h = 80;
r = 40;
d = 0.75;
// With d=0.75:
// At r=70, h=100 it's 3:42 and 18 meters
// At r=70, h=50 it's 2:08 and 10.4 meters
// At r=25.4, h=50 it's 1:34 and 3.1 meters
// At r=25.4, h=100 it's 3:06 and 5.9 meters
// At r=40, h=80 it's 2:37 and 7.9 meters
// With d=0.5 or d=0.6 or d=0.7 it crashes Slic3r
difference() {
cylinder(r=r, h=h);
translate([0, 0, d]) cylinder(r=r-d, h=h);
}