Self-Propelled Gun – 2 Mild Steel Prototypes Ordered, 1 Built
With the onset of the Second World War in 1939, the United States began rapidly developing new self-propelled guns to modernize their antiquated ground forces, which were only equipped with towed guns. In early 1941, the Firestone Tire and Rubber Company submitted their proposal for a fully enclosed self-propelled gun based on the chassis of the M3 Stuart Light Tank. This vehicle was designated as the 75 mm Howitzer Motor Carriage T18. Two mild steel prototypes were ordered in 1942, but only one vehicle was completed before the termination of the T18 project.
The Beginnings of American Self-Propelled Guns
In 1918, at the end of the First World War, the United States began developing domestic self-propelled guns. These vehicles were inspired by French designs of the time, such as the Canon 194mm GPF sur affût-chenilles St Chamond, and based on Holt tractors. However, with the end of the war arriving sooner than expected, just a handful of these self-propelled guns were actually produced. These completed vehicles were used as a basis for future mechanized artillery development, but large-scale budget cuts in the early 1920s severely hindered any further experimentation.
American self-propelled gun development remained relatively stagnant for many years, with the United States’ first (and, until World War 2, only) mechanized artillery regiment, the 1st Battalion, 6th Field Artillery, being established in 1934. They were equipped with vehicle-towed 75 mm Pack Howitzer M1s, far from state-of-the-art. By the time World War 2 began, this was the only battalion of mechanized artillery in the United States Army.
As war began in Europe, a rushed re-militarization effort began in the United States. A single battalion of towed light howitzers would be nowhere near enough firepower for the upcoming global conflict, so field artillery battalions were restructured, and modern designs for future self-propelled guns were pursued. Of course, it takes a not-insignificant amount of time to develop and produce an entirely new vehicle, so an expedient solution was chosen. This resulted in the 75 mm Howitzer Motor Carriage T30, an M3 Half-track mounting a 75 mm Pack Howitzer M1A1. The T30 was rushed into service while development of a proper self-propelled gun continued.
75 mm Howitzer Motor Carriage T3
An early proposal for a self-propelled gun based on the Combat Car M1 was submitted in 1939. This vehicle, designated 75 mm Howitzer Motor Carriage T3, had a rather interesting design. The turret and upper hull of the Combat Car were removed and a short superstructure was constructed. The T3 HMC featured two guns: a 75 mm howitzer M1A1 in the right side of the superstructure and a .30 caliber machine gun located inside a modified M2A3 Light Tank turret on the top of the superstructure. Curiously, due to the lack of a proper gun mounting, a pair of doors could close around the howitzer to protect the crew. However, the doors had to be opened to traverse the gun, creating an opening in the casemate front. The vehicle’s armor was quite thin, at a maximum of only .625 in (15.9 mm) thick on the front of the machine gun turret and hull. Mobility was similar to the Combat Car M1, although the vehicle accelerated slower due to its increased weight.
The T3 HMC had a crew of three: gunner, loader, and driver. Even with a crew this small, the T3’s interior was still quite cramped. Issues reloading the howitzer and operating the machine gun were made apparent during testing. These poor crew ergonomics led to the T3’s eventual cancellation in 1940. With just a single prototype completed, the T3 Howitzer Motor Carriage was not considered successful. However, lessons learned during its development helped influence future self-propelled gun projects.
In June 1941, after the cancellation of the T3 Howitzer Motor Carriage, guidelines for a new self-propelled gun were created. This new vehicle was to act as a close-support vehicle and would mount either a 75 mm or 105 mm howitzer. It was to be based on the chassis of the M3 ‘Stuart’ Light Tank. Almost immediately, the 105 mm howitzer was dropped as a potential armament. The limited size of the M3 chassis would make operating the gun difficult and the howitzer’s weight would cause the vehicle to be front-heavy. With the 105 mm howitzer off the table, two designs mounting a 75 mm howitzer were proposed and evaluated.
The first, designated 75 mm Howitzer Motor Carriage T17, was based on the chassis of the M1E3 Combat Car. This chassis was chosen because of its sizable internal space. However, rather predictably, the T17 was canceled because it did not use the requested M3 Light Tank chassis. The vehicle never left the drawing board. This left just one capable design; the Firestone Tire and Rubber Company’s proposal, the 75 mm Howitzer Motor Carriage T18.
While it might seem unusual that the Firestone Tire and Rubber Company was contracted to produce an armored fighting vehicle, they had a long history of producing various other goods, including tank parts, for the American military. They produced tank tracks, M5 Light Tank turrets, artillery shells, and 40 mm Bofors anti-aircraft guns, to name just a few. Therefore, it was not completely unexpected for Firestone to attempt to develop an entire armored vehicle by themselves.
In October 1941, a wooden mock-up of the T18’s superstructure was produced by Firestone and fitted to an early M3 Stuart chassis. Suitably impressed and ready to suggest improvements, Aberdeen Proving Ground approved the production of two mild steel pilot vehicles. The first pilot was delivered in May 1942, when testing could finally begin.
The 75 mm Howitzer Motor Carriage T18’s Design
At a Glance
The T18 Howitzer Motor Carriage, from the lower hull down, was identical to a standard early production M3 Stuart. Both tanks shared the same lower hull design, suspension, drivetrain, engine, etc. However, the most striking visual change was the T18’s large cast casemate. The Stuart’s upper hull and turret were removed, replaced by the boxy fighting compartment designed to protect and contain the 75 mm main gun and three crew members.
The T18 was, much like the T3 HMC before it, armed with the 75 mm Pack Howitzer M1A1. The howitzer was fitted to a modified version of the M3 ‘Lee’ Medium Tank’s 75 mm gun mount and located in the front right of the superstructure. Within the vehicle, 42 rounds of 75 mm ammunition could be carried. For the gunner, an M1 periscopic sight was installed on top of the mount. Gun traverse limits were 15° to either side and between 20° to -5° vertically. The M1A1 howitzer could fire an assortment of rounds, including the M48 High-Explosive shell, the M66 High-Explosive Anti-Tank shell, and the M64 White Phosphorus shell. The M66 HEAT shell would have given the T18 HMC a fighting chance in an engagement with enemy armor. However, with a velocity of just 1,000 ft/s (305 m/s), this shell would have been quite hard to aim at any targets beyond close range. The M66 HEAT shell could penetrate a maximum of 3.6 in (91.4 mm) of armor. This gave the T18 HMC’s howitzer similar penetration to the M4 Sherman’s 75 mm M3 gun. The M1A1 howitzer’s maximum rate of fire was about 8 rounds/min, but even a trained T18 crew would probably not have been able to maintain that volume of fire. Limited by the spatial confines of the vehicle, the crew’s achievable rate of fire would probably have been no higher than 6 rounds/min.
To increase the firepower of the T18 HMC, two .30 caliber M1919A4 machine guns were placed in the vehicle’s sponsons. The machine guns were unable to traverse. Therefore, the only way to aim them was by turning the entire vehicle. The machine gun mountings and mounting locations were quite similar to those of the M3 Stuart. A maximum of 4,900 .30 caliber bullets could be carried within the vehicle. With its armament loadout, the T18 HMC could effectively fight as a direct-fire assault gun, neutralizing infantry with its machine guns, demolishing obstacles with high explosives, and even fighting tanks with its HEAT shell.
The T18 was a reasonably well-protected vehicle. While the cast armor of the casemate was flat, it compensated with pure thickness. The front of the casemate was an impressive 2 in (50.8 mm) thick, which would have offered reasonable protection against 37 mm rounds from a distance. The sides and top of the casemate were 1.25 in (31.8 mm) thick and the rear was just 1 in (25.4 mm) thick. As for the lower hull of the T18 HMC, the armor was unchanged from the M3 Stuart the vehicle was based on. The lower side of the T18 was the same thickness as the casemate side, 1 in (25.4 mm). The heavily sloped upper front plate and cast lower front plate offered .625 in (15.9 mm) and 1.75 (44.5 mm) of protection respectively. Finally, the rear armor of the T18 was 1 in (25.4 mm) thick, while the floor armor ranged from .5 in (12.7 mm) thick at the front of the tank to just .375 in (9.53 mm) thick at the back. Overall, this armor layout was reasonably thick for its time, protecting the vehicle against many of its common threats frontally from a distance.
However, this armor profile had a few disadvantages. Despite its thickness, the T18’s casemate armor was completely vertical. While this design decision increased the available space inside the vehicle, it limited the actual protection the armor could offer. Sloped armor can deflect and deform armor-piercing rounds, helping prevent a penetration. Completely flat armor, however, offers no such benefits. Incoming armor-piercing rounds maximize their penetrative effects. Furthermore, the weight of the casemate’s heavy frontal armor placed significant strain on the vehicle’s suspension. When observing pictures of the T18, the overloaded suspension becomes apparent quickly. The vehicle had a noticeable frontal tilt, as the vehicle’s rather forward center of mass placed much more strain on the forward bogie than it did the rear. Similar issues of front-heaviness plagued other uparmored American tanks, such as the Assault Tank M4A3E2 ‘Jumbo’ based on the M4 Sherman chassis.
The T18 HMC mounted the same Continental W-670-9A engine as the M3 Light Tank it was based on. This was a gasoline engine capable of producing 250 net hp at 2,400 rpm. Automotive testing of the T18 HMC was successful, revealing only slight differences in mobility between the T18 and a standard M3 Light. Both vehicles could reach the same top speed of 36 mph (58 kph) and had similar automotive characteristics. However, the slight difference in mobility was due to the T18’s increased weight of 14.88 tons (13.5 tonnes). For comparison, the standard M3 weighed only 14 tons (12.7 tonnes). Because of the weight disparity, the vehicles also had different power-to-weight ratios. The T18’s was 16.8 hp/ton (18.5 hp/tonne), while the Stuart’s was 17.86 hp/ton (19.69 hp/tonne). This difference was quite small and likely caused the T18 to accelerate slightly slower than the M3 Stuart. Regardless, having mobility only slightly worse than a very speedy light tank is still quite impressive and the T18 proved that it would have been able to maneuver around quickly and responsively.
Crew and Ergonomics
The T18 had a crew of just three, consisting of a gunner, driver, and commander/loader. To enter and exit the vehicle, two roof hatches were provided. While the T18 wooden mock-up had only one hatch, a second was added to the pilot at the request of Aberdeen Proving Ground.
Crew conditions inside the vehicle were likely poor. The driver’s only vision source was a single forward-facing periscope, severely limiting his ability to gauge his surroundings while driving. The vehicle did not have any pistol ports to peer through or a commander’s cupola, either. The only other source of precious situational awareness during combat was the gunner’s sight, which could only traverse as far as the gun could. The commander/loader did not have any source of vision at all, a very serious drawback. Understandably, the T18 would have been extremely vulnerable to flanking attacks during combat that it could neither see nor defend against. The vehicle’s lack of a dedicated commander combined with the limited vision of the crew would have resulted in a blind vehicle operated by overworked personnel.
Additionally, ventilation of the main gun was an issue. With no ventilation fans of any type, and a limited internal casemate volume, the vehicle surely would have filled with dangerous fumes when the main gun was fired continually. The only way to ventilate the crew compartment would have been to open the roof hatches, which created another problem. Driving around un-buttoned in the middle of combat is not generally considered to be a good idea, especially in close-quarters fighting. Crews would have been stuck between a rock and a hard place. Either they could try and ignore the gasses created by the howitzer or they could compromise their protection by opening the roof hatches. However, for the long-range indirect fire duties that T18 crews would have invariably found themselves participating in, opening the hatches would have been a much smaller issue. Far from the frontline and in much less imminent danger, opening the hatches to increase crew visibility and casemate ventilation would have been a no-brainer.
While the T18 offered some advantages over its predecessors, including thick frontal armor and the usage of a standardized chassis, the project was doomed from the start. A month before the first pilot vehicle was delivered in May 1942, the Ordinance Department canceled the T18 program. Even without a physical vehicle, it was clear that the T18 had many intrinsic issues that made it unfit for service. The vehicle’s flat armor, front-heaviness, lack of vision, and poor gun traverse limits were cited as the main reasons for vehicle’s rejection. The fate of the prototype following this decision is unknown. A popular theory states that the pilot was kept on display at Aberdeen Proving Ground until it was destroyed in 1947. However, this remains unproven and the current location of the prototype, if it survives, remains a mystery.
The 75 mm Howitzer Motor Carriage T18 was just a single stepping stone in the development of a 75 mm American self-propelled gun. Before the vehicle was even canceled, new development requirements were put forth by the Ordinance Department in December 1941. Reflecting the lessons learned from the T18 program, these requirements requested a self-propelled gun design based on the M5 Light Tank chassis and utilizing sloped frontal armor.
In an attempt to satisfy these conditions, two designs were proposed in April 1942. These were the T41 and T47 Howitzer Motor Carriages. The T41 was an open-topped turretless design on the M5 chassis and the T47 was a proposal mounting a new open-topped turret in place of the M5’s standard turret. The T47 was considered to be the best design and, as a result, the T41 was canceled almost immediately. The T47 was continually improved and developed, resulting in the now-familiar turret with the large barrel flash deflector and direct vision hatches in the front of the hull. This new turret combined with the slightly-modified hull of the M5 Light Tank was standardized in May 1942 as the 75 mm Howitzer Motor Carriage M8 ‘Scott,’ a vehicle that would see widespread service with the United States and its allies via the Lend-Lease program as a successful infantry support weapon.
75 mm Howitzer Motor Carriage T18 Specifications
Dimensions (L x W x approx. H)
14’10” x 7’4” x 7’
4.53 x 2.24 x 2.13 m
75 mm M1A1 Pack Howitzer (42 rounds)
2 x .30 caliber M1919A4 Machine Guns (4,900 rounds)
Front: 50.8 mm
Side: 31.8 mm
Rear: 25.4 mm
Top: 31.8 mm
Upper front: 15.9 mm
Lower front: 44.5 mm
Side: 25.4 mm
Rear: 25.4 mm
Engine deck: 12.7 mm
Floor: 12.7 mm to 9.53 mm
If someone tried to define the term ‘tank’ as a military vehicle, they generally would agree on the need for a turret, armor, and tracks. Whilst there are exceptions to each of these to one degree or another, the only real unifying point across definitions is the use of armor and this raises interesting possibilities, especially for Henry Wallace of Freeport, New York, USA. In 1942, Henry Wallace expanded the idea of what a tank can be to a vehicle with no tracks at all. In fact, Wallace did not even go for wheels for some wheeled tank/armored car, nor did he go the full way towards a legged machine. Instead, Wallace went for perhaps the most unusual method of transportation possible, a vehicle that walked on one leg, pushing what could be named as a tank to a new extreme.
The patent for this odd design came from Henry W. Wallace of Freeport, New York State, USA. He should not be confused with the US Secretary of State for Agriculture of the time with the same name. Freeport, New York, is not a large city but, as of 1940, there were just over twenty thousand people living there according to US Census Data. The only other patent from this man was filed in October 1940 and was for a flexible pen in the shape of a snake wrapped around the wrist. With a relatively common name and few other details to go off, there is insufficient information to be able to reliably identify the designer at this time.
There are inherent problems in a tank design that involve compromises. Whether operating on wheels or tracks, movement is limited to the direction the vehicle faces and a change in direction involves turning or reversing. Protection for the vehicle is concentrated forwards to protect from fire from the front, as it would be too heavy and impractical to add equivalent protection to the sides and especially to the rear. Thus, a conventionally laid out combat vehicle is more vulnerable from the sides and rear than the front. Any turning or change in direction by the vehicle might expose that weakness to an enemy. A vehicle on which all sides are equally armored does not have to worry about the direction of an enemy attack or even turn to face it.
