I started this project in January this year, having thought about it on-and-off for a couple of years. At the time of entering this project onto Hackaday IO, I've done the following:

• Made a relay from PLA, 3 galvanized iron nails, enamelled copper wire, solder, sellotape, epoxy glue, and connecting wires.
• Wrote a relay testing program for the Raspberry PI. It tests the operation of a relay for a specified number of cycles, and times how long it takes the contacts to open and close. It detects if a contact fails to open or close when expected.
• Established that a clock circuit can be made using (off-the-shelf) relays, and capacitors made from sodium bicarbonate, water and aluminium foil.
• Established that it may be possible to use a sodium bicarbonate capacitor as a snubber to reduce arcing at relay contacts.
• Made some counter circuits using off-the-shelf relays. This includes a circuit that would be capable of controlling a simple 2D plotter, programmed with a punched tape (made from PLA). The file 'controller_explanation.pdf' describes this circuit.
• Made an actuator from the same materials as the relay, used this actuator to step a gravity powered motor.
• Worked out how to get bidirectional linear motion from two unidirectional gravity powered motors.