Proping Question

[Doug Palmer]

Several pilots found themselves in a debate at our field yesterday. The
issue is weather it is safer to move the propeller on a (parked) aircraft in
the direction of usual engine rotation, or opposite usual rotation. This is
assuming that the propeller needs to move for some reason.

The reasonings ranged from "you should not turn an engine backwards" to
"turning the engine backwards disarms the impulse coupling", to several
issues in between.

Any thoughts from the groups collective wisdom?

[Steven P. McNicoll]

"Doug Palmer" > wrote in message
ink.net...
>
> Several pilots found themselves in a debate at our field yesterday. The
> issue is weather it is safer to move the propeller on a (parked) aircraft
> in the direction of usual engine rotation, or opposite usual rotation.
> This is assuming that the propeller needs to move for some reason.
>
> The reasonings ranged from "you should not turn an engine backwards" to
> "turning the engine backwards disarms the impulse coupling", to several
> issues in between.
>
> Any thoughts from the groups collective wisdom?

There is potential for damage to a vacuum pump if turned backward.

[Ron Natalie]

Doug Palmer wrote:

> The reasonings ranged from "you should not turn an engine backwards" to
> "turning the engine backwards disarms the impulse coupling", to several
> issues in between.
>

It doesn't "disarm" it, it just won't fire. This means than the engine
is less likely to start if the mags are hot (since the impulse coupling
aids in the starting). However, NEVER trust a propeller. Even turning
them backwards can generate a spark and even if the engine doesn't start
it can kick the prop over enough to do damage.

The argument against it is that people claim it hurts the vacuum pump.
While some dry pumps are designed to only turn one way, that's at
operating speed. The vanes are in there loose enough when it's
not spinning to not be a problem.

Except when absolutely necessary (like to get the tow bar connected)
you shouldn't be turning the prop at all. There's no good reason to
justify the dangers.

[Peter Dohm]

>
> Except when absolutely necessary (like to get the tow bar connected)
> you shouldn't be turning the prop at all. There's no good reason to
> justify the dangers.

Partly, just to be a smart-ass, and also looking at the geometry, that could
be one of the worst times to turn the prop...


In reality, as already pointed out, that is one of the times when it could
be necessary. At the very least, I would verify that all controls
(especially throttle and mixture) are all the way back and that all
appropriate switches are off--and then try to stay out of the prop arc while
working. That should minimize the personal danger and (hopefully) eliminate
the possibility of one of those "Voracious Airplane Eats Tractor" type
accidents that circulate forever on the internet.

Peter

[Dudley Henriques[_2_]]

"Doug Palmer" > wrote in message
ink.net...
> Several pilots found themselves in a debate at our field yesterday. The
> issue is weather it is safer to move the propeller on a (parked) aircraft
> in the direction of usual engine rotation, or opposite usual rotation.
> This is assuming that the propeller needs to move for some reason.
>
> The reasonings ranged from "you should not turn an engine backwards" to
> "turning the engine backwards disarms the impulse coupling", to several
> issues in between.
>
> Any thoughts from the groups collective wisdom?

This is one issue where you don't want to get bogged down in the
technicalities involving vacuum pumps and impulse couplings.
The bottom line on this issue is that you should NEVER.....EVER...... trust
a propeller not to kill you if you turn it by hand IN EITHER DIRECTION while
it's attached to the airplane.
Dudley Henriques

[Mark T. Dame]

Ron Natalie wrote:
>
> The argument against it is that people claim it hurts the vacuum pump.

That was what I was taught many moons ago. I have never confirmed it,
but my brain tells me that the engine is designed to turn in one
direction, so don't turn it in the other. No real proof (I'm not an A&P
and have never played one on TV), but just my own logic.


> Except when absolutely necessary (like to get the tow bar connected)
> you shouldn't be turning the prop at all. There's no good reason to
> justify the dangers.

If the engine is properly shutdown (boost pump off, throttle slightly
above idle, and mixture to cut off) the chances are greatly reduced than
if you just kill the engine by turn off the mags. Additionally, some
people recommend checking your mags before shutdown to make sure you
don't have a broken P lead which would also help. A flying club I used
to belong to had a "policy" (not a rule, just a suggestion that it would
be nice if you did it) of turning the prop vertical after parking it to
keep the birds from sitting on it and pooing on the plane.

Obviously the safest way to prevent an accidental fire while hand
turning the prop is to not do it. When I do turn a prob by hand, I try
to do it in the direction it turns while running, turn slowly to
minimize any compression (don't know if that is true either, just what I
was taught), and only use the palms of my hand on the face of the prop
to minimize the possibility of the prop smacking the back of my hand
should it fire. YMMV.


-m
--
## Mark T. Dame >
## CP-ASEL, AGI
## <insert tail number here>
## KHAO, KISZ
"A programmer and his mind are soon parted."

[[email protected]]

The magneto cannot generate a spark when turned slowly
backward, and it's not just because the impulse coupling doesn't work
backwards. The magnet could generate a flow in the primary winding,
but the points are closing rather than opening at the right time and
the arresting of the flow, a requirement for spark, isn't there.
Further, the distributor is geared to send a spark to a cylinder based
on a particular direction, and turning some reversible mags backward
can generate a spark but it happens when the distributor finger is in
the wrong place. Besides, the mag has to be turning at a good clip to
make any spark without the impulse coupling.
Worn-out vacuum pumps could indeed fail if turned
backward, but they don't belong on the airplane anyway. We use the
pumps with the wear inspection ports so that they never get to that
vulnerable stage. A good pump can be turned backward without fear of
breaking anything.
So we teach our students to turn the prop backward, but
that it must be done with great caution as a matter of course. Most of
them don't understand magnetos or engines or anything else and might
someday turn the thing in the wrong direction, and you have to make
such rules so that they learn that props can kill and so they will
keep their friends from fooling with it. We never lose a vacuum pump,
have never had an inadvertent firing. The most dangerous time is right
after the engine is shut down, when hot carbon in the cylinder head
could fire any vapors still present. We also check the mag grounding
at idle just before mixture cutoff.

Dan

[Barry]

> A flying club I used to belong to had a "policy" (not a rule, just a
> suggestion that it would be nice if you did it) of turning the prop vertical
> after parking it to keep the birds from sitting on it and pooing on the
> plane.

We turn the prop vertical in the winter to prevent water from pooling inside
the spinner and then freezing into a block of ice. This happened to me once,
and the vibration it caused was impressive. We shut down, pulled the plane
into a heated hangar, turned the prop vertical, and waited for the ice to melt
and drain out.

[Orval Fairbairn]

In article >,
"Dudley Henriques" > wrote:

> "Doug Palmer" > wrote in message
> ink.net...
> > Several pilots found themselves in a debate at our field yesterday. The
> > issue is weather it is safer to move the propeller on a (parked) aircraft
> > in the direction of usual engine rotation, or opposite usual rotation.
> > This is assuming that the propeller needs to move for some reason.
> >
> > The reasonings ranged from "you should not turn an engine backwards" to
> > "turning the engine backwards disarms the impulse coupling", to several
> > issues in between.
> >
> > Any thoughts from the groups collective wisdom?
>
> This is one issue where you don't want to get bogged down in the
> technicalities involving vacuum pumps and impulse couplings.
> The bottom line on this issue is that you should NEVER.....EVER...... trust
> a propeller not to kill you if you turn it by hand IN EITHER DIRECTION while
> it's attached to the airplane.
> Dudley Henriques

Some engines (I'm thinking Rotax in particular) are highly allergic to
turning the prop backwards. On a Rotax, it introduces air into the oil
galleys, which can result in premature engine failure.

I subscribe to the following precautions:

1. Check mag grounding prior to shutdown.

2. shut down with idle cutoff and throttle at idle.

3. If you turn the prop, do so in a way that it will not strike either
you or anything (or anyone else) if it kicks off.

I actually had a prop hit me from residual compression (no ignition) one
time.

[B A R R Y[_2_]]

Barry wrote:
>
> We turn the prop vertical in the winter to prevent water from pooling inside
> the spinner and then freezing into a block of ice. This happened to me once,
> and the vibration it caused was impressive. We shut down, pulled the plane
> into a heated hangar, turned the prop vertical, and waited for the ice to melt
> and drain out.
>


As do we.

Same name, same reason. <G>

[Newps]

The engine is not designed to turn in a specific direction. Some
accessories are, such as mags, vacuum pumps, starter, alternator. The
engine itself will happily run in the other direction, several twins do
just that.



Mark T. Dame wrote:

> Ron Natalie wrote:
>
>>
>> The argument against it is that people claim it hurts the vacuum pump.
>
>
> That was what I was taught many moons ago. I have never confirmed it,
> but my brain tells me that the engine is designed to turn in one
> direction, so don't turn it in the other. No real proof (I'm not an A&P
> and have never played one on TV), but just my own logic.
>
>
>> Except when absolutely necessary (like to get the tow bar connected)
>> you shouldn't be turning the prop at all. There's no good reason to
>> justify the dangers.
>
>
> If the engine is properly shutdown (boost pump off, throttle slightly
> above idle, and mixture to cut off) the chances are greatly reduced than
> if you just kill the engine by turn off the mags. Additionally, some
> people recommend checking your mags before shutdown to make sure you
> don't have a broken P lead which would also help. A flying club I used
> to belong to had a "policy" (not a rule, just a suggestion that it would
> be nice if you did it) of turning the prop vertical after parking it to
> keep the birds from sitting on it and pooing on the plane.
>
> Obviously the safest way to prevent an accidental fire while hand
> turning the prop is to not do it. When I do turn a prob by hand, I try
> to do it in the direction it turns while running, turn slowly to
> minimize any compression (don't know if that is true either, just what I
> was taught), and only use the palms of my hand on the face of the prop
> to minimize the possibility of the prop smacking the back of my hand
> should it fire. YMMV.
>
>
> -m

[Peter Dohm]

"Barry" > wrote in message
...
> > A flying club I used to belong to had a "policy" (not a rule, just a
> > suggestion that it would be nice if you did it) of turning the prop
vertical
> > after parking it to keep the birds from sitting on it and pooing on the
> > plane.
>
> We turn the prop vertical in the winter to prevent water from pooling
inside
> the spinner and then freezing into a block of ice. This happened to me
once,
> and the vibration it caused was impressive. We shut down, pulled the
plane
> into a heated hangar, turned the prop vertical, and waited for the ice to
melt
> and drain out.
>
>
Interesting, and worth remembering.

There is also a much older version of the advise--recommending that wooden
props be left horizontal when parked for long periods so that moisture in
the wood will not migrate to one blade, causing an imbalance.

