Category: WW2 Swedish Prototypes

Categories
WW2 Swedish Prototypes

The Morgårdshammar Tank Program

Kingdom of Sweden (1927-1930)
Tank – None Built

With roots going back to 1610, Morgårdshammars Mekaniska Verkstad AB (Morgårdshammar’s Mechanical Works Joint-stock company) was officially created in 1856. It was established as a foundry near the settlement Morgårdshammar in Bergslagen, Sweden, a region with a long history of mining and metal industry. After various developments and changes of operations, including gaining its current name, Morgårdshammar became a modern industrial plant by the early 1900s. The primary focus of the company at the time was the production of heavy mining equipment. An attempt to enter a new direction was made in 1927, when Morgårdshammar reached out in order to start experimenting in tank design. This was grounded on extensive experience with heavy machinery in combination with what was claimed to be a genuine patriotic intent to arm the Swedish Army with a modern tank produced indigenously.

Early tank acquisition

In 1923, Sweden had only fielded tanks for a single year. This force was made up of the ten LK II tanks bought from Germany after the First World War, which were known in Sweden as the strv fm/21s. Already, a foundation for future requirements for a new Swedish tank had been laid out based on a request from the state council. These requirements were created by Major Bertil Burén, the first commander of the Swedish tank battalion who would go on to be known as the father of the Swedish tank arm.

In 1925, the Swedish government granted a sum of SEK 400,000 (USD 1.1 million in 2020 values) for the acquisition of more tanks. The head of the general staff finally established requirements for a new Swedish tank in 1928:

  • Maximum weight of 12 tonnes
  • Armor to stop 37 mm cannon fire
  • Armament consisting of both a cannon and a machine gun
  • Good mobility in Swedish terrain, an average speed of 20 km/h on-road and half that in relatively difficult terrain

Burén had gained experience with the tank tactics and equipment of a major power in 1926 while visiting the Seaforth Highlander Regiment in Aldershot, Great Britain. It would be in the following year that the process of acquiring a new tank could begin. A Swedish delegation, headed by Burén, was sent to investigate the subject of tank development in Europe at the time. It would end with disappointing results, as no suitable foreign design could be found. The new design would instead have to be one of Swedish origin.

During their trip, the Swedish delegation visited Vienna, Austria. Between June 18 and 19 1927, discussions on the subject of tanks were held with the Austrian Major and tank theorist Fritz Heigl, known at the time for his publication Taschenbuch der Tanks. He was also responsible for the design of armored cars operated by the Austrian military, which was not allowed to operate any tanks due to the restrictions imposed by the Treaty of Versailles. Bertil Burén had previously corresponded with Heigl regarding tank production in Sweden for a Chinese warlord in northeastern China. The allure of a large sum of money certainly functioned as motivation and the project was highly secret. However, as the warlord in question was removed from power, this idea fell through. Heigl showed keen interest in equipping Sweden with a modern tank during the meeting, although the delegation was forced to lower his expectations on the Swedish economy and interest from the Swedish military.

Drawing of components for Proposal A and a comparison of it next to drawings of the Swedish strv fm/21, French Renault FT and British Vickers Medium Mark II. Photo: Warspot.ru via Krigsarkivet

An indigenous tank

In December 1927, Bertil Burén was contacted by two representatives from Morgårdshammar. Their intent was to develop a tank for the Swedish Army on their own initiative. Whether Morgårdshammar would manage to produce sufficient funds to develop a modern tank came into question, to which the representatives replied that Morgårdshammar was willing to make economic sacrifices due to patriotic reasons. This resulted in contact being established between Fritz Heigl and Morgårdshammar, with a subsequent meeting resulting in a contract between Heigl and Morgårdshammar. In the contract, Heigl bound himself to deliver complete technical drawings which were to be approved by the Swedish tank battalion and, through this, get both continuous payments as well as a percentage of profits from each delivered tank. The Royal Army Material Administration’s Artillery Department was then informed of the plans and invited to join the project, something which was promptly rejected because of doubts concerning the funding of the project as well as lacking interest. Burén proceeded to provide Heigl with roughly outlined requirements for a Swedish tank. An initial maximum weight limit of 9 tonnes was set, but this was later raised to 12 tonnes with bridge capacity in mind.

Despite hearing of the Artillery Department’s negative response, Morgårdshammar went ahead with their project. Bertil Burén visited AB Bofors’ director with the intent of gaining support for Morgårdshammar’s project, but he demanded SEK 400,000 before even commencing experimentation. As such, Burén was forced to continue by inquiring with artillerymen employed at Bofors concerning tank armament, and with Scania-Vabis on the subject of engine choice. Morgårdshammar’s head engineer Bjarme believed in the prospect of using a Maybach 100 hp engine, which Heigl viewed as ungainly, but he was unable to come up with a suitable alternative at the time.

In 1927, Heigl started sending drawings as well as letters to Burén and head engineer Bjarme on a weekly or bi-weekly basis. With the intent of retaining interest in the project, Burén gathered his officers from time to time to review progress. In February 1928, Fritz Heigl visited Sweden. He arrived at the Göta livgarde (I 2) infantry regiment’s tank battalion, commanded by Burén. For the first time, Fritz Heigl, an established tank theorist, got to step into a tank and drive it, something he did with joy. The tank in question was most likely an Strv fm/21. He only stayed in Sweden for a few days however as he soon fell sick due to a wound sustained during the Great War and was forced to return to be treated by a doctor in Austria. After a few weeks, the drawings started arriving once more.

Armament was discussed in a letter from Major Burén dated February 1928. Three primary options were considered, all of which were already finished designs in order to reduce costs. These were the Bofors 57 mm “coastal defense gun” M/16, the Skoda 37 mm L/27 infantry gun, and the Bofors 47 mm L/33 infantry gun. The 57 mm gun was most likely actually a 57 mm kanon M/16 which, according to Burén, was used in coastal fortifications at the time. This gun could possibly be borrowed for the first prototype, but was believed to result in too large of a turret and subsequently an overly heavy vehicle. The 37 mm infantry gun meanwhile was of the same type that had previously been used on the Swedish Strv fm/21 during trials and on the Czechoslovak Kolohousenka tank. This gun had already shown good performance during trials and a number of guns were already available. At the time, Major Burén recommended that Major Heigl should design the vehicle to mount the Skoda gun, but that room should be made available to use larger guns. The 47 mm infantry gun, on the other hand, had French connections and was eventually preferred during the design process, being used in technical drawings. Autocannons were also discussed, these being of 20 mm caliber. An Oerlikon design that had been tested in Sweden was mentioned most prominently, but Madsen and Armstrong models then in development were also brought up.

What is believed to be a 57 mm bevakningskanon M/16 on a tripod aboard a coastal defense ship of the Sverige-class during the early days of the Second World War. This gun is closely related if not identical to the 57 mm kanon M/16. Photo: Tornsvala.se

By this point, it was still expected that the tank would use the Schwarzlose water-cooled machine gun already in service with the Swedish Army and used on the Strv fm/21 as the “6,5 mm kulspruta m/14”. However, it was acknowledged that these may come to be replaced by Colt machine guns, as was eventually the case with the introduction of the water-cooled “6,5 cm kulspruta m/14-29” which was based on a Browning design. However, the air-cooled machine guns in the technical drawings are likely intended to represent air-cooled Browning models, something which was not introduced in Swedish tanks until a decade later.

By the spring of 1928, Bertil Burén felt a personal responsibility for the tank battalion, Major Heigl’s efforts, and Morgårdshammar to the degree that he was willing to sacrifice a promotion to remain active on the project. The Artillery Department’s construction department reported that only SEK 60,000 could be made available for the creation of a prototype.

On 15 October 1929, Morgårdshammar made a first offer to produce a tank prototype in Sweden. The offer argued that Morgårdshammar’s experience with heavy machinery and vehicles, including tracked loading machines, made them a suitable candidate for tank production. Success with such vehicles had inspired the company to develop a tank specifically designed for Swedish needs. In the offer, it was stated that the proposal had not yet been finalized and that further development was required. However, by cooperating with Major Heigl, it would be possible to produce a tank equal and in some regards superior to foreign models of the time. This tank prototype would be produced in soft metal but designed in such a way that this could be replaced by armor plate at a later date. The vehicle would also lack armament, weapon mounts, and vision devices. On the other hand, it would generally possess similar mobility to the envisioned production model. The final development of this tank would be a collaboration between Morgårdshammar, Major Heigl, and AB Scania-Vabis, which would assist with drivetrain components. Should the offer be approved, the tank battalion’s officers would also be involved in order to achieve an optimal result from both a military as well as a technical standpoint. Interestingly, Morgårdshammar explicitly noted that any further improvements to the design after finalization or potential cost overruns would be dealt with at the cost of Morgårdshammar. The tank prototype would be built at a cost of SEK 70,000 in around 15 months.

