Re: magnetically quenched gap "Director"

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "tcbfw by way of Terry Fritz <teslalist-at-qwest-dot-net>" <tcbfw-at-charter-dot-net>

Matthew,

Your my friend already . . . You quoted Spock !!!
answers interspersed in post

 > In the words of Mr Spock, "fascinating".  It begs a few questions:
 >
 > Do I get it right that, used as a spark gap (switching device), this is
 > effectively self quenching (as polarity reverses) ?

Yes, if your using fixed magnets it will self quench when the supply
polarity reverses, however you could also run your coil on DC then use
electromagnets and force the gap to quench by reversing the magnetic field.

 > I assume that these 'directors' would get hot with time/sufficient
 > power.  If this is so, to driving a large coil would need a more robust
 > device.  I was wondering about popping the tube into a water jacket -
would
 > the extra glass/water/air gap be of sufficiently low reluctance to cause a
 > problem?

You are correct, heat is not your friend. The size units in the pictures
will run that coil for only a few minutes if they are in open air as
pictured. So far we have had some luck cooling them in oil ( I know thats a
bad word ) The extra gap size can be componsated for by increasing the field
strenth and the low reluctance should only present a problem if you use
electromagnets and try reversing fields. - Our team goal now is to see if we
can build a gap that will run the Warthog (our large 13kw coil)

 > In one of the photographs, the tubes appear to be mounted in what looks
 > like the head magnet assembly of a 'vintage' full height hard drive; is
 > this the case?  It's just that I've got one in the shed, if I can prise it
 > off whatever it has stuck itself to ;-)

You have a keen eye for parts salvage, yes the metel block the T "Directors"
are being held in was from an old hard drive. My moto - If it can't be made
from someone elses trash, it ain't worth making.

 > For anyone considering trying to reproduce this - and living in a rural
 > area with no neon signs/neon sign shops - what sort of glass would be
 > recommended, of what should the elecrodes be made, and how to you get the
 > one to stick in the other without gas leaks?

Glass blowing is an art that as yet I haven't mastered, (Thanks again for
these tubes Bill) but in antisapation of a question just like this we have
had good results with blowing gas (we were using argon) through the tube at
a positive presure, once all the air was out of the tube and both electrodes
were bathed in argon (this also helped cool it) the tube opperated fine. A
tube like this has to be able to handle heat well, PVC pipe will not work.
Ceramic pipe work well (but it's hard to cut)

 > I've got a cylinder of MIG (C02/argon) in the shed - any good for this?

This is one mixture of gas we haven't yet tryed, but as it has argon in it -
it might work. (Anyone in Texas got a MIG welder I can borrow for a few
minutes?) - If I find some of this gas I'll let you know.

Thanks for your interest,
Phil
TCBFW