Custom addendum and dedendum radii

[dylanede]

Hi, and thanks for providing this great library.

Currently, the addendum and dedendum radii are not configurable, and controlled by the constants ka and kd in GearBase. Would it be possible to expose options to override these values, and/or specify the radii directly? I am currently trying to replicate some existing gears whose radii do not match those calculated by this library. If you provide some direction on how you think such a feature would be incorporated into the API, I'm happy to put together a PR.

Thanks!

[meadiode]

Hi, you can configure those constants by simply creating a class inherited from SpurGear like so:

class CustomGear(SpurGear):
    ka = 1.3
    kd = 1.1

Then use this CustmGear just like SpurGear:

gear1 =   SpurGear(module=1.0, teeth_number=17, width=5.0, bore_d=5.0)
gear2 = CustomGear(module=1.0, teeth_number=17, width=5.0, bore_d=5.0)

wp = cq.Workplane('XY').gear(gear1).moveTo(20, 0).addGear(gear2)

print('gear1 dedendum radius:', gear1.rd)
print('gear2 dedendum radius:', gear2.rd)

The result:

Initially I figured that since these coefficients need to be changed only in some special cases, I didn't expose them in e.g. a constructor or a method, thinking that one can just override them in an inherited class, or just directly override them like SpurGear.kd = 1.05 etc.