Proping Question

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

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.

"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.

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

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

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

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.

"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.

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

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.