How many revolutions will the drive shaft on a three piston vertical positive displacement meter make for each gallon of fuel delivered?

The correct answer is based on the operational mechanics of a three-piston vertical positive displacement meter. In such a meter, fuel is moved through the system by the reciprocating action of the pistons, with each complete stroke of a piston representing a specific volume of fuel displaced.

For a three-piston meter, each of the three pistons completes a full cycle of intake and discharge within one revolution of the drive shaft. This means that each rotation of the drive shaft allows for the displacement of fuel equivalent to the combined volume of the three pistons.

Therefore, to deliver one gallon of fuel, the pistons need to go through their full cycle multiple times. After calculating the necessary strokes required to deliver that volume, it is determined that the drive shaft must complete four full revolutions for each gallon of fuel delivered. This directly correlates with how the pistons and the drive mechanism are designed to work together, establishing the relationship between the drive shaft's revolutions and the volume of fuel dispensed.

This understanding of the pumping mechanics in positive displacement systems is fundamental for accurately determining flow rates and ensuring efficient operation within fuel handling and measurement systems.