Hiscox describes the Heppel rotary pump as four jointed wings linked to an eccentric disc inside a cylindrical shell. The calculator below uses general displacement and fluid-power equations; its two-rotor illustration depicts a separate generic concept, not that historical wing mechanism.
Heppel Rotary Pump Interactive Calculator
Compare theoretical displacement flow, a user-entered volumetric-efficiency scenario, arithmetic flow shortfall and hydraulic fluid output power.
Equation Used
- Entered displacement remains constant per revolution.
- Entered volumetric efficiency is applied uniformly and is not derived from pressure, speed, viscosity, temperature or clearance.
- The animation is a generic counter-rotating two-rotor concept; it does not depict the Heppel four-wing arrangement.
- No suction condition, cavitation/NPSH, torque, mechanical efficiency, seal, bearing, material, pressure rating, relief or safe-speed model.
Scenario arithmetic only. Entered displacement and volumetric efficiency are assumptions, not values predicted from an identified Heppel pump. Hydraulic output is ΔpQ, not shaft input or motor size.
Heppel mechanism and the flow calculation
In Hiscox’s entry 538, four wings turn about the cylindrical shell’s center and connect through links to a disc on an offset shaft. The linkage makes the wings move at different angular speeds on opposite sides of the pump.
The numerical model takes displacement per revolution as an input. Multiplying it by shaft speed gives theoretical flow; an entered volumetric efficiency scales that flow. The calculator does not derive displacement from the wing geometry.
The drawing uses two counter-rotating lobed symbols and fixed fluid markers to illustrate a different generic pump concept. It does not show sealed transport pockets, port timing or the Heppel linkage. Playback is slowed for viewing.
Use as a flow scenario only
The equations can compare entered displacement, speed, efficiency and pressure scenarios. They cannot identify a pump, approve a fluid, predict self-priming or suction lift, establish pressure or speed limits, or select a drive.
Displacement-flow and hydraulic-output identities
Theoretical flow is Qt=Vd n. Applying entered volumetric efficiency gives Qs=ηvQt, and the arithmetic difference Qt-Qs is displayed separately. Hydraulic fluid output is Ph=ΔpQs.
Volumetric efficiency must come from suitable test or manufacturer data for the actual pump, fluid, pressure, speed and temperature. It is not calculated here.
Transparent example
At 250 mL/rev and 300 rpm, theoretical flow is 75 L/min. With an entered 92% efficiency, the scenario flow is 69 L/min and the arithmetic shortfall is 6 L/min. At 2 bar, hydraulic output is 69×2/600=0.23 kW.
Required shaft power would be higher and cannot be found without mechanical/overall efficiency and duty data.
Scope and limitations
A pump assessment needs verified displacement, speed and pressure limits, viscosity range, temperature, materials compatibility, clearances, seals, suction conditions/NPSH, gas content, solids, relief protection, mechanical efficiency, torque and duty. None is supplied by this four-input model.
Frequently asked questions
Does the efficiency input predict wear or slip?
No. It is a user-entered multiplier. The displayed shortfall is only theoretical minus scaled flow.
Can hydraulic output size the motor?
No. Drive sizing also needs mechanical efficiency, starting and peak torque, and duty data.
Does the animation show the historical Heppel pump?
No. Hiscox describes four wings linked to an eccentric disc. The two-rotor illustration is a separate generic concept.
Why does pressure not reduce the calculated flow?
Pressure affects hydraulic power here. Volumetric efficiency is entered independently, so any pressure-dependent leakage must already be reflected in that input.
Mechanism reference and calculation basis
Gardner D. Hiscox, Mechanical Movements, Powers, Devices, and Appliances, entry 538, page 146 describes the Heppel wing-and-eccentric-disc arrangement.
The numerical results follow displacement-flow and hydraulic-power identities. Their inputs are hypothetical unless supplied from suitable measurements or manufacturer data; the book entry does not establish pump ratings, permitted fluids or operating limits.
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