----- 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.