The Tumbleweed Tank was the brainchild of a Texas inventor, who chooses to remain anonymous. This is probably because he doesn’t want anyone to know that his only invention was a giant metal ball with guns sticking out of the side.
(Source Military History)
Apparently, the ball-tank would have circular traction cleats on two cup-shaped halves that would rotate to propel the tank. Soldiers inside the sphere would fire machine guns from a stationary cab, and a heavy driving motor would be placed on the floor to prevent unwanted rolling. What this tells us is that the Tumbleweed Tank was susceptible to haphazard rolling.
The ball-shape, according to the inventor, would easily deflect incoming fire, and even absorb missile damage better. However, were not sure how well it would deflect the onslaught of ball jokes.