need eqaution of an helix that's spiraling down another helix

[azoulay]

Hi everyoneone,

the plotting of only ONE helix is pretty easy because the center of the helix is the Y axis.

I cannot figure out how to use (instead of the Y axis) an helix as the center of a second helix.
(Basically I want to plot a second helix that's spiraling down another Helix)

Does someone know the trick ?

I have this equation as the equation of the first helix:

r(t)=( Rcos(w*t), Kt, Rsin(w*t) )

what would be the equation of the second helix ?
(See diagram)

thanks,
Jonathan