Chapter 427: Landing Preparation (2)
After the defeat at Dieppe, the Allies soon discovered that they had made a big mistake in the timing of the tank landing: in order to allow tanks and infantry to attack the beach at the same time, the Allied tank landing ships had to get as close to the beach as possible before letting the vehicles out of the cabin. But such a ship with a displacement of 200 tons and 9 tanks inside would undoubtedly become a live target for enemy artillery fire.
At such a close distance, even light artillery can easily cause heavy damage to the landing ship. Once the ship is damaged, it means that all the tanks on the ship cannot be on duty on time, and a lot of combat power is lost in vain. This problem can be solved by placing the tanks in small landing craft, but the Allies do not have so many landing craft to call. The best way is for the landing ship to open the cabin and release the tanks while keeping a distance from the beach, allowing them to swim and land by themselves.
However, the defense capability of light amphibious tanks was too poor to resist the attack of anti-tank guns, and the medium tanks with better defense capability were too heavy. For example, the combat weight of various types of American Sherman tanks equipped by the British Army at that time was about 30 tons, and the domestic Churchill tank weighed 38 tons. Once it entered the water, it would sink to the bottom like a weight.
So Hobart turned his attention to the "double propulsion" device (Duplex Drive, abbreviated as DD) developed by inventor Nicholas Straussler.
Straussler (1891-1966) was born in Hungary and designed a variety of folding floating devices before obtaining British citizenship in 1933. The DD device is designed to provide floating capabilities for large vehicles including tanks. Its main structure is a folding canvas waterproof curtain tightly installed around the upper body of the tank. When the waterproof curtain is raised as a whole, it can provide buoyancy and sealing waterproof protection for the tank. At this time, even if the tank is under the waterline as a whole, it will not sink or take in water. In addition, the DD equipment also provides a propeller propulsion device directly driven by the tank engine, which allows the tank to travel at a constant speed in the water.
In June 1941, the British army tested a Sheriff airborne tank equipped with DD equipment at the Brent Reservoir, and the result was a great success. The DD equipment was finally finalized in June 1942. At first, the British army chose the Valentine infantry tank with a combat weight of 18 tons as the main carrier of the DD equipment. A total of 650 Valentine III (with 2-pound guns) and VIII (with 6-pound guns) were converted into Valentine DD tanks. But Hobart believed that this old tank was outdated and decided to use the newer American Sherman series tanks as the new DD equipment carrier.
In 1943, the first Sherman tank was modified and equipped with a foldable canvas canopy and a ring-shaped rubber air hose frame. This device was installed on a boat-shaped platform welded around the tank body. The working method is to inflate the rubber frame through the air pipe. As the gas is filled into the rubber frame, the tarpaulin is propped up to the high point above the turret, and the bracket locks the tarpaulin. The operation is completed by the tank crew and can be completed in just 15 minutes on the deck of the tank landing ship. The tank can be launched after the tarpaulin is unfolded. The unfolded tarpaulin provides nearly 1 meter of freeboard space. The entire vehicle is powered by two small propellers installed at the rear of the vehicle body. The direction is controlled by swinging the propellers. Additional steering is achieved by a small rudder installed outside the turret controlled by the commander.
The speed of the tank on the water is slow, which depends on the sea conditions. Sea conditions above level 5 mean a higher risk, but this limitation is not taken seriously, and catastrophic accidents often occur as a result. When the water depth reaches 5 meters, the tarpaulin can be retracted, and then it is the time for the "DD Sherman" tank to show its prowess, and its main gun can fire.
The "DD Sherman" tank does not have a heading machine gun, but its artillery provides powerful and direct fire support for the British soldiers in the landing operation, especially in the Normandy landing battle on June 22, 1944. Once out of the water, the propeller at the rear of the body can be retracted, and it is a standard main battle tank away from the beach.
Germany also studied amphibious tanks in World War II, and there was an amphibious version of the No. 2 tank, but such a light tank with weak protection and weak firepower did not meet their requirements, and they wanted to send the main tank up.
I don’t know which talent in the German Army had a brain hole after seeing the Navy’s submarines, and even had a whimsical plan to let the tank swim across the English Channel. To be honest, this idea is as unbelievable as someone telling you that the sun will rise from the south tomorrow. However, the top leaders of the German Army and the mustache may have been dizzy with the war situation, and actually approved this plan. And the German engineers not only did it according to the requirements of the military, but also succeeded.
They planned to modify the No. 3 tank or the No. 4 tank so that it could move underwater. Finally, German engineers chose the Panzer IV because it was the largest, most powerful and best-protected tank in Germany at the time. Engineers chose the D and E models of the Panzer IV as the basis for research and development, simply because they were the models with the largest production.
Their modification of the Panzer IV was to seal the tank's main gun and add a protective cover. Other places where leakage might occur, machine gun firing ports, observation windows, etc. were sealed with waterproof materials. The hatches, turrets and armored parts of the body were equipped with rubber gaskets and drainage covers. In terms of appearance, compared with the ordinary Panzer IV, there is not much difference except for the additional fixed ventilation pipes and pipe support frames.
However, unlike the original Type 4 tank, it has an additional snorkel and underwater navigation compass. The snorkel is equipped with a sealing cap and the exhaust pipe is equipped with a one-way exhaust device. When the tank dives, air is introduced into the cabin through the snorkel. The ventilation equipment consists of an 18-meter-long ventilation hose and a buoy at its front end. The buoy of the ventilation equipment is equipped with an air intake and a radio antenna, and the air input into the tank cabin enters from the buoy. When the diving tank moves in the water, its buoy floats on the water surface, and the air in the car is supplied through the buoy port.
After a major transformation, this diving tank can reach a maximum depth of 15-18 meters underwater. And it can also move along the seabed underwater. In this way, it seems that this tank already has combat effectiveness. As long as a few armored regiments are gathered, these diving tanks can go to capture Britain.
It's just that ideals are full and reality is very skinny.
First of all, this unfortunate snorkel is completely on the water surface by the buoy. If the buoy is flooded, the water will flow into the tank along the snorkel, and the people in the car may be drowned. Secondly, this tank can only move underwater for a maximum of 30 minutes. If it exceeds the limit, the carbon monoxide concentration in the car will be too high, which may cause poisoning of the crew members. If it exceeds the specified value, a large amount of carbon monoxide will be in danger of explosion.
In addition, although the theoretical diving depth of this diving tank is 18 meters, it must be when the water surface is stable. If the wind and waves are too strong, it is estimated that the tank will be easily overturned by the water flow. When in use, the diving tank must be transported to the nearshore waters by barge before use, and then launched not far from the target coast. The water surface must be flat sand, otherwise the tank will directly anchor. In addition, its field of vision in the water is very limited. If it encounters an obstacle, it is estimated that it will be difficult to bypass it. If it fails to bypass the obstacle or anchors, it will stay where it is, and eventually become a real diving tank that can never come up.
In addition, even if it really landed, there was no way to fire immediately. Since the tank needed to dive deep, the Germans used a lot of sealing materials to waterproof it when building the tank, which resulted in the weapons on the tank not being able to be used immediately after landing. Because some important parts, such as artillery, machine guns and observation devices, are filled with a lot of sealing rubber and foam materials.
The tank's snorkel must also be removed, because these 18-meter-long hoses greatly hinder the normal progress of the tank, and the exhaust pipe at the rear also needs to be reinstalled. Therefore, the crew also needs to remove these diving equipment before the tank can exert its true combat effectiveness. And by the time all this is done, the enemy may counterattack. So this weapon is not very easy to use. It can be said that it is a bit sensational.