Kolohousenka tank, specifically the KH-50, equipped with the same 37 mm Skoda L/33 gun that was intended to be used on Morgårdshammar’s design. Photo: Sector.sk

The design work was mostly finished by 1930 and Morgårdshammar submitted a second offer on 5 May. Besides the project’s progress, what was most remarkable about this second offer was that Morgårdshammar now demanded SEK 60,000 (USD 168,000 in 2020 value), lowered from the previous offer of SEK 70,000 (USD 196,000 in 2020 value). The latter price was the maximum figure which could be provided for the construction of a prototype. It was also stated that if the tank was not accepted for service, Morgårdshammar wanted no compensation whatsoever. The Artillery Department’s construction department had also been continuously informed by Burén on the progress of the tank program.

Despite these factors, the Artillery Department refused the offer on the grounds that they could not accept such a generous offer as it would mean that Morgårdshammar would lose money. An additional issue was the fact that the Artillery Department required a prototype to review before accepting the new tank type. Morgårdshammar’s lack of experience in the field of tank design and production also caused some issues. Morgårdshammar’s head engineer Bjarme responded to this by stating that delivering functioning constructions based solely on drawings was nothing new to Morgårdshammar and, as such, did not see the construction department’s reasoning to be justified.

Drawing of the 47 mm gun intended for the Morgårdshammar tank. Photo: Krigsarkivet, special thanks to Karl Blomster for providing the photograph.

Competition

By 1930, two other Swedish companies had shown interest in providing the Swedish Army with a new tank. A meeting was held within the Artillery Department and it was concluded that no foreign tank types suitable for Swedish conditions were available for sale and that a total of three companies within Sweden could provide the Army with a new tank.

These were Morgårdshammars Mekaniska Verkstad AB, AB Landsverk, and AB Bofors. Unlike Morgårdshammar, however, Bofors and Landsverk both relied on German companies for design work as well as prototyping. These companies were Krupp AG and Maschinenfabrik Esslingen, respectively. Landsverk offered a tank based on the Räder-Raupen-Kampfwagen M28 designed by Maschinenfabrik Esslingen, known as the L-5, while the design offered by Bofors was in reality the Krupp Leichttraktor.

Draft of turret design referred to as U.3, most likely related to the A.2 variation of Proposal A. Photo: Krigsarkivet, special thanks to Karl Blomster for providing the photograph.

The correspondence between Major Burén and Major Heigl continued into 1930, but Heigl’s sickness persisted. Heigl’s efforts would continue until the last stages of his life and the message of his passing would come from the Swedish embassy in Vienna together with Heigl’s latest progress on the project in December 1930.

When Bertil Burén later presented his views to the General field equipment master regarding the construction department’s decision regarding Morgårdshammar’s offer, he assured Burén that things would have been different had Heigl still been alive.

In a final consideration in February 1931 by the Artillery Department, it was concluded that the Morgårdshammar design possessed significant potential as a tank well suited to Swedish conditions. However, the fact that Morgårdshammar was unable to present a prototype, unlike its competitors, meant that it was expected that a relatively long time would pass before this type of tank could be accepted for service. This did not align with the need to replace the existing fleet of vehicles within the near future. The untimely death of Major Fritz Heigl was also noted as an obstacle in realizing the project.

On the other hand, in light of the unselfish efforts made by Morgårdshammar as well as potential future developments, it was made clear that there was potential for financial support for the establishment of Morgårdshammar as a tank industry. As part of future tank acquisition for wartime needs, it was seen as important that the experience within the field of tank development gathered by Morgårdshammar could be put to use.

Designs & offers

Fritz Heigl was able to present two different main designs to Morgårdshammar after input from Bertil Burén. The first construction was a fully tracked design known as Proposal A, while the second used a radical wheel system and was known as Proposal B. This design process would eventually culminate in the A-4-C as an evolution of Proposal A. It should be noted that Heigl’s designs did not directly correlate with the specifications of the offers put forward by Morgårdshammar to the Artillery Department. Only offers based on the more conventional purely tracked Proposal A were made to the Artillery Department under the designation “Stridsvagn, system Heigl”.

Proposal A

Heigl’s Proposal A was a mostly conventional tank design for its day, originally presented in mid-April 1928 after various layouts had been considered. These layouts were designated Sv. M A1, Sv. M A2, and Sv. M A3, respectively, the latter designation being an assumption based on the established pattern. In the designation “Sv. M A1”, “Sv.” refers to the early Swedish acronym for tank, “M” refers to Morgårdshammar, and “A1” refers to iteration 1 of Proposal A. Alternatively, these variations were simply referred to as A.1 through A.3. The A.1 is similar to the A-4-C design which would be finalized later. The vehicle described below is the finalized design of the A.2 which was in line with the appearance of Proposal A as presented in 1928. Finally, a third alternative known as A.3 with a rear-mounted engine is also mentioned in the documentation, but nothing more than its engine configuration is described.

Drawing of Proposal A dated 1928. Photo: Warspot.ru via Krigsarkivet

Proposal A had a length of 5.3 m, a width of 2.1 m, and a height of 2.4 m. Ground clearance was 500 mm and its tracks had a width of 350 mm. One of its more unusual features was in terms of the layout of its upper track run which was placed at an angle sloping downwards towards the front. It rode on 12 road wheels suspended by vertical actuators with the forward most roadwheel on either side being equipped with shock absorbers. The track was supported by four return rollers, while the drive sprocket was placed at the rear of the vehicle. This sprocket was powered by a rear transmission offset to the left which was connected to the engine mounted at the front left of the tank via a diagonal drive shaft. This suspension was in turn mostly under armor, as was the fashion at the time.

The vehicle carried a four-man crew, consisting of a forward driver, a reverse driver, a gunner, and a commander. Both drivers were positioned in extensions from the superstructure, the forward driver being located to the front right while the reverse driver was positioned to the rear left. Either extension was equipped with three vision devices while the forward face of either extension acted as a hatch hinged upwards, permitting for unobstructed observation when judged suitable. The rear driver’s position was covered by what is interpreted from drawings as a large hatch hinged away from him for easier access. The superstructure itself also housed a vision device to its front and a single air-cooled machine gun suspended in a ball mount to the front left.

Drafts of the interior arrangement of the A.2, the design which would be finalized as Proposal A in 1928, Photo: Krigsarkivet, special thanks to Karl Blomster for providing the photograph.

Atop the superstructure, the main turret was placed. It housed the tank’s primary armament in the form of a Bofors 47 mm cannon offset to the left with a shoulder rest which was mounted in a ball mount. This enabled it to be aimed in traverse and elevation independently of the main turret. The gunner was seated to the left of the primary armament, underneath a hatch in the roof. A second machine gun capable of being elevated to a vertical position was placed in the rear of the main turret, intended to be able to be used in an anti-aircraft role. The commander was seated higher than the gunner in a smaller sub-turret located in an extension on the right side of the main turret. This sub-turret also mounted a third air-cooled machine gun and a mushroom-type vision cupola on top.

Proposal B

The second design pursued by Heigl was far more radical, however, being presented in April 1928 after Proposal A. In some documentation, it is referred to as the Sv. M. 28 syst Heigl (Tank Morgårdshammar 1928 system Heigl). Unlike Proposal A, it was never seriously considered or offered to the Artillery Department. It featured a unique wheel-cum-track design consisting of a conventional track system in addition to two sets of railroad wheels at the front and rear respectively, which could be elevated or lowered as required. This design was never seriously considered for sale by Morgårdshammar.

