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omegalabs

Sat Jan 24 2009, 07:14PM

Registered Member #1521 Joined: Thu Jun 05 2008, 10:46AM
Location: Hungary
Posts: 128

Hi! I have a question. I use nitro lacquer (I don't know how it's called in english) for secondary coil, but it charges up electrostatically and produces sparks on the secondary surface, on high power. As I see, some people use polyurethane coating, but I can't find here in Hungary, or on ebay. Can someone offer me a good insulator coating?Â Â Â Â Â Â Â
Thanks.

Mads Barnkob

Sat Jan 24 2009, 07:41PM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

You are getting what we call "racing sparks" and this will happen to any secondary that is too tight coupled to the primary, or have a too thin varnish.

How many layers of varnish did you give your secondary? and what kind of tesla coil is it operating in?

Arcstarter

Sat Jan 24 2009, 10:38PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Hello, what Dr. Spark uses is Minwax fast-drying clear-gloss superior durability polyurethane. I use it too, and it work very well. It is quite cheap, really.

I have used it on my new coil, and it is easy to apply and dries enough for the next coat in 30 minutes to an hour.

That is me coating it with it. It is near the exact same polyurethane, but mine says clear gloss, and the one on ebay is clear semi-gloss. I am not sure what the difference is.

Hope it helps.

omegalabs

Sun Jan 25 2009, 12:57PM

Registered Member #1521 Joined: Thu Jun 05 2008, 10:46AM
Location: Hungary
Posts: 128

MadsKaizer wrote ...

You are getting what we call "racing sparks" and this will happen to any secondary that is too tight coupled to the primary, or have a too thin varnish.

How many layers of varnish did you give your secondary? and what kind of tesla coil is it operating in?

Yes, I know the coupling is matter, but I think the nitro coating is still the problem. I used this coating on several secondary coils, with 1 or 2 layer, but every secondary produces the same racing sparks on medium coupling. I realize this just now, yersterday.
A fatally secondary spark melt the wire between two windings, just before a show, where was 400 people. Fortunately I improved the secondary in time (that was in september 2008). This is my 11,8 inch (300mm) coil :

I working now on a 3 phase 12kW 12MOT powered DC coil, and I want to sure, that the secondary is insulated well.

omegalabs

Sun Jan 25 2009, 01:01PM

Registered Member #1521 Joined: Thu Jun 05 2008, 10:46AM
Location: Hungary
Posts: 128

Arcstarter wrote ...

Hello, what Dr. Spark uses is Minwax fast-drying clear-gloss superior durability polyurethane. I use it too, and it work very well. It is quite cheap, really.

I have used it on my new coil, and it is easy to apply and dries enough for the next coat in 30 minutes to an hour.

That is me coating it with it. It is near the exact same polyurethane, but mine says clear gloss, and the one on ebay is clear semi-gloss. I am not sure what the difference is.

Hope it helps.

Thanks, this is really cheap, but the shipping is 30$

I think I buy one soon.

I meaning about, that can I use this coating on my original nitro coating? Or I must clear the secondary before I apply the new polyurethane coating?

MOT_man

Sun Jan 25 2009, 05:36PM

Registered Member #1127 Joined: Mon Nov 19 2007, 12:08AM
Location:
Posts: 139

omegalabs wrote ...

Hi! I have a question. I use nitro lacquer (I don't know how it's called in english) for secondary coil, but it charges up electrostatically and produces sparks on the secondary surface, on high power. As I see, some people use polyurethane coating, but I can't find here in Hungary, or on ebay. Can someone offer me a good insulator coating?Â Â Â Â Â Â Â
Thanks.

Nitro lacquer depending upon its age can be slightly acidic and isn't recommended for insulating purposes at all. Polyurethane or Varathane brand varnish can be found in hardware stores internationally.

Dr. Drone

Sun Jan 25 2009, 08:00PM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
Location:
Posts: 1673

omegalabs

Sun Jan 25 2009, 10:07PM

Registered Member #1521 Joined: Thu Jun 05 2008, 10:46AM
Location: Hungary
Posts: 128

MOT_man wrote ...

It's work well on small coils.. but for medium and big sized coils it's not god. (the nitro)

omegalabs

Sun Jan 25 2009, 10:18PM

Registered Member #1521 Joined: Thu Jun 05 2008, 10:46AM
Location: Hungary
Posts: 128

Dr. Spark wrote ...

omegalabs wrote ...

I meaning about, that can I use this coating on my original nitro coating? Or I must clear the secondary before I apply the new polyurethane coating?

You may be able to give the secondary a light sanding and cover with polyurethane. This issue possibly here is the two do not get along or the polyurethane will not stick. Sand a little spot ( 800 grit wet/dry) on perhaps the bottom of secondary (where no one will see and no wire) with polyurethane and then wait a week. Look at the spot a week later under good light for crakes, fractures, or just anything that would make the first coating worse. Then scratch with fingernail to see if it holds on.

You can use any polyurethane; just call around at wood restore shops, furniture shops etc as someone has it.

Polyurethane is a good insulator and if you look on insulation charts it is high on the list, used in sheets in very high end x-ray transformers.

Have been reviewing a lot of interest in coatings, as there are a lot of coating that work well and a lot that do not. Maybe we can start a post on â€œSecondary Coatingsâ€ with pictures and videos that we can add/refer to when needed.

Cheers,
Ch

Is water based polyurethane good too? Many urethane lacquer is used for parquet coating that you can get in the shops here, and most of them are water based. I wasn't sure if water based coatings work well for insulation purpuses.

Andyman

Sun Jan 25 2009, 11:35PM

Registered Member #1083 Joined: Mon Oct 29 2007, 06:16PM
Location: Upland, California
Posts: 256

I'm not sure if it would really matter. The base evaporates either way, if I remember. Water base seems to cure much faster.

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