Two-Plane Balancing Calculator

Long rotors combine static and couple unbalance. Measure both bearings (A and B), attach a trial weight in plane 1 and then plane 2; the calculator solves the 2×2 influence coefficient system.

Initial run

Bearing A · Amplitude Phase (°)

Bearing B · Amplitude Phase (°)

Trial 1 — weight in plane 1

Trial mass (g) Angle (°)

Bearing A · Amplitude Phase (°)

Bearing B · Amplitude Phase (°)

Trial 2 — weight in plane 2

Trial mass (g) Angle (°)

Bearing A · Amplitude Phase (°)

Bearing B · Amplitude Phase (°)

Plane 1 correction —g at —°

Plane 2 correction —g at —°

Influence coefficients

α A1: —
α B1: —
α A2: —
α B2: —

Each trial weight is assumed to be removed before the next run.

These tools are intended for preliminary assessment and training. Decisions on critical equipment should be based on on-site measurement and expert evaluation.

How to use

Measure 1X amplitude and phase at bearings A and B at operating speed.
Attach a trial weight in plane 1, measure both bearings again, remove the weight.
Attach a trial weight in plane 2, measure both bearings again, remove the weight.
Apply the calculated corrections to both planes and take a verification reading.

Theory & formulas

Influence coefficients: α_A1 = (A₁ − A₀) / W₁, α_B1 = (B₁ − B₀) / W₁, and likewise for plane 2.

The corrections solve the complex linear system [α] · [C₁, C₂]ᵀ = −[A₀, B₀]ᵀ (Cramer’s rule).

A small matrix determinant means the two trials produced similar effects; the solution is then sensitive to measurement error.

Frequently asked questions

When is two-plane balancing needed?

When the rotor is long relative to its diameter, or when the phases at the two bearings differ clearly (couple unbalance). Narrow disc-type rotors usually need only one plane.