How It Works
Hydraulic Motor Torque Fundamentals
Hydraulic motors convert fluid power (pressure and flow) into mechanical rotational power (torque and speed). The torque output depends on displacement, operating pressure, and mechanical efficiency.
Torque Formulas
Metric (SI Units):
T = (D x P) / (20 x pi)
Where: T = Torque (N-m), D = Displacement (cc/rev), P = Pressure (bar)
Imperial Units:
T = (D x P) / (2 x pi)
Where: T = Torque (lb-in), D = Displacement (in3/rev), P = Pressure (psi)
Convert to lb-ft by dividing by 12.
Theoretical vs Actual Torque
- Theoretical Torque: Calculated assuming 100% mechanical efficiency
- Actual Torque: T_actual = T_theoretical x eta_m (mechanical efficiency)
- Mechanical Efficiency: Typically 85-95% for quality motors
Motor Types and Characteristics
- Gerotor/Orbit Motors: Low speed (50-800 RPM), high torque, compact design
- Vane Motors: Medium speed (200-2500 RPM), smooth operation
- Axial Piston Motors: High speed (500-6000 RPM), high efficiency
- Radial Piston Motors: Very low speed (1-300 RPM), highest torque
Motor Torque Calculator
Calculate theoretical and actual torque output from hydraulic motor displacement, system pressure, and mechanical efficiency.
Typical: 85-95% for quality motors
Calculating...
Motor classification: --
Results
Theoretical Torque
--
Actual Torque
--
Torque per bar/psi
--
Torque Constant
--
Motor Category
--
Typical Speed Range
--
Reference Formulas
Metric Torque:
T (N-m) = D (cc/rev) x P (bar) / (20 x pi)
Imperial Torque:
T (lb-in) = D (in3/rev) x P (psi) / (2 x pi)
Actual Torque:
T_actual = T_theoretical x eta_m
Motor Type Comparison
| Motor Type | Displacement | Max Pressure | Efficiency |
|---|---|---|---|
| Gerotor/Orbit | 50-800 cc | 140-210 bar | 80-90% |
| Vane | 25-250 cc | 140-175 bar | 80-92% |
| Axial Piston | 20-500 cc | 280-450 bar | 90-97% |
| Radial Piston | 100-5000 cc | 350-450 bar | 92-98% |
Application Guidelines
| Application | Typical Torque | Recommended Motor |
|---|---|---|
| Conveyors | 100-500 N-m | Orbit/Gerotor |
| Winches | 500-5000 N-m | Radial Piston |
| Wheel Drives | 200-2000 N-m | Orbit or Axial Piston |
| Mixers/Agitators | 50-300 N-m | Vane or Orbit |
| High-Speed Spindles | 10-100 N-m | Axial Piston |