The worm is stationary. Input is the rack runway fixed to the worm bearing. The pink curve is locus of a point on rack pitch line (a space involute of a circle?).
Worm: Helix angle B1 = 30 deg., left hand
Rack: Helix angle B2 = 0 deg.
Angle between worm axle and rack moving direction is L = 30 deg.