Investigation of the Step-Thrust Gas Bearing Without Feed Grooves for Two Directions of Shaft Rotation

The step-thrust self-acting gas bearing was investigated for an application where equal load support was required for both directions of rotation. A method of computer analysis by James and Potter [1] shows characteristics of the support for geometric, gas and speed parameters. Support of this step bearing is shown to be about one fifth of a good spiral-groove thrust bearing (spiral-groove bearings are limited to one direction of rotation). For comparison, a good thrust plate of unidirectional design would have the following parameters: groove width ratio ∼0.5, groove depth ratio ∼3, spiral angle ∼70 deg, and a radius ratio (R₁/R₀) ∼0.62. Two test models were built and evaluated to confirm the computer analysis. Dynamic responses to vibration loads were also tested.