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Learn why SAI Hydraulic Motors has been the icon of "power through efficiency" for the past 50 years. Although this story began over 50 years ago, the reason SAI has remained one of the leading companies in the design and production-technology of crankshaft radial piston hydraulic motors has been their advancements in technology year after year. They have specialized in the ability to transform hydraulic power into mechanical power and help designers match overall efficiencies to the application requirements they are seeking. Let's break it down

Hydraulic System Efficiency
This requires hydraulic system designer to first match the motor, then the pump to a specific system performance expectation. Whether the requirement is to do something within a specific time frame, or in handling a given amount of load, the design of the entire system will change depending on the motor selected.
That  is why the motor selection comes first in the process; you start with the load requirement, then work back to the prime mover—the pump that will put the fluid power into the motor selected to deliver the performance goal.

Motor Type
Each motor type— gear, vane, in-line piston, bent-axis piston and radial piston—has a specific performance profile. So, knowing the application performance requirement and which motor type best meets the objective is the first step. Then it’s necessary to evaluate the design advantages of your motor options along with the degree of complexity you want for the overall system. In the end, it all goes back to the application’s performance expectations.

Motor Function
A hydraulic motor is a hydraulic actuator that, when properly connected into a hydraulic system, will produce a rotary actuation. This can be unidirectional or bidirectional depending on the system design. Motors are similar in design to pumps only where a pump takes a rotary actuation to move hydraulic fluid out of the unit, whereas a motor will take flow into itself and put out a rotary actuation.

Motor Selection Criteria

  1. The application of the hydraulic motor generally dictates the required horsepower and motor speed range, although the actual speed and torque required may sometimes be varied while maintaining the required horsepower.

  2. The type of motor selected depends on the required reliability, life, and performance. But where output speed must be reduced, the overall cost of the motor with speed reduction must be considered to optimize the overall drive installation costs.

  3. Once the type of the fluid is determined, the selection of actual size is based on the expected life and the economics of the overall installation of the machine.
    Caution: A fluid motor operating at less than rated capacity will provide a service life extension more than proportional to the reduction in operation below the rated capacity.

  4. Once the type of fluid is determined, the selection of actual size is based on the expected life and economics of the overall installation on the machine.
    Caution: A fluid motor operating at less than rated capacity will provide a service life extension more than proportional to the reduction in operation below rated capacity.

 SAI Hydraulic Motor Product Features

FEATURE: High Starting Torque
BENEFIT: The SAI motor has virtually the same starting torque and dynamic torque. This is due to the presence of the crankshaft roller bearing. With this, startup friction is greatly reduced.

FEATURE: High Volumetric Efficiency
BENEFIT: In all SAI motor parts under pressure, the sealing is provided by Teflon/elastomer seals. The seal can compensate for the normal wearing of parts, as well as the natural expansion of the parts under stress. This enables SAI motors to maintain excellent volumetric efficiency, even after several thousand working hours. This is especially useful in applications requiring precise speed control at very low speeds or good braking capability.

FEATURE: Contamination Resistance
BENEFIT: The SAI design can withstand very large contamination particles in the system, up to 40 µm. All dynamic parts, such as cylinders, pistons, distributors, and valves, are hardened to further enhance their performance and contamination resistance. Large clearances and seals between dynamic parts also adds to the contamination resistance.

FEATURE: Thermal Shock Resistance
BENEFIT: The large clearances also allow SAI motors to have excellent thermal shock resistance. The large clearances will accept thermal expansion, and will not cause the dynamic parts to come in contact with each other and prolong the life of the motor.

FEATURE: Cavitation Resistance
BENEFIT: The innovative SAI design allows the motor to run in partial or full cavitation. The roller bearing under the piston does not require lubrication, and the piston retaining rings ensure that the pistons remain in firm contact with the central roller bearing. These innovative features allow the SAI motor to operate in full cavitation. The traditional hydraulic motor design with hydrostatic balancing under the pistons require lubrication at all times. If there is no lubrication present, it will experience significant frictional damage.


sai Hydraulic Motors

The wide range range of SAI hydraulic motors including: Variable Displacement, Double Displacement and Fixed Displacement motors, characterized by radial pistons and crankshaft design.
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Shaft End Drive Units

Sai Shaft end drive units

SAI offers radial piston motors coupled to single or double stage planetary gearboxes with shaft ends.
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Complete Wheel Drives

sai complete wheel drive units

SAI offers complete wheel motors to be coupled with single or double stage planetary gearboxes and/or drum brakes; compact wheel drive units including planetary gearbox and/or integrated negative disc brakes.
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sai hydraulic brakes

SAI offers shaft end brakes with negative disc.
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