By the fall of 1942, British designers had developed a second version of their CDL searchlight tank, based on the chassis of the M3 Grant combat vehicle. Soon this technique was shown to representatives of the United States, and they showed interest in such a development. At the beginning of the next year, work began on the creation of an American analogue of British special vehicles. In addition, in 1943, it was decided to transfer the existing searchlight installations to a newer and more advanced chassis. This resulted in the emergence of several projects of unusual equipment based on the M4 Sherman medium tank.
The original goal of the Canal Defense Light project was to create an armored vehicle with a powerful searchlight. It was assumed that a large group of such equipment would be able to highlight enemy positions, ensuring the offensive of troops in the dark. In addition, it was planned to use some original ideas aimed at further aggravating the enemy's position and increasing the survivability of searchlight tanks. The first carrier of the special CDL turret was the British Mk II Matilda II infantry tank. Subsequently, such a unit began to be installed on the American M3 medium tanks.
Experienced searchlight tank "E" / M4 Leaflet. Photo Network54.com
Already at the beginning of 1943, the American and British military understood that the Lee / Grant tanks were rapidly becoming obsolete and therefore had very limited capabilities even in the context of the construction of special and auxiliary vehicles, not to mention their intended use. It was obvious that all new designs should be based on different chassis of the latest models. One of the most successful carriers of various weapons or special equipment could be the M4 Sherman medium tank of American design.
By June 1943, American specialists completed the development of the T10 Shop Tractor searchlight tank, which was actually a slightly modified version of the British CDL Grant. Immediately after that, work began on the creation of the next sample of such equipment, using a newer chassis with increased characteristics. In addition, in the course of this modernization, it was proposed to create an updated version of the searchlight installation with more capabilities. First of all, it was necessary to increase the power of the existing lamp or lamps. Also, the updated machine needed more advanced surveillance equipment.
Further research showed that a promising searchlight tank can hardly do with just one high-power lamp and needs to use two such products. This made it possible to significantly increase the main characteristics, although it forced the development of a completely new turret. Such a price for a deep modernization was considered acceptable, as a result of which the final appearance of the future special machine appeared.
The next project of the CDL family was to be created using approaches already known and proven in practice. It was proposed to take a ready-made medium tank, remove units that are no longer needed from it, install some new systems, and also mount a turret with the required composition of equipment. This made it possible to save on mass construction and operation due to the maximum possible unification of searchlight tanks with linear ones.
Sherman tanks of all existing modifications, differing from each other in various features, could be used as the basis for the new vehicle. So, it is known that at least one of the prototypes built according to the American project was based on the M4A1 chassis. Such a tank had a cast hull with 51 mm thick frontal armor and 38 mm side elements. The project made it possible to preserve the existing layout with a front-mounted transmission and control compartment, a central fighting compartment and aft engine compartment. Changing the chassis was carried out only by removing some large units and installing others.
M4 Leaflet projections. Figure Network54.com
The tanks of the M4A1 modification were equipped with Continental R975 C1 radial gasoline engines with a capacity of 350 hp. With the help of a propeller shaft passing through the habitable compartment, the engine was connected to the front-mounted transmission. The undercarriage had six road wheels on each side, interlocked in pairs on bogies with spring damping. During the construction of searchlight tanks on the basis of "Shermans" of other modifications, the composition of the power plant and the design of the chassis could change.
During the alteration in accordance with new ideas, the existing medium tank lost its turret with cannon and machine-gun armament. In addition, all racks and stowages were removed from the fighting compartment to accommodate standard ammunition. Part of the freed up volumes were used to install new electrical systems. The largest new component is a 20-kilowatt power generator directly connected to the main engine. Such a powerful generator was required to power the improved searchlight installation.
In accordance with the updated requirements, a new tower was created that could accommodate two searchlight installations at once. At the same time, existing developments from previous projects were widely used in its design. On the standard chase of the body, a cast cap of a shape close to cylindrical was to be installed. The frontal part of this unit had a slight backward tilt. On the side, small overhangs were provided on it, necessary for the installation of some equipment. The center of the frontal part of the turret had an embrasure for a machine gun. On either side of it were narrow vertical windows for searchlights.
