splitting a 3"x1" ceramic insulator in half down the middle

[Opcom]

This happened at the Teslathon this weekend.

The arc from the large coil hit the insulator carrying the 13500V low voltage input, and split it right in two.
http://www.bunkerofdoom.com/teslathon2010/hog/100_9431.avi

Pics of the whole event are here in case anyone wants a high voltage fix:
http://www.bunkerofdoom.com/teslathon2010/index.html

I talked to the guys about operating a TC driven by a mediun wave transmitter. They say it can be done and for example a low frequency like 1400KC should not pose an issue if the design is done right. Smart guys there at that event.

[WBear2GCR]

Smart guys?

You couldn't get me to touch anything in the primary without a good shorting stick permanently connected first...

And what the heck is that blue thing on top of the coil??

I have seen a small Tesla Coil run by a single 833... surprisingly small spark, but neat... made by W2FFC locally...

fun stuff, if you are careful... or why you should not be able to arc the discharge back into the primary...

Just my 2 cents - feel free to disregard.



                _-_-bear

[W2PFY]

I'm not trying to be  Pest Toe Mist here but how many people get killed in a year with those HV Tesla & coin shrinking machines?

[John K5PRO]

I, too, was surprised at how readily those TCers walked over and grabbed the 13 kV circuit after it had just been running. Do they have any sort of
lock on the AC primary disconnect first, to make sure no one presses the button and energizes it? I would never trust relays or plain switches to prevent electrocution, as what if Murphy just decided to act out at the wrong instant?

Neat stuff, nice arcs. What was reason for intermittent operation, heating, arcing over?

[Opcom]

There is a guy at the variac & contactor and turns the pole pig off. He is in sight of the guys adjusting the beast and stays there to see that it was not turned back on. The rotary gap is left running even though there is no sparking.

The intermittent operation is because they were tuning it, moving the primary tap around on the lower coil as well as changing the size of the stationary gap in series with the rotary gap.

The operation my seem more intermittent than it is, but that is because only the big arcs that find 'ground' show up well on video. There are discharges that reach out 6-7 FT that are not very bright.
The rotary gap also plays a role as the phase of the gap rotation does not always coincide with maximum charge on the capacitor bank over the half cycle. The RPM of the gap electrodes has quite an effect on the timing.

The blue thing on the top is the "top load" and its purpose is to be the place for arcs to come from as well as to set up a gradient that discourages arcs from coming off the secondary winding and burning it.

The outer turn on the primary is divorced from the primary and is a grounded shield ring. That is where the arc should hit if it decided to come downward, but it was sort of doing what it wanted. It seemed to like the ground shield over the rotary spark gap a lot.

About the coin shrinking, they seemed to know what they were doing but I do not and I would not sit so close to a 33KJ cap bank charged to 20-30KV if it were an open lash-up.

No one got killed at this one. By gross appearances they do not seem to take the same kind of precautions we take with transmitters etc., but they do take different-looking precautions which are not very evident to casual observation. I believe they discharged everything each time. I was watching because I was walking around there. The T-coils have the capacitor connected across the transformer so it is discharged in the secondary when the power is turned off. The shrinker bank was discharged and strapped after each shot.

[W2PFY]

There are three things I won't play with now. # 1 is X-rays. Some do it as a hobby, Two, High powered lasers and now those pole pig powered Tesla machines. It's not that I disapprove, I'm just scared of what could happen to me or some other innocent person.

[WBear2GCR]

Well, I think these guys are playing with death... given the set up.

But, what do I know?

My old friend Frank T had a Tesla coil in his apartment in 1971... he probably had it before that. After the apartment he bought a big rambling victorian house in Mt. Vernon NY, he had it in a basement room...

The coil was maybe 8" diameter, about 4-5ft tall.
Rotary spark gap.
Several neon sign transformers ran it.
Bank of earl filt capazators...

7-8' discharges. No problem.

Nothing quite like bringing a nice young lady into the basement, sitting her down in the chair in the corner, winding up the spark gap (ran off a vacuum cleaner motor ~10,000 rpm), and then dumping in the primary power. BAAAAAPP !!!

Frank would grab a 4 ft fluorescent tube and hold it up to the discharge...

The reaction, was, ummmm... "mixed".

Guys seemed to like it fine.

                    _-_-bear

[W5COA]

So when and where is this North Texas Tesla get together held?

I built a TC in high school, and the teachers were so scared of it, they put me in a separate room from the other science fair projects.

That was 50+ years ago, and I would like to attend a modern event.

Jim (who lives in North Texas)

[Opcom]

It will be a year till the next one, I guess.. Here is the mailing list information:
>> > _______________________________________________
>> > Tesla mailing list
>> > Tesla@pupman.com
>> > http://www.pupman.com/mailman/listinfo/tesla