Tractors are equipped with high-torque engines which they need to pull enormous loads (whether riddles, ploughs, slurry tanks, tree stumps -you name it).
This situation can often cause them to execute a low-altitude ‘wheelie’.
In order to avoid staring at the sky, a farmer may attach a collection of big metal weights to the front bumper. This can’t be good for fuel consumption and humping all that metal about is heavy work for even the horniest handed son of toil.
Today’s invention is to mount the fuel tank on a pair of rails running fore and aft on top of the engine (as in the old Ferguson design). When the tractor was pulling hard, the tank would automatically shift forward to act as a counterbalance and keep the front wheels on the ground. The lower the fuel level on board, the farther forward would the tank move.