A month before the end of the First World War, Great Britain began development of the promising Medium Tank Mark D. This project reached the stage of construction and testing of a prototype, but in the end did not receive military approval. Subsequently, British engineers made several unsuccessful attempts to improve the existing tank. In addition, a proposal soon appeared, according to which the existing tank "D" was to become the basis for promising armored vehicles of other classes. These samples remained in history under the names Light Infantry Tank and Light Supply Tank.
In the early post-war years, the main light tank of the British army was the Mark A, also known as the Whippet. This tank differed from other armored vehicles of its time in its higher technical and operational characteristics, but by the beginning of the twenties it had become obsolete and needed to be replaced. In mid-1921, the military leaders took care of this problem and issued appropriate instructions. Soon the command of the Royal Armored Corps formed the requirements for a promising light tank intended to replace the Whippet.
Taking into account the experience in the development and operation of armored vehicles, the specialists of the military department issued a technical assignment for three vehicles at once, with some differences. The first of them was a light tank and was intended to accompany the infantry. With such tasks, it received the working designation Light Infantry Tank. The second armored vehicle was supposed to be operated in the colonies, which is why it was named Light Tropical Tank. The infantry tank was to be supplemented with an armored supply vehicle Light Supply Tank. All vehicles of the new family were supposed to have a relatively low combat weight, high mobility, anti-bullet protection and machine-gun armament.
Experienced Light Infantry Tank. No armament
The existing Mark A light tanks no longer fully met the requirements of the time, which is why the military wanted to accelerate the development of promising technology. This issue was resolved in a very interesting way. Shortly before the appearance of technical specifications for new armored vehicles, tests of the Mark D medium tank were completed. This sample did not suit the military, but individual ideas and solutions used in its creation could find application in new projects. After analyzing the possibilities and prospects, it was decided to build "Light infantry tank" and "Light supply tank" on the basis of the existing "D".
Moreover, with a certain proviso, the new vehicles could be considered options for a deep modernization of the existing tank. As part of promising projects, it was actually proposed to change the dimensions of the armored vehicle in order to meet the new requirements, while the basic ideas of the layout and other nature remained the same. At the same time, they decided to build a "tropical" tank for the colonies without directly borrowing technical solutions from the Medium Tank Mark D project.
An additional way to speed up the design and simplify future production was the maximum unification of the two machines. They were supposed to have a common chassis with a unified body, power plant and chassis. All major differences concerned the layout and equipment of the fighting compartment. In addition, the two samples differed in the most noticeable way in the range of tasks to be solved. Direct support for the infantry was assigned to the Light Infantry Tank, while the Light Supply Tank was actually an ammunition transporter.
Two new vehicles were proposed to be built on a unified chassis, which was a smaller version of the rejected Mark D medium tank. While maintaining the transverse dimensions at the same level, the hull was shortened, which also led to a redesign of the chassis. This led to a decrease in combat weight and allowed the use of a less powerful engine. In addition, the resulting chassis carrying capacity was used to slightly increase the armor.
The unified body of the two armored vehicles was assembled with bolts and rivets on the frame and had protection in the form of rolled sheets no more than 14 mm thick. The layout was based on ideas from a previous project. The front part of the hull stood out for the habitable compartment with all the crew's workplaces. Behind the crew compartment was a large compartment for the engine, transmission, fuel tanks, etc. The hull had large onboard units that were inside the tracks and had attachments for installing the necessary chassis devices.
The new body of reduced dimensions had a vertical frontal sheet, on the sides of which outriggers were mounted to install part of the chassis elements. Behind the frontal sheet, the body expanded, forming niches inside the tracks. Under such niches there were fastenings for the suspension and rollers, in a checkerboard pattern covered with armored shields. The front part of the roof of the "Light Infantry Tank" had a curved shape and was intended for the installation of the wheelhouse. The rear of the hull was equipped with a horizontal roof. Depending on the type of vehicle, the chassis could have inclined or rounded stern plates.
Mark D medium tank prototype
The Light Infantry Tank armored vehicle received a wheelhouse similar to that used in the Medium Tank Mark D project. It had a curved front plate to which side parts of a similar shape were attached. The stern leaf was distinguished by an increased height, which is why the wheelhouse received a curved roof, inclined forward. In the aft part of the top sheet there was an opening for installing a turret with a hatch and viewing slots.
"Light supply tank" received a superstructure of a less complex shape. In the frontal part of its hull, it was proposed to place an armored structure of a trapezoidal profile. She had an inclined frontal sheet, vertical sides and a horizontal roof. In the center of the roof, a small rectangular turret with observation devices was provided.
It was proposed to equip the chassis of the Light Infantry Tank and Light Supply Tank with a Hall-Scott gasoline engine with a capacity of 100 hp. Through a mechanical transmission of a simple design, the engine was connected to the stern drive wheels.
The chassis was used, which was a reduced and revised version of the system from the "D" project. On each side, with the help of an interlocked spring suspension, 22 road wheels of small diameter were attached. On the extended bases in the front of the hull were placed guide wheels, in the stern - leading. The upper branch of the caterpillar lay on several supporting rollers and special rails. In two new projects, the so-called caterpillar was again used. skeletal structure. A metal chain of small width interacted directly with the rollers and wheels, to which transverse tracks were attached. To improve traction and weight distribution, the tracks could swing relative to the chain.
