kemet tin 2 0 02 35b 2 9 0 09 80c 1 cast iron 2 0 05 75c 2 9 0 15 85______________________________________ as can be seen from table 3 all samples had driving force gf values after 10 hours had elapsed which exceeded a target value thus demonstrating practical utility however samples b 2 c 1 and c 2 which had center line average heights ra in the range of 0 05 u03bcm u2266 ra u2266 0 2 u03bcm had a small reduction in driving force gf after 10 hours had elapsed thus samples b 2 c 1 and c 2 are markedly preferable performance evaluations starting thrust gf and no load speed mm sec after 20 minutes had elapsed were performed with relative motion members having varying center line average heights as shown in table 4 more specifically relative motion members were prepared with longitudinal direction polishing streaks such as fig3 d and combined with elastic members 2 which were formed in a manner completely similar to those of examples one through three the experimental conditions and the results are shown in table 4 table 4______________________________________experimental conditions experimental resultscenter line average height starting thrust no load speedra gf mm sec ______________________________________0 04 71 700 05 150 1000 20 155 1050 40 158 1070 60 160 1120 80 161 1121 00 165 1131 10 89 82______________________________________ note denotes conditions outside the range of the preferred embodiment of.