Categories
WW2 German prototypes

30.5 cm L/16 auf Sfl. Bär

Nazi Germany (1943)
Assault Mortar – None Built

After the Battle of Stalingrad ended in February 1943, a great effort was made by Germany to develop heavily armored vehicles armed to be more effective at assaulting fortified positions and buildings, particularly in urban environments. The realization that such a vehicle was required came soon after fighting in Stalingrad began, and the straightforward solution to this problem was presented at Hitler’s conference on the 20th of September 1942.

Fighting in Stalingrad has clearly resulted in the necessity of having a heavy gun in a heavily armored vehicle to fire high explosive shells capable of destroying entire houses with only a few rounds…

The initial result of this calling was the SturmInfanterieGeschütz 33B (Eng: Assault Infantry Gun 33B), a variant of the StuG III assault gun with a heavily modified box-like casemate armed with a 15cm (5.9 in) sIG/33/1 howitzer. With 80 mm (3.15 in) of frontal armor, the StuIG 33B was capable of directly attacking fortified positions while still being adequately protected against return fire.

Drawing of Sturminfanteriegeschütz 33B. Source: Panzer Tracts No. 8: Sturmgeschuetz – s.Pak to Sturmmoerser.

Twenty-four of these vehicles were completed by October 1942, with 12 of them being put into service by the end of the month and the other 12 in November. Despite being optimized for demolition work, however, it would be far from the most powerful assault vehicle designs to come out of Germany during WWII.

As though the StuIG 33B was totally inadequate for its role as a demolition vehicle, 1943 would see the manufacturing firm Krupp propose a quintessential German wonder weapon. At a total combat weight of 120 tonnes (264,555 lbs.), the 30.5 cm L/16 auf Sfl. Bär was nothing short of a behemoth. As a Sturmmörser (assault mortar) intended to reduce enemy defensive positions to rubble anywhere from several kilometers away to direct fire at point-blank range, the Bär (appropriately translated to ‘Bear’ in English) was to be matched in firepower only by towed siege artillery, railways guns, and the famous and slightly heavier Karl-Gerät siege mortar, all while having comparable armor protection to the Tiger II.

Krupp Takes The Initiative

Historian and author Michael Frölich states that the proposal for 30.5 cm L/16 auf Sfl. Bär was done on Krupp’s own initiative without any requirements being issued to firms for such a vehicle. This is a good example of Germany’s procurement system gradually breaking down as the war dragged on, as firms started to more frequently propose their own vehicle designs with homegrown requirements in the quest for more government contracts.

Sources differ on when the 30.5 cm L/16 auf Sfl. Bär was proposed. Historian and author Thomas Jentz states that Krupp proposed the concept on the 4th of May 1943, and had completed a drawing of the vehicle on the 10th. However, Frölich states that the design was presented by Dr. Erich Müller, who was head of artillery development at Krupp, to WaPrüf 4/II (Bureau for testing artillery for fortifications and fighting vehicles, of Artillery Section of Army Ordnance Office) on the 11th of March 1943 under the designation SKA 758, and given the appropriate name Bär.

Loaded For Bear

Bär was to be armed with a 30.5 cm (12 in) L/16 siege mortar in a casemate located at the rear of the vehicle. The mortar itself weighed 8 tonnes and was mounted on a carriage weighing a further 6 tonnes which was bolted onto the floor of the fighting compartment. Around the gun was a large curved mantlet weighing 2.5 tonnes. The mortar could be elevated up to 70 degrees but could not be depressed further than 0 degrees. When horizontal at 0 degrees, the gun rested on a travel lock which featured a hinged cap that swung up to cover the muzzle of the mortar and lock it in place.

The mortar could only traverse 2 degrees left or right, so when aiming, the entire vehicle would need to be turned to effectively get the mortar onto target. This issue was also faced by the French Char B1 heavy tank, which featured a hull-mounted 75 mm (2.95 in) gun that was fixed in traverse, so horizontal aiming was done purely by steering the tank. This issue was largely overcome with the development of a very sophisticated steering system which allowed very precise control of the tank during steering. Since the Bär used a transmission not designed for that sort of precision, it is possible that accurate aiming at close range would have been difficult to achieve.

However, it can be easily argued that, at close range with a 30.5 cm shell, aiming doesn’t need to be that precise.

At high elevation when firing at long range, accommodation had to be made for the massive breech of the mortar, which during recoil would travel 1 m (3.3 ft) rearward through a hole in the hull floor.

