Glossary of Terms


Axial Piston - Type of design for hydraulic motors and pumps in which the pistons are arranged parallel with the spindle (input or output shaft).

Accelerator - An electric sensor that replaces the trunnion arm and mechanical linkage function that is found in a traditional hydrostatic drive system.

Axle - A shaft or spindle on which a wheel or pair of wheels revolves.


Bypass Valve - A valve whose primary function is to open a path for the fluid to bypass the motor or pump. Also referred to occasionally as the freewheel valve or dump valve.


CAN (Control Area Network) - A communication protocol for active components in a system.

Case Drain Line (Return Line) - A line returning fluid from the component housing to the reservoir.

Cavitation - A concentrated gaseous condition within the fluid causing the rapid implosion of a gaseous bubble.

Center Section - A device which acts as the valve body and manifold of the transmission.

Charge - To replenish a hydraulic system faster than what normal atmospheric pressure can accomplish.

Charge Pump - A device which supplies replenishing fluid to the fluid power system (closed loop).

Charge Pressure - The pressure at which replenishing fluid is forced into a fluid power system.

Charge Relief Valve - A pressure control valve whose primary function is to limit pressure in the charge circuit.

Check Valve - A valve whose primary function is to restrict flow in one direction.

Closed Loop - A sealed and uninterrupted circulating path for fluid flow from the pump to the motor and back.

Continuity - An uninterrupted path from point A to point B.

Contactor - An electromagnetic switch device (a relay) used for switching an electrical circuit.


Decay Rate - The ratio of pressure decay over time.

Deck Controller - The computer controller for the deck motors, reports to the Traction Controller.

Deck Motor - The electric motor that powers the cutting blades.

Digital Display - LCD dash display that communicates system status from the traction controller to the operator.

Displacement - The quantity of fluid that can pass through a pump or motor in a single revolution.

DMM (Digital Multi-meter) - combination ohm, voltage, and current meter.

Drive Motor - The electric motor that powers the gear case.


Electric Current - Is the rate of charge flow past a given point in an electric circuit measured in Amps.

Electric Short - A low resistance connection between two points in an electrical circuit. The current flows through the area of low resistance, bypassing the intended current flow in the circuit.

End Cap - See "Center Section."

Entrained Air - A mechanically generated mixture of air bubbles having a tendency to separate from the liquid phase.


Flow - To move or proceed steadily (fluid); pump creates flow (expressed in gallons per minute - GPM).


Gerotor - A formed rotor set operating about an eccentric that provides a fixed displacement for pumps or motors.


Hydraulic Motor - A device which converts hydraulic fluid power into mechanical force and mo­tion by transfer of flow under pressure.

Hydraulic Pump - A device which converts mechanical force and motion into hydraulic fluid power by producing flow.

Hydraulics - Engineering science pertaining to liquid pressure and flow.

Hydrostatic Pump - See "Hydraulic Pump."

Hydrostatic Transaxle - A multi-component assembly including a gear case and a hydrostati­c transmission.

Hydrostatic Transmission - The combination of a hydraulic pump and motor in one housing to form a device for the control and transfer of power.

Hydrostatics - Engineering science pertaining to the energy of confined fluids.


Inlet Line - A supply line to the pump.

Integrated Electric Transaxle - The electric motor and gear case assembly that transmits power to the wheels.

Integrated Zero-Turn Transaxle - The combination of a hydrostatic transmission and gear case in one housing to form a complete transaxle.


Manifold - A conductor which provides multiple connection ports.


NC - Normally closed switch.

Neutral - Typically described as a condition in which fluid flow and system pressure is below that which is required to turn the output shaft of the motor.

NO - Normally open switch.


Ohm Meter - A meter that only measures resistance, measured in ohms.


Pressure - Application of steady force by one body in contact with another; caused by resistance to flow; normally expressed in pounds per square inch (PSI).

Pressure Decay - A falling pressure.

Priming - The filling of the charge circuit and closed loop of the fluid power system during start up, frequently achieved by pressurizing the fluid in the inlet line.

Purging - The act of replacing air with fluid in a fluid power system by forcing fluid into all of the components and allowing the air a path of escape.


Rated Flow - The maximum flow that the power supply system is capable of maintaining at a specific operating pressure.

Relief Valve - A pressure operated valve which bypasses pump delivery (flow), limiting system pressure to a predetermined maximum value.

Resistance - The level of opposition to current flow in an electrical system, measured in Ohms.


Smartec ZT 45 Traction Controller - The computer controller for the drive and deck system.

Swash Plate - A mechanical device used to control the displacement of the pump pistons in a fluid power system.

System Charge Check Valve - A valve controlling the replenishing flow of fluid from a charge circuit to the closed loop in a fluid power system.

System Pressure - The pressure which overcomes the total resistance in a system, including all efficiency losses.


Valve - A device which controls fluid flow direction, pressure, or flow rate.

Variable Displacement Pump - A pump in which the displacement per revolution can be varied.

Voltage - A measurement of the electrical energy in a circuit at a given point; measured in volts.

Voltage Inverter - An electrical device that converts the system DC voltage to AC voltage.

Volumetric Displacement - The volume for one revolution.

Wiring Harness - Grouping of conductors (wires) that carry information and electricity.

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