Linear undamped model — one degree of freedom
Equivalent-Stiffness SDOF Natural Frequency Check
Calculate one undamped translational natural frequency from a documented equivalent stiffness and participating mass. This is not a complete machine-foundation dynamic analysis.
Undamped SDOF result
Implemented model
ωn=√(K/m)
fn=ωn/(2π)
Tn=1/fn
K is the equivalent translational stiffness in N/m for the stated mode,m is its participating mass in kg,ωn is in rad/s,fn is in Hz and Tn is in seconds. Dimensional check:√[(N/m)/kg]=√(s⁻²)=s⁻¹.
Two input bases
Direct K uses a documented modal/equivalent stiffness. Area-normalized uses K=kAA only when the cited source explicitly defines kA in MN/m³ and that linear area model for the same direction,geometry and conditions. The calculator does not treat kA as an intrinsic soil property.
Traceability and soil-model warning
MIT OpenCourseWare,Dynamics and Control I,Lecture20 gives mẍ+cẋ+Kx=0 and ωn²=K/m for an SDOF system. FHWA NHI-05-037 §5.4.6 states that the modulus of subgrade reaction is not a true soil property because it also depends on footing/slab size and stiffness. It further distinguishes dynamic and traditional static k-values.
No automatic resonance criterion
This result alone cannot label an operating speed safe or unsafe. Compare all excitation orders with all relevant coupled modes using documented damping,forcing and project-specific acceptance criteria. No universal30% separation rule,soil range or machine preset is applied.
Nikolai Shelkovenko
Nikolai Shelkovenko is a vibration analysis engineer and the founder and CEO of Vibromera. For more than 15 years he has balanced rotating equipment in the field rather than on a test bench: mulchers, industrial fans, crushers, centrifuges, shafts and spindles. That work is what the Balanset instruments grew out of — they were designed as a tool a specialist can carry to the machine and use alone, on site, not as laboratory equipment. Vibromera was founded in 2017 and has been based in Porto, Portugal, since 2023. Development, assembly and support of the Balanset line all happen here. The flagship instrument is the Balanset-1A, a portable analyser for single- and two-plane balancing and for vibration diagnostics. Nikolai is personally involved in customer support, in working through difficult balancing cases and in the development of the software. He works with customers worldwide, in any language.