The mortar had a choice of two kinds of shell, a high explosive shell weighing 350 kg (772 lb), and an anti-concrete shell weighing 380 kg (838 lbs.). The high explosive shell had a propellant charge of 50 kg (110 lbs.) and was estimated to achieve a muzzle velocity of 355 m/s (1,165 fps) with a maximum range of 10.5 km (6.5 m). The anti-concrete shell had a 35 kg (77 lbs.) propellant charge and was estimated to achieve 345 m/s (1,132 fps) with a maximum range of 10 km (6.2 m).

Only 10 rounds were to be carried in the vehicle. However, this is not an unreasonably low number. As the shells each weighed hundreds of kilograms and a large winch mounted to the ceiling of the casemate was required to move and load them, the two loaders in the vehicle would have taken an exceptionally long time to load each shell, meaning the vehicle would not run out of ammo in any short amount of time. It also would not be unreasonable to expect very few targets to require more than one or two hits before they were no longer a threat.

According to historian and author Fritz Hahn, the 30.5 cm mortar was to be built by Škoda and would use ammunition that had already been manufactured as part of an old contract with Yugoslavia. No details about this contract are known, however.

Exterior blueprints of the Bär as drawn by Hilary Doyle. Note the horizontal line in the center of the sponson which represents the point at which the side armor transitions from flat to sloped. Source: Panzer Tracts No. 20-1 Paper Panzers – Panzerkampfwagen & Jagdpanzer

Running Gear

To take advantage of parts commonality, the 30.5 cm L/16 auf Sfl. Bär was to be built on a chassis that made use of components from both the Panther II and Tiger II. It would be powered by the Maybach HL 230 found in the Panther, Tiger I, and Tiger II, providing 700 hp at 3000 rpm. It would also use the L 801 double differential steering system of the Tiger II, which was an upgraded version of the L 600 found in the Tiger I, and the ZF AK 7-200 7-speed gearbox of the Panther. This would have given the Bär an estimated top speed of only 20 km/h (12.4 mph).

The reason for choosing the Panther’s gearbox for the Bär is that, on 17th of February 1943, a proposal had been made recommending that Tiger II and Panther II should share a number of standardized components, including the engine (HL 230 P30), gearbox (ZF AK 7-200) and cooling system. During the time when Bär was being developed, this proposal was still in place, so considering Krupp’s involvement in the development of Tiger II, it is to be expected that they would have been well aware of the advantages of including these standardized components in the Bär. Like both Tigers and the Panther, the transmission of Bär was located at the front of the vehicle, and because the casemate and gun were located at the rear of the vehicle, the engine and cooling system were located in the center of the vehicle in front of the casemate in a layout similar to the Ferdinand tank destroyer.

Exterior top blueprint of the Bär showing the layout of the engine deck. Identical to those of the Tiger II and Panther, this layout has the engine as located in the centre of the hull with the radiators located in the sponsons on either side.Source: Panzer Tracts No. 20-1 Paper Panzers – Panzerkampfwagen & Jagdpanzer

As a very wide vehicle, the Bär’s tracks followed the same design process as those of Tiger I and Tiger II, in that a set of narrow transport tracks would be fitted to allow the vehicle to be transported by rail or trailer, and a set of full-width combat tracks would be fitted while the vehicle was traveling under its own power. The transport tracks were to be 500 mm (19.7 in) wide, and the combat tracks would double that at 1,000 mm (39.4 in) wide. In comparison, the Tiger II’s tracks were 660 mm (26 in) and 800 mm (31.5 in) respectively. With the transport tracks fitted, the vehicle had a width of 3.27 m (10.72 ft) and with the combat tracks this was increased to 4.1 m (13.45 ft). Despite the use of such wide tracks, at 120 tonnes, the Bär would have had very poor performance off-road, with a ground pressure estimated to be around 1.13 kg/cm2 (16.07 psi), compared to the Tiger II’s 0.76 kg/cm2 (10.8 psi).

Exterior frontal blueprint of the Bär drawn by Hilary Doyle, highlighting the great width of its tracks and characteristic sloping of the side armor. Source: Panzer Tracts No. 20-1 Paper Panzers – Panzerkampfwagen & Jagdpanzer

The Bär featured overlapping 800 mm (31.5 in) road wheels but it is not confirmed if it was to use the same sprocket and wheels as on Tiger II. However, as the vehicle was intended to standardize on components with Tiger II, it is reasonable to expect that it would. Hilary Doyle, in his illustration of the Bär, presents it as having the sprocket, idler and steel-rimmed road wheels of Tiger II. This is supported by Thomas Jentz describing the road wheels as “rubber cushioned”, likely referring to the ring of rubber sandwiched under the wheel hub on either side of the wheel as a way to reduce wear without using rubber tires like those used on earlier Tiger I road wheels, which were prone to wear and contributed to rubber wastage.

