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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 in=
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 otherwise
> 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 coi=
l
> and 'points,' or whatever solid state switch they are using, 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. Surprising to
> me, the one on my 4-cyl Austin-Healey doesn't use the cap, apparently the
> lobes on the distributor cam are sufficient to fire the Hall Effect senso=
r.
> >>
> >> 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 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 will fire wit=
h
> 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 sum=
p
> 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 i=
t
> 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.
> >>>
> >>> 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 thoug=
ht of
> something that=E2=80=99s never occurred to me, after using the same brand=
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 other
> way would be across. It=E2=80=99s been off many times and there=E2=80=99=
s 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
>
>
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<div dir=3D"auto">Not to mention that there are two magnetos.=C2=A0 You don=
't want your lawn mower quitting in mid-air.</div><br><div class=3D"gma=
il_quote"><div dir=3D"ltr" class=3D"gmail_attr">On Tue, May 18, 2021, 23:15=
Bob Spidell <<a href=3D"mailto:bspidell@comcast.net"; target=3D"_blank" =
rel=3D"noreferrer">bspidell@comcast.net</a>> wrote:<br></div><blockquote=
class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc soli=
d;padding-left:1ex">Magnetos still power the vast majority of small aircraf=
t 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>
>> Donate: <a href=3D"http://www.team.net/donate.html"; rel=3D"norefer=
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l</a><br>
>> 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>
> <a href=3D"mailto:Shop-talk@autox.team.net"; rel=3D"noreferrer noreferr=
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><br>
<br>
_______________________________________________<br>
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</blockquote></div>
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_______________________________________________
Shop-talk@autox.team.net
Archive: http://www.team.net/pipermail/shop-talk http://autox.team.net/archive
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