This page now separates the documented Quimby twin-screw topology from user-declared operating-point arithmetic. The animation shows counter-rotating screws and inward qualitative flow to a central discharge, while the calculator no longer presents an entered efficiency as measured performance.
Declared Positive-Displacement Operating Point
Enter a declared displacement, speed, volumetric-efficiency factor and pressure rise. The worksheet applies exact unit identities but does not generate a pump curve, leakage law, pressure capability or selection result.
Equation Used
- D is a declared displacement in US gallons per revolution and N is declared revolutions per minute.
- Eta_v is a user-entered dimensionless factor, not predicted from geometry, clearances, pressure, viscosity or speed.
- DeltaP is a declared pressure rise in psi and the factor 1714 converts GPM times psi to hydraulic horsepower.
- The animated screws counter-rotate qualitatively and show inward flow from both ends toward the middle discharge documented by Hiscox.
- Rotor profiles, pitch, chamber volume, timing, clearances and casing dimensions are not reconstructed.
- Pump curve, leakage, compression, torque, shaft power, mechanical efficiency, NPSH, viscosity, cavitation, heating, materials, ratings, selection, operation and safety are excluded.
Retains exact declared flow and hydraulic-power identities, replaces performance prediction language with an explicit ledger, and adds a connected source-grounded twin-screw flow animation.
Two intermeshing screws convey fluid inward to a middle discharge
Hiscox's Quimby plate labels suction at both ends and discharge at the middle of a close-fitted twin-screw casing. US Patent 6,375,443 describes Quimby-type paired screw rotors whose profiles and housing form working chambers.
The animation preserves that topology qualitatively; it does not reconstruct the historical rotor profile or chamber volumes.
Use this as a declared operating-point ledger
The worksheet converts a declared displacement and speed to ideal flow, applies a declared volumetric factor, and converts declared flow and pressure rise to ideal hydraulic power.
It cannot identify a suitable pump, establish pressure capability or predict an operating point.
Declared flow and fluid-power identities
Q_d is declared-adjusted flow, not measured actual flow. P_h excludes mechanical and drive losses.
A transparent declared example
For D=0.50 gal/rev, N=900 rpm, eta_v=90 percent and DeltaP=600 psi, ideal flow is 450.0 GPM, declared-adjusted flow is 405.0 GPM, the declared difference is 45.0 GPM and ideal hydraulic power is 141.8 hp.
A ledger is not a pump curve
Real performance depends on rotor profile, clearances, viscosity, pressure, speed, temperature, gas content and internal leakage. Shaft and motor power additionally require mechanical and drive efficiencies.
The former actual-flow, slip-prediction, pressure-capability, application, maintenance and troubleshooting claims are removed or explicitly bounded.
Quimby ledger questions
Is eta_v predicted?
No; it is declared.
Is DeltaQ calculated leakage?
No.
Is hydraulic power shaft power?
No.
Does the animation reproduce the Quimby rotor profile?
No.
Quimby topology and fluid-power references
- Hiscox, Mechanical Movements: Quimby twin-screw plate with suction at both ends and discharge at the middle.
- US Patent 6,375,443: Quimby-type paired screw rotors, profile family and rotor/housing working chambers.
- US EPA, Vapor Generator Feed Pump report: liquid hydraulic horsepower equals GPM times pressure rise in psi divided by 1714.
Building or designing a mechanism like this?
Explore the precision-engineered motion control hardware used by mechanical engineers, makers, and product designers.
