Does this page select or rate a flexible coupling?

No. It performs transparent arithmetic using user-supplied power, speed, multiplier, inertias, dynamic torsional stiffness and excitation order. Manufacturer limits and the governing design procedure remain required.

Does the frequency ratio prove that torsional resonance is avoided?

No. It compares one ideal undamped two-inertia mode with one entered synchronous order. Real systems can be multi-mass, nonlinear, damped and excited at many orders and transient events.

Sourced parameters required — ideal two-inertia model

Two-Inertia Coupling Torsional Arithmetic

Calculate power-speed torque and one ideal undamped torsional mode from documented dynamic stiffness,inertias and excitation order.

No coupling selectionNo generic stiffnessNo resonance verdict

Arithmetic results

Nominal transmitted torque,P/ω

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K-scaled torque arithmetic

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Reduced inertia,J₁J₂/(J₁+J₂)

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Ideal undamped torsional frequency

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Entered synchronous-order frequency

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Frequency ratio,fₙ/f_exc

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Signed frequency difference,fₙ−f_exc

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Absolute separation relative to f_exc

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Exact power-speed torque

ω=2πn/60
T=P/ω=(30000/π)·P_kW/n_varvtal
T_K=K·T

The former rounded constant9549 is replaced by the direct SI relation. T_K is only multiplication by a user-supplied K;it is not labelled a DIN-required torque or coupling rating.

Ideal undamped two-inertia mode

J_red=J₁J₂/(J₁+J₂)
fₙ=(1/2π)√(C_t,dyn/J_red)
f_exc=q·n/60

The displayed ratio and separation compare only this one ideal mode with one entered synchronous order. They do not prove resonance avoidance.

DIN740-2 context — no closed load factors implemented

DIN740-2:1986-08 is listed by DIN Media as current and is titled “Power transmission engineering;flexible shaft couplings;parameters and design principles”. Public scope information states that its calculation methods contain empirical load factors and apply only to a linear two-mass system under specific operating conditions;more elaborate methods are required when a rough calculation is not permissible. This page does not reproduce or claim any closed factor,table or clause.

Not modelled: multiple inertias,shaft/distributed stiffness,gear-ratio reflection errors,damping,nonlinear elastomer stiffness,backlash,transient start/stop,fault torque,electrical or reciprocating excitation spectra,harmonics other than entered q,temperature/load dependence,misalignment,maximum speed,bore/key/hub stresses,fatigue,guarding or manufacturer limits.