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The whole propeller thing is really overstated. It is just there to keep
the pilot cool. If the propeller stops turning, the pilot often begins
sweating.
On Wed, May 19, 2021 at 5:15 AM Jeff Scarbrough <fishplate@gmail.com> wrote=
:
> Not to mention that there are two magnetos. You don't want your lawn
> mower quitting in mid-air.
>
> On Tue, May 18, 2021, 23:15 Bob Spidell <bspidell@comcast.net> wrote:
>
>> Magnetos still power the vast majority of small aircraft piston engines;
>> they're a bit more complicated though. Mags in good nick will throw a
>> really hot spark; they're always 'hot' and the only way to disable them
>> is to ground the primary coil by a 'P lead.'
>>
>> On 5/18/2021 8:03 PM, Thomas Coradeschi wrote:
>> > You=E2=80=99re almost certainly looking at a magneto ignition system i=
n all of
>> those small engines=E2=80=A6 Bog simple indeed!
>> >
>> > =E2=80=94
>> > Tom Coradeschi
>> > tjcora@icloud.com
>> >
>> >
>> >> On 18 May 2021, at 10:53 PM, Bob Spidell <bspidell@comcast.net> wrote=
:
>> >>
>> >> re: "... they are using iron mass of the blade as part of the
>> inductance field to signal the position for coil firing ..."
>> >>
>> >> That was my guess, based on what they told me; the motor was otherwis=
e
>> in good shape (how I managed to get it back together still amazes me).
>> IIRC, it was a Tecumseh 5HP engine. The name of the shop was 'Knife
>> Stalkers.'
>> >>
>> >> I'm looking into possibly rebuilding a couple chainsaw motors, the
>> coil and 'points,' or whatever solid state switch they are using, are ve=
ry
>> simplistic. There may be a magnet in the crank gear to trigger the spark=
. I
>> use Pertronix in several cars and, except for one they have a cap on the
>> distributor cam with magnets to fire the electronic switch. Surprising t=
o
>> me, the one on my 4-cyl Austin-Healey doesn't use the cap, apparently th=
e
>> lobes on the distributor cam are sufficient to fire the Hall Effect sens=
or.
>> >>
>> >> bs
>> >>
>> >> On 5/18/2021 7:38 PM, old dirtbeard wrote:
>> >>> Hi Bob,
>> >>>
>> >>> I believe you, of course, but I have never heard this before. I hav=
e
>> 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 will fire wi=
th
>> the blade removed for sharpening.
>> >>>
>> >>> For this to make sense to me, there would need to be some sensor on
>> the 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 su=
mp
>> of the motor protrudes through the steel deck of the mower, so I suppose=
it
>> is possible. 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 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).
>> >>>
>> >>> best,
>> >>>
>> >>> doug
>> >>>
>> >>> 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
>> 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 th=
e
>> blade as a flywheel with a position sensor on it.
>> >>>
>> >>> Bob
>> >>>
>> >>> On 5/18/2021 2:55 PM, Brian and Wendy Warrick wrote:
>> >>>> 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.
>> >>>>
>> >>>> Brian
>> >>>> Nampa, ID
>> >>>>
>> >>>> From: Shop-talk <shop-talk-bounces@autox.team.net> on behalf of
>> Karl Vacek <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
>> >>>>
>> >>>> Last time I sharpened my 21=E2=80=9D walk-behind mower blade I thou=
ght of
>> something that=E2=80=99s never occurred to me, after using the same bran=
d of mower
>> for 25 years..
>> >>>>
>> >>>> On a Snapper, the blade can actually go on any way onto the square
>> adapter keyed to the crankshaft. The mounting point is square, no pins,=
no
>> longer side, nothing.
>> >>>>
>> >>>> One way would be aligned with the cylinder at TDC/BDC, and the othe=
r
>> way would be across. It=E2=80=99s been off many times and there=E2=80=
=99s no way to tell
>> how it was mounted originally. The manual is silent on this.
>> >>>>
>> >>>> Power stroke shouldn=E2=80=99t matter, but maybe some dynamic issue=
one way
>> or the other?
>> >>>>
>> >>>> Thanks!
