A Scotch yoke mechanism for an automatic drawing machine

The brief was purely mechanical: convert circular motor movement into the linear motion needed to lift and lower a pen on a drawing machine. Working in teams of four split into pairs, each of us developed a mechanism individually before testing it physically — I chose to pursue a Scotch yoke over more conventional cam-and-follower designs after 2D block testing confirmed the motion would work.

The first physical prototype failed under testing — glued slider supports were disrupting the movement — so my partner and I rebuilt it with bolted supports instead, and closed the gap between motor and slider to stop the spline slipping off. Scored against a second team's design on repeatability, reliability and rigidity, our Scotch yoke mechanism came out on top and was taken forward for the full drawing machine.

Machining the parts myself — on the mill and lathe — meant every tolerance issue in the design showed up directly in my own hands, which shaped how I iterated the slider and mount well beyond what the CAD model alone would have told me.