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Re: Static Air-blast gap.


From: 	NTesla[SMTP:ntesla-at-ntesla.csd.sc.edu]
Reply To: 	ntesla-at-ntesla.csd.sc.edu
Sent: 	Tuesday, September 02, 1997 11:21 AM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: Static Air-blast gap.

At 07:06 PM 8/27/97 -0500, you wrote:
>
>From: 	Per Niva[SMTP:pna-at-pp.gellivare.se]
>Sent: 	Wednesday, August 27, 1997 2:07 PM
>To: 	Tesla List
>Subject: 	Re: Static Air-blast gap.
>
>Phil Chalk wrote:
>
>> Now here's the new bit.  The fixed electrode would be drilled 
>> right through down its central axis - about a 1/4" dia. hole.  
>> Compressed air would be blown through this hole; it would hit 
>> the face of the movable electrode, then be forced to exit from 
>> the edges of the gap - hopefully fairly evenly.
>
>I had a similar idea, and asked about it on the usa-tesla list
>while this list was down.  The concern is, would the sharp edges
>of the hole in the electrode face alter the proberties of the
>gap?  Perhaps there would be corona leakage from the sharp edges,
>and the gap would fire easier than without the hole.
>This was also what other people seemed to think.
>Maybe one could round the sharp edges off?
>
>Otherwise it seems like a good idea to me (what that might
>be worth).

I have built that exact gap, using two 3" x 1" brass bars. I drilled 1/4"
holes 3/4 of the way down the center axis, and then drilled in from the
side to meet the end of the axial hole at its 2.25" depth. I threaded the
side hole and attached a 1/4" hose barb, which facilitated connection to an
air-compressor.
The key was the use a countersink to chamfer, bevel, or whatever you want
to call it, the top of the axial hole. This may also affect the shape of
the air-blast as it comes into the gap. (Spreading it some, I'm thinking,
which would be a good thing) I've used this gap with a small compressor
(actually, I have two of these gaps and run them in series), but I need
better airflow to get it to quench properly. However, to answer your
question, the residual carbonization/oxidation patterns in the faces of the
gap showed zero activity at the hole edges, because there aren't any
hole-edges, due to the countersink. ;)

Dan