add worm_dist

gears.scad

@@ -2233,6 +2233,7 @@ module worm(
         assert(is_finite(gear_spin))
         assert(is_finite(profile_shift) && abs(profile_shift)<1);
     helical = asin(starts * circ_pitch / PI / d);
+fda=    echo(helical=helical);
     trans_pitch = circ_pitch / cos(helical);
     vnf = worm(
         circ_pitch=circ_pitch,
@@ -2369,6 +2370,7 @@ function worm_gear(
         pr = pitch_radius(circ_pitch, teeth,helical),
         hob_rad = worm_diam / 2 + crowning,
         thickness = worm_gear_thickness(circ_pitch=circ_pitch, teeth=teeth, worm_diam=worm_diam, worm_arc=worm_arc, crowning=crowning, clearance=clearance),
+        dfda=echo("------->"),
         tooth_profile = _gear_tooth_profile(
             circ_pitch=circ_pitch,
             teeth=teeth,
@@ -2379,6 +2381,7 @@ function worm_gear(
             profile_shift=profile_shift,
             center=true
         ),
+        feeg=echo("<----------"),
         tbot = min(column(tooth_profile,1)),
         arcthick = hob_rad * sin(worm_arc/2) * 2,
         twist = sin(helical)*arcthick / (2*PI*pr) * 360,
@@ -2566,6 +2569,7 @@ function _gear_tooth_profile(
     prad = pitch_radius(circ_pitch, teeth, helical=helical),
     brad = _base_radius(circ_pitch, teeth, pressure_angle, helical=helical),
     rrad = _root_radius(circ_pitch, teeth, clearance, helical=helical, profile_shift=profile_shift, internal=internal),
+fgdg=    echo(pitchrad=prad,outerrad=arad,rootrad=rrad),
     
     srad = max(rrad,brad),
     tthick = circ_pitch/PI / cos(helical) * (PI/2 + 2*profile_shift * tan(pressure_angle)) + (internal?backlash:-backlash),
@@ -3153,12 +3157,42 @@ function worm_gear_thickness(circ_pitch, teeth, worm_diam, worm_arc=60, crowning
     ) thickness;
 
 
+// Function: worm_dist()
+// Synopsis: Returns the distance between a worm and a worm gear
+// Topics: Gears, Parts
+// See Also: worm(), worm_gear(), pitch_radius(), outer_radius()
+// Usage:
+//   dist = worm_dist(mod=|diam_pitch=|circ_pitch=, d, starts, teeth, [profile_shift], [pressure_angle=]);
+// Description:
+//   Calculate the distance between the centers of a worm and its mating worm gear, taking account
+//   possible profile shifting of the worm gear.
+// Arguments:
+//   d = diameter of worm
+//   starts = number of starts of worm
+//   teeth = number of teeth on worm gear
+//   profile_shift = profile shift of worm gear
+//   ---
+//   mod = The metric module/modulus of the gear, or mm of pitch diameter per tooth.
+//   diam_pitch = The diametral pitch, or number of teeth per inch of pitch diameter.  Note that the diametral pitch is a completely different thing than the pitch diameter.
+//   circ_pitch = distance between teeth around the pitch circle.
+//   pressure_angle = The pressure angle of the gear.
+
+function worm_dist(d,starts,teeth,mod,profile_shift=0,diam_pitch,circ_pitch,pressure_angle=20) =
+  let(
+      mod = module_value(mod=mod,diam_pitch=diam_pitch,circ_pitch=circ_pitch),
+      lead_angle = asin(mod*starts/d),
+      pitch_diam = mod*teeth/cos(lead_angle)
+  )
+  (d+pitch_diam)/2 + profile_shift*mod;
+
+
+
 // Function: gear_dist()
 // Synopsis: Returns the distance between two gear centers for spur gears or parallel axis helical gears.
 // Topics: Gears, Parts
 // See Also: worm(), worm_gear(), pitch_radius(), outer_radius()
 // Usage:
-//   dist = gear_dist(mod=|diam_pitch=|circ_pitch=, teeth1, teeth2, [helical], [profile_shift1], [profile_shift2], [pressure_angle=]);
+//   dist = gear_dist(mod=|diam_pitch=|circ_pitch=, teeth1, teeth2, [helical], [profile_shift1], [profile_shift2], [pressure_angle=], [backlash=]);
 // Description:
 //   Calculate the distance between the centers of two spur gears gears or helical gears with parallel axes,
 //   taking into account profile shifting and helical angle.  You can give the helical angle as either positive or negative.