Re: propeller gap help (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Sat, 21 Jul 2007 11:45:18 -0400
From: Scott Bogard <teslas-intern@xxxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: Re: propeller gap help (fwd)

Jason,
     Brass does not conduct better than tungsten (sorry).  I thought it did 
as well, but it does not, look it up.  You are correct that the threads will 
give better cooling though.  I you wanted super cooling, you might thread a 
few washers spaced with nuts to act as fins, but this may increase the 
weight and drag, making it impractical on all but a stronger motor.  
Tungsten will indeed last longer, But I never used it until I started using 
high current MOTs (I used steel before, which is not at all ideal, but it 
worked).  Good luck Shaun.
Scott Bogard.


>From: "Tesla list" <tesla@xxxxxxxxxx>
>To: tesla@xxxxxxxxxx
>Subject: Re: propeller gap help (fwd)
>Date: Sat, 21 Jul 2007 09:14:26 -0600 (MDT)
>
>
>---------- 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)
>
>Shaun,
>
>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.
>
>Jason
>
>
>
>
>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)
> >
> > Shaun,
> >      That depends on what you want you electrode speed to be.  My advice
> > for
> > 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
> > size
> > 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
> > just
> > 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
> > >
> > >
> > >Hello,
> > >
> > >I recently aquired a small sychronous motor, 1800RPM oriental motor.  I
> > >want
> > >to use it with my 12 Kv, 60 mA NST.  How long should the propeller rod 
>be
> > >if
> > >I'm going to use 1/4" tungsten rod.  I've seem a guy on ebay selling it
> > by
> > >the inch.
> > >
> > >thanks,
> > >
> > >Shaun Epp
> > >
> > >
> > >
> >
> > _________________________________________________________________
> >
> >
> >
> >
> >
>
>

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