This is somewhat like a simple spark gap. However, the safety
gap has 3 electrodes. The one in between the two others is
connected to a good ground. This conducts any power surges to the
ground, which would otherwise overload and destroy the main power
transformer. These power surges originate from the capacitors,
and can result from bad tuning.
For this section, you will need the following items:
1. A 5-inch section of wood that is 1 inch wide, and 1/4" thick.
2. 3 machine screws. They must be 1/8" wide, and 1" long. One of the screws should be without a head. If such an item is not available for sale, you will need to cut the head off. You can do this either with a Dremel and a cutoff wheel, or a hacksaw.
3. 4 screw-on end caps that will fit onto the bolts.
4. A 1/8" wide drill bit.
5. 2 ring connectors. They will have to be able to fit over the 1/8" bolts, as well as accept 8 gauge wire.
Cut the 5-inch section of wood into 3 sections that measure 1" by 1". The extra wood is extra to fall back on in the event of a mistake. Drill a hole in the center of each piece.
Thread one bolt per section through two of the sections of wood. Put the headless bolt through the remaining section of wood. An equal length of the bolt should be visible on either side of this last section.
I put epoxy on the middle bolt to hold it in place. You can also put epoxy on the inner hex nuts on the other two bolts. This will help prevent the wood from stipping out.
Put one ring connector on each of the three bolts. The two bolts with heads will be connected to the rest of the main circuit. The headless bolt will be connected to the Tesla Coil's ground. The gap between the electrodes should be less than 1/4".
This is what the finished safety gap should look like.
You can also see some chokes in the backgound. They protect the transformer from power feedback surges.
Cost of the Safety Gap
1. You can get the wood just about anywhere. I used a small piece of scrap wood.
2. I got a small bag of matching nuts and bolts at Lowe's. It was $0.78.
3. The bag of 4 end caps cost $0.78.
4. A pack of 6 ring connectors costs $0.69 at Sears Hardware.
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