Thanks Bill! But... heh.... don't look too closely! Angles aren't too precise, dimensions vary, things only line up and fit one way... I'm working with an old small Ryobi bandsaw, a drill press and a T-square and that's about it. And I can't tell you how many times I've screwed something up by trying to make it just that little bit better.

Like that coil form. I should have made 3 rings instead of two and put one in the middle, because the coil wire pulls the "waist" of the thing in until it looks like a dress form or a dice cup or something. I finally broke one of the vertical pieces and had to re-glue it, while re-routing the wiring and adding a turn, after that picture. And I'm still not convinced that the 4 dowels in the corners of the base unit are actually vertical, my glasses distort so much the whole thing looks to me like it's leaning over.

But it's fun building and seeing something come together in reality as I envision it in my mind's eye. It is especially gratifying to me _under the circumstances_ that I designed the coil using a comprehensive Tesla coil calculator based on conventional electromagnetic theory, and the coil works as calculated. The tuning is so very narrow and precise that even the coupling of 0.122, set by the winding heights and spacing, is critical for it to work right. As I clean it up and get the spark gap working better it approaches the predicted performance given by the calculator.

The spark gap is critical, and this gap is now working well. I now set the 5 individual gaps with a 0.020 feeler gauge so that they are all even and all parallel. This gives a total gap of just 0.1 inch and gives great performance in streamer length, less noise in the audio frequency and greater spectral purity in the RF.

Did you notice? I have attracted the lone Drive-By Thumbs-Downer Troll, or another one, and some sock puppets. Of course they are too cowardly to leave any reasons for their droppings, knowing that if they don't have a cogent argument I will ban them at the first sign of trollery or insult. 
I am greatly amused by this activity. In fact I don't think I'm reaching my Target Audience unless little Trolly-poo wakes up one of his sock puppet accounts and leaves a little dropping.

Here's an interesting image.

The exposure was 1/13 second, or 0.0769 sec.
I count 31 individual psarks in that time, in that nice fan portion. This means that the spark gap is firing at a rate of (31/0.0769) Hz... or 403 Hz.

Coincidence?

 

Kamil, Very wise to be safe, I always consider safety first and every part of the primary circuit with MOT's in it is potentially
deadly. When I'm experimenting with anything to do with deadly charge on capacitor or high powers at dangerous voltages
I get myself into a routine where I turn off and disconnect the supply, then discharge all the capacitors and jumper them (shorted)
before even considering touching anything, distractions can be dangerous too.
I have 40 uF on my two MOT's to correct the power factor, which can be left with charge on them sometimes, they get 240 volts.
My primary capacitance is small because less than 20 nF due to my fairly high frequency around 760 kHz, that 20 nF gets charged
to almost double the voltage of the output of the two MOT's in series because I use a DC resonant charging circuit, without that
almost doubling of the 4000 v or so to about 7000 v my spark gap doesn't work so good, I think because of the low capacitance
and energy of the primary capacitor bank.   

Building Tesla coils is kind of a very customized thing for most, people build them for different reasons.

Spark gaps are not a strong point for me as I lack a lot of equipment and live out of town. I had to build a wooden frame rotary
spark gap to get a good output from mine. As I just found out the rotor I made from a plastic cutting board for the spark gap is
cracked now so I'll need to make a new gap of some kind.

Almost impossible to build a "safe" Tesla transformer. It's the operator who needs to be safety minded and careful.
I've got my input power restricted by a coil in series with the MOT's that has a fair bit of resistance, my next play with it
will be to remove or reduce the power restriction and fix my spark gap or build a new one, it could do with a better frame
and rotor.

..

Hi Farmhand,TinsenKoala

Thank you for the advise on capacitance and safety ,
My flyback coils never scare me but MOT is different level but if I want to go bigger/stronger then I need to try it out and see how it goes.
Will start testing ASAP and if I will find questions and problems will come back to you guys ,lucky me that I have some body to ask
The schematic which I think should be appropriate for this build:
 http://isparktube.com/images/phocagallery/Schematics/thumbs/phoca_thumb_l_mot%20tesla%20coil.gif
Let me know what you think about this schematic?
Regards