The same is true for armament. With a vehicle carrying a turret armament, it has to be turned to target a specific threat, and, once more, the maximum of protection faces the enemy threat. Armor protection, as both weight and bulk have to be shared between the turret and hull, provides a challenge for a designer as to where to use the armor for optimal value.
With those two primary considerations in mind, the conventional vehicle cannot deliver equal protection and firepower all round – for Wallace, the solution was effectively a simple one. Create a vehicle that was symmetrical in defensive capabilities and offensive alike, and this meant a circular body. This body would make the tank especially valuable in a defensive situation, where it could simply ‘sit’ as a bunker to guard or control an area and then, when the job was done, move on.
The propulsion of such a vehicle could not rely upon tracks or wheels, as it would not be able to change direction quickly enough in the mind of Wallace. Instead, he opted for a single leg which was located in the center of the doughnut-shaped machine. With this, he felt, the tank would be able to “oscillate” to move, with all-round gun positions guaranteeing that firepower constantly faced the enemy. Thus, the vehicle could advance, retreat or move sideways without regard to enemy position or flanking attacks.
With a doughnut-shaped body resembling a pressure cooker or saucepan with a lid, the machine was certainly odd. The ‘handle’ of the lid was a small cabin that could be rotated in any direction and in which sat the driver of the machine, with a view slit for observation.
The rest of the machine was circular, with 6 gun positions located at 60 degrees from each other. Each position had a field of fire of up to 45 degrees to each side, which managed to create small blindspots immediately alongside the vehicle between the guns.
The smooth exterior of the vehicle was broken up by the 6 gun positions, but there would be no sign of the propulsion leg from the outside when the vehicle was ‘sat’ down as a pillbox. The leg itself resided in an octagonal area within the floor of the tank, with its gearing and hydraulic actuators around it to control its position and direction. The extension of the leg, however, was not done hydraulically but using compressed air or, as suggested by Wallace, by means of an explosive expansion of gas. This might have seemed like a good idea for a patent application, but was utterly preposterous for even this rather silly design. The automotive power was to come from a two-stroke fuel-injected diesel engine of an unspecified type. In a lengthy explanation of how the whole system was meant to work, Wallace explained that this explosive method was to work by releasing fuel into the top of the hollow extensible cylinders which formed the leg and that, with a single detonation of a cartridge into this cylinder, the explosive gases from this detonation would rapidly propel the vehicle upwards to get out of trouble or leap into action. Quite what effect this bounding kangaroo leap would have on the occupants is not explained and perhaps was never even considered as a possible issue or concern.
The rest of the internal arrangement within the machine was relatively straightforward. Between the outer walls, with those 6 gun positions, was a raised fighting platform under which ran a lot of the mechanical equipment (such as pumps) to run the machine. The outer skin of the machine was supported at the top and bottom by supporting beams. Despite the size of the machine and the number of men within it, just one hatch is shown in the patent drawing, in the rotating cabin for the driver at the top.
In terms of crew, even assuming just one man per gun (x 6), a driver, and a commander would mean not less than 8 men to reasonably crew this vehicle.
Whilst there have been designs for walking machines before, they usually relied upon continual support by their legs even when not in motion. More than that, they also had to depend on at least 2 legs for bipedal stability or more in motion. Wallace eschewed such ideas or any concept of motion short of brachiation from nature and went instead for a system using one leg. It is obviously not possible to walk on one leg without a hopping motion, but the design did not produce some giant pogo stick type of movement. It instead had an unusual undulating step where the second ‘foot’ would be the vehicle itself.
Consisting of a giant doughnut shape, with the single leg occupying the central recess in the bottom, at rest, the vehicle sat on the ground as a giant round fort or pillbox. During this phase, the leg could move forwards to a position in the direction of movement and then lift the whole vehicle off the ground, bringing it upwards and in the direction of travel. Now having moved a short distance ahead or in any direction, the leg would collapse slowly bringing the vehicle back to rest on the ground. The process would then repeat for as long as may be needed to move from location A to B. At all times whilst sitting on the ground, the leg was completely enclosed by the body and the vehicle provided both maximum firepower and maximum protection in all dimensions simultaneously. Using four large wheels, one on each side of the leg, and an element of rotation within the housing for it, the leg could be prepositioned in any direction in anticipation of a move that would be unknown to anyone outside the machine by observing it.
There are, however, serious problems with this method of motion, not least of which are ground pressure, balance, and speed.
Firstly, with the entire weight of the vehicle concentrated onto just a single point of contact with the ground. As the leg extended hydraulically into the ground to raise the body, it would sink into anything other than a good hard surface. The result would potentially be the leg impaling the ground to an extent that it might not be easily removed. This would be the military equivalent of trying to walk on a beach in high heels. If this sinking happened when the body was off the ground, the result could be disastrous, as moving a point of balance beyond the lip of the foot would result in the machine flailing over.
This brings up the second point of balance. Not only could the machine potentially tip if the ground shifted or leg sank when moving, but this would be magnified as a problem moving on anything other than a flat surface. Whilst the foot itself had a semi-flexible coupling in the manner of an ‘ankle’ connecting it to the base of the leg, the foot allowed for a limited degree of flexibility. Measurements of the vehicle would indicate that it would become unstable past 10 degrees of any slope. This would render the vehicle unable to operate on anything other than ideal flat terrain. Wallace sought to correct this rather obvious deficiency with his idea by stating that it was to use a gyroscopic stabilization device located around the center of gravity and consisting of two oppositional gyroscopes.
The final major problem with the practicalities of the mean of motion for the vehicle is speed. Movement in the chosen direction is limited by the amount of movement available to the foot at the point when the body of the vehicle is on the ground. Moving the foot in the desired direction whilst on the ground (1), as the hydraulics push on the foot, the body gradually lifts off the ground and is righted to a new forward position (2) until reaching full height (3). The tank can remain at any elevation between ground level and (3) for combat, although this would expose the leg to enemy fire. Return to the ground starts from the elevated position (4) down vertically (5) to the new resting position (6), a short distance from point (1). To continue the motion, the leg is moved to the new forward position (7) and the vehicle rises (8) to a new elevation (9) and so on.
One step beyond this slow move-lift-lower means of motion, Wallace drew an even more fanciful one. Here, the leg would do far more than even those rather absurd methods of movement, showing the tank literally jumping.
This slow move-lift-lower process could be sped up to a ‘dragging’ speed whereby only enough pressure need be applied to the foot to raise the body from the ground far enough that the hydraulics for the leg movement could drag it forwards and then return to the body to rest as the foot moves again. It is surely this method that would have been the only practical way of moving the vehicle, although practical is not really applicable to such an implausible design.
Wallace made no mention or estimate of the speed of this system of propulsion, but it was clearly not possible to combine a rapid bounding from the machine with a chance of the crew being in a fighting condition, even assuming the system had worked. The easiest, simplest, safest form of motion, the dragging method, would perhaps at best manage walking pace on a good surface.
As with many other features of this vehicle, little information can be discerned on which to judge the level of protection provided. No information is provided other than to say that protection was implied as being equal in all directions. From the approximate scale of the vehicle, the size of the seat, and space for the crew, the drawing would appear to indicate armor would have to have been metal (presumably steel) and not much more than bulletproof in thickness.
With 6 evenly distributed guns around the outside, it is unclear what sort of firepower Wallace had in mind. An enemy could be engaged at best by just two of the guns at any one time, leaving ⅔ of the firepower idle. Wallace could simply have had a rotating turret with a single large gun or multiple gun mountings, which would have obviated the need for so many crew and guns. Instead, unless the vehicle was totally surrounded, then all of the firepower could never be used at the same time and none of it when moving.
Weakly protected for a static pillbox, poorly protected for such a visible tank, and oddly armored for a fighting vehicle, the design was particularly bad when it came to motion. The single-leg concept, as drawn, was preposterous and unlikely to work even on a flat and hard surface, let alone a modest slope or wet ground. There, this tank would display the mobility of a lawn dart when moving and a house brick at other times, with less potential than either.
What Wallace was trying to secure as intellectual property with this design is clearly the single springing leg concept and a tank of equal protection and firepower. What he actually designed was perhaps one of the least practical, workable, or sensible systems of vehicular motion imaginable.
Trying to imagine what possible use this vehicle might have had to the US military or Allies in 1942, when it was submitted, is even less clear. Today, it can be seen as just one of those ideas from a well-meaning public eager to engage in and/or profit from the war by producing war-winning weapons and ideas. Sadly for Wallace, this was not one of them.
USA/United Kingdom/Belgium (1938-1941)
Light Tank – 1 Partial Prototype
Many people interested in tanks have likely heard the name Walter Christie and are aware that he produced several prototype tanks during the period between WW1 and WW2. Whilst his vehicles had some good features, overall they were not a commercial success for Christie, who had amassed a lot of debt in developing and building them. The result was that some of his assets, his tank prototypes included, ended up being used to pay off his debts and his ‘high-speed tank’ was one of them.
Sold to pay off Christie’s debts, this vehicle ended up in the hands of a German-born American businessman, Siegfried Bechold. This new owner rebranded the tank, had some additional design changes made and then, at the start of WW2, tried to sell the ‘new’ design to both the Belgians and the British.
The Belgians needed tanks urgently but this design would come too late to help them. The British expressed interest as the light weight of the machine was suited to their need for a tank for airborne operations, and by 1940 the British Purchasing Commission was actively considering the vehicle for production. Nonetheless, the idea was over by 1941, when British attention switched to a vehicle with more armor and firepower than the ‘Bechold’ tank. Even so, this early design and the consideration of it adds to the story of how the British were trying to develop their own ideas for a new kind of mobile warfare and airborne operations.
The enigmatic Mr. Bechhold
The name Siegfried Bechhold means very little even to the most ardent tank enthusiast. However, just prior to WW2 and into its first years, Bechhold was one of the most prominent men involved in tank design and production in America, despite never having produced any tanks. This peculiar state of affairs takes some digging to get to the bottom of, as does the man himself, not helped by his name appearing variously as Bechhold, Bechold, and Buchhold.
Siegfried Bechhold appears to have been born in Bavaria, Germany in 1900, although a newspaper article from January 1941 puts his birthplace as Holland. This is likely one of those situations where people de-Germanized themselves to try and disguise their German ancestry, something which was a common occurrence at the time, especially with the switch from ‘Deutsch’ to ‘Dutch’ in terms of self-description. Another account of his early life (from April 1941) stated that he was born in Bavaria and lived in Germany until he was 11 – so maybe his family moved to Holland or maybe he was just hiding his background.
Bechhold recounted his story that, at the age of 16 (so ~1916), he was, like tens of thousands of other German boys, drafted into the German Army during World War One, although it is not known if he saw any active service or not. By 1922, with WW1 behind him but in a country ravaged by economic and social problems, he managed to make the transatlantic voyage to the United States, arriving in New York with just US$40 to his name.
His first jobs were very poorly paid but, by the late 1920’s, he was living as a tenant at 34 East 62nd Street between Madison and Park Avenues (this house was demolished in an explosion in July 2006). He had been learning English at night school and had managed to get a job as a salesman, which proved very successful for him. So successful was it, that this man, who had arrived in the USA just a few years before, could now afford to travel back and forth to Europe. He would later claim that he used these trips to pass on information about German rearmament efforts during the early 1930’s and that he believed that Germany was far ahead of other countries in weapons development, although this sounds more like his sales-speak for selling tanks than the serious recollections of an international spy.
What is known though is that during this time, he, like many others, saw the tanks of Walter Christie. These were very well covered in the newspapers and newsreels of the age with Christie’s penchant for publicity stunts. Seeing a potential business opportunity, Bechhold was interested in these tanks which were significantly faster than other tanks of the age, and in many ways the most advanced tanks in the USA at the time.
Bechhold later reported that he was encouraged in his interests by Congressman Ross Collins of Mississippi, although how these two men knew each other is unknown. It was, according to Bechhold, Collins who encouraged him to produce tanks in the United States but Bechhold was not a technical man nor an engineer despite being Vice President of the Bethlehem Engineering Export Corporation of Wall Street, New York. He was skilled in salesmanship and finance. He was, however, despite his lack of engineering skills, to be credited in the US press as coming up with the idea of putting lightweight aircraft engines into tanks in place of ordinary diesel or petrol engines, although this too sounds more like the pitch of a salesman, as Christie had already done this years beforehand.
As an aside to his tank work and to give a flavour of the way in which Bechold was trying to avoid being labelled as anything other than as a patriot, he embarked on a vigorous self-justification campaign in the media, making sure no one was in any doubt as to his loyalties. As a result, in June 1941, it was reported that Bechhold, a naturalized citizen and “intense” patriot, had refused to sell his tanks to the Russians at the time of the War against Finland. Furthermore, it was claimed that, in the new war against Hitler, he would only sell them when the Russians went to war with Hitler, even though there seems to be no evidence whatsoever for this claim.
The Tank Company
By the end of the 1930’s, Bechhold had his opportunity. Walter Christie, a man of undoubted technical gifts, was running short of investors who wanted to keep losing money on his tanks. One vehicle of his, a “high-speed tank”, had to be handed over to the partners of the Hempsted Welding Company of New York, William and Alfred Christ, as a lien against unpaid debts owed to them by Christie. Exactly which of Christie’s vehicles this was in unclear but as the M.1938 was later presented by a Mr. Bigley with some involvement from Christie suggests that Bechhold got hold of the M.1937 high speed tank from Christie as the basis of his design. However, whilst exactly which vehicle may not be known, Christie’s creditors were to be appeased with a tank available for purchase to pay his debts.
Bechhold had, through Bethlehem Engineering Co. been engaged in a commercial contract with Christie which started on 9th August 1938 whereby Bechhold and his company were granted exclusive rights to sell and manufacture the design from Christie for the princely sum of US$5,000 (just over US$91,000 in 2020 values). The idea of the partnership was simple. For this initial outlay of cash to Christie, Bethem Engineering would take the full blueprints of the design, market them globally and grant manufacturing licences for US$50,000 to each national licensee. This US$50,000 (US$915,000 in 2020 values) would be split 50:50 between Bethlehem Engineering and Christie for which the licence got not only the blueprints but also a master mechanic or draughtsman from Christie. This agreement simply fell apart not least in part to how appallingly badly written and complicated it was. In the words of the New York Second Circuit of Appeals in July 1939 ruling on whether to grant an injunction against Christie for breach of his contract:
“This contract is so obscure, and, strictly taken, so incoherent, that nobody can be sure of its meaning, but so far as we can spell it out, this is what it was. The defendants made the plaintiff its exclusive agent to sell licenses to prospective manufacturers of their tank in foreign countries — perhaps also in this country as well, though apparently it was not included. The plaintiff was not free to sell such licenses generally, but only for those countries where the parties thought it “practical” to do so. The minimum license fee was to be $50,000, but the plaintiff was to try to get more, and the parties were to discuss the amount in advance: probably this implied that they should agree upon it.”
105.F.2d 933 (2nd Cir. 1939)
With the case between them ending in confused acrimony, Christie and Bethlehem Engineering’s relationship was over. Christie had won that case due not least in part to how confusing the agreement was between them over rights and whilst he had retained his rights over his design he was also financially crippled.
Bechhold too had moved on and was no longer involved with the Bethlehem Engineering Expert Company and, instead, on 25th July 1939 (just 2 weeks after the ruling), formed the Armored Tank Corporation (A.T.C.), incorporated in New York. Initially, this company had just 100 shares of stock (30 Class A, and 70 Class B) at a value of US$50 each (Total nominal value US$5,000).
The purpose of the company was to acquire the Walter Christie high-speed tank from William and Alfred Christ. On 31st July 1939, this tank was purchased for an undisclosed sum along with 34 shares (Value US$1,700) in the new company (6 more were given to the attorney for their legal services). The Armored Tank Corporation (A.T.C.) of New York was now in possession of the Christie High-Speed Tank, the rights over which had fractured the relationship between Christie and Bethlehem Engineering. Bechhold now had the vehicle and also the more difficult task of making money from it.
