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Re: Scroungein' (fwd)
>>Original Poster: "christopher boden" <chrisboden-at-hotmail-dot-com>
>><snip>
>>Project 1
>>Design Goal: To produce 5' discharge from a 120VAC <20Amp input.
Attainable!
>>Secondary size: 25" X 4"
>>Secondary winding: 26 AWG? (any ideas?)
24 or 22 ga are also good choices. Look for "Heavy build" or the
thickest coating that you can get your hands on.
>> Secondary form Schedule 40 PVC 4" pipe with glued on endcaps
You are better off with the thin walled stuff like SDR.
>>Winding method: Lathe....BIG lathe.
>> Primary winding: 1/4" soft copper tubing
>> Primary form: Flat helix?
Flat helix or something with a small angle will be fine. I wouldn't go
over about 15 degrees or you may have to significantly raise the
secondary to prevent flashover and other problems associated with high
coupling. I am fighting that battle right now...
>>Primary size? Number of turns/spacing????? any ideas?
Many people have good luck using spacing about the width to the tubing.
I used 1/4" tube and 3/8" spacing with good results. The 3/8" gives you
a little more room to place your tap. You need to do some math on the
sizing issues. You should get your hands on one of the Tesla Coil
Calculation programs that are floating around out there and numerically
test various configurations. I like the excel spreadsheet by Sonderman
/ Ruch. I have it on my page at
http://www.geocities-dot-com/CapeCanaveral/Cockpit/3377/tesla/index.html.
>>Caps: Where can we get some? What size do we need? How long will they
>>ast? We need rock-solid-reliability.
The only way that you will get "rock-solid-reliability" is with
commercially built caps such as Maxwell. Be prepared to spend hundreds
of dollars if you find them surplus and around $3000 if you contact
Maxwell directly and have them do a special run. Why not build rolled
LDPE, salt water, or MMC? Most coils in the size that you mention do
well with between .01 and .05 uF. Typically, coilers design the cap
size to allow for resonant charging, but there has been some discussion
lately that this may not be the optimal way. A .027 uf should produce
resonant charging for (2) 12/60s in parallel.
Again, consult some equations or one of the TC calc programs for more
insight into sizing various coil components.
>>NST: 15KVAC -at- 30mA
You have big aspirations if you want 60 inches of arc from this... I am
getting 50 inches out of (2) 12/60s in parallel.
>>Variac: ? what size do I need 20A?
A non-PFC 15/60 NST draws about 9 amps. You will probably draw about
half of that with your current NST. Most variacs are good for 2X their
rated value for short runs. I have been running my (2) 12/60s off a 10
amp variac for some time with no problems at all. Bigger is better if
you catch a good sale.
>>Spark Gap:Static (no shrapnell) possibbly the Quick model
I have great results with my RQ gap.
>>Torus: ?? biggest possible?
Depends on what you want. If you want it to be pretty and have many
streamers dancing around in the air, then you will want a smaller
Toroid. When you go for your distance records, you will want a larger
toroid. It isn't all that difficult to make the toroid so big that you
will never get spontaneous breakout. In order to get breakout, I have
to put a sharp point on my 7" dryer duct torroid with a 29" inch OD. My
4" x 20" is much more exciting to watch.
>> Anything else? What am I forgetting?
The filter network to protect your NSTs is non trivial. Several of us
in the So Cal area are having good results with Terry's RC filter, but
the resistors dissipate about 75W each with 120ma flowing through them.
Needless to say, it doesn't take them long to get really HOT.
Commercial EMI/RFI filters are a good idea to keep RF out of your variac
and house wiring.
Be careful.
<snip>
>>Christopher A. Boden
>> The Geek Group
>>344 Ionia SW
>>Grand Rapids MI
>> 49503
>>(616)-574-4065
>>The Geek Shall Inherit the Earth!
Making arcs in Huntington Beach, CA,
Ross