ABSTRACT
This chapter examines many of the compromises and trade-offs necessary to specify, rather than design, the correct bearing/shaft system, for the machine designer with limited experience of such systems. It shows a simple comparison chart of the most likely bearing systems to be considered for a rotary scanner based on rotational accuracy, maximum speed capability, relative price, and lifetime. The chapter examines in some detail the two main types of gas bearings; namely self acting, aerodynamic and pressure-fed aerostatic designs. There are certain fundamental characteristics of gases that explain why gas bearings are particularly suitable for high-speed rotary scanner designs. There are two main surface forms used in aerodynamic scanner bearings; spiral grooves and lobing. Whichever gas bearing system is selected, certain bearing and shaft dynamics have to be considered to allow high-speed operation, and specifically the synchronous whirls, the half-speed whirl, and the shaft natural frequency.
