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Re: [TCML] G-10 blistering
Hi Jeff,
Thanks for the comments. Actually, its the flying electrodes that
scorcherd their mounting surface of the G-10 disc. The stationary
electrodes are the ones that are set in the brass blocks. The brass
block "holders" are mounted to a 3/8" thick lexan base. Yes the
stationary electrodes and their brass mounting blocks do get quite
hot as well but so far, the lexan mounting has showed no signs of
heat damage. I don't think any of my electrodes (flying or stationary)
have gotten hot enough to exhibit visible in candescence yet, though.
I don't possess the skills or the equipment to machine finned heat sinks
and I had to break down and have my G-10 rotary disc machined by
a "professional" to the tune of about $200!
David Rieben
----- Original Message -----
From: "Jeff Behary" <electrotherapy@xxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Thursday, June 12, 2008 9:06 PM
Subject: RE: [TCML] G-10 blistering
Hey Dave,
I've had that happen too with a stationary spark gap, sickening when you
consider the price of G10...(and even worse to think of remachining a piece
of the stuff - I itch for days after...)
http://www.electrotherapymuseum.com/Forgotten_Tesla_Technologies/Magnifier_Pancake_System/images/G10-6-Series_Spark_Gap.jpg
shows a similar setup, but at the time I was only using a pair of gaps -
stationary.
I was running a few experiments with 480V - 1kV at 2-4 amps, with each gap
only .001" or so and very small capacitors (.01 and less). The spark gap
got scorching hot, and a few times the tungsten contacts actually turned
red, which changed to black when they cooled. The outer layer of G10
blackened and blistered behind the heatsink.
Have you thought of using finned aluminum for the heat sinks? It doesn't
look as nice as brass, but it dissipates the heat a lot better.
The heatsinks above were made from 1.25" 6061/T6 and were also about 2.5"
long.
Nice video!
Jeff
From: drieben@xxxxxxxxxxx> To: tesla@xxxxxxxxxx> Date: Thu, 12 Jun 2008
19:22:33 -0500> CC: > Subject: [TCML] G-10 blistering> > HI all,> > I
figure the answer is that I am just pushing a bit too much> power for the
size of the flying electrodes of my ARSG of> my Green Monster Tesla coil,
but I am going to go ahead> and share my experience with the list. I
recently upgraded> my Green Monster coil's ARSG to 2 pair of stationary
elec-> trodes spaced 180 apart on each side of the rotary disc > instead
of a single pair of stationary electrodes. The reason> for adding a second
pair of stationary electrodes is that I> was getting deminished quenching
at power levels over> about 60 amps draw that was apparent with flaming
"pop-> ping" yellowish plasma at the ARSG spark along with some->
accompanying erratic spark output and spikes in the current> draw,
according to the panel ammeter. Adding the second> set of stationary
electrodes made for a marked improvement > in this and I am now able to
run at up to 90 amps input > (at 240 volts) continuously without a hitch.
However, I noticed > a strange "hot melted pastic" like odor after the
last long> run at a solid 90 amps input when I got close to the tank cir->
cuit assembly after powering it down. I couldn't figure out > exactly what
was causing the odor at that time but a closer> examination a couple of
weeks later revealed that the G-10 > disc had actually scorched and
blistered a bit around each> of the (8) 3/8" x 1.5" long solid tungsten
flying electrodes.> I supposed that sustained 90 amp runs are just taxing
the> thermal dissipational characteristics of my ARSG componenets> to
their limits? Also, I believe the addition of the extra pair of>
stationary electrodes has increased the thermal load > on the flying
electrodes since they are now "sparking" twice with > each disc revolution
instead of once. BTW, the (4) stationary > electrodes are each 1/2" x 3"
long solid tungsten rods set in > 1.25" x 2.5" long brass square stock. I
suppose I'll have to up-> grade to more massive flying electrodes if I
wish to run at 90> amp long runs on a regular basis. Other than the
excessive flying> electrode heat, which are whirling at over 3000 RPM, the
coil> is running great ;^)) Here is short video clip of it > running
BEFORE the ARSG modifications:> http://youtube.com/watch?v=eWZD3M-nye8> It
runs notably smoother now without any racing sparks> and at even higher
power levels than I was able to run> for this clip. Will the flying
eledtrodes eventually burn their> way out of the G-10 disc since they
actually got hot enough> to scorch the epoxy bonding agent of the G-10?
Comments > from others with high powered coil experience is welcomed....
:^)> > David Rieben> _______________________________________________>
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