Origin - Dd Tank

He began with a Tetrarch light tank. His idea was simple but audacious: make a tank that could swim. Not float like a boat, but propel itself through the sea using its own tracks. The key was displacement. He bolted a rectangular, collapsible canvas screen to the tank's hull, held aloft by rubber tubes. When raised, the screen acted like the sides of a ship, pushing water away and allowing the 7-ton tank to bob just below the surface, with only a small air intake and an exhaust pipe visible.

Straussler, a naturalized British subject and a genius with mechanical things, had already made a name for himself with armored car designs. But this was different. He wasn't building a weapon. He was building a ghost.

The War Office was skeptical. "Swimming tanks?" a general scoffed. "Next you'll want flying horses."

He went back to the drawing board. He replaced the rubber tubes with a system of thirty-six hollow steel pillars. He used stronger, waterproofed canvas treated with wax and linseed oil. The drive mechanism was refined: the tank's own sprockets would turn a pair of propellers mounted at the rear, disconnected from the tracks. dd tank origin

It worked.

Straussler just nodded, spitting out brown river water. "No," he said quietly. "It's a theory that hasn't worked yet. There's a difference."

The first test was a disaster. The canvas ripped. The tank took on water. It sank to the bottom of the Hamble River like a dead beetle. He began with a Tetrarch light tank

But at Sword, Juno, and Gold beaches, the crews remembered Straussler's lesson: Don't fight the sea. Borrow its skin. They launched closer to shore. The canvas screens billowed. The little propellers whirred. And out of the grey, choppy water, the tanks rose like prehistoric beasts crawling onto land.

On a cold November morning, Straussler stood on the bank of a placid, man-made lake in Surrey. A Valentine tank, its canvas screen raised like the frill of a startled lizard, sat on the concrete ramp. The crew inside—three nervous volunteers—gave a thumbs up.

His assistant, a young Royal Engineer named Corporal Bill Jenkins, fished him out. "It's a coffin, sir," Jenkins said, shivering. The key was displacement

The problem was beaches. Any invasion of Nazi-occupied Europe would require landing tanks directly onto shore. But landing craft couldn't get close enough without being blown out of the water. Tanks launched too far out simply sank like stones.

But Captain John J. "Jock" McNeil of the 79th Armoured Division saw the potential. He was one of the few men who understood that breaking the Atlantic Wall would require bizarre, unnatural machines. He gave Straussler an ultimatum: one working prototype in thirty days.

The tank rolled into the water. For a sickening moment, it listed to the left. The crew inside felt the cold seep through the hull. But then, the canvas billowed out, the air pockets caught, and the tank leveled. The little twin propellers bit into the water. Chugging like a tugboat, the Valentine moved away from the shore.

Nicholas Straussler never saw the landings. He was in a workshop in Berkshire, covered in oil, already sketching a different kind of flotation device for a different kind of war. When the news came, he simply said, "Good. Now, about the problem of mud..."