which extends through an aperture or hole in the partition 82 at the end of which there is a flange 100 flush against the platform 82 the stem 92 has an end part 102 of smaller diameter fitting on this part is metal foot member or support 104 which is held on by a flange 106 on the part 102 of smaller diameter as may readily be seen access may be had to the head 94 of the threaded stem through an opening 110 in the top wall of the base section the stem may be rotated so to adjust the vertical supporting position of the foot member 104 fig4 and 6 are enlarged views which show the structure at the bottom part of the module 10 and of the rotor 30 a bottom plate of the rotor 30 is designated at 120 of fig5 the rotor bottom 120 has side flanges 122 and 124 a plate 126 has side flanges 130 and 132 and further edge flanges 134 and 136 plate 126 is spaced as shown from the bottom plate 120 flanges 134 and 136 seating against the bottom 120 and the inside of flanges 122 and 124 plate 126 has a circular ring shaped depression 140 formed in it as shown which forms a part of a ball race for balls 142 the top of the bottom frame or base section 14 is designated at 144 the base top 144 has a similar circular ring shaped depression 146 in it which is opposite to and complementary with.