This revision keeps the hydraulic motor, shaft, crank and compressor piston connected while limiting the calculation to a transparent declared power ledger. It makes no air-output or receiver-sizing prediction.
Hydraulic Drive Power and Torque Ledger
Enter pressure differential across the hydraulic motor, motor flow, shaft speed and a declared total motor efficiency. The outputs reconcile fluid input, declared shaft output, average shaft torque and the remaining declared conversion loss.
Equation Used
- Pressure is the declared differential across the hydraulic motor, not a system or relief setting.
- Flow is the declared flow through the motor under the same steady comparison condition.
- Total motor efficiency is a user-entered aggregate conversion assumption.
- Torque is the average value corresponding to declared shaft power and speed.
- The animation preserves crank radius and connecting-rod length; its air-valve markers are qualitative.
- Starting torque, ripple, leakage, pressure loss, air thermodynamics, CFM, receiver sizing, controls, heat rejection, ratings and safety validation are excluded.
Relabels pressure as motor differential, limits efficiency loss to a declared ledger, removes unsupported compressor performance and safety claims, and connects an exact slider-crank animation.
Hydraulic power crosses a motor and mechanical shaft
Parker defines hydraulic motor input from pressure differential and flow, then relates mechanical output to shaft torque and speed. The animation follows that topology from hydraulic ports through a rotating motor, shaft, crank and connecting rod to the compressor piston.
The slider-crank drawing preserves fixed crank radius and connecting-rod length. Intake and discharge markers identify only the qualitative half-cycles; they do not simulate valve dynamics or gas compression.
A concept ledger, not a compressor sizing result
The worksheet can reconcile a declared hydraulic operating point with a declared motor efficiency, shaft power and average shaft torque. It cannot select a motor, pump, compressor, receiver, valve, hose, cooler or drive.
Reconcile fluid power, shaft power and average torque
Parker and Danfoss publish these US customary power relationships. DeltaP is the pressure differential across the motor, Q is motor flow, eta_t is the separately declared total motor efficiency, N is shaft speed and T is average shaft torque in lb-in.
The declared conversion loss is the arithmetic remainder HP_fluid minus HP_shaft. Calling all of that remainder heat would require a thermal system boundary that this worksheet does not define.
A transparent declared operating point
At 2000 psi differential and 30 GPM, fluid input is 35.01 hp. With 85% declared total motor efficiency, shaft output is 29.75 hp. At 1000 RPM, the corresponding average shaft torque is 1875 lb-in and the declared conversion loss is 5.25 hp.
Shaft power does not determine air delivery by itself
Air output additionally depends on compressor displacement, speed, volumetric efficiency, pressure ratio, inlet state, leakage, valve behavior and thermodynamics. Those inputs are absent, so prior CFM, pressure-rise, temperature, receiver-fill, duty, tolerance, service-life and field-case claims are removed.
Compressed-air receivers require applicable safeguards. OSHA 1910.169, for example, addresses pressure gauges, safety valves and drains for covered air receivers. This page is not an operating or pressure-adjustment procedure.
Hydraulic-drive ledger questions
Is pressure the pump or relief setting?
No. It is the declared differential across the hydraulic motor.
Is the loss output a heat-load result?
No. It is only the power remainder implied by the entered efficiency.
Does shaft power determine compressor CFM?
No.
Are the animated air valves calculated?
No. They only mark qualitative intake and discharge half-cycles.
Hydraulic-drive and receiver references
- Parker Pump & Motor Division, Engineering Data: hydraulic horsepower from pressure differential and flow, and mechanical horsepower from torque and speed.
- Danfoss, Series L Component Selection: fluid and mechanical horsepower conversions used in hydraulic drive selection.
- Danfoss, General Orbital Motors Technical Information: motor relationships and total efficiency context.
- OSHA 1910.169, Air receivers: safeguards for covered compressed-air receivers.
Building or designing a mechanism like this?
Explore the precision-engineered motion control hardware used by mechanical engineers, makers, and product designers.
