In World War II, New Zealand wanted a tank, but none of their allies had any to spare. So they made their own, with a tractor, corrugated iron, a mattress, and a postcard.
First, a little background. If you’re not familiar with New Zealand, one of the culturally-defining characteristics of a stereotypical New Zealander is a willingness to improvise based on whatever is available. In the local parlance, this is a “number 8 wire” mentality. It’s a point of pride and sometimes a very useful skill. Sometimes.
I have written before about inflatable tanks. Absurd, but they actually achieved their desired outcome. The Bob Semple tank was worse. Much worse. Perhaps the worst tank ever made.
The concept was simple, and made sense at the time: create an exoskeleton that could be quickly and easily attached to existing machinery in the case of attack. New Zealand had plenty Caterpillar D8 tractors that they could use as the base.
First problem: the designers had no schematics or plans. So they decided to improvise based on a single postcard showing a similar American tractor-tank. Second problem: no armour was available. So they made armour out of corrugated iron – which, by the way, is very unlikely to be bulletproof. Third problem: no tank guns or turret guns. So they attached six light machine guns. That introduced the fourth problem: no place for the gunner to sit while they fired the machine guns. So they put a mattress down on the tractor’s engine for the gunner to lie on.
The end result was… awful. It was top-heavy (much like the ship from an earlier post), slow, heavy, and vibrated so much that it would be unlikely to ever actually hurt anyone. The poor thing had to stop every time it changed gears! You can see video of one in action below. Fortunately, it never saw actual combat, and the few prototypes were eventually retired.
[Thanks to Gareth E. for suggesting this topic.]