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Re: First light great.

Original poster: "Bart B." <bartb@xxxxxxxxxxxxxxxx>

Hi Daniel,

Tesla list wrote: 
Original poster: "Daniel Koll" <dk_spl_audio@xxxxxxxxxxx>

Ok, thanks. I will try making a toroid first but have some questions. When I make the disc out of wood, should I cover the whole thing in AL tape?


Yes. This is just a simple way to place a center disc into the toroid. Obviously, anything metallic will also work, but I usually have wire spool ends around so I use them for the purpose. Simply find something like a round wire spool end or whatever that is already round and near to the inner diameter of the toroid selection. If for example, you choose a 3"x12" toroid, the inner diameter would be a 6" disc. Before you cover with Al-Tape, drill a hole through the disc. The hole would be for a small diameter bolt (rounded head) used for attaching the top secondary wire to. Cover in Al-Tape completely (top, bottom, and sides). Use a glass jar or similar to rub the Al-Tape as smooth as you can get it. Then, place the bolt through the pre-drilled hole and fasten with a nut. The nut side should be inserted from the bottom of the disc up to the top so that the side which is facing the secondary has minimal protrusions.

Even the bottom? Anything else I should know? I will start with the 3"X12" that you recommended unless someone on the list doesn't think that is a good starting point.


After building the inner disc, simply form the flex tube to the same shape so that the disc rides center of the inner diameter. You should use Al-Tape again around the entire toroid to make it as smooth as possible. I just tear off strips and place them one at a time until it's to my liking. This will secure the disc to the tube and create a nice small toroid. Use the glass jar on the tube as well to rub out any protrusions from the tape.

I set up a little coil a few weeks ago and had an old Al-tape toroid I used. I decided to go into the garage and take some photos. Sometimes pictures are better to explain these things. I'll pop them up to my website.
http://www.classictesla.com/temp/Img_0615.jpg
http://www.classictesla.com/temp/Img_0618.jpg
http://www.classictesla.com/temp/Img_0619.jpg

Be careful with the Al-tape. It can be sharp.
If I would have known about the coupling I would have changed my design.
This is my first coil and I had never heard of this ever being a problem. I ran the coil for probably 2 1/2 minutes total with this issue. The secondary seems to be fine and in as good condition as when I started, I hope the streamers didn't make pin holes through the enamel and polyurethane. If the new toroid does fail then I guess I will remove some of the secondary windings. My secondary is wound for 16" so if I take off a 1/4-1/2" I don't think the output will be reduced too much.


No, the output would not be affected. There are many things which could have happen. Coupling and tuning are two most common problems coilers run into. Both can cause racing sparks and can often be difficult to distinguish which (or both) may be the problem. There are other possibilities as well. If a visual inspection of the coil looks ok (both inside the form and out), the coil is likely ok. They can take some abuse to a degree.
Finally, many people said that maybe it was just out of tune. Isn't the coil tuned when you achieve the largest spark output? All I did was trial and error until I saw what I think was the biggest sparks.
This is a perfectly suitable method to tune the coil as long as nothing is damaged in the process. With high powered coils, this can be chancy. Your coil is not high powered, so I think it's fine. However, a far more precise method is to calc the system first. Unless the user made an error in the calculations, usually only minor adjustment is necessary for best output.

It would probably be a good idea to give further specs on other parts of the coil. Such as: cap size and type, spark gap, primary turns, primary inner and outer dimensions. These are the common specs for running a pretty good analysis on your coil. With that info, the coupling and tuning can be calc'd very precisely. JAVATC will tell-the-tale if you give it accurate data. If your uncomfortable with the program, just give your specs here and I'll run it for you.

http://www.classictesla.com/java/javatc.html

Take care,
Bart B.

Thanks

From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: Re: First light great.
Date: Thu, 26 May 2005 09:01:45 -0600

Original poster: "Bart B." <bartb@xxxxxxxxxxxxxxxx>

Hi Daniel,

There is no rule that the bottom secondary and primary should be on the same plane. However, often it can be close. A good practice is to always build into your design the ability to adjust the coupling by moving the secondary (or primary) as necessary. In the event the coil is not constructed for this adjustment, then unwinding a few turns from the bottom secondary will perform the same function. However, I doubt your coil is coupled too tight (a hunch). Most likely, the coil is out of tune and the sphere isn't helping. The coil would behave better with a toroid rather than a sphere simply due to the shape of the toroid and how this shape interacts with the voltage stresses at the top of the coil. Large spheres will perform better than smaller ones, but breakout power comes into play with larger spheres.

I would recommend first a small toroid (3" x 12" or near). You can use most anything. Simple Al-flex tube from Home Depot has been used for years. Make a round wooden disk and cover in Al-tape. Insert the disk into the center of the toroid. The disk aids in the voltage stress shielding. You can also use Al-tape to hold it all together. Second, tune the coil. Use a program, trial and error, or whatever suits you. Then, if you still have racing sparks, you can go after the coupling. Considering your construction doesn't support an easy coupling adjustment, I would put it last on the list.

Take care,
Bart B.

Tesla list wrote:

Original poster: "Daniel Koll" <dk_spl_audio@xxxxxxxxxxx>

No I was not using a break out, I just attached my secondary magnet wire to the bottom of the sphere using aluminum tape. Should I change something? I cannot change the height of my primary or secondary without massive reconstruction. It would take hours and hours to change now. I was told that the bottom of the secondary and primary should be on the same plane so that is what I did. Thanks

From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: Re: First light great.
Date: Tue, 24 May 2005 20:47:13 -0600

Original poster: jdwarshui@xxxxxxxxx

Hi Daniel

I would agree with Gary about being overcoupled but it is also likely
that you need to re tap your primary. We usually place our spherical
capacitors directly on the end of the secondary. Many coilers believe
that spheres are inferior to toroids but I am not convinced that this
is true and have never seen any evidence to support this assertion.

Are you using a breakout on your sphere?

Jared Dwarshuis