Peter

[Andrew Sarangan]

On May 15, 10:59 am, "Mark T. Dame" > wrote:
> Ron Natalie wrote:
>
> > The argument against it is that people claim it hurts the vacuum pump.
>
> That was what I was taught many moons ago. I have never confirmed it,
> but my brain tells me that the engine is designed to turn in one
> direction, so don't turn it in the other. No real proof (I'm not an A&P
> and have never played one on TV), but just my own logic.
>
> > Except when absolutely necessary (like to get the tow bar connected)
> > you shouldn't be turning the prop at all. There's no good reason to
> > justify the dangers.
>
> If the engine is properly shutdown (boost pump off, throttle slightly
> above idle, and mixture to cut off) the chances are greatly reduced than
> if you just kill the engine by turn off the mags. Additionally, some
> people recommend checking your mags before shutdown to make sure you
> don't have a broken P lead which would also help. A flying club I used
> to belong to had a "policy" (not a rule, just a suggestion that it would
> be nice if you did it) of turning the prop vertical after parking it to
> keep the birds from sitting on it and pooing on the plane.
>
> Obviously the safest way to prevent an accidental fire while hand
> turning the prop is to not do it. When I do turn a prob by hand, I try
> to do it in the direction it turns while running, turn slowly to
> minimize any compression (don't know if that is true either, just what I
> was taught), and only use the palms of my hand on the face of the prop
> to minimize the possibility of the prop smacking the back of my hand
> should it fire. YMMV.
>

Although I agree with the dangers of accidental engine starts, what I
would like to know if there really have been any cases of inadvertant
engines starts when the prop is turned half a rotation with the
mixture in cut-off even if the magnetos were on. All the cases I am
aware of are related to hand-propping, which is not the same as
turning the prop to reposition the blades.

[Robert M. Gary]

On May 15, 5:59 am, "Doug Palmer" > wrote:
> Several pilots found themselves in a debate at our field yesterday. The
> issue is weather it is safer to move the propeller on a (parked) aircraft in
> the direction of usual engine rotation, or opposite usual rotation. This is
> assuming that the propeller needs to move for some reason.
>
> The reasonings ranged from "you should not turn an engine backwards" to
> "turning the engine backwards disarms the impulse coupling", to several
> issues in between.
>
> Any thoughts from the groups collective wisdom?

Of course turning it backward may damage the vac pump but I've never
flown a hand prop'ped airplane that had a vac system.
The problem with turning it backwards is that it can still on forward.
If you turn it and stop near the compression, it will then turn back
the other way. So, either way assume its hot.
Once you've been flying a hand propped airplane for awhile you will
realize that it is not safe or reasonable to use a full body kick
every time you turn the prop. So I would pull the prop through with an
open palm hand such that if the prop did start I would be ok (some of
the old guys actually start the plane this way). Then, when its time
to start, I hit the mags and do a full kick. If you primed the engine
correctly it should only take about an 1/8 of a turn for it to fire.
BTW: I would never hand prop a nosewheel plane.

-Robert

[Robert M. Gary]

On May 15, 8:20 am, wrote:
We also check the mag grounding
> at idle just before mixture cutoff.
>
> Dan

What type of plane are you handpropping that has mixture cutoff? Must
not be the traditional Stromburg carb.

-Robert

[Maxwell]

"Newps" > wrote in message
. ..
>>
>> If the engine is properly shutdown (boost pump off, throttle slightly
>> above idle, and mixture to cut off) the chances are greatly reduced than
>> if you just kill the engine by turn off the mags. Additionally, some
>> people recommend checking your mags before shutdown to make sure you
>> don't have a broken P lead which would also help. A flying club I used
>> to belong to had a "policy" (not a rule, just a suggestion that it would
>> be nice if you did it) of turning the prop vertical after parking it to
>> keep the birds from sitting on it and pooing on the plane.
>>
>> Obviously the safest way to prevent an accidental fire while hand turning
>> the prop is to not do it. When I do turn a prob by hand, I try to do it
>> in the direction it turns while running, turn slowly to minimize any
>> compression (don't know if that is true either, just what I was taught),
>> and only use the palms of my hand on the face of the prop to minimize the
>> possibility of the prop smacking the back of my hand should it fire.
>> YMMV.
>>

That's only true with 2 cyclce engines, even then, ignition timing is a
factor. The rotational derection of a 4 cycle engine is determined by the
cam, valve and ignition timing. Twin engine aircraft with counter rotating
props/engines have beend designed specifically to do so. The engines as a
whole, are not interchangable.

[Mark T. Dame]

Robert M. Gary wrote:
> BTW: I would never hand prop a nosewheel plane.

Personally, I wouldn't hand prop any plane. I got too many nicks and
cuts as a kid finger propping model airplanes. (-:

Which reminds me of a story. One winter a few years ago the FBO had a
152 that was being stubborn in the cold weather, so one of the line guys
helped out by hand propping it for the pilot. He was wearing gloves and
when the plane started, one of his gloves came off. The prop threw the
glove about 30 feet and the pilot freaked out because he thought the
guy's hand was still in the glove! He shut the engine down to check on
him. The line guy wasn't happy about having to hand prop it again...


-m
--
## Mark T. Dame >
## CP-ASEL, AGI
## <insert tail number here>
## KHAO, KISZ
"In accord with UNIX philosophy, Perl gives you enough rope to
hang yourself."
-- Programming perl, Larry Wall and Randal L. Schwartz

[Jim Stewart]

Doug Palmer wrote:
> Several pilots found themselves in a debate at our field yesterday. The
> issue is weather it is safer to move the propeller on a (parked) aircraft in
> the direction of usual engine rotation, or opposite usual rotation. This is
> assuming that the propeller needs to move for some reason.
>
> The reasonings ranged from "you should not turn an engine backwards" to
> "turning the engine backwards disarms the impulse coupling", to several
> issues in between.
>
> Any thoughts from the groups collective wisdom?

Never, ever turn a Rotax 912/914 backwards. It
will break the suction in the oil line. To regain
oil pressure you have to undo oil lines and refill
them.

[JGalban via AviationKB.com]

Robert M. Gary wrote:
>BTW: I would never hand prop a nosewheel plane.
>

Just out of curiosity, why does a nosewheel make a difference?

I used to have an old 172 (with the cheesey 20 amp generator) that required
a handprop after most night flights. I didn't seem any different than
handpropping a tailwheel equiped 170.

John Galban=====>N4BQ (PA28-180)

--
Message posted via AviationKB.com
http://www.aviationkb.com/Uwe/Forums.aspx/aviation/200705/1

[Peter Dohm]

"Robert M. Gary" > wrote in message
ps.com...
> On May 15, 8:20 am, wrote:
> We also check the mag grounding
> > at idle just before mixture cutoff.
> >
> > Dan
>
> What type of plane are you handpropping that has mixture cutoff? Must
> not be the traditional Stromburg carb.
>
> -Robert
>
This could be just a nomenclature issue. I was taught to call the lean
position of the mixture control "idle cut off" even though it really doesn't
cut anything off. However, it is too lean to keep the engine running at
1000 rpm.

I'm curious about what others think

Peter

[Robert M. Gary]

On May 15, 2:08 pm, "Peter Dohm" > wrote:
> "Robert M. Gary" > wrote in glegroups.com...> On May 15, 8:20 am, wrote:
> > We also check the mag grounding
> > > at idle just before mixture cutoff.
>
> > > Dan
>
> > What type of plane are you handpropping that has mixture cutoff? Must
> > not be the traditional Stromburg carb.
>
> > -Robert
>
> This could be just a nomenclature issue. I was taught to call the lean
> position of the mixture control "idle cut off" even though it really doesn't
> cut anything off. However, it is too lean to keep the engine running at
> 1000 rpm.
>
> I'm curious about what others think
>
> Peter

In the C140, the Aeronca, and the J-3 the carbs (probably all
Stromburg), pulling the mixture all the way out at idle had no effect
at all on the engine. The mixture control only affected the engine at
power.

-Robert

[JGalban via AviationKB.com]

Robert M. Gary wrote:
>
>In the C140, the Aeronca, and the J-3 the carbs (probably all
>Stromburg), pulling the mixture all the way out at idle had no effect
>at all on the engine. The mixture control only affected the engine at
>power.
>

With the Marvel-Schebler carbs found on the average (post 1950s) light
singles, pulling the mixture all the way back will cut off fuel to the idle
circuit as well as the main jet.

John Galban=====>N4BQ (PA28-180)

--
Message posted via AviationKB.com
http://www.aviationkb.com/Uwe/Forums.aspx/aviation/200705/1

[Morgans[_2_]]

"Robert M. Gary" > wrote

> BTW: I would never hand prop a nosewheel plane.

I think I know the reason for this opinion, but I would still be interested
in hearing your reasoning.

Why no hand propping a nose dragger for you?
--
Jim in NC

[[email protected]]

On May 15, 10:21 am, "Robert M. Gary" > wrote:
> On May 15, 8:20 am, wrote:
> We also check the mag grounding
>
> > at idle just before mixture cutoff.
>
> > Dan
>
> What type of plane are you handpropping that has mixture cutoff? Must
> not be the traditional Stromburg carb.
>
> -Robert

We were talking about turning the prop backward to reposition
it, not handpropping to start it. All our training airplanes have
starters and idle cutoff mixture controls. My own old Jodel with its
A-65 has to be handpropped, and has the old Stromberg with cruise
mixture control that has no effect on idle mixture. I shut the fuel
off and wait a bit for the bowl to run dry when I shut it down.

Dan

[[email protected]]

On May 15, 10:02 am, Newps > wrote:
> The engine is not designed to turn in a specific direction. Some
> accessories are, such as mags, vacuum pumps, starter, alternator. The
> engine itself will happily run in the other direction, several twins do
> just that.

That backward-running engine has a different camshaft, mags and
oil pump to allow it to run that way. Engines won't run backwards just
because we try to start them backwards. The intake/compression/power/
exhaust strokes MUST happen in that order, and a backward-turned
engine has them all messed up.

Dan

[[email protected]]

On May 15, 10:18 am, Andrew Sarangan > wrote:

>
> Although I agree with the dangers of accidental engine starts, what I
> would like to know if there really have been any cases of inadvertant
> engines starts when the prop is turned half a rotation with the
> mixture in cut-off even if the magnetos were on. All the cases I am
> aware of are related to hand-propping, which is not the same as
> turning the prop to reposition the blades.- Hide quoted text -
>
> - Show quoted text -

Yes, engines have hurt people. You can kill it with the idle
mixture cutoff, but if someone has fooled with the primer (or boost
pump on an injected system), fuel will be present and any spark could
set it off. An example is a failed start attempt, due either to a
flooded engine or cold weather. That prop will be dangerous with the
mags on. Turning it forward is insane.

Dan

[[email protected]]

On May 15, 4:11 pm, wrote:
> On May 15, 10:02 am, Newps > wrote:
>
> > The engine is not designed to turn in a specific direction. Some
> > accessories are, such as mags, vacuum pumps, starter, alternator. The
> > engine itself will happily run in the other direction, several twins do
> > just that.
>
> That backward-running engine has a different camshaft, mags and
> oil pump to allow it to run that way. Engines won't run backwards just
> because we try to start them backwards. The intake/compression/power/
> exhaust strokes MUST happen in that order, and a backward-turned
> engine has them all messed up.
>
> Dan

Forgot to mention: an alternator generates just fine when run
backwards. I did it on an inboard boat I built, because there was no
room in that tight compartment for the alternator to sit alonside the
engine in its usual spot and had to be mounted backwards in front. An
alternator generates alternating curent that is internally rectified,
and the direction of rotor rotation is irrelevant. The only
consideration is the cooling fan blade angle; installing an older fan
with straight radial blades solves the problem.
The DC generator must be turned in one direction only.

