How this calculation works
An arithmetic average of bearing loads misses the nonlinear life penalty of heavily loaded revolutions. This calculator evaluates a repeated duty block using each state’s duration, speed and equivalent dynamic load. It reports basic rating life in operating hours.
Block damage = Σ[60nᵢtᵢ / (10⁶(C/Pᵢ)^p)]; repeated operating hours = Σtᵢ / damageA worked example
A 20 kN ball bearing runs two hours at 1000 rpm and 4 kN, then one hour at 2000 rpm and 8 kN. Each state contributes 120000 revolutions. The block fraction is 0.00864, giving 347.222 operating hours of repeated-block basic L10 life.
Good to know
Basic L10 describes a population reliability convention, not a guaranteed replacement interval. Lubrication, contamination, static damage and speed limits are absent. The page does not reproduce modified SKF life or select a bearing automatically.
Reference: JTEKT — basic bearing rating life (opens in a new tab) ↗
What this model answers
An arithmetic average of bearing loads misses the nonlinear life penalty of heavily loaded revolutions.
This calculator evaluates a repeated duty block using each state’s duration, speed and equivalent dynamic load. It reports basic rating life in operating hours.
The Helical gear tangential radial and axial force calculator resolves ideal mesh-force magnitudes. Bearing equivalent dynamic load still needs the bearing maker’s load coefficients and the shaft reactions.
Keep the input conventions consistent
Enter a manufacturer-derived equivalent dynamic load for each state, already accounting for the relevant radial and axial load relationship.
C and P must both use kN. Stopped periods are outside this rotating-life model and should not be entered with zero speed.
Read the result carefully
Revolution weighting differs from time weighting when speed changes.
A short high-speed heavy-load state may contribute much more life consumption than its share of clock time. The table exposes each state’s fraction of basic rating life rather than concealing it in a single average.
Work through the numbers
A 20 kN ball bearing runs two hours at 1000 rpm and 4 kN, then one hour at 2000 rpm and 8 kN.
Each state contributes 120000 revolutions. The block fraction is 0.00864, giving 347.222 operating hours of repeated-block basic L10 life.
Where the calculation stops
Basic L10 describes a population reliability convention, not a guaranteed replacement interval.
Lubrication, contamination, static damage and speed limits are absent. The page does not reproduce modified SKF life or select a bearing automatically.
A few questions, answered
Is equivalent load just the average of the entered kN values?
No. It is weighted by revolutions and raised to the bearing life exponent before being combined.
What should I change in the comparison?
Switch only the life exponent to compare the mathematical ball and roller models.