molded with end 128 are angled slightly toward each other an upper end of retainer arm 130 terminates in an outwardly angled portion 134 similarly an upper end of retainer arm 132 terminates in an outwardly angled portion 136 a hairpin shaped hub guide 138 integrally molded with end 128 terminates in a part circular hub retainer 140 part circular hub retainer 140 has a center 142 indicated by a symbol a part circular back up rib 144 disposed outside part circular hub retainer 140 has its center co located with center 142 it will be noted that center 142 is located upward beyond the closest approach of retainer arms 130 and 132 also retainer arms 130 and 132 extend further outward from end 128 than do outwardly angled portion 134 and 136 as shown in fig8 and 9 a flex rim wheel 146 includes a central disk 148 and a thin flexible rim 150 a plurality of spokes 152 best seen in fig9 extend diagonally from a perimeter of central disk 148 to retain central disk 148 in a concentric position preferably a small number of spokes 152 preferably three is combined with a thin cross section in rim 150 in order to provide substantial deformability in rim 150 central disk 148 includes a hub 154 protruding toward end 128 fig1 a ring 156 concentric with hub 154 is disposed at a radius substantially equal to a radius of part circular back up rib 144 fig6 and 7 at the side opposite to that containing hub 154 central disk 148 includes a guide disk 158 having a blind hole 160 centered therein a septum 162 spans the diameter of blind hole 160 in fig8 a guide rod 164 passes loosely through an axial bore 166 in brush spindle 65.