Driveshaft Critical Speed Calculator

Inputs

Shaft length (L)

Free span between effective supports.

Outer diameter (OD)

Tube outside diameter.

Wall thickness (t)

Tube wall thickness.

Elastic modulus (E)

Young modulus of the shaft material.

GPa

Density (rho)

Material density.

kg/m³

Use-speed factor (f)

Recommended operating speed as a fraction of calculated first critical speed.

Default result

Suggested max speed(n_safe)

6,418rpm

Pass

Using 0.75 x calculated critical speed.

Also computed

First critical speed(n_cr)8,557rpm

Inner diameter70.2mm

Tube area689.9mm²

Second moment of area(I)46.29cm⁴

Mass per length5.416kg/m

Method notes 2 notes

Uses a uniform simply supported tube approximation for first bending critical speed.
Real driveshaft limits also depend on joint angles, weld yokes, balance quality, tube straightness, end constraints, torque, dents and operating vibration.