The capacitor is easy to make, especially if you just want to duplicate my capacitor by printing the provided STL file. The instructions have an introduction that provides enough information to design your own fixed or variable capacitor, should you need a different capacitance range. If you have any questions about designing your own version of the capacitor, feel free to contact me. 

Since the instructions are so simple, I went ahead and wrote up my design for a motor with rack-and-pinion to move the capacitor. 

Since that was so simple, I went ahead and introduced my Arduino controller for the motor.  The motor controller is a work in progress.