shop-talk
[Top] [All Lists]

Re: [Shop-talk] Mower blade orientaaion relative to piston

To: "dirtbeard@gmail.com" <dirtbeard@gmail.com>, "bspidell@comcast.net" <bspidell@comcast.net>
Subject: Re: [Shop-talk] Mower blade orientaaion relative to piston
From: DAVID MASSEY <dave1massey@cs.com>
Date: Wed, 19 May 2021 12:07:35 +0000 (UTC)
Cc: "shop-talk@autox.team.net" <shop-talk@autox.team.net>
Delivered-to: mharc@autox.team.net
Delivered-to: shop-talk@autox.team.net
References: <000601d74c30$1ae5adc0$50b10940$@GMail.com> <MW2PR07MB397889AB84D2574BA8B851DCBB2C9@MW2PR07MB3978.namprd07.prod.outlook.com> <5ff69898-d0ef-8db4-db6d-f57f9b5bbdcf@comcast.net> <CAG1pxgaBSqYewhJsaMJPPRkp6xBJ5YNUE5vSLVO4RCGhrSgFUQ@mail.gmail.com> x64; rv:88.0) Gecko/20100101 Firefox/88.0
--===============0961169033576184577==
        boundary="----=_Part_1251050_1669472372.1621426055738"

------=_Part_1251050_1669472372.1621426055738
Content-Transfer-Encoding: quoted-printable

 I would find it mildly surprising if they were triggering off of the blade=
 but any motor I've worked on is at least 20 years old.=C2=A0 On those moto=
rs (a couple Briggs and Scrapiron and a Tecumseh) had the magneto in the fl=
ywheel on the opposite end.=C2=A0 They will run without the blade attached.=
=C2=A0 Triggering off the blade means that motor is a special-purpose model=
 for that application.=C2=A0 The economies of scale favor a more generic de=
sign.
=20
Dave=20

=20
=20
-----Original Message-----
From: old dirtbeard <dirtbeard@gmail.com>
To: Bob Spidell <bspidell@comcast.net>
Cc: shop-talk@autox.team.net
Sent: Tue, May 18, 2021 9:38 pm
Subject: Re: [Shop-talk] Mower blade orientaaion relative to piston

Hi Bob,
I believe=C2=A0you, of course, but I have never heard this=C2=A0before.=C2=
=A0 I have a Craftsman 21" walk behind and I usually sharpen the blade and =
do maintenance=C2=A0this month, so I think I will see if the engine will fi=
re with the blade removed for sharpening.
For this to make sense to me, there would need to be some sensor on the bla=
de, or they are using iron mass of the blade as part of the inductance fiel=
d to signal the position for coil firing. The aluminum sump of the motor pr=
otrudes=C2=A0through the steel deck of the mower, so I suppose it is possib=
le. There is quite an air gap between the blade and the sump of the engine,=
 however.
You have me very curious and I will let you know if the mower will fire wit=
hout the blade=C2=A0attached (if it does, I will not let it run as it is ha=
rd to predict what would happen without that flywheel attached to the crank=
shaft).
best,
doug=C2=A0
On Tue, May 18, 2021 at 5:35 PM Bob Spidell <bspidell@comcast.net> wrote:

  Possibly of some interest: I had a Craftsman walk-behind that quit runnin=
g suddenly. I tore the engine down, didn't find anything, then finally took=
 it to a repair shop. They told me the blade had a crack in it that caused =
the problem; supposedly the blade is part of a timing loop that fires the s=
park. Sort of makes sense if you think of the blade as a flywheel with a po=
sition sensor on it.
=20
 Bob
=20
 On 5/18/2021 2:55 PM, Brian and Wendy Warrick wrote:
 =20
  I run Snapper walk behind mowers and have never gave it a thought. I can'=
t see why it would matter. If it did, they would have designed the adapter =
differently. =20
   Brian  Nampa, ID  =20
   From: Shop-talk <shop-talk-bounces@autox.team.net> on behalf of Karl Vac=
ek <stearman809@gmail.com>
 Sent: Tuesday, May 18, 2021 3:52 PM
 To: 'shop-talk@autox.team.net' <Shop-talk@autox.team.net>
 Subject: [Shop-talk] Mower blade orientaaion relative to piston =C2=A0    =
 Last time I sharpened my 21=E2=80=9D walk-behind mower blade I thought of =
something that=E2=80=99s never occurred to me, after using the same brand o=
f mower for 25 years..  =C2=A0  On a Snapper, the blade can actually go on =
any way onto the square adapter keyed to the crankshaft.=C2=A0 The mounting=
 point is square, no pins, no longer side, nothing.  =C2=A0  One way would =
be aligned with the cylinder at TDC/BDC, and the other way would be across.=
=C2=A0 It=E2=80=99s been off many times and there=E2=80=99s no way to tell =
how it was mounted originally.=C2=A0 The manual is silent on this.  =C2=A0 =
 Power stroke shouldn=E2=80=99t matter, but maybe some dynamic issue one wa=
y or the other?  =C2=A0  Thanks!
 Karl   =20
=20
=20
 _______________________________________________

