Re: RSG gap at side of electrode.

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Ted,

http://www.webelements-dot-com/webelements/elements/text/W/heat.html

tells more about elements than anyone really wants to know ;-))

For tungsten, the magic number is 4.5 E-6 / C.

For every degree C you raise the temperature, it will expand 0.0000045 of 
what it was.  +4.5 x10^-6 / C

So if I have a 1 inch tungsten block and I heat it from 25C to 1000C it 
will end up at...

1.0043875 inches...

Your calculations are correct.  I would worry more about any plastics 
expanding or deforming from centrifugial forces and such.  But, we are 
still talking the thickness of a sheet of paper...

Cheers,

         Terry


At 11:59 AM 11/26/2002 +1300, you wrote:
>Hi Ed
>Ted in NZ here
>Looking at the thermal coefficient of expansion for Tungsten (assuming that
>is what you use) is 1 part per million per deg kelvin.
>So if a 200mm rotor heats up by an average of 100deg delta L is 0.02mm
>
>I'm not a mechanical engineer dealing in this stuff so forgive me if I've
>stuffed up but as you can see with tungsten delta L is pretty small.
>
>Other designs with other metals will be quite different but all in all
>expansion is relatively small and only a problem with high power, longer
>rotors and very close gaps. Again my problem was with brass rotor of 5mm dia
>220mm long running over 5kva and I'd set up the gaps very tight.
>
>Best
>Ted L in NZ
>----- Original Message -----
>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: <tesla-at-pupman-dot-com>
>Sent: Tuesday, November 26, 2002 11:08 AM
>Subject: Re: RSG gap at side of electrode.
>
>
> > Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
><Esondrmn-at-aol-dot-com>
> >
> > In a message dated 11/24/02 2:09:50 PM Pacific Standard Time,
> > tesla-at-pupman-dot-com writes:
> >
> >
> >
> > >Subject: RSG gap at side of electrode.
> > >
> > >Tnx Pete I think that would work well and might have other advantages
>too.
> > >I would not want to over state the expansion problem, it arose for me at
> > >very high power and in special circumstances (ie brass rod rotor) and is
> > >very easily accounted for with a small extra amount of clearance to the
> > >fixed electrodes.
> > >Best
> > >Ted L
> >
> >
> > Since I am in the process of building a new rotary gap, I find this
> > discussion interesting.  With the stationary electrodes set to the outside
> > of the rotating electrodes - will the diameter of the rotating electrodes
> > increase when comparing the static dimension to the clearance when it
>comes
> > up to speed?
> >
> > Ed Sonderman
> >
> >
> >