Re: Spark length vs watts

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 7/22/01 3:44:02 PM Eastern Daylight Time, tesla-at-pupman-dot-com 
writes:

> Original poster: "S & J Young by way of Terry Fritz <twftesla-at-qwest-dot-net>" <
> youngs-at-konnections-dot-net>

Steve,

Twins give longer sparks for a given input power.  I use the equation:

   spark length inches = 2.4*square root input power (watts)

for twin coils.  I figure about 58" from a twin at 600 watts.

Greg Leyh's original large coil gave a rather linear response,
double the break-rate gave double the spark length.  His
electrum however worked differently.  I think that as coils
become more efficient, they tend to follow the square law.
In any case, I've found high break-rates to be much less
"efficient" than low break-rates.  Your measurements
are really measuring the effect of different break rates in
addition to measuring input power.  Using break rate
increases, I've found that doubling the input power increases
the spark length by only about 20%.  However I see you're
seeing the full 40% increase in some cases, which follows
the square law.  I would think your input power should 
double when your break-rate doubles, but in many cases
it doesn't.  Any suggestions why this might be?

Your work is appreciated.  

John Freau
---
  
>  
>  List,
>   
>  I took a few somewhat crude measurements of DC power into my twin TC vs 
> spark
>  length.  I held the voltage constant at 12 KV and varied the BPS and 
> measured
>  the milliamps and spark length as best I could.  It appears spark length is
>  proportional to DC watts raised to the 0.45 power.  This plots as a 
straight
>  line approximately.  (Plotting spark length vs sqrt power gives a curved 
> plot.)
>   
>  Data is as follows:
>   
>  BPS    watts    spark inches
>   25     60        10
>   50    108        12
>  100    228        18
>  150    384        24
>  200    600        28
>  250    720        31
>  300    864        34
>  350   1056        37
>  400   1188        39
>  450   1308        41
>  500   1440        42
>   
>  Spark lengths are difficult to determine.  My TC is a twin, and I used two
>  sharp breakpoints extending past the toroids aimed at each other.  When 
the 
> two
>  coronas start to connect, the center inch or two brightens considerably
>  (interesting effect).  That is the condition I measure the spark length.
>   
>  So I wonder if John Freau's "efficiency" formula would be a bit more 
> accurate
>  if it was 1.7 x wall power raised to the 0.45 power?
>   
>  Someday I will try to get some data where power is held constant and 
measure
>  spark length vs BPS.  I may have to wait until I get my triggered SPDT 
spark
>  gap going as my RSG seems to crud up rapidly, degrading performance and
>  affecting measurements.  Electrodes are #10 brass bolts.  (I know - use
>  tungsten ...)  
>   
>  --Steve
>