$fn = 50;
tube_length = 4; // tube length in studs
piston_length = 3; // piston length in studs
travel_length = piston_length-2; // piston travel in studs
top_type = "axle"; // top mounting type: 'pin' = pin hole, 'ball' = ball end hole, 'axle' = axle hole, "axle_rod" = axle, "ball_end" = ball
bottom_type = "ball"; // bottom mounting type

travel = min(travel_length, piston_length-2, tube_length-2);

//difference() { union() {

difference() {
  tube_offset = (bottom_type == "axle" || bottom_type == "axle_rod" ? 1 : (bottom_type == "ball_end" ? 0.4 : 0));
  union() {
    translate([0, 0, 8]) cylinder(r=4, h=tube_length*8-8);
    mount_base(type=bottom_type, r=4);
  }
  mount_hole(bottom_type);
  translate([0, 0, 8+tube_offset]) cylinder(r=3.2, h=tube_length*8-tube_offset);
  translate([-5, -0.5, tube_length*8-6]) cube(size=[10, 1, 3], center=false);
}

color([1, 0.5, 0.5]) translate([0, 0, (tube_length+piston_length-1)*8]) rotate([180, 0, 0])
{
  difference() {
    union() {
      //translate([0, 0, 4]) cylinder(r=3, h=piston_length*8-4);
      //rotate([90, 0, 0]) translate([0, 4, -4]) cylinder(r=4, h=8);
      translate([0, 0, 8]) cylinder(r=3, h=piston_length*8-8);
      mount_base(top_type);
    }
    mount_hole(top_type);
    translate([-5, -0.7, (piston_length-travel-1)*8+3]) cube(size=[10, 1.4, travel*8+3], center=false);
  }
}

//rotate([90, 0, 0])
color([0.5, 0.5, 1]) translate([-4, -0.5, tube_length*8-6])
cube(size=[8, 1, 3], center=false);

//} translate([0, -50, -1]) cube(size=[10, 500, 500]); }

//rotate([10, 0, 0]) axleround(h=8);

module mount_base(type, r = 3) {
  if (type == "pin" || type == "ball" || type == "axle") {
    cylinder(r=4, h=8+0.1);
  }
  else if (type == "axle_rod") {
    axleround(h=8+0.1);
  }
  else if (type == "ball_end") {
    translate([0, 0, 4]) sphere(r=3);
    translate([0, 0, 6]) linear_extrude(scale=r, height=2) circle(r=1);
  }
}

module mount_hole(type) {
  if (type == "pin") {
    rotate([90, 0, 0]) translate([0, 4, -4]) pin_hole();
  }
  else if (type == "ball") {
    ball_end_n();
  }
  else if (type == "axle") {
    translate([0, 0, -0.1]) axleround(h=8+0.1, axleradius=2.4, axlemesh=1.85);
    translate([0, 0, -0.1]) cylinder($fs=0.5, h=0.8+0.1, r=5);
  }
}

// cut for ball end
module ball_end_n() {
  translate([0, 0, 4]) sphere(r=3.05);
  translate([0, 0, 2.3-0.1]) cylinder(r=2.9, h=2);
  translate([0, 0, -0.1]) cylinder(r=5, h=2.4);
}

module axleround(h = 24, axleradius = 2.3, axlemesh = 1.7) {
  difference() {
    cylinder($fn=16, r=axleradius, h=h);
    translate([axlemesh/2, axlemesh/2, -1]) cube([axleradius, axleradius, h+2]);
    translate([axlemesh/2, -axlemesh/2-axleradius, -1]) cube([axleradius, axleradius, h+2]);
    translate([-axlemesh/2-axleradius, axlemesh/2, -1]) cube([axleradius, axleradius, h+2]);
    translate([-axlemesh/2-axleradius, -axlemesh/2-axleradius, -1]) cube([axleradius, axleradius, h+2]);
  }
}

module pin_hole(height=8) {
  union() {
    translate([0, 0, -0.1]) cylinder($fs=0.5, h=height+0.2, r=2.5);
    translate([0, 0, -0.1]) cylinder($fs=0.5, h=0.8+0.1, r=3);
    translate([0, 0, height-0.8]) cylinder($fs=0.5, h=0.8+0.1, r=3);
  }
}