Re: [TCML] Propeller-Style SRSG eats Tungsten Rods @ 10kVA

[Gary Lau <glau1024@xxxxxxxxx>]

Wow - I think the hardware alone used to hold together the Lexan enclosure,
weighs more than my entire coil.  Well, maybe not, but I'd sure hate to
notice something inside the enclosure that needed fixing after I just
buttoned it up!

I wonder what the thinking is on the 13M propeller blade design?  The nice
thing about the propeller design as popularized by Terry Blake is that the
blade itself couldn't be simpler.  But the "blade" on the 13M seems to be a
very specialized, purpose-build assembly, and not as aerodynamic as I would
have guessed.

I like the 13M's attempt to create a line on the electrodes, rather than a
point, where the arc occurs.  I would guess that this would improve
quenching as well as reduce electrode erosion.  Before I achieved success
with my propeller gap, I attempted to build a SRSG using a Lexan disk with
two 3/4" copper pipe segments as rotating electrodes.  The pipes stuck out
about 1.5" from either side of the disk, and I had two stationary electrode
pipes that arced to the two sides of the rotating pipes - kind of a rotary
cylinder gap where the arcing was to occur in a line along the sides of the
pipes.  Unfortunately I had only the Teletype motor, and the Lexan disk and
pipes were too massive to spin up for my small motor.

Has anyone ever build a rotary gap, with tungsten rods inserted midway
through a disk, but with the stationary electrodes arcing to the *sides* of
the rotating electrodes?  While this places a greater importance on the
precision of the radial placement of the disk electrodes, I think this would
be a win-win in terms of quenching and electrode erosion.  I wonder if the
arcing would occur randomly along the length of the rods as it does on
cylinder gaps, or if a temperature gradient along the length of the rods
might bias the arcing towards the warmer free ends?

Regards, Gary Lau
MA, USA


On Fri, Oct 15, 2010 at 9:10 AM, David Rieben <drieben@xxxxxxxxxxx> wrote:

> Hi Scott, all,
>
> Here's a pretty good shot of the 13M "propeller gap":
> http://www.teslauniverse.com/photos/wysock-13m#id=album-17&num=content-620
>
> David
>
>
>
>
> ----- Original Message ----- From: "Scott Bogard" <sdbogard@xxxxxxxxx>
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Sent: Thursday, October 14, 2010 6:17 PM
> Subject: Re: [TCML] Propeller-Style SRSG eats Tungsten Rods @ 10kVA
>
>
>  Gary is absolutely correct, I would like to point out that Bill Wysocks
>> 13M coil ( a true monster if ever there was one) uses a propeller gap of
>> sorts.  I can't find the link to the page that details of it but you can see
>> here from the back of the gray spark gap the tip of the propeller in an
>> acrylic box.
>> http://www.teslauniverse.com/photos/wysock-13m#id=album-17&num=content-622
>> The only difference between this and the ones us amateurs make is the
>> surface area of the point of contact, there is nothing stopping someone from
>> making an arbor capable of holding several tungsten rods in parallel and
>> electrically binding them together so dwell time is tiny but conducting area
>> is huge.  It might be difficult to machine but it would perform superbly,
>> and still be lighter than a disk.  I'm going to say it, carefully built
>> propellers are better in every way, I think there is room for improvement in
>> the design of the "prop," making something special instead of just a rod in
>> some PE, to correct issues like electrode spacing and as argued current
>> handling capability, but I doubt I'll ever build a disk type.  Just putting
>> this out there.
>>
>> Scott Bogard.
>>
>>  I'm not sure it's fair or useful to suggest that a propeller gap isn't up
>>> to
>>> the task of a 10KW or whatever, coil.  I don't see how a disk holding
>>> short
>>> tungsten segments is inherently more capable than a propeller geometry. I
>>> think what matters is only the diameter of the tungsten rods.  If the
>>> same
>>> diameter tungsten were used in a propeller gap, wouldn't it be equally
>>> capable as a disk-based geometry?  I was going to suggest that maybe
>>> propeller gaps are limited because long welding rods don't normally come
>>> over 1/4" diameter, but just noticed that McMaster-Carr has lengths up to
>>> 12" and diameters up to 2".  Wowza!
>>>
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>>
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