[TCML] caps and efficiency

[bartb]

Hi Woo,

That little bipolar is nothing much. I used the beer bottle caps 
purposely for the Seibt coil as high corona is wanted in that type of 
coil and beer bottles are of course nicely lossy. I built about 14 beer 
bottles caps but ended up using only 2. I plan to build a little mmc for 
the bipolar coil (4 x 17 mmc using some wima caps). This will 
dramatically help it's performance as a true bipolar coil. For the Seibt 
I wanted high corona for the grounded brass wires running down the sides 
of the coil (which is where the wave pattern along the coil can be 
observed which is the intention for the Seibt). Normally, an induction 
coil would be used, but since I didn't have one, I simply wound the 
bipolar (worked fine for the purpose). Adjustment was simple since all I 
had to do was slide the secondary left or right within the primary. 
Given it's proximity, this made for a simple tunning adjustment.

Your tcbor cap efficiency is not surprising compared to the lossy 
doorknobs. Your tube coil looks like a fun coil to play with. I'd love 
to do some audio modulation myself with a coil someday. Were one of 
those families with about 10 guitars in the house, so it seems natural 
to go that route at some point. But, I just haven't taken the leap yet.

Take care,
Bart

dr.hankenstein at earthlink.net wrote:
> Bart,
>
> That's a pretty neat little coil.I like the "beer bottle" caps. How are they for efficiency? Dr. Jeff helped me make a TCBOR type homemade oil-filled cap back in the mid nineties for my table top coil. I compared this highly effiecient cap to a series-parallel arangement of 100 doorknob caps approximatley equal in capacitance to the tho TCBOR cap recently. Here's what I found:
>
> Doorknobs: (690pf-20kv times fifty caps in parallel) times two banks in series ran at 12kv-60mA full throttle for over an hour. No heating, no flashover. very lossy, only about 1/2 the performance of the TCBOR cap. The reason I ran so many caps in parallel (MMC) was to overt the possibility of heating up, as the ceramic doorknobs tend to drift as much as 20% as they heat up. I was considering using one bank of these caps in my 833C plate as the main tuning cap. As it stands, I aquired a nice mica transmitting cap, so I used the ceramic cap bank as RF bybass with a large VLF Plate choke instead.
>
> Here is a picture of the coil and progress so far:  http://www.drspark.org/images/tubecoil/Dsc_0004.jpg 
>
> The coil runs in three modes: (1) AC/MOT-pulsed with SCR for conventional "sword" shaped sparks. (2) Pure DC cathode-modulated using pulse input from Audiotesla MKIIc Tesla coil controller (I use this mode to play guitar, keyboard and Theremin through the tube coil) Output sound in this configuration very closely resembles that of a DRSSTC coil. (3) Pure DC grid-driven with 100 watt PLC amplifier/oscillator/modulator. (I use this mode to connect to a Sony Walkman CD player.....very interesting) I am presently working on phasing control to explore improved operation and efficiency. This is a prototype coil. It allows me to mimic ideas I would like to try out on a solid state coil. Difference is that the tube coil can handle alot more abuse (accidents and oops') than its solid state counterpart....less tempermental.
>
> Woo
>
>
>   
>> [Original Message]
>> From: bartb <bartb at classictesla.com>
>> To: Tesla Coil Mailing List <tesla at pupman.com>
>> Date: 5/3/2008 10:33:19 AM
>> Subject: Re: [TCML] bipolar coil
>>
>> Hi Woo,
>>
>> Dr. Jeff must be using a small cap size for the turns. This is an actual 
>> bipolar coil also, unlike what I think Kris is building. Dr. Jeff's 
>> bipolar is a nice little coil! I built one similar in size, although it 
>> was not used as a bipolar coil, but rather a hv source for a Seibt coil.
>>
>> http://www.classictesla.com/seibt/Img_2870.jpg
>>
>> I've been wanting to turn this thing into a self-contained bipolar coil 
>> (however I need to replace the wooden primary runners with something else).
>>
>> Take care,
>> Bart
>>
>> dr.hankenstein at earthlink.net wrote:
>>     
>>> Kris,
>>>
>>> Here is a picture of Dr. Jeff's small bipolar coil: http://www.drspark.org/images/jeffbipolar/Dsc_0185.jpg  If I recall correctly, he's using a 9kv / 30ma neon sign xfmr with a Sangamo mica transmitting capacitor and a 5-break stationary spark gap. Tuning doesn't seem to be very critical. Secondary is rather small, maybe 2" x 12" or so. Small coils are alot of fun!
>>>
>>> Woo
>>>   
>>>       
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