Violet crank carrying orange block of small gear (pitch radius R2) and small worm (1 start, lead: t1, pitch radius: R3).
Green large worm: 2 starts, lead: t2 = 2.t1, pitch radius: R4 = 2.R3.
Grey internal gear (pitch radius R1 = 4.R2) is stationary.
V4 = Vc(1+A)
V4: velocity of the green worm
Vc: velocity of the violet crank
A = (R3/R4).(R1/R2); in this video A = 2 so V4 = 3Vc
The violet crank and the green worm rotate in the same direction.