RE: Early versions of Tesla's coil

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <teslalist-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi John,

On 4 Jul 2003, at 12:58, Tesla list wrote:

 > Original poster: "John H. Couture by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>
 >
 >
 > Malcolm -
 >
 > Isn't this an induction coil that operates when the buzzer contacts open not
 > when the contacts close as with a Tesla coil? It could therefore not operate
 > in cap discharge fashion. The capacitor would be to protect the buzzer
 > contacts from the inductive kick (back emf) of the coil and not as a storage
 > cap as in a Tesla coil.
 >
 > John Couture

I dug out the book over the weekend and perused the relevant section.
Tesla's description of it is that of an "entirely new principle of
operation" or words to that effect. I have scanned some pages to send
to Richard if his bandwidth permits sending a 6MB-odd file. The coil
is not iron-cored. It is essentially a halfwave coil with two
sections wound as lumped inductors - at least that is my reading of
it. I will do a further check this evening. You may be right.

Malcolm

 > ------------------------------
 >
 >
 > -----Original Message-----
 > From: Tesla list [mailto:tesla-at-pupman-dot-com]
 > Sent: Thursday, July 03, 2003 10:26 PM
 > To: tesla-at-pupman-dot-com
 > Subject: Re: Early versions of Tesla's coil
 >
 >
 > Original poster: "Malcolm Watts by way of Terry Fritz <teslalist-at-qwest-dot-net>"
 > <m.j.watts-at-massey.ac.nz>
 >
 > Hi Richard,
 >
 > On 3 Jul 2003, at 18:26, Tesla list wrote:
 >
 >   > Original poster: "RMC by way of Terry Fritz <teslalist-at-qwest-dot-net>"
 > <RMC-at-richardcraven.plus-dot-com>
 >   >
 >   >
 >   > Referring to this image:
 >   >
 >   > http://www.pbs-dot-org/tesla/ins/images/tc_main01.jpg
 >   >
 >   > We see an image of an early coil of the type designed and built by Tesla
 > in
 >   > the earlier part of his career leading up to the end of the 19th 
century.
 >   >
 >   > 1) Has anyone seen any better pictures?
 >
 > I have the book of the lecture/s and I *think* there is a diagram of
 > the coil in there together with a spark photo.
 >
 >   > 2) Can anyone accurately describe what various components we are looking
 > at
 >   > in the picture?
 >
 > The coil itself is air-cored, the secondary being wound in two
 > sections with the primary in the centre.
 >
 > --(ASIDE: Because I was so fascinated by the brush discharges between
 > the loops of wire coming off the secondary terminals, I built a
 > similar machine to see the effects. Mine employed a ferrite core and
 > was a lot less exacting in manufacture. I used plasitc solder reels
 > for each secondary half and wound them with PVC-covered wire. I also
 > popped the whole assembly into a plexi container and oil-filled it
 > (that was when I discovered that silicone rubber didn't go well with
 > transformer oil - I'd used it to "seal" gaps in the container joints
 > ;).
 >
 >        The primary of the original was activated in cap discharge
 > fashion using a buzzer type contact arrangement (the front upright
 > coil). The hot end of each secondary winding is located where the
 > leads emerge from the secondary (i.e. the effective center-tap
 > between the two halves is located just beneath the surface insulation
 > covering the outer turns. Some of this is probably not well
 > remembered. I will scan what diagrams I have and send it to you off-
 > list from home (I'm off work next week). Feel free to share them if
 > you wish.
 >
 >         BTW, the effects are not unique to this type of machine and
 > although building it was instructive, I'd never bother doing it again.
 > I seem to recall it was around this time that Tesla was talking about
 > 1/4 wave secondaries (from a wirelength point of view) and a 1/2 wave
 > primary (also from a wire length point of view! which he then all but
 > admitted was not practical).
 >
 > Malcolm
 >
 >   > 3) Do we know anything about the power supply input required to drive
 > this
 >   > type of machine?
 >   >
 >   > I know this variety of machine was demonstrated at the IEE in London as
 > well
 >   > as at various USA events and was an oil-immersed secondary, not
 >   > ground-referenced.  I have seen some of the photgraphs in the lecture he
 >   > presebted ("experiments in alternating currents of high potential and
 > high
 >   > frequency" is the approximate title) and also seen the impressive brush
 >   > discharge shots. I know nothing about the primary gap or cap or turns or
 >   > secondary or M or resonant frequencies.
 >   >
 >   > Cheers
 >   >
 >   > RMC, England
 >   >
 >   >
 >   >
 >
 >
 >