Shaft + Bearing System Calculator

This calculator composes the shaft statics with ISO 281 bearing selection. Radial reactions at the two bearings are resolved independently in the vertical and horizontal planes and combined; the external axial thrust is either taken entirely by the locating bearing (fixed–floating) or distributed between an opposed angular-contact / tapered-roller pair using the induced-axial method — each bearing generates an internal axial load Ja = 0.5·Fr/Y, and the external thrust Ka is apportioned per the SKF General Catalogue table 11 load cases (back-to-back "O" or face-to-face "X"). Each bearing is then selected from the real SKF catalogue and rated by ISO 281 exactly as in the Bearing Calculator (dynamic equivalent load P = X·Fr + Y·Fa, L10 = (C/P)^p, reliability factor a1). The two lives are combined into a system rating life for bearings in series, L = (L_A^−e + L_B^−e)^(−1/e), with the ISO 281 Weibull slope e = 1.5. The induced-axial factor uses R = 0.5/Y with the bearing-family Y; SKF refines R (≈0.8–1.0) via a Ka/C diagram for its angular-contact ball series. Thermal axial growth across the span is α·L·ΔT. Not modelled: bearing and housing stiffness, mounting fits, preload and its thermal interaction, and moment loads shared by a paired set — confirm the arrangement, fits and clearance/preload against the manufacturer's procedure before production.

Validated: for two 40° angular contact ball bearings back-to-back with FrA = 1 000 N, FrB = 3 000 N and an external thrust Ka = 1 000 N (Y = 0.57, so R = 0.877), this tool returns the SKF table 11 case 1c distribution Fa_A = 1 632 N, Fa_B = 2 632 N; the case 1a distribution (FrA = 3 000, FrB = 1 000) returns Fa_A = 2 632 N, Fa_B = 3 632 N; and two equal-life bearings combine to a system life of 0.63× the individual life, matching L·2^(−1/1.5).