[SEL] Recharging of Maytag coils

Mon Jun 8 19:28:42 PDT 2009

Hi Bill,
  Long Time no hear. How was Waukee this year? I hear things were 
some better then last. Sure missed going out.
  Hows Mike B  haven't heard from him in even longer. Mark

At 09:26 PM 6/8/2009, you wrote:
>Yes, I was trained by Sun on the use of he scope, own a scope now, and got
>my first job by showing the service manager what was wrong with the Ford he
>ws working on.
>You can see it all in the scope pattern...... And tell a LOT about an
>engine, even mechanically, if you can read the scope.
>The full operating of the system would take pages............
>
>I've still got all my Sun training guides downstairs......... Pages and
>pages.
>
>-----Original Message-----
>From: sel-bounces at lists.stationary-engine.com
>[mailto:sel-bounces at lists.stationary-engine.com] On Behalf Of Elden DuRand
>Sent: Monday, June 08, 2009 6:48 PM
>To: The SEL email discussion list
>Subject: Re: [SEL] Recharging of Maytag coils
>
>Jerry & Bill:
>
>A couple of years ago, I did a study of point/coil/condenser (battery or
>mag) and ignitor ignition electrics.
>
>The condenser is, in fact, needed in order to produce a "hot" spark at the
>plug.  As a side effect, it also supresses arcing at the points.
>
>What you have with this type of ignition is a parallel resonant L/C circuit.
>The "L" is the inductance of the primary of the coil plus the reflected
>inductance of the secondary of the coil.  The "C" is the capacitance of the
>condenser.
>
>What happens is that when the points are closed, there is a magnetic field
>produced by the primary in the core of the coil.  At this time, the
>condenser does not exist in the circuit, being short-circuited by the
>points.
>
>The fun begins when the points open.  As soon as the points open, the field
>of the coil begins to collapse, inducing a voltage across the condenser
>which is now in the circuit.  The rate at which the voltage rises is
>dependent upon the capacity of the condenser and the inductance of the coil.
>Once the coil's field has collapsed completely (and made one spark at the
>plug), the condenser is charged up and has nowhere else to discharge itself
>but back into the primary of the coil, which it does, causing the magnetic
>field to build back up in the coil (albeit at a lower voltage|).  When the
>condenser has discharged itself, the field of the coil again collapses
>(making another, weaker, spark) and charges the condenser again.  This goes
>on for several cycles and is called a "damped oscillation".
>
>The reason the points burn if you don't have a condenser across them is that
>the voltage rises faster than the points can open and a series of small arcs
>occur at the points as they relatively slowly open, adding up to a big
>heating event.
>
>There is actually a damped oscillation in the coil even without the
>condenser.  This is caused by the distributed capacitance of the coil and
>wiring.  The frequency of this oscillation is very high and the coil, as
>designed, is very inefficient at producing a high secondary voltage at this
>frequency.
>
>If you want to see oscilloscope pictures of what happens in a
>point/coil/condenser, go to my web page (below my signature) then go to
>"Otherstuff" and pick your subject.
>
>Oh, yes.  You can get very scientific about the value of the condenser used
>but most of the coils aren't very picky about just what resonant frequency
>they resonate at.  As long as the value is between 0.15 microfarad and 0.47
>microfarad, you should be okay.  If you get a non-automotive condenser, get
>a film type (NOT ELECTROLYTIC!) capacitor rated at 630 Volts DC and you will
>be fine.
>
>Please note that this is just an audit class.  No quizzes will be given.
>
>Take care - Elden
>http://www.oldengine.org/members/durand
>
> > -----Original Message-----
> > From: sel-bounces at lists.stationary-engine.com
> > [mailto:sel-bounces at lists.stationary-engine.com]On
> >  Behalf Of
> > bill at antique-engines.com
> > Sent: Monday, June 08, 2009 02:14 PM
> > To: The SEL email discussion list
> > Subject: Re: [SEL] Recharging of Maytag coils
> >
> >
> > Having a degree in automotive technology, earned when points were
> > still in use to some degree, here's why I state that it MAY, mind you
> > MAY not start and/or run, or run properly:
> >
> > When the points open, the sudden loss of primary current causes a
> > quickly collapsing magnetic field in the coil which induces a larger
> > voltage in the secondary windings. The voltage traveling through the
> > secondary winding in turn induces a current flow, in reverse, in the
> > primary circuit
> > - enough to cause the points to arc.
> > This "back emf" is due to the design of the ignition coil and its
> > inherent inductance.  This feedback of electrical energy causes a
> > spark to occur at the points that pits and erodes the contact
> > surfaces.  To suppress this energy, a condenser is used.  It acts like
> > a shock absorber (absorbing the back emf), ** and in so doing it helps
> > to interrupt the primary current as quickly as possible when the
> > points open.
> > Without the condenser, the back emf would form an arc across the
> > points as they separate, ** slowing the collapse of the coil's field,
> > thus delaying and thereby reducing the voltage rise in the secondary
> > coil winding - ~possibly~ reducing it enough to cause it to not span
> > the plugs gap.  The condenser suppresses most, but not all of the back
> > emf. So points still burn or erode.
> >
> > Bill
> >
> > > It should start and run without the condenser
> > but only till the
> > > points burn which can be fairly quickly. The
> > condenser has little to
> > > do with the actual generation of spark, more to
> > do with the
> > > protection of the points from arching and
> > burning quickly. If you try
> > > it without a condenser gap the points a bit
> > wider then the spec .020
> > > to get a clean break or so that the arc flame
> > between the points does
> > > quit due to width of gap.        Mark
>
>
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Mark Shulaw
454 Co. Rd. 33
Bluffton, OH. 45817
USA

Frappi at wcoil.com / 419.358.5206  Home / 419.516.2996 Ver. Cell.
Hobby Collector and Dealer in Maytag Multi-Motor Engine parts.
VISIT the Maytag Collectors Club at  www.Maytagclub.com  