Re: Static Gaps vs Rotary Spark Gaps

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 08:54 AM 3/30/2005, you wrote:
> Original poster: "Medina, Benjamin (UMR-Student)" <bamxbb@xxxxxxx>
>
> Hello Folks. I originally was going for an ARSG (Asynchronous Rotary Spark 
> Gap) but got a lot of responses from the TCML saying that it's not 
> friendly with the NST, that it might fry it, and that I had to stay at 24o 
> BPS (at least) to be safe. Therefore, I've changed plans and am thinking 
> about using a SG (Static Gap).
>
> Using a 15kV/30mA NST, in terms of efficiency and performance, how does a 
> SG compare to a RSG? Is there any rule of thumb as to the # of gaps in 
> series? Does a RSG guarantee longer sparks vs. a SG?
>
> I am doing a school project, so we have budget and time constraints. Which 
> of the following Static Gaps setups would you suggest I should go with? Or 
> anything similar to images below. Bottom line, I want something that is 
> reliable, easy to build, and efficient. Gary Lau suggested, 
> http://www.hot-streamer.com/TeslaCoils/Misc/terrygap.jpg

The tradeoff is that there is a fixed voltage drop "per gap", so stringing 
together many small gaps has more loss than a single gap.  However, 
multiple gaps have better "quenching" performance (that is, when the 
voltage across the gap drops lower as the energy is transferred out of the 
primary into the secondary), the gap shuts off more consistently.



> Your comments and advice will be very much appreciated.
>
> Thanks again,
>
> Ben Medina
> Rolla, MO.
>
>
> http://hot-streamer.com/temp/BenMedina/f73d20a6.jpg
> (How is the connection done here? Essentially, where is the gap?)


The gaps are between the tubes.  You hook the wires to the end tubes of the 
set)



> http://hot-streamer.com/temp/BenMedina/f73d20b5.jpg
>
> (Maybe two parallel wood pieces. I am guessing I connect one end of the 
> screw/bolt to one end of the secondary side of the NST and the other end 
> of the other screw/bolt to the other end of the secondary side of the NST)?


You got it.  However, the bolt end gap has a lot of practical problems. The 
end of the bolt gets real hot, real fast, and that leads to bad gap 
performance.  A bolt gap with compressed air blowing through it (at fairly 
high speeds) will alleviate some of these issues.  I've had very, very poor 
luck with simple unblown bolt gaps.  They're finicky,  seem to change 
performance from second to second, etc.  If you have an air compressor that 
can blow a stream of air through the gap, it can work better.

The RQ/TCBOR gap in your first picture has the advantage of a large 
electrode area over which the sparks form, being made of copper (a good 
thermal conductor) and lots of heat sink area. This leads to stable 
performance.