David, all,
I agree, I've found the RQ style multiple gaps to give somewhat
poor performance compared to a Gary Lau style single
sucker or vortex or pressure gap (pressure is probably
best). A single gap, provided it is kept cool enough
seems to be best because of reduced voltage drop
as Bert mentioned.
For rotaries I think the same thing is true, fewer gaps
are better, provided they don't power-arc or re-fire
while the electrodes are still aligned. Increasing
the number of gaps doesn't help the quenching
very much since the quenching is mostly a result
of the energy being quickly burnt up in strong output
spark production.
For static gaps, much of what some folks refer to
as poor quenching is really due to gaps that are running
too hot and therefore fire at an abnormally low voltage.
Happy July 4th !
John
-----Original Message-----
From: David Rieben <drieben@xxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Wed, Jul 4, 2018 8:09 pm
Subject: 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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>>
>
>
>
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