Re: Resonance Theory

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Matt,

On 17 Oct 2001, at 17:06, Tesla list wrote:

> Original poster: "Matt Shayka by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<lightningcreator-at-hotmail-dot-com>
> 
> List,
> 
> I have a theory that I came up with. I need to tell this story first:
> 
> One day, while in a theme park, I was waiting for a few friends to get off a 
> roller coaster. Behind the bench I was sitting on was a fancy metal fence, 
> and one end of it was cut off. I dunno why. But I put my finger on it, and 
> started pushing on it slowly and steadily out of boredom. I kept the pace 
> steady, and the section of fencebegan to bounce wildly. then, as the rest of 
> the fence started to creak, the frequency of the fence lowered and my finger 
> was no longer in sync with the fence. I thought about it, And I also thought 
> about the swing so often used to descibe resonance. as the amplitude 
> increases, the frequency lowers because the seat has a greater distance to 
> travel. And the observation that makes me belive this:

Should not the frequency be independent of amplitude? It is in a TC 
resonator (leaving spark loading effects aside). As the amplitude 
increases, the rate of change (speed of swing) increases also but the 
period of oscillation remains the same. I would suggest that the 
frequency changed as more fence was excited, in effect lengthening 
the resonator.
 
> I was fiddling with my coil one night. I had recently gotten it to work 
> muuch better than it was by removing the topload completly. (just a wire 
> now) It now throws a 10" streamer with half the original 1kW tank circuit. 
> (still pretty bad, but improving...) I watched the length of the streamers 
> carefully. They start off at 8", grow to 10" over a 3 sec. period, then 
> stop, and start all over again.(the output never actually "stopped".)

That behaviour is typical of TCs - sparks grow with time through 
repetitive hammering of the discharge channel.At some point, growth 
stops when there is insufficient energy in a primary shot to cause 
any further channel growth. Convection serves to increase the channel 
stretch (upwards) lengthening it beyond what a shot can deliver. I've 
never been sure why the channel then completely recedes while a new 
one forms.
 
> I think it starts off at a high frequency, and then lowers as the amplitutde 
> increases.  It would be real hard to make a primary do that...
> 
> Anyone else have this happen?  Comments?

Monitoring with the oscilloscope shows there is no substantial 
frequency difference between a secondary excited with a few mW and 
multi-kW of power.

Regards,
Malcolm