Within a few months of formation of the company and the purchase of this High-Speed tank, Bechhold was recruiting a draughtsman. Between December 1939 and January 1940, A.T.C.’s draughtsman prepared blueprints and drawings of this Christie tank with some modifications. During this time, a license agreement for the production of this modified Christie high-speed tank was acquired in Belgium. The Belgium firm, Ateliers de Construction de Familleureux, paid an advance royalty of US$10,000 for this license. Whatever plans there were in Belgium for this vehicle though are unknown, as the nation was overrun by the Germans in May 1940, with no Christie tanks produced.
By the end of 1940, the first glimpse of what A.T.C. was working on can be seen. In November-December that year, it was advertising ‘Super-Tanks’ in the US Army Ordnance Magazine as being “built in all weights” by the Armored Tank Corporation at 30 Church Street, New York. This was formerly the location of numerous businesses such as the National Manufacturing Company, American Locomotive Sales Corporation, and the New York Railway Club (close to the site of the World Trade Center Complex today and now the location of the Century 21 Department Store). The same advert appeared that same month as being constructed by the Pressed Steel Car Co. as well.
Although the tank was never built as shown in the 1940 image with the low cylindrical turret there was a photo of a mockup of the Bechold tank was circulated in the press by least the early part of 1942. This vehicle had the same distinctive rounded nose glacis and two hatches in the driver’s plate. Off-center to the left of the driver’s plate, next to the left hatch was a mockup of a gun of unknown type although it appears too large to be a simple machine gun. The gun is roughly in the same position as what appears to be a small machine gun on the 1940 artist’s impression. The most noticeable difference between the 1940 drawing and the mockup (other than the lack of turret on the mockup) is that 3 wheels can clearly be counted on each side along with what appears to be a pair of return rollers instead of 4 wheels with no return rollers. Also apparent is that whilst the return rollers appear to be real, the photo may have been editted to make the vehicle appear shorter than it was.
Based on the available photograph, the drawing, and information from the company’s advertising of it being “Built in all weights”, a brief analysis of the vehicle shown is possible.
In December 1940, Bechhold was reported to have been producing ‘Medium Tanks’ for the British and had also submitted a design for an airborne tank. This tank was at the time being reported in the press as weighing 10 tons (9.1 tonnes), 14 ½ feet (4.42 m) long, fitted with armor one-inch (25 mm) thick with a single 37 mm gun and a machine gun. Also noted was that it would carry two sub-machine guns, suggesting a crew of just 2 or 3. A final note is that it was designed to be carried under “a Douglas plane”.
This description is immediately reminiscent of the Christie promotional idea of an underslung high-speed tank from 1936. In that artwork, a 3-wheel Christie turretless high-speed tank was pictured being carried under an Air Corps bomber.
An idea of quite how a system for carrying a tank in this manner under a plane would work can be found in a May 1941 Patent. This was filed by Alfred Anderson, assignor to the Armored Tank Corporation for a ‘Hook-on-and-Release-Mechanism for Fighting Tanks’. This invention describes an invention for attaching tanks to aircraft, specifically slung below the plane, and for dropping the tank when in flight. This is a different system to the one from Christie – that one used a pair of scissor arms to grab and retract the tank.
Instead, four upside-down triangular fittings would be attached on the underside of the fuselage of the aircraft. Each held a hydraulically controlled actuator with a large stud pushed out on a spring. When hydraulic pressure was applied, this spring would compress withdrawing the stud back inside the actuator. This would release the tank, as these four studs were attached via holes into the body of the tank. These would not be disengaged simultaneously, but in pairs. The rear pair would disengage first, allowing the bottom of the tank to hang down as the carrying plane swooped in suicidally low over the ground. At a suitable point, the front studs would also then be disengaged releasing the front of the tank. The back end of the tank was then supposed to hit the ground first from a lower height, with the front end following. This method was intended to overcome the turning effect on the vehicle. The dangers to the vehicle crew and to the aircraft performing this maneuver cannot be overstated; this was really a system designed to get the plane and its tank shot down. Even if it did work and the tank was deposited safely to the ground, one wonders how long it would take the crew to become operational after such an experience.
The vehicle shown in that 1936 promotion art for Christie is different from the vehicle in the 1940 ATC advert though. For sure, ATC got a Christie High-Speed Tank but its vehicle is much closer to a vehicle the size of the M3 Stuart or even the M1 Combat Car. What can be seen from the advertising image is that it was a small tank with a distinctive rounded back end to the hull running on four closely-spaced Christie type wheels (and presumably Christie spring suspension too). No track guards or mudguards at all are shown. The track itself is very similar to the flat plate track of the Christie tanks.
The nose lacks any indication of the pointedness of the earlier Christie High-Speed tanks but is uniformly rounded leading to a long glacis sloping up to a slightly inclined driver’s plate. Where the glacis meets the driver’s plate, there are two structures that appear to be mounts for fixed hull machine guns. In 1940, it should have been obvious that fixed, forward-firing machine guns were utterly useless but it was an easy way to add what was thought of as additional firepower to a design and many tanks subsequent and independent of this one retained this feature, including the M3 Grant, M4 Sherman, and Canadian Ram.
The driver’s plate featured two rectangular hatches, each with a vision slit. Out of the front of the left-hand hatch was what appears to be a heavy machine gun. From the position of the hatches and hull weapons, it would appear to have had a driver mounted on the right and hull machine gunner on the left. A third man, the commander, would most likely occupy the turret. The turret itself, as drawn, is very unusual, looking like an overturned cooking pot. On the roof was a full size (it occupies the entire roof) hatch in two parts, each opening sideways. A series of slits were placed around the exterior of the turret and at least two machine guns, one forwards and one to the left. In total, the firepower for this vehicle as drawn was 4 machine guns and one heavy machine gun.
Presumably, the part about being built in ‘all weights’ was to mean that different options in terms of fittings, armor, and weapons were potentially on offer. Certainly, the specifications and look of the vehicle were very up to date given the parlous state of US tank development at the time. The T4 medium tank, for example, from 1935/1936, was a very promising design but was 13.5 tons and capable of just 35 mph with 3 machine guns. The Bechhold tank was, at least on paper, better armed, better armored, smaller (about 50 cm shorter), and faster. No surprise then that it was an interesting prospect for investors interested in lucrative future army orders.
The potential of the A.T.C. tanks from Bechhold’s company had indeed gained attention. In June 1940, a British Purchasing Commission had arrived in the USA to look at the possibility of producing and purchasing tanks for the war effort. Great Britain had, of course, been at war since September 1939, and June 1940 was just after the evacuation of Dunkirk, a time when a lot of British armor had already been lost on the continent with the fall of France. Great Britain and its Empire now stood resolute against the Axis of Germany and Italy but it desperately needed tanks and arms to fight the war.
The same month, Bechhold managed to interest John MacEnulty, the President of the Pressed Steel Car Company, in tank production and a five-year contract (renewable for up to 2 years) was signed on 23rd July 1940. Under the terms of this contract, Pressed Steel would gain exclusive rights to the production of tanks from A.T.C. (notwithstanding that a non-exclusive Belgian production license had already been signed). Under the terms of the contract, Pressed Steel would pay A.T.C. a royalty of $750 for each vehicle of A.T.C.’s design ordered for production by the US or Foreign Governments at Pressed Steel. A.T.C. was to provide plans, drawings, technical advice and, if required, a skilled engineer to assist in production.
On 25th October 1940. Pressed Steel entered into an agreement with the British Purchasing Commission for the production and delivery of 501 M3 Medium tanks. These were not tanks designed by A.T.C. but Bechhold did assist in the completion of the contract arrangement and the British sent an advance of US$500,000 to Pressed Steel. The next month, November 1940, Pressed Steel paid A.T.C. US$75,000 under the terms of the July 1940 contract with US$300,000 remaining to be paid.
It is not clear though why Pressed Steel paid this commission to A.T.C. as the vehicles being produced were Grant tanks and not the Christie-based tank design from A.T.C. Despite the huge sum paid to ATC, it was in trouble. Bechhold had finagled matters so that after October 1940, only he held all of the Class A shares in the company, and therefore had exclusive voting rights for A.T.C. He had also increased the number of shares available from 100 to 10,000 (3000 Class A and 7000 Class B) with a reduced value of just US$1 each.
The desperate need for tanks meant that the British were rapidly building their own in industries repurposed from civilian work to war work, but they were also looking for American production too, as this would not be affected by the manpower shortage in Britain or by German bombing. As well as the order for the M3 tanks from Pressed Steel, various other options were being considered and the work of the Purchasing Commission continued into 1941.
One particular type of vehicle that the British were interested in was an airborne tank,namely a tank which could accompany parachute or glider-borne troops. The lightweight and compact Bechhold tank was obviously of specific interest. On 27th February 1941, on behalf of the British committee in charge of evaluating tank designs, a telegram was sent to the Consul General in New York regarding the tank situation. The British were clear on what they needed from an airborne tank:
3 man crew
37 mm gun and .30 calibre Browning in a 360 degree rotating turret (quite why a 37 mm gun was specified in preference to the 2 pounder which was already an excellent gun and fielded on the A.17 Tetrarch is unknown but it is probably to do with the 37 mm being easier to produce in the USA)
Space for a wireless
Maximum Speed 40 mph (64 km/h)
Radius of Action 200 miles (320 km)
Armor basis ‘preferably’ 40-50 mm on the front and turret. 30 mm thick sides
Weight about 9 tons (9.1 tonnes) (anything under 9 tons was felt to lack the fighting qualities required) (for reference: the A.17 Tetrarch weighed just 7.6 tonnes)
“Not very interested in dropping Tank from a height of two feet”
In other words, the idea of dropping the tank from a plane was not wanted at all. Either it had to be landed directly (some various schemes for adding wings to tanks were considered), or it had to be unloaded from an aircraft. Dropping it from underneath a plane was, quite rightly, seen as a terrible idea. These requirements exceeded those of the Bechhold tank from A.T.C. That vehicle lacked the armor and firepower required and was inferior to the available A.17 Tetrarch when what was wanted by the British was basically a better armored version of the Tetrarch. The British were also anxious to get an airborne tank as soon as possible and were hoping for interest from the USA in manufacturing the vehicle. The Bechhold tank was, therefore, not suitable for their needs as it was noted that a pilot model had not yet been built.
By the end of March 1941, British plans for “the Bechold [sic: Bechhold] Project” were over. Having analyzed the tank, the British reported that: “The tank will not have the essential fighting qualities for the operations in view” and would also divert production from heavy bombers. The matter was left in the hands of American authorities to pursue and oversee its development. In its place came consideration of a 9-ton (9.1 tonnes) tank to be carried by towed glider. A final comment on the matter, from 30th April 1941, was that it had become clear to the British that the “American War Department feel they have no capacity to devote to the development of air-borne tanks”. As the decision was that Bechhold’s tanks should be overseen in America rather than from Britain it was decided that no action be taken on the Bechhold tanks.
The British had not been convinced by Bechhold’s salesmanship. They had, after all, already been down the Christie suspension vehicle route with the purchase of a Christie M.1931 which became the A.13E1 in 1936/7 and they had extensive experience with light Cruiser type tanks already. They also had plenty of small light tank designs including the A.17 Tetrarch. They had been clear on what they wanted but Bechhold was either unable or unwilling to comply, or simply could not produce a prototype, which was required before a decision could be taken. With the British unconvinced and an already lucrative deal with Pressed Steel in place, Bechhold had other plans.
Shenanigans and Taxes
In February 1941, A.T.C. sold its original Christie tank for just US$3,500, (Bechhold had bought it for US$5,000 in 1939) and on 18th August that year, A.T.C. incorporated as a corporation in Delaware to avoid payment of New York franchise taxes. This was completed on 20th August and the shares changed to just 100 Class A and 9,900 Class B shares with Bechhold, of course, retaining all the Class A shares and the voting rights that went with them (he also held 6,400 of the Class B shares too). Between 2nd and 4th September 1941, A.T.C. signed over all assets and the July 1940 contract (with Pressed Steel) to a newly incorporated body in Delaware, meaning the New York ATC effectively disappeared, although it was not formally dissolved until 11th September 1941. Mr. MacEnulty of Pressed Steel wrote to Bechhold on 4th September 1941 informing him that the July 1940 contract was now canceled due to alleged misrepresentations by Bechhold and a legal fight ensued.
Bechhold was insistent that he was owed money from Pressed Steel and, despite being offered US$300,000 (the remaining balance from the British Purchasing Commission contract), Bechhold refused due to the tax liability involved. His counter-offer was US$1.5m and this was immediately rejected. Instead, Pressed Steel suggested it should buy all of the remaining shares of ATC for US$50 per share (10,000 shares at US$50 would mean a US$500,000 payday). This would mean the end of Delaware A.T.C, which would have to surrender all its designs including an “aero” (airborne) tank concept, a full size model of the hook and release mechanism for releasing a tank from an airplane, designs of various other tanks and flamethrowers, and cash. This offer was considered and changed on 3rd October 1941 with a value of US$37.50 per share (US$375,000), but this would be only the existing July 1940 contract, no other plans or designs. This was agreed to by the voting members of Delaware A.T.C., which was just Bechhold, who of course approved of this arrangement.
In order to facilitate this transaction, the Delaware incorporated A.T.C. was changed from any mention or use of Armored Tank Corporation to the ‘Illinois Tank Corporation’ (I.T.C.) on 14th October 1941. On this day, just as Armored Tank Corporation (Delaware) was bought out by Pressed Steel and changed to Illinois Tank Corporation, Bechhold started a new company in Delaware. He called this new company the ‘Armored Tank Company’ once more receiving all of the assets from the original A.T.C., other than the contract, which had now gone to I.T.C. The next day, the new A.T.C. handed over all of its shares to I.T.C. which was then distributed to the stockholders, which also included Bechhold.
From these corporate shenanigans, Bechhold netted himself a cool 100 Class A shares (100% of the voting power), and 6,400 Class B shares valued at US$243,750 in total. This 15th October 1941 payment of US$375,000 (tax year 1941-1942) was to have serious consequences for Bechhold and his creative accounting.
Following this 15th October takeover though, the original July 1940 contract was finished. Bechhold probably felt he had made enough money and the entire business of the Illinois Tank Company was wound up suggesting that what assets in terms of tank designs it might have had leftover had little to no value. I.T.C. formally dissolved on 22nd November 1941.
The substantial pay-off which Bechhold had received was classed as personal income. He, and the other stakeholders, were found to be personally liable for taxes of this income. If there is one certainty greater than death and taxes, then it is taxation in time of war. Taken to court for non-payment of taxes, Armored Tank Corporation admitted an error in its tax liabilities and was assessed to be liable for the sum of US$390,144.91 (including US$78,028.98 in tax penalties on top of its original 80% tax liability of US$312,115.93).
This was not the end of it either, for the individual shareholders of the Armored Tank Corporation/Illinois Tank Corporation were also found personally liable for back taxes and penalties. Stockholders Philip Steckler and Hamilton Allen were found liable for US$33,750, and US$22,500 respectively, and Max and Siegfried Bechhold were found liable for US$243,750 and US$45,000 respectively. A massive combined penalty of US$735,144.91 (over US$12.8m in 2019 dollars) for not paying taxes on that US$375,000 (US$6.5m in 2019 dollars) income demonstrated the danger of trying to dodge taxes in wartime.
A.T.C. did not just produce a tank design. One of the more unusual things it designed and produced was a trailer for vehicles. This design appears in a letter dated 19th May 1942 from the Office of the Chief of Ordnance to the Commanding General of Aberdeen Proving Grounds (A.P.G.). Confusingly though, the product in question was produced by the ‘Armored Tank Corporation’ of Jersey City, New Jersey, suggesting that Bechhold kept working on designs incorporated in a different state. It is unlikely to be a mistake as A.T.C. (NY) had ended in September 1941 and I.T.C. (DE) ended November 1941. It is undoubtedly the same firm reborn, however, as the person providing information to A.P.G. on behalf of A.T.C. (NJ) was none other than ’Mr. Bechhold’ himself.
