The Largest Security-Cleared Career Network for Defense and Intelligence Jobs - JOIN NOW

Military


Tortoise (A39)

The heavy assault gun Tortoise (A39) is a British super heavy assault gun designed, built and tested during World War II , but never launched into mass production. The machine was designed to solve the problem of the destruction of heavily fortified areas, so in its design mobility was sacrificed for security. Despite the fact that this vehicle is called a tank, its turret doe not rotate, which, combined with powerful artillery weapons and low mobility, makes it possible to rank it as a super heavy self-propelled artillery .

In 1942, the British General Staff, responsible for developing the concept for the development of armored vehicles, showed an interest in the so-called "assault tank" - a heavy armored vehicle capable of acting upon the breakthrough of fortifications and capable of withstanding a large number of direct hits. As a result, several experimental machines appeared, including the Ecelsior A33, the Valiant and the American T14.

In addition there were a large number of projects that did not go further than the drawing boards. Among them was a project prepared by Newffield Mechanization Ltd from Birmingham, which was the AT1 (Assault Tank) with 150-mm armor and a small, pear-shaped turret under a 75-mm cannon or a 95-mm howitzer. The body was similar to that of Valiant, and the suspension was planned to be torsion. The weight was estimated at 45 tons. There were two versions of this project: one resembling a tank, but with a fixed turret; the second is a more squat car with 200-mm armor and with weapons only from a pair of machine guns.

But these projects did not suit the British General Staff, which demanded that a six-inch mortar and a flamethrower be mounted on the roof of the hull. On May 31, 1943, a new project appeared with an extended hull hanging over the tracks. The level of protection remained the same, and the armament changed, making two twin machine-gun installations in turrets on the roof, a 20-mm cannon on the left of the frontal sheet and a six-pound on the right with the Molins automatic loader modeled on the 3.7-inch anti-aircraft gun. The second design was a more squat vehicle with 200-mm armor and with weapons only from a pair of machine guns.

After several reworkings of this project, on June 26, 1943, AT10 appeared. This version had a six-pounder, paired with a machine gun - on the right, and a 20-mm cannon on the left. On the roof of the hull, behind the commander's turret was a twin machine-gun unit, designed for good back fire angles. The maximum armor thickness has now reached 225 mm, the weight was estimated at 45 tons, the height of the hull was 2.28 meters. Newffield Mechanical Ltd. considered this combination of protection and armament to be sufficient and began to produce a full-scale wooden model.

However, the General Staff demanded that the company put on "Tortoise" - as the project was now called - a 75-mm cannon with a high initial velocity of the projectile. At Newffield, they calculated that the necessary lengthening of the hull would lead to weight gains of up to 65 tons, nevertheless, Sir Miles Thomas from the management of Newffield (later the head of the armored vehicles department in the Supply Ministry) concluded that it would not be difficult to install a new 17-pound cannon on the tank. the offer was accepted.

The new project AT13 appeared on August 13, 1943 and already looked like the "Tortoise" which was built. But even after that, the gun was shifted to the right, and the 20-mm machine gun - to the left, although the 95-mm howitzer was planned instead. The suspension was a series of two-wheeled carts with a 32-inch caterpillar. Couples carts slightly overlap each other. The outer wheels of the carts on each side could be dismantled together with the tracked screen, which allowed the tank to pass in width across the Bailey Bridge. This resembled a similar operation with the "Tiger" during its transportation by rail. On the American giant T28 "cousin" of the Tortoise the issue was solved even more radically - the external pair of tracks was dismantled.

At the same time, the issue with the propulsion system was resolved. For the AT10, the Ford engine was planned, but which one the V8 GAA series or V12 was not yet clear. At AT13, it was decided to put a Rolls Royce Meteor with a Merritt Brown transmission. The project had one detail that could totally surpass all other technical problems - the designers of Newffield planned the whole-cast Tortoises building. Although it represented undoubted benefits in terms of body ballistics, doubts arose as to the ability of the plant to process this desing. It was the main problem, but Miles foresaw other difficulties: would the Tortoise be too heavy for existing transporters?

