Home > SAI BD Series variable displacement hydraulic motors from Custom Fluidpower

SAI BD Series variable displacement hydraulic motors from Custom Fluidpower

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Custom Fluidpower  offers the SAI BD Series variable displacement hydraulic motors featuring an innovative bearing arrangement. 

The B series five cylinder crankshaft design radial piston hydraulic motors utilise many of the proven components from the GM series motors, well known for their high performance and reliability.

The innovatively designed sliding central bearing arrangement made possible by the latest materials and manufacturing techniques increases the range of possible options in SAI hydraulic motors.

These options include the possibility to change displacement, fit taper roller bearings for axial load capability, have a hollow through shaft option, and fit a counterbalance weight to smooth out high speed vibration. It’s also possible to accept higher radial loading of the motor shaft due to a larger cross section giving extra strength.

Change of motor displacement

Change of motor displacement in the BD series hydraulic motors is achieved by changing the stroke of the crankshaft in a 20-30 bar range, with changes from high to low displacement and vice versa taking place dynamically as well as statically.


The BD series hydraulic motors can be freewheeled in full cavitation.

Design and operation

The sliding bearing has an extremely low coefficient of friction, delivering very high starting torque efficiency, and continuing to achieve higher than average mechanical efficiencies both in high and low displacement modes.

Starting and low speed torque

The hydraulic motors are capable of working at low speeds with a high degree of speed stability and the minimum stable speed depending on the displacement of the motor. Output torque remains constant and does not fall away at very low speeds or under stall or start conditions.

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