Dual motor hydrostatic drive system

A dual motor hydrostatic drive system, for transmitting power from a pair of prime movers to a common rotatable member, comprising;

• a pair of hydraulic motors operatively drivingly connected to such rotatable member;
• a first hydraulic circuit in communication with one of the hydraulic motors including a pair of fixed displacement pumps driven by one of the prime movers, and valve means selectively actuatable for simultaneously directing the output of both pumps to said one hydraulic motor;
• a second hydraulic circuit in communication with the other of said hydraulic motors including a fixed displacement pump and a variable displacement pump both driven by the other prime mover, and valve means selectively actuatable for simultaneously directing the output of both pumps to said other hydraulic motor;
• and
• means responsive to fluid pressures in the first and second hydraulic circuits for automatically varying the output displacement of the variable displacement pump so that a predetermined relationship is maintained between the fluid pressures in the first and second hydraulic circuits.