Dan

[Ron Natalie]

Andrew Sarangan wrote:

>
> Although I agree with the dangers of accidental engine starts, what I
> would like to know if there really have been any cases of inadvertant
> engines starts when the prop is turned half a rotation with the
> mixture in cut-off even if the magnetos were on. All the cases I am
> aware of are related to hand-propping, which is not the same as
> turning the prop to reposition the blades.

Start no, kick over a turn or two, yes. Even with the engine cut
off with the mixture, there can end up with just enough fuel in the
system to fire the thing over a turn. I've had it happen on a 172N
we had in the club.

[EridanMan]

Interesting topic, interesting discussion... but if I may expand on
the original question a bit?

The Original piper POH that came with my bird ('67 PA-28-140) actually
recommends that that prop be pulled through two complete rotations
backwards any time the engine is started after sitting for a long time
(it actually says its a good idea for every flight, but should be
mandatory any time the engine's been sitting for a while).

I've NEVER heard or seen this advice anywhere else... I've never
practiced it... It seems almost insane to me... but the book says
what the book says.

Anyone have any clue why?

I can get the exact wording tpmogjt ... its in the 'preflight and
takeoff' section of the book.

[TheSmokingGnu]

Andrew Sarangan wrote:
> Although I agree with the dangers of accidental engine starts, what I
> would like to know if there really have been any cases of inadvertant
> engines starts when the prop is turned half a rotation with the
> mixture in cut-off even if the magnetos were on.

Early in my piloting career, while my instructor deftly distracted me
with questions about the cruising speed of an unladen swallow, I managed
to turn the mags off before pulling the engine to cutoff, so that it
stopped because the ignition died. Spotting my mistake, my instructor
asked me to run the starter over, and the engine gleefully spat to life
on the very first blade, and ran for another 5-10 seconds.

Then he asked me if I wouldn't mind terribly putting the plane away myself.

Take any aircraft X and put renter A before you who does something
similar but doesn't catch the mistake, and you too can become another
statistic by trusting that the prop is dead, that the p-lead works, and
that the cylinders are dry.

TheSmokingGnu

[Private]

"Andrew Sarangan" > wrote in message
oups.com...
snip
>
> Although I agree with the dangers of accidental engine starts, what I
> would like to know if there really have been any cases of inadvertant
> engines starts when the prop is turned half a rotation with the
> mixture in cut-off even if the magnetos were on. All the cases I am
> aware of are related to hand-propping, which is not the same as
> turning the prop to reposition the blades.

I had a friend who claimed that he had a warm engine start in his hangar
when he repositioned the prop. The hanger door was closed and he had
nowhere to go. Claimed his back was against the door and he held his hand
on the center of the spinner to stop the aircraft from moving forward.
Luckily the fuel was shutoff and it only ran for a very short time. I
forget where the gas came from. He may have been spinning a tale but he
really wasn't that kind of guy.

Happy landings.

[Don Poitras]

In rec.aviation.student EridanMan > wrote:
> Interesting topic, interesting discussion... but if I may expand on
> the original question a bit?

> The Original piper POH that came with my bird ('67 PA-28-140) actually
> recommends that that prop be pulled through two complete rotations
> backwards any time the engine is started after sitting for a long time
> (it actually says its a good idea for every flight, but should be
> mandatory any time the engine's been sitting for a while).

> I've NEVER heard or seen this advice anywhere else... I've never
> practiced it... It seems almost insane to me... but the book says
> what the book says.

> Anyone have any clue why?

> I can get the exact wording tpmogjt ... its in the 'preflight and
> takeoff' section of the book.

My 63 Musketeer (BE-23) POH says the same thing:

'Always pull the propeller through by hand, opposite the direction of
rotation, several times to clear the engine and "limber up" the cold,
heavy oil before using the starter. This will also lessen the load on
the battery if external power is not used'

An old timer saw me doing that and nearly bit my head off saying that
I was going to break the vacuum pump. I felt I needed to do that in
cold weather because I was having a lot of trouble starting the
engine. I'd get maybe two revolutions before the battery died. Turned
out I needed a new starter and I had some electrical shorts too.

The vacuum pump did give up the ghost last year, but I don't think
it was related as I meekly switched to "limbering up" in the suggested
direction.

With the new starter, I don't really have any trouble starting anymore,
but I will pull it through a few times on the coldest days.

Followup set to r.a.p

--
Don Poitras

[Maxwell]

"Private" > wrote in message
news:0Ft2i.188319$aG1.182030@pd7urf3no...
>
> I had a friend who claimed that he had a warm engine start in his hangar
> when he repositioned the prop. The hanger door was closed and he had
> nowhere to go. Claimed his back was against the door and he held his hand
> on the center of the spinner to stop the aircraft from moving forward.
> Luckily the fuel was shutoff and it only ran for a very short time. I
> forget where the gas came from. He may have been spinning a tale but he
> really wasn't that kind of guy.
>

Interesting. I used to know an old timer that told the same tale.

[Cubdriver]

On Tue, 15 May 2007 12:59:05 GMT, "Doug Palmer"
> wrote:

>The reasonings ranged from "you should not turn an engine backwards" to
>"turning the engine backwards disarms the impulse coupling", to several
>issues in between.

The local airport owns two Cubs that are of course always propped. The
one I fly has impulse coupling; I think the other does as well. At
various times I've been propped by flight instructors, the airport
manager, and the airport owner. I've never moved the prop backwards
myself, but I've often seen them do it repeatedly -- I think to unload
the carb because they've flooded it with repeated pulls. I've never
heard anyone remark that it shouldn't go backwards.

However! I've never moved a prop unless someone was standing on the
brakes, and since if I'm propping the plane it's usually because the
guy at the controls is a stranger who probably knows little about
Cubs, I always prop from behind.

Blue skies! -- Dan Ford

[Cubdriver]

On 15 May 2007 14:35:47 -0700, "Robert M. Gary" >
wrote:

>In the C140, the Aeronca, and the J-3 the carbs (probably all
>Stromburg), pulling the mixture all the way out at idle had no effect
>at all on the engine.

I fly a J-3, and I've never seen one with a mixture control.

Blue skies! -- Dan Ford

[Cubdriver]

On 15 May 2007 09:19:59 -0700, "Robert M. Gary" >
wrote:

> So I would pull the prop through with an
>open palm hand such that if the prop did start I would be ok (some of
>the old guys actually start the plane this way)

That's what I was taught to do, and what I do if I'm propping from the
front (rarely). As it happens, I was 68 at the time, but my instructor
was 21. Blue skies! -- Dan Ford

[Peter Dohm]

"Private" > wrote in message
news:0Ft2i.188319$aG1.182030@pd7urf3no...
>
> "Andrew Sarangan" > wrote in message
> oups.com...
> snip
> >
> > Although I agree with the dangers of accidental engine starts, what I
> > would like to know if there really have been any cases of inadvertant
> > engines starts when the prop is turned half a rotation with the
> > mixture in cut-off even if the magnetos were on. All the cases I am
> > aware of are related to hand-propping, which is not the same as
> > turning the prop to reposition the blades.
>
> I had a friend who claimed that he had a warm engine start in his hangar
> when he repositioned the prop. The hanger door was closed and he had
> nowhere to go. Claimed his back was against the door and he held his hand
> on the center of the spinner to stop the aircraft from moving forward.
> Luckily the fuel was shutoff and it only ran for a very short time. I
> forget where the gas came from. He may have been spinning a tale but he
> really wasn't that kind of guy.
>
> Happy landings.
>
>
I hope he was wearing gloves!

Actually I have either heard or read the same story a couple of times over
the years, and I really do have my doubts.

[john smith[_2_]]

In article >,
Cubdriver <usenet AT danford DOT net> wrote:

> On 15 May 2007 14:35:47 -0700, "Robert M. Gary" >
> wrote:
>
> >In the C140, the Aeronca, and the J-3 the carbs (probably all
> >Stromburg), pulling the mixture all the way out at idle had no effect
> >at all on the engine.
>
> I fly a J-3, and I've never seen one with a mixture control.

That's because the carburetor is hard to find now a days.
The ones that out there in the fly markets are high priced and are
pretty much junk. The people selling them are hoping to find a sucker
that only has the model number and doesn't know what to look for.
I am still looking for one to put on a 7AC Champ.

[[email protected]]

On May 16, 6:40 am, john smith > wrote:
> In article >,
> Cubdriver <usenet AT danford DOT net> wrote:
>
> > On 15 May 2007 14:35:47 -0700, "Robert M. Gary" >
> > wrote:
>
> > >In the C140, the Aeronca, and the J-3 the carbs (probably all
> > >Stromburg), pulling the mixture all the way out at idle had no effect
> > >at all on the engine.
>
> > I fly a J-3, and I've never seen one with a mixture control.
>
> That's because the carburetor is hard to find now a days.
> The ones that out there in the fly markets are high priced and are
> pretty much junk. The people selling them are hoping to find a sucker
> that only has the model number and doesn't know what to look for.
> I am still looking for one to put on a 7AC Champ.

The Stromberg carb on that Cub will either have a mixture
control that's lockwired in the full rich position, or will be missing
the mixture mechanism and have a cover plate over it. My A-65 had the
cover plate, and since I was a machinist in a former life, I machined
the mixture control parts and put them in. It works fine, but I seldom
use it. The CHTs go up too much if I lean it.
The mixture control in that engine doesn't directy control
the fuel flow like the Marvel Schebler/Precision Aeromotive carb does,
and so it can't shut the fuel right off. The float bowl is vented
through a cavity in the top cover that has two other passages, one
leading to the dead airspace behind the venturi where the air pressure
is more or less ambient, and the other into the venturi itself.
Without the mixture parts installed, the venturi will draw a tiny bit
of air from the dead airspace, but not enough to drop the bowl
pressure. With a mixture control, leaning the engine reduces the
airflow from the dead airspace by gradually shutting it off, and the
venturi's much lower pressure begins to drop the atmospheric pressure
in the float bowl. Since fuel flow is dependent on the difference
between venturi pressure at the fuel nozzle and the bowl's vented
pressure, the flow decreases as the bowl's pressure comes closer to
the venturi's pressure. In other words, the venturi suction holds the
fuel back. At idle, there's not much airflow through the venturi and
it doesn't generate any suction, so the mixture has no effect on fuel
flow.
Turning a prop backwards during hand-propping reduces the
mixture ratio in the cylinders if the engine has been overprimed. Air
is drawn through the exhaust and will absorb the fuel, carrying it
back through the carb and out. The carb will often drip fuel during
such an event. Combustible mixtures range from 8:1 (rich) to 18:1
(lean), and overpriming will make the air/fuel mixture much richer
than 8:1 and the engine won't fire. When an electric starter is
available, we can pull the mixture, open the throttle and crank until
it leans out enough to catch, but when handpropping this could take
hours and cause a heart attack or something.

