Thread-topic: Acrylic sheet for primary coil insulator
Hi Steve,
Well it certainly won’t hurt to try the acrylic so why not?
Do you have any pics of the offending coil? Could the situation be improved by changing the strike rail height, etc, or improving the field control with a larger diameter toroid? Lowering the toroid may help also. Oh, and make sure the impedance between the strike rail and ground is as low as possible...
My coils are also on the higher power side, I have one similar in size to yours and a 12” pig powered one that makes 12+ footers. You can see videos of the 5kW 8.6” one below. Interestingly, having just watched the second video for the first time in a while there may actually be a primary strike! It’s difficult to tell as it may also just be skipping to a different point on the strike rail. Didn’t cause any issues in any case!
https://www.youtube.com/watch?v=_Z98tYReYBUhttps://www.youtube.com/watch?v=WHroMC_zYqU
Sent from Mail for Windows 10
From: Steve White
Sent: Monday, 3 September 2018 11:04 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] Acrylic sheet for primary coil insulator
My coil is probably considered to be on the larger side. It is 8.6" in diameter and uses a 3600 RPM RSG with protection gap. It is powered by a pole transformer and at 4.8 KVA it produces 8 foot streamers. I do have a strike rail. The vast majority of the time, the strike rail absorbs the errant streamers. On occasion, however, a streamer will strike the primary coil. In one instance, after striking the primary, the streamer then jumped over to the secondary coil. Although no damage was observed, I certainly don't like the idea of streamers striking the delicate secondary coil. So this is my motivation for considering the acrylic sheet. I wouldn't even consider this if I had to buy the acrylic. I got it for nothing.
Is there anyone that has tried covering the primary coil with an insulating sheet such as acrylic or something else? If so, did it help?
Steve White
Cedar Rapids, Iowa
----- Original Message -----
From: "Gregory Peters" <greg.j.peters@xxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Sunday, September 2, 2018 4:57:31 PM
Subject: Re: [TCML] Acrylic sheet for primary coil insulator
Personally I would only use the acrylic if you want to stop people from touching the primary - which is normally only an issue on small coils that people actually have the guts to get close to.
The strike rail will do a great job of preventing primary strikes on it's own. Just be sure to leave half to one inch gap in it to prevent it from acting like a shorted turn. Save that nice sheet for something more useful.
If it's a regular SGTC a properly made safety gap with a grounded centre post may also help prevent damage from an inadvertent primary strike, but really in 20 years of coiling and quite a few coils I have never seen the coil arc past the strike rail to the primary.
Cheers!
Greg.
-------- Original message --------From: Steve White <steve.white1@xxxxxxxxx> Date: 3/9/18 1:50 am (GMT+10:00) To: Tesla Coil List <tesla@xxxxxxxxxx> Subject: [TCML] Acrylic sheet for primary coil insulator
I am considering adding an acrylic sheet as a top cover for my primary coil to minimize primary strikes. I never would have considered such a thing because of the expense but I recently acquired a large sheet of 5/16" acrylic sheet for nothing, so that idea has now returned. My question concerns the strike rail. Should I install one with this cover or not? Here are my options as I see them:
1. No strike rail
2. Strike rail in the normal position on top of the acrylic sheet
3. Strike rail under the acrylic sheet
My concern with number 1 and 3 is that if a streamer finds its way around and under the acrylic sheet, the streamer may melt or burn a portion of the acrylic. I have heard of at least one coiler that has installed such an acrylic sheet and I recall that he placed the strike rail under the sheet. I forgot the link.
Steve White
Cedar Rapids, Iowa
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