The OLTC`s gone pro.

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Finn Hammer <f-h@xxxx>

All,,

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:
http://home5.inet.tele.dk/f-hammer/7.jpg
The toroid is copper, and 6" by 24"
Secondary is 10" by 35" and about 1700 turns.
Fres. 67kHz
A peek into the guts:
http://home5.inet.tele.dk/f-hammer/11.jpg
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...
http://home5.inet.tele.dk/f-hammer/13.jpg
Crouching all down on the floor, I got this shot:

http://home5.inet.tele.dk/f-hammer/14.jpg
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:

http://home5.inet.tele.dk/f-hammer/15.jpg
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.
http://home5.inet.tele.dk/f-hammer/17.jpg

That copper rod is just waiting to protude:
http://home5.inet.tele.dk/f-hammer/19.jpg

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

http://home5.inet.tele.dk/f-hammer/P1010020.jpg
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:
http://home5.inet.tele.dk/f-hammer/16.jpg

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