Re: First Light for 10" Coil.

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

Original poster: Bart Anderson <classi6-at-classictesla-dot-com> 

Hey Peter,

Very nice! Love seeing a 6-MOT coil doing this well!

I personally also appreciate the .wmv file type for the movie (compact size 
and good quality!).

The coil is no doubt doing very well. I couldn't help myself but run 
through your specs (as I do with everyone's). You mentioned Fres at 85kHz 
or so. This must be without the toroid or the self resonant frequency. With 
the topload, it should have measured down around 67 kHz. It appears your 
tapped at the self resonant frequency, which is low on primary inductance 
(about 22%). Couping is currently at 0.14. It should tune in at around 8 
turns and I bet you could get away with a little higher coupling (maybe 
1/2" lower on the secondary to primary proximity).

It's hard to say that with a coil that is running so well, but I'll say it 
anyway.

Anyway, I mostly just want to congratulate you on an excellent build of a 
nice and powerful 6-MOT BEAST!!!

Take care,
Bart



Tesla list wrote:

>Original poster: "Peter Reid" <peter-at-reidconsulting-dot-com.au>
>Hello Everyone on the Tesla Coil Mailing List.
>
>I have just finished building my new MOT powered 10” Coil and managed to 
>tune it somewhat. I am quite happy with the results so far, however I am 
>wondering if anybody could shed some light onto areas I should work on In 
>order to improve the spark length and power handling capabilities of this 
>coil. So far I have managed occasional 8.5ft Power Arcs to a grounded rod. 
>However I feel that the coil is still capable of a lot more. Initially the 
>spark output was quite poor until I increased the coupling between the 
>primary and secondary. (I don’t think I’ve gone too far).
>
>I will list the specifications below. With the current setup I am getting 
>quite powerful arcs to the strike rail and ground with-in about a 3ft 
>radius around the coil.
>
>I have posted some photos on my website for anyone that’s interested. I 
>also have some pretty good video footage, but that isn’t on the webpage. 
><http://tesla.reidconsulting-dot-com.au/>http://tesla.reidconsulting-dot-com.au 
>Any input / help with improving the current setup would be greatly 
>appreciated, I am just a little worried about burning up my secondary if I 
>try and pump any more power though it.
>
>
>
>Coil Specs are as follows..
>
>Primary
>Flat Spiral, Wound with ½ In Copper tubing, spaced but ½ inch.
>ID = 12.7in
>OD = 32.5in
>Turns = 10.25, tapped at about turn 6.15
>Primary sits 1.5ft above the ground on a specially made wooden platform.
>Strike Rail = 1/2copper tube raised by ½ inch around outside of primary.
>
>Secondary
>Wound on a 10” PVC pipe, which has been baked and sealed with many coats 
>of polyurethane.
>Winding length = 41in
>Wire Diameter = 0.9mm B&S Gauge 19
>The bottom turn of the secondary is elevated 1 inch above the top of the 
>primary winding.
>
>Toroid
>12” x 42.5” (Tube Diameter x Outside Diameter of Toroid)
>Mounted 12in above the top winding on the secondary.
>
>Measured Res Frequency of Secondary is 84.8kHz, and primary has been tuned 
>to exactly that. (Can someone please tell me if its worth trying to detune 
>it by 1/3 of a turn to account for streamer loading etc?.)
>
>Capacitor
>0.15uF MMC Cap Bank made up of 144, 942C20P15K caps.
>
>Power Supply
>6 MOT Supply, Currently Ballasted to 40A -at- 240V (Using a Sliding Choke Balast)
>Maximum line draw current of 80A -at- 220v when the ballast is removed. 
>That’s 17.6kVA J
>Approx 12kV output.
>
>Spark Gap.
>200bps Sync Gap, with a Remote Phase Adjuster.
>Single Gap, Tungsten static electrodes, and 4 x 8mm brass threaded rod 
>(moving electrodes) Spinning on a 12in
>G-10 disc (3000 rpm) Gap spacing is about 1-2mm total.
>
>
>BTW, Thanks to everybody who has contributed to the mailing list, the help 
>I have received from you guys has been invaluable.
>
>
>Regards
>
>Peter Reid.