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Re: CONCERTINA CAP



Original poster: "Phil Parry by way of Terry Fritz <teslalist-at-qwest-dot-net>" <ryukin-at-ntlworld-dot-com>

Hi Ian,

 > First of all hello everybody, this is my first correspondence to the
'list'.
 > I am in the process of building my first coil (4 1/2") and after searching
the
 > W.ibbly W.obbly W.ay I discovered this fantastic information resource. I
was
 > amazed to see so many 'insane' people out there with the same inexplicable
 > fascination with electrical discharges. Perhaps I'm not that mad after
all?

There are more of us than you think!  We UK coilers have our own group and
website (www.tcbouk-dot-org.uk) - there is a Teslathon planned in the Nottingham
area late August/early September and another in Cambridge in October (exact
dates TBC) if you don't mind the trip and want to meet other coilers/show
off your stuff!

 > Anyway I'll get to the point. With respect to rolled caps having self
 > inductance
 > and long discharge paths, I was wondering about folding i.e. a concertina
cap.
 > I know that the effective capacitance would be half that of a roll for a
 > given length of material, but the discharge path would be very short and
 > very low
 > resistance (one could run the bus-bars right along the exposed ends or
loops.
 > The reason behind my thinking is as follows. I work as a buyer for a
roofing
 > company and we carry large quantities of self adhesive allu. flashing and
 > rolls
 > of thick (up to 2mm), poly roofing membrane, p.v.c. pipes of all diameters
 > etc. so my plan was to burnish down the allu flashing to the poly membrane
 > excluding all the air. Then when folded the only place air can be trapped
is
 > between plates of the same polarity. Why not just build a stacked plate
 > cap? I hear
 > you cry, well.....I am I just thought this would reduce production time
and
 > make it easier to exclude air. It's just a thought.
 > Any comments anyone?

I don't foresee any huge problems as long as you oil-fill the cap to prevent
corona from the folds and edges, but others on the list can probably give
better advice.  Most people have abandoned homebrew caps in favour of MMC's
now though.

 > Also I don't seem to be able to find any detailed info on d.c. resonant
 > charging or magnifier coils

www.richieburnett.co.uk has some excellent info on DC charging.

 > and I'm struggling to find a suitable
 > transformer as
 > nst's are limited by law in the u.k. to 10kV -at- 60mA and also have internal
 > trip
 > switches for earth leakage and or short circuit (or so I'm told by
somebody in
 > the industry)

That explains the problems I've had finding decent NST's :)  Thanks for the
info - I didn't know that.  Im concentrating on valve coils (VTTC's) at the
moment so MOT's and radio transformers are more my thing.

 >, pole pigs are very rare. (except those 33kV jobs that weigh as
 > much as a car and cost as much as a house!) I know I can series two mot's
but
 > that's still only 4kV.

You can use voltage doublers/quadruplers on a MOT stack for more voltage.
Steve Conner's 3.5" coil (www.scopeboy-dot-com/tesla) uses a 10kV DC supply from
a single MOT - I saw this in action at the Derby Teslathon a few weeks ago
and it was very impressive for its size.

Welcome to coiling - hope to see you at a Teslathon sometime!

Cheers
Phil