The proposal to the military was not this time a tank, but a trailer capable of being used for hauling supplies, equipment, or fuel. According to Mr. Bechhold, the British were interested in this trailer and the report recommended that APG experiment with it over a 250 mile (402 km) course to assess its viability, showing it off to the army and British representatives respectively.
This trailer was known as the ‘ROTA-TRAILER’ and the name stenciled on the side during trials stated this was the ‘Model 4’, suggesting the other 3 models or designs were less well refined. This Model 4 trailer consisted of two large hollow wheels fitted with a 40 inch (101.6cm) rubber tire 5 inches (12.7cm) wide. The wheels were unsprung but could hold up to 60 imperial gallons (272.8 liters) of fuel, either petrol or diesel, and were covered in rubber to provide a ‘self-sealing’ effect if the wheel hub were punctured by ammunition up to .50 caliber. Between the two wheels was a large rectangular cargo compartment made from ⅛” thick (3.175 mm) thick welded steel. This large space inside could be fitted with an ammunition rack for tank or artillery shells (34 rounds of 75 mm or 108 rounds of 37 mm), small arms ammunition boxes, ration boxes, water or fuel cans, or other items that were required. A second, smaller compartment below this was specifically designed to hold four boxes of .30 ammunition.
At the back of the trailer lay a third compartment, smaller than the first, and which contained a hand-operated fuel pump and supply hose long enough to feed the towing vehicle. Below this compartment lay a fourth compartment (just like the one at the front) which held stowage space for tools.
Overall, the trailer was very complex containing many bespoke parts that made for complicated maintenance. The doors to access the items inside were fitted with wing nuts (butterfly nuts) but were overly laborious to unscrew to access the contents. This is something that could easily have been rectified in a production model.
The Rota-Trailer not only had these internal compartments for stowage but also the ability to have a multitude of items carried on top. A special frame was fitted which held three 5-US gallon (18.9 liter) oil cans, and various tie-downs allowed other accessories such as nets or tarpaulins or other stores to be lashed to the top of the trailer.
Despite looking good on paper, capable of extending the fighting range of a tank, the trailer had serious problems. It was tested by an M4 Sherman and two different half-tracks over a 26 mile (42 km) cross country course and 250 miles (400 km) of gravel roads and, whilst it was on a flat surface, like a road, it worked well with little bouncing. The trailer was heavy too: each wheel weighed 400 lbs (180 kg) empty and 800 lbs (360 kg) when full in addition to the weight of the other material carried. The weight of the trailer placed additional strain on the drivetrain of the towing vehicle and, during rough travel off-road, the stress and strain on the trailer risked serious damage. On top of this, the trailer reduced the maximum speed of the vehicle towing it because the instability of the load caused by the sloshing liquid in the wheels threatened to result in sideways skids at high speeds.
Even as it was, the semi-rough terrain traversed ended up with all of the cans of water inside or on top of the trailer becoming deformed and leaky but the trailer did at least provide self-floatation in mud due to the width of the fuel cells. Another downside was that the lower front compartment, just 8.75 inches (222 mm) from the ground had a tendency to become filled with mud which was forced into it.
A final problem with the trailer was that it made reversing more difficult. During testing with an M4, the trailer skewed to one side and the stress caused damage to the towing arm and the tank tracks rubbing against the trailer body.
Overall, the tests of this A.T.C. product were a failure and the vehicle was not recommended for use. Its main faults were:
Difficult to reverse
Additional strain on the drivetrain of the towing vehicle
Reduces maximum possible speed of the towing vehicle
Too heavy to move easily by hand
Too little ground clearance
Steel body is not resistant to small arms fire
None of these faults were to stop further ideas, designs, and experimentation with trailers for hauling fuel or stores by tanks, but the work from A.T.C. (NJ) on this matter was effectively dead. No more is known of A.T.C. after this time; possibly Bechhold’s resources had simply run out and this venture failed, although it is noteworthy that on 1st February 1943, despite the failings of the Rotatrailer, the British still ordered 600 of them anyway, although how many were finished or delivered is less clear.
In the Army
Siegfried Bechhold, aged 42, in October 1942 joined his second Army. His first was a German one in WW1, his second, an American one in WW2. He served as a private being sent to Camp Lee in Virginia. He is not believed to have been sent overseas.
Re-born once more?
The back end of the hull of the Bechhold Tank seen in the November/December 1940 advert is very similar to the vehicle shown to the US Army Ordnance Department in May 1942 known as the Bigley Gun Motor Carriage suggesting a possible link to that vehicle. Was, in fact, the Bigley GMC the M.1938 High-Speed tank from Christie, bought and modified by A.T.C. and then sold off, redeveloped and re-submitted by another firm? Or is it in fact the other Christie tank, the M.1937 sold off by his creditors to Mr. Bechhold. On the balance of the evidence, the former case appears to be correct.
By the end of WW2, Bechhold had left the field of tanks and the complications of military work. By 1948, he was living in Florida where he headed the Ribbonwriter Corporation of America, selling parts for typewriters. Siegfried Bechhold died in California in 1956.
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The Light Tank T3, made in the late 1930s, occupies a period of time in US tank development history best described not so much as a dark age but more of a grey age. Lots of failed and somewhat obscure ‘T’ number designs were being developed to fulfill an unclear and poorly considered set of strategic goals at a time when an isolationist America was unprepared to wage a modern war.
This relatively unknown and obsolete-before-it-was-even-finished tank is remarkable only for its unremarkableness, and that it was inferior in almost every way to tanks of other nations such as Italy, whose 2-man turretless light tanks were also identified as having serious failings in combat. Perhaps, the only thing to distinguish the Light Tank T3 is that it marks one small step in the process of development which eventually led to one of the most successful light tanks of WW2, the Stuart.
The US Light Tank T3 started life in 1936 as an idea by Rock Island Arsenal (RIA) to produce a tank lighter than the Light Tank T2, which was due to go into mass production that fiscal year. At this time, weight was king. The US Secretary of State for War had decreed in the Spring of 1933 that 7.5 US tons (6.8 tonnes) was the maximum weight allowable for a light tank, so the goal was to keep the weight as low as possible. RIA had already dropped the British Vickers 6-ton-style suspension in favor of a double-wheel volute spring bogie from the Combat Car T5 for the Light Tank T2 in 1934. Thus, the suspension which was to form the basis of numerous American designs for the next several years had already been selected when the Light Tank T3 came along. With an attempt to be less than half the fully laden weight of the already light Light Tank T2 (weighing just 7.5 US tons to 9.7 US tons/6.8 to 8.8 tonnes depending on the variant), severe design compromises would have to be made.
The most obvious of these changes was the removal of the turret, followed by a significant overall reduction in size and the switch to a crew of just two instead of four on the Light Tank T2. The two crew were simply the driver on the front left of the hull, and the commander on the front right. The commander also had to operate the sole armament. In an effort to further reduce weight, some aluminum components were also used inside. Finished in March 1936, the vehicle was shipped to Aberdeen Proving Ground (APG) in Maryland in April that year. Here, on 23rd April, the Light Tank T3 was unveiled for comparative testing with the pilot model Combat Car T5 (a tank in all but name).
The Light Tank T3 was powered by a single V8 Ford car engine. Capable of delivering 83 hp at 3,800 rpm, with differential steering and a 4-speed transmission, the Light Tank T3 could manage a credible 35 mph (56 km/h) on a road.
This Ford V8 was later replaced with a Menasco air-cooled engine and as such was renamed Light Tank T3E1.
The Light Tank T3 used a pair of dual-wheel bogies with rubber volute springs of a very similar style fitted to a whole generation of US tanks in WW2. These volute spring units, however, were the result of comparative testing with an experimental rubber torsion suspension. Details on what that suspension actually looked like are unclear but it is known that it failed repeatedly during testing and would need redesigning to be usable. It was not and was abandoned. When the Light Tank T3 was upgraded with a Menasco engine as the Light Tank T3E1, the volute springs were finally selected as the preferred suspension.
The Light Tank T3 was very poorly armed, just a single .30 caliber (7.62 mm) machine gun located in the front right of the hull. Mounted in a ball, the range of motion was acceptable but still ultimately as limited as other vehicles such as the Italian CV.3, it faced forwards so could not fire to the sides or rear.
As might be imagined in such a small and light vehicle, the armor was woeful. No part of the Light Tank T3 was thicker than ⅜” (9.5 mm), with most of the armor being just 3/16” (4.8 mm) thick, enough to protect against small arms from the front but vulnerable to even a burst from a machine gun or shot from an anti-tank rifle. With such poor armor, it is no surprise that an idea was floated to increase the armor thickness to an unspecified value in another variant known as the Light Tank T3E2, with the issuing of the tank to the National Guard in mind. This was never completed and the Light Tank T3E2 was never built. There was also a T3E3 version that got as far as a study but it is not known exactly what the study was about and whether it was armor or automotive related or something else.
T3E1: upgraded T3 with a Menasco engine. 1 converted.
T3E2: T3 project with increased armor. None built.
T3E3: unknown study project
When the Light Tank T3E1 was abandoned, it was not wasted. Instead, the remaining vehicle was stripped of its armament and converted into an experimental tracked carrier named the Cross-Country Carrier T5. The sole contribution of the Light Tank T3 is perhaps to show the futility of a two-man tank armed with just a single machine gun. The cost of the vehicle and the poor combat potential meant that, despite moderately good mobility, it was still a failure. Of the variants attempted, the Light Tank T3E1 was at least an improvement with a better engine but the E2 with more armor was dropped before it began. The Light Tank Tank T3E3 got as far as a design study but how far and quite what they were even trying to study is not clear. The concept was a dead end. The vehicle was converted to a tracked utility carrier and quite rightly consigned to the dustbin of US tank design.
11.25’ x 6.75’ x 4.5’ (3.43 x 2.06 x 1.37 m)
3.54 US tons / (3.21 tonnes)
2 (Commander/gunner, and driver/radio operator)
Ford V8 Petrol (T3), Menasco air-cooled (T3E1)
35 mph (56 km/h)
1 x .30 caliber machine gun
¼” to ⅜” (6.35 to 9.53 mm) (T3), slightly heavier armor (T3E2)
When the US joined the war in 1941, their primary light tank was the M3 Stuart and, while this vehicle was acceptable for that time, there was an interest in a new light tank. In January 1941, the US Army started the T7 Light Tank program, however, by August 6th, 1942, this tank had grown in weight and size and was now reclassified as the M7 Medium Tank. With no replacement for the Light Tank M3 in progress, the T21 Light Tank project was started.
With the need for a new light tank, representatives of the Ordnance Department and the Armored Force held a conference at Fort Knox on August 18th, 1942. where it was decided that they should use the new T20 medium tank as a basis for the light tank. It would mount the M3 75 mm gun and feature armor capable of holding up against .50 caliber rounds while being within a 20-ton limit. It was decided that, if possible, the M3 75 mm gun would be replaced with a 76 mm higher velocity gun. It was proposed that it could use the Medium Tank M7’s suspension.
Following this conference and additional studies, an Ordinance Committee Minutes (OCM) was issued in February 1943 detailing the new light tank. It would have a crew of 5, mount a stabilized 76 mm gun, and would have a top speed of 45 mph (72 km/h). However, at this stage, the engine, suspension, and various other aspects were not finalized and its weight had been increased to 47,000 lbs (21,300 kg) or 21 long tons. Final layout drawings were finished during March and submitted. By this time the weight had been increased to 51,000 lbs (23,100 kg) or 22.8 long tons, with the new top speed being intended as 50 mph (80 km/h).
There was also a second variant which existed for a short time called the T21E1. This variant was to weigh 22 tons, later increased to 23 tons, and would have thicker armor than the normal T21 while being able to manage 50 mph (80 km/h). It seems likely that the T21E1 program was accepted as the new T21, as later sheets state the T21 as having almost the same figures as the T21E1.
The initial armor for this tank was designed to only resist .50 caliber fire, being 1 1/8th inch (2.85 cm) on the hull’s front and 1.5 inches (3.81 cm) on the turret face. The hull’s side and rear armor was 1 inch (2.5 cm) and 3/4th (1.9 cm) of an inch, respectively, the turret’s side and rear armor were 1 1/8th inch (2.85 cm). At a later point, the armor on the T21 increased to be the same armor basis as on the M5 Stuart. The T21E1 project was to have the same armor as the M5 Stuart as well.
The T21 was to mount the 76 mm M1E1 or M1E2 gun – the primary difference between these 2 guns being that one had a tighter rifling twist rate than the other. The rounds used by that gun included M62 Armor Piercing Capped (APC) and M79 Armor Piercing (AP), additional rounds including High Explosive and White Phosphorus. The gun was to have elevation and depression limits of +25 and -10 degrees respectively, as well as being gyro-stabilized. It also was to mount two .30 caliber machine guns, one co-axially to the main gun and another in a bow mount in the hull.
Suspension and Tracks
While it was initially proposed in August 1942 to use the M7 Medium Tanks Vertical Volute Spring Suspension or VVSS, it was later decided to utilize torsion bar suspension instead. The tracks that were intended for it were the 18 inch T49 type. Whilst the exact layout is unknown, the T21 would have had, it can be assumed that due to it being just a lighter T20, it would have been the same or very similar as on the T20E3. The T20E3’s suspension had a torsion bar and initially had 3 track return rollers per side, however later on, 2 additional ones were added, bringing the total to 5 per side. an idler wheel was attached to the front wheel to compensate for slack in the track.
Engine and Transmission
The engine for both the T21 and T21E1 was to be the Ford GAN, which produced 500 bhp at 2600 RPM. The transmission for both was the same 5-speed manual transmission utilized in the M4A3. The location for the engine and transmission is unknown, but again, due to it being just a lighter T20, it is likely that it would have been in the same position as on the T20, in the rear of the tank.
In March 1943, the design and layout were presented at Fort Knox to the Armored Force. They came to the realization, from their experience with the M7 Medium Tank, that the T21’s weight would continue to increase in the future, resulting in another under-armored medium tank. They then suggested that the T21 project be terminated and Ordinance replied in July 1943 by killing the project. Up to this point, no mockup or pilot vehicles had even been started. The fate of the T21E1 is unknown, but it was almost certainly canceled along with the T21 if it was still in development at that time.
This design, like many before it, was a good idea on paper, but operational realities and desires soon lead to a situation where, like the M7 before, it was doomed to become too heavy to fulfill the light tank role and too light to fulfill the medium tank role. The discontinuation of the T21 program in March 1943 was met with the start of a new project, the T24, which would not be deployed until 1944, which in turn forced the US to continue having to field the M3 and M5 Stuarts up until the end of the war, despite their growing inferiority.
T21 Light Tank Specifications
5.76 m x 2.98 m x 2.48 m
Total weight, battle ready
20.98 tons (47,000lbs gross)(21.31 tonnes)
Five (Driver, Co-Driver, Commander, Gunner, Loader)
45mph (72kph) on road
25mph(40kph) on 3% grade
12mph(19kph) on 10% grade
1150 miles at 25mph (40kph) on roads
Gyro Stabilized 76mm M1E1 or M1E2 gun with 70 rounds
Two .30 Browning M1919 machine guns with 6000 rounds
Lt. Colonel Gladeon M. Barnes from the US Army’s Ordnance Department casts a long shadow over tank development in the USA in the period around the start of WW2. Barnes was an interesting man, but some of his ideas and designs were demonstrative of a disconnect between his thinking and military reality.
