In the interwar years, namely in the 30s of the twentieth century, the designers of many countries of the world almost simultaneously decided that their armies needed amphibious tanks.
"Valentine" Mk IX DD.
Only the British had the experience of creating them (the Pig and Medium D tanks), but everyone understood that following their path meant not going anywhere. The fact is that it is not difficult to hang pontoons from the tank. This can be done with almost any tank, the main thing is to attach the mountings. But pontoons are … huge water resistance! You can't do with an outboard motor afloat, it can be carried away by an ordinary current. Of course, the pontoons are simple and, moreover, unsinkable, since it is enough to fill them with ping-pong balls or balsa and they are not afraid of any bullet holes. But this is how much balsa is needed? And then - pontoons need to be transported for tanks. You need a crane to install them! All this must be carried out in a zone subject to enemy fire damage. And if the tank is dropped from the ship? Then the dimensions of the pontoons will require a ramp inconceivable in width, and what about that?
Tank "Ka-Mi" at sea.
This is how the military and the designers of those years reasoned, or something like that. The obvious solution was to give the pontoons a "ship shape". That is, prepare a set of four pontoons for each tank: bow, stern and two "sides". In a number of countries of the world this was tried, for example, in Czechoslovakia, and then in Japan, where later, during the Second World War, a very good amphibious amphibious tank "Ka-Mi" appeared.
Screws of the "Ka-Mi" tank
The tank had an original pontoon arrangement: a front pontoon with a volume of 6, 2 m³, which gave the structure a streamlined seaworthy shape, was solid on the machines of the first series, but then it began to be made of two parts, which, when dropped, were divided into two halves, which facilitated the passage of the tank. The volume of the rear pontoon was 2.9 m³, but both of them were dumped from inside the tank. There was no need to leave it for this!
Tank "Ka-Mi". Side view.
The tank had a hull of considerable volume, which, together with the pontoons, endowed it with excellent seaworthiness. Moreover, he had two screws on the body, but the rudders with a drive were on the pontoon, behind the screws! The pontoons were stuffed with balsa crumbs, so it was possible to drown them and the tank itself only with a direct hit. But … for all its merits, "Ka-Mi" was still too specific. His main goal was to land on the islands of the Pacific Ocean. And again, the pontoons had to be assembled, stored somewhere, hung on the tank.
PzKpfw38t amphibious tank.
The Germans did something similar, preparing for the landing on the British Isles: the Pz. II tank was equipped with a pontoon in the shape of a boat and with a rectangular cutout in the middle. Below the "boat" had reclining supports. When they leaned back, the hull leaned on them, rose (leaning on the stern) and the tank drove out from under this structure. Or drove into it when it was necessary to use it. These tanks even fought, however, not against England, but against the USSR - they crossed the Southern Bug. However, later they decided to abandon these technical tricks.
Floating tanks with a displacement hull, which also appeared at that time, solved the problem of pontoons. But due to the presence of such a body, it was impossible to put either thick armor or solid weapons on them. In addition, they plunged into the water so deep that they could swim only in the quietest weather. So all of these two solutions had serious drawbacks that prevented the use of "amphibious tanks" in combat conditions.
Soviet amphibious tank T-37.
And here a completely unusual idea came to the head of the Hungarian engineer Nicholas Straussler, who moved to England in 1933, where he had clearly more opportunities for work. He thought that the easiest way is to surround any tank with a displacement screen and thus make even the most "non-floating" tank float! The first sample of his device, which looked like a tarpaulin screen on spacers made of metal rails, was tested on the Tetrarch tank in June 1941. Alan Brook, the commander of the metropolitan forces, liked the idea, and he ordered to continue the work.
Already in September of the same year, the Straussler system, which received the name DD - "Duplex Drive" or "Double Drive", since in addition to the tracked drive, his tank also had a propeller drive, it was decided to install it on the Valentine tank. What was captivating in the design was that neither the propeller nor the screen in any way prevented the tank from performing its "work" on land, and most importantly, it did not have much weight. The height of the screen was increased, the thickness of the tarpaulin too, and the thickness of the rubber tubes into which the air was pumped was increased and thereby straightened the screen.
Tests of the new model began in May 1942, and the tank was deliberately sunk with machine-gun fire, figuring out how dangerous it was for it. Finally, the DD system was recognized as fully consistent with the task and began to equip tanks with it. Already in December 1944, the British army was armed with 595 tanks "Valentine" DD, modifications V, IX and XI.
We tried to make the same screens for the Cromwell and Churchill tanks, but both of them (and especially the last one!) Turned out to be too heavy for this. Along with the adoption of new tanks, the means of rescue from them were also worked out, in the event that the tank was flooded during the landing. In this case, the tankers had to put on special breathing devices, wait until the tank is completely filled with water and then leave it through the hatches.
