If you are going to build a “good” weapon you need to make sure that it effectively does what you want it to do; a gun that hits the enemy and a tank that protects your troops (also while hitting the enemy). However it seems through history there have been some pretty ill-conceived weapons. This includes something called the Bob Semple Tank which was built by looking at a picture of a tank.
Besides having the least-threatening name ever bestowed upon a tank, the Bob Semple barely qualified as one. It was little more than a farm tractor -- and due to several design flaws, it was about as useful as one in a war zone. The designers based it on an American tractor tank, but the problem was that they had no blueprints, no building materials outside those found in a farm and no idea what the hell they were doing. They literally designed the Bob Semple by looking at a postcard of the original tank. By that logic, half of us should be able to reconstruct the Eiffel Tower.