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Re: Advanced Spark Gap Technology



The air flow meter that I borrowed from work shows the air flow stays about
the same from 3" down to about 1.75" then becomes slightly less as the
funnel gets smaller.  There must be some air slip back threw the fan blades
caused by the back pressure.  A box fan probably isn't very efficients any
way.  A box fan has a lot of area like the center hub of the fan blade and
the square case that doesn't produce any air flow.

Fan blade measures 4.375" diameter................Area = 15.0253"

The fan blade hub measures 2.062" diameter........Area = 3.3377"

The fan blade area = 15.0253 - 3.3377 = 11.6876"

My box fan measures 4.6875" square................Area = 21.9726

A funnel opening of 3.41" has an area of 11.6876"  

I folded 2 sheets of paper in half and cut one end 4.6875 wide and the other
end is 2" wide.  I taped the 2 sheets of paper together to get a square
funnel 4.68 at one end and 2" at the other end.  I taped the funnel to the
box fan and taped the spark gap to the other end of the funnel.  It was a
mickey mouse type construction but it was only an experement.

The hardest part was getting the copper plates flat.  Don't use copper
unless they are thicker than what I used. About .062" thick minumim would be
nice.  I think .062" aluminum plates cut out with a bandsaw will be much
easier to work with.

The poly washers were a little difficult to make too.  I had 2 paper punches
and neither one would punch a clean hole in .006 mil poly.  I discovered if
I punched a hole in 4 sheets of poly I could get 3 good washers the other
washer would be worthless.  I sharpened the end of a tiny pieces of tubing
rasor sharp on the sander and used it to bunch the screw hole in the center
of the washers.

Today I was thinking about washers and remember the RED FLAT washers that
come with a computer Mother Board.  Those tiny red washers look like they
would work great for spacers if I could figure out where to buy 40 of them.
I called a computer store and they said they would give me 3 or 4 of those
washers but not 40.

I was running only 750 watts on this experement.  I did several short runs 1
minute to 3 minutes for about 20 minutes.  If the power is increased you
might have a problem with heat just like you do with an RQ gap.

Gary Weaver






At 01:49 PM 2/4/00 -0700, you wrote:
>Original Poster: Dan Kline <ntesla-at-ntesla.csd.sc.edu> 
>
>At 10:32 PM 2/3/00 -0700, you wrote:
>>Original Poster: gweaver <gweaver-at-earthlink-dot-net> 
>>
>>I have been experementing with spark gaps.  I made several paper funnels to
>>reduce the area of a box fan and increase the air velocity.  I reduced a 4"
>>box fan down to 3", 2", 1.75", 1.5" and I checked the air velocity with the
>>air flow meter that I borrowed from work.  
>
>Which one worked the best?
>
>>I built a spark gap using 10 flat copper plates 2" x 2" each.  The copper
>>plates are made from roofing flashing from the lumber yard.  I cut the
>>plates with tin snips and filed the edges smooth.   I clamped all the plates
>>together in a stack and drilled a .150 diameter hole threw the entire stack
>>of plates in each corner.  4 places.
>>
>>I flattened each copper plate by placing it between 2 blocks of steel 1"
>>thick 2" square and hitting it with a 2 pound hammer.  
>>
>>I used 2 paper punches to punch out some .006 mil polyethylene flat washers
>>with a .150 diameter hole in the center.  4 washers in a stack gives me a
>>.024 space between each plate.  I put spacers on all 4 corners. Its all held
>>together with 4 plastic screws with plastic hex nuts on each corner.
>>
>>The finished spark gap is about 1/2" thick 2" square with a wire soldered on
>>each outside plate.  The spark gap is taped to the end of a paper funnel and
>>the funnel is taped to the end of a box fan.  
>>
>>I ran this for about 20 minutes on a 750 watt coil and it works better than
>>my RQ gap with the same box fan.  The flat copper plates act like a radiator
>>and keep the spark gap cool.  The air tends to blow most of the sparks to
>>the back half of copper plates.
>>
>>Its small, compact and easy to build.  I think it would be easier to build
>>if the plates were made out of thicker metal so they won't need to be
>>flattened.  Some 1/16" aluminum plates will probably work fine.  Wires can
>>be attached to stake on terminals and put under the head of the plactic
>>screw on one plate and another terminal under the hex nut on the other plate.
>
>I've thought about building gaps like this a lot, especially after reading
>old articles about building quenched gaps and stuff like that, but I never
>could think of a spacer that wouldn't end up either conducting, getting a
>carbon track, or breaking from heat-stress. The old designs used mica as
>the spacer. But shoot, even if it *did* track, it would be so easy to fix...:)
>I think I'll give this a shot. Could you describe the fan/funnel/gap setup
>a little more?
>Thanks,
>Dan
>
>>Gary Weaver
>
>
>
>
>