The first tanks that entered the battlefields of the First World War had a noticeable impact on the course of battles and demonstrated the need for such technology. Nevertheless, the armored vehicles of the early models did not differ in high performance and had a lot of other disadvantages. Soon, new projects of military equipment appeared, which took into account the experience of operating existing tanks, and also proposed some new ideas. The Medium Tank Mark D left a noticeable mark on the history of British tank building.
By mid-1918, the British army was armed with tanks of several classes and types, differing from each other in different characteristics and combat capabilities. For example, heavier "rhombuses" could show high cross-country ability on rough terrain, while light tanks were distinguished by a higher travel speed. At the same time, a significant part of the vehicles carried relatively weak armor and were equipped only with machine guns. The study of the operating experience of all available tanks soon led to the formation of new concepts and the emergence of promising armored vehicle architectures.
Wooden model of the Medium Tank Mark D
Already almost no one doubted that the best solution to the existing problems were medium tanks, which combine the high mobility of light vehicles and the fighting qualities of heavy vehicles. In this regard, in the second half of 1918, several similar projects were launched at once. One of them received the designation Medium Tank Mark D - "Medium Tank, Type D". It is interesting that the work on the "D" project started in October 1918, i.e. literally a few weeks before the end of the war. As a result, the tank quickly lost all chances to enter the battlefield, but the project was still not stopped and came to trials.
The promising tank had special requirements in terms of mobility and firepower. The machine was supposed to overcome ditches at least 3 m wide and be able to attack targets in any direction. The solution of such problems led to the formation of an unusual technical appearance of the tank. Even against the background of other "land ships" of its time, the new Medium Tank Mark D looked very remarkable and unusual. At the same time, however, the project had to use some of the usual, from a modern point of view, solutions.
The main ideas of the project were worked out already in the last months of 1918, thanks to which a full-size wooden model appeared in November. Based on the results of checking this product, the necessary improvements were identified, after which the project was changed as required. The hull has undergone some changes, the composition of the onboard units has changed slightly. Other original technical solutions were not processed.
The Medium Tank Mark D project proposed the construction of a fairly large combat vehicle capable of showing high maneuverability on rough terrain. To solve such problems, the designers developed a new chassis that had little resemblance to existing systems. So, to overcome wide trenches, it was proposed to use a tracked propeller with the maximum possible base. The overall cross-country ability was improved due to the non-standard track design.
Same layout, side view
The main element of the "D" medium tank was the armored hull of the original design. The body was assembled from armor plates with a thickness of 8-10 mm. Using bolts and rivets, individual sheets were mounted on a frame assembled from metal profiles. The body layout was close to what is now called classic. The habitable volume was located in the front of the hull, combining the control compartment and the fighting compartment. A large aft compartment was given over to the power plant and transmission. At the same time, the car did not have a rotary tower, instead of which a large fixed wheelhouse was used.
The body of the tank received a relatively narrow and high curved frontal plate. On the sides, beams and shields were attached to it, which were necessary to move the chassis elements forward relative to the body. According to some reports, the hull was distinguished by the presence of onboard volumes located inside the tracks. Moreover, he had vertical sides of great length. There was no roof in the front of the hull, since there was a wheelhouse with weapons in this place. In the stern, a cover for the engine compartment was provided, made in the form of a truncated pyramid of low height. The stern was made from several armor plates located at different angles to the vertical.
To place weapons, it was proposed to use a fixed wheelhouse, placed in the frontal part of the hull. Its front part was flush with the frontal sheet of the hull and repeated its shape. The sides of the wheelhouse were made curved. Due to this, they noticeably protruded beyond the main body and formed a kind of fenders niches. The stern of the tower also had a rounded shape, and this sheet differed from others in its increased height. In this regard, the wheelhouse received a curved roof with a raised stern, in which there was a small turret with viewing slots.
The central and aft parts of the hull were given for the installation of the power plant and transmission. Since the tank was large and heavy, it needed an appropriate engine. However, there was no shortage of free volumes for the installation of a powerful power plant. The Medium D tank was equipped with a 240 hp Armstrong Siddley Puma carburetor engine. The engine was connected to a mechanical transmission of a relatively simple design required to drive the rear drive wheels.
Tank "D" during a demo ride
One of the tasks of the project was to increase the cross-country ability. To solve it, it was proposed to use the original design of the chassis, which resembled existing systems, but at the same time had some noticeable differences. At the bottom of each side with the help of the so-called. cable suspension was installed on 28 road wheels of small diameter. At the same time, the beam-base of the rollers was made curved, because of which only part of the rollers rested on the ground, while the rest, under normal conditions, were raised above it and served as tensioning. Also, the tank received supporting rollers, uncharacteristic for British armored vehicles of that era, five on each side. In the front and rear parts of the side, guide and drive wheels of large diameter were placed. All the main parts of the chassis were covered with armored side shields.
The Medium Tank Mark D received a new track of an unusual design. Instead of single cast tracks, the so-called system was now used. skeletal type. The basis of such a caterpillar was a narrow metal chain, to which large track links were attached. This allowed us to obtain an acceptable support surface with a minimum weight of the belt assembly.
All armament of a promising medium tank was to be located in the front wheelhouse of the hull. Various options for the armament complex were considered, involving the use of machine guns and cannons. The most powerful complex was supposed to include a 57-mm gun and two rifle-caliber machine guns. Nevertheless, this version of the weapon never left the blueprints, and the experienced equipment received a less powerful weapon.
In the center of the frontal sheet of the cabin and in the sides, there were three ball mounts for machine guns. It was proposed to use 7, 7-mm Hotchkiss machine guns. The design of the machine-gun environment made it possible to fire at targets within fairly wide sectors in the front hemisphere and to the side of the tank. The task of quickly transferring fire to large angles could be solved by the simultaneous use of different machine guns. Ammunition in the form of several thousand rounds should be transported inside the habitable compartment on the appropriate racks.
Tank on the water. Some parts have been removed to facilitate construction
According to known data, the crew of the medium tank "D" was supposed to consist of four people. The car was driven by a driver, his assistant, commander and gunner. The workplaces of the entire crew were located in the forward habitable compartment of the hull and were not separated from each other in any way. The driver and his assistant were located in the front of the compartment and could observe the road using roof hatches or viewing slots in the frontal sheet. The commander was located in the stern of the wheelhouse and used a turret with viewing slots. The hatches of the driver and commander were used to access the inside of the tank. In addition, another round hatch was placed on the left side of the hull.
Regardless of the situation and the current situation, the driver had to drive the tank. The main task of his assistant was to monitor the operation of the power plant. The commander, first of all, had to observe the battlefield and look for targets. The shooter served the weapon. Under the appropriate circumstances, the driver's assistant and commander could help the shooter and take control of the two machine guns. Thus, the crew had at least the theoretical possibility of the simultaneous use of all available weapons.
The original undercarriage, adapted to overcome obstacles, had a noticeable effect on the dimensions of the tank. The overall length of the Medium Tank Mark D reached 9, 15 m. The width did not exceed 2.2 m, the height did not exceed 2.5 m. The combat weight was 13.5 tons. Relatively high power density (slightly less than 18 hp at ton) made it possible to accelerate to 35-37 km / h on a good road. The power reserve was 170 km. The tank could climb a wall about 1 m high and cross a trench more than 3 m wide.
The promising tank was distinguished by large internal volumes filled with air. As a result, it had limited buoyancy and could cross water obstacles not only along fords. However, the actual characteristics on the water were not too high and imposed significant restrictions on the crossing of water bodies.
The car could climb the slope coast
The development of the Medium D project was completed after the end of the First World War. Despite the truce and a peace treaty signed later, Great Britain needed new armored vehicles, which led to the continuation of work on a number of projects. In 1920, the first prototype was built for testing. Soon this car was sent to the test site, where it was planned to check its driving performance. It should be noted that at that time the prototype was unarmed. Nevertheless, the absence of relatively light machine guns could hardly have a noticeable effect on the main characteristics.
At the test site, the tank confirmed the design characteristics. He developed the highest speed for his time and could overcome various obstacles, including unacceptably difficult for other armored vehicles. The most important difference from other tanks of that time was the ability to sail. Armament checks and assessments were not carried out due to its absence.
