winding lathe built -> Enamel-coated copper wire on PVC water pipe - PVC cement to hold the windings / Tesla Coils / Forums

Forums

4hv.org :: Forums :: Tesla Coils

« Previous topic | Next topic »

winding lathe built -> Enamel-coated copper wire on PVC water pipe - PVC cement to hold the windings

previous 1 2 3

Move Thread

LAN_403

tarakan2

Sun Oct 12 2014, 12:16PM

Registered Member #3859 Joined: Sun May 01 2011, 03:47PM
Location:
Posts: 179

Hazmatt_(The Underdog) wrote ...

tarakan,

IF YOU DO THE RESEARCH... you will find that transmission velocities in coaxial cables is often 0.86 x c

But this varies depending on the medium.

The propagation is also on the surface of the medium, this is the skin effect, which is another headache!

AND if the copper is silver plated, now you're dealing with an extremely conductive medium plated onto a second medium, whereby most of the RF energy, if not all, is inside the 3 mils of silver, and the copper is just acting as a mechanical support.

AND ALL OF THIS... goes right out the window with Tesla coils because they are NOT IDEAL antennas, so antenna theory doesn't really matter at this point.

If you really want to go down the rabbit hole, the secondary has multiple resonances which approaches a ladder network in simulation.

Honestly, just build your coil and be done with it, and stop worrying about minutia.
It takes about $20,000 in equipment to measure these small problems, and who has the time, seriously.

Tesla transformer is not wound with coaxial cables.
Proportions of height to width are also pure BS according to Tesla's own patents and drawings.

I am winding a long and skinny one 1" in diameter with a 36AWG.

Dr. Slack

Sun Oct 12 2014, 02:36PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

Tarkan

I feel your pain and frustration, it's evident in each of your posts. You have a heard a lot of things about Tesla coils, and are having difficulty separating the true from the false. One of the joys of TCs is that they behave in such a strange, almost magical way. As they are complex, well, more complex than an antenna or an LC circuit, a lot of people think them magical. I forget who said that any technology with more than half a dozen variables is indistinguishable from magic.

Anyhows, there is a sizable body of people who think that the most efficient way to run a TC secondary is to have the wire length = lambda/4 at the resonant frequency. It has an emotional appeal, and it is possible to build or tune a TC to that relationship. However there is no emperical evidence to suggest that it's true. The fact that the wire on the secondary is close wound, and the nearest electrical things to each turn is the one above and below means you certainly cannot analyse it like an isolated wire.

Why do you want to build a Tesla coil?

If it's for the impress the friends and family stuff, then follow the well tried and well tested route. There are a great many rules of thumb that work quite well, ones like use 1000 turns on the secondary, or make it between 3:1 and 5:1 height:diameter ratio. You can't really go wrong following those. The secondary is the difficult thing, wind that, and then trim everything else to match. Forget Tesla's patents, the man was barking towards the end of his life, a pity really, but that's the way it goes sometimes. Read Hazmatt's posts, and Dr DC, you asked, and they are trying to help.

If it's to investigate electromagnetic theory, then you will need to know what B and H fields are, and a lot more besides. A TC is probably too complicated to attempt to understand all its behaviour from the ground up, but it is a lot of fun.

If it's to delve into the magical theory, then it will rapidly become a waste of time airing it on this forum.

It's a little disappointing to see a man on the one hand asking questions, but on the other dismissing height/wdith ratios as BS. If you have made up your mind it's BS, then you are uneducateable. The reason 4:1 is the ratio to go for is a complex mix of the conductivuty of copper, the typical frequencies TCs run at and so the skin depth, the impedance of free space, the typical coupling coeffieicnts that work well (so 8:1 is too long), the sort of trajectory a spark takes out of the topload towards a ground some distance away (so 2:1 is too squat), and a whole bunch besides. Most importantly, it's an emperical observation made by hundreds of people before you who have made sucessful Tesla coils. Don't follow it by all means, but expect to have to work harder to get a good result.

Hazmatt_(The Underdog)

Sun Oct 12 2014, 03:44PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

Spot on Neil.

Tarakan, pick yourself up a copy of "The Ultimate Tesla Coil Design" and let that be your bible.

Mitch Tilbury presents a very thoughtful analysis, But as a researcher and Electrical Engineer myself, I know that his numbers do not make much sense.
(In short his input power to output and wire considerations are way off.)

He had in the past downloadable spreadsheets to calculate every aspect. I am not sure if the website is still available, but if it is, it should be at

I have been researching this subject for over 14 years, I have all the books (Inductance calculations, Transient theory, Design of Inductance Coils, etc.), a bunch of equipment, and still no answer yet.

There are over 40 variables to consider, each related to another, including your friend H/D ratio.

H/D ratio determines the pitch of the winding, the TURNS!!!, RESONANT FREQUENCY, RESISTANCE DC AND AC, SKIN EFFECTS, HEATING, coil height like Neil said (you dont want it just arcing to itself) JUST TO NAME A FEW!!!

So no, its not BS.

And you totally missed the point of the transmission velocity, which cannot be measured in a single conductor. There has to be a return path. The point was that transmission IS NOT IN A VACUUM, it is in a conductor, so it can be close to 0.86 x c, so no, you cannot calculate the velocity based on the speed of light, there is a correction factor for the transmission medium.

PICK UP THE BOOK, WIND THE COIL.

Andy

Sun Oct 12 2014, 04:10PM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874

Hi tarakan2
What I was meaning is that the primary is linked to the secondary by magtnic fields and the secondary is linked to the ground plane by static fields.
If I was going to build a Telsa coil I would find the secondary antenna length say 1km, then make the primary have 50% frequency of the secondary length, then build a top load to bring the thing into resonance.
A static field at 450-500V can in juice 5V at 100meters into a conductive object.

previous 1 2 3

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob