1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
|
#! /usr/bin/env python
'''
Copyright (C) 2007 Aaron Spike (aaron @ ekips.org)
Copyright (C) 2007 Tavmjong Bah (tavmjong @ free.fr)
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
'''
import inkex
import simplestyle, sys
from math import *
import string
def involute_intersect_angle(Rb, R):
Rb, R = float(Rb), float(R)
return (sqrt(R**2 - Rb**2) / (Rb)) - (acos(Rb / R))
def point_on_circle(radius, angle):
x = radius * cos(angle)
y = radius * sin(angle)
return (x, y)
def points_to_svgd(p):
f = p[0]
p = p[1:]
svgd = 'M%.5f,%.5f' % f
for x in p:
svgd += ' L%.5f,%.5f' % x
svgd += 'z'
return svgd
class Gears(inkex.Effect):
def __init__(self):
inkex.Effect.__init__(self)
self.OptionParser.add_option("-t", "--teeth",
action="store", type="int",
dest="teeth", default=24,
help="Number of teeth")
self.OptionParser.add_option("-p", "--pitch",
action="store", type="float",
dest="pitch", default=20.0,
help="Circular Pitch (length of arc from one tooth to next)")
self.OptionParser.add_option("-a", "--angle",
action="store", type="float",
dest="angle", default=20.0,
help="Pressure Angle (common values: 14.5, 20, 25 degrees)")
self.OptionParser.add_option("-c", "--centerdiameter",
action="store", type="float",
dest="centerdiameter", default=10.0,
help="Diameter of central hole - 0.0 for no hole")
self.OptionParser.add_option("-u", "--unit",
action="store", type="string",
dest="unit", default="px",
help="unit of measure for circular pitch and center diameter")
def effect(self):
teeth = self.options.teeth
pitch = self.unittouu( str(self.options.pitch) + self.options.unit)
angle = self.options.angle # Angle of tangent to tooth at circular pitch wrt radial line.
centerdiameter = self.unittouu( str(self.options.centerdiameter) + self.options.unit)
# print >>sys.stderr, "Teeth: %s\n" % teeth
two_pi = 2.0 * pi
# Pitch (circular pitch): Length of the arc from one tooth to the next)
# Pitch diameter: Diameter of pitch circle.
pitch_diameter = float( teeth ) * pitch / pi
pitch_radius = pitch_diameter / 2.0
# Base Circle
base_diameter = pitch_diameter * cos( radians( angle ) )
base_radius = base_diameter / 2.0
# Diametrial pitch: Number of teeth per unit length.
pitch_diametrial = float( teeth )/ pitch_diameter
# Addendum: Radial distance from pitch circle to outside circle.
addendum = 1.0 / pitch_diametrial
# Outer Circle
outer_radius = pitch_radius + addendum
outer_diameter = outer_radius * 2.0
# Tooth thickness: Tooth width along pitch circle.
tooth = ( pi * pitch_diameter ) / ( 2.0 * float( teeth ) )
# Undercut?
undercut = (2.0 / ( sin( radians( angle ) ) ** 2))
needs_undercut = teeth < undercut
# Clearance: Radial distance between top of tooth on one gear to bottom of gap on another.
clearance = 0.0
# Dedendum: Radial distance from pitch circle to root diameter.
dedendum = addendum + clearance
# Root diameter: Diameter of bottom of tooth spaces.
root_radius = pitch_radius - dedendum
root_diameter = root_radius * 2.0
half_thick_angle = two_pi / (4.0 * float( teeth ) )
pitch_to_base_angle = involute_intersect_angle( base_radius, pitch_radius )
pitch_to_outer_angle = involute_intersect_angle( base_radius, outer_radius ) - pitch_to_base_angle
centers = [(x * two_pi / float( teeth) ) for x in range( teeth ) ]
points = []
for c in centers:
# Angles
pitch1 = c - half_thick_angle
base1 = pitch1 - pitch_to_base_angle
outer1 = pitch1 + pitch_to_outer_angle
pitch2 = c + half_thick_angle
base2 = pitch2 + pitch_to_base_angle
outer2 = pitch2 - pitch_to_outer_angle
# Points
b1 = point_on_circle( base_radius, base1 )
p1 = point_on_circle( pitch_radius, pitch1 )
o1 = point_on_circle( outer_radius, outer1 )
b2 = point_on_circle( base_radius, base2 )
p2 = point_on_circle( pitch_radius, pitch2 )
o2 = point_on_circle( outer_radius, outer2 )
if root_radius > base_radius:
pitch_to_root_angle = pitch_to_base_angle - involute_intersect_angle(base_radius, root_radius )
root1 = pitch1 - pitch_to_root_angle
root2 = pitch2 + pitch_to_root_angle
r1 = point_on_circle(root_radius, root1)
r2 = point_on_circle(root_radius, root2)
p_tmp = [r1,p1,o1,o2,p2,r2]
else:
r1 = point_on_circle(root_radius, base1)
r2 = point_on_circle(root_radius, base2)
p_tmp = [r1,b1,p1,o1,o2,p2,b2,r2]
points.extend( p_tmp )
path = points_to_svgd( points )
# Embed gear in group to make animation easier:
# Translate group, Rotate path.
t = 'translate(' + str( self.view_center[0] ) + ',' + str( self.view_center[1] ) + ')'
g_attribs = {inkex.addNS('label','inkscape'):'Gear' + str( teeth ),
'transform':t }
g = inkex.etree.SubElement(self.current_layer, 'g', g_attribs)
# Create SVG Path for gear
style = { 'stroke': '#000000', 'fill': 'none', 'stroke-width': str(self.unittouu('1px')) }
gear_attribs = {'style':simplestyle.formatStyle(style), 'd':path}
gear = inkex.etree.SubElement(g, inkex.addNS('path','svg'), gear_attribs )
if(centerdiameter > 0.0):
center_attribs = {'style':simplestyle.formatStyle(style),
inkex.addNS('cx','sodipodi') :'0.0',
inkex.addNS('cy','sodipodi') :'0.0',
inkex.addNS('rx','sodipodi') :str(centerdiameter/2),
inkex.addNS('ry','sodipodi') :str(centerdiameter/2),
inkex.addNS('type','sodipodi') :'arc'
}
center = inkex.etree.SubElement(g, inkex.addNS('path','svg'), center_attribs )
if __name__ == '__main__':
e = Gears()
e.affect()
# vim: expandtab shiftwidth=4 tabstop=8 softtabstop=4 fileencoding=utf-8 textwidth=99
|