Meanwhile, while the crews of the "Valentines" were being prepared for landing in France, it became obvious that they were, one might say, outdated right before our eyes, and they urgently needed to be replaced. Therefore, it was decided to equip the American Sherman tanks with the DD system. The tank's weight of 30 tons again required improvements. Now the screen has become three-layer at the bottom, then two-layer, and only at the very top - single-layer. Another problem was the drive. After all, the transmission was located in front of it. But even then they found a way out: they put additional gears on the sloths, and already from them they made transfers to the screws. In addition, an electric pump was installed in the body for pumping water. As a result, the speed of the new "DD tanks" increased to 10 km / h. However, the handling was still very poor.
The device of the Sherman DD tank.
To participate in the landing in Normandy, the British attracted LCT landing ships (3), which took on board five Sherman DD tanks instead of the usual nine, and the Americans - LCT (5), carrying four tanks.
The "finest hour" of tanks with the Straussler system came on June 6, 1944. The landing of tanks under enemy fire began at 6:30 am in the Utah sector. The vehicles were landed 900 meters from the coast, but the waves and the current carried them aside for two kilometers, and it turned out that the tanks were in one place, and the infantry, which they were supposed to support, in another!
Beach site "Utah". Tanks "Sherman DD" come out of the water.
At the "Gold" section, some of the tanks managed to land directly on the beach, and that was very good, but the rest of the vehicles landed in the water 4500 meters from the shore! Strong waves flooded many tanks, as a result, out of 29 vehicles, only … two made it to the coast! But the good news is that only five tankers were killed.
British tanks in this sector were launched 600 meters from the coast, but eight vehicles sank. Here, some of the tanks landed directly on the shore, without raising the screens. But … the sand was saturated with water, so many cars got stuck, and when the tide started, they were filled with water.
The Canadians landed in the Juneau sector: two regiments with Sherman DD tanks. Because of the great excitement, they suffered heavy losses and could not fully help the landing party, but it was still tanks, at least a little!
On the "Svord" sector, out of 40 Sherman tanks, 34 vehicles reached the shore, and another five landed directly on the shore. Tanks immediately folded screens and rushed into battle. But then they had to be removed without fail, since the dried tarpaulin was fire hazardous.
The experience of the Normandy operation showed that the system needed to be improved further. The height of the screen was increased by 30 cm, a device for irrigating the screen was placed outside, in case of fire afloat.
This was followed by Operation Dragoon, during which Sherman DD tanks landed in southern France. In total, 36 tanks were landed, of which one was flooded with waves, one hit something under the water, and five were blown up by German mines.
In May 1945, these tanks crossed the Rhine, and because of the strong current, the tanks went into the water above the landing site, and for the sake of convenience, floating LVT transporters delivered special decks there, making it easier for the tanks to get out of the water.
The last operation of these vehicles was the crossing of the Elbe. Moreover, so that some local German sympathizing with the Nazis did not make holes in the screens, all the inhabitants of the village, where they were being prepared for landing, were evicted.
But in the Pacific Ocean, in Burma, the Americans preferred tanks with pontoons (T-6 system), which moved through the water by rewinding the tracks. It was safer that way, they thought, and besides, the tanks could shoot afloat.
Well, and then … Then, as always happens in such cases, there were many proposals for improvement. For example, put rocket boosters on the tank in the lower part of the hull with an inclination of 30 degrees. Their simultaneous inclusion was supposed to add speed to the tank. But … the walls of the screen were bent under the pressure of water. And in general, this is a dangerous business, like this "fly" on rockets.
The tankers wanted to strengthen the armament of the DD tanks, because they could not shoot on the move. What do you want? So here you are: they made a machine-gun mount with two M1919 machine guns, put it on the top of the screen. Swim and shoot! But it showed low reliability, so the matter did not go further tests. They also put a recoilless 94-mm cannon on the screen, but … where can you get the exhaust from it? And they also abandoned it, as well as the periscope for the driver, so that he himself could see everything and steer where necessary.
"Sherman DD" at the Museum in Bovington.
We tried to make the Churchill-Crocodile flamethrower tank floating. But everything rested on the placement of the fire mixture trailer. Making it floating also turned out to be very difficult technically. Finally, in the 59s of the last century, they tried to make the new tank "Centurion" floating. But the "Centurion DD" also "did not go" - the weight for the tarpaulin screen turned out to be too much. Later, similar systems with folding screens were installed on the Strv-103, M551 Sheridan, M2 Bradley infantry fighting vehicles and a number of other vehicles, but all of them no longer resembled Straussler's design. His contribution to world tank building was not small, yes, because without his "DD tanks" the success of the landing in Normandy was not so dubious, but not so impressive, and the losses would have been much greater, but not as great as the contribution the same Christie and our Soviet designers.