Drawing of Proposal B dated 1928. Photo: Ointres.se

This was a response to a widespread concern at the time regarding the reliability and range of tracked systems. By introducing an alternate transport mode for travel outside of combat, usually done in the form of a wheel-cum-track design where the vehicle could transition between running on tracks or wheels for road travel, these concerns were mitigated. What made Proposal B stand out was the fact that its wheels were not intended for road travel, but for railroad use, something which makes sense from the perspective of strategic mobility. This could theoretically also allow the vehicle to act as an armored draisine if required, allowing it to protect the vital railroad-based ore routes of northern Sweden. This is a solution that was pursued in various forms by German, Japanese, Polish, and Soviet engineers, even after the Second World War. These railroad routes were of vital importance to the Swedish economy and extensive effort was put into defending them ever since they were constructed in the early 1900s. As such, Heigl’s radical approach did make sense in the context of Swedish strategic concerns. While the primary function of the convertible drive was to enable travel along railroad lines, they could be used to help cross trenches, overcome obstacles, or climb mounds.

This convertible system consisted of four railroad wheels mounted in two pairs on the front and rear of the vehicle. The railroad wheels were mounted at the end of folding arms actuated by pistons. A piston was mounted at either corner of the vehicle with a shallow upward angle facing outwards from the center between the track and hull. These arms could then be elevated or depressed between a stowed mode where they are nearly vertical or a travel mode where they extend down to allow the bottom of either railroad wheel to be at a level below the bottom track run.

Besides the wheel-cum-track system, the design was overall similar to Proposal A, but was different in specific areas. It was longer at 6.8 m, but not as wide at 1.95 m or as tall at 2.32 m. The track system was more conventional, having a slight slope upwards towards the front. It rode on 10 road wheels and the track return was supported by three return rollers. The engine was located at the rear instead of at the front, connected to a rear-mounted transmission which provided power to the rear-drive sprocket. This was still covered by armor panels alongside the rest of the suspension.

The design for Proposal B carried a crew of three, consisting of a centrally situated driver with a gunner and a commander behind him in the turret. The driver sat in the forward part of the superstructure which was octagonal in shape with the rear face being extended back to form part of the engine compartment. The armor layout included many angles and the turret had a round shape, meaning that ballistic protection could be increased alongside the increased likelihood of ricochets.

Cutaway exposing the interior layout of Proposal B. Photo: Krigsarkivet, special thanks to Karl Blomster for providing the photograph.

The forward-most face of the superstructure had a vision device and was hinged at its top to allow it to be folded away when not required by the driver. The faces to either forward corner as well as either side also housed vision devices. This superstructure had a total of four ball mounts for machine guns, one in either corner face. The roof of the superstructure just behind the turret housed a horizontally mounted access hatch that was hinged to the rear. Driving controls consisted of two steering wheels, one mounted in the front to be used by the driver, and another in the rear of the fighting compartment. The driver also seems to have had access to driving tillers. The rear steering wheel was likely intended to be operated by one of the crew members in the turret to reverse the vehicle after opening the hatch in the rear of the turret. This was a two-piece hatch and was located adjacent to the horizontal hatch behind the turret, enabling easier access when the turret is traversed to the front by opening both hatches.

The turret was located centrally atop the octagonal part of the superstructure. In addition to the rear hatch, it housed a mushroom-type vision cupola on its rear right with six vision ports. The turret housed the primary armament which was of the same type and mounting as seen on Proposal A. It also housed three additional machine gun ball mounts, one of which was mounted parallel to the primary armament. Secondary armament consisted of three air-cooled machine guns which could be moved between the different ball mounts in the tank as required.

Stridsvagn A-4-C syst. Heigl

The ultimate evolution of Fritz Heigl’s work would be the Stridsvagn A-4-C syst. Heigl (Tank A-4-C system Heigl), presented in 1930. This design would be the furthest development of Proposal A. This iteration was in line with the previously mentioned A.1 variation of Proposal A, having a more conventional layout. Compared to the A.2, the dedicated rear driving position was missing and the track layout was more conventional, being raised to the front rather than the rear. Through this, the total length of the tank had been reduced to 5 m.

Drawing of the A-4-C from 1930. Photo: Fromtheswedisharchives.wordpress.com

The A-4-C’s suspension consisted of 10 road wheels while three return rollers supported the track’s run above. The engine was retained at the front left while the drive sprocket and transmission were mounted to the rear. This transmission was, at least in early drafts, moved to the center rear of the vehicle, being connected to the engine via a diagonal drive shaft. The forward return roller was connected to the external track adjustment mechanism. This mechanism was integrated into the armored cover for the suspension which covered nearly all of the suspension units.

Drawing depicting the running gear of the A-4-C with and without side skirts. Photo: Krigsarkivet, special thanks to Karl Blomster for providing the photograph.

The driver was seated on a bicycle-type seat to the front right of the vehicle. He was provided with a small extrusion at the front, with a hinged hatch to the front and a vision slit to the left likely replicated on the right. In terms of turret design, the A-4-C remained rather unconventional. The primary turret was a conical design and housed at least two crew members. The primary armament was housed at the front in a circular mounting, likely a ball mount, while an air-cooled machine gun in a ball mount was located at its rear. A second ball mount was placed on the forward left side of the turret with a vision slit placed ahead of it, the latter being part of a hatch that could be opened upwards to provide increased situational awareness. These features were likely replicated on the far side of the turret.


Side view draft depicting the interior of the A.1 iteration of Proposal A. Photo: Krigsarkivet, special thanks to Karl Blomster for providing the photograph.

A secondary turret was mounted to the rear left on top of the primary turret on a round extrusion. This turret was provided with another machine gun in a ball mount to its front, while a hatch with a vision slit was located on the forward left side of it, likely complemented by a corresponding device on the opposite side. At its very top, the secondary turret housed a cupola hinged to the rear. This seemingly lacked vision devices but could provide the commander with good visibility in an open position.


Top view draft depicting the interior of the A.1 iteration of Proposal A. Photo: Krigsarkivet, special thanks to Karl Blomster for providing the photograph.

1929 offer

By the time a fully tracked design was offered to the Artillery Department by Morgårdshammar in October 1929, it had gone through some changes compared to Proposal A as drawn in 1928. Certain features such as the transmission, gearbox, and clutch were still not decided upon at this point. This design was referred to simply as “Stridsvagn, system Heigl” (Tank, system Heigl).

The offered design was taller, with ground clearance increased to 600 mm and total height to 2.75 m. Weight was specified as 10.5 tonnes without armament, ammunition or crew, giving it an average ground pressure of around 0.5 kg per cm2. Combat ready, this would increase to the maximum limit of 12 tonnes as specified in the requirements provided by Major Burén. Armament had increased to four machine guns in addition to a low caliber cannon while armor protection had been decided at 20 to 30 mm, making it well protected for its day, so much so that it could be considered shell proof.

Steering was of the clutch-brake type and it was suggested that two driving positions could be made available, at the front and rear respectively. The additional driver facing the opposite direction to the tank’s heading would be tasked with aiding in combat while not steering. This was implemented in order to enable equivalent maneuverability and combat effectiveness both forwards and backward. The steering devices were power-assisted by compressed air, being linked to a compressor connected to the engine. The suspension consisted of spiral springs and hydraulic shock absorbers. The offered design could overcome a gradient of 45°, a trench of 2.3 m, a wall of 1 m, and wade through 1 m of water. Top speed was rated at 25 km/h, a speed which could be attained while heading both forwards and in reverse, with four gears being available in either direction.

The specified engine was a water-cooled 6-cylinder 6.4-liter Scania-Vabis gasoline model with a maximum power output of 85 hp at 2000 rpm. It would also be able to run on ethanol. The choice of this engine instead of the previously mentioned Maybach alternative was due to the advantages presented by an indigenously produced engine. This construction could operate at up to 40° from the horizontal and was accessible from the driver’s position, most likely at the front. Fuel consumption was specified at circa 225 grams per horsepower at full power and circa 260 grams per horsepower at half power.

1930 offer

The second offer was made by Morgårdshammar in May 1930 and consisted of a more finalized tank design. Height was reduced back to 2.4 m as on Proposal A from 1928 and ground clearance was reduced to 400 mm at its lowest while being greater at the front and rear in order to ease the crossing of snowy terrain. Track width had been reduced to 320 mm while machine gun armament had been reduced to two. Armor thickness had been further specified as 30 mm across the most vital areas, with remaining surfaces being covered by 10 to 20 mm thick plates. The crew was no longer specified as four, but was instead noted as consisting of either three or four men. In terms of provisions for steering, besides the two driver positions already suggested, it was proposed that the tank could also be steered from the turret where better visibility would be available.

