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Dusty archives


From: 	Larry Robertson[SMTP:LWRobertson-at-msn-dot-com]
Sent: 	Friday, June 20, 1997 5:53 PM
To: 	Tesla Builders
Subject: 	Dusty archives

Hi ...
	Several times I've seen the advice "Go look in the
archives", and yet much as I hate to admit it I still don't
know how to do this. Possibly some instructions for myself 
and the other newcomers would keep repetitive questions
down a little.

	Baby is holding up well. Although it is a little less
capacitance (.018 vs. .022) spark seems good. We have 
2 feet of hot blue to ground, and maybe 3 feet of steamers
so far.

If I open up the crude static gap I'm using - consisting of 
five pieces of 5/16 removable chain links end to end 
strapped onto a piece of PVC pipe - the cap gap starts
going off at about 30% on the variac. It is set to 7/8 of
an inch, which implies the voltage across the cap must be
on the order of 70 kV. This produces the longest strike 
to ground. A smaller gap with higher power - producing
a higher rep rate - makes longer streamers with nice
banjoing effects. It is evident I have to get a better gap.

It is also evident why my first two caps failed, with this 
much resonant rise.

The plastic parts for a rotary gap finally came in. It was of
course designed before the nxm gap advice posted here,
but may still work out ok. I started with a cheap bench grinder
on sale at Post Tool, thinking that would make it easy to
mount rotating disks. On the 9 inch X 3/4 inch rotating part
I have four equally spaced 1/2-13 bolts with acorn nuts on the
spark end, all connected together. The stationary side
has six similar bolts connected as two groups of three,
which are the HV connections. I thought one advantage of
this configuration is that the electrodes present in an 
alternate fashion i.e.. on the rotating side, 1 and 3 fire
then 2 and 4. The stationary side sequences 1&4, 3&6,
and 2&5; thus I surmised giving more time for cooling. Also it
gives 12 presentations per revolution, which with an 1800
RPM motor produces 480 pps. Also saves several bolts.

This can be scaled up - I calculated  pps = (nXm) / 2 , where
n and m have no common factors except 2. So for
instance 6 electrodes on one and 10 on the other
would produce 30 pps. and save a whole bunch of bolts.

As pointed out here though, one would have to keep an
eye on the dwell time.

So we may get time this weekend to give it a try. 

So it goes in the wilds of Morgan Hill.

LR