Small-ish 3D printed SGTC via cheap ZVS flyback build, humbly asking a couple ?s

[davekni]

Disclaimer: I know aesthetically this will not be to everyone's tastes 

Looks really great to me.  Much nicer than any of my projects.

With initial tuning in daylight I'm getting 12" (30cm)+ sparks which I think is not bad for a 120W spark gap tesla coil built by a noob

Yes, I'd say that is good performance.

I'm wondering if the toroid is too small because sparks are coming out of the sides even with a breakout point.

Yes, a larger toroid would most likely improve performance.  Of course, that lowers secondary frequency, so primary needs to be tuned lower to match.

[Michelle_]

Disclaimer: I know aesthetically this will not be to everyone's tastes 

Looks really great to me.  Much nicer than any of my projects.

With initial tuning in daylight I'm getting 12" (30cm)+ sparks which I think is not bad for a 120W spark gap tesla coil built by a noob

Yes, I'd say that is good performance.

I'm wondering if the toroid is too small because sparks are coming out of the sides even with a breakout point.

Yes, a larger toroid would most likely improve performance.  Of course, that lowers secondary frequency, so primary needs to be tuned lower to match.

Thanks for the kind words, I appreciate it. I think you're right that it could use a bigger top load. Also the spark gap could probably be improved, the performance started degrading and then I realized it was corroded and needed cleaning.


I also have tragic news... I think the tesla coil killed both my neon globe and my big xenon globe. I didn't know this was possible but both of them don't react to anything anymore including the slayer exciter, big coil, or plasma toroid prototype that used to work for the big xenon globe. That's too bad because that thing was expensive and the neon globe was probably one of a kind.  :'(

Only slight consolation is the coil works well, here it is shooting a foot long spark into open air, through an argon filled tube that I probably killed.

[Michelle_]

So it's possible to burn holes through borosilicate glass with a tesla coil: PSA be careful

Looks like maximum continuous arc length (pulled to rf ground) is about the same as the secondary (14"/35cm)

Calling this one done! Time to move on to solid state!

[davekni]

So it's possible to burn holes through borosilicate glass with a tesla coil: PSA be careful

Bummer about your xenon tube especially.
I'd guess this is thermal expansion cracking from concentrated local heating.  Even the best glass can't handle extreme temperature gradients.

[alan sailer]

Sorry to hear about the tubes.

If I had known you were subjecting the tubes to sustained arcs I would have warned you. There is a small handheld Oudin coil used
my many to check glass vacuum systems for leaks. The unit is well known for causing leaks as well as finding them.

https://www.electrotechnicproducts.com/bd-10as-high-frequency-generator/?gad_source=1&gclid=CjwKCAjw3NyxBhBmEiwAyofDYS4n6qNpmmftBXQOEAbOPNEhh5q1qmJ9WZ5Jl9oiEe4XiB9tpg1EoRoCtGQQAvD_BwE

I am sure that Strattman could refill your neon as well as the xenon globe. Won't be cheap though.

https://strattman.com/wp-content/uploads/2023/05/Strattman-Design-Wholesale-Price-List-2023.pdf

Cheers.

[Michelle_]

Yeah I didn't know what I was doing obviously, lesson learned. I also killed that argon tube in the pics but at least I got a cool video from it (the pictures are screen shots) and I have a couple more.

Wayne is a good guy he's who I got the xenon globe from (I got the neon one along with my other smaller tubes from a Ukrainian ebayer) - he can refill it which is still cheaper than outright buying another one and less wasteful so that's OK with me. I didn't ask him about the neon one but maybe I should because I liked that little thing lol.

[alan sailer]

dave,

I'm not sure exactly what happens. Obviously the arc is hot and that can do all sorts of damage.

I had a nice (home filled) plasma tube die after brief exposure to a small DRSSTC arc. I am not so good at flame sealing so
I feel that was the main cause. The spark found my badly sealed tubulation and opened a small leak.

I recently had a lovely green plasma globe that had operated for many hours die. Driven by a flyback at about 30kHz and using
capacitive coupling to the tube. The strange part is that the stem of the tube (1/2 inch diameter Pyrex) was wrapped with copper tape.
The tape had a HV wire soldered to it. For some darn reason the spot right under the wire was a hot spot and cracked the pyrex.

You would think a soldered joint to copper tape would distribute the current (and heat) more uniformly, but that is not what happened.

I have littel hope of ressserecting the tube but paln to try...

Cheers.

[davekni]

Alan,

Certainly could be any such possibility.  My only glass glowing experience was in college and shortly after, in other words, decades ago.  Was going mostly on the one image which looks like cracked glass.

[NyaaX_X]

That works fine... I don't know if I make my topload bigger. Can it store more energy and generate a longer and concentrated arc? My arcs only 15cm+ I think...

My plasma globe had been broken by my sstc few months ago. I was guessing the pulse arcs hit it in one point and the transient energy heating and breaking through the glass randomly, whatever. I still have a tube of Neon and another tube of Helium.

[alan sailer]

It's probably obvious but the weak spot on plasma glass is the seal or tip-off point.

Since a plasma globe is generally under a mild vacuum annealing isn't possible. So the tip off point is
an area full of a lot of strain. The point size heating source of a tesla coil arc is enough to heat this area
uneavenly. I'd guess a micro-crack is the result.

Cheers.

[Michelle_]

That works fine... I don't know if I make my topload bigger. Can it store more energy and generate a longer and concentrated arc? My arcs only 15cm+ I think...

My plasma globe had been broken by my sstc few months ago. I was guessing the pulse arcs hit it in one point and the transient energy heating and breaking through the glass randomly, whatever. I still have a tube of Neon and another tube of Helium.

It might be worth trying a bigger top load, yours is running 24v right? I'd check the voltage across the spark gap and see what voltage you're actually getting. I have 12000v across my spark gap, and my system is also fairly optimized I think.

I might try a bigger topload but I'm not too worried about it, althoguh I'm curious if I can actually hit the 18"/45cm sparks the deepfried neon formula claims. I'll need to check in javaTC because I only have around 1.5 more primary turn of adjustment left and increasing the capacitance of my MMC is out of the question because I would need to start running parallel strings.

edit: checked javatc if I change my top load OD from 9" to 11" it should require exactly 1 extra turn to tap which I have, so I'll try it then seeif it makes a difference. I made the topload modular so it just lifts off and mates onto a post which also doubles as the electrical connection. I can print it at 5% infill with gyroid infill pattern at least with PETG so it's not too ridiculous even though it's a huge part.

[Michelle_]

I tried the bigger toroid with re-tuning and got basically the same result. I think I'm being limited by my spark gap and power supply at this point. The worst part is the spark gap, the steel balls are very corroded and even after trying to clean them they degrade quite quickly again which makes the whole thing hard to adjust. There's also a slight... residue in the area inside that seems to have come from the spark gap, kind of a white dusty film sort of thing so that's probably not something that's good. Probably in the future I'll make a new spark gap with multiple contacts like many others have done. I think doing that would make a big difference but ultimately I figure it needs more power to reach the next level, so maybe someday I'll try a heavier duty ZVS and PSU or just a 12KV NST.

[MRMILSTAR]

Streamer length is determined by input power. To make a rugged spark gap use tungsten for the electrodes. A good source is tungsten welding rods.

[Michelle_]

Streamer length is determined by input power. To make a rugged spark gap use tungsten for the electrodes. A good source is tungsten welding rods.

Thanks for the advice I will obtain some tungsten next.