How It Works

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Hydraulic Motor Speed Fundamentals

Motor speed is determined by the volume of fluid flowing through the motor divided by the displacement per revolution. Volumetric efficiency accounts for internal leakage.

Speed Formulas

Metric (SI Units):

N = (Q x 1000) / D

Where: N = Speed (RPM), Q = Flow Rate (L/min), D = Displacement (cc/rev)

Imperial Units:

N = (Q x 231) / D

Where: N = Speed (RPM), Q = Flow Rate (GPM), D = Displacement (in3/rev)

Note: 231 in3 = 1 US gallon

Theoretical vs Actual Speed

Theoretical Speed: Calculated assuming 100% volumetric efficiency
Actual Speed: N_actual = N_theoretical x eta_v (volumetric efficiency)
Volumetric Efficiency: Typically 90-98% for quality motors

Speed Limits by Motor Type

Gerotor/Orbit Motors: Max 50-800 RPM (typically limited by orbital motion)
Vane Motors: Max 200-2500 RPM (limited by vane wear)
Axial Piston Motors: Max 500-6000 RPM (highest speed capability)
Radial Piston Motors: Max 1-300 RPM (designed for low speed, high torque)

Effects of Over-Speed

Increased wear and reduced service life
Cavitation damage (if inlet flow restricted)
Excessive heat generation
Seal damage and external leakage

Motor Speed Calculator

Calculate theoretical and actual motor speed from flow rate, displacement, and volumetric efficiency. Includes speed limit warnings for different motor types.

Quick Select Presets

Unit System

Flow Rate (L/min)

Motor Displacement (cc/rev)

Volumetric Efficiency (%) Typical: 90-98% for quality motors

Motor Type (for speed limit check)

✔

Calculating...

Speed within limits

Speed vs Limit

0 RPM

-- RPM

Safe Zone Max Limit

Results

Theoretical Speed --

Actual Speed --

Speed per L/min (or GPM) --

Slip Speed (Leakage) --

Motor Type Max Speed --

Speed Margin --

Reference Formulas

Metric Speed:

N (RPM) = Q (L/min) x 1000 / D (cc/rev)

Imperial Speed:

N (RPM) = Q (GPM) x 231 / D (in3/rev)

Actual Speed:

N_actual = N_theoretical x eta_v

Motor Speed Limits

Motor Type	Min Speed	Max Speed	Notes
Gerotor/Orbit	10 RPM	800 RPM	Low speed, high torque
Vane	50 RPM	2500 RPM	Smooth, medium speed
Axial Piston	100 RPM	6000 RPM	High speed, high efficiency
Radial Piston	1 RPM	300 RPM	Very low speed, max torque

Flow Requirements by Displacement

Displacement	100 RPM	500 RPM	1000 RPM
50 cc/rev	5 L/min	25 L/min	50 L/min
100 cc/rev	10 L/min	50 L/min	100 L/min
200 cc/rev	20 L/min	100 L/min	200 L/min
500 cc/rev	50 L/min	250 L/min	500 L/min