CritSpeed

Sun Engineering

In-app purchases

About this app

CritSpeed — Rotor Critical Speed Estimator

CritSpeed estimates the first lateral bending critical speed of a two-bearing squirrel-cage induction motor rotor using measured shaft geometry and classical engineering methods.

Designed for motor repair shops, reliability engineers, field service engineers, application engineers, and technically capable maintenance professionals who need a practical first-pass rotor screening tool.

WHAT CRITSPEED DOES

• Measured shaft sections — Enter the bearing span and define a uniform or stepped shaft using actual section dimensions and material properties.
• Rotor component modeling — Include the rotor core, conducting bars, and end rings with their axial locations and masses.
• Critical speed estimate band — View the Dunkerley lower estimate (ND), Rayleigh upper estimate (NR), and midpoint (NM).
• Running-speed comparison — Compare observed motor running speed with the estimated critical speed and review green, yellow, or red screening guidance.
• Engineering details — Review component masses, geometry summaries, and running-speed margins.
• Metric and US units — Work with SI or imperial measurements.
• Save and export — Store cases locally and export plain-text engineering reports.
• Built-in QC reference cases — Compare calculated outputs against expected reference values.

HOW IT WORKS

1. Enter the bearing span and define measured shaft sections.
2. Add rotor core, conducting-bar, and end-ring geometry.
3. Optionally enter motor nameplate information and observed running speed.
4. Calculate and review the critical-speed estimates, rotor diagram, and speed classification.
5. Save the case or export the results for your records.

ENGINEERING APPROACH

CritSpeed uses Euler-Bernoulli beam theory, numerical static-deflection solving, the Rayleigh energy method, and the Dunkerley method to estimate the first lateral bending critical speed of a two-bearing rotor.

It is a screening estimator, not finite-element analysis (FEM), a full rotordynamics package, or a guarantee of safe operation. For unusual machines, flexible bearing supports, or high-consequence applications, use specialist engineering analysis.

SUBSCRIPTION REQUIRED

CritSpeed is subscription-only, with no free tier or free trial. Monthly and Annual auto-renewing Google Play subscriptions provide the same full app access and differ only in billing period. Prices and currencies are displayed by Google Play. Restore Purchase is available on the subscription screen, and subscribers can manage their subscriptions through Google Play.

OFFLINE AFTER ACTIVATION

Once a subscription is activated, CritSpeed's core calculations, saved cases, and report generation can be used offline. Purchasing, restoring, verifying, or managing a subscription may require an internet connection.

PRIVACY

No account or login is required. No ads, affiliate links, or location tracking. Rotor measurements, calculations, and saved cases remain on your device; they are not sent as part of subscription verification.

CritSpeed provides practical estimates for engineering screening and comparison. It does not replace detailed analysis where machine criticality warrants it.

What’s new

Initial release of CritSpeed!

• Estimate motor rotor critical speed from measured shaft and rotor geometry.
• Rayleigh and Dunkerley critical-speed estimates.
• Running-speed comparisons with color-coded guidance.
• Support for metric and US measurement units.
• Save cases and export engineering reports.
• Built-in QC reference cases.

Designed for motor repair shops, reliability engineers, and field service professionals.