Re: A few questions about coil designing

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

Original poster: "Bunny Killer" <bunikllr-at-bellsouth-dot-net> 

Hey David...

sounds alot like my BIGPIG Coil...

my secondary is.... bottom 10" of wind is #10THHN  the rest,  45" of 
#18    12.5"X55"

on the primary...   why 5/8"   Im using 3/8" with .25" spacing ( and Im 
running 2 pigs in series for 30KV) and get an occasional primary flashover 
( Im thinking it occurs when a bug falls between the turns.... hell of a 
bug zapper)

my toroid is 12"X52"   with a smaller 6"X24" below the main toroid

caps..   Im using 4 Maxwells at .114uF all in series   each rated for 
50KV    for a total V of 200KV with a rough estimate of .025uF total

maybe you should consider series for the caps  100KV at .050uF

my original setup used 2 1256D's in paralell   ( basically one for each leg 
of the 240 line)  and kept the current around 30A max for short runs
the newer power supply has 4 1256Ds which allows 60A runs for extended 
times ( several minutes instead of seconds)

as far as the rotory spark gap    if you supply the G-10 and Tungsten I can 
supply the smaller parts and machine shop capacities  ( email me on this 
one...  )

Scot D




Tesla list wrote:

>Original poster: "David Rieben" <drieben-at-midsouth.rr-dot-com>
>Hi All,
>
>I am in the process of constructing a fairly big coil with a 12 3/4" x
>44" long secondary wound with 897 turns of #17 heavy build Essex
>magnet wire. That makes for just over 3000 feet of wire.
>The primary is 12 spiralled turns of 5/8" OD soft copper
>tubing with the outer most turn at nearly 40" diameter. There is an
>approximate 1/2" spacing between each primary turn.
>
>For the primary capacitor I will be using either one or two paralleled
>.1 uFd, 50 kV Hipotronics commercial pulse capacitor(s). These are
>Tesla coil specific custom capacitors that Jeff Parisse was using for his
>Model 10 coil. I'm thinking that .1 uFd will be sufficient primary
>capacitance for my design.?
>
>The power supply will be either a 10 or 15 kVA, 14,400 volt pole trans-
>former (have one of each), controlled and ballasted with (2) paralleled 1256D
>Powerstats and a Lincoln 225 amp arc welder core set for the maximum welding
>amperage. The arc welder's core guts have removed from the factory steel
>box and placed in a tank of transformer oil to increase the duty cycle.
>
>The rotary gap will most likely be ASYNCH G-10 and tungsten
>with a variable speed DC or universal drive motor. I may have to
>break down and pay someone to do this part for me as i am
>no machinist and I do want it to be right :^))))
>I have designed and built big coils before but I want to make sure
>that I get this one right the FIRST time ;^)
>
>My questions are: Will there be a problem of turn/turn flashover
>on the outer turns of the primary coil since there is often less than
>1/2" spacing between the adjacent turns? If it's tapped at say the 7th
>turn then there's 5 additional unused turns that can develop an auto-
>transformer effect. I may just remove most of the unused turns if
>this proves to be a problem once tuned in.
>
>Also, my Hipotronics pulse caps are the single bushing, steel
>can type with the steel case grounded to the terminal opposite
>of the bushing. I'm thinking that I'll need to place the capacitor
>in parallel with the transformer instead of the spark gap in paral-
>lel with the same, otherwise I'll end up with the entire exterior
>case of the capactior floating at 14,400 volts ;^O. I've heard that
>this wiring variation of the primary circuit places more strain on
>the transformer but since I'm using a pole transformer, I don't feel
>that this will be an issue in this case.
>
>I plan on building a 12" minor diameter toroid from aluminum flex-
>duct tubing from McMaster-Carr, with a major diameter of 48" to
>54". I'll probably also use a smaller toroid (4" minor diameter x
>16 to 20" major diameter) for a corona shield of the topmost
>turns of the secondary. With a toroid this large, will .1 uFd be
>sufficiently large for the primary capacitor? It seems that my
>power supply combo may not have suffiecient power to drive
>.2 uFd of primary capacitance. Any comments welcome ;^)
>
>David Rieben
>
>