include <BOSL/constants.scad>;
use <BOSL/metric_screws.scad>;
$fn=100;

thread = [
	4, // diameter
	6 // depth
];

thickness = 1.2;
gap = 0.4;

pipe_diameter = 8;

module multi_helix( length, diameter, count = 4) {
	factor = 90*length/diameter;
	for( f = [factor, -factor])
		linear_extrude( length, center = true, slices=length/2, twist = f)
			for( i = [0:count-1])
				rotate( [0, 0, 360/count*i])
					translate( [diameter/2, 0, 0])
						children();
}
difference() {
	cylinder( h=50, d=20, center=true);
	cylinder( h=50+0.1, d=20-2*thickness, center=true);
}
intersection() {
	multi_helix( 50, diameter = 20-thickness, count = 4)
		translate( [-thickness,0,0])
			//circle( d=thickness*4);
			square(thickness*2,center=true);
	cylinder( h=50, d=20, center=true);
}