By December 1943, the layout for the AT13 project was almost ready, although the last three times changed slightly. So for AT14 instead The 20-mm cannon and machine gun on the left had only one machine gun installed - the weight was reduced to 60 tons. At the AT15, the gun was shifted to the center of the hull, and at AT15A the cabin of the hull was increased, bringing the weight to 65 tons. At this stage the General Staff, which demanded to install a new gun, and the 17-pounder was replaced by a new 37-pounder cannon, which was an anti-tank gun based on a proven 3.7-inch anti-aircraft gun. After the decision was made, the project was redesigned as AT16 and a non-alloyed steel prototype was ordered.

In February 1944, the next step followed - it was decided to order 25 tanks, to which the General Staff gave the designation A39, without waiting for even a prototype. This trick, tried earlier in Churchill, led to a sad result. Even at this stage of the work it was clear that deliveries could not begin until September 1945 - an estimate that should be brought to life.

In the meantime, two more projects were prepared - AT17 and AT18. Both used the same chassis and differed flamethrower mounted on the gun. Virtually the entire combat compartment was occupied by four 610-l tanks with incendiary mixture, between which there were seven high-pressure cylinders providing the release of fire mixture. At AT17, one flamethrower was in place of the gun, and the other in the machine gun turret on the roof of the wheelhouse. AT18 had a flamethrower instead of a gun, with the removal of the frontal bullet meta. Both projects did not go further than drawings.

In November 1944, another "competitor" appeared - SP4. It was a tank with a turret mounted 3.7 mm cannon on the A41 chassis (the Centurion), which was implemented only in a wooden model. By that time, it turned out that the characteristics of the gun can be improved by replacing the 37-pound projectile with a 32-pound projectile. It was declared that with it the characteristics of the gun were surpassed a whole 25 times higher.

With the end of the war in Europe, interest in the "Tortoise" began to decline rapidly. Plans were already being made for a new generation of combat vehicles, among which the A39 looked like a dinosaur. The order was reduced to 12 vehicles. In February 1946, the Defense Committee decided to halve the order again, up to 6 vehicles at a price of 141,666 pounds each. In fact, five tanks were completed,

The "Tortoise" hull was welded from cast parts and rolled sheets of armor. The largest casting was a cabin without a roof with a thickness of the frontal part up to 230 mm. The roof was a rolled sheet. Another molded part in the frontal part protected the transmission. The engine compartment was welded from rolled sheets of armor and hung over the tracks. Laying of 3IPA was in the right fender, in the left - the charging unit and batteries. The lower part of the hull was made of rolled sheets of armor, with additional protection in the form of heavy side screens. The suspension was torsional, although it looked like a Sherman chassis.

Each wheeled cart (four on board) had two pairs of rollers. The torsions were grouped under the floor of the cabin by four, so that for each side carriage there were two torsions. In most cases, the roller trolley has one axle and its wheels move in a vertical plane at the same time, but on the Tortoise, each roller of the trolley also had an independent suspension. This was envisaged at the project stage at the same time with the possibility of removing the outer pair of rollers of the trolley, to reduce the dimensions of the tanks during transportation, but at the same time this suspension reduced the lateral load on the trolley characteristic of the chassis with wide tracks.

It should be noted that there was no provision for any dismantling of other equipment that would reduce the weight and size during transportation. What they wanted, they got - the possibility of transportation by rail, loading through the ramp of amphibious vessels and movement on flooded bridges had to be discarded.

The tracks of the caterpillar were molded of margon steel and had a centering ridge. The width of the tracks was 32 inches, each link was connected by two pins to meet each other. "Tortoise" was a rather rare among British tanks scheme with the front leading "asterisk" in the rear engine. The caterpillar had six supporting rollers on the side - two on two central shafts and one on the front and rear.