One such example came in 1938 with the idea for a small heavy tank armed with a single machine gun. Quite what role such a vehicle was meant to fulfill is hard to imagine years after other users of such vehicles had already accepted the serious inherent limitations of a similar type of vehicle.
Somewhat oddly, the inspiration for this idea came from the Spanish Civil War. Section G-2 (the department responsible for Intelligence in the US Army) examined that conflict for lessons in a report titled ‘Tank Lessons from the Spanish Civil War’. They concluded that tanks were too poorly armored, used in too few numbers, and that they were not maneuverable enough.
In that war, the primary tanks being used were the German-supplied Panzer I, the Italian CV.3 series light tank, and the Soviet-supplied T-26 light tank. During that war, as G-2 correctly pointed out, tanks tended to be used in small numbers or alone and both the CV.3 series and T-26 had thin armor, around 14 to 15 mm maximum, meaning both were just bulletproof.
The T-26 had an advantage over the CV.3 in the addition of a turret-mounted weapon, whilst the CV.3 was stuck with its only armament in a mounting on the front left of the hull facing forwards. Neither tank was able to demonstrate much speed even though the CV.3 was faster, just under 30 miles per hour (48 km/h) compared to just under 20 miles per hour (32 km/h) for the T-26, although the overall effect was slight. Both tanks were too slow, both suffered from narrow tracks and a relatively underpowered engine. Any reasonable and objective assessment of the use of tanks in the Spanish Civil War would reflect this.
The Italians, for example, understood from the conflict the severe limitations of the CV.3 for tank vs tank combat and undertook work on turreted light tanks with some urgency. The Germans and Soviets likewise looked and learned. Why then did the US see a solution lying in a vehicle with the same sort of layout as the CV.3 but with less armament is difficult to comprehend.
Barnes’ concept was for a small light tank, just 7 US tons (6.35 tonnes) or so and just 11 feet (3.35 m) long. For reference, the Italian CV.3 was less than half the weight, shorter, narrower, and lower, and the Soviet T-26 was heavier and slightly longer, wider, and taller.
With a crew of just two, both men would have their work cut out for them. One man had to drive the tank and operate its radio, almost certainly sat on the left just like on the Light Tank T3. The other crew member would have to both command the tank and operate the armament and would sit on the right, alongside the other man. This is a very similar arrangement to the Italian CV.3, except the crew position/roles were reversed. It could be considered that these reductions in size and capability were, in fact, simply the means to get the most tank possible for the least money. However, here Barnes trips-up once more. He provided a cost estimate of US$20,000. In 1938, US$20,000 was a huge sum of money, equivalent to over US$350,000 in 2020 values, or roughly half the cost of a far more potent and useful Sherman tank.
Comparison between Barnes’ design and the primary Spanish Civil War Tanks
The 2-man heavy
1 x 37 mm / 1 x .30 cal MG
2 x 7.92 mm machine guns
2 x 6 mm machine guns
1 x 45 mm & 1 x 7.62 mm MG
L / W / H
11’ x 6.5’ x 4.5’
(3.35m x 1.98m x 1.37m)
4.02 x 2.06 x 1.72
3.03 x 1.4 x 1.2
4.65 x 2.44 x 2.24
7 tons (US)
(off road/on road)
20 mph / 35 mph
(32 km/h / 56 km/h)
25 km/h / 37 km/h
F / S / R
7 – 13 mm
14 / 8 / 8
15 / 15 / 15
The drawing of Barnes’ vehicle shows a single machine gun and the annotation states this to be a single .30 caliber (7.62 mm) weapon with 60 degrees of traverse, presumably 30 degrees to each side. An alternative armament was also proposed, a 37 mm gun. Once more, this was to be mounted in the front, seriously limiting its potential effectiveness. On top of this failing, operating a gun is a lot of work to load, aim and fire and, perhaps because of this, Barnes did propose that it could be automatically fed. Thus, the commander would have to ‘only’ command the tank, aim and fire the gun. Even so, the tank, limited by the traverse of its gun, would still be inferior to the Soviet T-26.
If the CV.3 and T-26 were unsuitable, with armor only 15 mm at most, then the goal would be to have more, presumably to make the tank protected against automatic cannon fire such as the potent 20 mm Breda cannon which was a proven armor-killer in Spain. It would also mean anti-tank rifles would be less useful against tanks, so more armor was not an unreasonable goal. Barnes wanted up to 1.5 inches (38 mm) of armor on this small heavy tank. For the purposes of reference, the Czech LT vz. 35 (better known as the Panzer 35(t) in German service in WW2), a tank which is possibly the preeminent and most modern turreted tank of the era, had just 25 mm across the whole front. What Barnes was indeed proposing was a tank the size of the diminutive American Light Tank T3, a little larger than the Italian CV.3 light tank, but with armor heavier than most of the tanks then in European service. All that, just to carry a single and rather limited machine gun, a task the even smaller CV.3 did more effectively with two machine guns mounted together.
The speed and agility of the vehicles in the Spanish Civil War were seen as a failure because they were insufficient. Therefore, Barnes should have been looking for a vehicle able to exceed the speed of the CV.3. Instead, he managed to make a vehicle which even under ideal circumstances was larger, heavier, and slower.
The power to weight ratio of this design was to be 20 to 25 horsepower per ton and, with an estimated 7-ton (6.35 tonnes) weight, that would mean an engine of 140 to 175 hp. Ideally, this would mean a top speed of 20 mph (32 km/h) on a slight slope and 35 mph (56 km/h) on a road. On paper, this all sounded good, but paper-designs are like that and a magic engine can be produced from thin air with imaginary performance. When the design meets reality, things change and this is exemplified by the Light Tank T3.
Although Barnes did not specify which engine was going to be used, the Light Tank T3, produced two years earlier in 1936 gives a good idea of the problems. Both vehicles clearly use a pair of volute-sprung bogies, each with two wheels and a front-mounted drive sprocket meaning the transmission was in the front. The Light Tank T3 is very similar in size, suspensions, armament, and appearance to Barnes’ idea and was fitted with a 221 cubic inch (3.62 litre) Ford V-8 engine. Despite being slightly over 3.54 US tons (3.21 tonnes), this vehicle had half of the armor Barnes was proposing and yet had the same top speed. The Light Tank T3 was the same size as Barnes’ idea, with half the armor and half the weight, and yet the same desired performance meaning whatever engine Barnes was considering would have to be significantly more powerful and yet fit in the same space as available in the T3. This was no small order, although the Combat Car T5 of 1933 had managed to cram a 235 hp air-cooled Continental R-670 radial petrol engine inside, all for 6.29 US tons (5.71 tonnes), albeit with armor around just ½” to ⅝” thick (12.7 to 16 mm).
The closest vehicle, perhaps to Barnes’ idea, was not the Light Tank T3, but the Light Tank T6. Built in 1939, one year after Barnes’s 1938 concept, the Light Tank T6 departed from the suspension of the Light Tank T3, using just a single 2-wheel bogey with a volute spring and the large on-ground trailing wheel at the back along with a separately sprung half-bogey. Once more, the driver was to be on the left in another two-man tank but this vehicle was not armed at all. With armor up to 1” (25 mm) thick and weighing in at 9.75 US tons (8.85 tonnes), the Light Tank T6 was roughly the same size and gives a good idea of a potential power plant for Barnes’s tank, namely a pair of 8-cylinder Buick petrol engines. However, even so, it was more than 2 tons heavier and still had armor no thicker than 1” (25 mm) and, importantly, no armament. Comparing Barnes’ idea to both Light Tanks T3 and T6 shows how unrealistic it really was.
Comparison between Barnes’ design and the Light Tanks T3 and T6
Light Tank T3
The 2-man heavy
Light Tank T6
1 x .30 cal MG
1 x 37 mm / 1 x .30 cal MG
L / W / H
11.25’ x 6.75’ x 4.5’
(3.43m x 2.06m x 1.37m)
11’ x 6.5’ x 4.5’
(3.35m x 1.98m x 1.37m
Approx. 11.25’ x 6.75’ x 4.5’
(3.43m x 2.06m x 1.37m)
3.54 tons (US)
7 tons (US)
9.75 tons (US)
Ford V8 Petrol
Twin Buick 8-cylinder Petrol
(off road / on road)
? mph / 35 mph
(? km/h / 56 km/h)
20 mph / 35 mph
(32 km/h / 56 km/h)
? mph / 30 mph
(? km/h / 48 km/h)
F / S / R
¼” to ⅜”
(6.35 to 9.53 mm)
⅜” to 1”
(9.53 to 25 mm)
It is hard to see any merit in Barnes’ idea. The armor certainly would have provided excellent protection from the relatively small caliber weapons then in service on a lot of tanks, but those were the previous generation. Against a 37 mm anti-tank gun, like the type used in numbers in Spain to good effect, even 38 mm of armor was not going to be much help, although it would certainly have made the little tank impervious to infantry which did not have access to a cannon. What then was Barnes’ really proposing? A small lightly armed and heavily armored tank may have some utility against infantry but, with the only armament in the front it would, as the Italians found to their cost, prove untenable. If, however, Barnes was really considering a small tank destroyer then why bother with the armor at all. Concealment and maneuverability would have been of far more use and he could reasonably have mounted the gun on top in an open-setting for a wider arc of fire and more space to carry ammunition.
Both ideas were also stymied by the selection of just two crew. There was simply too much for two men to do in combat, so a slightly larger chassis would also have allowed a third or fourth man to operate the gun, but would also have severely increased the weight and decreased the mobility.
Finally, Barnes’ concept of mobility was flawed. There was no way he was going to get even more armor and an automatic 37 mm anti-tank gun into a vehicle no bigger than the 9-ton Light Tank T6, along with a larger engine and still have the same performance. Likewise, he could not have allowed the weight to go over 7.5 tons (6.8 tonnes), as this was the limit set in 1933 by the Secretary of War for light tanks, suggesting a reason behind the ‘heavy’ part of the name, and that is before the eye-watering price-tag for the vehicle was considered.
Barnes 2-man Heavy Tank specifications
7 tons (6.35 tonnes).
2 (Commander/gunner, and driver/radio operator)
Type unknown, 140-175 hp desired
20 mph off-road / 35 mph on road (32 km/h / 56 km/h)
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.
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 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.
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.
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.
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.
At least 5 (Driver, Assistant Driver, Gunner, Two Loaders)
The G-3 Light Tank Destroyer was the product of the disorganized state of US tank design at the start of WW2. The United States of America formally declared war on Japan, one of the three main Axis powers, on 8th December 1941, following the attack of the US naval base at Pearl Harbor, Hawaii the day before. This was followed, on 11th December, by a declaration of war against Nazi Germany and Italy. The US had been selling arms to the United Kingdom for some time before this though and had started its own military build-up as well, increasing its army strength from just over ¼ million men in 1940 to nearly 1.5 million by the time of entering the war. Nonetheless, it would be some time before the American war machine was in full swing and it had squandered the honeymoon period from the war’s beginning in 1939 to do exactly the development work it needed to deliver an effective tank destroyer. The G-3 Light Tank Destroyer is emblematic of this failure by the US military as the design fails to accommodate the needs of the Army in a new era of tank warfare.
The Americans entered WW2 with a serious shortage of armor, just 8 battalions of tanks for the entire Army in 1940. The Army had been hamstrung by the determination that tanks were only there to support the infantry in tackling machine guns, leading to a lack of attention to the actual problems associated with knocking out enemy tanks with their own tanks. The speed of the German advance and destruction of the most powerful tank force in the world, France, in 1940 came as a further body blow to the US military, which realized it had a serious shortfall in capability to overcome. The US Army needed large numbers of powerful anti-tank guns quickly and this was a problem considering the main anti-tank weapon in service was the 37 mm towed gun which had only entered service in 1939. The Army, in fact, had not even started work on a dedicated anti-tank gun until 1936, and despite men like General McNair having pushed for mobile anti-tank battalions within Infantry Divisions, little had actually been done.
With little done in the run-up to declaring war and despite the bad news from France in 1940, it was not until April/May 1941 that General Marshall (Chief of Staff of the US Army) decided that a solution was needed to meet the shortfall in anti-tank capability. He instructed the Army’s G-3 Section, responsible for Operations and Training, with this task and, within G-3, this responsibility fell onto the shoulders of Lt. Col. Andrew Bruce. Specifically, Lt. Col. Bruce was tasked with dealing with “such unsolved problems as measures against armored force action”. This was the start of the tank destroyer branch and, at this time, nearly 6 months into the war, there were simply no vehicles for it. The most powerful gun on a tank at the time was mounted in the sponson of the M3 Medium Lee, the 75 mm M2 gun, a less than ideal solution.
G-3 quickly developed a list of requirements for a lightweight tracked vehicle. Fast and maneuverable, these vehicles were to be able to respond to actions where enemy tanks were encountered and then engage them. This required speed, but also a powerful gun. The one thing which was not a particular need was armor. Protection would be sacrificed to the need to bring a gun to the battle faster.
The Fast Tank
How do you get a tank to go quickly? – by taking away all unnecessary weight, such as all but the bare minimum of armor, just bulletproof would have to suffice. The turret could also go if necessary, saving a lot of weight directly, as it would not need turret traverse motors or a turret ring, but also indirectly as the gun could use mounts in the hull and be substantially lower, meaning a smaller vehicle. Maneuverability also meant the vehicle would need a powerful engine, and all of this would have to be carried on a suspension system capable of traveling quickly over rough ground. In 1940/41, there was a clear leader in this regard in the US, the ‘Christie’ system.
The essential elements of the Christie-type system relied upon large diameter wheels carried on a short arm connected to a large coil spring. It was already in extensive use by the British on their Cruiser tanks and by the Soviets on the BT series of tanks. The US, however, had said no. They had already closely examined and rejected the Christie design several years beforehand in favor of volute springs.
Volute springs had two large advantages over the Christie system. Firstly, they were more compact, and secondly, they removed the need to deal with the obnoxious Mr. Christie. So bad, in fact, was Christie’s reputation within US armor circles that, despite his designs having several advantageous features, the Army simply would not consider the vehicles. This attitude persisted even after Christie had divested himself of his designs, selling the rights off to a man named Bechold, who, in turn, would later sell them on to a man named Bigley. Both of those men (Bechold and Bigley) would learn the sting that Christie’s work carried with it and found no success either.
This need for a fast tank-destroyer though, meant a re-appraisal of the Christie system was needed regardless of the previous history between the establishment and the man. The volute-spring system worked but was simply not capable of dealing with the speeds that G-3 wanted. What this meant was that, by December 1941, G-3, through Lt. Col. Tharp, a G-3 General Staff Officer and strong advocate for the Christie-suspension tank destroyer concept, had managed to gain a small amount of interest in it, sending G-4 (responsible for supplies) their recommendation.
This recommendation was for a fast tank using Christie-suspension and carrying a 37 mm anti-tank gun. That vehicle would see development on the old Christie tank chassis owned by William Bigley. By the start of 1942, Tharp’s pressure had led G-3 to develop their own ideas for a fast tank-destroyer based on the now ‘Bigley’ chassis.
With the US entry into the war, the development of armored fighting vehicles required coordination and, to this end, a board was set up to manage things. This board, known as the Armored Vehicle Board (A.V.B) was chaired by Brigadier General William Palmer and often simply referred to as the ‘Palmer Board’. By October/December 1942, the Palmer Board was considering 15 different designs for tank destroyers, amongst them this design using the Bigley chassis. Of note is that one of the competing designs was what became the T49 from Buick.
No engine is mentioned on the plans. It may be assumed that the engine inside was the same one that had originally been used in the Christie design, the 750 hp Hispano Suiza V12. With this engine the tank could, in theory, manage up to 60 mph (97 km/h) fully laden on a good road, although this would be lower off-road and also a dangerous and impractical speed to consider ‘the norm’. Nonetheless, the speed of the Christie design was undeniable and would likely be reflected within the thinking behind this G-3 concept.
