Here is something else I scavenged from the Universal Stereoplotters. A nice z-stage setup for our McWire RepStrap.
In these images we have two full assemblies being shown. On the left is an assembly that is broken into its two components. The smaller shiny piece is the part you attach to the McWire bot while the darker piece above it is the part that gets the Extruder attached to it. To the right is the same setup--I got two--but put together.
An astute observer may ask how this assembly is kept together once in the vertical position? Ah, there is the cool part: MAGNETS! The two round portions in the dark piece with what look like lines through the centers of them are magnets. The other portion is metal so it gets held against the rollers but doesn't end up touching the magnets. Nice little setup that we should consider for the McWire RepStrap.