The propulsion system consisted of a naturally aspirated Rolls-Royce engine, the Mk.V Meteor - a 12-cylinder, V-shaped, 650 hp. On the sides of the engine were put two fuel tanks - big on 390 liters on the right and small 245 liters - on the left. On the left was also located the oil tank, which occupied the remaining space. The radiators were in front of the engine, and the exhaust pipes were collected in a large muffler that ran along the entire engine compartment. The tank also carried a charging unit of the four-cylinder Morris-8 engine, which worked directly on the generator. The engine was included in the cooling circuit of the main engine, and the exhaust pipe with a silencer was taken out of the conning tower.

The engine worked on the gearbox through the Bord & Beck clutch and three shafts combined in a common pipe. The gearbox was a Merritt-Brown H51D, providing through a separate reverse six speeds forward and backward and having on-board brakes for driving along the course. This gearbox allowed the tank to turn on the spot. After testing the prototype P1 in the transmission made changes, but what is not known. One of the most interesting features of this tank, the Tortoise, was then considered to be a tank, albeit very specific, but not self-propelled - there was a fighting compartment that housed a crew of seven. The crew included the driver, who occupied the place to the right of the gun, the arrow of the frontal machine gun - to the left of the gun, another shooter was behind the driver, the commander was sitting to the left - behind and above the first gunner. Thus, four crew members were located on the sides of the cabin, making room in the center for artillery crews. The gunner of the gun was located to the left of the gun, and two loaders - behind the gun.

There was an interesting problem with the latter. The gun was designed for separately loading projectiles and charges were stored separately. A small number of "finished" shells were stored on the rear wall of the conning tower in separate canisters, and most of the ammunition was located under the floor of the crew compartment. The problem was: should the loaders have to separately send a projectile and a charge case into the gun, or did one of them have to load the gun, and the other only have to operate the lock? The latter was the standard practice of English gunners, but careful timing showed that the first loading scheme adopted on the Tortoise is more preferable.

The 32-pound (3.7-inch-94-mm) projectile initial velocity was 880 m / s, and the ammunition included armor-piercing and high-explosive shells. The gun was mounted in a ball bearing with a diameter of 24 inches, providing + 18 -10 declination and 20 degrees horizon in both directions. The gunner's sight was mounted in a separate ball mount to the left of the gun, but was tightly connected to the gun itself. The front shooter had at his disposal 7.92-mm machine gun, also in a small ball installation with declination angles of 35. Two more "Demon" were in the upper turret with a circular shelling. They had declination angles of + 15-10. The need for a last machine gun installation was questionable, at the same time it represented a certain danger to the radio antenna and the compass, which were mounted on the roof of the hull, not to mention the crew members.

Since the entire roof became a "zone of fire", the machine gun sparks were equipped with a special device that prevented the destruction of equipment on the roof of the hull. In addition, each hatch was equipped with a special switch that blocked machine-gun fire when the hatch was open. The descent of machine guns for this reason was made electric. Machine gun control (in the vertical plane) was carried out using a knob with two electric trigger buttons. For this installation, specially prepared guns were required, and not only for security reasons, the usual training did not help to eliminate the delay in such a constrained installation.

The commander also had at his disposal a rotating turret with viewing devices and a binocular periscope movable in a vertical plane. The latter, through repeaters, was connected with the gunners gun sights and the upper gunner. On the turret of the commander, was mounted a standard, six-barrel smoke grenade launcher, which had thus circular fire. Two more such grenade launchers were at the corners of the front sheet of the conning tower. To the left of the driver's hatch, a two-inch grenade launcher was mounted in the mobile unit. The drivers place would have seemed familiar to anyone dealing with the Centurion, although the former was located above and to the right.

However, if the person did not have special training, he would not feel very comfortable in this place - the control of the tank was shifted to the right, so that the driver had to sit at some angle to the direction of travel. In addition, if the driver drove the tank through the open hatch and the seat was therefore raised, it was difficult to reach the pedals. When fully equipped, the N 19/38 radio station (on the left, between the commander and the shooter) was installed on the Tortoise, providing both external and internal communications, as well as communication with an infantry, worn radio station, fortified by the chopping of the tank. The communication could be carried out by the commander and the driver.