Dan

[george]

On May 16, 9:41 pm, Cubdriver <usenet AT danford DOT net> wrote:
> On Tue, 15 May 2007 12:59:05 GMT, "Doug Palmer"
>
> > wrote:
> >The reasonings ranged from "you should not turn an engine backwards" to
> >"turning the engine backwards disarms the impulse coupling", to several
> >issues in between.
>
> The local airport owns two Cubs that are of course always propped. The
> one I fly has impulse coupling; I think the other does as well. At
> various times I've been propped by flight instructors, the airport
> manager, and the airport owner. I've never moved the prop backwards
> myself, but I've often seen them do it repeatedly -- I think to unload
> the carb because they've flooded it with repeated pulls. I've never
> heard anyone remark that it shouldn't go backwards.
>
> However! I've never moved a prop unless someone was standing on the
> brakes, and since if I'm propping the plane it's usually because the
> guy at the controls is a stranger who probably knows little about
> Cubs, I always prop from behind.
>

I always 'walk through'.
photo is of H M Jenkins prop starting a Rallye. As he and I were the
only ones there that day who were able to take the place of starter
motors :-)
http://imagebank.org.nz/is.php?i=264&img=Harry_prop_star.jpg

[Capt. Geoffrey Thorpe]

"Cubdriver" <usenet AT danford DOT net> wrote in message
...
> On 15 May 2007 14:35:47 -0700, "Robert M. Gary" >
> wrote:
>
>>In the C140, the Aeronca, and the J-3 the carbs (probably all
>>Stromburg), pulling the mixture all the way out at idle had no effect
>>at all on the engine.
>
> I fly a J-3, and I've never seen one with a mixture control.
>

In the C-120 I flew (IIRC it was a Stromberg) the mixture lever was safety
wired in place - there was no mixture control on the panel.

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

[Robert M. Gary]

On May 16, 2:52 am, Cubdriver <usenet AT danford DOT net> wrote:
> On 15 May 2007 09:19:59 -0700, "Robert M. Gary" >
> wrote:
>
> > So I would pull the prop through with an
> >open palm hand such that if the prop did start I would be ok (some of
> >the old guys actually start the plane this way)
>
> That's what I was taught to do, and what I do if I'm propping from the
> front (rarely). As it happens, I was 68 at the time, but my instructor
> was 21. Blue skies! -- Dan Ford

I still do the full kick when I'm actually starting the engine. Even
when I was flying the float plane and propping from the back, I'd give
a kick. Of course, if you prime the 65 cont hp engines correctly they
take almost no effort to start. I can't imagine trying to start my
Mooney that way!!

-Robert

[Robert M. Gary]

On May 15, 2:47 pm, "Morgans" > wrote:
> "Robert M. Gary" > wrote
>
> > BTW: I would never hand prop a nosewheel plane.
>
> I think I know the reason for this opinion, but I would still be interested
> in hearing your reasoning.
>
> Why no hand propping a nose dragger for you?

Because the top arch of the prop is close to my head. When teaching
students to hand prop the biggest challenge is to get them to stand
close enough to the prop. Standing too far back is much more dangerous
than standing too close. The worst thing that could happen is to fall
into the prop, something that can only happen if you are standing back
and leaning into it.

-Robert

[Morgans[_2_]]

"Robert M. Gary" > wrote

> Because the top arch of the prop is close to my head. When teaching
> students to hand prop the biggest challenge is to get them to stand
> close enough to the prop. Standing too far back is much more dangerous
> than standing too close. The worst thing that could happen is to fall
> into the prop, something that can only happen if you are standing back
> and leaning into it.

I was wrong. I had not heard that exact variation, before. <g>

Kicking though is still too close, even if you are swinging your body away
from the tip?
--
Jim in NC

[Dave[_5_]]

> However! I've never moved a prop unless someone was standing on the
> brakes, and since if I'm propping the plane it's usually because the
> guy at the controls is a stranger who probably knows little about
> Cubs, I always prop from behind.
>
> Blue skies! -- Dan Ford


I flew cubs for awhile 30+ years ago. If there was no one around to
prop yours, the drill was to stand behind the prop on the right side
and flip it with your right hand, The left was poised to adjust the
throttle when it caught. I recall that they were amazingly easy to
start (usually on the first or second try).

David Johnson

[Dana M. Hague]

On Tue, 15 May 2007 17:47:01 -0400, "Morgans"
> wrote:

>Why no hand propping a nose dragger for you?

I've done it a few times but found it very awkward, as the prop on,
say, a C-150 or 172 is much lower than the prop on a taildragger like
my T-Craft.

On the T-Craft turning it backwards was the standard way of clearing
it if it was flooded... but there was no impulse coupling nor vacuum
pump.

-Dana

--
--
If replying by email, please make the obvious changes.
-------------------------------------------------------------------------------
Congress shall make no law....What part of NO didn't you understand?

[Jose]

> Kicking though is still too close, even if you are swinging your body away
> from the tip?

What exactly is "kicking"?

Jose
--
There are two kinds of people in the world. Those that just want to
know what button to push, and those that want to know what happens when
they push the button.
for Email, make the obvious change in the address.

[Don Tuite]

On Thu, 17 May 2007 04:05:57 GMT, Jose >
wrote:

>> Kicking though is still too close, even if you are swinging your body away
>> from the tip?
>
>What exactly is "kicking"?

You're facing the prop from the front ot the plane. The blade is at
10 o'clock, at the start of a compression stroke,. You've previously
primed the engine and pulled the prop through several compressions
with the switch cold and the mixture rich.

Now you holler "Hot!, Brakes!" (assuming somebody's in the cockpit --
otherwise you switch the mags to hot and check the chocks and tiedown.

Reach up, pads of your fingers just over the top of the blade. Left
leg on ground, right leg swings forward and smartly back at the same
time that you snap the blade down. The leg swing propels your body
backward, away from the propeller arc.

That was the drill on the Taylorcraft. Cub pilots can swing the prop
from behind because of the way the doors work. I guess you'd have to
prop a T-craft on floats from behind, too, but it wouldn't be pretty
to look at.

It took the lady who sold me the plane about ten minutes to teach it
to me. It feels kinda natural. If it's a big exertion, you're doing
it wrong.

Don

[C J Campbell[_1_]]

On 2007-05-15 16:28:54 -0700, EridanMan > said:

> Interesting topic, interesting discussion... but if I may expand on
> the original question a bit?
>
> The Original piper POH that came with my bird ('67 PA-28-140) actually
> recommends that that prop be pulled through two complete rotations
> backwards any time the engine is started after sitting for a long time
> (it actually says its a good idea for every flight, but should be
> mandatory any time the engine's been sitting for a while).
>
> I've NEVER heard or seen this advice anywhere else... I've never
> practiced it... It seems almost insane to me... but the book says
> what the book says.
>
> Anyone have any clue why?
>
> I can get the exact wording tpmogjt ... its in the 'preflight and
> takeoff' section of the book.

This is also recommended in at least Cessna 172 manuals for cold
weather starts. The idea is that oil that is cold or has been sitting
awhile is thicker and more sluggish. Pulling the prop through limbers
up the oil some, so the engine does not have to work as hard while
starting. It can make all the difference in whether you are able to
start the engine or not.
--
Waddling Eagle
World Famous Flight Instructor

[C J Campbell[_1_]]

On 2007-05-15 07:46:15 -0700, "Dudley Henriques" > said:

>
> "Doug Palmer" > wrote in message
> ink.net...
>> Several pilots found themselves in a debate at our field yesterday. The
>> issue is weather it is safer to move the propeller on a (parked) aircraft
>> in the direction of usual engine rotation, or opposite usual rotation.
>> This is assuming that the propeller needs to move for some reason.
>>
>> The reasonings ranged from "you should not turn an engine backwards" to
>> "turning the engine backwards disarms the impulse coupling", to several
>> issues in between.
>>
>> Any thoughts from the groups collective wisdom?
>
> This is one issue where you don't want to get bogged down in the
> technicalities involving vacuum pumps and impulse couplings.
> The bottom line on this issue is that you should NEVER.....EVER...... trust
> a propeller not to kill you if you turn it by hand IN EITHER DIRECTION while
> it's attached to the airplane.
> Dudley Henriques

People will say it is technically impossible, but I think it is wishful
thinking. An engine may not run backwards very well, but I have seen
too many malfunctioning magnetos to believe that it could never happen.
It might be improbable, but I would not bet my life on the idea that it
is impossible.
--
Waddling Eagle
World Famous Flight Instructor

[C J Campbell[_1_]]

On 2007-05-15 05:59:05 -0700, "Doug Palmer" > said:

> Several pilots found themselves in a debate at our field yesterday. The
> issue is weather it is safer to move the propeller on a (parked) aircraft in
> the direction of usual engine rotation, or opposite usual rotation. This is
> assuming that the propeller needs to move for some reason.
>
> The reasonings ranged from "you should not turn an engine backwards" to
> "turning the engine backwards disarms the impulse coupling", to several
> issues in between.
>
> Any thoughts from the groups collective wisdom?

An engine can be made to run backwards. Model airplane engines do it
all the time, usually as a result of mixture that is too rich. Granted,
real airplane engines are different and have more safety systems, but I
could not say that it is impossible, especially given the enormous
variety in types of engines, magnetos, starters, and fuel systems you
see on airplanes.

I have never heard of an accident involving an engine running backward.
I haven't found one, either. You can be the first! :-)
--
Waddling Eagle
World Famous Flight Instructor

[Robert M. Gary]

On May 16, 3:05 pm, "Morgans" > wrote:
> "Robert M. Gary" > wrote
>
> > Because the top arch of the prop is close to my head. When teaching
> > students to hand prop the biggest challenge is to get them to stand
> > close enough to the prop. Standing too far back is much more dangerous
> > than standing too close. The worst thing that could happen is to fall
> > into the prop, something that can only happen if you are standing back
> > and leaning into it.
>
> I was wrong. I had not heard that exact variation, before. <g>
>
> Kicking though is still too close, even if you are swinging your body away
> from the tip?
> --
> Jim in NC

In a tailwheel, as you pull the prop "down" during the kick you are
also moving toward yourself (because of the angle the taildragger sits
on the ground), which helps you maintain contact as you are moving
away from it. In a nose wheel plane you'd be pushing straight down on
the prop, causing your head to move down closer to the prop arch.

-Robert

[Steve Foley]

"C J Campbell" > wrote in message
news:2007051622171050878-christophercampbell@hotmailcom...

