RE: AMRAD Spark Gaps

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

Original poster: "Oxandale, Terry by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Toxandale-at-SPP-dot-org>

I'm not an industrial engineer, but I can hold my own in a mechanical
environment. When I built this (and I may have stated this earlier)
device, other than gasket problems (which were a concern even before I
built it but I was just using what I had on hand to see if it would
work), the only other problem was the uneven expansion of the discs
during the warm-up (initial arc time). the arcing side of each disc
would get hotter than the opposite (non-arcing) side, and thus this
uneven expansion closed the gap somewhat. Now multiply this times the
number of gaps, and you could have a significant problem with many gaps
(which is why I think mine worked best at about 5 to 6 gaps). Intuition
tells me that if we make the center arcing surface too large in area,
that this expansion problem will be exacerbated. I don't know if a
thinner disc would curve less than a thick disc would (due to the
temperature evening out quickly). Ideally you would want to use a single
disc that is symmetrically convex (like a lens) or like two hats put
together at the brim. This way, arcing would occur on both sides of the
disc, but in my case, this entailed machining that I did not have
available to me at the time. This is a most resourceful bunch of folks
on this list so I know somebody is going to come up with even better
ideas (other than a lot of elbow grease and grit like we used to do to
make telescope lenses)

Terry Oxandale
> ----------
> From: 	Tesla list[SMTP:tesla-at-pupman-dot-com]
> Sent: 	Friday, December 29, 2000 9:14 PM
> To: 	tesla-at-pupman-dot-com
> Subject: 	Re: AMRAD Spark Gaps
> 
> Original poster: "bob golding by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <yubba-at-clara-dot-net>
> 
> > Hi All,
> 
> >    I have been putting some thought into how to make an accurate
> amrad
> type gap and have come to the
> > conclusion that the best way would be to stamp out the pieces on a
> fly
> press. This would involve
> > making a die. I have been talking to a friend with a lathe milling
> machine and a fly press. He looked
> > at my drawings and said if I go round and instruct him on what we
> want
> ,and provide the materials he
> > is quite happy to turn up a die for us. The materials are no
> problem, the
> time is my own and I can
> > always get copper from the scrap yard. So if we are going to do this
> I
> need to know what dimensions
> > we should go for. I thought 2" copper pipe spit down one side would
> be a
> good start. There is always
> > lots of this ,and it is new so no cleaning to worry about. It is
> also
> easy to cut into short lengths
> > with a pipe cutter. This will give us a 5" x 5" square and  about 1
> mm
> thick. Of course I will grab
> > any sheet I find. as my friend has a small guillotine.  What
> diameter
> indent should we go for?. If
> > anyone has any ideas let me know. Still have to work out the gaskets
> but
> if we start with something
> > pretty flat is should help. I like terry's design, as this makes it
> simple  to make the blanks, and
> > if it is enclosed in a sealed box one could put a fan on the end for
> cooling. If anyone else wants to
> > experiment let me know and I will send  them some blanks at copper
> scrap
> prices plus postage.
> > (Currently around £1.25 (about one dollar) a kilo) to experiment
> with. If
> it all ends in tears you
> > could always use them for coasters.
> 
> cheers
> bob golding
> 
> >
> 
> >
> > > > So they did.  And so did I when I built mine.  A real pain.
> > > > A right royal major pain.  Mine started out as two inch
> > > > diameter disks 1/16 inch thick.  With an 80 tooth-per-inch
> > > > piercing saw I converted them to washers.  With a sheet of
> > > > sandpaper stapled to a piece of wood I sanded them down to
> > > > around 1 - 1,1mm thin.  Lost some fingerprints and blood in
> > > > the process.  With my Unimat 3 and a grindstone I got them
> > > > very nearly flat and parallel.  I started with 40 disks.  I
> > > > got 15 or so washers.  I smeared silicone high vacuum grease
> > > > (stable to over 200C) on them to seal them against the gaps.
> > > >
> > > > They *still* leak ;-)
> > > >
> > > > Webpage coming "real soon now" but probably not this year
> > > > :-)
> > > >
> > > > Dunckx
> > >
> > >
> > >
> > >
> 
> 
>