Our 4-ported models can be used as two speed motors when external valving circuitry is added. Choose your package displacements based on maximum torque required. Unload one package and the remaining package provides a lesser torque value, but with higher speed capability. Two equal packages will provide a 2:1 ratio at the shift. Two unequal displacements will provide different shift ratios depending on the package choices. For example; 125 CID + 60 CID = 185 CID in full displacement. Subject to which package is unloaded, a ratio of either 3.08:1 or 1.48:1 is attained. You may have 2 or 3 speeds depending on your drilling needs and your circuitry.
Open and Closed Loop SystemsEither motor can be switched out of the work mode via external valving. Be sure to connect the 2 main motor ports, (A1 & B1, or A2 & B2) through that valving, to the low pressure side to ensure oil circulation through the unloaded package. If both speeds are needed in both directions, the use of shuttle valves will allow the unloaded motor to remain connected to the low pressure side. For open loop circuits, a minimum pressure of 15 psi should be provided at the ports of the unloaded motor. Care should be taken to size valves properly for their respective flow in the high speed mode. Full system pressure is allowed on working motors during 2 speed operation. The use of cross port reliefs is highly recommended, and should be placed close by the motor assembly. This will guard the system against pressure spikes during normal operation as well as while shifting.
Series/ParallelSeries/Parallel circuitry can only be used when both motor packages are the same displacement. This will provide a 2:1 speed ratio.
Two-Speed Information - 4-Port Models