The engine choice had returned to a Maybach design. Specifically, a water-cooled 6-cylinder 7-liter Maybach gasoline engine with a maximum power output of 100 hp at 2200 rpm. This design was originally intended as a bus engine but modified to serve in a tank. The reason for this choice was to increase the engine power sufficiently to enable the tank to reliably move at a speed of 20 km/h under most conditions, with 25 km/h remaining as the top speed. The offer states that a larger engine would have been desirable, but that this was not possible due to weight and volume limitations.

The choice of gearbox fell on a double planetary type based on Heigl’s design, a system that the manufacturer had experience with. The offer also included an overdrive which doubled the number of available gears compared to the ordinary. It was added that if this gearbox was not found to be satisfactory, Morgårdshammar would be willing to replace it with a mechanical gearbox without additional costs. In the event that a mechanical gearbox was to be used, either due to practical reasons or by request, speedometers would be built into the axles to enable the driver to seamlessly time the rotation of cogs and axles when switching gears.

Drawing depicting the function of Proposal B’s innovative wheel-cum-track design. Photo: Warspot.ru via Krigsarkivet

Conclusion

In the end, Morgårdshammar’s offer would fail and AB Landsverk, operating as a German subsidiary, was able to go ahead with their L-5 design which would evolve into the more well-known L-10 and L-30. This laid the groundwork for the establishment of Swedish tank development and industry in the long term, but one initially under the influence of German interests, for good and bad. Morgårdshammar meanwhile would never come to function as a part of the Swedish tank industry. Despite their significant effort and initiative, their experimentation in this field would come to a halt alongside their tank program when the company lost out to competition, something which was no doubt exacerbated by the death of the head designer for the project. Whether the initiative on their part was truly of patriotic origin or due interest in economic gains is however uncertain. Morgårdshmmar still exists as a company today, albeit as a subsidiary, and its focus remains on heavy mining equipment.

Morgårdshammar’s Proposal A from 1928.
Morgårdshammar’s Proposal B from 1928.
Morgårdshammar’s later A-4-C proposal from 1930. All illustrations by Pavel Carpaticus Alexe, funded by our Patreon campaign.

Sources

Militära Minnen 1895-1943. Bertil Burén. Södermanlands Regementes Museiförening, 2005. p.88-94.
Teknisk Tidskrift, 31 October 1931, Svenska Teknologföreningen.
Krigsarkivet, Svea livgarde, Mobiliseringsavdelningen, fd Hemliga handlingar, F 2: 1.
Krigsarkivet, Göta livgarde, Stridsvagnsbataljonen, F. Särskilda serier.
Krigsarkivet, Göta livgarde, Stridsvagnsbataljonen, offer from Morgårdshammar October 15 1929 and May 5 1930.
Krigsarkivet, Bertil Burén’s personal archive, letters to Fritz Heigl.
Krigsarkivet, Generalmajor Eric Gillners Samling.
PANSAR Nummer 2 2014, Christer Badstöe.
PANSAR Nummer 2 1982, Didrik von Porat.
http://www.ointres.se/strv_m_21.htm
http://www.biographien.ac.at/oebl/oebl_H/Heigl_Fritz_1895_1930.xml
http://tankarchives.blogspot.com/2017/11/the-swedish-armys-tough-choice.html

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Landsverk 120 (L-120) in Norwegian Service ‘Rikstanken’

Kingdom of Sweden/Kingdom of Norway (1938)
Light Tank – 1 Operated

Even into the 1930s, Norway was not one of the more industrially advanced countries in Europe. As such, Norway was a relative latecomer to the idea of mechanizing its armed forces. It was not until the mid-1930s that the Royal Norwegian Army (No: Hæren) began to express an interest in Armored Fighting Vehicles. It was around this time that it developed its first armored vehicles – 3 improvised armored cars built on commercial truck chassis. By 1936 though, the Army was looking for something a little tougher. The Army became interested in the L-120, a prototype light tank in development by its fellow Scandinavian neighbor, Sweden. While the L-120 – built by Landsverk – would not become a success in Sweden, 1 prototype hull was purchased by and delivered to the Norwegians.

The tank was delivered without a turret, leaving the Hæren to build a basic one of its own design, equipped with a machine gun. The L-120 was Norway’s first-ever tank and would be known by many names, including ‘Kongstanken’ (Royal Tank) and ‘Norgestanken’, (Norwegian Tank); however, it is most popularly known as the ‘Rikstanken’ (The National Tank).

In Norwegian service, the tank would never see combat. Although it was used in training in 1938 and 1939, it was left in storage when the German Army invaded in April 1940. After the invasion and subsequent occupation, the vehicle remained in storage. By war’s end, however, the tank had disappeared.

The L-120 ‘Rikstanken’. This photo is quite rare in that it is one of the only photos showing the machine gun installed in the turret. Photo: Wikimedia commons

What’s in a Name?

According to the Forsvarsmuseet (Norwegian Armed Forces Museum) in Oslo, the names given to the L-120 have some interesting history in their own right. The names ‘Norgestanken’ and ‘Kongstanken’ were actually double entendres. In Norwegian, the word ‘tanken’ means both “the tank” and “the thought”. The noun ‘Norgestanken‘ can therefore also mean ‘The Norway thought’, an old nationalistic term for the idea of an independent Norway – Norway had only gained independence from Sweden in 1905. ‘Kongstanken’ can also mean “the royal thought”, and can signify grand, bold, or idealistic thinking. This generation of Norwegians remembered the struggle for independence, so it is easy to see why so much reverence was placed in the name.

In 1936, the Swedish Military was looking to replace the Stridsvagn m/21-29 and Stridsvagn m/31. A requirement was put out for two new tanks, one armed with a 37 mm gun, and a lighter vehicle armed only with machine guns. Landsverk would design two vehicles to fill these roles, the L-60 and the L-120. The L-60 would fill the medium tank role, and would later enter service as the Strv m/38. The L-120 was under consideration for the role of the light tank. At least 3 prototypes were built, each with slight differences, mostly regarding the design of the radiator grills and the design of the driver’s hatch. Design-wise, the L-120 was extremely similar to the previous L-100 light tank concept. The design was typically Swedish, being quite a narrow vehicle, with a hull that sloped to the rear, and a large diameter sprocket wheel at the front of the running gear. The L-120 has a claim to fame in that it is one of the first-ever tanks to feature a torsion bar suspension.


One of the L-120 prototypes complete with a machine gun-armed turret. It has some differences compared to the Norwegian example, in particular the vent on the hull side and the design of the driver’s hatch. Photo: landskrona

By 1937, two prototypes had been produced, and by May were taking part in trials. The trials highlighted that their engines left them underpowered, and they were extremely unreliable. As a result, the Swedes canceled development of the L-120, with the military instead opting for the Czechoslovakian-built AH-IV tankette.

Norwegian Purchase

Despite the tank’s failures in the eyes of the Swedish military, the Norwegians expressed interest in the L-120 to see whether it would be compatible with their dragoon and cavalry units. Initially, the Norwegian Army was granted a budget of 20,000 Kroner. However, the shipping costs of a complete tank would have risen to 50,000 Kroner due to the weight. As a result, the vehicle was shipped in a stripped-down condition without armor plating, a turret, or any armament. The Norwegian Army took delivery of this basic tank hull in 1938.


The L-120 that would make it to Norway. Note the differences to the vehicle pictured above. The date and location are unknown, but as the turret is different to that used on the example sent to Norway, this may well be the prototype under trials in Sweden. Photo: Wikimedia Commons

Overview of the ‘Rikstanken’

Unfortunately, not much information regarding this L-120’s unique specifications survive today, but there are fragments that can be retrieved. The L-120 weighed between 4 and 4.5 tonnes (4.4 – 4.9 tons), measured 4 meters (13 ft 3 in) in length and was about 1.7 meters (5 ft 8 in) wide. With the original turret, it measured 1.65 meters (5 ft 4 in) in height. Propulsion was provided by an 85 hp, 6 cylinder Volvo Type DC – presumably, petrol – engine, reportedly taken from the Volvo LV93 series of commercial trucks. This ran through a 5 speed (4 forwards, 1 reverse) gearbox, also apparently taken from the LV93 truck. The engine was located at the rear of the tank and powered the forward-mounted sprocket wheels, propelling the vehicle to a top speed of about 50 km/h (31 mph). The running gear consisted of 4 split, spoked, and rubber-tired road wheels per side on a torsion bar suspension. There was a larger diameter, spoked trailing idler wheel at the rear, and the return of the track was supported by two return rollers. The track was of quite a short pitch, and quite narrow at about 15 cm (5.9 in) wide.

