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Re: propeller gap help (fwd)
---------- Forwarded message ----------
Date: Fri, 20 Jul 2007 20:50:49 -0400
From: Jason Johnson <jasonmsusolar@xxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: propeller gap help (fwd)
I would tend to agree with Scott on this. 1/4" tungsten is probably overkill
in you're application with a 12/60 NST, but would certainly offer good
longevity. You might try some 1/4" brass threaded rod at first, both to
establish a good length for the spinning electrode, and because you might
well be satisfied with its performance.
I use a 9" length of 1/4" brass threaded rod in my propeller style gap, and
it puts up with several hundred milliamps from 2 MOTs. Of course it does
wear some, and you should periodically check your gap spacing (to prevent
overvoltage), but I don't think you would notice much wear on the threaded
rod with a 12/60 powered system. Also, if you want to change to 1/4"
tungsten later - you've already got a 1/4" hole in your arbor. I would go
with as long of a length as you can easily accommodate, to maximize
electrode speed (for good cooling, etc).
Other possible advantages - brass threaded rod is available in 12" lengths
for approx. $2 @ Home Depot; it needs no special locking collars or
setscrews, just locknuts; it also makes good stationaries; better electrical
conductivity than tungsten (though this is probably not super significant);
also the threads increase surface area, and thus act like little cooling
fins, though I'm not sure if this last point outweighs the superior melting
point of tungsten.
On 7/20/07, Tesla list <tesla@xxxxxxxxxx> wrote:
> ---------- Forwarded message ----------
> Date: Fri, 20 Jul 2007 16:12:27 -0400
> From: Scott Bogard <teslas-intern@xxxxxxxxxxx>
> To: tesla@xxxxxxxxxx
> Subject: RE: propeller gap help (fwd)
> That depends on what you want you electrode speed to be. My advice
> you would be to use thinner (cheaper) tungsten. A 12/60 NST is only 720
> watts, and only requires a cap between 13-25 nf (depending on secondary
> and other factors). I think 1/4 inch is a bit overkill, I use 1/8-in at
> twice the power (which is just a bit slim, but it seems to work fine).
> Anyway, 7 inches (which is the standard tungsten electrode size) gives
> over 37 MPH, and seems to work for most of us using propeller gaps, just
> fine. Good luck.
> Scott Bogard.
> >From: "Tesla list" <tesla@xxxxxxxxxx>
> >To: tesla@xxxxxxxxxx
> >Subject: propeller gap help (fwd)
> >Date: Fri, 20 Jul 2007 11:43:11 -0600 (MDT)
> >---------- Forwarded message ----------
> >Date: Fri, 20 Jul 2007 11:50:51 -0500
> >From: Shaun Epp <scepp@xxxxxxx>
> >To: tesla@xxxxxxxxxx
> >Subject: propeller gap help
> >I recently aquired a small sychronous motor, 1800RPM oriental motor. I
> >to use it with my 12 Kv, 60 mA NST. How long should the propeller rod be
> >I'm going to use 1/4" tungsten rod. I've seem a guy on ebay selling it
> >the inch.
> >Shaun Epp