The First World War gave impetus to the development of a significant number of areas in the field of weapons and military equipment. However, not all of the original designs of that time were created in connection with the outbreak of war in Europe. Local conflicts in other regions could also influence the development of armies. So, the North American Border War in the mid-tens of the last century led to the emergence of a very original and interesting project of the super-heavy combat vehicle Holt 150 ton Field Monitor.
At the end of 1910, a political crisis began in Mexico, culminating in a change of government and civil war. Over the next several years, various political forces, supported by armed groups, tried to take power into their own hands. In addition, some groups have frequently invaded the neighboring United States and attacked local settlements. The US Army tried to combat such raids, however, despite all the successes in this matter, the attacks did not stop. It was obvious that some new means were needed to solve the existing problem.
In 1915, the Holt Manufacturing Company proposed its own solution to the problem of raids, which built various tractors and worked out various options for promising combat vehicles. As conceived by the company's specialists, self-propelled vehicles were required for a more effective fight against violators of the army's border. It was proposed to provide superiority over the enemy with the help of thick armor and sufficiently powerful artillery weapons. At the same time, in the new project, it was possible to use a number of existing developments in other equipment, while individual components and assemblies would have to be created from scratch.
Reconstruction of the Holt 150 ton Field Monitor machine
The future armored vehicle was planned to be used in the southern regions of the United States, which had a characteristic landscape. In addition, during the pursuit of the enemy, the possibility of crossing the border with access to similar areas belonging to Mexico was not ruled out. The features of the intended combat use made it possible to significantly simplify the technical appearance of the future vehicle. Sufficiently strong soils of the southern regions allowed the use of a wheeled propeller, providing the required characteristics of cross-country ability and mobility.
Working out the technical appearance of the future armored vehicle led to very interesting results. It turned out that obtaining optimal characteristics will lead to an increase in size and combat weight. The last parameter was supposed to reach the level of 150 tons. The presence of armor and a well-developed complex of weapons made us recall the ships of the "monitor" class. For these reasons, the original design of the armored combat vehicle was officially named the Holt 150 ton Field Monitor. In case of successful completion of the project and acceptance into service, the vehicle could have received one or another official army name, but this did not happen.
A promising combat vehicle had to be distinguished by a uniquely large mass, which, first of all, was associated with the level of protection. According to the surviving data, from a certain point in the project of the "monitor" the possibility of using a reservation with a thickness of 24 to 75 mm was considered. It is curious that in some sources the same numbers are indicated, but measurements are given in inches. However, the 75-inch armor (1905 mm) looks implausible and is clearly the result of a unit error.
The armor not less than an inch thick would allow the car to confidently withstand bullets and shrapnel, as well as protect the crew from small and medium caliber artillery. Due to the level of development of technologies of that time, the armor parts had to be assembled into a single structure using a frame of the required shape and various fasteners.
According to reports, the 150 ton Field Monitor project proposed the construction of an armored hull of a rather complex shape, formed by a large number of rectangular or beveled panels. In terms of the body, it was supposed to have a shape close to rectangular. With the horizontal bottom, it was necessary to mate vertical sides, consisting of a large number of separate parts. In the center of the boards, protruding sponsors were provided. The frontal projection of the hull was covered with a vertical bottom sheet, above which a more complex structure was placed. In the center of the upper forehead there was a triangular protrusion, on the sides of which it was proposed to place a pair of gun mounts with cylindrical movable masks.
Behind the gun mounts was a large superstructure, which occupied about half of the total length of the hull. The superstructure had a vertical stern sheet connected to the horizontal roof of the stern compartment. The stern projection was covered with a vertical sheet of medium height.
It was proposed to equip the combat vehicle with a pair of towers of the same design with a shoulder strap with a diameter of 2 m. One of them was to be placed in the front of the hull, above the gun mounts. The second was located on the roof of the stern, just behind the superstructure. The towers had a cylindrical shape without separate frontal or side parts. On the horizontal round roof, it was proposed to provide an opening for the installation of a turret with viewing slots.
Given the high combat weight, the authors of the project found the only suitable power plant that could be built at that time using the available technology. The 150-ton monitor was to be driven by two high-power steam engines. These products were developed by Holt with the active assistance of Doble engineers. Specialists of the two organizations already had experience in the joint design of steam power plants, which, to a certain extent, helped in the creation of a new armored vehicle.
According to some reports, the entire aft part of the hull, which was distinguished by its lower height, together with a part of the central compartment, was given over to two high-power steam engines. The main gearbox was connected directly to the steam engines, with the help of which the torque was distributed to all four wheels. In order to obtain the best possible characteristics of mobility and handling, it was decided to equip all wheels with their own gearboxes. Thanks to this, as one might expect, the 150 ton Field Monitor could do without the steerable steering wheels.
The undercarriage of the super-heavy combat vehicle consisted of four wheels with a diameter of 20 feet (6 m). The use of all-metal wheels has been proposed. They had to have a tire assembled from a large number of metal plates. The lateral projection of the wheel was completely covered by a disc of the corresponding dimensions. The wheels had to be mounted directly on the axles of their gearboxes. The use of any depreciation systems was not envisaged. Swivel mechanisms were also not used; it was proposed to maneuver by changing the speed of rotation of the wheels of different sides.
In the frontal part of the hull, on a pair of their own installations, the main guns of the combat vehicle were to be placed. It was proposed to use 6-inch (152 mm) ship guns of the available types as the "main caliber". Based on dimensional considerations, the permissible barrel length was limited to 30 calibers. The possibility of using smaller-caliber artillery systems, including those with a shortened barrel, was also considered. In all cases, the design of the hull and gun mounts ensured firing within not too wide horizontal and vertical sectors. Despite the differing characteristics of the guns of different models, the "Field Monitor" in any case had to show high firepower.