This photo of one of the L-120 prototypes during trials grants a clear view of the vehicle’s running gear. This is not the example sent to Norway and is one of the other two vehicles, identified by the large grill on the hull side. Photo: ftr.wot-news.com

The L-120 hull that made it to Norway was unique in appearance compared to the other prototypes. The front of the vehicle was dominated by a large sloping upper plate that extended back to the turret ring. There is a suggestion that the tank was delivered without armor, and as such, iron plates were installed on the vehicle. This cannot be corroborated at the time of writing, however. The sides of the hull also sloped inwards. A simple box-like hood was added over the driver’s position, placed slightly to the left of the centerline. Three simple vision ports in the hood provided vision for the driver, one of only a two-man crew. The steering tillers were also reportedly missing when the vehicle arrived, leading to their replacement with a steering wheel. This is another detail that currently can not be corroborated.

The other crew member was the commander/gunner who would be located in the turret. As the vehicle arrived without a turret, the Norwegians had to fabricate their own. They came up with a simple cylindrical turret with a flat roof and a single-piece hatch. This seems to be quite crude in nature and simply hinges backward at a crease in the middle of the roof plate. The only way the commander could see out effectively would be to operate head out, as there do not appear to have been any vision devices in the walls or roof of the turret. However, in some of the surviving photos, it would appear that there may be simple slits cut into the sides of the turret. Considering the rudimentary nature of the turret, it must be assumed that horizontal traverse was manual, but whether this was by gearing or brute force is unknown. It is also unknown how thick the metal used to fabricate the turret was, and whether it made it taller or shorter than the original turret.

A post-invasion photo of the ‘Rikstanken’ with a posing German soldier. Note the sloping upper plate, square hood for the driver and the round aperture in the turret ‘face’ for the machine gun main armament. Photo: armed-conflicts.com

For armament, the Norwegians installed an American made Colt M/29 ‘Mitraljøse’ (heavy machine gun) in a simple circular cut out in the ‘face’ of the turret. This weapon was a Norway-specific version of the Colt MG38, the export version of the Colt M1928, which in turn was an export version of the famous Browning M1917. It was chambered in the Norwegian 7.92 x 61 mm round, and remained a water-cooled, recoil-operated machine gun, and had a rate-of-fire of 590 rounds-per-minute. This gun was a sensible choice, as it was the most plentiful – perhaps only – heavy weapon in service with the Norwegian Army at this time, with around 1,800 in operation.

Norwegian troops operating an M/29 at Narvik in 1940. It should be noted that this is a reversed image as the M/29 feeds from the left, not the right. Photo: Wikimedia Commons

Other details on the vehicle include simple headlights on the fenders over the sprocket wheels, the exhaust pipe on the right rear fender, a larger stowage box on the left rear fender, and pioneer tools (pickaxes, shovels, etc) stowed around the back end of the vehicle.

Service

The service history of the ‘Rikstanken’ can be described as patchy at best. What remains are a series of fragments, mostly consisting of second- or even third-hand accounts.

Between 1938 and 1939, the L-120 was predominantly used in training exercises alongside the cavalry and the 3 improvised armored cars. All 4 vehicles were passed around the cavalry and dragoon units so they could all train with and gain experience operating with armor. As part of the cavalry, the tank received the number ‘PV-1’, which was painted on both of the fenders over the sprocket wheels. It would appear that the tank was predominantly based at Gardermoen, just North of Oslo, at the base of the 1st Dragoon Regiment.

Two shots of the L-120 with – what appears to be – Norwegian troops. On the left we can see the tank, possibly at Gardermoen, between 1938 and 1939. Note the ‘PV-1’ stenciled onto the fender. On the right, we can see the tank in a poor state, buried in snow, with the rear plate missing. Note the exposed engine. Photo: armedconflicts.com

It would appear that the mechanical issues that emerged during the Swedish trials once more reared their heads during Norway’s time operating the vehicle. The Norwegians also came to the conclusion that the engine was far too underpowered. There were also brake issues, once reportedly causing the vehicle to crash into a tree. A Colonel by the name of Christopher Fougner – Commander of the 2nd Dragoon Regiment, was of the opinion that the tank was a waste of money and time, reportedly stating that the only working tank the Norwegian Army would ever see would belong to an attacking enemy. This is ironic considering the events that would transpire just a couple of years later, in 1940.

April 1940 would, of course, bring the invasion of Norway by Nazi Germany, and subsequent occupation. The L-120’s role in the invasion is, again, uncertain. There is a possibility that the tank did see some action in defense of Norway, but it would appear this was not the case. Even so, its ability to combat the more advanced Panzers of the Wehrmacht is highly questionable, although it may have done well against infantry. However, it seems more likely that the tank – along with the armored cars – were left at the Gardermoen base when the garrison forces left to face the invaders. Indeed, there are many post-invasion photos of German troops posing with the vehicle to suggest this.

The ‘Rikstanken’ onboard a ship. Quite why it is on a ship, where it is going, or why, is unknown. Note the large stowage box and pickaxe at the rear. Photo: armedconflicts.com

This, unfortunately, is where the trail runs cold. It is unknown what happened to the vehicle during the duration of the occupation, or whether it survived to the end of the war. Nothing is thought to remain of the vehicle today.

Conclusion

Successful or not, the L-120 ‘Rikstanken’ is an important vehicle in Norway’s military history. Despite the mechanical issues, it gave the Norwegian Army their first experience in the operation of a tank.

The ‘Rikstanken’ in a rather poor state with posing German soldiers. Photo: armedconflicts.com

It was not until the end of the War, and the Nazi occupation, that the Norwegian Army would gain more advanced armored vehicles. The surrendering German Army left behind swathes of equipment, including Panzer III medium tanks and StuG III assault guns, which would be pressed into service as the Stridsvogn and Stormkanon KW-III, respectively. Norway would also receive a small number of the American built M24 Chaffee light tank, which would serve them into the later years of the Cold War.


Landsverk 120 (L-120). In Norwegian service, it was known as the ‘Rikstanken’ meaning ‘National Tank’. It was fitted with an improvised turret mounting an M/29 machine gun. The grey color is speculative as it is unknown what color the vehicle would have been. This illustration was produced by Ardhya Anargha, funded by our Patreon campaign.

Sources

Ole Jacob Broch, Oslo militære samfund gjennom 25 år: 1925-50
Åke F. Jensen, Kavaleriet i Norge 1200-1994: Utvikling og innsats gjennom 800 år
Tom Kristiansen, Tysk trussel mot Norge? Forsvarsledelse, trusselvurderinger og militære tiltak før 1940
Øystein Mølmen, Raumabanen/Romsdalen, Lesja og Dovre: Kamphandlingene 1 April 1940 Kjell Arnljot Wig, Kongen ser tilbake
Forsvarsmuseet (Norwegian Armed Forces Museum), Oslo
www.armedconflicts.com
www2.landskrona.se (Accessed via the Wayback machine)
hem.fyristorg.com (Accessed via the Wayback machine)
www.dws-xip.pl

Categories
WW2 German Light Prototypes WW2 Swedish Prototypes

Räder-Raupen-Kampfwagen M28 (Landsverk 5)

German Reich/Kingdom of Sweden (1928-1933)
Light Tank – 6 Prototypes Built

The Räder-Raupen-Kampfwagen M28 (Eng: Wheel-Cum-Track Tank M28), also known as the Landsverk 5, was one of the first German tank projects after World War I. According to paragraph 171 of the Treaty of Versailles from 1919, the German Army and German companies were forbidden to develop tanks. However, nine years after the treaty was signed, the development of the M28 started in high secrecy. Five or six of these vehicles were built in various configurations and examined by both the German and Swedish Armies, but did not enter service with either of them.

