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Re: Semi-Rotten Spark Length


  Finn -

  You are correct in that the continuous spark is actually a series of
individual sparks  occuring at each bang. It should be noted that the
controlled spark makes all of the sparks the same length and not varying in
length as in the typical TC operation. When the sparks are the same length
they will produce an approximate constant load.

I agree that a standardized spark test for Tesla coils is needed if coil
comparison tests are to be useful. However, I realize that recommendind a
method that gives shorter sparks would not be a popular test with coilers.
The advantage of the controlled spark is that it makes comparison test more
meaningful because the load is not varying.

  John Freau is performing some interesting experiments that are helpful and
can be used to set up a TC data table. He is finding the charge (not
overall) efficiency by using    cap watts/input watts. The problem with this
method is that the cap watts are not constant and will vary with  the length
of each output spark.

  I have not heard of a method to determine the cap watts for each output
spark during a continuous spark test. In order to find this cap watts one
would have to find the difference in joules in the cap both before and after
the particular bang. This requires knowing how much voltage is left on the
cap after each discharge. The one shot test would not help because the
output sparks depend on the previous spark conditions during continuous
operation.

  John Couture
-------------------------------

-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Sunday, May 30, 1999 4:08 AM
Subject: Re: Semi-Rotten Spark Length


>Original Poster: Finn Hammer <f-hammer-at-post5.tele.dk>
>
>Tesla List skrev:
>>
>> Original Poster: "John H. Couture" <couturejh-at-worldnet.att-dot-net>
>>
>>   Finn -
>>
>>   I did not intend to "dismiss" spark performance. Only wanted to point
out
>> the limitations of using sparks for testing and rating Tesla coils. The
>> controlled spark presents a constant load to the Tesla coil similar to
the
>> Prony brake presenting a constant load when testing an electric motor.
>> Varying length sparks do not do this.
>>
>>   John Couture
>
>Yes, I think I get it: You want a _continous_ spark, one that doesn`t go
>like this: streamers, long hit to ground rod, streamers, streamers, hit
>to ground rod...etc. etc.
>Now, as far as I recall from 1/2 year on this list, you are the only
>person who insist on this Controlled spark, and it makes perfect sence
>to me, that this would make direct comparison btwn coils more fair, and
>thus usefull.
>I have also found by my own experiments, that it makes a difference,
>which kind of breakout point the spark is leaving the top terminal from.
>And what kind of shape the grounded rod has at the receiving end.
>The intent of my question was, therefore, to encourage you to step
>forward with a proposal for a standard geometry of these emitting and
>receiving points, which, if they became generally accepted, could become
>standard equipment around the coiling community.
>This way, one more obstacle to comparison would be overcome.
>Anyway, I will make a proposal myself, to make basis for a discussion.
>
>The emitting point for a controlled spark must be situated at the end of
>a 3/8 " /10 mm copper pipe, and have a radius of 3/16 " / 5 mm. The rod
>must be vertical, leave the toroid at the equator, and be of a length,
>so thet the point of the emitting hemisphere is 6 " /150 mm from the
>surface of the toroid.
>The receiving electrode of the grounded rod must exibit equal
>properties.
>
>Please view in a fixed-width font such
>              as Courier.
>
>
>
>
>This could be made from a piece of copper strap, bent to follow the
>radius of the toroid, with a weight at the one end, that rests on the
>centerplate of the toroid, to avoid that the whole thing slips down, at
>the other end a copper pipe is soldered, with a acorn nut at the end.
>
>
>        ********         6" / 150 mm
>     ***        ***  <---------------->
>    *              *
> ++* <--Weight      +----------------++ <----- Brass acorn nut
> ++*                +----------------++
>                       ^copper pipe^
>Does this make sence ?
>
>
>Cheers, Finn
>
>
>