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Per Niva's spark gap


From: 	Per Niva[SMTP:pna-at-pp.gellivare.se]
Sent: 	Tuesday, August 26, 1997 7:21 AM
To: 	Tesla List
Subject: 	Per Niva's spark gap

Hi, hi

Here are some more posts to the usa-tesla list, on
current state of things over here. I'll repost them to 
this list and hope there will be more interested people here.



> I just got back from the HV lab for the evening.
> Todays work have included driving down the ground rods and
> connecting them, building the primary coil and trying to prepare
> the 4" PVC pipe for the secondary. Closing in on the precious 
> sparks, but I don't think baking the PVC pipe in the oven was 
> such a great idea... At least the way I did it. Fortunately 
> enough did I manage to stop the process before bad things started 
> to happen. No harm to the oven, and it's not used for cooking 
> food anyway. I guess I'll go for the 3" PE pipe to start with.
> 
> The question about main spark gap remains, though. My current plan
> is to use a series static gap with 4 single gaps. The two options
> for electrodes currently at hand is 1) bolts with big, round heads.
> They're called "wagon bolts" in Swedish at least. These bolts look
> something like this: -|--)
>                       ^  ^
>                     nut  head
> 
> The head is maybe 3/4" in dia, and the thread is 5/16".
> I'd arrange the bolts in a row, with the gap distance adjustible
> by screwing the bolts in and out of the nuts, which would be welded
> to some metal base. 
> 
> Ascii art:    --|-) (-|-- --|-) (-|-- --|-) (-|--
>            ======     =======     =======     ======
> 
> The other option for electrodes would be brass nuts used for
> keeping IKEA assemble-your-self-furniture together. They look like 
> this: (side view, enlarged, actual size around 1/2" dia)
> 
> flat brass washer ->    |
>                         |---~~~~ 
> hexagonal hole here ->            <- threaded end
>                         |---~~~~
>                         |
> 
> These would be arranged in the same way as the "wagon bolts".
> With the IKEA nuts I'd get flat faces in the gaps, but with
> a hexagonal hole in the middle. With the "wagon bolts" I'd
> get spherical faces. Which is to prefer? Maybe it doesn't 
> matter, since they'll only handle some 800 watts (for now...)
> 
> 
> 
> Does anyone out there read this? Do you care about my plans?
> It seems like most people rather discuss something else than
> coiling... If no one cares, I won't waste your time with
> irrelevant, tesla coil-concerning posts... (flames go to 
> /dev/null.)
> 
> 
> Be hearing you (?),
> 
> Per
> 
> 
> ====================================
> This darn sig block is still missing


Malcom Watts replied:

MW> The first option. Sharp edges are a no-no anywhere in high 
MW> voltage devices. Corona bleed is the worst enemy of MV's.


I replied:

> Yes, I think so too. Sharp edges or corners seems to be bad 
> when dealing with HV. They act as a starting point for thowing 
> off sparks or corona. The IKEA nuts was never really an option 
> anyway, a friend gave them to me and thought they looked 
> usable. I didn't. Fun hearing other people's opinions though.


And I posted again:

> Hello, hello
> 
> The spark gap is ready! (For now, that is.)
> 
> I went for the wagon bolts, but modified the setup slightly.
> Instead of connecting them in a long row, as I described
> earlier, I put them in a plastic pipe, like this:
> 
>        (top view)
> 
>         |      |
>         |      |
>      --||--)(--||--   <- one "end" connection
>      |  |      |
>      --||--)(--||--
>         |      |  |   <- bars to connect the gaps in series
>      --||--)(--||--
>      |  |      |
>      --||--)(--||--   <- other "end" connection
>         |      |
>         |      |
> 
>         ^      ^
>        pipe walls
> 
> 
>         /------\
>         |      |
>      --||--)(--||--
>         |      |
>         \------/
> 
>         end view
> 
> 
> Through this pipe I run air blown by a old hoover. The
> pipe is some 2 1/2" inner dia. Is that enough CFM to do 
> anything good?
> 
> With this design I get several Good Things:
> * Ease to build...
> * Connects easily to the air supply
> * Shielding from the UV light
> 
> At the down side:
> * Many corners and edges to let off corona
> * A bit difficult to adjust the gap length
> * Possible dimensional stability problems with the
>   plastic pipe, due to heat?
> 
> 
> Any comments appreciated,
> 
> Per
> 
> 
> ----------------------------------------------------
> pna-at-pp.gellivare.se                 +46 (0)970 20976
> "Beware - the world will never be the same again..."
>