X-Virus-Scanned: clean according to Sophos on Logan.com
Return-Path: <marv@lancaironline.net>
Sender: <marv@lancaironline.net>
To:  lml@lancaironline.net
Date: Mon, 16 Apr 2012 08:13:56 -0400
Message-ID: <redirect-5482947@logan.com>
X-Original-Return-Path: <billhogarty@gmail.com>
Received: from mail-lb0-f180.google.com ([209.85.217.180] verified)
  by logan.com (CommuniGate Pro SMTP 5.4.4)
  with ESMTPS id 5480942 for lml@lancaironline.net; Sat, 14 Apr 2012 00:46:59 -0400
Received-SPF: pass
 receiver=logan.com; client-ip=209.85.217.180; envelope-from=billhogarty@gmail.com
Received: by lbbgp3 with SMTP id gp3so756383lbb.25
        for <lml@lancaironline.net>; Fri, 13 Apr 2012 21:46:22 -0700 (PDT)
MIME-Version: 1.0
Received: by 10.152.130.167 with SMTP id of7mr3450854lab.36.1334378782209;
 Fri, 13 Apr 2012 21:46:22 -0700 (PDT)
Received: by 10.112.22.134 with HTTP; Fri, 13 Apr 2012 21:46:22 -0700 (PDT)
In-Reply-To: <list-5480913@logan.com>
References: <list-5480913@logan.com>
X-Original-Date: Fri, 13 Apr 2012 21:46:22 -0700
X-Original-Message-ID: <CAAXEWUqazgrCOev6ARWjtWzM3QSB_OL_h-aB0KXXUWJAKRtqEA@mail.gmail.com>
Subject: Re: [LML] Re: P-Lead
From: "William A. Hogarty" <billhogarty@gmail.com>
X-Original-To: Lancair Mailing List <lml@lancaironline.net>
Content-Type: multipart/alternative; boundary=f46d042c6c3f4f348104bd9c45ef

--f46d042c6c3f4f348104bd9c45ef
Content-Type: text/plain; charset=ISO-8859-1

Ed:  A simple answer to your question :   The purpose of grounding the P
lead is to prevent the magneto from operating.  Without the P lead, the
mageneto
is hot (assuming that you have a good magneto).  Be careful.

Regards, bill Hogarty

On Fri, Apr 13, 2012 at 9:02 PM, Brent Regan <brent@regandesigns.com> wrote:

>  Ed asks: "what is the point of grounding the P-lead if it is ground
> already? "
>
> Answer: To keep it grounded.
>
> A magneto has three main components, a dynamo, a high voltage transformer
> and a distributor. The high voltage transformer has a low number of turns
> primary and a high number of turns secondary. Both primary and secondary
> have one lead grounded. On the secondary the other lead goes to the
> distributor and then eventually to the spark plug(s). On the primary the
> other lead of  goes to the breaker points (a cam actuated normally closed
> switch). The other side of the points are connected to ground.
>
> The P-Lead stud is connected to the point there the primary lead is
> connected to the points. Therefore, when the points are closed the
> resistance to ground will be zero ohms. When the points are open the
> resistance to ground will be around an ohm or two, which is the DC
> resistance of the primary winding.
>
> In operation, the rotating magnet of the magneto produces an alternating
> magnetic field in the core of the transformer. With the points closed, the
> primary winding is shorted so a current is generated by the changing
> magnetic field. This current generates its own local magnetic field. When
> the points open, the current goes to zero and the local magnetic field
> collapses quickly. Since voltage is a function of the speed that a magnetic
> field changes and the number of turns exposed to the change, the rapidly
> collapsing field produces a high voltage in the secondary winding. When the
> voltage gets high enough a spark is established.
>
> If the P-Lead stud is shorted then the primary circuit is never opened,
> the magnetic field never collapses quickly and the spark is not generated.
>
> Disconnect the P-Lead from the stud on the magneto and verify your
> airplane's P-Lead is shorted to ground when the ignition is OFF and open
> when the ignition is ON. The P-Lead stud on the magneto will always be
> within a couple of ohms of ground.
>
> Regards
> Brent Regan
>

--f46d042c6c3f4f348104bd9c45ef
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

<div>Ed:=A0=A0A simple answer to your question :=A0=A0 The purpose of groun=
ding the P</div><div>lead is to prevent the magneto from operating.=A0 With=
out the P lead, the mageneto</div><div>is hot (assuming that you have a goo=
d magneto).=A0 Be careful.</div>
<div>=A0</div><div>Regards, bill Hogarty<br><br></div><div class=3D"gmail_q=
uote">On Fri, Apr 13, 2012 at 9:02 PM, Brent Regan <span dir=3D"ltr">&lt;<a=
 href=3D"mailto:brent@regandesigns.com">brent@regandesigns.com</a>&gt;</spa=
n> wrote:<br>
<blockquote style=3D"margin:0px 0px 0px 0.8ex;padding-left:1ex;border-left-=
color:rgb(204,204,204);border-left-width:1px;border-left-style:solid" class=
=3D"gmail_quote">
 =20

   =20
 =20
  <div text=3D"#000000" bgcolor=3D"#FFFFFF">
    Ed asks: &quot;<span style=3D"font-size:14pt">what is the point of
      grounding the P-lead if it is ground already? &quot;<br>
      <br>
      Answer: To keep it grounded.<br>
      <br>
      A magneto has three main components, a dynamo, a high voltage
      transformer and a distributor. The high voltage transformer has a
      low number of turns primary and a high number of turns secondary.
      Both primary and secondary have one lead grounded. On the
      secondary the other lead goes to the distributor and then
      eventually to the spark plug(s). On </span><span style=3D"font-size:1=
4pt">the primary</span><span style=3D"font-size:14pt"> the other lead of=A0=
 goes to the breaker
      points (a cam actuated normally closed switch). The other side of
      the points are connected to ground.<br>
      <br>
      The P-Lead stud is connected to the point there the primary lead
      is connected to the points. Therefore, when the points are closed
      the resistance to ground will be zero ohms. When the points are
      open the resistance to ground will be around an ohm or two, which
      is the DC resistance of the primary winding. <br>
      <br>
      In operation, the rotating magnet of the magneto produces an
      alternating magnetic field in the core of the transformer. With
      the points closed, the primary winding is shorted so a current is
      generated by the changing magnetic field. This current generates
      its own local magnetic field. When the points open, the current
      goes to zero and the local magnetic field collapses quickly. Since
      voltage is a function of the speed that a magnetic field changes
      and the number of turns exposed to the change, the rapidly
      collapsing field produces a high voltage in the secondary winding.
      When the voltage gets high enough a spark is established. <br>
      <br>
      If the P-Lead stud is shorted then the primary circuit is never
      opened, the magnetic field never collapses quickly and the spark
      is not generated.<br>
      <br>
      Disconnect the P-Lead from the stud on the magneto and verify your
      airplane&#39;s P-Lead is shorted to ground when the ignition is OFF
      and open when the ignition is ON. The P-Lead stud on the magneto
      will always be within a couple of ohms of ground. <br>
      <br>
      Regards<br><font color=3D"#888888">
      Brent Regan<br>
    </font></span>
  </div>

</blockquote></div><br>

--f46d042c6c3f4f348104bd9c45ef--