Background

On 3 April 1926, graduate engineer (Dipl.-Ing.) Otto Merker, then working at the Schwäbische Hüttenwerke, part of the company Gutehoffnungshütte (GHH), filed a patent in France concerning designs of wheel-cum-track tractors. During the two following years, he would improve and refine his designs until 1928, when the wheel-cum-track vehicle (the Räder-Raupen Fahrzeug) was ready to be produced. It was designed to act as the basis for a tank intended to be produced by the subsidiary AB Landsverk in Landskrona, Sweden.

Two designs for a wheel-cum-track tractor, patented by Otto Merker in April 1926. Source: Brevet d’invention No. 631.839.

The full name of GHH was Gutehoffnungshütte, Aktienverein für Bergbau und Hüttenbetrieb (Eng: Joint Stock Association for Mining and Metallurgical Business), based in the city of Oberhausen (North Rhine-Westphalia, Germany) with a specialization in mechanical engineering. Landsverk, then known as Landskrona Nya Mekaniska Verkstads Aktiebolag (Landskrona New Mechanical Works Joint Stock Company), had originally been a foundry focusing on various civilian applications of metal works. By 1920, the company was on the brink of bankruptcy. Seeing an opportunity, GHH bailed them out and gained 50% of the company’s stocks in the process.

After 1920, GHH managed to acquire more stocks and owned 62.8% of Landsverk in 1925. These stocks were registered by another subsidiary, N.V. en Handelsmaatschappij Rollo, a Dutch company acquired by GHH in 1920. A Swedish law from 1916 prohibited foreigners from owning more than 20 percent of a company, but the Landsverk articles of association were based on an 1895 contract.

These factors allowed GHH, who also owned the majority of MAN AG at the time, to circumvent the limitations on tank development in Germany set by the Treaty of Versailles through setting up armored vehicle development in Sweden. This use of subsidiaries and foreign companies to circumvent the treaty, as well as the cooperation with the USSR, was already suspected by the Royal Swedish Army Materiel Administration’s artillery department in the early 1930s.

Name

The Räder-Raupen-Kampfwagen M28, meaning ‘Wheels-Tracks-Fighting vehicle Model 1928’, is sometimes also referred to as ‘GHH-Fahrzeug GKF’. In Sweden and within Landsverk, it was known as the ‘Landsverk 5’, or L-5 for short. The idea of a wheel-cum-track system already emerged in Germany during the early 1920’s when Joseph Vollmer developed a system based on a Hanomag tractor, utilized by the Czechoslovak-built Kolohousenka. Merker could have been inspired by Vollmer’s system, although it is also possible that he was influenced by the British, who had started testing wheel-cum-track systems mounted on various vehicles around the same time.

Chassis equipped with the 77 hp engine and hydraulic wheel system. Note the presence of rear fenders and headlights. Photo: alternathistory.com

Swedish Tank Acquisition

In December 1928, Swedish authorities officially established requirements for a future tank:

  • Maximum weight of 12 tonnes
  • Armor to stop 37 mm cannon fire
  • Armament consisting of both a cannon and a machine gun
  • Good mobility in Swedish terrain, an average speed of 20 km/h on road and half that in relatively difficult terrain

By this point, Sweden’s entire tank force consisted of just ten strv fm/21s (alternatively known as strv m/21s), and a small number of foreign vehicles acquired for trials. Furthermore, military spending had been drastically reduced as a result of the defense resolution of 1925. For these reasons, acquiring the largest number of vehicles possible with available assets within a relatively short time frame was stressed. The Swedish government had previously granted SEK 400,000 for this purpose.

Based on international trips to tank factories and trials of foreign designs, it was realized that no foreign tank available on the open market was suitable for Swedish circumstances at the time. Moreover, indigenous tank production was seen as a major advantage in terms of readiness for a potential military conflict. As such, Sweden turned to its own industry. In 1930, there were three companies within Sweden that could provide the military with a new tank. These were Morgårdshammars Mekaniska Verkstad AB (Morgårdshammar’s Mechanical Works Joint stock company), AB Landsverk, and AB Bofors.

The first of these, Morgårdshammars Mekaniska Verkstad, could provide an indigenous design which had been in development since 1927. This development was headed by the Austrian Major and tank theorist Fritz Heigl, famed for his publication ‘Taschenbuch der Tanks’ (Eng: ‘Handbook of Tanks’). Bofors and Landsverk, on the other hand, relied on German companies for design work. These companies were Krupp AG and Maschinenfabrik Esslingen respectively. Both Landsverk and Maschinenfabrik Esslingen were subsidiaries of GHH at the time. Krupp was, via two decoy companies, the largest stockholder of Bofors and these arms manufacturers actively cooperated in the development of various projects during the interwar years. In the case of the Bofors proposal, the tank in question was actually Krupp’s Leichttraktor design. This was an evolution of the LK II which was in service with the Swedish Army as the lightly modified strv fm/21. The Leichttraktor was interestingly equipped with a turret produced by Landsverk, the competitor of Bofors and Krupp in this case.

One of the Bofors (Krupp Leichttraktor) prototypes as a monument – the fate of a vehicle without a future. Photo: Yuri Pasholok, via warspot.ru

Design

The design of the M28 was unconventional overall. The engine was mounted in the front left of the vehicle in a u-shaped frame. A cooler was placed in front of it. The driver sat directly to the right of the engine. In an elevated hatch, three visors were located. It could be folded open to the right side of the vehicle. The rolled homogeneous armor on the vehicle was of mixed construction, being both bolted and riveted. Its thickness is unknown, although it was most likely between 8 to 13 mm thick, as with the production models offered to Sweden. This would be adequate against small arms fire, but certainly not against cannon or anti-tank gunfire.

The vehicle could also be driven from the back by a second driver whose seat was located in the rear right. He was covered by an elevatable hatch, in which a machine gun was installed. Above the machine gun, three square-shaped visors were placed. On the left side of the back, an access door was installed.

The M28 which was sent to the secret Soviet-German Kama proving grounds for testing, the protrusion at the front left of the vehicle is an air intake. Photo: Landskrona minnesbanken

Engine

Either five or six vehicles, numbered 1-6, were built but differed a bit from one another. Whether the sixth vehicle actually existed or was even planned is uncertain due to contradicting sources (this is further detailed below). The first three prototypes, 1-3, were powered by a Benz-50-PS 4-cylinder gasoline engine and was fitted with a 70 l fuel tank. This engine had a displacement of 4160 cm3 and a compression ratio of 4.75. It consumed 14 kg of fuel and 0.4 kg of oil per hour at cruising speed. It had a maximum output of 52 hp at 1950 rpm.

The other three prototypes, 4-6, had a 70-PS-NAG-D7P 4-cylinder gasoline engine and an 85 l fuel tank installed. It had a displacement of 3620 cm3, a compression ratio of 5.5, fuel consumption of 18 kg per hour and oil consumption of 0,6 kg per hour at cruising speed. The maximum output was 77 hp at 3400 rpm. The gasoline was pumped into the carburetor by an electric IMCO-Autopuls-12-V-Pumpe (pomp). Besides the standard fuel tank, an additional reserve can with a volume of 30 l could be brought along.

A Typ K 45 gearbox produced by ZF Friedrichshafen AG was installed. This gearbox was equipped with a multiplication device, a so-called ‘Maybach Schnellgang’, which provided the vehicle with four forward and two reverse gears in total. Changing from forward to reverse gear took 4-5 seconds. Driving on wheels, the early vehicle could reach a speed of 46 km/h, but only 23 km/h on track. The cruising range was 180 km on wheels and 80 km on tracks.

From Wheel to Track and Vice Versa

Changing from wheels to tracks was performed by lifting devices on the sides of the tank. Vehicles 1-4 had an electric lifting system installed, together with four 12 Volt batteries, 5 and 6 had a hydraulic system installed. With these systems, the wheels could be lowered or lifted 36 cm, resulting in a ground clearance of 15 cm between the tracks and the ground. Total ground clearance between the hull and the ground in the tracked mode was 40 cm. For the later type with the revised lifting device, the transition from tracks to wheels or the opposite could be made in just 20 seconds.