The initial recommendation was to use the standard Army 37 mm anti-tank gun, but by the time the development work had begun on the Bigley chassis, the move towards a bigger gun was already underway.
By way of illustration, one of the rival designs, which went through a series of substantial changes, ended up as the T42. Even that vehicle did not meet requirements and was then redesigned once more (and redesignated as T49) by April 1942. When it did so, it was being considered for it to mount an American-made British 57 mm gun (6 pounder) instead of the original 37 mm gun considered suitable for anti-tank warfare at the start of the process. That decision was followed in July 1942 by the selection of an American 75 mm gun instead for the T49, ready for assessment in October/December that year. The T49 was later redesignated as T67.
As a turreted vehicle, the T42 (T49) mounting a 6 pounder or 75 mm gun was substantially more effective than the 37 mm proposed on the Bigley chassis and the result was obvious. The Bigley idea was shelved and the only known remaining drawing of the vehicle concept clearly shows it with a small-caliber gun. Whether the armament planned for the T42 was being mirrored by ideas to uparm the Bigley to match it is simply not known. If it was not changed, then it can be speculated that the Bigley tank-destroyer idea was dead sometime in the middle of 1942, when there was the switch to the British 6-pounder. Indeed, this would match with the death of the parallel idea, that of utilizing the Christie suspension taken from the Combat Car T4 to re-equip the T9 Light Tank chassis during the development of the 37 mm-armed GMC T42 in April 1942. That, in turn, had led to an unsuccessful Christie trailing-arm suspension concept for the first pilot model T49, although that too was dead by October, along with a myriad of other proposals to fill this fast tank destroyer role.
Even if heavier armament options had been considered for this G-3 concept, all hope for the Bigley was definitely over by the end of 1942 with the approval of the far more capable T49 platform. And, if any doubt remained, the selection of a 75 mm gun as the weapon of choice in January 1943 for the project put the final nail in the coffin.
With all of the talk of Christie, Bechold, G-3, and Bigley, it is understandable how hard it is to keep track of what the actual name of the vehicle was. If that is not hard enough, the book ‘Steel Steeds Christie’ by Walter Christie’s son J. Edward Christie makes the matter worse. Here, a suspiciously similar tank using the hull shape of the tank (albeit with 5 return rollers) is being referred to as the ‘M-1943 Christie Tank’ and also as the ‘M-1950’, which is recorded in US Archives as the Bigley Motor Carriage when it had the 4 large road wheels.
Comparing the vehicles it is clear that they share several common features such as the lines of the hull indicating a connection between the designs. However, the caption on the G-3 drawing shows Christie’s level of involvement with the name sticking with the suspension rather than the designer of this vehicle per se, despite the efforts of J. Edward Christie to postscript claim the design as his own.
A real question mark though has to be considered as to what the final G-3 proposal was even to look like. Clearly, the suspension is the same type of angled ‘Christie’ units with a wheel on an arm controlled by an angled cylinder with a spring. Undoubtedly, this was a very good suspension system but was not without its faults either. Primarily, the problem with the suspension was that the springs took up valuable width on the vehicle. Four of the wheels, each relatively small, were on these arms and a fifth wheel at the back was attached in the reverse-position to the same axis as the drive sprocket. On top of this was a second balanced arm connected to the rearmost return roller which also served to feed the track at the correct angle to the drive sprocket whilst simultaneously pushing up on the track to keep it tight.
One additional note on the return rollers is that the lead-most roller is also drawn as if it was meant to be able to move. There is no springing or return arrangement for it to move back into its original position but a sprung return roller would also assist in keeping the track tight. The mechanism by which it was to do this is, however, not clear.
The sprocket too was a Christie-design leftover. This was not the normal kind of tank sprocket with a toothed wheel pulling a track around via gaps in the end connector of the track plates. This was actually patented by Christie in January 1937 in conjunction with Morris Commercial Cars of Birmingham, England and used a series of rollers mounted on a sprocket. These would draw the track by means of the central guides on the track plates and also move with them as the track is drawn over them to reduce wear.
A further arm was fitted to the front of the tank and appears to be connected to a short arm connected to a central pivot about which the arm could rotate. On each end of this arm was a bearing with a roadwheel. This arrangement was clearly sprung, but only on the top part of the arm. The spring was yet another of the cylindrical springs and was angled back just as sharply as the other ones. This arrangement was perhaps best considered to be in the manner of a see-saw (teeter-totter) where, as one side moves up or down, the arm rotates and the other side moves in the other direction. Balanced by a coil-spring to the top part of this arrangement it meant that regardless of the position of the arm and wheels relative to each other, that they would remain in contact with the track and help keep it taut.
Left: The unusual and ingenious system of drive sprocket and double arms with one arm for a sprung road wheel, and the other for a sprung-tensioning return roller. Right: An angular sprung cylinder suspension unit for a road wheel. Source: Steel Steeds Christie
The roller-type drive sprocket and track plates designed by christie. Source: UK Patent GB474714 of January 1937
The basic hull shape was the same as the original Christie machine, that much is clear but the rest is not. The drawing from G-3 clearly shows some kind of superstructure on top. The superstructure would certainly increase the profile of the vehicle, but it doesn’t appear to be part of the actual tank itself. Instead, this frame appears to be part of a gantry system as used to attach the tank slung underneath or drawn up inside an aircraft, a particularly favorite pastime of Christie to suggest.
The small size of the wheels and the spacing between them would seem to indicate this was going to be a very light vehicle too, with the engine and transmission in the rear. Crew-wise there is little information other than that which can be inferred from the design. In the raised section on the hull, there was originally just a small raised cupola from which the commander/driver could observe the surroundings. There would also be space for a second man, presumably to operate the gun. There would still be sufficient space, albeit maybe not very comfortable considering ammunition storage and the breech of the gun, for another crew member, meaning a crew of 2 to 3 men.
Like all of Christie’s designs, armor was secondary to speed. In fact, for Christie, almost everything was secondary for speed. His designs were either bulletproof or barely bulletproof. In its original form, before being sold off to Mr. Bechold, the hull is reported to have been just ¼ (6.35 mm) to ½” (12.7 mm) thick. Speed, not armor, was to be the protection for the G-3 Tank Destroyer if it kept the same armor values.
It is not hard to see why this G-3 concept failed. It was not a future-looking design but a quick glance back to a past image of a tank in which the figure of Walter Christie loomed large. Undoubtedly, the Christie suspension was innovative with many desirable features but a barely-bulletproof, casemate-gun-mounting tank-destroyer armed with a 37 mm gun was hardly a reasonable competitor to a vehicle as capable as the T49 with a 75 mm gun. It would not be until July 1943 that the first actual descendants of this process, the M18 Hellcat started to roll off the production lines – the product of an unnecessarily long process started too late.
The Medium Tank M4A4 Sherman was an improved variant of the M4A3. The goal of the tank was to increase the speed of production of the M4 by using a new multibank engine and with a hull made from 5 pieces instead of seven. The longer and more complex engine would mean an increased length of track on the ground for improved performance of the M4A4 on soft ground, yet despite this, the M4A4 was not adopted by the US Army for use overseas. Early in the development of the M4A4, consideration was given to making us of the longer hull to improve the suspension. This led to the idea of using the ‘Christie’-style suspension from the T4 Medium Tank on this new Sherman. Whilst the M4A4 was built in large numbers and saw extensive service during World War 2 and later, the idea of using this ‘big-wheel’ suspension never left the drawing board.
The design of the M4A4 began in February 1942. This new Sherman was going to be more mobile than the M4A3 by using the 435 hp Chrysler A57 multibank petrol engine. The selection of what was actually 5 engines fitted together created a crowded space within the engine bay, which necessitated a slightly longer hull than the M4A3. This was considered a tradeoff that could add a large number of tank engines into the supply chain which would aid in meeting their production targets. Further, the hull of the M4A4 was simplified, as it was made in fewer parts than the M4A3 (5 instead of 7), and featured a 3-piece final drive housing on the front instead of the single-piece final drive housing on the M4A3. This would improve the speed of repairs and maintenance on the tank although, initially, the complex engine arrangement had been unreliable.
Lengthening the hull by 11 inches (279 mm) in order to accommodate the engine also meant that the suspension would have to be lengthened. The M4A3 had used three pairs of volute spring suspension (Vertically Volute Suspension System – VVSS) and these could be spread out more along the slightly longer sides of the M4A4 or a new suspension system could be considered instead. This prompted a very short study by Chrysler, the design agent for the M4A4, to try and improve the performance of the tank by way of an improved suspension system. The system to be investigated was a modified version of that trialled on the T4 Medium Tank.
Rather than refit the three VVSS units, spaced out along the side, the idea was now to use five large road wheels connected on horizontal crank arms. Springing for the wheels was delivered by means of vertical coil springs mounted on the outside of the lower hull. This has been described variously online as being a ‘Christie Sherman’ or ‘Christie suspension’ but it really is not. The Christie patent for his system had already been sold off by then as well as licensed off to countries like Great Britain and the Soviet Union. One of the dominant features of Christie’s suspension design was the suspension springs operated within a double-wall cavity along each side of the tank. This system was adopted and adapted for use in tanks such as the British A.13 and Soviet BT-5 and remained in use on some tanks through to the end of World War 2. The British Comet, for example, was the last British tank to use a version of this system. This was not the case for this M4A4. Here, the springs would be mounted externally.
Christie, by February 1942, was almost a dirty word in US armor circles and had no formal involvement with the US Army. His last official contact had been with the Ordnance Department in March 1939 and ended when he had stormed out of a meeting in a tantrum when his demand for large orders for his tanks was rejected. He had stomped off saying he would go and see President Roosevelt and with that had ended any prospect of formal consulting work.
Consequently, attributing his name to this design would be incorrect. If there is any doubt on the matter, the somewhat awful book ‘Steel Steeds Christie’ published in 1985 by his son Edward and which makes numerous fallacious claims, makes no claim to this design. The T4 suspension design was certainly based on the work of Christie, but the first conceptualized drawings for a sprung suspension-arm suspension for the M4, prepared by the Ordnance Office in February 1942, had already departed from this arrangement.
The T4 Medium Tank, built by Rock Island Arsenal in 1935 and 1936, weighed just 13.5 tons (12.2 tonnes). Different versions of the T4 were trialed between 1935 and 1940 when it was declared obsolete, but the key feature of the design was the four large road wheels on each side. The suspension of the T4 was certainly based on the suspension designs from Christie, but it did not use Christie’s patents. The track for the T4 was also a short-pitch type track 12 inches (305 mm) wide.
The T4 weighed just 13.5 tons (12.2 tonnes), whereas the M4A4 would weigh 34.9 tonnes (31.6 tonnes), more than double the weight of the T4, so using the same suspension required changes. The T4 used just 4 wheels on each side, which would be inadequate for the extra weight of the M4. Thanks to the longer hull of the M4A4 though, 5 of these large-diameter wheels could be fitted on each side. The second change came about after the initial drawings from the Ordnance Board. Those drawings had shown the five, closely positioned wheels, each mounted on an individual arm with a corresponding spring cylinder angled forwards. To meet the increased weight of the M4, these springs had to be changed too. The solution here was to adopt heavier coil springs and to mount these vertically along the outside of the lower hull of the tank under the sponsons.
The adoption of the T4 style wheels was also met with the choice of a wider version of the T4 track. This single-pin track was 18.5 inches (470 mm) wide, wider than the standard M4A4 track and the original T4 track, and used a center guide to prevent lateral slippage. With 93 track links per side (compared to 85 on the T4) and the larger, heavier wheel, this new M4A4 was significantly heavier than the original volute-suspension M4A4 by 3,080 pounds (1,397 kg).
The volute-suspension M4A4 used either the T48 or T51 83-link 16.56 inch (421 mm) wide track with a ground contact length of 160 inches (4,064 mm), which was substantially longer than the M4A3 at 147 inches (3,734 mm). Using this T4 style suspension, the track length on the ground was only fractionally longer than that of the M4A3, at just 148 inches (3,759 mm), yet despite this shorter length of track in contact with the ground than the volute-suspensioned M4A4, the wider track made up for this and kept ground pressure to just 14 psi (96.5 kPa).
With the new spring system fitted to the outside of the lower hull, this meant a lot of space was taken up under the sponson on each side. Consequently, the tracks and wheels would be further out than they would be if it had retained the VVSS system. This would have posed some additional issues regarding the transportation of the tank due to its increased width, about 450-470 mm wider than the M4A3 due to the projections of the track and the lack of space in which to add grousers to the inside of the track.
With the new spring system fitted to the outside of the lower hull, this meant a lot of space was taken up under the sponson on each side. Consequently, the tracks and wheels would be further out than they would be if it had retained the VVSS system. This would have posed some additional issues regarding the transportation of the tank due to its increased width, about 450-470 mm wider than the M4A3 due to the projections of the track and the lack of space in which to add grousers to the inside of the track.
One final note of difference between the suspension systems on the M4A4 are the return rollers. Easily overlooked, the VVSS system used a small return roller angled back from the suspension bogie which served to hold the track off from fouling on the top of the bogies. No such rollers were drawn on the T4 suspension units to support the track. The angle of the track, as it descended from the front sprocket to the rear idler, would likely contact the top of the last roadwheel but other than that it was unsupported .
Despite the fact that the T4-style suspension was found by engineers at Chrysler to be workable, it was not pursued. The volute system was not ideal but it was simple and reliable. In the short-term, the volute-spring system was retained, although work on improved suspension for the M4 continued. No versions of the Chrysler vertical coiled spring suspension M4 were ever built. Despite 7,499 M4A4s being built, it only saw limited service with the US Army anyway, restricted mainly to training duties. It did, however, find extensive use overseas particularly with the British, where it was known as the Sherman V.
Illustration of Chrysler’s improved suspension M4A4. Illustration by Andrei Kirushkin, funded by our Patreon Campaign.
6.06 m x 2.62 m (hull, 3.07 m to 3.09 m wide over tracks) x 2.74 m
Total weight, battle ready
72,780 pounds (36.29 US tons) (33 tonnes)
5 (commander, driver, co-driver, gunner and loader)
435 hp Chrysler A57 multibank petrol engine
35 mph (56 km/h)
M3 75 mm gun in M34 mounting
.50 calibre M2 AA machine gun
2 x .30 calibre M1919A4 machine guns
The U.S. Army did not prioritize addressing the need for heavily armored tanks until very late in World War II, when the losses of Allied armor were increasing due to enemy anti–tank guns. The M4A3E2, a makeshift assault tank developed from the M4A3 Sherman, was only produced as a stopgap measure until the T26E3 Pershing was available for reinforcement. Unfortunately, these heavy tanks were still not considered enough.
The T29 was developed to solve this problem. Armed with a long-barreled 105 mm T5E1 gun in a heavily armored turret, and weighing over 66 tons (60 tonnes), it was intended to directly engage with any opposition, from fortified bunkers to heavily armored tanks. Over a thousand were planned for production, with the first tank being completed in July 1945, too late to see action against Germany in Europe. The production would continue for a planned invasion of Japan, Operation Downfall, until its cancellation after the nuclear bombing of Hiroshima and Nagasaki, followed by the surrender of Japan, ending the war in Pacific.
Even after WWII, experiences gained from the war were carried over to the T29 and the design underwent numerous experiments for postwar development studies, which led to the production of the 120mm Gun Tank M103.
The development of a new heavy tank was first requested by the Chief of Research and Engineering of the Ordnance Department, General Gladeon M. Barnes, on 1 August 1944. He called General John B. Waldron, the Assistant Deputy Commissary of the Ordnance, about an Ordnance Committee Minute for a new heavy tank project. Gen. Waldron told Gen. Barnes that the project must be considered before such a vehicle could be passed for production. The inspection of the tank details took place at the Detroit Arsenal on the following day by the Ordnance Board and the Armored Center. It was expected that the new vehicle would be armed with a 105 mm cannon.