At the same time, drawbacks were identified that are directly related to obtaining high technical characteristics. The Mark D tank turned out to be very difficult to manufacture and operate. First of all, difficulties of one kind or another arose during the assembly and maintenance of the overcomplicated chassis. Also, in some situations, there could be problems with maneuverability associated with the large length of the tracks and the base of the chassis.
Checks and fine-tuning of the tank in the basic configuration continued for several months. Initially, tests were carried out only on land, but in 1921 the experienced Medium Tank Mark D went to the reservoir for the first time. First, the testers tested the capabilities of the armored vehicle in moving along the fords. Later, after some minor modifications, an attempt was made to make the tank fully floating. In the following checks, it was found that the machine has some potential in this context, but its implementation is associated with a lot of difficulties.
Second prototype of the Medium Tank Mark D.
The tank was indeed able to float on the water without using any additional means. By rewinding the tracks, he could swim at a speed of about 5 km / h. However, the draft was unacceptably high. During tests on water, the car was noticeably lighter, but even in this form it sank to the level of the axles of the guide and driving wheels. The installation of all armor and weapons would necessarily lead to an additional loss of buoyancy. As a result, the tank was afraid of even a little excitement. For launching and going ashore, the car needed a shallow section of the bottom and beach with sufficient hardness, which still needed to be found.
The proposed medium tank "D" was distinguished by high characteristics of mobility and maneuverability, but it was not devoid of noticeable shortcomings. Armament and armor were not powerful enough, and assembly and operation were associated with a host of problems. Real advantages over the existing technology were either absent or overridden by shortcomings and lag in certain characteristics. Such an armored vehicle was not of interest to the British army. In 1921, the military ceased to show clear interest in the Medium Tank Mark D project, and alternative developments began to receive more support.
Nevertheless, work on this project did not stop immediately. Taking into account the experience of testing and criticism of the customer, attempts were made to modernize the existing machine. Soon two new variants of the medium tank appeared. According to some reports, new projects were tested using an existing prototype. It was rebuilt twice in one way or another, and each time it received some improvement in performance. However, there is reason to believe that new projects were tested using one or two separate prototypes.
The first upgrade was designated the Medium Tank Mark D *. It is known that this project proposed a minor upgrade of the chassis. Apparently, it was a question of simplifying the existing design with optimization of suspension systems, but at the same time maintaining the overall architecture. According to some reports, such processing led to a change in the design of the side flaps and the rearrangement of the devices they closed.
Experienced armored vehicle, rebuilt according to the Medium Tank Mark D ** project
The next project, the Medium Tank Mark D **, included a new modification of the chassis and the superstructure design. The latter received an additional turret with viewing slots, which made it possible to increase the awareness of the crew. The second turret was placed in front of a roof on a special superstructure. The undercarriage received updated tracks. They retained the skeletal structure, but the cross members could now swing relative to the main chain. This should to some extent improve the distribution of the machine's weight on the ground and increase cross-country ability.
Two modernizations of the Mark D tank made it possible to improve the technical and operational characteristics to a certain extent, but did not lead to the desired results. By the time the modification appeared with two asterisks in the name, the military department had time to consider the available proposals and draw conclusions. The Medium Tank Mark I, developed by Vickers, was recommended for service. The armored vehicle under the letter "D" lost all chances to get into the troops.
Probably out of a desire to bring the existing developments to practical use, the authors of the Medium Tank Mark D project used it as the basis for new types of armored vehicles. In the same 1921, new armored vehicles were created, based on the existing project. They were different in size, and also had other onboard equipment. Nevertheless, even such developments did not allow bringing the existing concepts to mass production and subsequent operation in the troops.
The completed prototype (or prototypes) has been sent to storage. It is known that he remained at the Bovington Proving Ground until at least the late twenties. Later the car was disposed of as unnecessary. Currently, the experienced Medium Tank Mark D can only be seen in the few surviving photographs.
The goal of the Medium Tank Mark D project was to create a promising medium tank that combines all the best qualities of existing equipment. The assigned tasks were successfully solved, but the price was unacceptable complexity of design and operation. Other samples of a similar purpose, developed in parallel with the "D" tank, had fewer drawbacks, which determined the final choice of the military. The designers tried to modernize the medium tank or make it the basis for new armored vehicles of a different class, but all these attempts also did not affect the future rearmament of the army, although they left a noticeable mark on the history of British tank building.
