I've used an ABEC7 bearing for rollers in line. Let the bearing in mineral oil some time to get a smooth and faster turning.

For the Helix I used, openscad. As my first desing do not judge me

linear_extrude(height = 120, slices = 100, center = false, convexity = 10, twist = 130, $fn = 100){ difference() { difference() {translate([-20,0])circle(20, $fn=100);translate([-20,0])circle(19.5, $fn=100);} ;{translate([-40,0])square(200) ;} ;} } linear_extrude(height = 120, slices = 100, center = false, convexity = 10, twist = 130, $fn = 100){

difference() { difference() {translate([19.5,0])circle(20, $fn=100);translate([19.5,0])circle(19.5, $fn=100);} ;{translate([-0.5,-40])square(40) ;} ;} }