To attack enemy manpower, it was proposed to use 10 Colt M1895 machine guns at once. Two machine guns were planned to be installed in two towers. The rest could be distributed among several installations in the corps sponsons. Thus, the machine gunners were able to control a significant part of the surrounding area. All machine guns had limited sectors of fire, but their areas of responsibility were partially overlapped. The joint use of machine guns made it possible to attack targets in almost any direction.
An interesting feature of the Holt 150 ton Field Monitor project is the large crew. The car was to be driven by 20 people. The driver and two onboard engineers were to control the movement and the main systems. The operation of the guns was entrusted to at least 6-8 gunners. The remaining crew members served as machine gunners. Crew jobs were distributed throughout the habitable volume of the hull and turrets. At all places there were means for observing the terrain and targeting weapons. Access to the car was provided by side hatches located under the hull sponsons.
The total length of the future "monitor" was supposed to reach or exceed 20 m. The width of the vehicle was within 4 m, the height was at least 7 m. The combat weight, according to calculations, reached 150 tons. If even the most efficient steam engines were used, the new armored vehicle could develop a speed of no more than several kilometers per hour. The power reserve, limited by the availability of fuel and water, could not be outstanding either.
According to the original plans of Holt Manufacturing, the design of the 150 ton Field Monitor armored vehicle should have been completed in 1915, and after that the necessary documentation was submitted to the military. If a positive decision was received, already in 1916 the first prototype could go to the test site. The further fate of the most interesting project was to be determined in accordance with the wishes of the customer. It soon became clear that such plans could only be partially implemented.
Indeed, by the end of 1915, the Holt designers completed the preparation of the project, and soon the package of necessary documents was sent to the military department. Its leaders got acquainted with the unusual proposal, but were not interested in it. First of all, "Field Monitor" was criticized by General John Pershing. He rightly noted that a heavy and slow machine will not be able to effectively support the cavalry. Escorting the infantry, in turn, also could not lead to outstanding results justifying the construction of large and heavy vehicles.
The military even refused to build and test a prototype. However, the development company did not give up hope. She continued the development of the existing project, trying in one way or another to improve the main characteristics and expand the existing capabilities. For example, the artillery armament complex has consistently undergone several modifications. In addition, the outdated M1895 machine guns have given way to the newest M1917. The main features of the architecture and construction, however, have not changed. Probably, in some cases, the processing of certain ideas was associated with the need for a complete redesign of individual structural elements.
Armored "monitor" case
Available information suggests that as the development of the existing project, which lasted for several years, the designers of the company "Holt" managed to save their project from some weaknesses and certain shortcomings. However, in the updated form, the super-heavy wheeled combat vehicle could not interest the military. It is noteworthy that by this time the US command began to prepare to enter the war in Europe, however, in this theater of operations, it was not possible to find a place for the Holt 150 ton Field Monitor. The military leaders still believed that mobile combat operations were the task of cavalry and light armored cars.
After several years of work that did not give any real results, Holt Manufacturing was forced to close a project that once seemed promising. In its original form, it did not interest the main customer in the person of the United States Army, and the subsequent modernization and improvement did not lead to the desired consequences. The project was closed and all documentation went to the archive with no hope of returning from there.
At present, with modern knowledge of armored vehicles, it is not so difficult to understand the reasons for abandoning the original "Field Monitor". At one time, such a combat vehicle could not find real use for a number of reasons. Moreover, even in later periods, the proposed technical design did not allow obtaining the desired results. First of all, the reason for the failure was the unjustified enlargement and overweight of the structure. The 20-meter 150-ton four-wheeled vehicle would be too complex to build and operate.
Steam engines could be a big problem. They were able to provide an acceptable power density, but the low reliability of such a powerful power plant would seriously impede the operation of the 150 ton Field Monitor. The proposed wheeled chassis could also lead to difficulties, for example, when overcoming certain obstacles. In fact, an all-wheel-drive wheeled vehicle would only be able to drive over relatively flat landscapes in the southern states or Mexico without any problems.
As further experience in the creation of armored vehicles showed, an artillery self-propelled gun can carry one gun and at the same time have high combat qualities. From this point of view, the two installations with 6-inch guns, proposed for placement on the "monitor" look redundant and unnecessarily complex. The rejection of some of the guns or even one of the turrets would lead to hefty weight savings and corresponding advantages of a different nature.
The placement of twin machine gun mounts in rotating turrets was a definite plus of the project. However, the proposed turrets were too large for such weapons, which could lead to certain production and operational difficulties. The high placement of the towers could make it difficult to fire at targets located at a short distance from the armored vehicle. It should also be noted that the proposed placement of machine guns left a lot of dead zones, primarily covered by large wheels.
Thus, the proposed super-heavy combat vehicle Holt 150 ton Field Monitor had only a few notable advantages. First of all, she could simultaneously attack several targets with cannon and machine gun fire without significant risks to the crew. In addition, having appeared on the battlefield, a huge machine with powerful weapons had every chance of provoking panic in the ranks of the enemy. This was where its advantages ended. All other technical and operational features were associated with a variety of problems.
In such a situation, the military's refusal to support an unusual project does not look like something unexpected or wrong. The command reasoned sensibly and did not help in the further development of a deliberately unpromising model. Holt engineers, in turn, had the opportunity to study an interesting concept at a theoretical level and draw all the necessary conclusions. According to the results of the work carried out, in the next project of a military vehicle, the designers decided to do without overly bold proposals and significantly reduced the overall dimensions of the equipment.
