Modular pump design

A modular pump, comprising:

• a reciprocating pump, comprising:
• a universal gearbox comprising
• a universal adapter hub having a first opening on a left side of the universal gearbox and a second opening on a right side of the universal gearbox, both openings sized to receive a crank unit attachment, wherein the first and second openings extend through opposite ends of the universal gearbox and are aligned with each other along a rotational axis of the universal adapter hub;
• and
• at least one gear that is mechanically coupled to the universal adapter hub at a location along the universal adapter hub outside of the first opening and the second opening to impart rotation to the universal adapter hub;
• and
• at least one crank unit attachment removably coupled to the universal gearbox on the right side, the left side, or both, wherein the at least one crank unit attachment comprises:
• a splined hub unit extending through the first opening on the left side of the universal gearbox or the second opening on the right side of the universal gearbox;
• and
• at least two crank throws for connection to a rod and piston arrangement of the reciprocating pump;
• wherein the at least one crank unit attachment is removable and interchangeable with at least one structurally different crank unit attachment having a different number of crank throws.