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Re: The OLTC`s gone pro.

Original poster: "K. C. Herrick" <kchdlh@xxxxxxx>

That's beautiful work, Finn; I'm envious!  Congratulations.

It's interesting about the breakouts: When I had my super-complex s.s. coil running, I found I didn't require a breakout at all (with the smooth 6" x 24" toroid). I got very nice 2 1/2 ft. sparks that danced all around the toroid. If you recall, I posted a photo of it with Terry. 2 1/2' ft. didn't satisfy me, I tried to improve it but made it worse & endlessly failing, & finally ran out of motivation...so it no longer runs.

Do you need the breakouts, or are they just for the directing of the sparks?

Ken Herrick
Oakland, CA USA

Tesla list wrote:
Original poster: Finn Hammer <mailto:f-h@xxxx><f-h@xxxx>


The OLTC (yes, I cave in and submit to tradition rather than formal correctness) that I`ve been building has just passed the Factory Acceptance Test (FAT) so I dare to share the construction details with you all.
This coil is based heavily on the work of Stephen Connor, and without his cooperation, and continuing contribution, it would not have been built.

It looks like this:

The toroid is copper, and 6" by 24"
Secondary is 10" by 35" and about 1700 turns.
Fres. 67kHz
A peek into the guts:

reveals a steel pipe skeleton with the 3/16" allu plate covers attached. Some touch up paint work to do on the bottom of the secondary.... The box in the bottom contains the gate driver, and a rather clever trigger generator. The coil is only designed to give out short bursts og streamers and arcs (48" long). The customer didn`t like the tone of a coil running at a steady breakrate, like a sync rotary gapper.. By the time that the order was received, I knew (thanks to Marco Denicolai) that a streamer is fully developed after 14 breaks. I figured those 14 streamers would sound like a "bang". At the Derby Teslathon Stephen had a trigger generator that could deliver triggers in sequence, and we were all flabbergasted to experience that up to 3 breaks, the coil would say "bang", but with more than 4 breaks it would say "beep". The ear-brain interface is a wonderfull thing. Stephen made a special trigger generator that randomized the firing sequence around a predetermined breakrate, not unlike a static gap, and the sound is similar. To each his own, but I prefer the sound of a sync. gapper.
Here is another view, I guess you are starting to wonder what those blue pipes are...

Crouching all down on the floor, I got this shot:


As has become tradition with my coils, the primary is tucked nicely away inside the secondary. It is a "why not" desition, and it opens up to some interesting visual design possibilities, although I didn`t exploit them to the limit in this particular coil.
Those blue pipes that take off from the base of the coil and up into the secondary actually make it all the way to the top of the coil:


They are custom made bowden cables, made from pneumatic polyurethane pipe and nylon fishing line. terminated in pneumatic fittings and brackets made for the job.
Crimped to the nylon fishing line is a piece of cobber rod, which is guided to the perimeter of the toroid by soldered in copper tube.

That copper rod is just waiting to protude:

And it does so, when one of the solonoid magnets, with associated pull back spring:


down in the base tells it to.
The coil will be installed in a circular 10`dia. faraday cage, and is designed to be able to fire either a streamer or an arc, in 6 different directions within the 2 front quadrants, and this is accomplished like this:
The appropriate discharge point is extended, and for a streamer a train of 12-15 breaks is fired, whereas for a connecting arc, a train of 18-22 breaks is fired.

If you are a strong beleiver in the importance of sealing the ends of your secondary, and perhaps adding a couple of baffels at intermediate positions, you should take a look at this pic:

That`s the IGBT`s you see down at the other end of the pipe.
For this installation, there is also going to be 2 barrels with twin coils in each, I`l get back to you with pictures and descriptions when they are finished.

I`ve been on this list for quite some years, now, and would like to express my feelings of the deepest gratitude to all, none mentioned none forgotten, who have helped and inspired me to get to this point, where I am now lining up among the professionals. But keep in mind, a pro is not necessacarily a great coil constructor. We can all build coils. But can you sell a coil, can you build a coil that you will part with with pride, and can you attract and negotiate that contract, that is of importance.
As such, I feel more like the crack salesman then the pro coiler.

Cheers, Finn Hammer