Shop-talk@autox.team.net
Archive: http://www.team.net/pipermail/shop-talk http://autox.team.net/arch=
ive

rd@gmail.com


_______________________________________________

Shop-talk@autox.team.net
Archive: http://www.team.net/pipermail/shop-talk http://autox.team.net/arch=
ive

ssey@cs.com


------=_Part_1251050_1669472372.1621426055738
Content-Transfer-Encoding: quoted-printable


<div style=3D"color:black;font: 12pt Arial, Helvetica, sans-serif;">
<div> <font size=3D"3">I would find it mildly surprising if they were trigg=
ering off of the blade but any motor I've worked on is at least 20 years ol=
d.&nbsp; On those motors (a couple Briggs and Scrapiron and a Tecumseh) had=
 the magneto in the flywheel on the opposite end.&nbsp; They will run witho=
ut the blade attached.&nbsp; Triggering off the blade means that motor is a=
 special-purpose model for that application.&nbsp; The economies of scale f=
avor a more generic design.</font><br>
</div>

<div> <br>
</div>

<div style=3D"clear:both"><font size=3D"4">Dave </font><br>
<br>
</div>

<div> <br>
</div>

<div> <br>
</div>

<div style=3D"font-family:arial,helvetica;font-size:10pt;color:black"><font=
 size=3D"2">-----Original Message-----<br>
From: old dirtbeard &lt;dirtbeard@gmail.com&gt;<br>
To: Bob Spidell &lt;bspidell@comcast.net&gt;<br>
Cc: shop-talk@autox.team.net<br>
Sent: Tue, May 18, 2021 9:38 pm<br>
Subject: Re: [Shop-talk] Mower blade orientaaion relative to piston<br>
<br>

<div id=3D"yiv5420248293">
<div>
<div dir=3D"ltr">Hi Bob,
<div><br clear=3D"none"></div>

<div>I believe&nbsp;you, of course, but I have never heard this&nbsp;before=
.&nbsp; I have a Craftsman 21" walk behind and I usually sharpen the blade =
and do maintenance&nbsp;this month, so I think I will see if the engine wil=
l fire with the blade removed for sharpening.</div>

<div><br clear=3D"none"></div>

<div>For this to make sense to me, there would need to be some sensor on th=
e blade, or they are using iron mass of the blade as part of the inductance=
 field to signal the position for coil firing. The aluminum sump of the mot=
or protrudes&nbsp;through the steel deck of the mower, so I suppose it is p=
ossible. There is quite an air gap between the blade and the sump of the en=
gine, however.</div>

<div><br clear=3D"none"></div>

<div>You have me very curious and I will let you know if the mower will fir=
e without the blade&nbsp;attached (if it does, I will not let it run as it =
is hard to predict what would happen without that flywheel attached to the =
crankshaft).</div>

<div><br clear=3D"none"></div>

<div>best,</div>

<div><br clear=3D"none"></div>

<div>doug&nbsp;</div>
</div>
<br clear=3D"none">
<div class=3D"yiv5420248293gmail_quote">
<div class=3D"yiv5420248293yqt9341191006" id=3D"yiv5420248293yqt66682">
<div class=3D"yiv5420248293gmail_attr" dir=3D"ltr">On Tue, May 18, 2021 at =
5:35 PM Bob Spidell &lt;<a rel=3D"nofollow noopener noreferrer" shape=3D"re=
ct" ymailto=3D"mailto:bspidell@comcast.net"; target=3D"_blank" href=3D"mailt=
o:bspidell@comcast.net">bspidell@comcast.net</a>&gt; wrote:<br clear=3D"non=
e"></div>
<blockquote class=3D"yiv5420248293gmail_quote" style=3D"margin:0px 0px 0px =
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex;">
 =20
   =20
 =20
 =20
<div>
    Possibly of some interest: I had a Craftsman walk-behind that quit
    running suddenly. I tore the engine down, didn't find anything, then
    finally took it to a repair shop. They told me the blade had a crack
    in it that caused the problem; supposedly the blade is part of a
    timing loop that fires the spark. Sort of makes sense if you think
    of the blade as a flywheel with a position sensor on it.<br clear=3D"no=
ne">
    <br clear=3D"none">
    Bob<br clear=3D"none">
    <br clear=3D"none">
   =20
<div>On 5/18/2021 2:55 PM, Brian and Wendy
      Warrick wrote:<br clear=3D"none">
    </div>

