Re: TC resonance estimation?

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

Original poster: "Mike Panetta by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ahuitzot-at-mindspring-dot-com>

On Thu, 2002-07-18 at 13:46, Tesla list wrote:
> Original poster: "Malcolm Watts by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>
> 
> Hi Mike,
>         The good news is that you can *choose* the frequency you wish 
> to operate at and design a secondary coil to do it for you. Several 
> simple equations and an idea of what you want to achieve are all you 
> need. The bad news is that if you design for a low frequency and a 
> small coil to do it, the secondary losses will soar exponentially 
> which is not good, especially for a CW coil where RMS currents are 
> typically higher than a disruptive coil.

Would a coil of other then a 6:1 aspect ratio fix the problem with
losses?  I was thinking about making a 12" x 2" coil until I saw that
the resonance frequency (with a particular top load) would be somewhere
around 1MHz...  This was someone elses project that I found on a web
page out there on the web (it was a google search for ' small tesla
coils '), so MMMV (My Milage May Vary ;) I guess...  Do you know of any
web sites off hand that would describe how I would go about choosing my
resonance frequency, and what the tradeoffs are of the various size
coils?

> 
>      Medhurst, Wheeler are the names to remember and there must be 
> plenty of data on what adding a particular size of terminal to a 
> particular size of secondary does to frequency in the archives. The 
> final *minimum* radius of curvature of the terminal will determine 
> what output voltage you can reach (assuming copper losses are kept 
> low enough) before the coil can break out with a spark.

Do you think a google search on the names you gave above would return
any useful results?  I think I may do the search anyways and find out
myself ;).  As for the top load, I was thinking of using a steel float
that I have as the top load, but I do not know how well it would do. 
Its not spherical, but its kinda more like a short cylinder (maybe 3
inches) thats has a hemisphere at each end to cap it.  As you can see, I
am trying to keep this as cheap as possible to start with by using as
much of things I already have on hand as possible ;)


> 
> Regards,
> malcolm
> 
> 

Thanks for the post,
Mike