Scavenging one from an old radio was not an option. Since most of new radios uses analog tuning. And the ones with air variable capacitors are very rare, and are collectors item.
I have read an article once about building an air variable capacitor. So i decided to build my own from scraps of aluminum sheets and from things that are easily found around the house.
If you have a drill, a scissors, a file and some sandpaper. You can easily build this one. It doesn't require much skills.:-)
I made mine from aluminum sheets 1.5 and 2mm thick. The housing is from an aluminum heatsink, i also manage to get 3 pieces of bolts with a few nuts from my junk box. The plastic bushing which also acts as an insulator is from a plastic pen and some plastic jar caps.
I also made my own washers/spacers from the 2mm thick aluminum sheet.
The contacts of the rotor which also acts as a tensioner. Were from a broken washingmachine timer.
You can experiment with the number of plates and with the size op gaps by adding more plates and washer, in the rotor and stator.
Step 1: Marking the center for pilot holes
Lay the aluminum sheet flat on your work bench. From on end draw a square measuring 5cm x 5cm. Using a sharp object like a nail or file.
Get the center and punch a hole in it using a small nail. Punch a hole for every 5 centimeters along the straight line as shown on the photo.