    <blockquote type=3D"cite">
     =20
     =20
     =20
<div style=3D"font-family:Calibri, Helvetica, sans-serif;font-size:12pt;col=
or:rgb(0,0,0);">
        I run Snapper walk behind mowers and have never gave it a
        thought. I can't see why it would matter. If it did, they would
        have designed the adapter differently.</div>

     =20
<div style=3D"font-family:Calibri, Helvetica, sans-serif;font-size:12pt;col=
or:rgb(0,0,0);">
        <br clear=3D"none">
      </div>

     =20
<div style=3D"font-family:Calibri, Helvetica, sans-serif;font-size:12pt;col=
or:rgb(0,0,0);">
        Brian</div>

     =20
<div style=3D"font-family:Calibri, Helvetica, sans-serif;font-size:12pt;col=
or:rgb(0,0,0);">
        Nampa, ID</div>

     =20
<div>
       =20
<div style=3D"font-family:Calibri, Helvetica, sans-serif;font-size:12pt;col=
or:rgb(0,0,0);">
          <br clear=3D"none">
        </div>

        <hr style=3D"display:inline-block;width:98%;">
       =20
<div dir=3D"ltr" id=3D"yiv5420248293gmail-m_-6852136761353026904divRplyFwdM=
sg"><font style=3D"font-size:11pt;" face=3D"Calibri, sans-serif" color=3D"#=
000000"><b>From:</b>
            Shop-talk <a rel=3D"nofollow noopener noreferrer" shape=3D"rect=
" ymailto=3D"mailto:shop-talk-bounces@autox.team.net"; target=3D"_blank" hre=
f=3D"mailto:shop-talk-bounces@autox.team.net";>&lt;shop-talk-bounces@autox.t=
eam.net&gt;</a> on behalf
            of Karl Vacek <a rel=3D"nofollow noopener noreferrer" shape=3D"=
rect" ymailto=3D"mailto:stearman809@gmail.com"; target=3D"_blank" href=3D"ma=
ilto:stearman809@gmail.com">&lt;stearman809@gmail.com&gt;</a><br clear=3D"n=
one">
            <b>Sent:</b> Tuesday, May 18, 2021 3:52 PM<br clear=3D"none">
            <b>To:</b> '<a rel=3D"nofollow noopener noreferrer" shape=3D"re=
ct" ymailto=3D"mailto:shop-talk@autox.team.net"; target=3D"_blank" href=3D"m=
ailto:shop-talk@autox.team.net">shop-talk@autox.team.net</a>'
            <a rel=3D"nofollow noopener noreferrer" shape=3D"rect" ymailto=
=3D"mailto:Shop-talk@autox.team.net"; target=3D"_blank" href=3D"mailto:Shop-=
talk@autox.team.net">&lt;Shop-talk@autox.team.net&gt;</a><br clear=3D"none"=
>
            <b>Subject:</b> [Shop-talk] Mower blade orientaaion relative
            to piston</font>
         =20
<div>&nbsp;</div>

        </div>

       =20
<div lang=3D"EN-US">
         =20
<div>
           =20
<div style=3D"margin:0in 0in 0.0001pt;font-size:11pt;font-family:Calibri, s=
ans-serif;">
              Last time I sharpened my 21=E2=80=9D walk-behind mower blade =
I
              thought of something that=E2=80=99s never occurred to me, aft=
er
              using the same brand of mower for 25 years..</div>

           =20
<div style=3D"margin:0in 0in 0.0001pt;font-size:11pt;font-family:Calibri, s=
ans-serif;">
              &nbsp;</div>

           =20
<div style=3D"margin:0in 0in 0.0001pt;font-size:11pt;font-family:Calibri, s=
ans-serif;">
              On a Snapper, the blade can actually go on any way onto
              the square adapter keyed to the crankshaft.&nbsp; The mountin=
g
              point is square, no pins, no longer side, nothing.</div>

