Parameter input for n-sided polygon in sketches

imants_smidchens · May 2021

I found myself designing a configurable 3-sprocket chain for a robotics project, and as I read up on how chain pitch works, I found the simplest way to generate a variable n-toothed sprocket was to define a polygon with n sides and a side length of the chain pitch (seen below)

Image: https://us.v-cdn.net/5022071/uploads/editor/bd/abc99pzadws6.png

Currently the polygon tool does not allow for parameter-driven polygons, as variables are not considered valid expressions.

Image: https://us.v-cdn.net/5022071/uploads/editor/st/8y8cgk4u1anj.png

I realize this is likely because the input for such a polygon must be a natural number, but being able to configure this would be nice.
I also realize I could just define the diameter of the circle to be (# of sides)*(

pitch length)/(pi) and call it good enough, but my brain prefers the geometric visual solution ¯\_(ツ)_/¯

Thanks for your time!

imants_smidchens · May 2021

i found out that the polygon feature acts much like the pattern tool and thus enters a gray area in terms of how it can be edited and create dependency issues - if i delete one face of a pentagon, then change the parameter to be 4 sides, then back to 5, what happens to the deleted face? (and other such issues)
Perhaps a more robust solution (in my case, at least) is to define the circle with an isosceles triangle.

Image: https://us.v-cdn.net/5022071/uploads/editor/pz/73t93l8wq6fo.png

definitely works well enough, at some point i'll get around to writing a featurescript that doesn't have this bothersome intersection issue between chain links

Parameter input for n-sided polygon in sketches

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