Previous wheel-cum-track vehicles were generally designed in such a way that switching from wheels to tracks or the opposite took a considerable amount of time. By being able to perform this process in just a few seconds, and from within the vehicle, the wheeled mode could be employed not only in regions that were known to possess large amounts of good roads but instead anywhere suitable. The wheeled system could also function as a jack for the vehicle, something which could have been very practical for performing maintenance to the running gear or repairing a damaged track.

The wheel-cum-track system had the additional advantages of decreasing wear on the running gear while also lowering running costs by decreasing both maintenance work and fuel consumption. In addition to this, the increased speed and subsequent increased tactical, as well as operational mobility provided by the wheeled mode, was considered important in combat scenarios of the day as stalemates were sought to be avoided based on experience from the First World War. In addition to this, speed was considered to be more important in terms of protection than armor.

If the lifting system did not work, for example due to a technical failure, the wheels could also be manually lifted. When manually performed, lifting or lowering the wheels took four men around five minutes.

The presence of the wheeled system did, however, have its drawbacks in the form of increased overall width and weight, both of which would be troublesome in terrain, while also limiting hull width. In the case of the M28, the total width was 2.4 m but the distance between the outer edges of the tracks was only 1.6 m. This would limit the equipment and ammunition which could be carried. To partially address the width and weight issues, the wheeled units were designed in such a fashion that they could be removed in around six hours.

Front and rear photos of the M28 where the three rear vision blocks can be seen. Photo: zhuanlan.zhihu.com

Suspension

The wheels used cantilever springs. A cantilever spring is a flat spring supported at one end and holding a load at or near the other end. The suspension consisted of semi-elliptic leaf springs. Ten small road wheels were located on each side, gathered in two units of four and one unit of two. In order to reduce noise, some of the suspension components were covered by rubber and a type of coating from Ferodo, a British friction product manufacturer.

The metal tracks had a width of 20 cm, and a length of 12 cm. 66 track links were located on each side. The full weight of the vehicle was roughly 7 tonnes, which resulted in a ground pressure of 0.85 kg/cm2. The vehicle was maneuvered by a steering wheel via a special type of planetary transmission, a development of a Cletrac transmission. Rather than applying full braking force to the inner track during a turn, this transmission only reduces the power output to said track instead of completely cutting power. This resulted in the vehicle having a much smoother turning process than other vehicles of its day. A turn radius of 3 m within the inner track could be achieved using this system. If necessary, the inner track could be fully braked in order to perform tighter turns. The wheels were steered by a worm gear.

Braking while driving on the tracks was done with an outer-band brake, meaning that brake band is wrapped around the outside of a brake drum which will brake when tightened. While driving on wheels, an internal-band brake system was used, meaning that the drum is pressed on from the inside. The wheels were made of steel and equipped with pneumatic tires, although bulletproof tires seem to have been used as well. The wheelbase had a length of 2.8 m, while the complete chassis had a length of 4.38 m. On wheels, the chassis would reach a height of 1.48 m. As mentioned, the total width of the vehicle was 2.4 m, and the distance between the outer edges of the tracks was 1.6 m. The complete chassis of the early type without superstructure weighed 5.3 tonnes, the later type weighed 5.4 tonnes.

Turret

The commander and gunner were both seated in a centrally mounted turret. A six-sided cupola for the commander was installed on top with a visor in each side. This cupola could presumably be opened to the rear in order to provide increased visibility and access, just as on the mockup. Furthermore, two visors were placed facing upwards on top of the cupola. The commander and gunner could enter through a hatch in the back of the turret.

Armament

The primary armament of the M28 consisted of a 37 mm gun equipped with a semi-automatic breech. It had a depression of 10 degrees and an elevation of 30 degrees. To the left of the cannon, a coaxial 7.92 mm Dreyse machine gun was installed. It could be disconnected from the main gun which allowed for a depression of 15 degrees and an elevation of 35 degrees. Two optics were installed in the front of the turret, one for the main gun and one for the machine gun. An additional 7.92 mm Dreyse machine gun was installed in the rear driver’s hatch. This gun had a traverse of 20 degrees to each side, a depression of 5 degrees and an elevation of 77 degrees, potentially allowing it to be used as an anti-aircraft machine gun, although it is unclear if it was specifically designed for this purpose. The ammunition complement consisted of 200 37 mm shells and 2000 7.92 mm rounds in total. It should be noted that the primary armament seems to have never been installed, as all images depicting the front of the turret lack the 37 mm gun. The large protrusion at the front of the turret appears to be a shroud of some sort, presumably present to protect the gun from damage.

M28 with the rear driver’s hatch and machine gun at high elevation. Photo: valka.cz

Building and German Testing

A total of either five or six vehicles were built between 1929 and 1930 by Maschinenfabrik Esslingen. In order to retain secrecy, this production was labeled as farming equipment. A full-scale mockup was also constructed in affiliation with these vehicles. One of the early models with a complete armored body and turret was sent to Kama tank proving grounds in the USSR in 1930. The Kama proving grounds were located near Kazan. The name Kama was a combination of Kazan and Malbrandt, Malbrandt being chief engineer and responsible for the trials taking place at Kama. The proving grounds were a result of the Treaty of Rapallo, signed in 1922 between Germany and the then SFSR, which was not only intended to improve economic cooperation but military cooperation as well. The existence of these proving grounds was kept top secret as it did violate the Treaty of Versailles from 1919.

Designs like the WD Schlepper, Großtraktor, and Leichttraktor were tested at Kama, and so was the M28. During the tests, it became clear that it was underpowered and the suspension overloaded, which caused problems with the reliability of the systems, so the armored superstructure and turret were removed. After that, it performed reasonably well, but the Germans had lost their interest in this vehicle. When the collaboration between the USSR and German army ended in 1933, the vehicle was taken back to Germany and scrapped shortly after. What happened to the other vehicles is unknown, but it is highly unlikely that any chassis survived past the Second World War.

Demonstrations for Swedish Delegations

The first information regarding the M28 reached Swedish military authorities in the form of a confidential message to a lieutenant Elliot at the Royal Army Materiel Administration’s artillery department. It was reported that only a chassis had been produced so far. The fact that Germany was banned from tank production by the Versailles Treaty was well known. While the matter was subsequently shrouded in secrecy, captain Gösta Bratt, who was experienced with engines, was allowed to inspect and drive the tank in Germany.

The L-5 chassis, as it was referred to, was demonstrated to Swedish representatives on a number of occasions between 1930 and 1931. Demonstrations were primarily held with the later 77 hp engine and hydraulic system equipped chassis, without the hull and turret. Mobility was found to be more than sufficient and steering was easy to perform, even in sharp downward slopes. In the wheeled mode, a maximum speed of 80 km/h (49.7 mph) forward and 25 km/h (15.5 mph) backward could be attained. Additionally, upward slopes of around 40 degrees could be traversed without using full engine power. This was of course without the additional weight and instability brought by the armored body.

The running gear was generally liked, but the effectiveness of the semi-elliptic leaf spring suspension was not seen as sufficient, although improved suspension types were already being considered by this point. The construction of the wheeled units was regarded as being sufficiently robust for field use. Other features that were particularly acclaimed were the effective transmission, powerful engine, and silent running. The designer considered the advanced transmission, which allowed for reduced power output to the inner track during a turn, to be overly complex and that it would be advantageous to not include this feature in the production model. The Swedish delegation, on the other hand, viewed it as a significant advantage in Swedish terrain. While the pneumatic tires which were demonstrated were seen as suitable for peacetime conditions, their suitability for combat was doubted. For combat use, other types could replace the pneumatic tires. Semi-solid tires, which were offered by Landsverk for the production models, or bulletproof ones were considered for this purpose.

The previously mentioned issues with total and hull width respectively were however constant concerns. At the time, the maximum width of a tank suitable for Swedish terrain was considered to be 2 m, 0.4 m less than that of the displayed chassis. There was however consideration made on this point, namely that such a width would still be suitable for Swedish forests. A protecting framework could be fitted which would have protected the wheeled units, although this would not automatically increase mobility in dense terrain. Moreover, the 1.6 m distance between the outer edges of the tracks meant that stability could also become an issue in uneven terrain.