While both Tigers and the Panther used torsion bar suspension which took up most of the space on their hull floors, Bär was instead, to use leaf springs. It is not known what these suspension units would have looked like but one of the main reasons for choosing leaf springs instead of torsion bars was to facilitate the inclusion of a baseplate built into the rear of the hull floor. This design feature would not be possible if the Bär used transverse torsion bars under a false floor like the Tiger and Panther. Prior to firing, possibly only for high elevation during low threat engagements, this base plate would be lowered onto the ground and locked in place. The purpose of this was to help absorb the massive amount of recoil generated by the gun during firing, which was estimated to reach around 160 tonnes of force. This design concept is present in some produced vehicles, such as the M55 and M110 Self-Propelled Howitzers, both of which feature a large dozer-like plate at the rear of the vehicles – known as a ‘recoil spade ‘ – which lower down onto the ground for the same purpose of absorbing recoil that could otherwise damage the vehicle, particularly the suspension.

Interior blueprint of the Bär, showing the transmission, engine and gun carriage. Also note the baseplate under the rear hull, shown in both its raised and lowered positions. The outlines of the mortar’s breech show the maximum length of travel during recoil at different elevations. At maximum elevation, the breech is shown recoiling through the hull floor, through a specially designed hole. Source: Überschwere Panzerprojekte Konzepte und Entwürfe der Wehrmacht

Layout

The hull of Bär greatly resembled that of the Tiger II in both shape and protection. The reason for such a level of protection was that, as an assault mortar, the Bär had to be capable of resisting incoming fire from some of the most powerful AT weapons of the time. The floor armor was also intended to protect against mines, a sensible concern for an assault vehicle. To achieve this, it had the following armor values:

  • Upper Hull Front: 130 mm (5.12 in) at 55 degrees from vertical, 222 mm (8.74 in) LoS (Line of Sight) thickness.
  • Lower Hull Front: 100 mm (3.94 in) at 55 degrees from vertical, 173 mm (6.81 in) LoS thickness.
  • Upper Sides: 80 mm (3.15 in) flat transitioning into 80 mm at 25 degrees from vertical, 88 mm (3.46 in) LoS thickness.
  • Lower Sides: 80 mm flat.
  • Rear Hull : 80 mm at 30 degrees from vertical, 93 mm (3.66 in) LoS thickness.
  • Roof: 50 mm (1.96 in).
  • Front Floor: 60 mm (2.36 in).
  • Rear Floor: 30 mm (1.18 in).
  • Mantlet: 80-130 mm (3.15-5.12 in), 130-300 mm (5.12-11.8 in) LoS thickness.
  • Casemate Front: 130 mm, 130-170 mm (5.120-6.69 in) LoS thickness.

The driver was positioned in the front left of the vehicle and the radio operator was on the right. Each had a swing-out hatch like those found on the Panther and Tiger II and a single rotatable periscope. Despite the intended use of the vehicle, the radio operator did not have a ball-mounted machine gun for close protection against infantry. In fact, no other weapon is described as being present on the vehicle, although it can be reasonably assumed the crew’s personal weapons would be carried. Because of the placement of the engine, these two crewmen were physically separated from the rest of the crew who were in the rear fighting compartment. The commander and gunner were positioned on either side of the mortar and each had their own swing-out style cupola with 8 periscopes. It is notable that, because of the vehicle’s 3.55 m (11 ft) height, the cupola periscopes were angled downwards to reduce the massive blindspot that would otherwise be present all around the vehicle. The two loaders were positioned at the rear of the casemate, where they could operate the winch and load the mortar, and there was a hatch in the lower rear hull for them to enter or leave the vehicle.

It should also be noted that, in the drawing showing the interior layout of the Bär, what appears to be the elevation wheel for the mortar can be seen significantly below the positions of the gunner and commander on the gun carriage. This suggests two possible options. One option was that the gunner did not fight with his head up in his cupola, but he instead moved down next to the gun carriage and adjusted the mortar without actually seeing what he was aiming at himself, with the commander directing him using his own sight. A second possibility was that one or both or the loaders had a second duty in adjusting the mortar and it was the gunner who directed them using his own sight (no actual gunsight is shown in the drawings). With the placement of the elevation wheel, it was not possible to be up in the cupola while adjusting the mortar.

