Sliding variable capacitor

thingiverse

***UPDATED Frame V2. The original didn't provide sufficient space for the geared plate holder to slide smoothly after removing the supports. This updated version works properly now. I still need to install the plates themselves for testing of the capacitance yet.*** A variable capacitor designed to approximate 10-120pF in value. At this point, it's purely mathematical as I haven't printed it yet. It's intended to utilize two 40mmx80mm pieces of aluminum flashing for the plates. I need to draw up the electrical connections, but the frame plate requires a tab 3mm wide extending from one corner, while the wedge needs a 3mm wide piece brought through the hole and folded over to act as a contact for the geared plate. The wedge should provide sufficient tension to keep the tab in contact with that plate as the gear moves it back and forth. I haven't decided on end stops yet, but this setup should be fine with care, the wedge will also offer some retention ability. I calculated the capacitance based on a dielectric constant of 2.55, which is roughly what I've found for PLA, so it should be in the ballpark of 2.5 to 3. Again, I haven't built it yet, so these values are purely mathematical. The shaft is 5mm, but could be adjusted to anything really, and if you're printing this, designing a knob should be relatively easy enough.