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Messages - MRMILSTAR

Pages: [1] 2 3 ... 11
1
Voltage Multipliers / Different styles of HV electrodes
« on: July 14, 2020, 09:34:39 PM »
On large Marx generators, CW multipliers, and other HV equipment I often see large shielding electrodes  composed of many smaller bowl-shaped elements. I assume that this construction technique is used because its simpler to build and is a close approximation to an ideal shape such as a toroid or sphere.

Other times I see the shielding electrode made from tubular sections which, in the Tesla coil world, we usually call a skeleton electrode which again is a close approximation to an ideal shape.

And then other times I see an actual spun aluminum electrode with the ideal shape.

Does anyone know why one technique is used instead of another? I assume that its just simplicity of construction and cost for the large electrodes. The attached image shows examples of these.

2
It doesn't look like copper oxidation. I am guessing that its a degradation of either the varnish or the magnet wire insulation. I have no idea why though.

3
I've never experienced that problem. You are the first person that I've ever heard having that problem. Are you using PVC for the secondary coil form? If so, PVC can absorb moisture. The best practice is to apply a coat of varnish to the inside and outside of the tube before winding the coil. This prevents moisture from getting into the PVC. I also store my TC equipment in an environment that has no more than 50% humidity. Are you using magnet wire for the secondary coil?

4
Voltage Multipliers / E-Bay Marx generator
« on: June 27, 2020, 09:36:57 PM »
I just saw this very interesting Marx generator on E-Bay. No specs unfortunately. I wonder if its actually a CW multiplier. Does anyone know anything about it?

https://www.ebay.com/itm/MARX-IMPULSE-GENERATOR-LIGHTNING-INDOORS-MADE-BY-VARIAN-SEMI-CONDUCTOR-FREE-SHIP/184340134249?hash=item2aeb873969:g:qD8AAOSwsvhe8-iR

5
Spark Gap Tesla Coils (SGTC) / Re: power factor correction
« on: June 27, 2020, 04:36:50 PM »
PFC has no benefit to performance. It is useful if you are running close to your circuit breaker trip point. PFC will lower the real wall current and allow you to draw more real power from the wall outlet without tripping the circuit breaker. If you already have plenty of margin on the wall current I see no value.

6
This capacitor has been sold.

7
Solid State Tesla Coils (SSTC) / Re: Secondary parameters
« on: June 22, 2020, 05:20:07 AM »
There are several excellent web sites that explain the theory of Tesla coils. This is one my favorites.

http://www.richieburnett.co.uk/tesla.shtml

8
Transformer (Iron Core) / Re: Neon transformer
« on: June 01, 2020, 11:55:28 PM »
Spark gap firing might be tricky with only 5000 VAC to work with.

9
Richie's site works fine for me. Here is the link that I use.

http://www.richieburnett.co.uk/tesla.shtml

10
If you mean the 4hv site, the site is "working" for me. By "working" I mean that you still can't post images but you can still access all areas of interest and view the postings.

Try this link:

https://4hv.org/e107_plugins/forum/forum.php

11
Sell / Buy / Trade / Re: How to get rid of stuff?
« on: May 21, 2020, 05:23:40 AM »
Treasure to the right person. If I didn't already have a fully-assembled magnetic core board I would take it off of your hands.

12
Solid State Tesla Coils (SSTC) / Re: I have fried my router!
« on: May 13, 2020, 11:29:30 PM »
Do not touch the sparks regardless of what you see people doing on Youtube! Even though you may not feel much, that current is flowing through your body. You don't feel much because your nerves do not respond to frequencies in the Tesla coil range but that current is still flowing through your body.

Don't believe that skin effect myth either. The skin effect is only significant for excellent conductors such as copper, gold, silver, or aluminum. Your body is a poor conductor and the skin depth extends pretty much all the way through your body. If the power of your coil is significant, you can be doing nerve damage and/or partially cooking your internal body parts. You can also get skin burns.