One other mysterious feature of the Bär shown in the drawing is the object protruding from the rear of the casemate. As it is shown with a shell inside it, it can be assumed to have been some kind of loading tray for loading shells into the vehicle and then stowed in their ready racks. What is not clear however is how it functioned. The rear of the object appears to be a wall the same thickness as the armor on the rear of the casemate, suggesting the object slid inwards into the vehicle much like a drawer, so that the rear was flush with the armor. If that was the case, it is not known if this drawer action was done specifically to move the shells into the vehicle where they were then moved by the internal winch, or if the tray stayed in place during loading and the shells were manually pushed in from the outside or were pulled in by some kind of mechanical rammer.

The loading process would have been time-consuming and undoubtedly would require the assistance of a Munitionsschlepper (ammunition tractor) with its own external crane, much like the Munitionsschleppers that accompanied the Karl-Gerät siege mortars. This is supported by Fritz Hahn who states the Bär would indeed be supported by specialist ammunition-carrying vehicles, however, no other descriptions of this vehicle are provided.

Hahn also states that a lighter version of the Bär had been designed, weighing significantly less at 95 tonnes. However, once again, no other details are provided. This is likely because Hahn wrote about the vehicle four decades after WWII ended while relying mostly on his recollections, and with his personal experience not being related to armored vehicles, without evidence, it is highly likely that this claim is not accurate.

Possible later iteration of the 30.5 cm L/16 auf Sfl. Bär dated from December 1944, however, it could simply be an incorrectly captioned drawing of the Geschützwagen Tiger or some other obscure self-propelled gun due to the significant differences in the design, such as the missing mantlet and different casemate shape. Source: Waffen und Geheimwaffen des deutschen Heeres 1933-1945 by Fritz Hahn
Internal blueprint showing the internal components in more detail, minus the external loading tray. In this blueprint, the hatch in the lower rear hull is also visible. Source: German Armored Rarities 1935-1945

Misconceptions

As a unique and imposing vehicle, the Bär has proved popular amongst scale modelers, with modeling companies such as Amusing Hobby and Trumpeter producing their own model kits of the vehicle. However, a number of inexplicable inaccuracies are present in the models of both the aforementioned modeling companies.

These include:

  • The presence of a hull-mounted ball machine gun. While heavily inspired by the Tiger II, there is no evidence that the Bär possessed a hull machine gun.
  • A single cupola. While it is a sensible change to an impractical design, the Bär did not feature one cupola on the casemate roof, but a pair. As well as this, the cupolas on these models are not correctly designed in that the periscopes are not angled downwards to increase visibility, unlike the periscopes of the original design.
  • Fully sloped upper side armor. According to Doyle’s drawings for the Bär, the lower half of the sponson’s side armor was to be vertical, with the rest of the upper side armor all the way to the casemate roof being sloped at 25 degrees. There is no primary evidence that the Bär’s sponsons were fully sloped like that of Panther or Tiger II.
  • A complex cast casemate face. One of the most glaring changes to the Bär’s design in models is the presence of a large complex cast piece as the casemate’s frontal armor. There is no evidence to support such a design. While the Bär’s actual casemate face is highly curved in the vertical plane, it is completely straight in the horizontal plane. A comparable existing design would be that of the Maus, whose turret face very much resembles the shape of the Bar’s casemate face. This was produced by bending a straight armor plate using a huge metal press.

Fate and Conclusion

On the 27th of May 1943, in a meeting between the manufacturing firm Alkett and the Waffenkommission, Alkett revealed plans for a competing design in the form of a self-propelled 38 cm (14.96 in) mortar. Development for the vehicle was approved and by October the first prototype, a 38 cm rocket launcher mounted in a casemate built on a Tiger I chassis, was built and presented to Hitler. This vehicle would see further development and entered production as the 38 cm RW61 auf Sturmmörser Tiger. It is more commonly known as Sturmtiger.

30.5 cm L/16 auf Sfl. Bär seemingly ceased development sometime after Alkett revealed their competing design, and it is not hard to understand why. At 120 tonnes, it was significantly underpowered and, despite its enormous tracks, it would have had poor mobility and would have been vulnerable to sinking on anything but hard ground. While it could have been technically capable of fulfilling its intended role, the Sturmtiger demonstrated that the role could be more effectively filled by a vehicle half the size and weight without requiring vast resources to function.

With the existence of a later blueprint showing a significantly altered design, it is very possible that development of the Bär actually continued even after the introduction of the Sturmtiger, until at least December 1944.



Artists representation of the 30.5 cm L/16 auf Sfl. Bär in red-oxide primer with a 1.83 meter (6 ft) man for scale. Illustration produced by the author, Mr. C. Ryan, and funded by our Patreon Campaign.

Specifications

Dimensions (L-W-H) 8.2 x 3.27-4.1 x 3.55 meters (26.9 x 10.7-13.45 x 11.65 feet)
Total weight, battle-ready 120 tonnes (264,555 lbs.)
Crew 6 (Commander, Gunner, Driver, Radio Operator, 2 Loaders)
Propulsion Maybach HL230 P30 700 hp 3000 rpm
Speed (road) 20 km/h (12.4 mph)
Armament 30.5 cm L/16 Mortar (10 rounds)
Armour Hull 30-130 mm, Casemate 80-130 mm
For information about abbreviations check the Lexical Index

Sources

Thomas L. Jentz, Panzer Tracts No. 8: Sturmgeschuetz – s.Pak to Sturmmoerser
Thomas L. Jentz, Panzer Tracts No. 20-1 Paper Panzers – Panzerkampfwagen & Jagdpanzer
Michael Fröhlich, Überschwere Panzerprojekte Konzepte und Entwürfe der Wehrmacht
Fritz Hahn, Waffen und Geheimwaffen des deutschen Heeres 1933-1945
Michael Sowodny, German Armored Rarities 1935-1945


Categories
WW2 American Fake Tanks

Mobile Pill-Box Fortress

U.S.A. (1940)
Proposed Vehicle Design

The early 20th century was dominated by new technologies being developed in large numbers. To capitalize on these rapid advancements, monthly magazines were published that focused on bringing these new technologies to the general public’s attention. This proved to be a great success. The most popular example of these magazines is Popular Mechanics, which published its first issue in 1902 and continues to be published today. Another popular example was Modern Mechanix, which went through several name changes since its first issue in 1928 before its final issue in 2001.

The technologies featured in these magazines varied greatly in their application. Power sources, home gadgets, farming equipment and flying machines are but a few examples of the kinds of inventions and concepts featured. Most notably, particularly during both World Wars, was the inclusion of conceptual weaponry and armored vehicles. These were rarely competently designed. Due to a total lack of practical insight into the use of military equipment, the end result was often a design more appropriate for a science fiction setting than a real battlefield. Some designs featured in these magazines are notable for their relative practicality however, at least when compared to the rest, and their intended usage is somewhat reasonable for being designed by illustrators as nothing more than magazine filler.

Firepower Required

Before the United States entered the War in 1941, it faced a distinct lack of dedicated tank destroyers. While it would not be until late 1941 when the US finally adopted such a vehicle – the 75 mm gun-armed M3 Gun Motor Carriage – designs already existed in the previously mentioned magazines that were intended to fill a similar role.

The November 1940 issue of Modern Mechanix features a drawing of a large armored truck with two guns in an even larger turret-mounted behind the cab. This Mobile Pill-Box Fortress, as it is referred to in the magazine, by virtue of having a single turret on a sensible and presumably existing truck chassis, is on the higher end of practicality regarding conceptual designs found in these magazines. No other name is given to the vehicle and no further information on it can be found despite supposedly being based on a prototype built by a truck manufacturer based in Los Angeles, California.

The single page showing the Mobile Pill-Box Fortress and its description. Note the inconsistency in scale between the crewmen in the cab and in the turret, making judging the size of the vehicle difficult. Source: Modern Mechanix, Issue November 1940.

Design

The Mobile Pill-Box Fortress is based on a large truck chassis with two single wheels at the front and two pairs of triple wheels at the rear. The reason for two pairs of triple rear wheels should be clear, as directly above them is a huge domed turret housing a pair of 6 inch (152 mm) guns, presumably naval in origin.

Turret

The turret can rotate a full 360 degrees, but gun elevation and depression are not known. Depression would inevitably be limited in the forward arc due to the roof of the cab and the bizarrely located headlight mounted to it. Ammunition for the guns is stored in two racks, one upper and one lower. The shells are stored nose-up in two racks that run the full circumference of the interior turret wall. This allows a large number of projectiles to be stowed despite their great size. It is not shown in the drawing where the propellant charges are stored. It is possible they are stored at the front of the turret or on the right side of the guns where they would be obscured, but the most likely explanation is either that they were never considered by the artist or the shells are one-piece. No access hatch or door is visible on the turret.

Due to the great recoil generated by such large guns, the vehicle features four large outriggers around the turret ring. These outriggers appear to be telescopic in extension and fixed in place with no articulation, apart from being capable of extending and retracting their feet up and down. The outriggers are an appropriate design choice for a vehicle that, as the name suggests, acts as a stationary pillbox instead of a more mobile vehicle, capable of quickly relocating during combat.

The turret’s gunner is located on the left side of the guns and has no seat. He has a direct vision telescope that is mounted unusually far back in the turret which is aiming through a thin visor in the turret’s mantlet. Even though the sight would most likely move with the mantlet, and stay lined up to see through it, the field of vision as a result of being mounted so far back would be incredibly narrow. Only two other crewmen are shown in the turret, those being the loaders, who are each loading their respective guns. As 6 inch guns, each projectile would have been very substantial, at likely 45 kg (99 lb) or more in weight. With the turret having a pair of guns, this means that each loader has to lift and load projectiles by himself, which during sustained fire would be incredibly tiring without any loading aides such as a winch or conveyor, neither of which are shown.

Cab

The cab is located at the front of the vehicle. The driver’s position is assumed to be on the right side due to the placement of the only seat visible in the drawing, an unusual choice for an American vehicle. However, due to the perspective of the drawing, the seat may actually be more centered in the cab. On the left side of the cab is the assistant driver who operates at least one of the two machine guns present in the vehicle, both of which are in the front corners of the cab. Ammunition for the machine guns is stowed above the engine in the center of the cab. Due to the placement of the driver, it is likely that he operates the right-side machine gun instead of the assistant driver having to move back and forth between the two guns. Like some tanks with an assistant driver, it is likely that he would be expected to take over driving the vehicle should the driver be injured. They may also alternate duties each day.

There are a number of vision ports around the cab. There are two ports on the front slope which can be hinged open. Similarly, there is a large hinged port on the sloped roof. It can be assumed there is a second port on the right side which is obscured, but what these upwards-facing ports would be for is not clear. Each of the two machine guns in the front corners had their own fixed vision ports above them, which, like that on the turret, would provide undoubtedly poor visibility for those operating the guns. There is a fixed port on the left side of the cab, again it is likely the right side has the same. Lastly, there is a vision port in what appears to be an access door in the back left corner of the cab. A step is present below it on the outside, as is a handle. What appears to be two hinges spanning the width of the cab roof are also present. It is not clear how these panels would open.

Armor

No specific armor values for the vehicle are given, but while the drawing is poorly scaled it is clear that the armor of the turret is supposed to be very thick by standards of the time. The turret armor is intended to protect against shells and bombs (no specific shell or bomb is described), whereas no such requirement is given for the cab armor, but it is reasonable to assume it would be at least capable of resisting small arms and shrapnel. The engine has its own armored housing within the cab, and it is not known if the covers over the wheels are simply mudguards or if they too are supposed to be armored.

Fate And Conclusion

While at its core the Mobile Pill-Box Fortress is reasonably designed by the standards of the magazine it was featured in, no information can be found regarding the claim that it was based on a real prototype that underwent four months of testing by the US Army. After the United States joined the war, a great deal of effort went into developing and testing trucks carrying anti-tank guns in a wide variety of configurations.

The purpose of these vehicles was to be fast and easy to manufacture due to being built on existing chassis, as well as fast on the battlefield, able to quickly respond to reports of enemy tanks in an area and move to engage them. This manufacturing and doctrinal need are incredibly similar to the description of the Mobile Pill-Box Fortress, a truck-based vehicle capable of traveling up to 65 mph (105 km/h) to any threatened area to counter both tanks and infantry, and afterward, relocate to any other area in need of anti-tank support. However, due to the great weight of the vehicle, it is reasonable to expect it to be incapable of reaching such high speeds outside of long straight roads.

The choice of a 6 inch gun would be questionable, let alone a pair of them. The incredible capability of such weapons against both tanks and infantry cannot be understated, especially for 1940, but their immense size and weight directly influences the size of the vehicle, which in turn condemns it as almost entirely impractical. For the vehicle’s time, it can be argued quite easily that no practical advantage comes with having such large weapons in a vehicle like this, simply because far smaller and lighter anti-tank guns already existed that were perfectly capable of defeating any tank of the period. At the very least it would be easy to invent a more sensible gun for the drawing.