> An engine can be made to run backwards. Model airplane engines do it all
> the time, usually as a result of mixture that is too rich. Granted, real
> airplane engines are different and have more safety systems, but I could
> not say that it is impossible, especially given the enormous variety in
> types of engines, magnetos, starters, and fuel systems you see on
> airplanes.

I don't see how a four cycle engine can run backwards. If the crank is
turning backwards, the intake valve would be open while the piston is going
up, pushing the contents of the cylinder into the intake manifold. While the
exhaust valve is open, the piston would be going down, sucking whatever is
in the exhaust manifold into the cylinder. there would have to be a source
of fuel in the exhaust manifold for the engine to run.

Model engines are two stroke, so they can run backwards.

A long time ago, I bought a moped (also a two cycle). The timing was so far
retarded that it ran better backwards than forwards until I had it timed. It
couldn't pull me up the hill because it ran so badly. Once, it fired up
backwards and ran great. I rode it up the hill backwards.

[Peter Dohm]

> >> Several pilots found themselves in a debate at our field yesterday.
The
> >> issue is weather it is safer to move the propeller on a (parked)
aircraft
> >> in the direction of usual engine rotation, or opposite usual rotation.
> >> This is assuming that the propeller needs to move for some reason.
> >>
> >> The reasonings ranged from "you should not turn an engine backwards" to
> >> "turning the engine backwards disarms the impulse coupling", to several
> >> issues in between.
> >>
> >> Any thoughts from the groups collective wisdom?
> >
> > This is one issue where you don't want to get bogged down in the
> > technicalities involving vacuum pumps and impulse couplings.
> > The bottom line on this issue is that you should NEVER.....EVER......
trust
> > a propeller not to kill you if you turn it by hand IN EITHER DIRECTION
while
> > it's attached to the airplane.
> > Dudley Henriques
>
> People will say it is technically impossible, but I think it is wishful
> thinking. An engine may not run backwards very well, but I have seen
> too many malfunctioning magnetos to believe that it could never happen.
> It might be improbable, but I would not bet my life on the idea that it
> is impossible.
> --
> Waddling Eagle
> World Famous Flight Instructor
>
It doesn't really have to "run" to hit you, it only has to "kick" once. And
that is cold comfort indeed, since immediate death is far from the worst
thing that can happen to a person.

(rant omitted)
Peter

[Maxwell]

"C J Campbell" > wrote in message
news:2007051622001427544-christophercampbell@hotmailcom...
>
> People will say it is technically impossible, but I think it is wishful
> thinking. An engine may not run backwards very well, but I have seen too
> many malfunctioning magnetos to believe that it could never happen. It
> might be improbable, but I would not bet my life on the idea that it is
> impossible.
> --

On a 2 cycle engine, ignition time is all it takes. Some golf carts actually
work that way. The starter and ignition time is selectable by the direction
indicatior on the dash.

But on a 4 cycle engine, the valve timing would have you intaking through
the exhaust, and exhausting through the intake.

[Dudley Henriques[_2_]]

"C J Campbell" > wrote in message
news:2007051622001427544-christophercampbell@hotmailcom...
> On 2007-05-15 07:46:15 -0700, "Dudley Henriques" >
> said:
>
>>
>> "Doug Palmer" > wrote in message
>> ink.net...
>>> Several pilots found themselves in a debate at our field yesterday. The
>>> issue is weather it is safer to move the propeller on a (parked)
>>> aircraft
>>> in the direction of usual engine rotation, or opposite usual rotation.
>>> This is assuming that the propeller needs to move for some reason.
>>>
>>> The reasonings ranged from "you should not turn an engine backwards" to
>>> "turning the engine backwards disarms the impulse coupling", to several
>>> issues in between.
>>>
>>> Any thoughts from the groups collective wisdom?
>>
>> This is one issue where you don't want to get bogged down in the
>> technicalities involving vacuum pumps and impulse couplings.
>> The bottom line on this issue is that you should NEVER.....EVER......
>> trust
>> a propeller not to kill you if you turn it by hand IN EITHER DIRECTION
>> while
>> it's attached to the airplane.
>> Dudley Henriques
>
> People will say it is technically impossible, but I think it is wishful
> thinking. An engine may not run backwards very well, but I have seen too
> many malfunctioning magnetos to believe that it could never happen. It
> might be improbable, but I would not bet my life on the idea that it is
> impossible.
> --
> Waddling Eagle
> World Famous Flight Instructor
>

Rule number one for me has always been "never give the machinery an
advantage".
If it CAN kill me, it just MIGHT kill me, so I treat it that way.
:-)))
Dudley Henriques

[[email protected]]

On May 16, 8:26 pm, Dana M. Hague
<d(dash)m(dash)hague(at)comcast(dot)net> wrote:
> On Tue, 15 May 2007 17:47:01 -0400, "Morgans"
>
> > wrote:
> >Why no hand propping a nose dragger for you?
>
> I've done it a few times but found it very awkward, as the prop on,
> say, a C-150 or 172 is much lower than the prop on a taildragger like
> my T-Craft.
>
> On the T-Craft turning it backwards was the standard way of clearing
> it if it was flooded... but there was no impulse coupling nor vacuum
> pump.

I haven't yet seen a Continental or Lycoming lightplane engine
without an impulse coupling on at least one mag. That impulse
mechanism is necessary for starting because it snaps the mag over fast
so it'll generate a spark, but it also retards the spark to at or near
top dead center so that the engine doesn't kick back. The usual firing
position on an A-65 is 30 degrees before top dead center. The other,
non-impulse mag won't fire at hand-propping speeds, but will sometimes
fire immediately after the engine catches and will stop it or kick it
backwards or make it hammer frightfully until the RPM comes up to
idle. Some pilots will set the mag switch to the impulse mag only
while hand-propping, going to Both after the engine is running. Much
safer. I have two impulse mags on mine and it behaves itself.
I hand-prop using one hand only. As I pull down I fold
myself so that my weight is carried back a little. The trick, as has
been mentioned, is to get pretty close to begin with. And make sure of
your footing. Anything slippery like snow or ice or wet grass, or
gravel on the pavement, can let you slide into the prop.
I don't prime my A-65 unless the temp is down around
freezing. It floods way too easily. Mags on, throttle at idle, and it
will catch on the sixth to eighth blade.

Dan

[Orval Fairbairn]

In article . com>,
wrote:

> On May 16, 8:26 pm, Dana M. Hague
> <d(dash)m(dash)hague(at)comcast(dot)net> wrote:
> > On Tue, 15 May 2007 17:47:01 -0400, "Morgans"
> >
> > > wrote:
> > >Why no hand propping a nose dragger for you?
> >
> > I've done it a few times but found it very awkward, as the prop on,
> > say, a C-150 or 172 is much lower than the prop on a taildragger like
> > my T-Craft.
> >
> > On the T-Craft turning it backwards was the standard way of clearing
> > it if it was flooded... but there was no impulse coupling nor vacuum
> > pump.
>
> I haven't yet seen a Continental or Lycoming lightplane engine
> without an impulse coupling on at least one mag. That impulse
> mechanism is necessary for starting because it snaps the mag over fast
> so it'll generate a spark, but it also retards the spark to at or near
> top dead center so that the engine doesn't kick back.

.........

Both mags on the O-435 Lycoming in my Johnson Rocket are non-impulse.

[Don Poitras]

Orval Fairbairn > wrote:
> In article . com>,
> wrote:

> > On May 16, 8:26 pm, Dana M. Hague
> > <d(dash)m(dash)hague(at)comcast(dot)net> wrote:
> > > On Tue, 15 May 2007 17:47:01 -0400, "Morgans"
> > >
> > > > wrote:
> > > >Why no hand propping a nose dragger for you?
> > >
> > > I've done it a few times but found it very awkward, as the prop on,
> > > say, a C-150 or 172 is much lower than the prop on a taildragger like
> > > my T-Craft.
> > >
> > > On the T-Craft turning it backwards was the standard way of clearing
> > > it if it was flooded... but there was no impulse coupling nor vacuum
> > > pump.
> >
> > I haven't yet seen a Continental or Lycoming lightplane engine
> > without an impulse coupling on at least one mag. That impulse
> > mechanism is necessary for starting because it snaps the mag over fast
> > so it'll generate a spark, but it also retards the spark to at or near
> > top dead center so that the engine doesn't kick back.

> ........

> Both mags on the O-435 Lycoming in my Johnson Rocket are non-impulse.

Both mags on the O-320 Lycoming in my Beech Musketeer are non-impulse.

--
Don Poitras

[JGalban via AviationKB.com]

wrote:
>
> I haven't yet seen a Continental or Lycoming lightplane engine
>without an impulse coupling on at least one mag.

They're out there. In addition to the impuse system, there was a starting
system called "shower of sparks" that used a gadget called a vibrator to
provide the low rpm spark. Unlike the impulse system, the vibrator required
electrical power from the battery to make a spark.

I've usually seen these on older models.

John Galban=====>N4BQ (PA28-180)

--
Message posted via AviationKB.com
http://www.aviationkb.com/Uwe/Forums.aspx/aviation/200705/1

[Capt. Geoffrey Thorpe]

"C J Campbell" > wrote in message
news:2007051622171050878-christophercampbell@hotmailcom...
> On 2007-05-15 05:59:05 -0700, "Doug Palmer" >
> said:
>
<...>
> An engine can be made to run backwards. Model airplane engines do it all
> the time, usually as a result of mixture that is too rich. Granted,

Those are two strokes and don't rely on valve timing to run. A buddy had a
Bultaco motorcycle that liked to do that - it was pretty funny when he
dumped the clutch not realizing that it was running backwards.

> real airplane engines are different and have more safety systems, but I
> could not say that it is impossible, especially given the enormous variety
> in types of engines, magnetos, starters, and fuel systems you see on
> airplanes.

If you turn a conventional four stroke engine backwards, what would have
been the exhaust stroke is now an intake stroke, and what was the intake
stroke is now an exhaust stroke - the air will flow backwards through the
engine from the exhaust to the intake so fuel will not find it's way in to
sustatin combustion. On the other hand, an engine can "kick back" for a
revolution or so - and that's enough to do the damage...

To make a conventional four stroke run backwards, you have to re-arrange the
location of the lobes on the cam.

Trivia: Kettering developed his electric starter after a friend was killed
when an automobile engine kicked back while he was starting it with a hand
crank...

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

[Cubdriver]

On 16 May 2007 07:50:51 -0700, wrote:

> Turning a prop backwards during hand-propping reduces the
>mixture ratio in the cylinders if the engine has been overprimed. Air
>is drawn through the exhaust and will absorb the fuel, carrying it
>back through the carb and out. The carb will often drip fuel during
>such an event.

That might explain an event that startled me at the time. While being
propped in hot weather--unsuccessfully--I was strapped in the rear
seat of the Cub, when the mechanic came by and said, "Your engine is
on fire." He leaned close to the cowling (the engine is visible
through the iconic J-3 cowling "ears"), gave a puff, blew the fire
out, and went on his way without further comment.

