From: Dale Hall [SMTP:Dale.Hall-at-trw-dot-com]
Sent: Saturday, June 27, 1998 4:31 PM
To: Tesla List
Subject: RE>New Coil
Good find on the glass/epoxy 6 5/8"x 3/16" x 54"
I've been searching for epoxyglass 6" - 12" forms for years unsucessfully!
At 4:1 you can make two 27", I'd use #22
Glad to hear from fellow Low Power DC coilers !
Keep the copier supply, it provides 3X the current of my little flyback.
There were two limits to the discharges in your previous coils performance.
Coil diameter and gap quench (& another .05uF would have helped)
Mylar caps perform for awhile but don't last long (did you see int cap arcs?)
While I recommend a vac gap, an RQ 3 cylinder beats two bent wires.
Your copier supply with a 6.25" PVC Sec #22 or #24 awg, a vacuum gap, and
a .1uF ruby mica or hommade polyethelene or polypropylene oil cap will do
10" power arcs with an 8" galvanized 4x90degree elbow toroid !! And yours
will do it 3X as often as mine (maybe more cause a PS rated at .6ma can
usually provide more)
Of course with AC excitation of sufficient power & RSG you could get 3-7' arcs
Dale Redondo Beach, Calif
excerpt form prev post:
My 6.25"x16" coil powered by 5kVdc flyback, 12v .04A consumes less ~1/2 watt Cpri= .1uF gap=small vacuum switch. Low power trade = one 8-10" bang\per sec. (1.25J, a reliable power arc is produced at each gap firing with 8"x22" galvanized torus using a protruding point to point ground) Ccharge 5kV*.25ma for 1s= 1.25J
Helical Pri=.125"x11" Cu tubing tap ~3.8 turns Lsec=15.7mH (#22awg HPT)
Ipri =~600 Apk ~260 kHz Iarc=~23 Apk ~2 Mhz (23A*(xL=26138) = ~601kV)
(the calc V is likely bogus - used induct reactance of Sec * arc peak current)
Goiing to higher V flybacks for >1.25J/bang say up to 5J chg=20kV*.25ma for 1s (use lower Cpri for less Ipkgap) will yield longer sparks at greater input
energy expenditure but still small compared to the AC input power case which generates more sparks/sec at a cost of more average input power required.
another excerpt ...
(I get 9" from my Portable Battery powered (12v.04A)
6.25" Sec with 1.25J -at- 5kVdc & .1 & a vacuum switch (NO noise - great quench)
- mileage may vary w/air gap, increased voltage should result in much longer
sparks J=c*v*v/2). .........
The trick to using flybacks with batteries is efficient electronics driver design.
Most of the posted designs use a push pull cfg which draws amps at ~25v.
A single FET or bipolar drive like the one in my 5kV is most efficient. It should
be designed such that the idle current is very low but rises upon demand - like
when charging the primary CAP. The flyback driver I use came with it. I merely
stripped out the unneeded functions (extra voltages for the CRT) from a 1" video
camera B/W monitor. The idle current is ~36 ma (this could improved upon if
I ever get motivated) at 12v (was designed for ~9v, I push it - been using it that
for years). I use rechargable AA NiCads which are available up ~2200 mAH
capacities (2200/50=~44hr) or single use alkalines could extend that 2-3x.
As I mentioned in the previous post, the most economical and easiest way to
checkout the DC mode: find an old B/W TV or video monitor and tap into the
anode connection. I remove the CRT socket to kill filament power and the
current drawn by the e-beam to get every uA to charge Cpri. The normal HV
precautions should be taken so as to not cause the muscle contraction (i.e.
don't touch charged stuff, discharge before contacting, ). To measure the HVDC
I use a 1000:1 resistive divider (1V dmm scale = 1kV) 999M to 1.1M to plug
into a 10Meg DMM. The load on the HV is only 1ua per kV + isolates DMM.
Date: 6/26/98 9:39 PM
To: Dale Hall
From: Tesla List
From: David Dean [SMTP:deano-at-corridor-dot-net]
Sent: Thursday, June 25, 1998 8:24 PM
To: Tesla List
Subject: New Coil
Just acquired a distribution transformer
nameplate specs KVA 5 , %IMP -at- 85deg C 1.6
high voltage 7200/12470 , 14400/24940
low voltage 120/240 , non PCB
switch set at 14400
About two months ago found a piece of spun fiberglass pipe 6" nom.
Actual O.D. 6 5/8"
wall thickness 3/16" overall length 54". This is glass/epoxy.
Now I've got the itch.
Have been following the thread about conventional coils being magnifiers
with some interest.
This idea was presented to me by a Mr. Mull about 12 years ago, just
before he died, along with some
other interesting ideas, things he had tried when he was an avid coiler
back in the '30s.
About 3 1/2 years ago I made a small coil with two windings on one
coilform, first winding
about five inches long, then very widely spaced turns for about twenty
inches, then another winding about
fifteen inches long. This was on a 1 1/2" OD acrylic tube with #40 wire.
Primary was about twenty turns of
#12 wire on a cardboard tube 3 1/2" Dia. Power source was a copier power
supply 5.5KV DC -at- 0.6mA.
Cap was internal to power supply, when the supply died, I dissected it
and found the cap to be rated
12KV DC .050 uF mylar dielectric. Spark gap was two bent copper wires.
It made 1 1/2 inch sparks
with or without any topload. Very disappointing.
>From what I have learned during the last ten months reading on this
list, I can see why it did not work well.
Everything was wrong. However, once bitten, twice shy. I am now inspired
to think that it might work,
but I don't want to waste a coilform that I am unlikely to happen across
So, should I stick to the tried and true? Or should I go for broke...
Any suggestions will be appreciated.