----- Original Message -----
Sent: Monday, December 18, 2006
9:01 AM
Subject: Casting mechanics /
Christmas poem (Capt. Jake Jordan)
Walter & Group.........
From Troy Miller (Some of you have seen this from ol Al's messages to
his Group). I suggest you print this one out for study and future
reference :-
There are
basically two types of acceleration that we need to concern ourselves
with -- linear and angular.
Linear
acceleration is a change in speed (velocity) in a straight line.
So when we talk about translational movement, we’re talking about
how the hand moves along in a straight line in the early phase of the
cast, without significantly changing the angle of the rod butt. If
the rod didn’t deflect (load) and you didn’t rotate at all, then the tip
speed would be exactly the same as your hand speed. Of course,
neither of these is absolutely true. We do load the rod, and there
will be some negative rotation at the outset of the casting stroke and
some positive rotation toward the end of the translational phase.
In fact, we’re in continuous transition throughout the casting
stroke. That’s what makes it all smooth and graceful. Any
surprises to the rod or line, and both will tell you about
it…
Angular
acceleration is a change in rotational speed with time. For
instance, if an engine’s crankshaft was spinning at 600 rpm and you
gradually increase the fuel delivery, the rpms will increase in response
to the additional energy created. Say you smoothly press down on
the throttle and the rpms go up to 700, then 800, then 900 rpm.
This would be considered angular acceleration. Of course, in
flycasting, we don’t even go one full revolution. We only go
something less than 180 degrees on even our most “open” casting
strokes.
So, if we want
to think about units, see how this fits:
LINEAR
MEASUREMENTS/MOVEMENTS
Distance =
physical displacement between two points along a straight line between
them (examples – inches, feet, miles)
Speed (aka,
Velocity) = rate of change of position along that straight line
(examples – feet/sec, MPH)
Acceleration =
rate of change of speed
(if the speed is changing). (examples – feet/sec/sec,
MPH/sec)
ANGULAR
MEASUREMENTS/MOVEMENTS
Angle = in 2-D
(planar geometry), a measurement between two vectors (lines), typically
measured at their intersection (degrees, radians)
Angular
velocity = rate of change in angle with time (examples –
deg/sec, RPM)
Angular
acceleration = rate of change in angular velocity with time
(examples -- deg/sec/sec, RPM/sec)
Don’t get
confused about vectors. “Scalar” means how much. “ Vector”
means how much, and in what direction. So we could say that if I’m
driving to Mountain Home to catch the next world record brown, that my
average velocity (or speed) might be 62.3 MPH. But if we wanted to
be more specific, then we could assign a compass heading to it and say
that I was going 62.3 MPH at a bearing of 19.343 degrees from magnetic
north. Therefore, if someone knew where I started and when, they
could take a map and figure out where I would be after any given time
interval. And when I could be expected to arrive, if I specified a
final destination. I’m taking the liberty of neglecting the
curvature of the earth, of course…
Assuredly,
we’ve known HOW to cast for a very long time. We’re just now
getting to the point of describing it in accurate physical terms, I
think. That’s how my book starts…
Let me know if
anything needs further explanation. I’m just on break here in the
shop…
Regards
--
TAM
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Troy...
Well
worded and understandable.
One thing I'd
emphasize is that there is a period during the casting stroke where
there is a blend of linear and angular acceleration (velocity/time) as
the translational phase melds into a principally rotational phase.
With some casters, and some casts, this blend exists throughout the
entire stroke. Overlapping this is the so-called, "loading move"
most of which takes place as the rotational phase begins followed by
the, "speed-up-and-stop" ("power-snap") which takes place largely during
the latter part of the rotational phase. One set of terms does not
negate the other well publicized ones. It all fits together,
nicely.
This
information represents another kind of, "blend". The language of
the lay fly caster with that of the engineer. Kind of reminds us
of Mel Kriegers teachings as he talks about the lexicon of the, "poet"
and that of the, "engineer".
No matter what
we call it, or, "how you cut it", all this must include SMOOTH
CONSTANT ACCELERATION to a point of rapid deceleration
("stop").
Some
say, "well that's what we've been teaching for years"...."It's an answer
we'd expect on an MCI exam"....etc. What's new, then ?
As I
see it, what is new to many of us, is how we look at, "smooth constant
acceleration". Many of us took that to mean constantly
increasing acceleration with no irregularities. Now the new
studies tell us that it means steady or unchanging acceleration. A
big difference.