The armored cabin of the Light Infantry Tank received three embrasures with mountings for machine guns. In the frontal sheet there was a larger installation, which, according to some sources, could carry two machine guns at once. Two more similar devices for one machine gun each were placed on the sides. The armament of the tank consisted of three or four Hotchkiss 7.7 mm machine guns. The placement of machine guns in three installations, borrowed from the previous project of a medium tank, made it possible to simultaneously attack several targets in different directions. Some sources claim that the Light Infantry Tank did not have a wheelhouse, but a rotating turret, but this information does not have sufficient confirmation.
The Light Supply Tank was not intended for direct combat missions, but it had weapons for self-defense. In the frontal leaf of its cabin there was a ball mount for mounting one rifle-caliber machine gun. With its help, the crew could defend against enemy infantry, but the attack of any serious targets, for obvious reasons, was excluded.
"Light infantry tank" at the training ground
The main task of the "Light Supply Tank" was the transportation of ammunition and various materiel needed by the troops during battles. For transporting the payload, it was proposed to use an open cargo area. Almost the entire rear part of the hull roof, located behind the cockpit of the crew, was a platform for storing certain cargo. In order to avoid the loss of cargo during movement, the platform received side fences of a simple design. Convenience of loading and unloading was proposed to be provided using a rounded unit with a flooring, placed at the junction of the roof and the stern sheet.
The infantry tank's crew consisted of five people. All tankers were located in a single volume, which served as a command and control compartment and a fighting compartment. In front of the compartment were the driver and his assistant. They could use hatches in the wheelhouse roof. There were observation slots for observing the road. The crew also included two shooters and a commander. The latter was located in the aft section of the compartment and could monitor the terrain with the help of the viewing slots of its turret. The latter was equipped with a hatch. Two shooters could use any machine guns available. Apparently, if necessary, the driver's assistant and commander could act as machine gunners, which made it possible to simultaneously use the entire available complex of weapons.
There is no exact information on the composition of the crew of the supply vehicle. Probably, she could be controlled by a driver and his assistant, as well as a shooter. This made it possible to control the car and, if necessary, engage in self-defense. Access to the habitable compartment was provided by a sunroof.
The Light Infantry Tank and Light Supply Tank projects involved a significant redesign of the existing Mark D chassis, aimed at reducing the size of the vehicle in accordance with the new customer requirements. This task was successfully accomplished. Both armored vehicles had a length of slightly more than 6, 7 m with a width of less than 2, 2 m and a height of no more than 2, 8 m. The combat weight of both samples reached 17, 5 tons. At the same time, the transport armored vehicle could take on board up to several tons of various cargo. Despite the low power-to-weight ratio, both cars had to reach speeds of at least 30-35 km / h on the highway. There was an opportunity to overcome various obstacles. According to some reports, the voluminous hull made it possible to sail, but the buoyancy margin left much to be desired.
The reworking of the existing project, despite all its complexity, took only a few months. Thanks to this, the design documentation for two promising armored vehicles for different purposes was prepared already in the 1921 year. In the last months of the year, the assembly of prototypes began. One prototype was built for each project. Soon, two vehicles entered the proving ground and demonstrated their potential.
The design performance has been confirmed. The Infantry Tank and Supply Tank showed acceptable mobility. Thus, the use of the original undercarriage, which was originally created to increase cross-country ability, again justified itself and made it possible to obtain the required capabilities. In terms of firepower, the Light Infantry Tank hardly differed from the base Medium Tank Mark D, which had a similar fighting compartment and similar armament. The Light Supply Tank, in turn, could carry large loads, primarily ammunition, etc.
Transport vehicle Light Supply Tank, aft view. The cargo area is clearly visible
However, both types of armored vehicles had noticeable problems. First of all, they differed from other modern machines in their greater design complexity. Because of this, the assembly and operation of equipment were associated with certain difficulties, and also differed in increased cost. From the point of view of labor intensity and price, the new light armored vehicles did not look very good against the background of other developments in their class.
Having studied the pros and cons of the two presented samples, the command of the British Panzer Corps decided to abandon their adoption. Too complex and expensive a tank and transport vehicle were of no real interest to the troops. After this decision, the project was closed for lack of prospects. Two prototypes remained in storage for some time, but later went for disposal. Further development of British armored vehicles was now carried out in the framework of other projects.
The projects of the Light Infantry Tank and Light Supply Tank vehicles were intended for the fastest renewal of the armored vehicle fleet. At the same time, the "Light Infantry Tank" was a replacement for the aging Mark A Whippet, and the "Light Supply Tank" was the first representative of its class, capable of significantly increasing the mobility of troops and optimizing their supply. To accelerate the development of new projects, it was proposed to use the existing ideas and solutions in the most active way. This really helped to reduce the design time, but led to other inherent problems.
One of the reasons for abandoning the Medium Tank Mark D was the overly complex design, primarily of the chassis. In the course of revision in the framework of new projects, the existing chassis was reduced and seriously changed in accordance with the current requirements of the customer. A direct consequence of this was the preservation of almost all the existing problems associated with the high complexity of the suspension and caterpillar. Thus, the overcomplicated design first led to the abandonment of the medium tank, and then "destroyed" two light vehicles.
In 1920-21, British engineers were developing and reworking the Medium Tank Mark D project. The first results of this work were two options for upgrading the basic design. Subsequently, on the basis of a medium tank, two light vehicles for various purposes were developed. All these projects did not progress beyond the proving grounds, and the army did not receive such types of armored vehicles. After the closure of the Light Infantry Tank and Light Supply Tank projects, the development of the existing cross-country chassis stopped. The following British tanks were based on different ideas and solutions.
