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Re: Model-T Ford coil



At 08:26 PM 12/9/96 -0700, Malcolm Watts wrote:
>>From MALCOLM-at-directorate.wnp.ac.nz Mon Dec  9 20:14:53 1996
>Date: Tue, 10 Dec 1996 08:50:53 +1200
>From: Malcolm Watts <MALCOLM-at-directorate.wnp.ac.nz>
>To: tesla-at-pupman-dot-com
>Subject: Re: Model-T Ford coil
>
>You can do OK with an induction-coil driven TC. I have obtained 6"+ of
>corona from a TC driven by a standard ignition coil run from a circuit
>using a power transistor for switching the coil and a variable mark-
>space ratio oscillator with a 12V supply. The primary cap was about 
>3000pF from memory.
>
>Malcolm
>
>> >        I recently got an old Model-T Ford coil. After
>> >an hour, I finally understood how it works. Pretty
>> >embarrising to take so long to figure out something so
>> >old and simple. Anyway, I have only a couple of plans
>> >for its use in a mini Tesla Coil, wrapping a coil around
>> >a wine bottle, and wondered if anybody had used the Ford
>> >coil in a project and what they have done.
>> >
>> >Thanks,
>> >Bob Schumann
>> >
>> Ford coils are simply induction coils.  As I recall, the old Model T used
>> four of them (one for each cylinder) mounted in a box beneath the dash.
>> They are still being manufactured for sale to antique car buffs, but are
>> pricey at about $50 a pop.  They were a standby for the electrical
>> experimenters of the Gernsback era.  Their innards consist of a primary
>> wound with (I think), #22 DCC magnet wire on an iron wire core, surrounded
>> by a secondary of #40 enamelled wire.  There is a tinfoil capacitor across
>> the secondary to give a "hot" spark. Connections are brought out to three
>> terminals, one being common to both primary and secondary.  With a clean and
>> well-adjusted interrupter it will give a 0.75" spark (and kick like a mule
>> if you get across the terminals).  It was claimed that a Ford coil driven
>> Tesla coil would give a 4" spark, but none of the coils I built back then
>> ever did much better than 1"-1.5".
>> 
>> Norm
>> 
One of the problems with getting good results from Ford coils was keeping
the interrupter contacts clean, particularly if one succumbed to the
temptation of running them with more than 6 VDC on the primary.  Using
modern electronic circuitry to replace the vibrator interrupter sounds like
a great idea.  My wimpy results may have been due due to poorly tuned Tesla
circuits.  I eventually eviscerated a couple of Ford coils and reassembled
the two primaries and secondaries into a transformer which put out about 5
Kv, and would give nice crackly 4" discharges from the terminals of my
bipolar Tesla secondary, with enough power to light 40-W incandescent bulbs
(and also, on one occasion, to kick back and demolish a light socket).

Norm 

>