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Re: [TCML] Re: Toroid Size
Hi Greg,
I can answer that, no, there is not, however you can size a toroid to
the wattage of the system (and I suppose you can size a secondary
similarly, but it is not a direct relationship.) The formula John came up
with some time ago is [top load overall diameter = 0.5 through 0.9*(SQRT
power)] in inches and watts. Something to note, for a normal-ish toroid,
the overall diameter in inches is roughly equal to the capacitance in pF.
I have found this to be very accurate, going beyond 0.9 stops output, and
going below 0.5 gives to many streamers to count. I like to shoot for 0.9
personally... For sizing a secondary I just like to take the predicted
spark length and divide by 2.5, and that is the length, then size the
diameter according to 4.5 to 1 H/D, then size wire gauge for 1200 turns.
Please note, your top load will "look" too big if you do things this way,
but trust me it performs swimmingly... I've gotten used to over-sized top
loads, I'll never go back.
Scott Bogard.
On Tue, Aug 13, 2013 at 2:11 AM, Greg Leyh <lod@xxxxxxxxxxx> wrote:
> Hi John,
>
> Is there a good rule-of-thumb for sizing a toroid to a given secondary
> dimension? I'm planning on using a 4x16 toroid with a 5x32 secondary
> winding. Does that seem like a reasonable match? I'm about to wind the
> secondary and thought I'd ask first.
>
> Cheers,
> Greg
>
>
> Hi Brandon,
>>
>> Yes, it's definitely possible to have a toroid that's too big. If the
>> toroid
>> is too big, sparks will only break out when using a breakout point or
>> bump.
>>
>> The proper size of toroid depends on how many sparks you want to
>> see coming off the toroid. If the toroid is large enough to produce
>> only one spark streamer... well then you'll get one streamer. If the
>> toroid is smaller, then you'll get two streamers, and if smaller yet,
>> then you'll get 3 streamers, etc. The smaller the toroid, the more
>> streamers, but they'll be shorter.
>>
>> I happen to like the look when the streamers oscillate from side
>> to side of the toroid and occasionally show 2 full streamers. This
>> will give pretty long sparks and good spark action. To me this is
>> the most exciting type of look. Some folks prefer a full head of
>> streamers, etc.
>>
>> Low break rate coils probably need a little larger toroid to get just
>> one streamer.
>>
>> On my TT-42 TC which gives 42" sparks using a robust 12/30 NST,
>> I use a 4" x 13" spun toroid and I get about 3 simultaneous sparks
>> I guess. I tested a 6" x 24" toroid on the coil and it gave a single
>> streamer but needed a breakout bump to break out reliably.
>> Clearly a 6" x 24" toroid was too large in my view. However the
>> sparks were a little longer, about 44" or so. I didn't try a 5" x 16"
>> toroid, but that would have been interesting to try. Folks often use
>> a 5" x 16" spun toroid for a 15/60 NST powered coil. I used to offer
>> a 5" x 16" size but it was just too time consuming to make.
>> I do offer a 4" x 13" spun toroid ($165, free shipping in USA,
>> as-spun finish). Amazing Science ( www.amazing1.com/toroids.htm )
>> offers a 4.5" x 18" toroid for about $240 I think plus shipping. I have
>> no connection with them.
>>
>> My website is:
>> http://futuret.110mb.com
>>
>> Cheers,
>> John
>>
>>
>> -----Original Message-----
>> From: Brandon Hendershot <brandonhendershot@xxxxxxxxx>
>> To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
>> Sent: Sun, Feb 19, 2012 5:55 pm
>> Subject: [TCML] Toroid Size
>>
>>
>> Hi List,
>>
>> It's been quite a while since I hung up coiling, looks like the bug's back
>> though.
>>
>> So I finally got myself a job and some stable income (:D) and can finally
>> afford to buy a spun aluminum toroid for my coil.
>>
>> First question; Can you have a toroid that's simply TOO big? I'm
>> suspecting
>> that my 4"x16" Al Ducting/Pie Pan do-dad is a bit too small. Would a
>> 6"x24"
>> Spun Al toroid be too big of a jump?
>> I suppose it would be helpful to plug it into JavaTC, but It's not working
>> on my browser right now, and I simply don't want to measure my up whole
>> coil again (old PC died).
>> Before I go through that errand, does anybody have any wisdom for me
>> regarding using bigger toroids?
>>
>> You can see how my 4"x16" looks here: teslacoilers.blogspot.com
>>
>> Thanks Everyone,
>> Brandon H.
>>
>>
>>
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