>> >>>> Karl
>> >>>>
>> >>> _______________________________________________
>> >>>
>> >>> Shop-talk@autox.team.net
>> >>> Donate: http://www.team.net/donate.html
>> >>> Suggested annual donation $12.96
>> >>> Archive: http://www.team.net/pipermail/shop-talk
>> http://autox.team.net/archive
>> >>>
>> >>> Unsubscribe/Manage:
>> http://autox.team.net/mailman/options/shop-talk/dirtbeard@gmail.com
>> >>>
>> >> _______________________________________________
>> >>
>> >> Shop-talk@autox.team.net
>> >> Donate: http://www.team.net/donate.html
>> >> Suggested annual donation $12.96
>> >> Archive: http://www.team.net/pipermail/shop-talk
>> http://autox.team.net/archive
>> >>
>> >> Unsubscribe/Manage:
>> http://autox.team.net/mailman/options/shop-talk/tjcora@icloud.com
>> >>
>> > _______________________________________________
>> >
>> > Shop-talk@autox.team.net
>> > Donate: http://www.team.net/donate.html
>> > Suggested annual donation $12.96
>> > Archive: http://www.team.net/pipermail/shop-talk
>> http://autox.team.net/archive
>> >
>> > Unsubscribe/Manage:
>> http://autox.team.net/mailman/options/shop-talk/bspidell@comcast.net
>> >
>>
>> _______________________________________________
>>
>> Shop-talk@autox.team.net
>> Donate: http://www.team.net/donate.html
>> Suggested annual donation $12.96
>> Archive: http://www.team.net/pipermail/shop-talk
>> http://autox.team.net/archive
>>
>> Unsubscribe/Manage:
>> http://autox.team.net/mailman/options/shop-talk/fishplate@gmail.com
>>
>> _______________________________________________
>
> Shop-talk@autox.team.net
> Donate: http://www.team.net/donate.html
> Suggested annual donation $12.96
> Archive: http://www.team.net/pipermail/shop-talk
> http://autox.team.net/archive
>
> Unsubscribe/Manage:
> http://autox.team.net/mailman/options/shop-talk/jdinnis@gmail.com
>
>
--=20
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D
=3D Never offend people with style when you =3D
=3D can offend with substance --- Sam Brown =3D
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D
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Content-Transfer-Encoding: quoted-printable
<div dir=3D"ltr">The whole propeller thing is really overstated.=C2=A0 It i=
s just there to keep the pilot cool.=C2=A0 If the propeller stops turning, =
the pilot often begins sweating. <br></div><br><div class=3D"gmail_quote"><=
div dir=3D"ltr" class=3D"gmail_attr">On Wed, May 19, 2021 at 5:15 AM Jeff S=
carbrough <<a href=3D"mailto:fishplate@gmail.com";>fishplate@gmail.com</a=
>> wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0px=
0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><di=
v dir=3D"auto">Not to mention that there are two magnetos.=C2=A0 You don=
9;t want your lawn mower quitting in mid-air.</div><br><div class=3D"gmail_=
quote"><div dir=3D"ltr" class=3D"gmail_attr">On Tue, May 18, 2021, 23:15 Bo=
b Spidell <<a href=3D"mailto:bspidell@comcast.net"; rel=3D"noreferrer" ta=
rget=3D"_blank">bspidell@comcast.net</a>> wrote:<br></div><blockquote cl=
ass=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid=
rgb(204,204,204);padding-left:1ex">Magnetos still power the vast majority =
of small aircraft piston engines; <br>
they're a bit more complicated though. Mags in good nick will throw a <=
br>
really hot spark; they're always 'hot' and the only way to disa=
ble them <br>
is to ground the primary coil by a 'P lead.'<br>
<br>
On 5/18/2021 8:03 PM, Thomas Coradeschi wrote:<br>
> You=E2=80=99re almost certainly looking at a magneto ignition system i=
n all of those small engines=E2=80=A6 Bog simple indeed!<br>
><br>
> =E2=80=94<br>
> Tom Coradeschi<br>
> <a href=3D"mailto:tjcora@icloud.com"; rel=3D"noreferrer noreferrer" tar=
get=3D"_blank">tjcora@icloud.com</a><br>
><br>
><br>
>> On 18 May 2021, at 10:53 PM, Bob Spidell <<a href=3D"mailto:bsp=
idell@comcast.net" rel=3D"noreferrer noreferrer" target=3D"_blank">bspidell=
@comcast.net</a>> wrote:<br>
>><br>
>> re: "... they are using iron mass of the blade as part of the=
inductance field to signal the position for coil firing ..."<br>
>><br>
>> That was my guess, based on what they told me; the motor was other=
wise in good shape (how I managed to get it back together still amazes me).=
IIRC, it was a Tecumseh 5HP engine. The name of the shop was 'Knife St=
alkers.'<br>
>><br>
>> I'm looking into possibly rebuilding a couple chainsaw motors,=
the coil and 'points,' or whatever solid state switch they are usi=
ng, are very simplistic. There may be a magnet in the crank gear to trigger=
the spark. I use Pertronix in several cars and, except for one they have a=
cap on the distributor cam with magnets to fire the electronic switch. Sur=
prising to me, the one on my 4-cyl Austin-Healey doesn't use the cap, a=
pparently the lobes on the distributor cam are sufficient to fire the Hall =
Effect sensor.<br>
>><br>
>> bs<br>
>><br>
>> On 5/18/2021 7:38 PM, old dirtbeard wrote:<br>
>>> Hi Bob,<br>
>>><br>
>>> I believe you, of course, but I have never heard this before.=