The "Tortoise" was listed in the documents of the Royal Armored Corps as a tank. At the same time, it could be considered an anti-tank self-propelled gun. In this case, the "Tortoise" came under the jurisdiction of the Royal Artillery, and when in the summer of 1949 the P1 prototype was sent to fire tests, it came to Lakhill under Salisbury Plain - the heart of the "land of artillery". By that time, it was clear that, as a tank, the Tortoise would not be accepted, and the artillerymen decided to try the tank to work out future requirements for anti-tank self-propelled guns.

But there was no chance to test it. First, the firing squad officer responsible for working out the shooting parameters calculated that the firing range, even direct fire, is too long to ensure safety outside the range. Then the Military Office decided to transfer the self-propelled anti-tank artillery to the Royal Armored Corps. As a result, the "Tortoise" was taken to Lulworth, near Bovington, to the tank school of artillery preparation; where there was enough space for firing (called the English Channel) to ensure safety when the projectile was out of range.

Tankers decided to test for the future features of separate loading and at the same time compare the ways of loading the gun with those adopted in artillery. For this, the crew was staffed from both tank crews and gunners. For comparative tests in the Lulworth was driven the Centurion-III. Since the 32-pound has already been tested for accuracy and armor penetration, there was still time for the trials, which gave the same results as the previous tests.

Although the fate of Tortoise was actually resolved with the end of the war, and they were not going to take it into service, two tanks were used for tests in Europe. In April 1948, it was decided to send P4 and P5 to Germany in the first place to check the possibility of transporting such large tanks within the British occupation zone. The start of work on a new series of heavy tanks FV200 was taken into account, since it was clear: where the Tortoise will pass, troops could "push through" anything. It was obvious that with a width of 3.9 m the tank could not be transported by rail, and with a combat weight of 80 tons it would flatten any transporter.

Specially for this purpose, a five-axle transporter was designed at the Cranes of Derehem. It was intended to send two samples to Germany to test them in various road conditions, and conduct live fire tests on Belsens live targets. Despite the complexity of the task, Major Garnett, who was responsible for carrying it out, was notified only for two weeks, as a result of which he was forced to recruit his team hastily. For towing a conveyor with a tank - weighing about 120 tons - it was decided to use two Diamond-T tandem tractors. Thus, the total weight of the train was 155 tons, and the length was 28.5 m.

Three years after the end of the war, the British occupation zone of Germany was still a ruin. The few remaining bridges were in too poor condition to accept such a load, while others destroyed during the war were replaced with temporary ones, so that not only Bailey bridge could not accept the weight of the tank. Moreover, all these bridges were too narrow. So when crossing the Bailey bridge, there would be only a few centimeters of free space. As a result, before leaving Britain, the crews trained hard on an unloaded conveyor, which was not any easier.

Apart from the autobahn - the pride of Germany - the rest of the roads were in poor condition, and most of the minor roads did not even have a hard surface. Some roads had only a narrow strip of coating, on both sides of which there were wide dirt lanes. In addition, many cities and villages in Germany had a central street with a cobblestone pavement, which was damaged during the passage of tracked vehicles. Fortunately, there were not many steep climbs, to overcome which required to change the slope of the trailer, for which there was a set of wooden wedges. In this, the tank test team of the British Rhine Army had six officers and 55 privates, including crews from tank crews and gunners, supply and repair personnel.

The British Rhine Army provided an escort of military police on jeeps and motorcycles along the route. As elsewhere, the convoy was accompanied by five more Diamond-T tractors and a whole fleet of conveyors "B". The training was provided by the test institute of armored vehicles from Chertsey, including loading and unloading of tanks on the conveyor and transportation. Given that the transporter was manageable but tended to skid when cornering, the two drivers of the train required particularly synchronous work. The driver was responsible for driving and using conveyor brakes, and the second driver followed the conveyor engine and switched gears in sync with the first. There was an intercom for communication between the drivers, but, with the exception of driving at night, they preferred hand signals.

