Hey Robert...
wonderful idea but not the proper material... probably conductive to
boot....
the disc is brittle and designed to wear away as it is used. Ergo, the
material is not homogenious ( actually the grit is held together with
an epoxy) and very prone to shattering in the wrong application.
When designing a rotory spark gap, you NEED a material that is either
homogenious ( solid metal, etc. :) ) or a cross fiber patterned
laminated material ( G-10 is a popular choice). When you put several
ounces of tungsten into the periphery of a rotating disc and spin it
up to or past 1800 rpm, the electrodes can produce in excess of 5+ G's
with no problem. Can you say bullet? ;)
Another consideration to ponder is the amount of heat that can be
transfered to the disc via the electrodes. Since heat can be a
problem, this leaves out using plastics that can become soft at less
than 400 degrees F ( which is most of them).
There are about 3 general designs for rotory gaps
1. 1/4 - 1/2" thick, 8 - 10+" dia. disc with electrodes approximately
1/2- 3/4" from edge ( G-10 being the popular choice) Pole piggie usage.
2. propeller gap, basically an insulative hub holding a "lengthy" ( 8"
or so) piece of tungsten rod ( hub being UHMW PE) normally used in NST
applications.
3. a work of art, the gap used in the China Olymics Tesla coil (
probably cost as much as a small pick up truck).
When designing for Tesla coils, there are a few things to remember
Primary voltages can be from 5KV to 30 KV, insulation is a prime
factor ( especially after 25KV)
Secondary voltages can range from 50ish thousand volts to 1.5+ million
volts ( not much can insulate against that... think lightning)
Spark gaps create plazma... I dont know of much that can resist the
errosive effects it can produce... but tungsten does seem to hold its
ground to a degree...
Browse the active websites, see what is normally used... its been
tested and most likely works most of the time. There are exotic
materials out there that can be substituted, but the cost factor is
the determining point of implementation.
Alot of great ideas come from the "What if" attitude... it gets
people thinking and wondering....
Scot D
Robert Davies wrote:
WOW!!!
http://tesladownunder.com/
I was at Lowes yesterday and I was looking at a 7 1/2 angle grinder
disc, it has a threaded center and can handle high rpm. Has anyone
used this type of material for a spark gap?
http://www.lowes.com/lowes/lkn?action=productDetail&productId=22836-70-DW4999&lpage=none
<http://www.lowes.com/lowes/lkn?action=productDetail&productId=22836-70-DW4999&lpage=none>
Rob
KI4HXT
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