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Re: TC physical construction



Hello Jim:

  I would find a Physical construction discussion of interest too, 
so here goes.  I am at the point in my coil efforts where I am now 
mounting the various components.  Any comments from the group would 
always be helpful and I'm sure many of us will learn from others 
past experiences.  Here's what I am trying to do.

I made my primary on a plywood sheet that is lifted 18" above a 
second sheet which is on casters.  The plan at present is to place 
the rotary sparkgap and Condenser Products capacitor on this lower 
shelf.  The capacitor will rest in a cradle about 10" off the 
lowere plywood sheet.  Prior to mounting the primary, I sanded, 
primed and painted all of the wood to insure it didn't accumulate 
alot of moisture during the summer around here.  The next step was 
to layout the nylon stand-off strips and cut a series of openings 
in the top plywood sheet.  I've seen several different shots where 
the primary movable tap came from underneath and then stretched 
around the outside to the final resonant connection point.  At the 
same time, my current understanding is there is a benefit to the 
system Q if all leads are kept short and straight runs, using tubing 
or flat strap.  Well, right or wrong, with those pieces of 
information in my head, I chose to cut four slots 2" wide and 10" 
long every 90 degrees in order to provide as straight a shot up to 
the correct point for resonance.  This will make it easy to keep 
that lead as short as possible.  I also cut two 2" diameter holes 
near the base of the secondary.  The first is for the ground lead 
for the secondary and the second is for the primary inner end.  I've 
taken this inner end of the primary and radiused/formed it down 
through this hole and it extends about 8" below the top sheet of 
plywood.  I am planning on cutting it to the correct length and then 
connecting the end of the cap to it, using a chunk of 1" wide 20 ga. 
copper sheet.  The other end of the cap will go to the sparkgap 
which will be across the incoming H.V. (keep reading, I'll make the 
final point soon!)  The second end of the sparkgap and the second 
H.V. lead will actually become the point that runs up to the tap 
point on the primary.  The cap and sparkgap will be rotatable around 
the system base so that I can position them at the correct point to 
access one of the four cutout gaps in the top sheet of plywood, in 
order to keep that tap lead as short as possible.  Hope that makes 
sense.  

I am expecting the strike rail to absorb most of the hits, but I 
really don't know.  I have some 1/8" sheet acrylic that I have as a 
safety idea---if I start getting hits straight through the primary 
down to the sparkgap and/or the cap, would a sheet of acrylic above 
the primary help?  Maybe pie slice shaped chunks just beneath the 
primary in-between the four nylon primary supports? Gee, I gotta use 
that 1/8" sheet of acrylic for something!  

The last point that I am trying to get a grip on is where to 
physically locate the chokes and bypass caps in the high voltage 
leg(using RG-213).  I wonder if placing them right under the coil 
system or back by the transformer itself is better.  Setting it out 
by the transformer, in my mind requires an additional enclosure of 
some sort for safety reasons.  Putting it under the primary in my 
"structure" keeps it in an area that is already going to be 
considered very deadly and not approachable until certain steps are 
completed. I really don't know if one is better than the other, or 
if a "where ever it will fit" is O.K.

I got an old Hoffman electrical enclosure with a disconnect switch 
in it that I am using for the metering and two autotransformers- one 
for the Cater motor on the gap and the other for the H.V. system.  
My wife is already asking how long that thing is going to be laying 
around--Oh, well-------I've got the coil structure itself in our new 
basement family room, aren't hose made for coil projects?  That 
caused some discussion too.

This represents my longest run of incoherent babble to date--any 
comments will be apreciated!

Chuck Curran