The goal of this project was to create a 4-part linkage that would allow us to pie someone sitting in a chair directly in the face using a single stepper motor.
A model animation showing the linkages in motion
The cut plywood linkages.
Modeling
I created a model that allowed us to visualize how the linkages could be arranged to best utilize a mechanical advantage. In order to create a "snapping" motion, the back driving link needed to be much smaller than the "throwing" link. This came at the cost of a larger required torque to drive the linkage as a whole. The parts could then be laser-cut and fitted with hardware. Care was taken to make important links flush with one another.
Support / Driving System
In order to drive the linkage, one link needed to be press-fit to the stepper motor dimensions. A plan was designed for a series of legs, to meet a height requirement of 40cm for the pie. Lastly, a holder for the pie tin was designed, cut, and glued to the "throwing" link.
Assembly
Our final linkage design needed to be altered slightly, as the stepper motor did not have the required torque to drive the links. This was fixed by trimming the "throwing" link slightly, at a slight compromise to speed. The base was fabricated with 2x4 fir and plywood using a table saw, chop saw, and vertical band saw.
