Matt;
I would like to have something big and impressive to have customers walk around a protective cage.
Maybe 4 feet high with 3 foot sparks.
Thinking of leaving the workings visible to impress.
Like the spark gap and a beer bottle cap bank or two in a fish tank.
I don't know how much maintenance a beer bottle cap bank would require. If its sealed would it need refilling?
Where can I get tungsten for the spark gap? Would titanium work?
Thanks for your time.
Beer bottle capacitors really are not reliable, and are generally only used by the occasional hobbyist as a stand-in until some real capacitors arrive. I wouldn't trust them in this case. Also, NEVER seal beer bottle capacitors--If they heat up they can build up a lot of pressure and explode violently. You'd be much better off building a capacitor bank with some Cornell-Dubilier 942C capacitors. They are a favorite among the Tesla coiler community. They have been proven to work at high voltages and high frequencies, and don't fail as easily as some others. They have a very low ESR and ESL, which is very important.
In general I wouldn't recommend running Tesla coils for more than a few minutes (max) at a time. This prevents significant wear and tear and gives them a much longer lifetime.
The melting point of tungsten is twice that of titanium (titanium has a melting point of around 3000°F, whereas tungsten has a melting point of around 6000°F), so tungsten would definitely be the preferred material. On the other hand, it is quite expensive. You can find some on ebay, but the cost is generally fairly high. If titanium is easier for you to acquire, it may be worth trying. Just remember that the temperature of electric arcs can be above 30,000°F, which is why a synchronous rotary spark gap would be a good idea--it would keep the electrodes cool. You would still need to give the Tesla coil a break every couple of minutes though.
Have you been that close to an operating Tesla coil of that size? The spark gap is LOUD!
There are videos on YouTube in which some ingenious folks figured out how to chop the spark gap with an additional external modulation to produce music, thus making the sound and main arc streamers in sync. No amplification is required. It's very impressive -- imagine Zeus as a rock star!
The point being, most people won't want to even get that close to it, let alone stand around and gawk at it, while it's operating.
You are referring to a SSTC ("Solid State Tesla Coil"), which I have already mentioned should not be built as a first TC. SGTCs ("Spark Gap Tesla Coils") are much more rugged and often don't require as much math to get them running. Generally if you don't do the math, the coil simply won't work well, if at all. SSTCs, on the other hand, can have explosive results if you don't do the math. Also, SSTCs (especially DRs) can be even louder than SGTCs, so there really is no benefit to building a SSTC over an SGTC at this point in time. They require a lot more work to design and build, and should not be done under a budget or a deadline.
4pyros , it is important that you offer hearing protection for those who will be near to the coil. You will also need to shield the spark gap, as it can emit harmful UV light.
Regards,
Matt