Based on the experience of previous projects, the tower was divided into three sections. The central part was given over to accommodate the operator and weapons for self-defense. The front of this compartment was equipped with a machine gun mount and electrical controls. In addition, the workplace was equipped with means for controlling the guidance of searchlights in two planes. The operator was next to them. Access to the operator's compartment was provided by hatches in the roof and stern of the tower. Three periscopic viewing devices were installed in the roof above the operator.
To highlight enemy positions in the new project, it was proposed to use two searchlights at once, based on existing ideas. The side compartments of the tower were equipped with units of a similar design. Each of them used its own high power carbon arc lamp equipped with a mirror system. With the help of a curved mirror placed at the front of the turret, the light flux was redirected to the stern. There was a direct mirror, with the help of which the rays were transferred in the direction of the frontal vertical embrasure. As with British floodlights, this system illuminated a sector several degrees wide and high. The presence of two searchlights was supposed to increase the "combat" characteristics of the vehicle accordingly. The tower received the means to maintain the carbon arc lamps: the operator could bring the electrodes closer together as they burned out.
Modern model of the "E" tank. Photo Panzerserra.blogspot.fr
According to some reports, in the new American project it was proposed to retain the additional equipment of the searchlight, previously proposed by British designers. The floodlight embrasure was to be equipped with a movable shutter-shutter and light filters. The first made it possible to stop and resume the illumination without turning off the lamp. The filters were supposed to make it difficult to determine the real location of the carrier of the searchlights, but at the same time they did not prevent their own troops from observing the highlighted area.
During the modernization, the M4 Sherman tank lost its original turret with cannon and machine gun armament. Nevertheless, the new project of the searchlight armored vehicle still implied the use of weapons for self-defense. To combat manpower and unprotected enemy equipment, tankers could use two M1919 rifle caliber machine guns. One of them was placed in the standard course setting of the frontal sheet, at the starboard side. The second was proposed to be mounted in the forehead embrasure of the new tower. The use of an anti-aircraft machine gun was not envisaged.
The lack of cannon armament and the reduction in manned volumes led to a decrease in the crew. Only three people were supposed to operate the searchlight tank. The driver and gunner were located in their regular places in the front of the hull. The commander, who also served as the operator of the searchlight installations and the gunner, was in the tower. All crew workplaces were equipped with their own hatches and observation devices.
The development of a new project was completed in the spring of 1944, after which one of the American arsenals, with the assistance of the defense industry, rebuilt the M4A1 serial tank. The prototype received the official designations M4 Leaflet (after the American searchlight tank program) and "E". Also, some sources use the name T10E1, indicating the succession of projects. The prototype was to be tested at the Fort Knox Army Base. In May of the same year, a prototype was presented for testing.
Like many other wartime designs, the E searchlight tank passed all the necessary checks in just a few weeks. The tests fully confirmed the calculated advantages of the new model over the existing T10. The use of the chassis of the newer Sherman medium tank provided obvious advantages. The M4 Leaflet featured improved mobility, increased protection and greater ease of use. In addition, by this time, M4s of various modifications had become the most massive tanks in the American army, which was also an important plus. At the same time, the new searchlight tank was in some respects inferior to the previous CDL Grant / T10. The fact is that replacing the existing M4 turret resulted in the removal of the main gun. In the case of the equipment based on the M3 Lee / Grant tank, the turret replacement did not affect the main 75 mm cannon in the hull sponson.
The first version of the British "Sherman" with a CDL turret. Photo Panzerserra.blogspot.fr
Thus, having significant advantages in the mass of characteristics, the searchlight tank based on the M4 Sherman was inferior to the previous type in firepower. The lack of artillery and the use of only machine-gun weapons was a decisive factor. The American military, comparing two original samples of special equipment, came to the conclusion that a well-armored, but poorly armed searchlight tank is not of interest to the army. Moreover, the potential customer considered that the construction of such equipment would be a waste of good and modern tank chassis.