=C2=A0 I have a Craftsman 21" walk behind and I usually sharpen the bl=
ade and do maintenance this month, so I think I will see if the engine will=
fire with the blade removed for sharpening.<br>
>>><br>
>>> For this to make sense to me, there would need to be some sens=
or on the blade, or they are using iron mass of the blade as part of the in=
ductance field to signal the position for coil firing. The aluminum sump of=
the motor protrudes through the steel deck of the mower, so I suppose it i=
s possible. There is quite an air gap between the blade and the sump of the=
engine, however.<br>
>>><br>
>>> You have me very curious and I will let you know if the mower =
will fire 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 t=
he crankshaft).<br>
>>><br>
>>> best,<br>
>>><br>
>>> doug<br>
>>><br>
>>> On Tue, May 18, 2021 at 5:35 PM Bob Spidell <<a href=3D"mai=
lto:bspidell@comcast.net" rel=3D"noreferrer noreferrer" target=3D"_blank">b=
spidell@comcast.net</a>> wrote:<br>
>>> Possibly of some interest: I had a Craftsman walk-behind that =
quit running suddenly. I tore the engine down, didn't find anything, th=
en finally took it to a repair shop. They told me the blade had a crack in =
it that caused the problem;=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0=
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>
>>><br>
>>> Bob<br>
>>><br>
>>> On 5/18/2021 2:55 PM, Brian and Wendy Warrick wrote:<br>
>>>> 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 de=
signed the adapter differently.<br>
>>>><br>
>>>> Brian<br>
>>>> Nampa, ID<br>
>>>><br>
>>>> From: Shop-talk <<a href=3D"mailto:shop-talk-bounces@au=
tox.team.net" rel=3D"noreferrer noreferrer" target=3D"_blank">shop-talk-bou=
nces@autox.team.net</a>> on behalf of Karl Vacek <<a href=3D"mailto:s=
tearman809@gmail.com" rel=3D"noreferrer noreferrer" target=3D"_blank">stear=
man809@gmail.com</a>><br>
>>>> Sent: Tuesday, May 18, 2021 3:52 PM<br>
>>>> To: '<a href=3D"mailto:shop-talk@autox.team.net"; rel=
=3D"noreferrer noreferrer" target=3D"_blank">shop-talk@autox.team.net</a>&#=
39; <<a href=3D"mailto:Shop-talk@autox.team.net"; rel=3D"noreferrer noref=
errer" target=3D"_blank">Shop-talk@autox.team.net</a>><br>
>>>> Subject: [Shop-talk] Mower blade orientaaion relative to p=
iston<br>
>>>>=C2=A0 =C2=A0<br>
>>>> Last time I sharpened my 21=E2=80=9D walk-behind mower bla=
de I thought of something that=E2=80=99s never occurred to me, after using =
the same brand of mower for 25 years..<br>
>>>>=C2=A0 =C2=A0<br>
>>>> On a Snapper, the blade can actually go on any way onto th=
e square adapter keyed to the crankshaft.=C2=A0 The mounting point is squar=
e, no pins, no longer side, nothing.<br>
>>>>=C2=A0 =C2=A0<br>
>>>> 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 man=
ual is silent on this.<br>
>>>>=C2=A0 =C2=A0<br>
>>>> Power stroke shouldn=E2=80=99t matter, but maybe some dyna=
mic issue one way or the other?<br>
>>>>=C2=A0 =C2=A0<br>
>>>> Thanks!<br>
>>>> Karl<br>
>>>><br>
>>> _______________________________________________<br>
>>><br>
>>> <a href=3D"mailto:Shop-talk@autox.team.net"; rel=3D"noreferrer =
noreferrer" target=3D"_blank">Shop-talk@autox.team.net</a><br>
>>> Donate: <a href=3D"http://www.team.net/donate.html"; rel=3D"nor=
eferrer noreferrer noreferrer" target=3D"_blank">http://www.team.net/donate=
.html</a><br>
>>> Suggested annual donation=C2=A0 $12.96<br>
>>> Archive: <a href=3D"http://www.team.net/pipermail/shop-talk"; r=
el=3D"noreferrer noreferrer noreferrer" target=3D"_blank">http://www.team.n=
et/pipermail/shop-talk</a> <a href=3D"http://autox.team.net/archive"; rel=3D=
"noreferrer noreferrer noreferrer" target=3D"_blank">http://autox.team.net/=
archive</a><br>
>>><br>
>>> Unsubscribe/Manage: <a href=3D"http://autox.team.net/mailman/o=
ptions/shop-talk/dirtbeard@gmail.com" rel=3D"noreferrer noreferrer noreferr=
er" target=3D"_blank">http://autox.team.net/mailman/options/shop-talk/dirtb=
eard@gmail.com</a><br>
>>><br>
>> _______________________________________________<br>
>><br>
>> <a href=3D"mailto:Shop-talk@autox.team.net"; rel=3D"noreferrer nore=
ferrer" target=3D"_blank">Shop-talk@autox.team.net</a><br>
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>> Suggested annual donation=C2=A0 $12.96<br>
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chive</a><br>
>><br>
>> Unsubscribe/Manage: <a href=3D"http://autox.team.net/mailman/optio=
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ud.com</a><br>
>><br>
> _______________________________________________<br>
><br>
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_______________________________________________<br>
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</blockquote></div><br clear=3D"all"><br>-- <br><div dir=3D"ltr" class=3D"g=
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Archive: http://www.team.net/pipermail/shop-talk http://autox.team.net/archive
--===============5301077647160729811==--
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