Hello, thank you for give me a chance to bid on your project, As you can see in my profile I am a serios worker here, I have very high level on mathematic and physic and I can find your equations but first we need to talk about some details.
1) The arcs must be circunferencial since you refer to constant radius as a parameter.
2) When you say "direction" for the second parameter is that I know the vector (x, y, z) for that parameter?
3) What about the starting point? It is a (0,0,0) or a point that belongs to the arcs?