How It Works
Motor Selection Process
Selecting the right hydraulic motor involves matching the required torque and speed to available motor types, considering system pressure, and calculating the necessary displacement and flow rate.
Step 1: Calculate Required Displacement
From Torque Requirement (Metric):
D = (T x 20 x pi) / (P x eta_m)
Where: D = Displacement (cc/rev), T = Torque (N-m), P = Pressure (bar), eta_m = mechanical efficiency
From Torque Requirement (Imperial):
D = (T x 2 x pi x 12) / (P x eta_m)
Where: D = Displacement (in3/rev), T = Torque (lb-ft), P = Pressure (psi)
Step 2: Calculate Required Flow
Metric:
Q = (N x D) / (1000 x eta_v)
Where: Q = Flow (L/min), N = Speed (RPM), D = Displacement (cc/rev), eta_v = volumetric efficiency
Imperial:
Q = (N x D) / (231 x eta_v)
Where: Q = Flow (GPM), N = Speed (RPM), D = Displacement (in3/rev)
Step 3: Calculate Power Consumption
Hydraulic Power:
P_hyd = Q x P / 600 (kW, with Q in L/min and P in bar)
P_hyd = Q x P / 1714 (HP, with Q in GPM and P in psi)
Motor Type Selection Guide
- Gerotor/Orbit: Best for 50-800 RPM, compact, economical, moderate efficiency
- Vane: Best for 200-2500 RPM, smooth operation, good for fans and conveyors
- Axial Piston: Best for 500-6000 RPM, highest efficiency, premium cost
- Radial Piston: Best for 1-300 RPM, maximum torque, ideal for winches and wheel drives
Efficiency Considerations
- Overall Efficiency: eta_overall = eta_m x eta_v (mechanical x volumetric)
- Typical Overall: 75-90% depending on motor type and condition
- At Low Speed: Efficiency drops significantly - add safety margin
Motor Sizing Calculator
Enter your required torque, speed, and available system pressure to calculate the necessary motor displacement, flow requirements, and get motor type recommendations.
Application Requirements
Efficiency Estimates
Calculated Requirements
Motor Type Suitability
Key Formulas
Displacement from Torque (Metric):
D (cc) = T (N-m) x 20 x pi / (P (bar) x eta_m)
Flow from Speed (Metric):
Q (L/min) = N (RPM) x D (cc) / (1000 x eta_v)
Hydraulic Power (Metric):
P (kW) = Q (L/min) x P (bar) / 600
Standard Motor Displacements
| Motor Type | Common Sizes (cc/rev) | Typical Applications |
|---|---|---|
| Gerotor/Orbit | 50, 80, 100, 160, 250, 400, 630 | Conveyors, feeders |
| Vane | 25, 45, 70, 100, 160, 250 | Fans, light drives |
| Axial Piston | 28, 45, 63, 80, 100, 125, 180, 250 | High speed, mobile |
| Radial Piston | 200, 400, 600, 1000, 2000, 4000 | Winches, wheel drives |