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Re: Interesting but not so impressive results...


From: 	George W. Ensley[SMTP:erc-at-coastalnet-dot-com]
Sent: 	Sunday, September 07, 1997 10:36 PM
To: 	Tesla List
Subject: 	Re: Interesting but not so impressive results...

Rodney,

Looks like your coil is getting close to resonance in the 3/4 wave mode.
You could do with a lot more C or L in the primary to bring it to 1/4
wave resonance. I wouldn't push the power up or it will begin to break
out at the bottom 1/3 and distress the insulation. 


At 01:04 PM 9/7/97 -0500, you wrote:
>
>From: 	Rodney Davies[SMTP:rgd872-at-anu.edu.au]
>Sent: 	Sunday, September 07, 1997 8:24 PM
>To: 	tesla-at-pupman-dot-com
>Subject: 	Interesting but not so impressive results...
>
>Hi All,
>
>Well, tonight I finally got around to arcing up my old 12" coil...
>I'm using a 500W bar-heater as a current limiter, and a pole-pig 10KVA
>11KV SWER transformer.
>The capacitor is approx 0.02uF. (home made rolled job).
>
>Here's some brief specs -
>Secondary - 
>900+ turns, self-resonates (unloaded) at 77Khz.
>1mm enamel coated wire, space-wound at 21 turns/inch.
>PVC former diameter - 12.5"
>Aspect ratio - 1:3.75
>
>Primary -
>5 turns of 3/8" copper pipe spaces at 3/4" between turns (archimedes).
>
>spark gap at this stage is a single static.
>
>>From tonights effort, I figured I was getting around 5-7KV out of the
>transformer, probably about 200-300Watts...
>
>The coil is currently unloaded, so the wire was merely sticking up in the
>air from the top of the secondary... (yup, I know...should be loaded).
>
>Well, I did actually, with various round metal objects, but that decreased
>the output significantly, so I left it unloaded since that was where the
>longest arc was occuring...
>
>Now here's the dissappointment, I was only getting about 4-5" of arc...
>
>Yup, you're right, she's way out of whack! out of tune, out of
>everything...even the capacitor is too low, should be around 0.1uF...
>Anyway, plenty of time for the fix-ups...
>
>The major point of tonights exercise was to observe the wave of the
>secondary coil... Here's what I did, and I know what you'll say - don't
>arc from the windings!!!
>
>Ok, I held an earthed wire in my hand, holding it approx 6" away from the
>side of the secondary and observed the corona.
>There was a definate faint corona occuring, but the interesting part is,
>what sort of corona I obtained whilst moving the earth wire up and down
>the length of the secondary.
>
>Ok, about 5" from the bottom, the corona was bright and dense and the arcs
>that did occur were fairly violent... I then moved the wire further up the
>secondary and observed that approx 1/3 the way up, I had the strongest
>corona and most violent arcs. 
>Then, I moved the wire further up and noticed that the corona almost
>dissappeared at about 2/3rds the way up, but then became brighter within
>4" from the top.
>
>Perhaps a diagram may help explain...
>
>
>	Secondary.
>
>	_________
>	|	|   <---- started to become brighter.
>	|	|
>	|	|
>	|	|
>	|	|   <----- virtually no corona
>	|	|
>	|	|
>	|	|   <----- brightest.
>	|	|
>	|	|   <----- earth wire ---+
>	|	|   medium brightness	 |
>	---------			---
>	Base.				 \\\
>
>
>I guess this is an indication of what the wave is doing...
>
>Also, there could be alot of contributing factors -
>1/ zero quenching on the single-static gap
>2/ completely out of tune
>3/ No toploading
>4/ primary circuit no where near in resonance
>5/ secondary re-coupling energy back to primary
>
>etc..etc...
>
>But, I'm sure I'll fix it up soon, just need more money... 
>Some, if not most of you will agree, big coils are an expensive hobby! :-)
>
>Anyway, I was just wondering if anyone would like to elaborate on the
>corona effects I observed with the secondary?
>
>Yes, I know, never arc to the windings...but it's a really bodgy coil, so
>I guess it really doesn't matter...
>
>
>Thanks Guys!
>
>Have fun!
>
>Catchya!
>Rod
>
>
>
>
>
>
George............