Help with Custom Cap thoughts??
From: Peter Electric [SMTP:elekessy-at-macquarie.matra-dot-com.au]
Sent: Wednesday, April 08, 1998 6:26 AM
To: Tesla List
Subject: Re: Help with Custom Cap thoughts??
Sounds like good material for caps to me. The main thing is to remove at
least an inch of Al on each side of the plate all round to stop arcing.
A neat way to do this might be to sand of an inch of the paint layer
then place the whole thing in caustic soda solution. Should etch off the
All nicely without blemishing the plastic.
Tesla List wrote:
> From: djQuecke [SMTP:djQuecke-at-worldnet.att-dot-net]
> Sent: Wednesday, April 01, 1998 4:53 AM
> To: Tesla List
> Subject: Help with Custom Cap thoughts??
> Hello Coilers,
> I wrote to the list several months ago about a material I want to try
> building custom capacitors. As usual, I have taken what seems to be a
> fairly simple task and turned it over in my mind for so long that I'm
> thoroughly confused about the basics.
> If you would bear with me I'll try to explain myself and perhaps get a
> couple of rather simple questions answered.
> The material is called ALPOLIC. It is maybe a 3/16" thick piece of
> polyethylene sheet with perhaps a 1/16" thick sheet of aluminum bonded
> each side. It comes in 4' x 8' sheets and you can use wood working
> equipment to cut it, etc.
> Pluses: zero air gap between poly and AL. Poly is thick enough to
> high voltage. Works fairly easily.
> Minuses: The AL sheets have a special paint bound to their surface
> doesn't remove easily. Poly perhaps too thick. Electrical connection
> between plates has me confused.
> The following ASCII drawing (sorry) shows 3 plates connected
> together. The
> easiest manner to connect them would be with UMW rods (E1 and E2) and
> use AL
> bushings between plates for the necessary electrical connection.
> Assume the conductive AL plates C2 and C3 as well as C4 and C5 are
> by AL bushing placed in between them. The UMW rods slide thru the
> Each plate will have two holes 3/8" diameter for the rods to bind
> I'll remove a 5/8" ring of AL on center with each 3/8" hole to avoid
> thru holes. Between twinned plates I will place a 1/2" ID x 5/8" OD x
> thick UMW bushing over the 3/8" UMW rod and then place a 5/8" ID x
> 3/4" by
> 1/4" OD AL bushing over that.
> I'll remove the paint only in a 1" circle center on the holes between
> twinned plates.
> Each plate is about 5" square. I'll remove a 1/4" strip of AL along
> edges on each side of plate to avoid arcover around edges.
> I'll remove paint around holes/rods on end plates and connect leads to
> end. The UMW rod ends will be threaded and I'll use nylon nuts to
> hold it
> all together.
> In this case then the conductive plates C1, C4 and C5 are positive
> and plates C2, C3 and C6 will be negative (don't forget these
> plates are actually bound to the dielectric plates and it can be
> to refer to them separately).
> This requires that an odd number of plates be connected together so
> you a
> pos and neg end plate.
> I figure 25 plates per cap. Should be about 12-13" long, 5" square
> I'm hoping for .0025uF per cap and a voltage rating of at least 50kV
> perhaps actually more like 100kV???
> I've got to get a micrometer and find out how thick this stuff
> actually is.
> Q1: Does this have chance of working? <g>
> Q2: In this scenario do I get to count the surface area of both
> plates C2 and C3 or just one because they are in reality joined?
> Q3: Do plates C2/C3 have to be physically connected to the end plate
> C6 and
> does C4/C5 need connected to C1.... or does the current pass thru C1
> D1, C2 & C3, D2, C4 & C5, D3 and finally C6??
> Q4: Doesn't my design actually just connect 3 capacitors (plates) in
> parallel? (I hope it is really that simple and I've just made another
> mountain out of a molehill, my specialty.)
> Q5: Assuming it works at all, is there a chance they will work without
> oil bath. I just don't see the necessity for oil since AL is bonded
> to poly
> (no air gaps there) and corona would have to jump either 11/16" inch
> of air
> around edge to avoid 3/16" poly or jump 7/16" thru holes to avoid the
> poly. Or is that what can happen by "surface effect" and the oil
> alleviate that??
> Q6: I got this material though scraps at a construction site. I need
> check pricing but wouldn't it be really easy to just buy a 4' x 8'
> sheet and
> rout off a 1/2" strip of the AL on both sides, place one electrode on
> side at opposite ends, get about .0085uF and call it finished?? A tad
> unwieldy but hey, I like the labor level......Of course you pole pig
> will need to stack a half dozen of these....
> Thanks for your time,
> Not to Scale
> Must be viewed with a fixed pitch font.
> Pos End Neg End
> ___ ___ ___
> _ | | _ _ | | _ _ | | _
> E1 |__|_||___||_|_____|_||___||_|_____|_||___||_|__|
> | || || | | || || | | || || |
> |C|| D ||C| |C|| D ||C| |C|| D ||C|
> |1|| 1 ||2| |3|| 2 ||4| |5|| 3 ||6|
> | || || | | || || | | || || |
> E2 |__|_||___||_|_____|_||___||_|_____|_||___||_|__|
> |_|| ||_| |_|| ||_| |_|| ||_|
> |___| |___| |___|