Inspiration can strike at any time, and after seeing a bicycle chain lying in a random orientation on the street, Ekaggrat Singh Kalsi decided to create the GETULA numerical display, based on movable linkages. The idea is that the chain, when properly bent, can show useful numbers on command.
His modular morphing clock uses two stepper motors and sprockets to advance a pair of custom chains for each digit. As each comes out of an opening, a pair of servo motors pushes the links left or right, bending the numbers into place as they appear. Custom 3D-printed linkages are used to allow them to stay rigid as they move upwards.
The system is controlled by an Arduino, along with a pair of A4988 stepper drivers for each module. Steppers are the common 24BYJ48 devices, and 9G servos are used to curve the chains. As of now, only one dual-linkage digit is automated, but the plan is to get all four working in the future.
Even though only one digit currently moves, it’s still quite an impressive feat of engineering. A demo of the system can be seen in the first video below, and it's put to use showing the year changing from 2020 to 2021 in the second – proof that you can display something useful with only one digit change!