Dear @Steve1
I recommend a sweep2 for 1/2 turn
blue = profil / shape / cross
green = rail
copy one rail curve - and use it twice to have same CV structure.
now generate the surface
and
_rotate (copy = yes)
_move to get one full turn
_arrayLinear
building only have of a turn will prevent further trimming issues for the next steps.
you can simplify the surface by optimising the rail and cross…
a setting of the curves like this pink version might give a better result
Thread make2_tp_rh5.3dm (10.1 MB)