Blue skies! -- Dan Ford

[Cubdriver]

On Wed, 16 May 2007 22:00:14 -0700, C J Campbell
> wrote:

>People will say it is technically impossible, but I think it is wishful
>thinking. An engine may not run backwards very well,

During World War II (really!) I worked on a farm in Concord, Mass.
There was a great steel-wheeled tractor that was started with a hand
crank. One time the tractor backfired while the lad was spinning the
crank, and the engine started running backwards. He jumped aboard and
had a great time wheeling it around the yard, one speed forward and
three in reverse. Blue skies! -- Dan Ford

[Cubdriver]

On Wed, 16 May 2007 21:39:54 -0700, Don Tuite
> wrote:

>Now you holler "Hot!, Brakes!" (assuming somebody's in the cockpit --
>otherwise you switch the mags to hot and check the chocks and tiedown.

With me, it's BRAKES! CRACKED! (referring to the throttle), HOT!
>
>Reach up, pads of your fingers just over the top of the blade. Left
>leg on ground, right leg swings forward and smartly back at the same
>time that you snap the blade down. The leg swing propels your body
>backward, away from the propeller arc.

Huh. With me it's the left leg that swings. Then the right leg turns
me farther back and to the left, out of the propeller arc.

Blue skies! -- Dan Ford

[Capt. Geoffrey Thorpe]

"Cubdriver" <usenet AT danford DOT net> wrote in message
...
> On Wed, 16 May 2007 22:00:14 -0700, C J Campbell
> > wrote:
>
>>People will say it is technically impossible, but I think it is wishful
>>thinking. An engine may not run backwards very well,
>
> During World War II (really!) I worked on a farm in Concord, Mass.
> There was a great steel-wheeled tractor that was started with a hand
> crank. One time the tractor backfired while the lad was spinning the
> crank, and the engine started running backwards. He jumped aboard and
> had a great time wheeling it around the yard, one speed forward and
> three in reverse. Blue skies! -- Dan Ford

That was a Diesel engine, correct?

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

[Cubdriver]

On 16 May 2007 17:22:39 -0700, Dave > wrote:

>I flew cubs for awhile 30+ years ago. If there was no one around to
>prop yours, the drill was to stand behind the prop on the right side
>and flip it with your right hand, The left was poised to adjust the
>throttle when it caught. I recall that they were amazingly easy to
>start (usually on the first or second try).

They still are, if the engine is warm, and that's the only occasion
when I have to prop the plane myself.

I hold onto the window frame with my left hand and, like you, pull
down with the right hand. I bounce it lightly a couple times in
advance, and one knows exactly when to pull down hard after it springs
back up.

At a minimum, I have a pair of chocks on a length of parachute cord. I
can climb into the back seat, give the cord a tug, then reel in the
chocks.

Blue skies! -- Dan Ford

[[email protected]]

On May 17, 2:52 pm, "JGalban via AviationKB.com" <u32749@uwe> wrote:
> wrote:
>
> > I haven't yet seen a Continental or Lycoming lightplane engine
> >without an impulse coupling on at least one mag.
>
> They're out there. In addition to the impuse system, there was a starting
> system called "shower of sparks" that used a gadget called a vibrator to
> provide the low rpm spark. Unlike the impulse system, the vibrator required
> electrical power from the battery to make a spark.
>
> I've usually seen these on older models.

Yup, you're right. Bendix made that system to provide a hot
spark for starting. The mag switch had extra terminals to provide an
AC signal from a buzzbox to the mag, but that mag had a second set of
points that gave the later spark for starting. Unison has a similar
setup now, but solid-state instead of an electromechanical buzzer to
create the signal for the primary winding.

Dan

[Morgans[_2_]]

<>> They're out there. In addition to the impuse system, there was a
starting
>> system called "shower of sparks" that used a gadget called a vibrator to
>> provide the low rpm spark. Unlike the impulse system, the vibrator
>> required
>> electrical power from the battery to make a spark.
>>
>> I've usually seen these on older models.
>
> Yup, you're right. Bendix made that system to provide a hot
> spark for starting. The mag switch had extra terminals to provide an
> AC signal from a buzzbox to the mag, but that mag had a second set of
> points that gave the later spark for starting. Unison has a similar
> setup now, but solid-state instead of an electromechanical buzzer to
> create the signal for the primary winding.

Both of those spark vibrators just make a constant sparking, just waiting
for the right combination of fuel, air and compression, don't they?

If that is the case, it would seem like that would be like a very advanced
spark, and could easily make a backfire to spin the engine backwards. Is
this what you have observed?

If that is not how they work, then...
Never Mind ! ! ! <g>
--
Jim in NC

[Scott Skylane]

Morgans wrote:


>
> Both of those spark vibrators just make a constant sparking, just waiting
> for the right combination of fuel, air and compression, don't they?
>
> If that is the case, it would seem like that would be like a very advanced
> spark, and could easily make a backfire to spin the engine backwards. Is
> this what you have observed?
>
> If that is not how they work, then...
> Never Mind ! ! ! <g>

The system produces a much higher powered, rapid succession of sparks,
but they are only delivered to each plug via a second set of points in
the mag, that are set at a delayed timing period.

Happy Flying!
Scott Skylane

[Morgans[_2_]]

"Scott Skylane"> wrote

> The system produces a much higher powered, rapid succession of sparks, but
> they are only delivered to each plug via a second set of points in the
> mag, that are set at a delayed timing period.

OK, thanks for that info!
--
Jim in NC

[C J Campbell[_1_]]

On 2007-05-17 14:59:44 -0700, "Capt. Geoffrey Thorpe" <The Sea Hawk at
wow way d0t com> said:

> "Cubdriver" <usenet AT danford DOT net> wrote in message
> ...
>> On Wed, 16 May 2007 22:00:14 -0700, C J Campbell
>> > wrote:
>>
>>> People will say it is technically impossible, but I think it is wishful
>>> thinking. An engine may not run backwards very well,
>>
>> During World War II (really!) I worked on a farm in Concord, Mass.
>> There was a great steel-wheeled tractor that was started with a hand
>> crank. One time the tractor backfired while the lad was spinning the
>> crank, and the engine started running backwards. He jumped aboard and
>> had a great time wheeling it around the yard, one speed forward and
>> three in reverse. Blue skies! -- Dan Ford
>
> That was a Diesel engine, correct?

My great uncle Ern was nearly killed by a Model T Ford that he cranked
up and the engine backfired and ran backward. 'Course, that guy was
nearly killed so many times...
--
Waddling Eagle
World Famous Flight Instructor

[Orval Fairbairn]

In article >,
Cubdriver <usenet AT danford DOT net> wrote:

> On Wed, 16 May 2007 21:39:54 -0700, Don Tuite
> > wrote:
>
> >Now you holler "Hot!, Brakes!" (assuming somebody's in the cockpit --
> >otherwise you switch the mags to hot and check the chocks and tiedown.
>
> With me, it's BRAKES! CRACKED! (referring to the throttle), HOT!
> >
> >Reach up, pads of your fingers just over the top of the blade. Left
> >leg on ground, right leg swings forward and smartly back at the same
> >time that you snap the blade down. The leg swing propels your body
> >backward, away from the propeller arc.
>
> Huh. With me it's the left leg that swings. Then the right leg turns
> me farther back and to the left, out of the propeller arc.
>
> Blue skies! -- Dan Ford

I was taught:

SWITCH OFF!

BRAKES!

(Propping guy pushes plane to verify)

THROTTLE CRACKED!

CONTACT! (so as not to confuse with switch on)

Now the propping begins.

[Dave Stadt]

"C J Campbell" > wrote in message
news:2007051720300843658-christophercampbell@hotmailcom...
> On 2007-05-17 14:59:44 -0700, "Capt. Geoffrey Thorpe" <The Sea Hawk at
> wow way d0t com> said:
>
>> "Cubdriver" <usenet AT danford DOT net> wrote in message
>> ...
>>> On Wed, 16 May 2007 22:00:14 -0700, C J Campbell
>>> > wrote:
>>>
>>>> People will say it is technically impossible, but I think it is wishful
>>>> thinking. An engine may not run backwards very well,
>>>
>>> During World War II (really!) I worked on a farm in Concord, Mass.
>>> There was a great steel-wheeled tractor that was started with a hand
>>> crank. One time the tractor backfired while the lad was spinning the
>>> crank, and the engine started running backwards. He jumped aboard and
>>> had a great time wheeling it around the yard, one speed forward and
>>> three in reverse. Blue skies! -- Dan Ford
>>
>> That was a Diesel engine, correct?
>
> My great uncle Ern was nearly killed by a Model T Ford that he cranked up
> and the engine backfired and ran backward. 'Course, that guy was nearly
> killed so many times...
> --
> Waddling Eagle
> World Famous Flight Instructor

A Model T will not run backwards. Even if it did run backwards it would in
no way would put your life in danger.

[C J Campbell[_1_]]

On 2007-05-17 21:00:36 -0700, "Dave Stadt" > said:

>
> "C J Campbell" > wrote in message
> news:2007051720300843658-christophercampbell@hotmailcom...
>> On 2007-05-17 14:59:44 -0700, "Capt. Geoffrey Thorpe" <The Sea Hawk at
>> wow way d0t com> said:
>>
>>> "Cubdriver" <usenet AT danford DOT net> wrote in message
>>> ...
>>>> On Wed, 16 May 2007 22:00:14 -0700, C J Campbell
>>>> > wrote:
>>>>
>>>>> People will say it is technically impossible, but I think it is wishful
>>>>> thinking. An engine may not run backwards very well,
>>>>
>>>> During World War II (really!) I worked on a farm in Concord, Mass.
>>>> There was a great steel-wheeled tractor that was started with a hand
>>>> crank. One time the tractor backfired while the lad was spinning the
>>>> crank, and the engine started running backwards. He jumped aboard and
>>>> had a great time wheeling it around the yard, one speed forward and
>>>> three in reverse. Blue skies! -- Dan Ford
>>>
>>> That was a Diesel engine, correct?
>>
>> My great uncle Ern was nearly killed by a Model T Ford that he cranked up
>> and the engine backfired and ran backward. 'Course, that guy was nearly
>> killed so many times...
>> --
>> Waddling Eagle
>> World Famous Flight Instructor
>
> A Model T will not run backwards. Even if it did run backwards it would in
> no way would put your life in danger.

The Model T was notorious for running backwards momentarily and causing
the crank to hit people in the face or it would break an arm. Ern was
knocked unconscious and suffered a broken nose.