Another problem was the lack of armor protection in the opinion of Swedish officials, only 13 to 15 mm of frontal armor in the case of the projected designs. This could be addressed in the case of the fully tracked vehicle, as the weight saved by removing the wheeled units could be used to increase the frontal armor to 25 mm. Some statements doubted whether armor protection below 30 mm for the most vital areas was even acceptable and that the armor of the fully tracked variant should be improved without increasing the total weight of the vehicle beyond 9.5 tonnes.

Firepower was also criticized, despite meeting the original requirements, as only one weapon could generally be used to engage a target at a time. While the hull machine gun was an exception to this, as it would not be operated by the turret crew, it could only provide a limited arc of fire.

Despite these negative factors, the displays resulted in mostly positive reviews. The general performance of the tank was considered to meet and in some cases exceed the previously mentioned requirements and the vehicle was seen as a modern tank at the time.

Profile view of the M28 in its wheeled mode. Photo: valka.cz

Swedish Consideration

Landsverk’s offer to Swedish authorities actually differed from the L-5 in the state that it was demonstrated. Two variants were offered, both a wheel-cum-track design as well as a fully tracked model. These were known as BT.150 I and OT.150 I respectively. They differed from the original in a number of ways, among them, that they would use a rear-mounted 150 hp Maybach engine. A Scania-Vabis model was originally planned, but no suitable engine from this manufacturer was available. The vehicle would be around 0.5 m longer and some steering systems were to be altered. The tracks would be wider and the leading wheel would be placed higher up while the suspension system would be improved. Total weight of this projected type was 8.4-8.9 tonnes. Both of the offered designs moved the fourth crew member from the rear of the vehicle to the front, next to the driver. The fully tracked vehicle was intended to be equipped both with a hull mounted machine gun as well as radio equipment, whereas the wheel-cum-track design would feature either a hull machine gun or a radio. These projected characteristics generally align with what the development process resulted in, namely the L-10 and L-30 designs.

By 1931, the envisioned organization of a Swedish tank company consisted of 18 tanks, a number which Sweden did not possess. Moreover, what tank types were available, such as the strv m/21-29 (upgraded strv fm/21) and strv fm/28 (Renault NC27), were mostly obsolete by this point. Because of these factors, the tactical requirements and capabilities of modern tanks could not be properly assessed. This stressed the acquisition of a fully developed and modern vehicles within a short time frame.

As a result, only acquiring the fully tracked model was seen as an attractive option. Acquiring only this variant would have also allowed for a wider hull to be used while decreasing the overall width as the wheeled system would not be protruding beyond the sides of the hull. This would have increased stability as well as cross-country mobility while allowing for increased armor protection. The enhanced tactical and operational mobility provided by the wheel-cum-track design was however appreciated and purchasing one vehicle in this configuration would allow for extensive field trials and consideration to be performed with this type of vehicle. The potential to use the same vehicle model both as a fully tracked tank and as a vehicle with mixed propulsion was also seen as advantageous.

The increased speed but decreased protection of the wheel-cum-track design meant that a different tactical approach would be applied to the wheel-cum-track model. There were suggestions to use mixed units with fully tracked versions as the first line of an advance, while tanks in the wheeled mode would follow as guard tanks, and as such, be better able to react thanks to their higher top speed, like massing on a strong point or performing a local counter-attack. The wheel-cum-track tanks would also be able to support flanking recon or combat units or protect columns on the move. A tank with mixed propulsion was also considered suitable as a command tank. As the direct combat value of the wheel-cum-track design was not significantly worse than that of a fully tracked vehicle, they would be able to perform conventional combat roles as well. Moreover, as the wheeled units could be removed, it was possible to negate the issues with weight and total width which otherwise hinder this type of wheel-cum-track design.

More radical approaches were also explored, where tanks with mixed propulsions systems were seen as a potential replacement for armored cars. This built on the fact that the tracked system would allow cavalry units to pass difficult terrain and road obstacles while at the same time being more potent in the combat role. Logistical services like repair work and maintenance would also be aided by the fact that cavalry and tank units would share the same vehicle types. These advantages would, of course, be offset by the considerably increased cost of wheel-cum-track tanks compared to conventional armored cars. This view of mixed propulsion designs generally aligns with the opinion of Hauptmann Streich, who acted as a spokesperson for the Kraftfahr division of the German Waffenamt. He stated that a wheel-cum-track vehicle would be more suitable as a reconnaissance vehicle, rather than as a conventional tank.

The Sixth Vehicle – Author’s Theory

In historical writing and documents, there seems to be an inconsistency as to whether five or six vehicles were built. While German sources always seem to mention six vehicles, Swedish Army documents sometimes mention that only five vehicles were built.

The German-Soviet military cooperation was highly secret. This could mean that a sixth vehicle could have been kept secret from the Swedish Army and sent to Kama without them knowing. That would not only explain why the Swedes talked about five vehicles, but also why they never tested the vehicle with installed armor and armament. It is never even mentioned in Swedish sources that armor and armament existed. As such, it is very likely that the only vehicle that received armor and armament was secretly sent to Kama, with the Swedish army left unaware of its existence.

Conclusion

The greatest feat of the M28, or L-5, was serving as the catalyst of Swedish tank development, which would be headed by Landsverk until the 1950s. Trials of this vehicle proved largely positive and directly influenced the decision of the Royal Army Materiel Administration to place an order for the further evolved L-10 and L-30 designs in October 1931. While the purchase of a prototype of the newer type was considered, the limited funds and time frame rushed the acquisition process, resulting in a full purchase of the new designs. As for the competing tanks, the Bofors design proved to possess certain inherent design flaws. The Morgårdshammar design on the other hand, while displaying some positive features, could never be presented in physical form, and its head designer had by this point passed away due to disease. Meanwhile, the L-5 could mostly satisfy and in some cases exceed the requirements set up by Swedish authorities in 1928, and was thus the logical project to invest in. The development of these Landsverk designs would continue in Sweden as Otto Merker was employed at Landsverk directly in 1929, being tasked with creating a tank development division. He was appointed head of this division the following year. The establishment of a foreign subsidiary in the form of AB Landsverk allowed the German industry to gain experience with armored vehicle design throughout the 1930s in relative secrecy. Said experience was subsequently applied to help create the German armored force and its advanced designs as they existed in the lead up to the Second World War.

Drawing of the Landsverk BT.150 II from ~1930, one of the evolutionary stages between the L-5 and the following L-30. Photo: Krigsarkivet, special thanks to Karl Blomster for providing the photograph.


Illustration of the Räder-Raupen-Kampfwagen M28 or ‘Landsverk 5’ produced by Andrie Kirushkin, funded by our Patreon Campaign

Specifications
Dimensions 4.38 x 2.4 m (with wheels, 1.6 m body) x 1.48 (chassis only, on wheels) meters
Total weight, battle ready Aprx. 7 tonnes
Propulsion (TE and TM) (1-3) Benz-50-PS, 52 hp. (4-6) 70-PS-NAG-D7P, 77 hp.
Speed (road) 46 km/h (wheels), 23 kph (tracks)
Armament 37mm Gun
2x MG Dreyse 7.92 mm
Total Production 5 – 6

Sources

Die gepanzerten Radfahrzeuge des deutschen Heeres 1905-1945. Walter J. Spielberger, Hilary L. Doyle. Motorbuch Verlag, Stuttgart, 2002. p.94-99.
Safehaven: The Allied Pursuit of Nazi Assets Abroad, Martin Lorenz-Meyer, 2007, University of Missouri Press, p.10-11.
Paul Reusch und die Gutehoffnungshütte: Leitung eines deutschen Großunternehmens, Christian Marx, Wallstein Verlag, 2013.
The Secret School of War: The Soviet-German Tank Academy at Kama, Ian Johnson, MA thesis, Ohio State University, 2012.
Treaty Of Versailles, paragraph 171.
Merker, O. (1926). French patent No. 631.839. Paris, France: Ministère du Commerce et de l’Industrie.
Krigsarkivet, Arméförvaltningen, Artilleridepartementet, Konstruktionsavdelningen, Vol: F I:5
ASJ Landsverk, Lars von Rosen, Löddeköpinge: Sprinter AB/Maskinskyddarna, 2005, p.84
PANSAR Nummer 2 2014, Christer Badstöe
PANSAR Nummer 3 2014, Christer Badstöe
PANSAR Nummer 3 1982, Putte Hallberg
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