rack: add property pitch (read-only), make length of rack match pitch…

… x teeth

freecad/gears/features.py

@@ -206,6 +206,8 @@ def __init__(self, obj):
         obj.addProperty(
             "App::PropertyBool", "properties_from_tool", "gear_parameter", "if beta is given and properties_from_tool is enabled, \
             gear parameters are internally recomputed for the rotated gear")
+        obj.addProperty("App::PropertyLength", "transverse_pitch",
+            "computed", "pitch in the transverse plane", 1)
         obj.addProperty("App::PropertyPythonObject", "rack", "test", "test")
         obj.rack = self.involute_rack
         obj.teeth = 15
@@ -229,10 +231,8 @@ def execute(self, fp):
         fp.rack.head = fp.head
         # checksbackwardcompatibility:
         if "clearence" in fp.PropertiesList:
-            print(fp.clearence)
             fp.rack.clearence = fp.clearence
         if "properties_from_tool" in fp.PropertiesList:
-            print(fp.properties_from_tool)
             fp.rack.properties_from_tool = fp.properties_from_tool
         fp.rack._update()
         pts = fp.rack.points()
@@ -254,6 +254,9 @@ def execute(self, fp):
             pol2.translate(
                 fcvec([0., np.tan(beta) * fp.height.Value, fp.height.Value]))
             fp.Shape = makeLoft([pol, pol2], True)
+        # computed properties
+        if "transverse_pitch" in fp.PropertiesList:
+            fp.transverse_pitch = "{} mm".format(fp.rack.compute_properties()[2])
 
     def __getstate__(self):
         return None

pygears/involute_tooth.py

@@ -177,35 +177,46 @@ def _update(self):
                       properties_from_tool=self.properties_from_tool)
 
     def points(self, num=10):
-        if self.properties_from_tool:
-            pressure_angle_t = arctan(tan(self.pressure_angle) / cos(self.beta))
-            m = self.m / cos(self.beta)
-            m_n = self.m
-        else:
-            pressure_angle_t = self.pressure_angle
-            m = self.m
-            m_n  = self.m
+        m, m_n, pitch, pressure_angle_t = self.compute_properties()
 
         a = (2 + self.head + self.clearence) * m_n * tan(pressure_angle_t)
-        b = (m * pi) / 4 - (1 + self.head) * m_n * tan(pressure_angle_t)
+        b = pitch / 4 - (1 + self.head) * m_n * tan(pressure_angle_t)
         tooth = [
             [-m_n * (1 + self.clearence), -a - b],
             [m_n * (1 + self.head), -b],
             [m_n * (1 + self.head), b],
             [-m_n * (1 + self.clearence), a + b]
         ]
         teeth = [tooth]
-        trans = translation([0., m * pi, 0.])
+        trans = translation([0., pitch, 0.])
         for i in range(self.z - 1):
             teeth.append(trans(teeth[-1]))
         teeth = list(np.vstack(teeth))
-        teeth.append(list(teeth[-1]))
-        teeth[-1][0] -= self.thickness
-        teeth.append(list(teeth[0]))
+        ext1 = np.array(teeth[0]) + np.array([0., a + b - pitch / 2])
+        ext2 = np.array(teeth[-1]) - np.array([0., a + b - pitch / 2])
+        print(ext1, ext2)
+        teeth = [ext1.tolist(), ext1.tolist()] + teeth + [ext2.tolist(), ext2.tolist()]
+        #teeth.append(list(teeth[-1]))
+        teeth[0][0] -= self.thickness
+        #teeth.append(list(teeth[0]))
         teeth[-1][0] -= self.thickness
         teeth.append(teeth[0])
         return(teeth)
 
+    def compute_properties(self):
+        if self.properties_from_tool:
+            pressure_angle_t = arctan(tan(self.pressure_angle) / cos(self.beta))
+            m = self.m / cos(self.beta)
+            m_n = self.m
+        else:
+            pressure_angle_t = self.pressure_angle
+            m = self.m
+            m_n  = self.m
+
+        pitch = m * np.pi
+        return m, m_n, pitch, pressure_angle_t
+
+
 
 if __name__ == "__main__":
     from matplotlib import pyplot