I have seen videos of people letting Tesla coils with output power of several kilowatts and more discharge through their body, even their head! They are idiots and are conducting an experiment with unknown results on their body. The damage to their body may not show up until years later. Use common sense. Do you think that its a good idea to let kilowatts or even hundreds of watts of power flow through your body even if you can't feel it? Its OK to touch the output of a very low power coil such as a plasma ball or small battery-powered models but not any coil with any significant power output. I never let anyone touch the streamers from any of my Tesla coils no matter what the power level is.

13
Capacitor Banks / Re: Crimping using pulsed power
« on: May 11, 2020, 09:37:31 PM »
Doing this little experiment made me think of the huge problems encountered during the WW2 plutonium bomb development. They had to determine a way to use explosives rather than magnetic fields to compress a plutonium core with practically perfect spherical symmetry. Its sort of a similar problem as crushing this copper cylinder with perfect symmetry minus one dimension, except that I didn't achieve perfect cylindrical symmetry by any means.

14
Capacitor Banks / Re: Crimping using pulsed power
« on: May 11, 2020, 05:12:52 AM »
The work coil is completely sacrificial. Being sacrificial is actually good for the capacitor because the work coil disintegrates before any voltage reversals occur.  I had considered the idea of machining a heavy-duty G10 containment structure for the work coil just to hold it together a little longer to allow more work shrinkage.

I wonder what the re-usable work coil for the commercial pulse power crimpers looks like?

15
Capacitor Banks / Crimping using pulsed power
« on: May 09, 2020, 10:02:16 PM »
I was playing around with my pulsed power machine a few days ago and decided to try something different. I took a 2 inch long piece of 0.875 inch diameter copper pipe and did a shrinking experiment. I placed the piece inside a 12-turn 12 AWG work coil and hit it with 7000 Joules. The result was an almost-perfect hourglass pinch. The work coil wasn't wound tightly against the pipe so I could have done the same thing with less energy with a tighter coil (better coupling) but I already had a few of these spare work coils made for quarter shrinking laying around.

This technique is actually used in industry where one piece has to be crimped on to another piece. Supposedly this method produces a better more uniform crimp than can be accomplished mechanically.

16
Very nice coil! I have only built large SGTCs and VTTCs. I haven't gotten on board yet with SSTCs. Of all the SSTC designs that I've seen the QCW types interest me the most. If I ever build a SSTC it will be the QCW type.

17
About 10 years ago before I retired and was working for an aerospace contractor, I was waiting at our local airport for departure to a conference when I noticed a USB flash memory stick laying on a seat. I picked it up and put it in my pocket. Several days later after I returned to my office, I popped in the memory stick to see what was on it. This was at a time before it was common knowledge that malware could be spread on a memory stick. It turned out that another employee at our company had accidentally left it at the airport and I returned it to him. I did notice that it was full of company engineering data. Lucky that I found it.

Today, if I saw a memory stick laying around at the airport I would still pick it up but there is no way I would insert it into my PC. If I had a sacrificial PC not connected to the internet I would probably take a look at its contents.

18
It becomes crumbly and brittle. I've heard that the brown areas can also become conductive.

19
Spark Gap Tesla Coils (SGTC) / Re: My 4.25" coil so far
« on: May 02, 2020, 11:09:02 PM »
Outdoor operation can be a big nuisance however if you want to produce the big streamers, outdoors is where you have to be unless you're one of those lucky people with a big pole barn. I'm not.

My 6.5 KVA SGTC with 9-foot streamers is outdoor operation only. It takes me about 15 minutes to set it up.

20
Spark Gap Tesla Coils (SGTC) / Effect of UV radiation on white PVC
« on: May 02, 2020, 05:41:09 PM »
About a week ago I was inspecting the base of my SGTC (6.5 KVA) and saw this brown spot on the bottom of the secondary coil form. This spot is about 4" x 4" and is in the direct line of site of my RSG electrode gaps. Its about 12" away from the spark gap. The UV radiation from the spark gap is so intense that it has turned this spot on the PVC tube brown. Total exposure time to UV was probably about one hour.

My fix was to use aluminum tape to cover that spot and protect it from further UV radiation damage. The pictures show before and after the patch.

The lesson learned is to remember that white PVC is very susceptible to UV radiation damage.

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