Hamrock-Dowson Film Thickness

Minimum EHL film thickness in elliptical point contact (rolling-element bearings): h_min / R = 3.63 · U^0.68 · G^0.49 · W^(-0.073) · (1 − e^(-0.68k)).

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Formula, assumptions, and limits

\frac{h_\text{min}}{R} = 3.63 U^{0.68} G^{0.49} W^{-0.073} (1 - e^{-0.68k})

Symbol	Meaning	Unit
$U$	Speed parameter
$G$	Material parameter
$W$	Load parameter
$k$	Contact ellipticity

Source: Hamrock & Dowson (1977)

In short

Minimum EHL film thickness in elliptical point contact (rolling-element bearings): h_min / R = 3.

Learn the theory Cylinder Lubrication Systems: Two-Stroke Engines