It will not run continuously backwards, but it will run for a stroke or
two, just enough to hit you hard.
--
Waddling Eagle
World Famous Flight Instructor

[C J Campbell[_1_]]

On 2007-05-17 14:26:01 -0700, "Capt. Geoffrey Thorpe" <The Sea Hawk at
wow way d0t com> said:

> "C J Campbell" > wrote in message
> news:2007051622171050878-christophercampbell@hotmailcom...
>> On 2007-05-15 05:59:05 -0700, "Doug Palmer" >
>> said:
>>
> <...>
>> An engine can be made to run backwards. Model airplane engines do it all
>> the time, usually as a result of mixture that is too rich. Granted,
>
> Those are two strokes and don't rely on valve timing to run. A buddy had a
> Bultaco motorcycle that liked to do that - it was pretty funny when he
> dumped the clutch not realizing that it was running backwards.
>
>> real airplane engines are different and have more safety systems, but I
>> could not say that it is impossible, especially given the enormous variety
>> in types of engines, magnetos, starters, and fuel systems you see on
>> airplanes.
>
> If you turn a conventional four stroke engine backwards, what would have
> been the exhaust stroke is now an intake stroke, and what was the intake
> stroke is now an exhaust stroke - the air will flow backwards through the
> engine from the exhaust to the intake so fuel will not find it's way in to
> sustatin combustion. On the other hand, an engine can "kick back" for a
> revolution or so - and that's enough to do the damage...
>
> To make a conventional four stroke run backwards, you have to re-arrange the
> location of the lobes on the cam.
>
> Trivia: Kettering developed his electric starter after a friend was killed
> when an automobile engine kicked back while he was starting it with a hand
> crank...

Sounds like it was running backwards to me. Maybe it would not keep
running, but the prop only has to hit you once.
--
Waddling Eagle
World Famous Flight Instructor

[[email protected]]

On May 18, 7:38 am, C J Campbell >
wrote:
> On 2007-05-17 14:26:01 -0700, "Capt. Geoffrey Thorpe" <The Sea Hawk at
> wow way d0t com> said:
>
>
>
>
>
> > "C J Campbell" > wrote in message
> >news:2007051622171050878-christophercampbell@hotmailcom...
> >> On 2007-05-15 05:59:05 -0700, "Doug Palmer" >
> >> said:
>
> > <...>
> >> An engine can be made to run backwards. Model airplane engines do it all
> >> the time, usually as a result of mixture that is too rich. Granted,
>
> > Those are two strokes and don't rely on valve timing to run. A buddy had a
> > Bultaco motorcycle that liked to do that - it was pretty funny when he
> > dumped the clutch not realizing that it was running backwards.
>
> >> real airplane engines are different and have more safety systems, but I
> >> could not say that it is impossible, especially given the enormous variety
> >> in types of engines, magnetos, starters, and fuel systems you see on
> >> airplanes.
>
> > If you turn a conventional four stroke engine backwards, what would have
> > been the exhaust stroke is now an intake stroke, and what was the intake
> > stroke is now an exhaust stroke - the air will flow backwards through the
> > engine from the exhaust to the intake so fuel will not find it's way in to
> > sustatin combustion. On the other hand, an engine can "kick back" for a
> > revolution or so - and that's enough to do the damage...
>
> > To make a conventional four stroke run backwards, you have to re-arrange the
> > location of the lobes on the cam.
>
> > Trivia: Kettering developed his electric starter after a friend was killed
> > when an automobile engine kicked back while he was starting it with a hand
> > crank...
>
> Sounds like it was running backwards to me. Maybe it would not keep
> running, but the prop only has to hit you once.
> --
> Waddling Eagle
> World Famous Flight Instructor- Hide quoted text -
>
> - Show quoted text -

The engine can fire when pulled through forward, but if the
prop has too little momentum to carry the piston past TDC or the
firing is advanced enough, it will kick backward. One blade,
travelling at the speed it does, will split your skull. I work on
these things all day, and when I forget that the prop is there and I
stand up after doing something on the engine and whack my head on a
stationary prop blade, it hurts big time. When it's swinging after a
kickback it's moving faster than an axe and weighs a lot more. Whether
dull or not, that trailing edge will do plenty of damage. You learn
respect for these things when you bash your head occasionally.
I used to own a '78 Dodge pickup truck, the worst vehicle I
ever encountered. It would "diesel' on after I turned the ignition
off, ignition being caused by hot carbon points in the cylinder head.
Some cylinders would fire, some wouldn't, and the result was an
exhaust system full of fuel vapours. An auto's exhaust system is a lot
longer than a lightplane's, and it can store plenty of vapour. Sooner
or later the engine would kick over backward, the exhaust would get
sucked into a cylinder, and it would run backward for a half-second or
so and finally die when the fuel vapours ran out. The hot carbon was
still doing the igniting, like a glow plug.
If an airplane does that it won't run so long, and it only
does it if there's hot carbon in the head which means that it's been
running. And that's why I consider a prop most dangerous immediately
after shutdown.

Dan

[nrp]

Many years ago I had a 125 hp Tripacer kick back when hand propping in
cold weather. The trailing edge of the prop put a 1/2 inch cut in my
fingertip - right through the leather glove I was wearing. Needless
to say I didn't go flying that day.

Lessons learned -
1) Fingers on the prop face only. Never over a trailing edge.
2) Don't over prime.
3) Know you mag system so that you are hand propping on only impulse
magnetos.

[Capt. Geoffrey Thorpe]

"C J Campbell" > wrote in message
news:2007051806380943658-christophercampbell@hotmailcom...
> On 2007-05-17 14:26:01 -0700, "Capt. Geoffrey Thorpe" <The Sea Hawk at
> wow way d0t com> said:
>
>> "C J Campbell" > wrote in message
>> news:2007051622171050878-christophercampbell@hotmailcom...
>>> On 2007-05-15 05:59:05 -0700, "Doug Palmer" >
>>> said:
>>>
>> <...>
>>
>> Trivia: Kettering developed his electric starter after a friend was
>> killed
>> when an automobile engine kicked back while he was starting it with a
>> hand
>> crank...
>
> Sounds like it was running backwards to me. Maybe it would not keep
> running, but the prop only has to hit you once.
> --
> Waddling Eagle
> World Famous Flight Instructor
>

So, we are arguing over the definition of the word "run"?

Now, if you brought your car in to where I work because it would just fire a
couple cylinders and quit and I tried to tell you that it was "running"
wouild you buy that? :-)

But, yea, one cylinders worth of "running" would be all it would take to
split one's skull.

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

[Matt Whiting]

C J Campbell wrote:
> On 2007-05-17 21:00:36 -0700, "Dave Stadt" > said:
>
>>
>> "C J Campbell" > wrote in message
>> news:2007051720300843658-christophercampbell@hotmailcom...
>>> On 2007-05-17 14:59:44 -0700, "Capt. Geoffrey Thorpe" <The Sea Hawk at
>>> wow way d0t com> said:
>>>
>>>> "Cubdriver" <usenet AT danford DOT net> wrote in message
>>>> ...
>>>>> On Wed, 16 May 2007 22:00:14 -0700, C J Campbell
>>>>> > wrote:
>>>>>
>>>>>> People will say it is technically impossible, but I think it is
>>>>>> wishful
>>>>>> thinking. An engine may not run backwards very well,
>>>>>
>>>>> During World War II (really!) I worked on a farm in Concord, Mass.
>>>>> There was a great steel-wheeled tractor that was started with a hand
>>>>> crank. One time the tractor backfired while the lad was spinning the
>>>>> crank, and the engine started running backwards. He jumped aboard and
>>>>> had a great time wheeling it around the yard, one speed forward and
>>>>> three in reverse. Blue skies! -- Dan Ford
>>>>
>>>> That was a Diesel engine, correct?
>>>
>>> My great uncle Ern was nearly killed by a Model T Ford that he
>>> cranked up
>>> and the engine backfired and ran backward. 'Course, that guy was nearly
>>> killed so many times...
>>> --
>>> Waddling Eagle
>>> World Famous Flight Instructor
>>
>> A Model T will not run backwards. Even if it did run backwards it
>> would in
>> no way would put your life in danger.
>
> The Model T was notorious for running backwards momentarily and causing
> the crank to hit people in the face or it would break an arm. Ern was
> knocked unconscious and suffered a broken nose.
>
> It will not run continuously backwards, but it will run for a stroke or
> two, just enough to hit you hard.

That is called "kick back" and isn't "running backward" at all.

Matt

[Cubdriver]

On Thu, 17 May 2007 17:59:44 -0400, "Capt. Geoffrey Thorpe" <The Sea
Hawk at wow way d0t com> wrote:

> crank. One time the tractor backfired while the lad was spinning the
>> crank, and the engine started running backwards. He jumped aboard and
>> had a great time wheeling it around the yard, one speed forward and
>> three in reverse. Blue skies! -- Dan Ford
>
>That was a Diesel engine, correct?

I doubt it. We didn't even know what disel was!

At least I didn't. This tractor was built in the 1930s or 1920s,
before the days of pneumatic tires.

[Peter Dohm]

> >>>>>> People will say it is technically impossible, but I think it is
> >>>>>> wishful
> >>>>>> thinking. An engine may not run backwards very well,
> >>>>>
> >>>>> During World War II (really!) I worked on a farm in Concord, Mass.
> >>>>> There was a great steel-wheeled tractor that was started with a hand
> >>>>> crank. One time the tractor backfired while the lad was spinning the
> >>>>> crank, and the engine started running backwards. He jumped aboard
and
> >>>>> had a great time wheeling it around the yard, one speed forward and
> >>>>> three in reverse. Blue skies! -- Dan Ford
> >>>>
> >>>> That was a Diesel engine, correct?
> >>>
> >>> My great uncle Ern was nearly killed by a Model T Ford that he
> >>> cranked up
> >>> and the engine backfired and ran backward. 'Course, that guy was
nearly
> >>> killed so many times...
> >>> --
> >>> Waddling Eagle
> >>> World Famous Flight Instructor
> >>
> >> A Model T will not run backwards. Even if it did run backwards it
> >> would in
> >> no way would put your life in danger.
> >
> > The Model T was notorious for running backwards momentarily and causing
> > the crank to hit people in the face or it would break an arm. Ern was
> > knocked unconscious and suffered a broken nose.
> >
> > It will not run continuously backwards, but it will run for a stroke or
> > two, just enough to hit you hard.
>
> That is called "kick back" and isn't "running backward" at all.
>
> Matt

Technically true. But "kick back" also makes a propeller a very effective
finger remover.

From what I have heard those old Model T Fords were notorious; although I do
not know how much was a result of people advancing the spark in the hope of
getting the engine to start, or how much was due to overall timing being out
of adjustment such that the markings on the spark advance control were no
longer accurate.

What makes that almost on topic is the fact that magnetos can also be out of
timing for various reasons, including wear of the points and/or the internal
cam followers, and that a failure of the impulse coupling(s) can move the
timing from after TDC to before TDC during the starting sequence. :-(

Actually, this has been a very imformative thread. For example, I had never
known the mechanism by which a four cycle engine can diesel backward beyond
a single kick--even though I have seen older automotive engines do so for a
half dozen strokes!

Peter

[Morgans[_2_]]

"Peter Dohm" > wrote

> Actually, this has been a very imformative thread. For example, I had
> never
> known the mechanism by which a four cycle engine can diesel backward
> beyond
> a single kick--even though I have seen older automotive engines do so for
> a
> half dozen strokes!


