An experimental comparison between the performance of a ‘total cross flow’ and an equivalent conventional design hydrostatic journal bearing

This paper presents the results of an experimental investigation into the advantages of a “Total Cross Flow” bearing design over an equivalent conventional hydrostatic bearing. Practical designs of journal and thrust hydrostatic bearings embodying the features of “Total Cross Flow” (TCF), “External Return Flow System” (ERFS) and “Grooved Lands” are described. The bearings set-up in a journal and journal plus double thrust arrangement are evaluated. For a 75 mm diameter journal hydrostatic TCF bearing steady speeds up to 1 million DN have been reached so far. With the properties of good damping, stiffness and low temperature rise the TCF hydrostatic bearings are considered suitable for wide speed range machine tool spindle applications. Experimental comparisons between the performance of TCF design and equivalent conventional pocket and flat land hydrostatic journal bearings clearly demonstrate the advantage of the former particularly in terms of much higher running speed capability with no penalty in temperature rise and shear power losses. Furthermore pocket pressure stability with respect to increased shaft speed for TCF journal bearings tested up to 1 million DN is over 4 times better than that for the equivalent conventional design tested up to 0.6 million DN with a similar temperature rise.