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Re: Scot's FSG --Abbreviations but no acronyms
Tesla List wrote:
>
> Original Poster: Parpp807-at-aol-dot-com
>
> Hi all,
> I have completed a very nice version of Scot D's fixed spark gap.
>
> The FSG consists of nine 1.5 inch diam Cu sweat couplings sandwiched between
> two
> 4 x 12 inch pcs of G-10. The G-10 was cut on a bandsaw using a new, metal-
> cutting blade. The cutting was easy. I rigged the shop vacuum cleaner to
> suck-up the
> dust as the cuts were made. The blade is no longer new. :-((
>
> The layout for the hole drilling is crucial if the copper cylinders are going
> to lineup
> properly to give an accurate and adjustable gap. Using zirconium nitride
> drills, I drilled
> the two slabs of G-10 exactly alike by wrapping the two slabs with duct tape,
> carefully
> centerpunching all nine holes, and drilling both slabs at the same time for
> the nine
> 8-32 screws plus the six 1/4-20 threaded brass support rods. This means that
> the bottom
> piece of G-10 has five cylinders and four dummy holes, while the top slab
> holds the four
> cylinders with five dummy holes. I put screws in the blank holes. I drilled
> the holes in two or three steps rather than ruining the drill by boring thru
> in one hit.
>
> I did the layout directly on the duct tape. The nine holes must be located
> along a centerline
> and spaced exactly 0.75 inches apart so that there is a spacing of 1.5
> diameters for
> each cylinder. The first of five cylinders mounts to the first hole, the
> second of five cylinders
> mounts to the third hole....and so on. On the other slab of G-10 the first of
> the four cylinders mounts to the second hole, the second of the four
> cylinders mounts to the fourth hole....and so on.
>
> My major change in Scot's design is not milling the G-10 for parallel ditches
> to hold
> the cylinders parallel. The cylinders are held solidly in place with the 8-32
> screw, a nut
> and a lockwasher. In addition to eliminating the need to mill out the
> ditches, I think this
> method gives better accuracy and the parallelism can be easily set using a
> gauge or
> shims. Also, I think the engineering is better because you do not remove
> almost
> 50% of the G-10 from right under the cylinder where you need the mass to
> carry the
> heat load. Another minor change in Scot's design is I added two additional
> 1/4 x 20 support rods in the center of the long sides of the slab. They help
> in the final lockup.
>
> The finishing touch is four pieces of 3/4-inch Lucite rod, drilled and tapped
> to
> fit the bottom of the corner rods to serve as insulated mounting feet. The
> overall
> appearance is impressive if you're impressed by spark gaps. :-))
>
> Disclaimer: All the abbreviations in this posting are abbreviations.
> They are not acronyms. :-))
>
> Happy day,
> Ralph Zekelman
Hi Ralph...
Sounds like you did a wonderful job if you get a chance I'd love to
see a picture of it ....
another little touch that i added to mine was the 1/4-20 bolts that hold
the 2 plates apart.... when i finally got the gap set to the proper
distance, I placed a second set of nuts on the "inside" section of the
plates to act as a locknut assembly... so when i need to clean the gap
set all I have to do is remove the top nuts... take the top plate off
and clean the gaps ... when its time to replace the top section ... the
double nut lock assembly is already preset for the best distance ..
just slide on the top plate and replace the last set of nuts and tighten
them down no fuss no muss just plug it in and you are up n
runnin... :)
Scot D