Quantifying
this as the blend of linear and angular acceleration progresses would
probably require a daunting challange to our physicists and
mathematicians as they try to torture enough calculus to come up
with an explanatory equation. That equation, I think, would
necessarily have many variables to fit the many casts and casting styles
encountered. Without going that route, however, Bruce Richards and
Noel Perkins have demonstrated this concept well with the acceleration
graphs produced by their depiction of angular change at the rod butt
using the Casting Analyzer.
Gordy
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A chrismas poem sent by Capt. Jake Jordon
(One of our most valued Group contributors and FFF supporters over the
years)
'TWAS
THE NIGHT BEFORE CHRISTMAS,
HE
LIVED ALL ALONE,
IN
A ONE BEDROOM HOUSE MADE OF
PLASTER
AND STONE.
I
HAD COME DOWN THE CHIMNEY
WITH
PRESENTS TO GIVE,
AND
TO SEE JUST WHO
IN
THIS HOME DID LIVE.
I
LOOKED ALL ABOUT,
A
STRANGE SIGHT I DID SEE,
NO
TINSEL, NO PRESENTS,
NOT
EVEN A TREE.
NO
STOCKING BY MANTLE,
JUST
BOOTS FILLED WITH SAND,
ON
THE WALL HUNG PICTURES
OF
FAR DISTANT LANDS.
WITH
MEDALS AND BADGES,
AWARDS
OF ALL KINDS,
A
SOBER THOUGHT
CAME
THROUGH MY MIND.
FOR
THIS HOUSE WAS DIFFERENT,
IT
WAS DARK AND DREARY,
I
FOUND THE HOME OF A SOLDIER,
ONCE
I COULD SEE CLEARLY.
THE
SOLDIER LAY SLEEPING,
SILENT,
ALONE,
CURLED
UP ON THE FLOOR
IN
THIS ONE BEDROOM HOME.
THE
FACE WAS SO GENTLE,
THE
ROOM IN SUCH DISORDER,
NOT
HOW I PICTURED
A
UNITED STATES SOLDIER.
WAS
THIS THE HERO
OF
WHOM I'D JUST READ?
CURLED
UP ON A PONCHO,
THE
FLOOR FOR A BED?
I
REALIZED THE FAMILIES
THAT
I SAW THIS NIGHT,
OWED
THEIR LIVES TO THESE SOLDIERS
WHO
WERE WILLING TO FIGHT.
SOON
ROUND THE WORLD,
THE
CHILDREN WOULD PLAY,
AND
GROWNUPS WOULD CELEBRATE
A
BRIGHT CHRISTMAS DAY.
THEY
ALL ENJOYED FREEDOM
EACH
MONTH OF THE YEAR,
BECAUSE
OF THE SOLDIERS,
LIKE
THE ONE LYING HERE.
I
COULDN'T HELP WONDER
HOW
MANY LAY ALONE,
ON
A COLD CHRISTMAS EVE
IN
A LAND FAR FROM HOME.
THE
VERY THOUGHT
BROUGHT
A TEAR TO MY EYE,
I
DROPPED TO MY KNEES
AND
STARTED TO CRY.
THE
SOLDIER AWAKENED
AND
I HEARD A ROUGH VOICE,
"SANTA
DON'T CRY,
THIS
LIFE IS MY CHOICE;
I
FIGHT FOR FREEDOM,
I
DON'T ASK FOR MORE,
MY
LIFE IS MY GOD,
MY
COUNTRY, MY CORPS."
THE
SOLDIER ROLLED OVER
AND
DRIFTED TO SLEEP,
I
COULDN'T CONTROL IT,
I
CONTINUED TO WEEP.
I
KEPT WATCH FOR HOURS,
SO
SILENT AND STILL
AND
WE BOTH SHIVERED
FROM
THE COLD NIGHT'S CHILL.
I
DIDN'T WANT TO LEAVE
ON
THAT COLD, DARK, NIGHT,
THIS
GUARDIAN OF HONOR
SO
WILLING TO FIGHT.
THEN
THE SOLDIER ROLLED OVER,
WITH
A VOICE SOFT AND PURE,
WHISPERED,
"CARRY ON SANTA,
IT'S
CHRISTMAS DAY, ALL IS SECURE."
ONE
LOOK AT MY WATCH,
AND
I KNEW HE WAS RIGHT.
"MERRY
CHRISTMAS MY FRIEND,
AND
TO ALL A GOOD NIGHT."
This
poem was written by a Marine. The following is his request. I think it
is reasonable.....
PLEASE.
Would you do me the kind favor of sending this to as many people as
you can? Christmas will be coming soon and some credit is due to our
US service men and women for our being able to celebrate these
festivities. Let's try in this small way to pay a tiny bit of what we
owe. Make people stop and think of our heroes, living and dead,who
sacrificed themselves for us. Please, do your small part to plant this
small seed.