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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,
David
----- 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. 
Bert

Steve White wrote:

Jan,
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.

Steve

----- 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
course...

Kind regards,
Jan



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