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Re: Wood
Tesla List wrote:
>
> Original Poster: Alex Crow <user-at-alexcrow.clara-dot-net>
>
> Dear All
>
> I was looking through various posts about materials for SG boxes and
> Primary supports, and I noticed that many people have said that wood is
> a bad material for these purposes. However, I have used it very
> successfully in my coil in all HV areas and as yet it hasn't even got
> warm or displayed any kind of tracking. What I did was to soak every
> piece throroughly, several times, in transformer oil. I am using 8mm
> plywood for most of these bits, and I found it was quite absorbent.
> I allowed this to soak in for several days, at which point I liberally
> applied varnish. Due to some oil still oozing from the wood, it takes an
> age to dry (think in days here) but I found that once it had done so it
> set quite hard and the wood actually felt like plastic to the touch.
> I tested this with my NST output, even trying to induce tracking by
> using pins as electrodes and it didn't draw any current or spark. I
> think that the oil must have displaced the water (2% or so, I hear) that
> is common to most woods - the Xfrmr oil is very non-viscous and
> penetrating - I spilt some on the concrete and thought there would be a
> stain there forever, but in three or four days it had disappeared.
>
> Anyone else have any experience with using wood at HV successfully?
>
> Alex Crow
Your report is entirely reasonable, and your results are to be
expected. Wood is a pretty universal substance and, if dry, a good
insulator. The traditional way of preparing wood is/was to boil it in
paraffin was to evaporate the moisture and then let it cool a bit, so
that the wax is "sucked" into the voids in the wood. If done right
produces a neat job, and the end product is easy to machine.
Ed