Shaft Deflection Screen

WHAT THIS SCREEN ANSWERS

Deflection can govern a shaft even when nominal stress is modest. It affects bearing alignment, seal wear, gear mesh, belt tracking, coupling life, positioning, vibration, and clearance. This screen gives an early estimate for a simple supported shaft with one centered load, making the stiffness effect of span and diameter visible before the component layout becomes fixed.

Enter center load, effective bearing span, shaft diameter, and elastic modulus. MechPlane derives the second moment of area for a solid circular section and applies the centered-load, simply-supported beam relation. Diameter has a strong fourth-power effect on stiffness, while span has a cubic effect. Those relationships make the page useful for comparing a layout change against a diameter change.

A real shaft rarely matches the ideal boundary condition exactly. Loads may be distributed, overhung, moving, or applied between supports. Bearings have stiffness, housings deflect, shafts are stepped, and mounted parts add mass and bending moments. The result should be treated as an early directional screen, not as an alignment, bearing-life, or gear-mesh approval.

Use the estimate to decide whether shaft stiffness deserves a more detailed model. Confirm actual load locations, support conditions, bearing stiffness, housing compliance, deflection criteria, fits, and dynamic behavior. Continue to bearing and critical-speed review when rotation or precision alignment is part of the application.