Despite the similarities between the purpose of the Mobile Pill-Box Fortress and the actual tank destroyers the United States would come to use, the sheer unwieldiness and weight of the vehicle would undoubtedly restrict it to roads only, greatly limiting its application as a strategically mobile weapon. The design, like so many from these magazines, is a great example of theory detached from reality and it is no surprise that none were ever built – this vehicle was purely for the readers of the magazine rather than actual use.



Representation of the ‘Mobile Pill-Box Fortress’ produced by the Author, Mr. C. Ryan, funded by our Patreon campaign.

Specifications

Crew At least 5 (Driver, Assistant Driver, Gunner, Two Loaders)
Speed 65 mph (105 km/h)
Armament Two 6 inch (152 mm) guns, Two machine guns

Source

Modern Mechanix, November 1940

Categories
WW2 American Prototypes

Pelican Project and Half-Track Amphibian Cargo Carrier T32

USA (1942-44) Amphibious Utility Vehicle – Scale model only

By July 1942, the US National Defense Research Committee (NDRC), while working on developing the DUKW amphibious transport, concluded that a larger amphibious vehicle would be needed. They presumably expected that the DUKW’s limited capacity of 2.3 tonnes would be inadequate during large scale landings. Testing was done on a number of converted trucks, however, it was found that wheeled vehicles with payloads over 6 tonnes faced severe problems due to the increased ground pressure and unsatisfactory traction on beaches, their most likely landing point. It was therefore decided that a new project would be started, looking at developing amphibious half-tracks. These were meant to provide forces with larger supply payloads during landings in Europe and the Pacific without the inherent problems that wheeled vehicles faced.

The GMC DUKW (“D” – year 1942, “U” – utility, “K” – all-wheel drive, “W” – twin rear axles), designed in 1941, started production at the end of 1942 and was to be the US Army’s backbone during naval landings. Source: warhistoryonline

The Pelican Project

As a result of converted trucks failing evaluation, a number of half-track designs were drawn up for the newly started Pelican Project. These ranged from payloads as little as 2 tonnes, all the way up to an ambitious 25 tonnes. Some designs, in an effort to lower ground pressure and increase traction even further, featured an extra set of front wheels. These extra wheels, if powered, could have increased off-road performance, but none of the designs with them were given any further consideration.
It is not known exactly how all these designs were judged, but the final design that came out of the project did at least see significant evaluation. As well as being the last design in the project, it was also one of the largest. Weighing an estimated 9 tonnes empty, with a 9-tonne maximum payload, the vehicle was to be 15.3 m long and 4.4 m wide, larger than any other amphibious vehicle at the time. The design was to use a Ford 400 hp V8 petrol engine powering a pair of either Kirsten-Boeing or Voith-Schneider vertical propellers, giving the vehicle a water speed of 13km/h.

Blueprint of the final design of the Pelican Project Source: Half-Track: A History of American Semi-Tracked Vehicles, by R. P. Hunnicutt
To take advantage of the large number of new M4 Sherman tanks being produced and to potentially ease the logistical burden of developing a brand new tracked vehicle, the Pelican half-track was to share its VVSS (Vertical Volute Spring Suspension) bogie design. It was to have two bogies per side, totaling four road wheels per side with a central separate return roller, as well as the same track link design as on M4.

VVSS suspension was the standard suspension design of most US armored vehicles until it was replaced on the M4 Sherman by HVSS (Horizontal Volute Spring Suspension). This surviving M4A4 can be found at the Portland D-Day Center, UK. Photo: Mark Nash
A full-width ramp at the rear of the vehicle provided access to the cargo hold which was large enough to accommodate a 6-ton 6×6 truck of any model. Unlike regular half-tracks, the 2.7m wide driver’s cab was placed at the very front of the vehicle in front of the engine. The driver was on the left and on his right would be seated the rest of the vehicle’s crew.
A number of scale models of the Pelican half-track were built and used in water tests, but the project was soon canceled and no working prototypes were built.

