Sunday 3 January 2016

World of Tanks Armoured Fantasy: Screw Drive

The idea of a tank without tracks and wheels sounds absurd. Even more absurd is the idea of a vehicle driven by something that looks like a huge screw affixed under the hull. And yet, among the many ideas sent to the Department of Inventions, the screw drive was one of the most reasonable and viable.

Grigorenko's "Driving Worm Gear"

On May 9th, 1944, exactly one year before Victory Day, Guards Senior Technical Lieutenant Boris Grigorenko deposited his invention into a field post box. The address was brief: "Moscow - Kremlin". The author proposed a new type of suspension that would not be troubled by "loose mud, swamps with vegetation, rivers, lakes, sands, snows, and others". He asked for help in building his prototype and testing it against the fascists.

Grigorenko called his implementation of Archimedes' Screw a "Driving Worm Gear". The vehicle would be driven by solid metallic rods with a threaded surface. "The driving worm gear is a replacement for wheels, tracks, bogeys. When the worm gear spins, the tank moves forward due to its thread". According to the author, this would give the tank optimal off-road performance. Grigorenko also included shock absorbers for travelling on a paved surface, adding rubber rollers.

He admitted to being an amateur: "I am not a technician or a draftsman, and I do not have the opportunity to schematically describe everything on paper." The author hoped that the idea would be worked on in Moscow by specialists and that he would be invited to supervise.

Grigorenko wrote little about the details of his invention, but included a few simple sketches. He proposed several variants of his worm gear. The first was an all terrain vehicle with a boat-like shape. The engine and transmission were in the front, along with the front deck and the driver's cabin, covered in glass, according to the sketch. A tarp covered platform behind it could hold up to 2 tons of cargo. Next, the author drew a GAZ-AA truck, replacing the rear wheels with his worm gear. The only techncial specification he wrote on the sketch was "Yaroslavl rubber factory USSR" on the tire. Lastly, the "driving worm gear" could be used on a tank, but that sketch was very abstract and had no comments at all.

The response of professionals is not known, as it was not preserved in the archives.

Beketov's Screw Tank

Engineering technologist V. Beketov made more progress in this area. In August of 1942, he sent his screw tank project to GABTU's Department of Inventions.

The description of the vehicle was prefaced with a discussion of what the ideal tank should be like. High firepower, speed, maneuverability, stability, but most importantly, a lack of weak points. The weakness of all tanks is the running gear, and Beketov thought he found a way to make it safe. "The main idea for solving this issue is a running gear that is, itself, a part of the armoured hull." The inventor proposed a vehicle that, in itself, was one big running gear. Instead of a tracked vehicle, he made a screw-driven one.

Beketov's tank consisted of a hollow armoured cylinder with an engine compartment and a driver's compartment inside. The rapidly spinning cylinder would propel the tank, but this was not enough according to the author. He wrote: "This idea is realistic only if two armoured cylinders are rigidly connected together and spin in opposite directions." The tank would be made out of steel pipes of various sizes and lengths.

Two of them, making up the hull, were 6.2 meters long and 1.2 meters in diameter. The minimum thickness of the armoured walls was only 10 mm. The pipes ended with cones. Four thickly walled pipes connected the two halves, and two more allowed the crew to travel between them.

The cylinders were split up into parts with bulkheads. "The bulkheads separate the compartments: engine, combat, and control. Aside from that, they make the cylinders more robust." In an attempt to decentralize the important parts of the vehicle, Beketov put the engines in the center. The engine compartment would be accessible from both sides. The author proposed installing the engine on a special metal frame. Fuel and oil would be stored underneath it. The fighting compartments were located under each of the four turrets. The author did not specify which turrets he would use, only that they would have 45 mm guns and machineguns. "The use of four turrets allows for the possibility of powerful defensive fire. Two turrets can fire per side, and when necessary, three or even all four turrets can be aimed at the same target."

The main feature of the design was the screw drive. The author wrote much about its benefits, such as the automatic adjustment of the ground pressure. It would be minimized when moving on snow or swamps, but maximized on hard surfaces.

Beketov described the characteristics of his creation in great detail: 7 meter long hull, 2.3 meters tall, 3 meters wide, and weighing 28 tons. This mass was not surprising considering the conservative armour thickness. A duo of 250 hp aircraft engines would propel the tank to a speed of up to 50 kph. GABTU's response to this project is also not known.

Sending their ideas for review, both inventors thought they made a discovery. Meanwhile, the idea of a screw drive was older than both of them. The first prototypes of screw driven vehicles were built in the 19th century, and in 1900 inventor Franz Dergint received a patent for a sled propelled by screws.

A whole series of screw driven all terrain vehicles was made after WWII. Some of them are still used today, irreplaceable for search and rescue missions in difficult terrain. This means that some fantasies can be made a reality and used to help people.

Original article available here.

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