RE: [TCML] G-10 blistering

[Jeff Behary <electrotherapy@xxxxxxxxxxx>]

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> _______________________________________________> Tesla mailing list> Tesla@xxxxxxxxxxxxxx> http://www.pupman.com/mailman/listinfo/tesla
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