Viscous couplings use two interleaved plate sets connected to relatively rotating members inside a sealed viscous-fluid chamber. This calculator does not solve that shear flow; it reports normalized input comparisons only.
Viscous Coupling Interactive Calculator
Enter two normalized speed references, a gap reference and kinematic viscosity. Outputs are arithmetic indices—not actual rpm, shear rate, transmitted torque, temperature response or coupling capacity.
Equation Used
- Input and output values are entered normalized speed indices rather than dimensional angular speeds.
- The difference is absolute, so direction and overrun sign are discarded.
- Gap is an entered reference used only in two quotients.
- Kinematic viscosity in cSt is normalized by 100,000 cSt; dynamic viscosity, density and temperature are absent.
- Plate count, radii, wetted area, slot geometry, fill fraction, pressure, fluid rheology, heating, torque, bearings, seals, strength, losses and durability are omitted.
Interleaved-Plate Viscous-Coupling Topology
U.S. Patent 4,889,206 describes a sealed housing and hub carrying interleaved plate sets in viscous fluid. NIST rheology nomenclature defines kinematic viscosity as viscosity divided by density. These sources support topology and units, not this page's proxy.
What This Calculator Represents
The tool compares two normalized speed indices, divides their absolute difference by the input index and gap, and evaluates one fully disclosed dimensionless proxy.
Normalized Speed and Viscosity Comparison
relative difference=100Delta/Nin
index gradient=Delta/g
proxy=(nu/100000)(Delta/30)(0.3/g)
The proxy is not torque and the index gradient is not a physical shear rate.
Worked Index Example
For indices 100% and 70%, gap 0.30 mm and nu=100,000 cSt, difference is 30 percentage points, relative difference is 30%, index gradient is 100 %/mm and the disclosed dimensionless proxy is 1.00.
Model Boundary
- Calculated: normalized differences and a transparent dimensionless comparison proxy.
- Illustrated: interleaved input/output annular plates in a fluid-filled chamber.
- Not calculated: actual rpm, tangential speed, shear rate, stress, torque, temperature, fill, pressure, plate geometry, losses, strength or durability.
Frequently Asked Questions
Is the proxy transmitted torque?
No.
Is percent per millimetre a physical shear rate?
No.
Why is difference absolute?
The absolute difference reports magnitude without indicating which shaft is faster.
Does cSt equal dynamic viscosity?
No; kinematic viscosity is dynamic viscosity divided by density.
Are temperature and shear-thickening included?
No.
Can this size or rate a coupling?
No.
References & Further Reading
- Wikipedia contributors. Viscous coupling unit. Wikipedia
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