From the files of the incredibly strange in armor warfare comes this little beauty...
The Ball Tank Concept
The "Ball Tank" was a concept from an engineer in Texas, United States.
The above drawing was featured in the July 1936 issue of Popular Science Magazine. The Ball Tank was described a high-speed "tumbleweed tank" with a spherical hollow steel driving cab, enclosed by a rotating outer shell. The inventor stated that the tank’s spherical shape presented the "smallest possible target for enemy bombs or shells, and all but direct hits would glance off its curved sides."
Far fetched? Well the photos below indicate some one took the design serious.
The Tank Ball Reality
Very little is known about this WWII "spherical droid" - captured on the Eastern Front (in Manchuria) in 1945 and currently on display in Military Museum in Kubinka, Russia. The Soviets claimed it was German built, although no proof has ever been offered and no explanation what German equipment, however weird, was doing in Manchuria.
The Tank Ball shown above had 5mm armor protection, driver's cab and was powered by a two-stroke one-cylinder engine. Conjecture is this machine was used as a reconnaissance vehicle, but no proof of that exists either.
You can't make this stuff up.