Re: Brass Ball static spark gap not doing so well

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Tesla729-at-cs-dot-com>

In a message dated 5/27/01 2:24:39 PM Central Daylight Time, tesla-at-pupman-dot-com 
writes: 


>
> I want to piggyback on what Deano said.  I've also had 
> bad pitting problems with brass, so I dumped it in 
> favor of copper, which seems much more durable. 
> However, I did use 1/4" treaded brass rod for my 
> Asynch RSG, and it worked out pretty well. The brass 
> still evaporates away, but the rod is too small 
> diameter to exhibit any pitting.  Instead, the entire 
> rod tip slowly eats away.  When the gap finally gets 
> too wide due to erosion, I simply re-gap, and I'm good 
> to go for a few more weeks.  This is just for the 
> fixed electrodes.  I've never had to service the 
> flying electrodes, which are made of the same brass 
> rod material. 
>
> Greg 
> http://hot-streamer-dot-com/greg 



Hi Greg, all, 

I have had pretty much the same experience with threaded brass 
rod electrodes. With my 10 kVA pig driven system, I use 1/2" dia 
threaded brass rod for the stationary electrodes and 3/8" dia 
threaded brass rods for the flying electrodes (asynch -at- ~ 300 bps) 
With these larger diameter rods, erosion is quite minimal. BTW, 
there are twin rotary discs, each with 6 flying elctrodes, which are 
in series, so there are a total of 4 SGs. The one disadvantage of 
the larger flying electrodes is that -at- 3/8" X 2" long, plus two fitting 
SS nuts and wahers with each brass electrode, they are rather 
heavy and it takes the 1/3 HP, 3450 RPM bench grinder motor 
several seconds to bring the RSG up to operational speed after 
power up. 

Sparkin' in Memphis, 
David Rieben