// Geometry of the sliding piece of the IC abacus 
// Last edited on 2003-09-18 21:45:07 by stolfi
//
// Requires
//     ic_abacus_slider_angle       = angle between chamfer and flat face, in degrees
//
// Defines 
//  ic_abacus_slider  = 
//     the slider piece, outer radius = 1, thickness = 2*ic_abacus_slider_HY
//     centered on the origin and threaded on the Y axis.

// Basic proportions of a slider:
//   These are relative to the slider's overall radius:
//     ic_abacus_slider_width       = thickness of sliders (along hole)
//     ic_abacus_slider_round_min_R = radius of filet around rim
//     ic_abacus_slider_sin_t       = sin of angle between chamfer and base of slider
//     ic_abacus_slider_cos_t       = cos of angle between chamfer and base of slider
//     ic_abacus_slider_hole_R      = radius of slider hole
//     ic_abacus_slider_flat_R      = radius of flat part around hole

#declare ic_abacus_slider_width       = 1.10;
#declare ic_abacus_slider_hole_R      = 0.32;
#declare ic_abacus_slider_flat_R      = 0.50;

#declare ic_abacus_slider_sin_t       = sin(radians(ic_abacus_slider_angle));
#declare ic_abacus_slider_cos_t       = cos(radians(ic_abacus_slider_angle));

#declare ic_abacus_slider_HY = ic_abacus_slider_width / 2;

#declare ic_abacus_slider_round_min_R = 
  (ic_abacus_slider_HY*ic_abacus_slider_cos_t - (1-ic_abacus_slider_flat_R)*ic_abacus_slider_sin_t) / (1 - ic_abacus_slider_sin_t);

#declare ic_abacus_slider_round_maj_R  =  
  1 - ic_abacus_slider_round_min_R;

#declare ic_abacus_slider_round_HY  =  
  ic_abacus_slider_round_min_R * ic_abacus_slider_cos_t;

#declare ic_abacus_slider_cap_base_Y  =  
  ic_abacus_slider_round_HY;

#declare ic_abacus_slider_cap_base_R  =  
  ic_abacus_slider_round_maj_R  + ic_abacus_slider_round_min_R / ic_abacus_slider_sin_t;

#declare ic_abacus_slider_cap_height  =  
  ic_abacus_slider_cap_base_R * (ic_abacus_slider_sin_t / ic_abacus_slider_cos_t);

#declare ic_abacus_slider_cap_join_R  =  
  ic_abacus_slider_round_maj_R  + ic_abacus_slider_round_min_R * ic_abacus_slider_sin_t;

#declare ic_abacus_slider_bounder =
  cylinder{
    <0, -ic_abacus_slider_HY, 0>, 
    <0, +ic_abacus_slider_HY, 0>, 
    1.0
  }

#declare ic_abacus_slider_joiner_cyl =
  cylinder{
    <0, -ic_abacus_slider_HY, 0>, 
    <0, +ic_abacus_slider_HY, 0>, 
    1.00001*ic_abacus_slider_cap_join_R
  }

#declare ic_abacus_slider_cap_cone =
  cone{
    <0, -0.0001*ic_abacus_slider_cap_height, 0>, 1.0001*ic_abacus_slider_cap_base_R 
    <0, ic_abacus_slider_cap_height, 0>, 0
  }

#declare ic_abacus_slider_caps =
  intersection{
    merge{
      object{ic_abacus_slider_cap_cone}
      object{ic_abacus_slider_cap_cone scale <1,-1,1>}
    }
    object{ic_abacus_slider_joiner_cyl}
  }

#declare ic_abacus_slider_round =
  difference{
    torus{ic_abacus_slider_round_maj_R, ic_abacus_slider_round_min_R}
    object{ic_abacus_slider_joiner_cyl scale <0.99999, 1.00001, 0.99999>}
  }

#declare ic_abacus_slider_hole =
  cylinder{
    <0, -1.1*ic_abacus_slider_HY, 0>, 
    <0, +1.1*ic_abacus_slider_HY, 0>, 
    ic_abacus_slider_hole_R
  }

#declare ic_abacus_slider =
  difference{
    merge{
      object{ic_abacus_slider_caps}
      ic_abacus_slider_round
    }
    object{ic_abacus_slider_hole}
    bounded_by{object{ic_abacus_slider_bounder scale 1.0001}}
  }