Re: Aspect ratios and teflon

["Malcolm Watts" <M.J.Watts-at-massey.ac.nz> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi Sam and everybody in general,

On 14 Aug 00, at 15:57, Tesla list wrote:

> Original poster: "Sam Beck" <Sam-at-peterbeck-dot-com> 
> 
> I've designed my secondary to be 3" by 12" and wound with 26 gauge wire.
> I've heard that an aspect ratio of 1:4 is desirable for small coils, but
> now it seems to be the contrary.  Can anybody clarify this?  And does
> anybody know if virgin teflon is a good capacitor dielectric?

The reason why there is much disagreement/controversy over 
different approaches to various aspects of coiling is that the 
different answers that are popular are addressing different 
situations and design goals. A 4:1 aspect ratio is great if 
your goal is a high Q secondary and you use a wire size that 
restricts the turns count to around a thousand and you're 
using a moderate sized topload. 5:1 using the same diameter 
coilform is obviously better if you want to give your coil a 
better voltage handling capability. Unloaded secondary Q's are 
not terribly important since they are generally pretty high 
unless the form material is damp or the wire is excessively 
small (which can mean a much higer voltage rise than you 
bargained for and attendent flashovers) and generally, higher 
losses in the secondary.
     My money goes for more coil height for something designed 
to produce long sparks but less for a compact tabletop model 
which is operated from an isolated *low power* DC-DC inverter  
in which case I don't mind seeing the entire coil throwing 
streamers from all over its length in every direction.

Regards,
Malcolm

*Engineering is the art of compromise to fit a specification*