Gear Story

As we continue our research on interactive physical systems, we’re developing tools to speed up the process for fabrication. And as our designs increase in complexity, they’ll require an increasing number of actuators. Having an automated system for creating these components will help to better our designs, so here’s our first step in the process: a parametric model which generates gears.

The end goal here is to create something akin to Archimedes Lever. But for now, the impetus behind this Grasshopper definition was a basic light shelf mockup we recently hacked together. We’re beginning an office remodel this summer, and during early design, we studied the efficacy of using a light shelf in the space (we referred to this project as a demo in a previous post). We created a physical mockup based on the section diagram below:


The mockup involved recycling some plywood leftover from parking day, laser cutting a sheet of chipboard, and borrowing a roll of large format bond paper from our plotter. We connected a stepper motor to an Arduino, added a light sensor, and also hooked up an XBee to provide a wireless shading override from the computer:


For this mockup, the pain points were the gears. Since we were putting this model together quickly, the gears were modeled on the fly and were modeled crudely. The teeth were neither cycloidal nor involute, so the gears were loud and would often skip. Not a big deal for this mockup, but the process did give us a reason to look into gear modeling which would increase smoothness and accuracy for future uses.

The system we’ve set up so far is for the creation of involute gears (cycloidal gears are arguably obsolete). The Grasshopper definition references a list of tangent circles (two or more) and creates involute gears by referencing those circles as the gear’s pitch diameter (Ref.1, Ref.2). From this, we can create a few different gear types: spurred, helical, and herringbone. We’ve also added functionality to model out-of-plane gears like worms, miters, and helical miters.

The gear generator will have some decent applications for fabrication, including setting up kinetic systems, creating custom tools, and designing flexible jigs and molds. Stay tuned for more.

UPDATE: check out this post for a basic version of the GH definition.


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  • Daniel

    Hi I was wondering if I could somehow get an update when this program progress?