Skeleton Tank (USA)

The Skeleton Tank was an experimental prototype tank built in 1918 by the Pioneer Tractor Company, Winona, Minnesota for $15,000 ($ 244,000 in 2018). Prototype was ready for trials by October of 1918.[3]Designed with several innovative features, some of which were controversial at the time, the Skeleton Tank project did not proceed beyond the single prototype tank.The objective of this prototype was to develop a lightweight vehicle capable of crossing wide trenches in a manner similar to the then-conventional heavy British tanks. Unlike the British tanks with their fully enclosed chassis, the Skeleton Tank achieved the requisite lozenge shape by supporting its tracks with a skeleton-like framework formed from ordinary iron pipes joined by standard plumbing connections. Suspended between these track frames was an armored fighting compartment carrying a machine gun turret. The engines were also housed in this armor-protected box.

This arrangement dramatically reduced the weight of the vehicle as compared to the larger British and French tanks while preserving the trench-crossing capabilities of those machines, and there was a belief that most enemy bullets and cannon rounds would pass harmlessly through the structure. However, it eliminated the possibility of mounting weapons in sponsons as in the British tanks and thus limited the armament that could be carried.