On 14 September 1944, OCM 25117C specified that, in order for a tank of greater firepower to be developed to meet potential operational requirements against fortifications and heavily armored enemy combat vehicles, it was considered imperative that the development of such a vehicle should be initiated immediately. Preliminary studies had been made for the installation of a 105 mm cannon in a tank with cross-drive transmission, torsion bar suspension and center-guided tracks, all powered by a 750 hp Ford petrol engine.
These studies had indicated the feasibility of this project. It was recommended:
That four pilot vehicles in general accordance with the characteristics outlined in this item be procured for test. Two to be fitted with 105 mm gun and two with 155 mm gun.
That the vehicles with the 105 mm gun be designated as Heavy Tank, T29.
That the vehicles with the 155 mm gun be designated as Heavy Tank, T30.
That these projects be considered confidential.
The first concept of the Heavy Tank T29 was initiated on 1 August 1944 with a proposal of what was essentially an enlarged T26 heavy tank sporting a 105 mm cannon. The initial specification was laid out with OCM 25117, suggesting a heavy tank weighing 54 tonnes and having an effective frontal armor thickness of 8.9 inches (228 mm), with a front hull armor of 5 inches (127 mm) angled at 46°. It also had a large mantlet covering the entire front turret, with 7.9 inches (203 mm) of armor backed with an internal armored plate. The turret design was to be made as simple as possible, with a 4 inch (102 mm) thick turret wall with nearly vertical inclination and streamlined. It was to have a stepped turret roof identical to that of the T26 turret, although it was noted to be a flaw in the protection due to the potential threat of deflecting projectiles. A large bulge was to be constructed at the rear of the turret to balance the turret assembly and the gun mount likewise.
The crew arrangement placed the commander on the right side of the turret, provided with a vision cupola. The gunner was in front of him, with the loader on the left side of the turret, provided with a single escape hatch. The driver and the co–driver were in the front hull. The armament consisted of a 105 mm T5 L/48 gun (a derivation of the prototype 105 mm T4 anti-aircraft gun intended for tank use), using stub fixed-type ammunition with just a single loader. A muzzle velocity of 2799 fps (853 m/s) for the armor-piercing round was expected. The main armament would have an elevation ranging from –10° to +20° and a .30 caliber (7.62 mm) Browning M1919A4 machine gun would be mounted coaxially. An anti-aircraft .50 caliber (12.7 mm) Browning M2HB heavy machine gun was also placed on top of the turret to be used by the loader. The tank would be powered by a Ford V12 petrol engine and a new cross–drive transmission developed by General Motors. The suspension used a similar approach to that of the T26, with torsion bars and center guided tracks.
However, the initial specification was revised a month later in favor of increasing firepower and a design overhaul. The front hull armor was switched to 4 inches (102 mm) angled at 54°, while maintaining the same effective armor thickness as previously. The general design of the turret received minor changes. The front plate of the turret remained the same but the rear bulge was increased in depth and reduced in thickness to 3 inches (76 mm). The 105 mm T5 L/48 gun was replaced with a much longer 105 mm T5E1 L/65, using large separated type ammunition. The turret now accommodated two loaders for the new shell loading type. The muzzle velocity was increased to 2,998 fps (914 m/s). A muzzle brake was developed for the new gun as a blast deflector, designed as an enlarged version of the 90 mm gun muzzle brake.
Contracts were awarded to the Pressed Steel Car Company for the construction of the tank and to Buick for the transmission development. The first pilot turret was to be mounted on the M6A2E1 in order to conduct trials in place of the T29. The second pilot turret assembly was being produced in February 1945 and expected to arrive in June. At the same time, a further design had been prepared and a new wooden mockup was built. The design received major alterations, with the turret wall now curved throughout the side to reduce the height of the turret. The roof plate was crested in the center to clear the gun breech and sloped down to either side of the turret walls to prevent shot deflection inside the turret. The actual weight of the turret was unchanged, and any weight savings were used to increase the armor protection. The thickness had been increased; 5.9 inches (158 mm) from the front to sides, tapering to 5 inches (127 mm) on the centerline of the turret, and 102 mm to the rear. The rear bulge of the turret was thickened again to 102 mm. The turret body was cast with the roof and the floor welded in position.
The gun mount was redesigned with the 105 mm T5E1 repositioned so that it would balance on its trunnions without the need for an equilibrator (although the installation of a muzzle brake would negate this). The recoil distance of the 105 mm gun was limited to 12 inches (305 mm) and regulated by three hydraulic cylinders located above the barrel. A recoil guard was fitted to the gun mount and extended from the gun cradle to the breech face. The single coaxial M1919A4 was replaced with two M2HB for increased firepower.
The main sight for the gunner was an M10E5 periscope with dual sights, 1x for a wide field of view, and 6x for high magnification, fitted with a reticle graduated for the 105 mm T5E1. An auxiliary telescope M70E2, a special M70 direct telescope lengthened by 15.7 inches (40 cm), occupied the vision port on the right side of the 105 mm gun with 3x magnification. An azimuth indicator was located on the gunner’s right. Elevation was controlled by means of a vertical handwheel and traverse by powered hydraulic control. An emergency hand traverse crank was also available. The gun traverse was equipped with a 5 hp power unit to drive the pump. The turret could be satisfactorily traversed either manually or by power traverse on a 30° slope. The power traverse system was designed to allow turret rotation at a speed of 3 rpm (18°/second). A full 360° turret rotation took 20 seconds. A gun traverse lock was located under the traverse pump and in front of the gunner, which consisted of a toothed segment that could be clamped into the traverse rack.
The primary firing controls consisted of an index finger trigger on the handle of the power traverse gear operating the main gun. A thumb button was provided to fire the coaxial machine guns. Secondary foot firing gear was also arranged beside the main one.
Separate ammunition was issued for the 105 mm T5E1. The shells would be derived from the ones for the 105 mm T4 gun, with the T12 HE and T13 APCBC–HE, weighing 38 pounds (17.2 kg) and 41 pounds (18.6 kg) respectively, with 33 pounds (15 kg) of propellant charge. 63 complete rounds were stowed and 46 of the projectiles were packed in bins inside the racks on either side of the commander. It was intended that the commander should pass these projectiles to the loaders. Nine charges were stowed in ready racks, 7 for the left loader and 2 for the right loader. The remaining ammunition was stored in the hull. Additional stowage for 23 boxes (110 rounds each) of .50 cal machine gun rounds was provided.
The turret crew was reshuffled to adapt with the second turret. The commander sat right behind the 105 mm gun, and the cupola was moved to the center rear of the turret. There were now two loaders stationed on both sides of the turret, provided with their respective escape hatches. The right loader had access to a pistol port to his side, and the left loader could use the .50 caliber machine gun mounted outside the tank. The gunner retained his original seat at the front right side of the turret, though now distanced away from the commander.
Two pilot tanks were being constructed by the Pressed Steel Car Company in March 1945. The T29 was planned for production with as many as 1,200 units, with 2 pilots to become available earlier for preliminary testing. Chevrolet worked on the turret and gun mount. Frankford Arsenal was given a directive for designing and manufacturing the fire control installations. The development of the engine and transmission would be undertaken by the Detroit Transmission Division of General Motors, whilst Buick inspected the final drive. Work on the T5E1 was temporarily suspended pending details of the new rounds and chamber design. In the redesign, provision for the subsequent scavenging device installation was being made.
The pilot turret received some modifications during production. The elevating gear was now anchored to the turret ring, whilst the box which contained the nut and screw elevation gear was mounted on the gun cradle. The main ventilation for the crew consisted of a 28.3 m3/min fan set to draw air from an inlet between the driver and co–driver. In addition, there was a blower fan with an inlet on the right side of the turret bulge, close to the deflector guard, intended to suck gun fumes and blow them out through a hole in the right rear of the turret. The ammunition arrangement was reallocated. 27 shells would be stowed in the right and 13 in the left of the turret bulge. The 9 ready racks were switched in position, with 7 shells on the right and 2 on the left side of the turret. The remaining shells and charges would be stored on the hull floor inside an armored rack. The whole complete ammunition load weighed about 2.2 tons (2.08 tonnes).
Due to the favorable results from variable power sighting telescopes and the request for the standardization of the T122 as the M83 telescope for issue to tanks and tank destroyers armed with high-velocity guns, a project was initiated to develop a bigger telescope designed for the T29. The substitute M70E2 telescope that was carried over from the M6A2E1 was replaced by the new scope, designated as T143E1.
The tank’s weight increased significantly from 59 ½ tons (54 tonnes) to almost 68 tons (62 tonnes). This crippled any common transportation methods, as there was no adequate bridge capable of supporting the T29. The widened Bailey–type triple–double panel bridge would carry the tank over a maximum span of 110 feet (33.5 m) width. However, this bridge was under procurement and none were ready in stock yet. Heavy floatation bridges and dry ferries for up to 79 tons (72 tonnes) of loading were undergoing development, and expected to arrive by the end of 1945 (OCM 26825). A new 30 inch (762 mm) wide steel track, designated T93, was being developed and expected to replace the T80E3 track currently used by the T29. A reason for this change was that T80E3 was an asymmetric type of track, a combination of T80E1 and Duckbill extended end connectors, and therefore, not considered sufficiently robust or reliable.
The new rounds in development for the T5E1 gun were designed to replace the substitute rounds of the T4 gun, including AP, HE, and APCR. The T32 was a solid APCBC projectile weighing 39 pounds (17.7 kg), capable of penetrating heavy armor at high obliquity. The shell design had been completed, and it was anticipated that the performance would surpass the earlier T13 round.
At the same time, work on improving the T13 progressed mainly in heat treatment, in which early batches of T13 shells were considered unsatisfactory. Newly redesigned shells with the improvements were the T13E1, T13E2, and T13E3. The T13E1 was tested and resulted in sufficient performance in both the design and the heat treatment against 102 mm and 127 mm face-hardened armor plates at 20°. The T13E2 had a thinner cap and was made from WD–9465 steel, and reported to be superior to the earlier T13E1 against face-hardened armor. The furthest of the T13 design, the T13E3, differed with a single radius on the projectile body and reduced diameter explosive cavity, was produced from WD–4370 steel. Aberdeen conducted tests with both T13E2 and T13E3 against various homogeneous and face-hardened plates for comparison, and concluded that the T13E2, with its better heat treatment, was still superior to the T13E3.
A new T30 HE shell was being designed to replace the T12 HE that originated from the 105 mm T4 ammunition, designed to work at both high velocity for achieving maximum range of attack and low velocity against hardened structures. High Velocity Armor–Piercing shot (HVAP) was the latest of the 105 mm weapon development, intended to create a more effective anti–armor ammunition than the regular AP shot. The shell designated as T29 consisted of a tungsten core contained in a magnesium body fitted with a steel bourrelet band, magnesium ballistic cap, and a steel base with copper driving band. Up to four designs were made; T29 (7.9 lbs/3.6 kg core), T29E1 (9.9 lbs/4.5 kg core), T29E2, (12 lbs/5.4 kg core), and T29E3 (9.9 lbs/4.5 kg core). The latter round was a redesign of the T29E1 that was 2.8 pounds (1.3 kg) lighter (estimated weight around 24 lbs/11.1 kg).
Procurement of the Heavy Tank T29 was reduced, from 1200 vehicles to 1152 in April, with the approval of production starting next year (OCM 27331). 6 pilots were planned for construction in total (OCM 27245). The first pilots of the T29 heavy tank hull and turret were being constructed in July and expected to be completed in the same month.
With the end of hostilities on the European front in May 1945, the production of T29s under the request from OCM 27331 was suspended as the heavily armored opposition that the T29 was designed to combat in Europe had already been defeated, leaving Japan as the sole threat. Amphibious operations against the Japanese forces were dangerous due to the coastal defense guns located inside heavy bunkers. The firepower of the 75 mm, 76 mm, and 90 mm cannons already available would not be able to damage their reinforced structures significantly. Seeking the advantages of using the 105 mm cannon of the heavy tank for this purpose, T29 resumed production in readiness for Operation Downfall, a planned large-scale invasion of Mainland Japan. Owing to the expectation of difficulty when traversing the mainland terrain with a tank weighing over 66 tons (60 tonnes), the development of the 30 inch (762 mm) wide T93 steel track was prioritized, although it was only on 1 July 1948 that the track would be completed and delivered to the T29 for testing. The track width had been reduced from the initial design to 24 inches (609.6 mm) during the development. It did not provide any substantial improvements over the asymmetric type T80E3 during the trials and the project was terminated in 3 September 1953.
The first T29 was finished in late July 1945 and located at General Motors’ Milford Proving Ground to provide data for the Detroit Transmission Division about its CD–850–1 cross–drive transmission. An equilibrator was installed to offset the added weight of the muzzle brake. The ammunition arrangement was redistributed again. 46 projectiles and 19 propellant charges would be stored in the turret, with the remaining ammunition stored in the hull. At the same time, the shell loadout for the T29 was standardized. Improved versions of the recently developed rounds would be made available for the gun to use; T32E1 APCBC, T29E3 HVAP, T30E1 HE, and a new burst–type white phosphorus smoke shell, designated as T46 WP.
After the end of the Pacific War, the production contract with Pressed Steel Car Company was terminated, with one pilot tank completed and a partially finished second pilot. All materials for the completion of 10 production tanks, including one partially finished pilot tank, were transferred to Detroit Arsenal for post-WWII development studies authorized by OCM 28848 on 23 August 1945. The first production T29 arrived at Aberdeen Proving Ground in October 1947. By this time, there was no longer any requirement for production of these heavy tanks and the test program was limited to evaluating the various power train components for application to new tank designs. Two additional T29s arrived in April and May 1948 for the endurance and engineering test programs. Ten tanks were built in total, two of which were the pilot vehicles built by Pressed Steel Car Company and eight were production tanks with the development continued by Detroit Arsenal. Some were modified independently to mount various experimental components such as new engine, fire control system, and stereoscopic rangefinder. This resulted in the development of T29E1, T29E2, and T29E3 heavy tanks that would test these new modifications.
The T29 project was discontinued in late 1950 in favor of a new heavy tank development based on the 120 mm cannon of the T34 in a new tank design, designated as T43 heavy tank, and standardized as 120 mm Gun Tank M103 in 1956.
The T29 was required to gain significant armor protection over the T26E3 Pershing. It was meant to be protected against the threat posed by the German high velocity cannons, notably the 8.8 cm Kw.K.43 high velocity cannon of the Tiger II. Basis armor thickness is the contemporary US term for what is today known as effective armor thickness. Necessary overhauls to both hull and turret protection were required beyond what the previous tank designs could offer, starting with 228 mm of basis armor requirement on the frontal projection.
The hull armor was a welded assembly of cast and rolled plates. The upper front glacis retained the 102 mm armor thickness from the Pershing, but with increased inclination to 54° to improve the basis armor thickness up to 228 mm, arranged with additional two rows of spare track links as a form of additional armor. A 7.62 mm machine gun port was stationed on the right side of the hull.
The lower front plate was 2.7 inches (70 mm) thick and angled at 58° at the center of the plate. The sides were split into two sections, 3 inches (76 mm) covering the fighting compartment and 51 mm covering the engine compartment toward the rear hull. The roof armor was .9 inches (25 mm) around the turret and half an inch (13 mm) above the engine deck.
Front, upper : 4 inches (102 mm) @ 54°
Front, lower : 2.7 inches (70 mm) @ 58°
Side, front : 3 inches (76 mm)
Side, rear : 2 inches (51 mm)
Rear : 2 inches (51 mm)
Roof, front : .9 inches (25 mm)
Roof, rear : ½ inch (13 mm)
Floor, front : .9 inches (25 mm)
Floor, rear : ½ inch (13 mm)
The variable armor thickness of the turret started at 6.2 inches (158 mm) at the front, tapering to 5 inches (127 mm) to the side of the loaders hatches, and 4 inches (102 mm) around the commander’s cupola and the rear of the turret. The turret roof armor consisted of 1.4 inches (38 mm) on the front and .9 inches (25 mm) on the rear.
