-30 seconds to deploy and retract, and can do so on the move.

  • Trench: 1,8 m

  • Gradient: 40 dg

  • Main armament: 37 mm Bofors L/45

  • Secondary armament: 6,5 mm Ksp m/21-29

  • Gun elevation/depression: +25/-10 dg

  • Armor: 6-14mm

  • There are no exact armor values listed anywhere, however judging from video footage one can reasonable conclude that the hull is 14 mm on the front and sides, and 6 mm on the rear, floor and roof. The turret is 14mm all around with most likely 6 mm on the roof. The mantlet is not made of steel, but can be assumed to have been 14 mm had it been.

Here's also a photo gallery

It can be seen in the rear along with the 3 L-10’s in front

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Internal Layout

These are images showcasing the inside from The Chieftain’s video on the vehicle.

Hoping this gets added!