[Prev][Next][Index][Thread]

Book review and coil update


Hi to all, 

Well another big Tesla weekend. I received the "Tesla coil
Builders Guide to the Colorado Springs Notes" on Thursday, and I
have nearly finished it. This book is an absolute goldmine.
Richard Quick has reviewed it in the Tesla References, but I will
add my own 2 cents(pence). It is a day by day explanation of what
Tesla did at CS. Richard Hull, the author explains Teslas
activities clearly and concisely, and also dispels a few myths
such as claims that Tesla produced 135 foot long lightning bolts
at CS. 
 The book is written from the perspective of the coil builder,
and particularly the magnifier coil builder (not many of those to
the pound I'll warrant) This is where the book really scores for
me. Mr. Hull explains the principle of operation and the circuit
parameters required for magnifiers or "extra coils" and notes the
increased efficiency over the classic coil system. This increase
in efficiency is clearly shown in the magnificent B&W photos in
the appendix. These are just brilliant and show what the coil
builder can achieve in terms of spark length with quite limited
power input. Streamers of up to 7 times the length of the extra
coil are produced. Magnifiers are most certainly where its at for
max spark lengths. 
  Mr. Hull's enthusiasm for his work is evident, with liberal
sprinklings of exclamation marks and a smattering of irony in
places. Historical background information is provided, but the
main body of the work is concerned with the technicalities of
Tesla's research at CS. I would highly recommend this book to any
Tesla freak, it is up there with "Nikola Tesla and his work...."
in a list of must haves. I got the book from the inter library
loan service in the UK and it looks like I am only the second
person in England to have read it :-)

  Well on to my own "research". Following the tips from the
usa-tesla massive last month on my coil, I have slightly changed
the configuration, i.e. gap now across HV trans. instead of cap.
Cap is now a single 0.004 mfd mica cap rated at 20 amps and
20kvac. This baby is as close to the primary as poss, it's
mounted underneath the 1/2" perspex plate that supports the
primary. 
  The HV trans knocks out 25KVAC so I can only turn it up to 50%
on the variac to spare my cap. I'm very scared of blowing it up
as its made of ceramic, also 20kv 20A caps are like rocking horse
sh*t to get hold of as I'm sure you know.
  The filter circuit has also been modified. I now have 2 in line
chokes. These are 1/2" ferrite rods wound with approx 40 turns of
1mm enammeled copper wire, sealed with polyurethane varnish and
wrapped in self amalgamating rubber tape. These are in series
with each HV line which then goes to two 500pF 30Kv caps mounted
on the RF ground spark gap shield. Safety gap consists of stiff
copper wire from the top of each cap going to about 1/4" from the
spark gap shield. Tank circuit wiring is 4mm diameter copper pipe
with serious crimped connectors. 
  Primary as mentioned before is 22 turns of copper tape in an
inverted cone stylee, secondary about 1150 turns of 0.4mm wire on
a 4" perspex former. Toroid is stainless steel 12 x 3". 
 I have three Spark Gaps in series, two of which are 1" diameter
carbon rods and 1 of which is 1" diameter brass rod. I measured
the DC resistance of the carbon rods at less than 1 ohm.


Enough already. Fired it up, gaps too wide, adjusted gaps to a
total distance of roughly 7mm and fired again at a tapping of
about 17 turns. Approximately 5" spark :-( Anyway the final max
tapping was *20 TURNS* This seems pretty big compared to the
normal 8-12 turns quoted on this list. I assume this is due to my
relatively small primary cap. I wanted to try a more accurate
tune but I was unable to see the spark properly, one of those
rare bright days in the UK. I guess this will have to wait until
i can do a nightime run, as my coil is run outside. The final
output was maxed out at about 1ft but THIN SPINDLY sparks. I
figure this to be due to either a lossy cap, gaps or both. I'm
limited as to my cap but I could try only 1 gap, maybe just the
brass one, what do people think of this strategy?


My next steps:

1. reduce No. of gaps

2. I would like to rewire my HV transformer to give say 15kv
instead of 25. Can I just rewind the secondary with this ratio
reduction in turns, beefing up the wire diameter and get the
proportional boost in current capability? The transformer is of
open construction, the core comes apart and the windings are on
bobbins, no epoxy has been used to encapsulate the windings.

3. I feel my aspect ratio may be too long on the secondary, I'm
tempted to remove 200 turns. 

4. From looking at Mr. Hull's photographs, I am convinced my
toroid is too small, although perfectly formed. I am trying to
source flexible drain pipe and Al tape.

5. My hand's up for one of those sexy Condenser Products caps if
there's another order going in.

6. Mr Hull mentions spiralling the top few turns on the secondary
in decreasing circles until the toroid is reached, I will try
this, and elevating the toroid further.


7. I have access to a digital camera, I will take some photos
soon, how do I go about putting them on the FTP server or sending
them to the list(s)?


8. I would like to make the coil generate a double dodecahedron
rotating merkaba field, so that I can teleport back into time.
Any ideas?

Thanks for listening

all comments gratefully received


Steve

********************** Let Them Eat Static ******************