Hydraulic Motor Torque and Speed
The torque, speed, and horsepower a hydraulic motor puts out.
Example
You enter
- Pressure differential (psi) 2000
- Motor displacement (in³/rev) 2
- Supply flow (gpm) 10
- Mechanical efficiency (0-1) 0.9
- Volumetric efficiency (0-1) 0.95
You get
- Output torque 573 in-lb
- Output speed 1,097 rpm
- Output power 9.98 HP
Checked against published worked examples from: Hydraulics & Pneumatics (Power & Motion).
Details, formula, and sources
ScopeTorque = psi x disp / (2 pi) x mech eff, speed = 231 x gpm / disp x vol eff, HP = T x rpm / 63025. 2000 psi, 2.0 in^3/rev, 10 GPM -> 573 in-lb, 1097 rpm, 9.98 HP; doubling displacement halves speed and doubles torque (same power). A sizing aid; the motor data govern.
Formula or tabletorque = psi x disp / (2 pi) x mech_eff; rpm = 231 x gpm / disp x vol_eff; hp = torque x rpm / 63025.
Source and editionThe fluid-power motor torque/speed relations (torque = psi x disp / 2 pi, speed = 231 gpm / disp), by name.
Free accessThe displacement-based torque and speed relations and the 231 in^3/gal and 63025 constants are standard published fluid-power results.
What governsEstimate. AHJ and licensed professional govern.
API field namespsi, disp_in3, gpm, mech_eff, vol_eff, torque_inlb, rpm, output_hp
- Torque psi x disp / (2 pi) x mechanical efficiency (in-lb)fluid-power engineering
- Speed 231 x gpm / disp x volumetric efficiency (rpm)fluid-power engineering
- Power output HP = torque x rpm / 63025fluid-power engineering