From 23b8aa0618e67514648aa715bd0b4be5ded99c85 Mon Sep 17 00:00:00 2001
From: Werner Almesberger <werner@openmoko.org>
Date: Wed, 4 Aug 2010 21:57:03 -0300
Subject: [PATCH] Initial commit. Just the HeeksPython script to generate the
 solids for now.

---
 cw.py | 207 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 207 insertions(+)
 create mode 100755 cw.py

diff --git a/cw.py b/cw.py
new file mode 100755
index 0000000..80f360e
--- /dev/null
+++ b/cw.py
@@ -0,0 +1,207 @@
+#!/usr/bin/python
+
+import sys, math
+
+
+group = None
+g = 9.81	# gravitational acceleration, m/s2
+
+# density, g/cm3
+
+density = 11.34	# pure lead (Pb)
+density =  9.31	# Pb50Sn50
+density = 10.00	# Pb67Sn33
+#density =  7.28	# pure tin (Sn)
+
+#
+# The z coordinate of the plane limiting the top of the counterweight. This is
+# the altitude of the board surface minus the board clearance.
+#
+z_ceiling = 5.0	# mm
+
+#
+# The y coordinate of the axis around which our system rotates, i.e., the
+# position of the center of the rear feet
+#
+y_axis = 16.0
+
+total_mass = 0
+total_torque = 0
+
+
+#
+# solve a quadratic equation of the form a*x^2+b*x+c = 0
+#
+
+def qeq(a, b, c):
+    d = math.sqrt(b*b-4*a*c)
+    return ((-b-d)/2/a, (-b+d)/2/a)
+
+
+#
+# find the x-coordinate of the center of mass of a trapezoid/trapezium with the
+# four corners (0, 0), (x, 0), (0, y0), and (x, y0)
+# we assume the mass distribution to be uniform
+#
+
+def cm_trap_a(x, y0, y1):
+    if y0 == y1:
+	return x/2.0
+    f = float(y1-y0)/x/2
+    return qeq(2*f, 2.0*y0, -x*(y0+y1)/2.0)[1]
+
+
+#
+# calculate a rectangle's contribution to mass and torque
+#
+
+def rect_calc(x0, y0, z0, x1, y1, z1):
+    global total_mass, total_torque
+
+    # mass, in g
+    m = (x1-x0)*(y1-y0)*(z_ceiling-(z0+z1)/2.0)*density/1e3;
+
+    # center of mass on y axis, in y coordinates (mm)
+    y_center = y0+cm_trap_a(y1-y0, z_ceiling-z0, z_ceiling-z1)
+
+    # weight, in N
+    w = m*g/1000.0
+
+    # torque, in Nm
+    t = w*(y_center-y_axis)/1000.0
+
+    total_mass += m
+    total_torque += t
+
+#
+# gnuplot a rectangle
+#
+
+def rect_gnuplot(x0, y0, z0, x1, y1, z1):
+    print x0, y0, z0
+    print x1, y0, z0
+    print x1, y1, z1
+    print x0, y1, z1
+    print x0, y0, z0
+    print
+    print
+
+
+#
+# add a rectangle to the CAD model
+#
+
+def do_rect_cad(x0, y0, z0, x1, y1, z1):
+    cad.sketch()
+    sk = cad.getlastobj()
+
+    cad.line3d(x0, y0, z0, x1, y0, z0)
+    line = cad.getlastobj()
+    cad.add(sk, line)
+
+    cad.line3d(x1, y0, z0, x1, y1, z1)
+    line = cad.getlastobj()
+    cad.add(sk, line)
+
+    cad.line3d(x1, y1, z1, x0, y1, z1)
+    line = cad.getlastobj()
+    cad.add(sk, line)
+
+    cad.line3d(x0, y1, z1, x0, y0, z0)
+    line = cad.getlastobj()
+    cad.add(sk, line)
+
+    cad.reorder(sk)
+
+    return sk
+
+
+def rect_cad(x0, y0, z0, x1, y1, z1):
+    global group
+
+    sk = do_rect_cad(x0, y0, z0, x1, y1, z1)
+
+    cad.extrude(sk, 3)
+
+    if group is None:
+	group = cad.getlastobj()
+    else:
+	cad.fuse(group, cad.getlastobj())
+	group = cad.getlastobj()
+
+
+#
+# add a rectangle with the following corners:
+# (x0, y0, z0)
+# (x1, y0, z0)
+# (x0, y1, z1)
+# (x1, y1, z1)
+#
+
+def rect(x0, y0, z0, x1, y1, z1):
+    rect_calc(x0, y0, z0, x1, y1, z1)
+    do(x0, y0, z0, x1, y1, z1)
+
+
+#
+# make the base
+#
+
+def make_base():
+    rect(16,   46.0, 2.6,  22,   55,   2.6)	# left lateral, bottom
+    rect(22,   46.0, 3.7,  24,   55,   3.7)	# on pedestal
+    rect(89.5, 46.0, 2.6,  99.5, 55,   2.6)	# right lateral, bottom
+    rect(88,   46.0, 3.7,  89.5, 55,   3.7)	# on pedestal
+
+    rect(29.5, 50.5, 3.7,  36,   55,   3.7)	# left podium, to beam
+    rect(38.5, 50.5, 3.7,  41,   55,   3.7)	# after beam
+    rect(71,   50.5, 3.7,  82,   55,   3.7)	# right podium
+
+    rect(16,   55,   2.6,  36,   59.5, 3.9)	# middle bar, to 1st beam
+    rect(38.5, 55,   2.6,  46,   59.5, 3.9)	# between beams
+    rect(48,   55,   2.6,  99.5, 59.5, 3.9)	# right of 2nd beam
+
+    rect(36,   56,   3.9,  38.5, 59.5, 3.9)	# cover the beams
+    rect(46,   56,   3.9,  48,   59.5, 3.9)
+
+    rect(15,   59.5, 3.9,  60.5, 64,   3.9)	# end bar, left of beam
+    rect(62.5, 59.5, 3.9, 100, 64,   3.9)	# right of beam
+
+    rect(15,   64,   3.9,  34,   69,   3.9)	# left "ear"
+    rect(89.5, 64,   3.9, 100,   69,   3.9)	# right "ear"
+
+    rect(34,   64,   3.9,  60.5, 65,   3.9)	# extend inner area to sponge
+    rect(62.5, 64,   3.9,  82.5, 65,   3.9)
+
+
+if __name__ == "__main__":
+    do = rect_gnuplot
+else:
+    import HeeksPython as cad
+    do = rect_cad
+
+make_base()
+
+#if __name__ !=  "__main__":
+#    sk = do_rect_cad(10, 40, z_ceiling, 110, 70, z_ceiling)
+#    cad.extrude(sk, 3)
+#    sk = cad.getlastobj()
+#    cad.cut(group, sk)
+#    group = cad.getlastobj()
+#    cad.translate(group, -15, -69, -5)
+#    cad.rotate(group, 0, 0, 0, 1, 0, 0, math.pi)
+
+#
+# add rectangular block for mold, then subtract the counterweight
+#
+
+if __name__ !=  "__main__":
+    cad.translate(group, -15, -46, -5)
+    cad.translate(group, 18, 5, 0)
+    sk = do_rect_cad(0, 0, 0,  120, 45, 0)
+    cad.extrude(sk, -10)
+    sk = cad.getlastobj()
+    cad.cut(sk, group)
+
+print >>sys.stderr, "total mass =", total_mass, "g"
+print >>sys.stderr, "total torque =", total_torque*1000.0, "mNm"