Re: familiair with rumkorff inductors? (fwd)

---------- Forwarded message ----------
Date: Sat, 20 Dec 1997 22:15:41 -0800
From: "Norman F. Stanley" <nfs-at-midcoast-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: familiair with rumkorff inductors? (fwd)

At 04:31 PM 12/20/97 -0700, you wrote:
>---------- Forwarded message ----------
>Date: Sat, 20 Dec 1997 22:15:40 +0100
>From: solva-wijnschenk <solva-at-xs4all.nl>
>To: "tesla-at-pupman-dot-com" <tesla-at-pupman-dot-com>
>Subject: familiair with rumkorff inductors?
>dear all,
>I am reading tons of stuff to get myself to build an own
>coil safely. I could lay hand on a original rumkorff inductor
>which is a special constructed coil with integrated interruptor
>producing arches of 10 cm easily out of 12 volt dc.
>While this represents maybe >80.000 at low kva (less then 60
>watts!!). it seems to me that it is a (kind of) safe way to
>build the primary tankcircuitry of the coil with.
>Is there anybody familiair with this way of constructing or
>is it not possible?
>thanks for your soon reply!
>BTW is there a kind of newwsgroup to subscribe to to get a wider reply??

Ruhmkorff coils or induction coils date back about 150 years,
 and were popular with electrical experimenters back in the days when
widespread AC electrification was not around.  The coil consists of an iron
core, usually a bundle of iron wires, wound with an inner primary and outer
secondary, the latter consisting of many turns of fine wire, commonly #36
or #40. For large coils generating very high voltages the secondary may be
wound in "pies" which are connected in series to get the voltage with less
risk of breakdown between turns.  The interrupter or vibrator is commonly
mounted at the end of the core to be actuated by the magnetic field of the
core, although separate interrupters, such as the Wehnult, were sometimes
used by experimenters of 80 to 100 years ago.  They were usually wound to
operate on 6 or 12 volt DC supplied from batteries.  Examples of such coils
may still be found in school and college physics laboratories, and I
believe are still available from scientific supply houses at hefty prices.
I've seen specifications for coils giving up to 18" sparks.  The undisputed
grand daddy of induction coils was the Spottiswoode coil, constructed back
in the 1860s, which was capable of throwing a 40" spark.  It is described
in an article, "The Induction Coil", in the May 1971 issue of Scientific

The venerable Ford coil is another example much used by amateur
experimenters in the good old days.  Induction coils were also used to
power early spark transmitters and, yes, Tesla coils.  A Ford coil, giving
about a 0.75" spark, could energize a Tesla coil giving a 4" spark,
according to an article in Gernsback's "Everyday Science and Mechanics"
back in the thirties (the experts on this list nowadays could undoubtedly
do better).