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Re: [TCML] Burnt Joint (Cap Bank)

I have used black HDPE from (tapplastics) on 3 coils for primary supports, strike rail supports and base with no problems. And the best part is that they cut to size "cheaply" which will save you some considerable time.


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-------- Original message --------
From: Jim Lux <jimlux@xxxxxxxxxxxxx> 
Date: 05/12/2013  1:34 PM  (GMT-08:00) 
To: tesla@xxxxxxxxxx 
Subject: Re: [TCML] Burnt Joint (Cap Bank) 
On 5/12/13 1:08 PM, Mike Gray wrote:
> Okay thanks for that - I'm not too bothered about transparency in the
> plastic, and it appears that the transparency will cost you extra, so I'll
> go for some HDPE. Black probably, should look quite smart.

oops.. when it comes to HV, "black is bad"..

A lot of times they use carbon black (a conductor) as the pigment. 
You'd want to get a small sample and try it.  If it's a $5 cutting 
board, that's easy. If you're ordering from a plastics distributor, get 
the breakdown voltage specs, or have them send you a small sample for 

> Anyway before I order I need to know what minimum width I'm going to need
> on the sheet, and since I need to re-wind my secondary I will probably make
> it a bit wider and taller. My current secondary, at 5.6cm diameter and 27cm
> tall, only has approximately 600 turns... which should be more like 1000+
> yes?

600 is fine. It's really more about what the inductance and capacitance 
are, relative to the series resistance.   Run one of the modeling tools.

You're at 4.8:1 height/diameter which is fine. When people talk about 
long and skinny, they're talking about those 30" tall by 3" diameter 
coils wound on mailing tubes that were popular in the 60s and 70s.

> If I used a 4" diameter form for the secondary, and wound a 50cm tall coil
> on that, that would give me just over 1000 turns. Are those dimensions
> suitable for me? My NST is 10kV, 50mA.

Run JavaTC and find out.  You're right at 5:1 which is fine.  You might 
want to look at reducing the number of turns. slightly bigger wire will 
have less loss. Spacewinding (e.g. with monofilament between turns) 
might be another idea.


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