A massive cast turret was welded on 78 inch (2 meter) wide turret ring and mounted a large gun mantlet at the front, covering a large portion of it. The thickness exceeded 8 inches (203 mm) on overall area, with up to 10 inches (254 mm) around the gun collar and 12 inches (305 mm) on the joints around the corner of the mantlet. An internal armored plate was attached to the gun mount as a secondary protection, forming the estimated 9 inches (228 mm) basis armor requirement on the frontal portion of the turret.
Mantlet : 8 – 12 inches (203 – 305 mm)
Front : 6.2 inches (158 mm)
Side : 4 – 6.2 inches (102 – 158 mm)
Rear : 4 inches (102 mm)
Roof : .9 – 1.4 inches (25 – 38 mm)
In order to develop a tank with the firepower to assault enemy fortifications and heavily armored combat vehicles, particularly the German heavy tanks, it was important to mount a gun able to fulfill these multiple roles. As such, the 105 mm T5E1 was developed for the current U.S. heavy tank projects, T95 GMC and T29, with M6A2E1 becoming a test subject for feasibility of mounting the gun into a turreted tank design.
The 105 mm T5E1 was a 65 caliber long, high velocity multipurpose cannon based on the 105 mm T4 anti–aircraft gun, with a muzzle velocity of 914 m/s. The gun was made of a monoblock construction with uniform right hand rifling. It had a vertical sliding wedge breech block, with three recoil cylinders located on top of the gun cradle, installed on the T123 gun mount. Loading characteristics of the tank intended for installation demanded that the cartridge case and shell be separated as two–piece ammunition, with an effective rate of fire of 6 rounds/minute with 2 loaders. Another variant of the gun was the 105 mm T5E2, installed on the T123E1 gun mount. The only key difference was the relocation of one recoil cylinder to the bottom of the gun cradle.
The T29 could store up to 63 rounds, located in an armored rack in the hull and a ready rack in the turret. Ammunition types comprised the T13E2 APCBC–HE, T29E3 HVAP, T30E1 HE, T32E1 APCBC, T37 APBC, and T46 WP. Most of the 105 mm shells were rescaled from 90 mm shells, with the exception for the T13E2, which was based on the 75 mm M61 due to being developed much earlier for the T4 gun. Two separate propellant charges were provided, T8 for AP shot, HE, and WP shells, and T9 specifically for HVAP shot (with finer powder granulation). Both charges were assembled with the same cartridge case and components, namely 105 mm Case T4E1, Primer T48, Supplementary Igniter T9, and M1 Powder. The charges had been established to give a working pressure of 40,000 psi (2812.27 kg/cm²). Each cartridge case was closed by differently shaped plastic plugs, with flat contour for the T8 and convex contour for the T9 (to fit the recessed base of the HVAP projectile) to prevent mistakes in loading the separate projectile and charge.
The main cannon was complemented with two coaxial 12.7 mm M2HB machine guns, and a dual power telescope T143E1 in T154 telescope mount, adjustable from 4x to 8x of magnification. It was based on the T122/M83 telescope used for the 90 mm cannon. A secondary M10E5 periscopic sight with dual sights from 1x to 6x was provided for the gunner to give a wide angle of vision and acquire the target. Gun elevation/depression was +20/–10, and the turret was rotatable to 360° with an effective turret rotation of 18°/second.
The T13E2 APCBC–HE was the earliest anti–tank shell in development, carried over from the T4 AA gun. It had a muzzle velocity of 900 m/s, weighing 18.6 kg. It was a rescaled 75 mm M61 APCBC–HE. The fuze was a standard U.S. armor–piercing high explosive B.D. (Base Detonating) M66A1. It could penetrate 208 mm of vertical armor at 500 yd (457 m) and 180 mm at 2,000 yd (1,829 m).
The second armor–piercing shell was the T32E1 APCBC, a solid shot for the T5E1 after the T13E2 was developed. The base shell weighed 15.8 kg with 1.9 kg of hardened penetrating cap and steel ballistic cap, totaling 17.7 kg in overall, coming at a slightly higher velocity of 914 m/s. The third shell was the T37 APBC. It was not much different from the T32E1, as both were based on the same shell, the 90 mm T33 APBC. However, the T37 was a fully rescaled 90 mm, with the whole body and ballistic cap alone weighing 17.6 kg of similar size as the T32E1. Both APCBC and APBC could penetrate up to 235 mm and 216 mm of vertical armor from point blank range respectively.
T30E1 HE consisted of a cast TNT explosive packed inside a forged steel body shell with bursting charge and P.D. (Point Detonating) M51A4 fuze, weighing 15.4 kg in total. It came with two different charges, standard charge T8 for use at maximum range firing at 945 m/s, and reduced charge T20 for increased anti–concrete performance from short range at 762 m/s. It could penetrate 1.3 m of concrete at 1,500 yards (1,372 m).
High Velocity Armor–Piercing T29E3 provided the most effective anti–tank munition for the 105 mm. Weighing 11.2 kg, it consisted of a 4.5 kg tungsten carbide core, an aluminum ballistic cap and body with steel bourrelet band, and a steel base with two rotating bands and a tracer holder. It could achieve a muzzle velocity of 1,128 m/s, and penetrate 360 mm of vertical armor from 500 yd (457 m) and 292 mm from 2,000 yd (1,829 m). This was enough to punch through even the most heavily armored tanks in the war, including the Panzerjäger Tiger Ausf. B, colloquially known as the Jagdtiger heavy tank destroyer.
The T29 was powered by the Ford GAC, a 12–cylinder petrol engine producing 750 hp at 2,800 rpm, with a maximum torque of 224.6 kgf/m. It had a displacement of 27 liters. Weighing 825 kg dry, it was connected to tanks with a fuel capacity of 300 U.S. gallons (1135 litres), running on 80 octane fuel and equipped with a liquid–cooling system. This gave the 64-ton heavy tank a power-to-weight ratio of 11.68 hp/t. The GAC engine was 35.5 cm longer than the GAA engine that powered the M4A3 medium tank, necessitating a larger engine compartment to fit such a machine.
A General Motors Cross–Drive CD–850–1 transmission was connected to the Ford GAC. It combined the functions of a transmission, steering gear, and brakes in a single unit. This unit also incorporated two hydraulically selected gear ranges driving through a single phase torque converter. It had 2 forward and 1 reverse speed steering. The great advantage of the cross drive transmission was its simplicity of operation which eased the task of the driver. The top speed of the T29 was 35 km/h with a maximum cruising range of 160 km. It could climb 30° of sloped terrain, cross a trench up to 2.4 meters wide, ford depths up to 1.2 meters, climb steps up to 1 meter, and was capable of pivot steering by pushing the driver’s wobble stick to the left or right in neutral position, increasing the ability of the tank to exit from difficult terrain.
The suspension system was retained from the T26E3 Pershing, with 8 double road wheels with rubber tires connected to torsion bars and 7 return rollers per side. The drive sprockets were placed at the rear, as well as the transmission and the engine powering them, while the idler wheels settled at the front to keep the track tension. The T29 used as many as 102 links of T80E3 tracks on each side, a combination of 584 mm wide T80E1 rubber–backed, steel chevron tracks fitted with 127 mm wide Duckbill extended end connectors, increasing the total width up to 711 mm to reduce the ground pressure of the heavy tank to 0.85 kg/cm². The tank had a ground clearance of 480 mm.
The T29 was operated by a 6–man crew. Inside the turret, the tank commander was seated in the rear bulge immediately behind the 105 mm gun breech. He was provided with an M15 periscope and 6 vision blocks in his cupola. His seat could be adjusted vertically and horizontally for observation and movement. The SCR 508 / 528 radio set was installed in the turret bulge on the left side of the commander for intercom. Two loaders were stationed on each side of the breech, provided with two standard type escape hatches. Both had access to their ready racks located on both left and right side of the turret. When not in loading operation, the right loader could use a single pistol port on his side, while the left loader could use a 12.7 mm machine gun placed outside of the tank. The gunner manned the 105 mm gun and was located to the right of it, sitting on a seat slung from the turret ring, and equipped with a direct sight telescope and a periscopic sight. The driver and co–driver sat in the front hull and used M13 driver periscopes installed on their hatches for driving. Both had access to separate controls, including a mechanical control system to operate the transmission under normal conditions and two manual steering levers for emergency use.
The first production T29 completed by Detroit Arsenal was delivered to General Motors for installation of a different engine, the Allison V1710–E32, producing 850 hp at 2,800 rpm, and the CD–850–1 cross drive transmission. The hull length was slightly increased by 5 cm to accommodate the new engine installation. This modification was designated as T29E1 in December 1945.
The second production T29 was equipped with a combination of hydraulic power turret traversing and elevating mechanism and computing sight system developed by the Massachusetts Institute of Technology. It was designated as T29E2 in April 1948, and armed with a 105 mm T5E2 cannon in T123E2 gun mount.
On 31 May 1945, the T29 became the subject of an evaluation for the effectiveness of the integrated fire control system. This followed the development of the T25E1 No. 13 with T31 stereoscopic rangefinder, by incorporating the latest modification, the T31E1, and T93E2 telescope in T136 periscope mount, designated as the T29E3 in mid–1948. Three new panoramic telescopes for indirect fire with the 105 mm gun were also installed: T141 for the T31E1 rangefinder, T144 for the T93E2 telescope, and T145 for the M10E5 periscope. The T141 and T144 were installed in the gunner’s periscopic sight mount and the T145 in the turret roof.
The T31E1 rangefinder was a stereoscopic instrument with the base length of 9 feet (2.74 meters). It was not connected to the other fire control system, as it was operated manually by the tank commander to relay the range information using the control box below the rangefinder. The range and target lead data was transmitted by flexible shafting to the gunner for tracking the target. However, tests at Aberdeen Proving Grounds (APG) showed that backlash, as well as windup and binding of the flexible shifting, resulted in serious errors in the system. Although the rangefinder was particularly useful for spotting purposes. It also displayed the importance of a rangefinder to obtain a first strike capability beyond 1,000 yards (914 m).
In 1946, the T29 was planned for a gas turbine engine development program with the associated power train, estimated to produce up to 1,400 hp. The project was separated into three different phases; Researching the development data of the internal combustion turbines and power train suitable for the T29, developing a pilot gas turbine engine based upon the data derived in Phase 1, and installation of the engine into the T29. No further details have been revealed.
The T29 was developed too late to enter the war it was designed for, with the first tank finished at the end of hostilities in the Pacific War. The lack of preparation of any practical solutions to transport such massive vehicles overseas also contributed to its delay. However, all the equipment and modules that were developed during World War II would later pave the way for future American tanks. The cross-drive transmission was improved and later used by all subsequent tanks, up to the M60 main battle tank. The 105 mm T5E1 gun and its ammunition were adapted for post-war development and later known as the 105 mm T140 gun, installed on the T54 medium tank. The heavy tank project itself led to the development of the T43, and eventually to the M103 gun tank.
There are currently seven surviving tanks, four of which are located at the National Armor and Cavalry Museum, including T29, T29E3, T30, and T34. The remaining 3 are the T30s, located at Fort Jackson, Detroit Arsenal, and Anniston Army Depot.
Illustration of the Heavy Tank T29 showing the large size of the turret and the impressive size of the gun.
Illustration of the Heavy Tank T29E3 showing off the distinctive paraxial rangefinder on the top of the turret. These were used to quickly determine the distance to an enemy tank and improve the first hit chances.
Both illustrations were produced by Tank Encyclopedia’s own David Bocquelet
105 mm T5E1 L/65, 63 rounds
3x 12.7 mm M2HB, 2,420 rounds
1x 7.62 mm M1919A4, 2,500 rounds
Front: 70 – 102 mm
Side: 76 – 51 mm
Rear: 19 – 51 mm
Roof: 13 – 25 mm
Floor: 13 – 25 mm
Front: 158 mm
Side: 158 – 102 mm
Rear: 102 mm
Roof: 25 – 38 mm
Mantlet: 203 – 305 mm
10 (2x Pilot T29, 5x Production T29, 1x T29E1, 1x T29E2, 1x T29E3)
British Army Staff – AFV Technical Situation Report No. 23, June 1944
British Army Staff – AFV Technical Situation Report No. 25, August 1944
British Army Staff – AFV Technical Situation Report No. 27, October 1944
British Army Staff – AFV Technical Situation Report No. 28, November 1944
British Army Staff – AFV Technical Situation Report No. 29, December 1944
British Army Staff – AFV Technical Situation Report No. 30, January 1945
British Army Staff – AFV Technical Situation Report No. 31, February 1945
British Army Staff – AFV Technical Situation Report No. 32, March 1945
British Army Staff – AFV Technical Situation Report No. 33, April 1945
British Army Staff – AFV Technical Situation Report No. 34, May 1945
British Army Staff – AFV Technical Situation Report No. 35, June 1945
British Army Staff – AFV Technical Situation Report No. 36, July 1945
British Army Staff – AFV Technical Situation Report No. 37, August 1945
British Army Staff – AFV Technical Situation Report No. 38, September 1945
British Army Staff – AFV Technical Situation Report No. 39, October 1945
British Army Staff – AFV Technical Situation Report No. 40, November 1945
British Army Staff – AFV Technical Situation Report No. 41, January 1946
British Army Staff – AFV Technical Situation Report No. 42, March 1946
Armed Services Technical Information Agency – AD301343 – An Analytical Study of Data on Armor Penetration by Tank–Fired, Kinetic Energy Projectiles Nielsen, K. (2012). Pressed Steel Car Company, Authorhouse
OCM 25117 – Heavy Tanks T29 and T30 – Development and Manufacture of Pilots Recommended, 14th September 1944
OCM 25259 – Tanks, Heavy, T29 and T30 – Development and Manufacture of Pilots Approved, 28th September 1944
OCM 26438 – Gun, 105–mm, T5E1 for Mounting in Tank, Heavy, T29 – Assignment of Model Designation, January 1945
OCM 26439 – Fire Control Equipment for the Heavy Tank T29 – Development and Assignment of Designation
OCM 26825 – Tank, Heavy, T29 – Classification as Limited Procurement Type Recommended; Gun, 105–mm T5E1 and Ammunition Therefor – Initiation of Procurement Recommended, 1st March 1945
OCM 27245 – Tanks, Heavy, T29 and T30 – Procurement of Additional Pilots Authorized, 5th April 1945
OCM 27808 – Gun, 105 mm, T8 and Carriage, Gun, 105 mm, T19, Fire Control Equipment; Accessories, and Associated Equipment, 31st May 1945
Records of the Office of the Chief of Ordnance – Development History of the Heavy Tanks, T29 & T30, 1945 R.P. Hunnicutt (1988). Firepower: A History of the American Heavy Tank
Tanks Encyclopedia Magazine, #3
The third issue covers WW1 armored vehicles — Hotchkiss Htk46 and Schneider CA and CD in Italian Service. WW2 section contains two splendid stories of the US and German ‘Heavy Armor’ — T29 Heavy Tank and Jagdtiger.
Our Archive section covers the history of early requirements for the Soviet heavy (large) tank. Worth mentioning, that the article is based on documents never published before.
It also contains a modeling article on how to create a terrain for diorama. And the last article from our colleagues and friends from Plane Encyclopedia covers the story of Northrop’s Early LRI Contenders — N-126 Delta Scorpion, N-144 and N-149!
All the articles are well researched by our excellent team of writers and are accompanied by beautiful illustrations and photos. If you love tanks, this is the magazine for you! Buy this magazine on Payhip!
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