Problems for the test team began in England. Initially, they planned to use a tank landing ship (LST) for transportation, but it turned out that not a single gangway could withstand more than 65 tons. They had to choose an ordinary merchant ship with a large cargo hatch. Loading was carried out in the Royal Albert Dock with the help of a 150-mt floating crane. But even this was a problem - the trailer did not have lifting clips that had to be welded urgently in place. After removing all the equipment from them, they were loaded using a grid. The escort arrived in London at night, from where early in the morning on Tuesday, May 25, 1948, the ship slowly moved down the Thames, heading for Hamburg, where she arrived on Thursday. Here the technique was unloaded again using a floating crane, and the convoy moved to their temporary camp.

Officially, the tests began on June 1st. Their description would take too much space, but in general it can be said that the tests mainly consisted in transporting tanks across Germany. From the beginning, the convoy arrived at the training ground near Belsen, then to Hannover, then through Bad Oinhausen to the training ground near Paderborn. From there, two convoys of tanks on the autobahn were transported to Gamm, and then back to Hanover through Minden and Neinburg, and then back to Belsen and Hamburg. The full test report on the Tortoise was published by the British Rhine Army in October 1948. It described the transport tests in detail, as well as a number of other tests.

According to the report, the convoy covered 1040 km, of which 160km the tanks moved under their own power. The maximum speed reached 19 km / h, but the average was much lower, with the exception of autobahns, since on other roads it was necessary to stop oncoming traffic. Delays were also caused by bridges. Another preliminary exploration of the area before the tests showed that only a few bridges along the route would be able to withstand the weight of the train. Therefore, it was common practice to unload the transporter, the tank slowly crossing the bridge under its own power, after which it was loaded onto the transporter again. In the ideal case, it took just 15 minutes. Sometimes, if the carrying capacity of the bridge was insufficient, it was necessary to make a detour. In one such case, under the Spreza had to cross the railway, for which it was necessary to lay a special coating in order not to damage the railway track, but even such a complex operation took only 35 minutes from unloading to loading.

The main problem was narrow roads, mainly due to roadside trees, ditches and too soft cover. So in Celle had to unload the tanks, and they followed the course of the conveyors through the winding pavements. On the whole, this showed that two heavy tanks would not do much harm to the city pavement, but in the case of a whole regiment it is another matter. Already one sharp turn of the tank was enough to turn out all the paving stones. The greatest slope on the route of 7.5 was overcome on the autobahn near Bckeburg. In general, transportation was recognized as successful, especially the work of conveyors, with which there were no problems at all, was noted.

During the tests, both tanks received personal names, but due to the poor quality of the photographs, only the name P5 Adventure was established. This tank was used for fire tests near Belsen. Shooting was carried out on the shields at a distance of up to 2000 m, particularly noted the good accuracy and a good impression of the new gun on the crews who are accustomed to a capricious 17-pound. Then fired at the decommissioned Sherman, whose frontal part was simply torn to shreds. Finally, the shooting was conducted on the "Panther" - judging by the photos, it was one of the vehicles assembled after the war under English control. Apparently, this is a model G with a frontal part of the type of tank, exhibited in Bovington. With 1230 m projectile with "Tortoise" struck frontal sheet "Panther", snatched a piece of the roof over the driver's seat and even tore off part of the mask of the gun, which was found 5 meters from the target.

According to the test results, representatives of armored forces and artillery rated tank very highly. Tankers, who fought in Europe, noted that such a gun would give them advantages over any German tank of 1944. However, some observers were less optimistic, and test reports were full of such phrases: "... lack of circular shelling", "." ..too heavy "," ... too slow "," ... mind-blowing problems with transportation "," ... split loading" - all with varying degrees of doubt! The fate of "Tortoise" was decided ...

Tortoise



NEWSLETTER
Join the GlobalSecurity.org mailing list



 
Page last modified: 10-12-2018 18:40:00 ZULU