Planetary gear set

Planetary gear set with a fixed ring from sources/planetary-set-spec.md (authoritative, text only), built as seven separate solids from five part designs: a 150 x 150 x 5 base plate (the datum), a 48-tooth internal ring rigidly fixed on it, a 24-tooth sun and a D88 x 5 carrier turning about the common z axis, and three identical 12-tooth planets (one design placed three times) turning on the carrier at radius 36. Module 2, pressure angle 20 deg, zero profile shift; every external tooth is thinned 0.10 mm and every ring tooth space widened 0.05 mm at the pitch circle (circular backlash 0.20 mm at the sun meshes, 0.15 mm at the ring meshes). Every gear is phased as specified (sun, ring and carrier at 0 deg, every planet at 15 deg) so all six meshes engage. The sun is motor-driven; each planet follows the sun and the fixed ring through two epicyclic meshes relative to the carrier, and the free carrier is set by those loops. A sweep of the sun checks that the set turns with zero interference and a flank gap of at most 0.2 mm at the sun meshes; the evaluator measures the carrier ratio (carrier angle over sun angle) and the carrier angle after one sun revolution.