Re: [TCML] rotary gap disk

["Phillip Slawinski" <pslawinski@xxxxxxxxx>]

On Sun, Nov 30, 2008 at 14:34, Jeff W. Parisse <workshop@xxxxxxxxxxxxx>wrote:

> Phillip,
>
> The gap spacing on our SG10-TC is amazingly small; business card width or
> less (our techs use automotive feeler gauges to set the spacing, I don't
> know the actual number but it is wicked tight).


What I meant is that I think the flying electrodes were too close together
on the disc.  My design had all the flying electrodes connected together by
a ring, and the two stationary electrodes were in front of the disc 180
degrees apart.  The flying electrodes were about 1.25" apart center to
center.


>
>
> Given that, I believe it is/was the brass vaporizing causing holdover that
> is the main issue with homemade gaps of this type. Suggesting to Jay that he
> spin faster may be a bad suggestion given the squared increase in potential
> energy he must now deal with safely.


Indeed, I ran the gap without a capacitor and there was a green glow where
the arc started at the electrodes.  The plasma plume stretched about a
quarter of the way around the disc.  The vaporization of the brass coupled
with the insufficient spacing between flying electrodes led to very poor
performance from the gap.


>
>
> Whatever the design that Jay adopts, I believe the 1/4" Lexan shattersheild
> is great advice for all non-machinists to follow. My plastics shop (Plastics
> Depot in So. Cal.) has a 3/4" sheet of Lexan with all sorts of bullet damage
> from several weapons (38cal handguns up to Mk-11 and M16 rifles). It is
> simply amazing what this material will withstand in terms of impact
> strength.
>
> Jeff
>
>
> ----- Original Message ----- From: "Phillip Slawinski" <
> pslawinski@xxxxxxxxx>
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Sent: Sunday, November 30, 2008 7:43 AM
> Subject: Re: [TCML] rotary gap disk
>
>
>
>  I've only built one rotary gap.  The one I built was sort of hacked
>> together.  I made a 5" disc out of a cutting board, and press fitted it on
>> a
>> fractional horsepower fan motor.  The motor speed was about 1650 rpm, and
>> I
>> had eight flying and two stationary electrodes.  I used 1/4" brass screws
>> with acorn nuts on the end.  While I don't remember having any trouble
>> with
>> the flying electrodes getting hot (all the way up to 2400W) the stationary
>> electrodes became smoking hot after about 40 seconds of run time.  I used
>> a
>> blower to keep them cool, but I never could get the gap to perform well.
>> It
>> could have been that the brass vaporized too easily, or it could have been
>> that the spacing between flying electrodes was insufficient.  The bottom
>> line is that the gap was awful.  I would be more apt to use proven designs
>> at this point instead of trying to do it the cheap way.
>>
>> On Sun, Nov 30, 2008 at 09:03, <jhowson4@xxxxxxxxxxx> wrote:
>>
>>  so i found a really good deal on lexan.  17$ for a 1/2" thick 12" by 12"
>>> couldn't find any G10 for cheap so i am going with lexan.  do you guys
>>> think that the 1/2" thickness is good. I am planning on spinning a 6.5
>>> inch
>>> diameter disk with up to 8 threaded rod and brass cap electrodes.
>>> I have a 1/3 HP  motor that I am going to modify for sync operation.
>>>
>>> what do you guys think?
>>>
>>> Jay Howson
>>> _______________________________________________
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>>>
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>>
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