openscad parametric wheel

$fn=48;

base_d = 50;
base_h = 10;

center_d = 10;

axes_count = 5;
angle = 360/axes_count;

difference(){
    union(){
        difference(){
            union(){
                difference(){
                    cylinder(d=base_d, h=base_h);

                    translate([0,0,-base_h])
                    cylinder(d=base_d*0.8, h=base_h*3);
                };

                for(a=[0:axes_count-1]){
                    rotate([0,0,a*angle])
                    linear_extrude(height=base_h)
                    polygon([[0,0], [base_d/10, base_d/2*0.9], [-base_d/10, base_d/2*0.9]]);
                };
             };

            translate([0,0,base_h*0.9])
            cylinder(d=base_d*0.9, h=base_h*3);
         };

        cylinder(d=center_d, h=base_h);
     };

    translate([0,0,-base_h])
    cylinder(d=center_d*0.5, h=base_h*3);
};