           =20
<div style=3D"margin:0in 0in 0.0001pt;font-size:11pt;font-family:Calibri, s=
ans-serif;">
              &nbsp;</div>

           =20
<div style=3D"margin:0in 0in 0.0001pt;font-size:11pt;font-family:Calibri, s=
ans-serif;">
              One way would be aligned with the cylinder at TDC/BDC, and
              the other way would be across.&nbsp; It=E2=80=99s been off ma=
ny times
              and there=E2=80=99s no way to tell how it was mounted origina=
lly.&nbsp;
              The manual is silent on this.</div>

           =20
<div style=3D"margin:0in 0in 0.0001pt;font-size:11pt;font-family:Calibri, s=
ans-serif;">
              &nbsp;</div>

           =20
<div style=3D"margin:0in 0in 0.0001pt;font-size:11pt;font-family:Calibri, s=
ans-serif;">
              Power stroke shouldn=E2=80=99t matter, but maybe some dynamic
              issue one way or the other?</div>

           =20
<div style=3D"margin:0in 0in 0.0001pt;font-size:11pt;font-family:Calibri, s=
ans-serif;">
              &nbsp;</div>

           =20
<div style=3D"margin:0in 0in 0.0001pt;font-size:11pt;font-family:Calibri, s=
ans-serif;">
              Thanks!<br clear=3D"none">
              Karl</div>

          </div>

        </div>

      </div>

      <br clear=3D"none">
    </blockquote>
    <br clear=3D"none">
  </div>


_______________________________________________<br clear=3D"none">
<br clear=3D"none">
<a rel=3D"nofollow noopener noreferrer" shape=3D"rect" ymailto=3D"mailto:Sh=
op-talk@autox.team.net" target=3D"_blank" href=3D"mailto:Shop-talk@autox.te=
am.net">Shop-talk@autox.team.net</a><br clear=3D"none">
lank" href=3D"http://www.team.net/donate.html";>http://www.team.net/donate.h=
tml</a><br clear=3D"none">
Archive: <a rel=3D"nofollow noopener noreferrer" shape=3D"rect" target=3D"_=
blank" href=3D"http://www.team.net/pipermail/shop-talk";>http://www.team.net=
/pipermail/shop-talk</a> <a rel=3D"nofollow noopener noreferrer" shape=3D"r=
ect" target=3D"_blank" href=3D"http://autox.team.net/archive";>http://autox.=
team.net/archive</a><br clear=3D"none">
<br clear=3D"none">
target=3D"_blank" href=3D"http://autox.team.net/mailman/options/shop-talk/d=
irtbeard@gmail.com">http://autox.team.net/mailman/options/shop-talk/dirtbea=
rd@gmail.com</a><br clear=3D"none">
<br clear=3D"none">
</blockquote></div>
</div>

</div>
</div>

<div class=3D"yqt9341191006" id=3D"yqt16240">______________________________=
_________________<br clear=3D"none"><br clear=3D"none"><a shape=3D"rect" ym=
ailto=3D"mailto:Shop-talk@autox.team.net"; href=3D"mailto:Shop-talk@autox.te=
am.net">Shop-talk@autox.team.net</a><br clear=3D"none">Donate: <a shape=3D"=
rect" href=3D"http://www.team.net/donate.html"; target=3D"_blank">http://www=
.team.net/donate.html</a><br clear=3D"none">Suggested annual donation&nbsp;=
 $12.96<br clear=3D"none">Archive: <a shape=3D"rect" href=3D"http://www.tea=
m.net/pipermail/shop-talk" target=3D"_blank">http://www.team.net/pipermail/=
shop-talk </a><a shape=3D"rect" href=3D"http://autox.team.net/archive"; targ=
et=3D"_blank">http://autox.team.net/archive</a><br clear=3D"none"><br clear=
=3D"none">Unsubscribe/Manage: <a shape=3D"rect" href=3D"http://autox.team.n=
et/mailman/options/shop-talk/dave1massey@cs.com" target=3D"_blank">http://a=
utox.team.net/mailman/options/shop-talk/dave1massey@cs.com</a><br clear=3D"=
none"><br clear=3D"none"></div>
</font></div>
</div>

------=_Part_1251050_1669472372.1621426055738--

--===============0961169033576184577==
Content-Transfer-Encoding: 7bit
Content-Disposition: inline

_______________________________________________

Shop-talk@autox.team.net
Archive: http://www.team.net/pipermail/shop-talk http://autox.team.net/archive



--===============0961169033576184577==--

<Prev in Thread] Current Thread [Next in Thread>