NNR IN RAPIDLY ROTATED METALS By - Nottingham eTheses ...

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The rotors used in this work were manufactured from glass
fibre rods produced in the laboratory. Continuous 20 end roving
pre-impregnated s glass E747, made by U. S. Polymeric Inc. and
generously supplied by British Aerojet Ltd. was wound under a
resin mix: Epikote 828/Epikote JPA/BDMA accelerator using a
coil winder especially adapted for the purpose(59). The result-
ing rods were cured in a temperature-controlled oven. Rotors
manufactured from the material produced from a simple hoop wind-
ing pattern of the glass fibres were unsatisfactory because the
axial strength provided by the resin mix was insufficient to with-
stand speeds in excess of 5 kHz. To overcome this problem the
coil winder was further modified to produce 300 helical windings.
Although the material so produced had the required axial strength
the pointed outer edges of the rotors tended to delaminate upon
impact with the stator. Generally, the most reliable rotor mater-
ials were those produced by combining an initial helical winding
pattern with a hoop wound outer ring. Rotors manufactured from
a composite material made by hoop winding the glass fibre rovings
on to a thin tube of glass cloth wrap proved equally robust.
4.4 THE FOIL BEARING ROTOR SYSTEM
4.4.1 INTRODUCTION
A foil bearing is formed between a flexible member and a rigid
surface. Considering Figure 4.3 the foil is wrapped around the
circular shaft and held under tension. As the shaft is rotated
gas is drawn between the shaft and the foil by viscous drag. In
a central region both the gap and the pressure are uniform: the