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Re: SRSG gap spacing?

Original poster: "Dave Leddon by way of Terry Fritz <twftesla-at-qwest-dot-net>" <leddon-at-attbi-dot-com>

Probably the best justification for the tightest possible gap spacing is
the ability to run the coil at lower voltages but all of the other reasons
given make the same assumption,  namely that the arc forms when the
electrodes are at their closest proximity.  It has been my observation that
the arc initiates well before this.  I can measure this spark advance on an
oscilloscope by comparing two signals, one generated by a magnetic pickup
coil and a pair of magnets mounted on the SRSG disk on the electrode
radius, and the second from a plane antenna (thanks Terry) which measures
the field generated by the secondary ring-down.

This spark advance increases as I increase the input voltage reaching a
maximum advance of about 400 microseconds at 100% input voltage.  This time
interval on my SRSG (3 inch electrode radius at 3600 rpm) equates to 0.45
inches of travel.  Further, the ring-down quenches in the second notch at
60 microseconds, when the voltage is high enough for streamers to form, and
in the first notch at 30 microseconds when strikes occur. So it's pretty
much all over well before the electrodes reach complete alignment.  Has
anyone else made this observation?


At 07:50 AM 5/27/02 -0600, you wrote:
>Original poster: "Steve White by way of Terry Fritz <twftesla-at-qwest-dot-net>"
>Hello Dave,
>Two advantages come to mind in having a narrow gap spacing. The first is
>power control. If you control the voltage to the primary with a variac, you
>can operate the coil at lower voltages if the need arises. The lowest
>voltage limit will be established by the minimum gap that you can maintain
>which will fire. The second reason is that with a SRSG with 4 flying
>electrodes, such as mine, there are a total of 4 gaps to fire simultaneously
>to complete the circuit. When you multiply the single gap spacing by 4, you
>will find that you actually need quite a small gap spacing to keep the 4
>combined gaps at a reasonable spacing.
>Steve: Coiling in Iowa
>----- Original Message -----
>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: <tesla-at-pupman-dot-com>
>Sent: Sunday, May 26, 2002 7:57 PM
>Subject: SRSG gap spacing?
>> Original poster: "Dave Leddon by way of Terry Fritz <twftesla-at-qwest-dot-net>"
>> What is the rational behind maintaining a narrow gap spacing on a SRSG?
>> I've seen this recommendation so often in this list that it begins to take
>> on the dimension of dogma.  On my coil, as the electrodes wear down and
>> gap spacing approaches 1/8 inch, the performance actually seems to
>>  In theory a wider gap should reduce the arc dwell time.  So what are the
>> advantages?
>> Dave