I had an older Oldsmobile that would diesel after the ignition was turned
off, sometimes for 2 minutes or more.

Whether it was running backwards, I don't know. I never thought to look for
that, and I don't own it anymore.
--
Jim in NC

[Robert M. Gary]

On May 17, 9:00 pm, "Dave Stadt" > wrote:
> "C J Campbell" > wrote in messagenews:2007051720300843658-christophercampbell@hotmailcom...
>
>
>
>
>
> > On 2007-05-17 14:59:44 -0700, "Capt. Geoffrey Thorpe" <The Sea Hawk at
> > wow way d0t com> said:
>
> >> "Cubdriver" <usenet AT danford DOT net> wrote in message
> ...
> >>> On Wed, 16 May 2007 22:00:14 -0700, C J Campbell
> >>> > wrote:
>
> >>>> People will say it is technically impossible, but I think it is wishful
> >>>> thinking. An engine may not run backwards very well,
>
> >>> During World War II (really!) I worked on a farm in Concord, Mass.
> >>> There was a great steel-wheeled tractor that was started with a hand
> >>> crank. One time the tractor backfired while the lad was spinning the
> >>> crank, and the engine started running backwards. He jumped aboard and
> >>> had a great time wheeling it around the yard, one speed forward and
> >>> three in reverse. Blue skies! -- Dan Ford
>
> >> That was a Diesel engine, correct?
>
> > My great uncle Ern was nearly killed by a Model T Ford that he cranked up
> > and the engine backfired and ran backward. 'Course, that guy was nearly
> > killed so many times...
> > --
> > Waddling Eagle
> > World Famous Flight Instructor
>
> A Model T will not run backwards. Even if it did run backwards it would in
> no way would put your life in danger.- Hide quoted text -
>
> - Show quoted text -

Running backwards for any length of time given the timing of the
spark. Usually you would expect the spark between 8-15 degress past
TDC (to allow the rod to move out and be ready to push down). if it
ran backwards, each ignition would be working against the engine.

-Robert

[Morgans[_2_]]

"Robert M. Gary" > wrote

> Running backwards for any length of time given the timing of the
> spark. Usually you would expect the spark between 8-15 degress past
> TDC (to allow the rod to move out and be ready to push down). if it
> ran backwards, each ignition would be working against the engine.

Are you saying that a Model-T is timed at 8-15 degrees past Top Dead
Center?

I hope so, because that sure is not reality for modern engines.
--
Jim in NC

[Dave Stadt]

"C J Campbell" > wrote in message
news:2007051806363950073-christophercampbell@hotmailcom...
> On 2007-05-17 21:00:36 -0700, "Dave Stadt" > said:
>
>>
>> "C J Campbell" > wrote in message
>> news:2007051720300843658-christophercampbell@hotmailcom...
>>> On 2007-05-17 14:59:44 -0700, "Capt. Geoffrey Thorpe" <The Sea Hawk at
>>> wow way d0t com> said:
>>>
>>>> "Cubdriver" <usenet AT danford DOT net> wrote in message
>>>> ...
>>>>> On Wed, 16 May 2007 22:00:14 -0700, C J Campbell
>>>>> > wrote:
>>>>>
>>>>>> People will say it is technically impossible, but I think it is
>>>>>> wishful
>>>>>> thinking. An engine may not run backwards very well,
>>>>>
>>>>> During World War II (really!) I worked on a farm in Concord, Mass.
>>>>> There was a great steel-wheeled tractor that was started with a hand
>>>>> crank. One time the tractor backfired while the lad was spinning the
>>>>> crank, and the engine started running backwards. He jumped aboard and
>>>>> had a great time wheeling it around the yard, one speed forward and
>>>>> three in reverse. Blue skies! -- Dan Ford
>>>>
>>>> That was a Diesel engine, correct?
>>>
>>> My great uncle Ern was nearly killed by a Model T Ford that he cranked
>>> up
>>> and the engine backfired and ran backward. 'Course, that guy was nearly
>>> killed so many times...
>>> --
>>> Waddling Eagle
>>> World Famous Flight Instructor
>>
>> A Model T will not run backwards. Even if it did run backwards it would
>> in
>> no way would put your life in danger.
>
> The Model T was notorious for running backwards momentarily and causing
> the crank to hit people in the face or it would break an arm. Ern was
> knocked unconscious and suffered a broken nose.
>
> It will not run continuously backwards, but it will run for a stroke or
> two, just enough to hit you hard.
> --
> Waddling Eagle
> World Famous Flight Instructor

Funny, I have been driving one for near 10 years and have never heard such a
thing. If your head is so low as to get hit by the crank you have much
bigger problems to deal with or the guy was less than 3' tall. The crank
has a ratchet and will free wheel if the engine pops backwards.

[Dave Stadt]

"Morgans" > wrote in message
...
>
> "Robert M. Gary" > wrote
>
>> Running backwards for any length of time given the timing of the
>> spark. Usually you would expect the spark between 8-15 degress past
>> TDC (to allow the rod to move out and be ready to push down). if it
>> ran backwards, each ignition would be working against the engine.
>
> Are you saying that a Model-T is timed at 8-15 degrees past Top Dead
> Center?
>
> I hope so, because that sure is not reality for modern engines.
> --
> Jim in NC

They have manual spark advance. At start up and full retard you are at TDC
give or take a couple of degrees.

[Jose]

> The crank has a ratchet and will
> free wheel if the engine pops backwards.

How would that work? The engine going backwards against the crank
imparts the same (direction) force as the crank going forwards against a
recalcitrant engine. That would freewheel too, defeating the purpose.

Jose
--
There are two kinds of people in the world. Those that just want to
know what button to push, and those that want to know what happens when
they push the button.
for Email, make the obvious change in the address.

[Matt Whiting]

Jose wrote:
>> The crank has a ratchet and will
>> free wheel if the engine pops backwards.
>
> How would that work? The engine going backwards against the crank
> imparts the same (direction) force as the crank going forwards against a
> recalcitrant engine. That would freewheel too, defeating the purpose.

Most hand cranks (I haven't seen a Model T lately, but on old tractors
and such) had a cam design such that the crank handle would turn the
crank shaft only in one direction. If the crank shaft tried to drive
the crank handle (as during a kick-back), it would spit the crank handle
forward and disengage it.

It is like the screw heads you see on some bathroom stalls where the
slot in the screw head has ramps behind it on opposite sides such that
you can tighten with a normal screw driver, but you can't easily remove
it with a normal screw driver.

Matt

[Brian[_1_]]

>
> Funny, I have been driving one for near 10 years and have never heard such a
> thing. If your head is so low as to get hit by the crank you have much
> bigger problems to deal with or the guy was less than 3' tall. The crank
> has a ratchet and will free wheel if the engine pops backwards.- Hide quoted text -
>
> - Show quoted text -

Sorry Dave,

That (almost) can't be correct. My 1916 Model -T as did all the other
hand cranked Model-T's I am aware of do have clutch on the crank. But
it will only disengage the crank when the engine fires forward. If the
driver forgets to retard the timing or the timing is off it is very
possible for it to back fire and the crank will spin backwards. Once
the crank starts spinning backward and the engine slows it clutch will
disengage the crank but not until it has either bruised the back of
you hand (if you did it right) or broken your arm (did it wrong). My
grandfather taught me to always hold the crank with an open hand
(don't put you thumb over it) So that it would throw your hand clear
if this happened. As for the "almost" part above I am sure there were
all kinds of creative inventions to prevent this from happening.
Perhaps your Model T has a non-standard clutch or starting device on
it.

Jacking up the left rear wheel doesn't hurt anything either if its
cold. But that is another topic.

Brian

[Matt Whiting]

Matt Whiting wrote:
> Jose wrote:
>>> The crank has a ratchet and will
>>> free wheel if the engine pops backwards.
>>
>> How would that work? The engine going backwards against the crank
>> imparts the same (direction) force as the crank going forwards against
>> a recalcitrant engine. That would freewheel too, defeating the purpose.
>
> Most hand cranks (I haven't seen a Model T lately, but on old tractors
> and such) had a cam design such that the crank handle would turn the
> crank shaft only in one direction. If the crank shaft tried to drive
> the crank handle (as during a kick-back), it would spit the crank handle
> forward and disengage it.

Oops, part of above is incorrect. The handle will disengage only if the
crank drives if forward as when the engine starts, not backwards!

Matt

[Don Tuite]

On Sat, 19 May 2007 01:13:55 -0400, Jose >
wrote:

>> The crank has a ratchet and will
>> free wheel if the engine pops backwards.
>
>How would that work? The engine going backwards against the crank
>imparts the same (direction) force as the crank going forwards against a
>recalcitrant engine. That would freewheel too, defeating the purpose.
>
A simpler version of the ratchet: The way it worked on my '41
McCormick-Deering tractor (sorry Cubdriver, mine had rubber tires),
the crank and the socket were machined with matching flats and
matching ramps. When you were applying torque to start the engine,
the flats were in contact, but when the engine started, the slanty
bits slid past each other and expelled the crank.

But if that sucker tried to run backward, the flats would continue to
engage and the crank handle would do something nasty. Not that it ever
tried that on me.

Jose's right.

Don

[Jose]

> If the crank shaft tried to drive the crank handle (as during a kick-back), it would spit the crank handle forward and disengage it.
>
> It is like the screw heads you see on some bathroom stalls where the slot in the screw head has ramps behind it on opposite sides such that you can tighten with a normal screw driver, but you can't easily remove it with a normal screw driver.

That doesn't make sense. Using the screw head, if the screw lurched
-forward- (in the direction you are trying to turn it) that would push
the screwdriver out. But if the screw turned backwards, that would push
against the screwdriver and kick =you= back.

Maybe there's an intermediate system?

Jose
--
There are two kinds of people in the world. Those that just want to
know what button to push, and those that want to know what happens when
they push the button.
for Email, make the obvious change in the address.

[C J Campbell[_1_]]

On 2007-05-18 13:57:02 -0700, "Capt. Geoffrey Thorpe" <The Sea Hawk at
wow way d0t com> said:

>
> So, we are arguing over the definition of the word "run"?

I s'pose. Well, it has been an interesting thread. I suppose it will
run on for awhile now, until someone calls someone else a Nazi. :-)

>
> Now, if you brought your car in to where I work because it would just fire a
> couple cylinders and quit and I tried to tell you that it was "running"
> wouild you buy that? :-)
>
> But, yea, one cylinders worth of "running" would be all it would take to
> split one's skull.


--
Waddling Eagle
World Famous Flight Instructor

[Cubdriver]

On Sat, 19 May 2007 14:00:18 -0700, C J Campbell
> wrote:

>I s'pose. Well, it has been an interesting thread. I suppose it will
>run on for awhile now, until someone calls someone else a Nazi. :-)

Call yourself lucky. Over on rec.music.opera, they insult one
another's body parts.

Blue skies! -- Dan Ford