re: 20 joules at 100 bps vs 4 joules at 500 bps - any difference?

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Original poster: FutureT@xxxxxxx 



this old posting shows some comparisons I had done some time ago
regarding different break-rates.  The coil was powered by
a potential transformer in these tests.   JF

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>Original Poster: FutureT- repost from May 30, 1999.


                                                      spark
                   cap-watts watt     watt   length     eff
BPS   Joules   calc    meter   meter  inches   factor %    eff.

120     3.85      463      550     2.6        42         88       84

240     5.41      650      800     3.8        42         88       81


I should mention that in the table above from my previous posting,>that the 
240 bps joule figure is based on two bangs, so the figure>is really joules 
per ac half cycle.>>But I did some more tests:>>First, I adjusted the gap 
phase by a few degrees to better equalizethe>bang sizes, this had no 
noticeable effect on the TC operation or>efficiency.>>I started thinking 
some more about the whole comparison, and I>started to wonder if I might be 
seeing the effect of a sort of "sweet>spot" in the coil, which could be 
skewing the results.  As a cross->check, I did a new test, running the coil 
at 240 bps with the same>bang sizes as previously used at 120 bps.  This of 
course doubled>the input power, and the spark increased by 23%.  Next I ran 
the>coil at 120 bps, but used the smaller bang size equal to that 
used>previously at 240 bps, and of course the spark was shorter.  Here's>a 
new table showing the new results:>>



BPS              cap-watts watt   amp     spark
          Joules    calc    meter   meter    length     increase>

120      2.7        325      400      1.8         34"

240      5.41      650       800     3.8         42          23%

120      3.85      463       550     2.6         42

240      7.7        926      1100                  51          21%

>>These results suggest that doubling the power input by a doubling>of the 
break rate (keeping bang size the same), gives about 1/2 the>spark length 
benefit as a doubling in cap size instead.  A doubling>of the cap size 
(bang size) gives about a 41% spark length increase>(shown by other 
experiments).  So these new tests continue to>indicate that longest sparks 
for a given wallplug input power can be>achieved with low break rates with 
larger caps.  Again the 240 bps>joule figures in the table above are for 2 
bangs (1/2 ac cycle).>>These tests also show that charging efficiency 
remains good at the>higher break break rate.  The inefficiency of high 
break rates must>be occuring due to the physics of spark growth in the 
air.  The>sparks are brighter and fuller though at the high break rate, so 
it>would seem that at high break rates, the power is going 
partiallyinto>creating fuller, brighter sparks, and partially into making 
themlonger.re>>John Freau