High Voltage Forum

Tesla coils => Spark Gap Tesla Coils (SGTC) => Topic started by: Patric on September 01, 2018, 11:04:19 PM

Title: Non toroid top loads
Post by: Patric on September 01, 2018, 11:04:19 PM: Guys,

like to discuss some more unusual top load configurations.
Our local gardening center is selling stainless steal deco spheres at a bargain. Even stacking up with a dozen or so is still very affordable. So why not build something like this:

How would something like this perform?

There are no discontinuities, would this produce an even field with sufficient surface area / capacitance?

Overlapping spheres would also be an options. Some angle grinding, spot welding, job done.
Although I find those separate sphere more appealing.

Cheers Patric
Title: Re: Non toroid top loads
Post by: Mads Barnkob on September 02, 2018, 05:10:40 PM: I have seen a Tesla coil that used 8 spheres set out in a circle as topload, but I can not find a picture or link to it right now. I tried to search all kind of sphere topload sentences, but no luck.

Sphere would have to be close enough to almost touch to be effective, one of the downsides of using a single sphere as topload is its weak field shaping downwards to the secondary coil and thus flashovers or uncontrolled sparks becomes a problem.
Title: Re: Non toroid top loads
Post by: Uspring on September 03, 2018, 01:52:29 PM: Both touching or overlapping spheres should work nicely. When considering intersecting surfaces, you usually have sharp edges somewhere, which could be a problem. But as long, as they point inward into the field free region of your structure, they don't matter.
Title: Re: Non toroid top loads
Post by: Max on September 05, 2018, 11:52:36 AM: As far as I know, there’re two coils using such toploads. One of them is mine, and I got the idea from this coil: https://forum.mosfetkiller.de/viewtopic.php?f=32&t=62483&start=5 (https://forum.mosfetkiller.de/viewtopic.php?f=32&t=62483&start=5)

@Mads: you commented one of my videos of the coil; so chances are, it was mine you remember ;) btw. I always wondered how you found that video...

I used 9 spheres with a diameter of 25cm. The resulting "toroid" is 1m outer diameter. Pics can be found here: https://forum.mosfetkiller.de/viewtopic.php?f=32&t=62896&start=253 (https://forum.mosfetkiller.de/viewtopic.php?f=32&t=62896&start=253)
The coil in action (scroll down): https://forum.mosfetkiller.de/viewtopic.php?f=32&t=62896&start=315 (https://forum.mosfetkiller.de/viewtopic.php?f=32&t=62896&start=315)

In my opinion there’re no perfomance problems with this type of toroid. I easily got 2,5m arcs (secondary: 20cm x 1m, 0.6mm wire) - and didn’t even tune it. In the next weeks I’ll try to get longer arcs by tuning the coil properly and using pulse-skipping.

If anyone’s interested, I could explain more in detail how the topload was put together.

Kind regards,
Max
Title: Re: Non toroid top loads
Post by: Mads Barnkob on September 05, 2018, 01:42:16 PM: Thank you very much Max, I have been looking all the wrong places to find it, I have scrolled 2 years back in the Coilsmith group on facebook, I was so sure it was there I saw it.

I am subscribed to your channel, I think I once did a search for DRSSTC/Tesla coils and just subscribed to everyone that had interesting looking coils on their videos :)

Here is the video for everyone to see!
Title: Re: Non toroid top loads
Post by: Patric on September 05, 2018, 08:41:36 PM: Thanks for the confirmation, I shall make my top load from spheres then!
Cheers Patric