[Home][2018 Index] Re: [TCML] Re Please review my coil plan [Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [TCML] Re Please review my coil plan

Hi Bert,

So I guess it was not my imagination that the additional quenching gained by an extra pair of stationary gaps in my big coil did not help increase the output at all and if anything, it may have actually diminished the output a bit. With the losses of additional gaps in series causing significant extra voltage drop (100-200 volts/gap would make for quite a significant loss of power when there is typically several hundred or even a thousands of peak amps, and several amps RMS in the primary circuits of larger systems), "overquenching" does appear to be an actual source of losses to be reckoned with. Makes me even question the wisdom of the RQ style mulitple gap for NST sized systems now?

Happy July 4th to US coilers,

----- Original Message ----- From: "Bert Hickman" <bert@xxxxxxxxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Tuesday, July 03, 2018 9:14 AM
Subject: Re: [TCML] Re Please review my coil plan

Excellent points, Steve.

Doubling the number of gaps also doubles spark gap losses in the system. Each gap introduces a voltage drop of between 100-200 volts in the primary circuit. This applies to both static and rotating gaps.


Steve White wrote:

There are a couple of potential problems with using double stationary electrodes (4 gaps to fire simultaneously instead of 2) if I am understanding you correctly.

The main problem with 4 gaps is that you have to get the gap spacing twice as close as with 2 gaps for the same firing voltage. I made my SRSG with the ability to use either 2 or 4 stationary gaps. When I tried it with 4 gaps, I found it very difficult to get consistent firing even though I am using a 14.4 KV pole pig. I eventually went to 2 gaps and get good consistent firing. The usual reason for using 4 stationary gaps instead of 2 is to decrease the quenching time however, given the diameter of the large tungsten electrodes which would be used for a high-power coil, the impact of this is negligible. I would just stay with 2 stationary gaps. You can try it with your stationary electrodes and see if the erosion is acceptable. If not, you can make the auxiliary heat sinks with ceramic heat shields for the stationary electrodes as I described earlier. I don't have any problem with flying electrode erosion with a rotor speed of 3600 RPM due to the excellent air flow. If your
rotor speed is high enough, I don't think you will have a problem with flying electrode erosion. Since you are contemplating a ARSG you will have to experiment with the speed.

Another potential problem with having 4 stationary gaps is uneven electrode erosion. If the stationary electrodes wear unevenly, then this make it even harder maintain a very small gap spacing. This uneven wear also becomes a problem as you increase the number of flying electrodes if they wear unevenly. If the wear is uneven, the electrodes can collide if you try to adjust some electrodes to compensate.

One thing to remember is that the more flying electrodes that you have, the harder it will be to achieve precise electrode hole placement and to balance the rotor. As you probably know, the rotor with the flying electrodes needs to be made to a very high level of precision and balanced very precisely or else it will shake your coil apart or worse. I see from your transformer picture that you have a lathe. That will help a lot. With a lot of careful thought, I was able to make my rotor with just a bandsaw, a drill press, and a rotary die grinder. At the time, I didn't have a lathe or a milling machine, which I now have.

The conclusion, as I see it, is to use as few stationary and flying electrodes as possible. This minimizes the uneven erosion problem and makes your gap maintenance easier.

The G10 (FR4) rotor material that you are contemplating is perfect.


----- Original Message -----
From: "Jan Ohlsson" <jan@xxxxxxxx>
To: tesla@xxxxxxxxxx
Sent: Monday, July 2, 2018 8:04:10 AM
Subject: [TCML] Re Please review my coil plan

Hi Kurt,
Your big coil is really impressive and it was not my intention to be
disrespectful to a pioneer like mr Burnett. A calculation method that makes
it possible to establish a good balance between BPS, ballast inductor and
capacitor is of course of great value, regardless of if the charging system
really is resonant in the true sense or not.

And thanks David,
You and others have certainly convinced me of the importance of varnish...
Yes, the bomb shelter is a great place, but I will be dependent on a
counterpoise type ground, and I have gotten the impression that this concept
is not that much tested for tesla use.

I was planning on an epoxy/fiberglass disk for the rotary, slightly larger in diameter (40 cm), in the hope that this would cool the electrodes better.
But from ypur experiences with your high powered coil, I realize that
electrode erosion might be a bigger problem then I expected. I will try to achieve as much cooling as possible for the stationary electrodes, and will
try to locate larger diameter rods. Perhaps double sets of stationary
electrodes would also share the load and keep up better?

All assuming that I first succeed with the transformer and ballast, of

Kind regards,

Tesla mailing list
Tesla mailing list

Tesla mailing list

Tesla mailing list