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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
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<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. On those motors (a couple Briggs and Scrapiron and a Tecumseh) had=
the magneto in the flywheel on the opposite end. They will run witho=
ut the blade attached. Triggering off the blade means that motor is a=
special-purpose model for that application. 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 <dirtbeard@gmail.com><br>
To: Bob Spidell <bspidell@comcast.net><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 you, of course, but I have never heard this before=
. I have a Craftsman 21" walk behind and I usually sharpen the blade =
and do maintenance 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 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 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 </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 <<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>> 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";><shop-talk-bounces@autox.t=
eam.net></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"><stearman809@gmail.com></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"><Shop-talk@autox.team.net></a><br clear=3D"none"=
>
<b>Subject:</b> [Shop-talk] Mower blade orientaaion relative
to piston</font>
=20
<div> </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;">
</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. 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;">
</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. It=E2=80=99s been off ma=
ny times
and there=E2=80=99s no way to tell how it was mounted origina=
lly.
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;">
</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;">
</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>
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