Tests of the first and only prototype type "E" / M4 Leaflet / T10E1 were completed in June 1944, shortly after the outbreak of hostilities in Normandy. The negative feedback from representatives of the military department accordingly affected the further fate of the project. All work on the current modernization of "Sherman" was terminated due to inconsistency with the wishes of the customer. Completion of the existing project using a weapon of acceptable power was not possible. As a consequence, the development of the existing "E" tank was stopped.
It is known that the creation of a searchlight tank based on the M4 combat vehicle was also carried out on the other side of the Atlantic Ocean. Simultaneously with the United States, Great Britain was studying this problem, which created the first projects of such technology. There is reason to believe that the British project was a direct development of the American one, or, at least, was created taking into account the developments on it. As a result, the main features of the architecture of different armored vehicles coincided, but there were certain differences.
British industry built two experimental CDL Sherman tanks at once. Both of them were based on a chassis with a welded armored hull, but the main features of the modernization were borrowed from a foreign project. So, all units of the fighting compartment were completely removed from the hull, instead of which an electric generator was installed, etc. The tower of the first prototype in its design, in general, repeated the American design, but had a different dome. Taking into account the available production technologies, the dome was divided into several cast and rolled parts, assembled into a single unit by welding.
Like the M4 Leaflet, the first variant of the British CDL Sherman had two searchlights placed on the side of the turret. Between their vertical embrasure windows was a machine-gun mount designed for the use of weapons that met the standards of the British army.
The second prototype of the CDL based on the Sherman had a different turret design. Now a curved frontal sheet of large width was used, to which the sides placed at an angle were attached at the back. A rectangular niche was located at the stern. The increased volume of the tower made it possible to equip the commander's workplace in the stern, which made the tower two-seat. The commander could use his own sunroof, equipped with a set of viewing devices. Apparently, the strengthening of the crew by a fourth tanker was proposed to reduce the load on its individual members. The original American project and its version of the British development assumed that the commander would coordinate the work of the crew, control the searchlights and fire from a machine gun. The division of such duties between the commander and the gunner operator could significantly facilitate their work.
Scheme of the second version of the CDL Sherman. Figure Panzerserra.blogspot.fr
Tests of two British-designed searchlight tanks also took place in 1944 and confirmed the conclusions drawn by American specialists. Once again, it was found that the chassis of the M4 Sherman tank provides improved mobility compared to the M3 Lee / Grant vehicle, and also differs from it in an increased level of protection. At the same time, the lack of an artillery gun and the fundamental impossibility of installing it without a serious revision of the project was considered a disadvantage. As a result, CDL Sherman tanks were not recommended for adoption and serial production.
The further fate of the three prototypes is unknown. Apparently, they were rebuilt according to the original designs and transferred to the armies for use in hostilities. Thus, in the configuration of searchlight tanks, vehicles of the E and CDL Sherman types have not survived to this day.
After the unsuccessful completion of the project of a searchlight tank based on the M4 Sherman armored vehicle, the British army abandoned the further development of this direction. The emergence of such a solution was facilitated by the not too great successes of recent developments, as well as the almost complete absence of practical results from the use of sufficiently large-scale technology. For various reasons, the existing Canal Defense Light tanks based on two types of chassis were able to take part in battles only a few times, performing their main functions. At other times, they had to solve completely different tasks of an auxiliary nature.
The United States Army, in turn, did not abandon the original ideas and the creation of new searchlight tanks. The command and designers took into account the shortcomings of the existing project M4 Leaflet / "E" / T10E1 and formed an updated look for a promising special-purpose armored vehicle. With the help of a number of original ideas and solutions, they managed to combine in one project both searchlight installations and artillery weapons. Initially, this version of the tank had the already known designation "E", but later it was given a new name T52. This combat vehicle can be considered one of the most interesting and successful examples of its class.
