First Light for 10" Coil.

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

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.