MP-23 · SHAFTS AND JOINTS
Shaft Critical Speed Screen
Screen a simple rotor for first critical-speed sensitivity from supported span, central mass, shaft diameter, modulus, and operating rpm.
Preliminary design support. Your inputs and results stay in this browser.
WHAT THIS SCREEN ANSWERS
A rotating shaft can become dynamically sensitive when operating speed approaches a natural bending mode. The first question is not whether a shaft is strong enough in static stress. It is whether its geometry, span, and rotating mass create an obvious speed-separation issue. This screen uses a deliberately simple rotor model to expose that risk early.
Enter a central rotating mass, support span, shaft diameter, elastic modulus, and operating rpm. MechPlane first estimates static center deflection for a simply supported shaft, then uses that deflection in a Rayleigh-style first critical-speed proxy. If operating speed approaches the estimate, the result warns rather than claiming a safe speed.
Actual rotors are more complex. Mass can be distributed or overhung. Bearings and housings have stiffness and damping. Couplings, gears, pulleys, balance quality, shaft steps, preload, and support structure all change the mode shape. A simple model is valuable only because it tells the designer when the simplistic model has reached its boundary.
Use this page to identify a possible rotor-dynamics review. Confirm the actual assembly, support stiffness, balance requirements, acceleration path, operating range, resonance crossings, and manufacturer guidance before establishing any speed limit. Do not treat a separation ratio as approval of high-speed rotating equipment.