Re: [TCML] 12"/16" Large Coil Diameter Selection

["Peter Terren" <pterren@xxxxxxxxxxxx>]

My 18 inch coil is here.
http://tesladownunder.com/Tesla_coil_18inch.htm
I get sparks to 11 feet (121 inches from a 50.5 inch winding for a ratio of 
2.4. It is driven by 2 PT transformers drawing 240V 75A but could take more 
power.
The former used was custom welded polyethylene with end caps and flanges for 
easy attachment of accessories. It cost $250 Aust (US$260) some years ago.
My only concern is that nothing sticks to polypropylene so when I had to 
remove some windings, there was a tendency for the remaining windings to 
slip.
It is very light compared to a comparable PVC tube. Not sure about sonotubes 
though.

So what should you do? Go for 16 inch.
Consider:
Do you need structural strength to be able to sit on top for shows (Google 
Lords of Lightning)
Do you need to attach supports for your toroid and for mechanisms to control 
a rotating breakout point.
(I believe everyone should and I use that on all my coils).  I rapidly get 
bored with a simple coil.
Are you going to have the secondary adjustable in height or the primary to 
adjust k. Preferably on the fly but it wont be as structurally strong for a 
large coil.
(I would fix the secondary and make the primary height adjustable.)
Use the most ridiculously large toroid. like larger than truck tube size. 
Don't worry about it being bumpy if you are using a breakout point as I 
almost always do.
Currently I use an 18 inch flexible plastic duct tubing which unfolds around 
a flange and inverted bucket to give an external diameter of just over 4 
feet. It should really be bigger like 5 feet.
The great thing about the toroid is that I join the ends with Mori clips 
(special paperclips). Remove these and the toroid concertinas down to 18 
inches by 12 inches and weighs nothing. Great for travel
With a breakout point there are no sparks from the toroid so no damage to it 
from sparks but the metal spiral takes these anyway.
With no breakout point I recommend a second toroid or large corona ring 
below the first to direct sparks upwards, reducing primary strikes.
With a single toroid adjust spacing from top winding as per DC Cox's 
recommendations.
If you want performance questions, play with Java TC with various figures 
that you want to try.

Please note my post - my real tip to all coilers.


Cheers
Peter



-----Original Message----- 
From: Ln2guy42@xxxxxxx
Sent: Saturday, June 04, 2011 5:06 AM
To: tesla@xxxxxxxxxx
Subject: [TCML] 12"/16" Large Coil Diameter Selection

Hello everyone!

I am planning on winding a large secondary coil and have an option regarding 
diameter size.

I have on hand a large supply of 18 awg magnet wire as well as two segments 
of sonotube. They are both 60" in length, but one is 12" in diameter and the 
other is 16" in diameter. The coil will be powered by a 14.4 Kv 10 kw pole 
transformer.

I have researched the archives and found that the main considerations in 
designing larger coils to be the lower aspect ratio (suggested to be 3:1), a 
larger diameter (for it is more "efficient" and can handle more power), as 
well as aesthetic design (overall coil size versus spark output length).

I was wondering if anyone had any suggestions/comments on which coil 
diameter to use based on any criteria that are important in this decision.

I am also curious to know how a 4" increase in diameter of a secondary coil 
will make a difference (if any) in coil performance with regards to the 
above criteria.

Thank you so very much for any input and I appreciate all comments.

Amir M.


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