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Re: [TCML] New Coil

Hi Miles,
It's not too difficult really. Note that Javatc gives a "minimum" proximity between coils. This value (minimum proximity) is determined by the ability of voltage breakdown between coils and therefore requires a transformer input to be calculated. It is wise to add 1/4" to 1/2" above this value. There is no rule on a 2" gap (simply an empirical recommendation that is sometimes too wide and sometimes too narrow). I prefer to calculate it, but note that most coils will be in the 1.5" to 2" range regardless.
In any event, if you see that the minimum proximity is for example 1.5", then set your primary diameter to accommodate this value plus say 1/4" (primary radius = 1.75 + sec radius).
Now, if you desire a 0.14 coupling and your primary ends up below sec bottom turn, then you need to increase the inner diameter of the primary to attain that. For a reality check, realize that primary coils can be adjusted below, right at the sec bottom turn, or even above the bottom turn. It's placement is preferred to be even or below the secondary bottom turn (since the voltage across the secondary increases with turns). However, coupling is rather important for decent performance. You might be surprised at how many coilers pay little or no attention to these guidelines and still end up with great running coils. 

Hope that helps,

Bart

Miles Mauldin wrote:

Hi Bart,
Am I using the tool incorrectly then? You are right, it does not output any diameters, those are inputs. I am questioning the values I had to input to arrive at a coupling of .14k. I do not believe I have seen any photos of a coil design that had the bottom windings of the secondary below the plane of a flat primary. Also every other tool I've used, and research I've done, suggests the inner diameter of the primary be at least 2" greater than the outer diameter of the secondary form. I am just guessing I'm not using the tool correctly. Any guidance would be appreciated. Thanks, 
Miles



________________________________
From: bartb <bartb@xxxxxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Wed, March 10, 2010 8:29:09 PM
Subject: Re: [TCML] New Coil

Miles,
The recommended minimum proximity in Javatc is calculating the distance as the "nearest points" as noted in the help file. If Javatc tells you 1.5" as the minimum proximity, then it's looking for a primary diameter that meets this distance. Javatc does not suggest a primary diameter in any of it's outputs. 

Take care,
Bart

Miles Mauldin wrote:

Could that really be correct?  Using the javatc tool it suggests my primary inner diameter to be only 1.5" greater than the secondary form (a difference of .75" radius), and to obtain .14k coupling the lower end of the secondary is .5" below the primary.  I worry when the primary and secondary is that close; should I?




________________________________
From: John Forcina <forcijo10@xxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Mon, March 8, 2010 1:22:52 PM
Subject: Re: [TCML] New Coil

If i read correctly in this photo,
http://www.cmnow.com/TeslaMan/Toroid/tn1.htm You plan to have your primary
coil 4" That is going to be way too low and your coupling between your
primary and secondary coils will be very small allowing very little energy
transfer into the secondary coil.  I recommend you plug your coil specs into
Javatc http://www.classictesla.com/java/javatc.html .  Adjust your primary
height and diameter and adjust your primary coupling to about K=.14

On Mon, Mar 8, 2010 at 12:58 PM, DC Cox <resonance@xxxxxxxxxxxx> wrote:

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