Half-Track Amphibian Cargo Carrier T32

In May 1944, the NDRC was requested by the Ordnance Department to once again design an amphibious half-track to assist during landing operations. One main difference with this new program, however, was that the vehicle was required to have a three quarter length track. This was similar to that of German half-tracks, instead of the much shorter two-bogie design of the earlier Pelican half-track and other US half-tracks. This design would reduce ground pressure by having significantly more track in contact with the ground and more road wheels to support to vehicle.
Sparkman & Steven, Inc., contracted by the OSRD (Office of Scientific Research and Development), drew up an initial half-track design with an empty weight of 17 tonnes, and a payload of 13.6 tonnes. At a maximum weight of 30.6 tonnes, this design greatly outweighed the earlier Pelican’s 18 total tonnes. This could be credited to the three quarter length track, but at 12.7 m in length and 3 m in width, the vehicle managed to stay significantly smaller in size.

Blueprint of the initial vehicle design. Note the sloped top edge of the hull, and the matching sloped waterline, suggesting the vehicle would be tilted back slightly when in the water. Source: Half-Track: A History of American Semi-Tracked Vehicles, by R. P. Hunnicutt
The vehicle was to be powered by the Continental R975-C4 petrol engine, coupled with the General Motors 900T Torqmatic Transmission. This combination, the same as on the M18 Hellcat, would have given the vehicle 400 hp with an estimated top speed of 48 km/h on land, and 13 km/h in water. The front two wheels were powered, and propulsion in water was provided by a pair of 711 mm (28 inch) diameter propellers underneath the rear of the cargo bed.


Scale model of the initial vehicle design. It is unclear why the model lacks the sloped top edge of the hull, the rounded bow, and the cover plate over the wheels that are present in the blueprint. It is possible these modifications were done in the time between the initial blueprint and the model being made. Source: Half-Track: A History of American Semi-Tracked Vehicles, by R. P. Hunnicutt
The tracks, being longer than those of the Pelican half-track, allowed the design to have 5 dual road wheels which were also substantially larger. The wheels were on independent torsion bars instead of VVSS bogies, giving them more vertical travel and providing a smoother ride. The tracks also differed from the earlier Pelican in that they were without return rollers, an unusual feature on US vehicles. The design of the links was the same as on the T87 105mm Howitzer Motor Carriage, an ongoing project to have an amphibious vehicle using M18 Hellcat components armed with a 105 mm howitzer, a project that ended soon after the war did.
The design was later modified to include an additional road wheel by moving the drive sprocket forward. The rear ramp was also reshaped to provide clearance when entering an LST (Landing Ship Tank), reducing its overall length to 11 m and its overall height to 3.05 m. On the 29th June 1944, the improved design was designated Half-Track Amphibian Cargo Carrier T32. It was requested that three prototypes be built for testing, but Army Service Forces denied the request and the entire project was canceled, just over one month after the project was started.

The revised design that was submitted for prototype testing designated T32. Source: Half-Track: A History of American Semi-Tracked Vehicles, by R. P. Hunnicutt


The ‘Pelican Project’ amphibious Half-Track.


Early version of the Half-Track Amphibian Cargo Carrier T32.


Later version of the T32.

These illustrations were produced by this article’s author, Mr. C. Ryan, and were funded by our Patreon Campaign.


Conclusion

While the Pelican design, had it been built, might have suffered to a degree because of its small ground contact area for its weight, both the Pelican and the T32 seem to have been reasonable designs for their requirements. Ultimately, the sheer number of DUKWs being produced from late-1942 onwards outmatched any potential production numbers of the two vehicles, making them largely redundant apart from their valuable ability to bring regular trucks and other large vehicles to shore.
The failure of both projects did not end the US’ interest in large amphibious cargo vehicles however, as they would go on to attempt others after the war. One such vehicle was the capable 7.3-tonne, 8-wheeled XM157 Drake in 1956, which did succeed at reaching the prototype stage. It failed to reach production, however, as the army’s interest became focused entirely on the far larger LARC-LX for its amphibious heavy cargo needs. A 4-wheeled vehicle with a 54-tonne payload, it would go on to serve in the Vietnam War and stay in service until 2001.
Dimensions (L-W-H)15.3 x 4.4 x 3.94 meters

Specifications (Pelican)

Total weight, battle-ready 9 tonnes approx.
Propulsion Ford 400 hp V8
Speed (water) 13 km/h

Dimensions (L-W-H)11 m – 12.7 x 3 x 3.05 – 3.34 meters

Specifications (T32)

Total weight, battle-ready 17 tonnes approx.
Propulsion Continental 400 hp R975-C4
Speed Est. 48km/h (land), 13km/h (water)
Payload 13.6 tonnes, several dozen passengers, or a single 6-ton 6×6 truck

Sources

R. P Hunnicutt, Half-Track: A History of American Semi-Tracked Vehicles, Presidio Press