Proping Question

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

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.

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

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...ation/200705/1

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

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

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

"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