Sliding variable capacitor

***UPDATED Frame V2. The original didn't have enough space for the geared plate holder to slide effectively after removing the supports. This now works properly. Haven't installed the plates themselves for testing of the capacitance yet.***

A variable capacitor designed to be approximately 10-120pF. I have not printed this yet, so it's all mathematical at this point. It is designed to use two 40mmx80mm pieces of aluminum flashing for the plates. I haven't had a chance to draw up the electrical connnections, but the frame plate needs a tab 3mm wide extending from one corner, while the wedge needs a 3mm wide piece brought trough the hole and folded over to act as a contact for the geared plate. The wedge should provide enough tension to keep the tab in contact with that plate as the gear moves the plate back and forth. I haven't decided on end stops yet, but this should be alright with care, the wedge should also provide some retention ability.

I calculated the capacitance based on