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Re: 120bps vs 240bps tests

In a message dated 99-06-05 06:03:42 EDT, you write:

<< Original Poster: "R.E.Burnett" <R.E.Burnett-at-newcastle.ac.uk> 
 
> Hi John, Malcolm, and all,
 
> More excellent test results,  I really wish I had time to take more
> measurements.  I found that by using a HV scope it was easier to
> figure out what was going on in the rotary with different caps
> and HV supplies.

Hi Richie, Malcolm, all,

Thanks, I agree it's nice to actually measure the bang size on the
scope, thereby making it easy to separate charging efficiency, and
spark growth efficiency.  Gap losses are still an unknown with this
set up though.  I use a solid state scope, and had no problems so far.
 
 >Your results seem pretty conclusive that 120BPS sync is better 
> than 240 BPS sync for best spark length.  Also you seem to be saying
> that power is still processed into "Cap Energy" efficiently at
> 240BPS if I understood you correctly.  Therefore it must be the
> spark that does not grow as well at 240 BPS as we had hoped ?

Yes, the charging circuit seems to work almost as efficiently at 240
bps, which agrees with your (Richie's)simulations.  I think the most
reliable 120bps vs. 240 bps test I did was the one that used a smaller 
bang size for the 240 bps, to keep the spark length constant.  This
way, the main unknown is the gap losses, but somehow i don't think 
they're making a huge relative difference.  In the tests where I kept
the bang sizes constant, but let the spark length increase at 240bps,
the question of TC sweet spots arises.  

I did some new tests to analyze the nature of these sweet spots, 
which I've posted separately.
 
> I plan to do some low power tests using around 300Watts at both
> 100BPS and 200BPS with all other parameters constant.  V will
> obviously by 1.41 times higher at 100BPS to get the same power.
> That is why I am keeping the power low to save the caps.
> I will keep the list posted.

I'll be interested in the results.  But as far as saving the caps is
concerned, does double the break rate at a lower voltage really save
the cap?  Certainly the cap voltage rating has to be appropriate in
either case, but high bps batters the caps too in it's own way.  
 
> I can adjust the phase of my 200BPS gap so that it only fires on
> alternate presentations,  ie. at 100BPS.  Funny enough, this also
> seems to be very close to the best firing angle for a purpose built
> 100BPS gap !  This is fortunate as I can compare 100BPS and 200BPS
> just by adjusting the phase of the gap.  Have you tried this ?

I see what you're saying, and I thought of this too, but didn't try it.
I agree it would make things easy.  I meant to try it, but forgot.  But
I may be doing more tests soon, and I'll try it.

Cheers,
John Freau
 
> Note: 100BPS and 200BPS refer to synchronous operation at 50Hz (UK)
>       120BPS and 240BPS refer to synchronous operation at 60Hz (USA)
 
> Keep the info coming,
 
 >					- Richie
 
 					- In sunny Newcastle.
  >>