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Nikola Tesla's Colorado Springs Saltwater Capacitors

August 2nd, 1995

PLANS FOR BOTTLE CAPACITOR

Plans for Nikola Tesla's Colorado Springs capacitor bank

Go drink a sixpack of wine coolers. When your buzz wears off wash and clean the bottles out. Scrub off the labels.

Discard the pop-tops and get six screw on white plastic caps from 2-litre Schweppes bottles.

Create a supersaturated solution of Morton salt and water. My solution was 8 tablespoons salt to 6 cups of water. Pour the solution into the bottles filling up to the level where the bottle is no longer cylindrical.

For the remaining airspace, top off the bottles with 10W30 motor oil which will float above the salt solution.

Drill a 1/4 inch hole in the center of each plastic screw cap. Take six 1/4" by 8" long zinc coated carrage bolts, the kind with threads running only about an inch at the end (these are common).

Screw a hex nut onto each bolt as far as it will go. Insert each bolt thread first through the bottom of each plastic cap through the hole you made so that the cap rests on the nut.

Screw another nut onto each bolt down over each plastic cap. There should be about 1/2" of thread left free.

Take these six assemblies and screw one onto each bottle so the head of the bolt sticks down through the oil into the brine. Fit should be tight but seal the cap with RTV anyway.

Now wrap the the cylindrical portion of the outside of each bottle with Aluminum foil allowing the foil the cover the bottom of the bottle. Wrap over this tightly with electrical tape (at least two layers). Don't wrap over the neck of the bottle or the foil on the underside.

Construct a box of 3/4" pine or plywood just big enough to house the six pack and about 6" deep. Paint it flat black and varnish it or use some other insulating coating.

Cover the bottom with a sheet of plate glass and place a sheet of Aluminum,copper,or foil on the glass. Place the bottles in the box. The metal/foil on the glass on the box bottom will contact the foil on the bottle bottoms forming one terminal of the capacitor.

A hole should be drilled through the box near the bottom to bring out the lead away from the top end. Electrically tie the bolt ends (top) of each bottle together with small pieces of heavy gage wire and ring lugs. That is the other terminal.

The beauty of this is the convenience of bottle capacitors yet everything is dry outside. Tuning is as easy as pulling a bottle out or putting another in.

Parts List: (for 1 'sixpack')

6 beer or wine cooler bottles (must have some cylindrical surface area)
6 plastic caps from 2 litre Schweppes bottles
1 quart 10W-30 motor oil
1 box Morton salt
3/4"x6" pine wood
1/4" window glass
1 handfull of ring lugs (for 18AWG or bigger)
Some 18AWG wire or bigger
1 box aluminum foil
6 1/4"x 8" zinc coated carrage bolts (with nuts and stars)
2 rolls electrical tape

Notes:

  • Several boxes may be needed wired in parallel
  • Each box (in my case) was about 4.3nF
  • Each individual bottle in the sixpack should be close to .74 nF
  • You can experiment with other solutions instead of salt water
  • You can try bigger bottles
  • I used un-iodized salt. Iodized salt contains potassium iodide and dextrose which may or may not give the caps more capacitance
  • Tesla used a similar caps in Colorado Springs
  • I made a special box for tuning with the capacitance value of each successive bottle halved (by removing foil/tape with an Xacto knife)
  • I've never had a bottle explode (the deep box will shield you)