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A reliable Tesla coil

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4pyros

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I am finally done for the year at the Haunted Attraction I work at.
One thing they would like for next year is a Tesla Coil.
It would have to be outside with a roof over it.
I was thinking of making one but was wondering how reliable it would be in there environment.
Would the humidity and temperatures changes make in necessary to continuously adjust it to get it to work.
Can they run for 6-7 hours a night without problems?
 
Reliability with respect to environmental variability will depend largely upon what you're using for switching, and how large/powerful the Tesla coil is to be. A traditional fixed spark gap would be least reliable. A motorized interrupter-type spark gap would be more reliable. A solid-state interrupter would be most reliable, but they are limited by cost vs. power-handling concerns.
 
I have read that the contacts on a rotary spark gape can burn up fast.
Is there any way to stop this?
 
Hi guys,

Got caught up in something else and just came across this thread :D

I definitely DO NOT recommend building a SSTC just for this event. SSTCs, especially DRSSTCs (which are the most efficient) require a lot of time, research, and practice. You might be able to build a good one within a year, but having the pressure overhead might not make for the best work environment. If you want to build a SSTC, I suggest starting off with building a small one (not for the show) just for fun and to learn the math, but don't plan to have a big one in time for next year.

I think SGTCs are probably your best bet at this point, as they tend to be the simplest and easiest to build. A (synchronous) rotary spark gap would be a great idea, with tungsten terminals (which won't burn out as quickly). How big would you like your Tesla coil to be? That ultimately determines the size of transformer and capacitor bank you'll need. I'd be happy to help you out if you have any questions!

Regards,
Matt
 
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.
 
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.
 
I stopped and "gawked" at one in a hunt near here. Its was not that loud out in the open.
Would love to do music at some point, but think thats all solid state drive.
 
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
 
Matt, can tungsten carbide tool bits be used in the rotary spark gap? Seems to me one of the DIY high frequency add ons for TIG welders used them in the spark gap.
 
Matt, can tungsten carbide tool bits be used in the rotary spark gap? Seems to me one of the DIY high frequency add ons for TIG welders used them in the spark gap.

I don't see any reason why not. The melting temperature is relatively high (5000°F) and the resistivity is low (around 2*10^-7 ohms/meter), so I imagine they would make fairly decent spark gaps. Again, keeping the electrodes cool is the most important thing. The only thing I'm not sure about is their magnetic properties. I imagine they should be fairly good at high frequencies though.
 
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.
But they would look cool!
 
But they would look cool!

Until they break down or explode from overuse :p

They are far less efficient and really are not ideal for medium-size Tesla coils.
 
Until they break down or explode from overuse :p

They are far less efficient and really are not ideal for medium-size Tesla coils.
So I can hide a multiple small capacitor bank, and make a Beer bottle capacitor bank for looks
 
Its also worth noting that you can buy carbide tipped lathe tools, I have quite a few at home for hard steels. You can also buy carbide inserts as well. I only mention this because cutting carbide rod down to size might be problematic.
 
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